Renewable Energy Technologies Student Book NQF Level 4

GREEN SKILLS FOR JOBS

Student Book Renewable Energy Technologies NQF Level 4 Introduction to Renewable Energy and Energy Efﬁ ciency Textbook provided free of charge by the Skills for Green Jobs Programme ! For classroom use only! Not for resale or redistribution without further permission!

Editor

Skills for Green Jobs (S4GJ) Programme Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH Registered offices: Bonn and Eschborn GIZ Office Pretoria P.O. Box 13732, Hatfield 0028 Hatfield Gardens, Block C, 1st Floor, 333 Grosvenor Street Pretoria, South Africa Tel.: +27 (0) 12 423 5900 E-mail: [email protected] www.giz.de

1st Edition

Responsible: Edda Grunwald Authors: S4GJ Team

Illustrations, Layout: WARENFORM Photos: Dörthe Boxberg, Ralf Bäcker, version-foto

Pretoria, September 2017 CONTENTS

List of Figures and Tables 3 Glossary 12 Preface 26 Foreword 27 Using this Student Book 28

Topic 1 1. Introduction to Renewable Energy Resources and Energy Efﬁ ciency 29

1.1 Economic and Environmental Beneﬁts of Wind Power Systems 30 1.1.1 Wind Power Applications: A Short History 31 1.1.2 Wind Energy Markets in South Africa and the World 41 1.1.3 Advantages and Disadvantages of Wind Power Generation 50

1.2 Economic and Environmental Beneﬁts of Hydrogen Fuel Cell Technology and E-Mobility 61 1.2.1 Hydrogen and Fuel Cell Technologies 62 1.2.2 E-Mobility 75

Topic 2 2. Basic Scientiﬁ c Principles and Concepts 85

2.1 Basic Principles of Wind Power Generation 86 2.1.1 What Causes Wind? 87 2.1.2 Wind Power Factors 94 2.1.3 Essential Wind Turbine Components and their Functions 107 2.1.4 Wind Turbine Types 132

2.2 Basic Principles of Battery and Fuel Cell Technologies 146 2.2.1 Electrochemical Processes in Batteries 147 2.2.2 Electrochemical Processes in Fuel Cells 169

2.3 Basic Principles of E-Mobility 188 2.3.1 Eco-Car Types Compared 189 2.3.2 Essential E-Car Components and their Functions 203 Topic 3 3. Occupational Health and Safety 219

3.1 Hazards and Safe Work Practices Related to Wind Turbine Technologies 220 3.1.1 Hazards Related to Wind Turbine Technologies 221 3.1.2 Safe Work Practices Related to Wind Turbine Technologies 225

3.2 Hazards And Safe Work Practices Related To Fuel Cell Technologies 231 3.2.1 Hazards Related To Fuel Cell Technologies 232 3.2.2 Safe Work Practices Related To Fuel Cell Technologies 237

3.3 Hazards And Safe Work Practices Related To E-Mobility Technologies 242 3.3.1 Hazards Related To E-Mobility Technologies 243 3.3.2 Safe Work Practices Related To E-Mobility Technologies 247

Topic 4 4 Application of Wind Turbine and Fuel Cell Systems and Batteries 253

4.1 Connect Wind Turbine Components using Didactical Training Kits or Small-Scale Industrial Components 254 4.1.1 Experiments with Wind Turbine Training Sets 255 4.1.2 Build your own wind turbine (DIY) 287

4.2 Connect Fuel Cell System Components using Didactical Training Kits 301 4.2.1 Experiments with Fuel Cell Training Sets 302

4.3 Conﬁguring Batteries for Renewable Energy Systems 320 4.3.1 Experiments with Batteries 321

2 LIST OF FIGURES AND TABLES Figures

Topic 1 Theme 1.1.1 Figure 1: Simpliﬁed drawing (side and top view) of an early vertical-axis windmill 32 Figure 2: A post mill 33 Figure 3: A smock mill 34 Figure 4: A technical drawing illustrating the mechanism for a self-regulating windmill 35 Figure 5: Windpumps at the Loeriesfontein Museum, South Africa 36 Figure 6: A simpliﬁed schematic view into a wind turbine 37 Figure 7: A 7 MW offshore wind turbine 38

Theme 1.1.2 Figure 1: Global cumulative installed wind power capacity (2000 – 2015) 42 Figure 2: Top 10 countries with the highest cumulative installed wind power capacity (2015) 43 Figure 3: Large-scale high resolution wind resource map 44 Figure 4: Wind energy projects in South Africa 45

Theme 1.1.3 Figure 1: A possible transition to renewable/clean energy generation over time 51 Figure 2: Comparison of life cycle greenhouse gas emissions for renewable and conventional generation technologies 52 Figure 3: Comparison of life cycle stages and GHG emissions for wind and coal power 53 Figure 4: A typical EIA process for a wind power project (simpliﬁed) 56 Figure 5: Main components of a 5 MW wind turbine and their overall share of turbine costs 58

Theme 1.2.1 Figure 1: Comparison of electrolysis and reverse electrolysis of water (schematic) 63 Figure 2: Fuel cell applications in cutting-edge technologies (schematic) 64 Figure 3: Fuel cell operation (schematic and simplified conceptional) 65 Figure 4: Fuel cell in a lab converting chemical energy into electrical energy 65 Figure 5: Hydrogen as alternative fuel powers fuel cell electric cars such as the Toyota Mirai 66 Figure 6: Overview of hydrogen production pathways (simplified) 67 Figure 7: Overview of sustainable hydrogen production pathways (simplified) 68 Figure 8: Illustration of non-sustainable and sustainable hydrogen production techniques 68 Figure 9: Hydrogen is an ‘energy vector’ or ‘energy carrier’ 69

3 Theme 1.2.2 Figure 1: Component configurations in the three different EV-types 76 Figure 2: uYilo’s DC fast charging facility 76 Figure 3: Tesla’s Supercharger charging profile based on 90 kWh models 77 Figure 4: A typical e-bike with rear hub configurations 78 Figure 5: Ratios of electric motor assistance in a pedelec following EU regulations 79 Figure 6: Different electric motor configurations of e-bikes 79 Figure 7: PV shade canopies with integrated public seating and e-bike charging docks 80 Figure 8: Schematic drawing of the first ZEM inland passenger ship FCS Alsterwasser 81

Topic 2 Theme 2.1.1 Figure 1: A rotor spinning fast in strong wind 88 Figure 2: Directions of sea and land breezes along the coast 89 Figure 3: Two different pressure gradient scenarios and their relative effect on wind speed 89 Figure 4: Sixteen principal bearings of wind direction 90

Theme 2.1.2 Figure 1: Mass of air fl owing through swept rotor area (schematic) 96 Figure 2: Volume (V) of the wind ‘cylinder’ can be redefi ned as the swept rotor area (A) multiplied by the length (s) of the wind ‘cylinder’. 96 Figure 3: Relationship between wind speed and wind power 97 Figure 4: Wind speeds and power increase with height 98 Figure 5: The rotor’s swept area 98 Figure 6: Power output increases as the swept rotor area increases 99 Figure 7: Energy transformations relevant to a wind turbine 100 Figure 8: Lift and drag 101 Figure 9: The Betz limit 102 Figure 10: Mechanical and electrical effi ciency 102

Figure 11: Power coefﬁ cient (Cp) and Poutput vs wind speed 104

Figure 12: Pinput and Poutput vs wind speed 104

Theme 2.1.3 Figure 1: HAWT subsystems (schematic) 108 Figure 2: A single loop conductor placed in a magnetic fi eld (schematic) 109 Figure 3: The conductor rotates in a magnetic fi eld into its horizontal position 110 Figure 4: Flux lines - the pictorial representation of a magnetic fi eld 110 Figure 5: Flemming’s right hand rule 111 Figure 6: Rotating towards its vertical position the conductor is not inducing a current (schematic) 111 4 Figure 7: The conductor rotates into its horizontal position inducing a current in the loop (schematic) 112 Figure 8: The conducting loop is connected to two split rings and two carbon brushes which rest on the slip ring segments 112 Figure 9: Current fl ow under load resistance (schematic) 113 Figure 10: Unidirectional DC current 113 Figure 11: DC machines have many loops of wire wound together to form a coil 114 Figure 12: Types of DC machines (simplifi ed) 114 Figure 13: Schematic diagram of a separately excited DC machine 115 Figure 14: Schematic diagrams of series-wound, shunt-wound and compound-wound generators 115 Figure 15: Schematic diagram of a permanent magnet DC generator 116 Figure 16: Stator assembly for a twin axial fl ux permanent magnet (AFPM) wind turbine 117 Figure 17: Schematic diagram of a synchronous generator and its AC waveform 118 Figure 18: Asynchronous generator diagram and squirrel-cage structure (simplifi ed) 119 Figure 19: Pitch control (simplifi ed) 122 Figure 20: Various blade angles due to pitch control ensuring maximum rated power 122 Figure 21: Pitch control mechanism for a 1 kW wind turbine 123 Figure 22: A typical confi guration for a category A1 installation (schematic and simplifi ed) 124 Figure 23: Switchgear and transformer layout in a typical wind farm confi guration (schematic) 126 Figure 24: Underground cable construction 126 Figure 25: Wind farm power collection system (schematic layout) 127

Theme 2.1.4 Figure 1: Position of principal wind turbine components in HAWTs and VAWTs 133 Figure 2: Principal design comparison of Savonius and Darrieus rotors 134 Figure 3: Comparison of Savonius and Darrieus rotor working principals (schematic) 134 Figure 4: Proposed setups for combined Savonius-Darrieus rotors (schematic) 135 Figure 5: Components of the IKS Windtrainer Junior set in their storage position 137 Figure 6: IKS Windtrainer Junior set: some assembled components 137 Figure 7: Components of the leXsolar-Wind training set in their storage position 138 Figure 8: Two different anemometer types 138 Figure 9: Two different wind machine types 142 Figure 10: Setup for experiment 2 (schematic) 143

Theme 2.2.1 Figure 1: The three basic components of a battery 148 Figure 2: Simpliﬁ ed structure of an atom 149 Figure 3: Sodium cations (Na+) and chloride anions (Cl–) 150 Figure 4: Table salt (NaCl) dissolves in water 151 Figure 5: An enlarged image of Figure 4 c 152 5 Figure 6: The Volta pile (schematic) 153 Figure 7: Simpliﬁ ed electrochemical processes in a voltaic pile / galvanic cell 154 Figure 8: The zinc-carbon dry cell (schematic) 155 Figure 9: Alkaline bottom cell (schematic) 156 Figure 10 – 16: Lead-acid battery discharging via conduction between terminals 157 Figure 11 157 Figure 12 158 Figure 13 158 Figure 14 159 Figure 15 159 Figure 16 160 Figure 17: Lead-acid battery charging by reversing the electrochemical process 160 Figure 18: Lead-acid battery charging by reversing the electrochemical process 161 Figure 19: Schematic setup for Experiment 2 164 Figure 20: Schematic setup of Daniell cells in series creating a battery 167

Theme 2.2.2 Figure 1: Two half-reactions occur at the anode and cathode assembly of a fuel cell 170 Figure 2: The basic components of a polymer electrolyte fuel cell (PEFC schematic view) 171 Figure 3: Catalyst reaction sites (Pt) at porous carbon electrodes 172 Figure 4: A proton exchange membrane (PEM) 172 Figure 5: Components and operation of a PEMFC (schematic) 173 Figure 6: A PEMFC stack composed of a series of single cells separated by bipolar plates 174 Figure 7: Electrolysis: An electric current splits water to produce hydrogen and oxygen 175 Figure 8: Electrolysis: Gas quantity ratios and redox reaction 176

Figure 9: IKS H2 Trainer Junior Set 177 Figure 10: Setup for Experiment 1 178 Figure 11: Setup of Experiment 1 (schematic) 181 Figure 12: Setup for Experiment 2 183 Figure 13: Setup of Experiment 2 (schematic) 184 Figure 14: Two types of graphs illustrating simple linear regressions 185 Figure 15: Regression lines / gas quantities vs current 186

Theme 2.3.1 Figure 1: Greenhouse gas emissions of different sectors in the EU 190 Figure 2: Greenhouse gas emissions from transport in the EU 191 Figure 3: Global markets of electric vehicles (BEVs and PHEVs) 191 Figure 4: FCEV operating principle simpliﬁ ed (schematic) 192 Figure 5: Different degrees of vehicle electriﬁ cation 193

6 Figure 6: Simplifi ed HEV design concept (FWD schematic) 193 Figure 7: Simplifi ed PHEV design concept (FWD schematic) 194 Figure 8: Simplifi ed BEV design concept (FWD schematic) 195 Figure 9: Simplifi ed FCEV design concept (FWD schematic) 196 Figure 10: Shares of EV sales in European markets (2016) 197

Theme 2.3.2 Figure 1: Power train, i.e. engine and drivetrain of a conventional ICE car (FWD) 204 Figure 2: Powertrain of a modern BEV 204 Figure 3: Three-phase AC synchronous pancake motor for a modern BEV 205 Figure 4: In-wheel electric motor for a modern BEV 206 Figure 5: Acceleration and magnetic braking simplifi ed 208 Figure 6: Single-pedal speed control mechanism 209 Figure 7: Estimations for battery cost reductions and performance improvements 210 Figure 8: Growth projection for lithium batteries (Production capacities in GWh) 211 Figure 9: Cutaway of an EV showing the fl oor position of the battery unit 211 Figure 10: Two different charging cables (400 V left and 230 V right) 212 Figure 11: Six different connector types (from left to right: US, EU, China and Japan) 213 Figure 12: Standard VDE three-phase connector for charging BEVs 213 Figure 13: FCEV components simplifi ed (schematic) 214 Figure 14: Hydrogen fuelling control system for FCEVs (simplifi ed) 215

Topic 3 Theme 3.1.1 Figure 1: PPE required for working with renewable energy technologies 222

Theme 3.1.2 Figure 1: Fuses and surge protection for a small-scale wind turbine installation (off-grid) 226 Figure 2: Lockout/tagout procedures 227

Theme 3.2.1 Figure 1: Basic structure of a hydrogen safety system 233 Figure 2: A fuel cell powered bus manufactured by Toyota (Japan) 234 Figure 3: Hydrogen tanks on the Honda FCX Clarity platform 235

Theme 3.2.2 Figure 1: The Hindenburg zeppelin disaster in 1937 239 Figure 2: A modern hydrogen-powered aircraft 239 Figure 3: A modern hydrogen-powered SUV 240

7 Theme 3.3.1 Figure 1: EV warning decals 244 Figure 2: High ‘voltage’ components of a typical BEV (schematic) 245

Theme 3.3.2 Figure 1: Lithium-ion battery pack of an EV 248

Topic 4 Theme 4.1.1 Figure 1: The IKS Windtrainer Junior set (left) and the leXsolar-Wind training set (right) 256 Figure 2: Each training kit uses different components 256 Figure 3: Inserting the rotor blades (IKS Windtrainer Junior) 257 Figure 4: Wind turbine and rotor blade sets (leXsolar) 258 Figure 5: Schematic setup of Activity 1 using IKS Windtrainer Junior 258 Figure 6: Schematic setup of Activity 1 using the leXsolar-Wind training set 259 Figure 7: Carefully tighten the rotor blade locking bolts 259 Figure 8: Hypothetical progression of the output curve in the leXsolar chart 261 Figure 9: Hypothetical progression of the output curve in the IKS chart 261 Figure 10: Different HAWT types 262 Figure 11: The IKS Windtrainer Junior setup for Activity 2, 3 and 4 263 Figure 12: Schematic setup of Activity 2, 3 and 4 using IKS Windtrainer Junior 264 Figure 13: Schematic setup of Activity 2, 3 and 4 using the leXsolar-Wind training set 264 Figure 14: Enter the measured values into the tables provided 265 Figure 15: Hypothetical progression of curves in different charts 267 Figure 16: Curved rotor blades (concave / convex) from IKS’s Windtrainer Junior set 268 Figure 17: Air foil cross-section and aerodynamic forces 269 Figure 18: Enter the measured values into the tables provided and answer all questions 270 Figure 19: Hypothetical curve progression (power vs wind speed) 271 Figure 20: Angle of attack, angle of incidence or pitch angle 273 Figure 21: Relationship between lift, drag and angle of attackc (pitch) 274 Figure 22: Pitch control adjustments along the cord line of rotor blades 274 Figure 23: Hypothetical progression of curves in different chart types 276 Figure 24: Relationship between ‘voltage’ (V) and current (I) in a circuit 278 Figure 25: Schematic setup of Activity 5 using the leXsolar Wind training set 280 Figure 26: Hypothetical progression of I/V lines and output curves in different chart types 282 Figure 27: Schematic setup of Activity 6 using IKS Windtrainer Junior 284 Figure 28: Detailed view for Activity 6 connections using IKS’s capacitator module 285 Figure 29: Schematic setup of Activity 5 with the leXsolar Wind training set 285

8 Theme 4.1.2 Figure 1: DIY – building a HAWT and/or a VAWT (Savonius model) 287 Figure 2: Some of the tools you will need for this activity 288 Figure 3: The materials you need 289 Figure 4: The two VAWT designs once assembled 289 Figure 5: Pattern on the baseplate 290 Figure 6: Improved stator coil design 291 Figure 7: Clockwise connection of eight coils 292 Figure 8: Rotor and stator option for VAWT Design #1 292 Figure 9: Rotor and stator option for VAWT Design #2 293 Figure 10: Circular pattern on cardboard for rotor disk 294 Figure 11: Magnets need to be placed in an alternating polarity arrangement 295 Figure 12: Circular pattern on cardboard for top and bottom cover of turbine blades 296 Figure 13: Assembled VAWT Design #1 297 Figure 14: Assembled VAWT Design #2 297 Figure 15: Circuit diagram of a full-wave bridge rectifi er and smoothing capacitor 298 Figure 16: Simple stator plate based on 3 coil design with a six diode rectifi er unit 299 Figure 17: Connecting/soldering the coils to a rectifi er unit 299

Theme 4.2.1

Figure 1: Electrolysis reaction: 2 H2O (l)  2 H2 (g) + O2 (g) 304 Figure 2: Setup for Activity 1 305 Figure 3: Setup for Activity 1 306 Figure 4: Electrolyser I/V chart based on hypothetical results obtained from Table 3 308 Figure 5: Setup for Activity 3 309 Figure 6: Setup for Activity 3 310 Figure 7: Combined I/V and P/I chart based on hypothetical results obtained from Table 4 311 Figure 8: RET Level 2 training set: 2, 3 or 4 PV cells connected in series 313 Figure 9: The electrolyser powered by 2, 3 or 4 PV cells connected in series 313 Figure 10: Hypothetical electrolyser and PV cell I-V characteristics 314

Figure 11: Setup for Voc and Isc measurements of the turbine generator 316 Figure 12: Turbine generator connected to power the electrolyser 317 Figure 13: Hypothetical I-V electrolyser and PV cell I-V characteristics 318

Theme 4.3.1 Figure 1: Required tools and components 321 Figure 2: Pay attention to polarity when connecting batteries 322 Figure 3: Four SLAs connected in series 323 Figure 4: Four SLAs connected in series and parallel 323 Figure 5: Draw your circuit diagram next to the illustration 324 Figure 6: Draw your circuit diagram next to the illustration 325 Figure 7: Draw your circuit diagram next to the illustration 326

9 Figure 8: Draw your circuit diagram next to the illustration 327 Figure 9: Overcurrent protection for four individual batteries connected in series 328 Figure 10: Overcurrent protection for four individual batteries connected in series 329

Tables

Topic 1 Theme 1.1.2 Table 1: Wind energy projects in South Africa 46

Theme 1.1.3 Table 1: Potential impacts associated with wind power and wind farm development 54 Table 2: Cost structure of a typical medium-sized (2 MW) wind turbine 57

Theme 1.2.1 Table 1: Number of existing public hydrogen refuelling stations and 2020 targets 70 Table 2: Existing FCEV ﬂeet and 2020 targets 70

Topic 2 Theme 2.1.1 Table 1: Beaufort wind speed scale in km/h 91

Theme 2.1.3 Table 1: Main control techniques used in wind turbines 120 Table 2: Turbine design concepts based on generator conﬁ guration and pitch control 121

Theme 2.1.4 Table 1: Criteria for wind turbine categorisation 133 Table 2: Symbols for experimental setup by the leXsolar-Wind training set 139

Theme 2.2.1 Table 1: Standard electrode reduction potentials (E° V) of selected metals 166

Theme 2.2.2 Table 1: Standard electrode reduction potentials (E° V) of hydrogen and oxygen 170 Table 2: Symbols used for devices in the experimental setups 179 Table 3: Gas volumes 182 Table 4: Gas volumes 185

10 Theme 2.3.2 Table 1: Examples of feedback signals sent from EV components to the controller system 206

Topic 4 Theme 4.1.2 Table 1: Material required for Step 1 290 Table 2: Material required for Step 2 291 Table 3: Material required for Step 3 293 Table 4: Material required for Step 4 294 Table 5: Material required for Step 5 295 Table 6: Material required for Step 6 296 Table 7: Material required for Step 7 298 Table 8: Troubleshooting 300

Theme 4.2.1 Table 1: Hypothetical results (blue fonts) of Activity 1 305 Table 2: Calculating energy efﬁ ciency factor using hypothetical results 305 Table 3: Hypothetical results (blue fonts) of Activity 2 307 η Table 4: Hypothetical results (blue fonts) of Activity 3 310 Table 5: Hypothetical results (blue fonts) of Activity 4 314

Table 6: Hypothetical results (blue fonts): measuring Voc and Isc of the turbine generator 317

Table 7: Hypothetical results (blue fonts): measuring wind speed (vwind),

Voc and Isc of the turbine at electrolyser current (I = 0 mA) 317

Theme 4.3.1 Table 1: Document your measurements (V and I) in the table below: 324 Table 2: Document your measurements (V and I) in the table below: 325 Table 3: Document your measurements (V and I) in the table below: 326 Table 4: Document your measurements (V and I) in the table below: 327

11 GLOSSARY

Accumulator A rechargeable battery or cell (see also ‘secondary battery’).

Air foil The cross section proﬁle of a rotor blade, designed to provide low drag and good lift. Also found on an airplane wing.

Alkaline battery The most common are AAA, AA, A, C and D dry cell batteries. The cathode is composed of a manganese dioxide mixture, while the anode is a zinc powder. It gets its name from the potassium hydroxide electrolyte, which is an alkaline substance. GLOSSARY Alternating Current Charge can vary with time in several ways, resulting in different types (AC) of current. An electric charge ﬂowing back and forth at a set frequency will, for example, result in a time-varying current called alternating current (AC). AC is a current that varies sinusoidally over time, for example 100 times per second at a frequency of 50 hertz. AC is provided by most power stations and is transmitted through the national grid to residential and commercial power users.

Ambient Factors found in the surrounding area or environment, e.g. ambient temperature.

Anemometer An instrument used to measure the velocity or speed of wind.

Angle of attack The angle between the line of the chord of an aerofoil and the relative airﬂow. The angle of relative air ﬂow to a wind turbine’s blade.

Anion A negatively charged ion which has more electrons than protons. In a fuel cell anions, being positively charged, migrate toward the anode.

Anode One of the two electrodes in a battery or fuel cell, the anode is positively charged. It gives up electrons into the circuit and ions into the electrolyte.

Armature Usually synonymous with rotor plate, the moving part of an electric machine. In many generator and motor designs, the armature carries the magnets and rotates around the axis of the stator, i.e. the disk carrying the coils.

Asynchronous The terms asynchronous and induction are often used interchangeably generator to describe these types of AC machines. Many wind turbines use so-called three phase asynchronous generators to generate alternating current. Most induction machines contain a rotational element, the rotor is dubbed a squirrel cage. The stationary part of the motor windings is called the armature or the stator. The asynchronous nature of induction machine operation comes from the slip, i.e. the difference between the rotational speed of the stator ﬁeld and the somewhat slower speed of the rotor.

Axis The centre line of a rotating object‘s movement.

12 Battery (cell) An electrochemical device used to store energy. The term is usually applied to a group of two or more electric cells connected together. A battery cell consists of a positive electrode, a negative electrode, and other necessary electrochemical and structural components. A battery cell is a self-contained energy conversion device whose function is to deliver electrical energy to an external circuit via an internal chemical process.

Battery An electrochemical device used to store electrical energy. The term is usually applied to a group of two or more electric cells connected electrically.

Battery capacity The electric output of a cell or battery on a service test delivered before the cell reaches a speciﬁed ﬁnal electrical condition. It may be GLOSSARY expressed in ampere-hours, watt-hours, or similar units. The capacity in watt-hours is equal to the capacity in ampere-hours multiplied by the battery ‘voltage’.

Battery charger A device capable of supplying electrical energy to a battery.

Battery charge rate The current expressed in amperes (A) or milliamps (mA) at which a battery is charged.

Battery module A grouping of interconnected battery cells in a single mechanical and electrical unit.

Battery pack/Traction Interconnected battery modules that have been conﬁgured for a battery speciﬁc energy storage application.

Battery system Completely functional energy storage system consisting of the pack(s) and necessary ancillary subsystems for physical support, thermal management, and electronic control.

Beaufort scale A scale of wind forces which describes the wind by name and range of velocity, and classiﬁes it from force 0 to 12. The initial wind force scale of Francis Beaufort (1805) did not reference wind speed numbers but related qualitative wind conditions to effects on the sails of a frigate of the Royal Navy, namely from ‘just sufﬁcient to give steerage’ to ‘that which no canvas sails could withstand’.

Betz coefficient The maximum power coefficient (Cp) of a theoretically perfect wind turbine is equal to 16/27 (59.3%). This coefficient had been mathematically proven by the German physicist Albert Betz in 1919. In reality, this limit cannot be achieved due to drag, electrical losses, and mechanical inefficiencies (see capacity factor).

Bipolar plate A fuel-cell stack component. They are often designed to channel the ﬂow of gases and heat to and from the cell.

Blades Flat long panels connected to the rotor hub providing the aerodynamic active surface. Blades converting linear wind power into a circular motion.

Braking system A device to slow a wind turbine’s shaft speed down to safe levels.

Brushes Conducting devices that transfer a current to or from a rotating object. They are usually made of carbon-graphite.

13 Capacity factor (Cp) A power coefficient and a measure of a wind turbine’s overall efficiency. Cp values indicate the ratio of input power extracted from the wind relative to the output power over a given time period. The Cp thus represents the combined efficiency of the various turbine system components.

Capacity The capacity of a battery is a measure of the amount of energy that it can deliver in a single discharge. Battery capacity is normally listed as amp-hours, milliamp-hours or watt-hours.

Catalyst Any substance that increases the rate of a chemical reaction, but which is not used up by the reaction and can thus be used over and over again. Platinum and Palladium, for example, are used as a catalyst in GLOSSARY many fuel cells.

Cathode One of the two electrodes in a battery or fuel cell. The cathode is negatively charged. Reduction occurs at the cathode, meaning electrons are captured rather than released (anode). It is an electrode that, in effect, oxidises the anode or absorbs the electrons. During discharge, the positive electrode of a voltaic cell is the cathode.

Cation A positive ion, e.g. a proton liberated from hydrogen is called a cation.

Cell Composed of positive and negative plates and an electrolyte, a cell is an electrochemical device which is capable of storing electrical energy. It is the basic ‘building block’ of a battery.

Charge (electric) There are two types of electric charges, positive and negative, commonly carried by protons and electrons respectively. Electric charge is the physical property of matter that causes a force when placed in an electromagnetic ﬁeld.

Charge The conversion of electrical energy, provided in the form of a current, into chemical energy within the cell or battery.

Charging The process of supplying electrical energy for conversion, i.e. converting electrical energy to chemical energy.

Chemical hazards These are present when a worker is exposed to chemical substances be it solids, liquids or gases. Some of these substances can have dangerous health effects and could cause illnesses, skin irritation or breathing problems.

Circuit A closed conducting path through which electric charges can ﬂow.

Combustion Also known as burning of fossil fuels in different types of machines that convert heat energy into mechanical energy. A complex sequence of exo- thermal chemical reactions between a fuel and oxidant (usually oxygen). The reaction is accompanied by the production of heat and/or light.

Commutator The rotating axis part of a DC generator.

Compressed hydrogen Hydrogen in the gaseous state kept under pressure greater than standard atmospheric pressure.

Constant-current A charging process in which the current applied to the battery is charge maintained at a constant value.

14 Cryogenic storage Under high pressure and very low temperatures gases can be stored in high-pressure cylinders in liqueﬁed form. Cryogenic storage of hydrogen or other gases is a common technology, however hazards resulting from the very low storage temperatures, e.g. around -250º C for hydrogen, include severe cold-burns.

Cut-in / cut-out The wind speed at which a wind turbine begins (cut-in) or ceases wind speed (cut-out) to generate power.

Cut-off voltage/final The prescribed lower-limit voltage at which battery discharge is voltage considered complete. The cut-off or final voltage is usually chosen so that the maximum useful capacity of the battery is realised. The cut-off voltage varies with the type of battery used and what the battery is used for. When testing the capacity of a NiMH or NiCD battery a cut-off GLOSSARY voltage of 1.0 V is normally used. 0.9V is normally used as the cut-off voltage of an alkaline cell. A device that is designed with a too high cut-off voltage may stop operating while the battery still has significant capacity remaining.

Cycle life For rechargeable batteries, cycle life refers to the total number of charge/discharge cycles the cell can sustain before its capacity is signiﬁcantly reduced. End of life is usually considered to be reached when the cell or battery delivers only 80% of rated ampere-hour capacity. NiMH batteries typically have a cycle life of 500 cycles. NiCd batteries can have a cycle life of over 1 000 cycles. The cycle of a battery is greatly inﬂuenced by the type of depth of the cycle (deep or shallow) and the method of recharging. Improper charge cycle cut-off can greatly reduce the cycle life of a battery.

Cycle One sequence of charge and discharge.

Darrieus A vertical-axis wind turbine (VAWT) design using lift forces. Initially designed by F.M. Darrieus (1920 – 1930), a French wind turbine developer. A modern variant is the H-Darrieus rotor – its rotor blades are straight and sit on support arms.

DC/DC converter A power converter that produces an output ‘voltage’ greater than or less than the input ‘voltage’.

Deep cycle A cycle in which the discharge is continued until the battery reaches its cut-off voltage, usually 80% of discharge.

Density Mass per unit of volume.

Depth of discharge The amount of energy that has been removed from a battery (or battery pack), usually expressed as a percentage of the total capacity of the battery. For example, 50% depth of discharge (DOD) means that half of the energy in the battery has been used. 80% DOD means that eighty percent of the energy has been discharged, so the battery now holds only 20% of its full charge.

Diffusion The movement of molecules from a region of higher concentration to a region of lower concentration.

Diode A solid-state device that allows current to ﬂow in a circuit in only one direction.

15 Direct current (DC) There can be several different types of current as charge can vary with time in several ways. If the current does not change with time but remains constant, we call it a direct current (DC). Direct current is usually provided by batteries, photovoltaic cells and other DC generators.

Direct drive Referring to a rotor and generator conﬁguration where the two components are connected directly so that one rotor revolution equates to one revolution of the generator.

Discharge The conversion of chemical energy from a battery or fuel cell into electric energy.

GLOSSARY Drag An aerodynamic force that acts parallel and in opposition to the direction of travel for an object moving through a ﬂuid.

Drain Withdrawal of current from a battery or fuel cell.

Dry cell A primary cell in which the electrolyte is absorbed in a porous medium or is otherwise restrained from ﬂowing.

Efﬁciency The ratio of energy output to energy input.

Electrical hazards Workers in the wind power industry are exposed to a variety of potentially serious electrical hazards. Often, these include electrical shock and severe burns from arc ﬂashes. Falls and also crushing injuries have been reported as a result of these injuries.

Electric machines Electric machines are electromechanical energy conversion devices. Motors convert electrical energy into mechanical energy while generators do exactly the opposite, converting mechanical power into electrical power.

Electrode A terminal that carries an electric current. An electrical conductor through which an electric current enters or leaves a conducting medium, whether it be an electrolytic solution, a solid, molten mass, a gas or a vacuum. For electrolytic solutions, many solids and molten masses, an electrode is an electrical conductor at the surface of which a change occurs from conduction by electrons to conduction by ions.

Electrolyser An electrochemical device which works like a fuel cell in reverse, i.e. the device can split water into its constituent molecules, hydrogen and oxygen, by passing an electric current through it.

Electrolysis The breakdown of a chemical through the application of an electric charge to it. This process is commonly used to break up water into hydrogen and oxygen.

Electrolyte A chemical compound which, when fused or dissolved in certain solvents - usually water - will conduct an electric current. All electrolytes in the fused state or in solution give rise to ions which conduct the electric current. In a fuel cell, the electrolyte allows ions to move from one electrode to the other, but is impermeable to electrons.

16 Electromagnetic fields Electromagnetic fields, also known as EM fields, are present everywhere in our environment but are invisible to the human eye. EM fields are produced by electrically charged objects. EM fields affect the behaviour of charged objects in their vicinity. They can be considered as the combination of an electric field and a magnetic field. The electric field is produced by stationary electric charges and the magnetic field by moving electric charges.

Electromotive force The potential difference generated by either an electrochemical cell or (EMF) a changing magnetic ﬁeld. Commonly denoted by the acronym emf or EMF.

Energy monitor A display that indicates the charge/discharge status of the high ‘voltage’ battery. GLOSSARY

Explosion limit Some gas mixtures, e.g. air and hydrogen, will readily ignite and (LEL/UEL) explode within a certain range of concentration. For example, air/ hydrogen mixtures containing as little as 4% hydrogen, which is the lower explosion limit (LEL), up to as much as 75%, the upper explosion limit (UEL), will readily ignite and explode. If a ﬂammable mixture of hydrogen and air is allowed to form, the likelihood of an explosion occurring is very high, because the energy necessary to initiate a hydrogen/air mixture is very small.

Falling hazard Workers who erect and maintain wind turbines work at heights and are thus exposed to falls with potentially dangerous consequences (serious injuries or death).

Flemming‘s right hand This rule says that if you stretch thumb, index finger and middle finger rule of your right hand perpendicular to each other, then the thumb indicates the direction of motion of the conductor field, the middle finger indicates the direction of flow of the current through the conductor and the index finger indicates the direction of the magnetic field.

Float charging Method of recharging in which a secondary cell is continuously connected to a constant-voltage supply that maintains the cell in fully charged condition. The method is typically applied to lead acid batteries.

Fossil fuel Any hydrocarbon fuel produced from organic matter (long dead).

Frequency Cycles per second, measured in Hertz. For example, the number of times an AC circuit reaches both minimum and maximum values in one second.

Fuel cell An electrochemical device which converts chemical energy to electrical energy without combustion. Unlike a battery, a fuel cell will continuously produce electricity as long as fuel is supplied and the catalyst remains active.

Fuel cell electric Fuel cell electric vehicles use fuel cells to generate electric power for vehicles (FCEV) propulsion.

Galvanic cell A combination of electrodes, separated by an electrolyte, capable of producing electrical energy by electrochemical action.

17 Gassing The evolution of gas from one or both of the electrodes in a cell. Gassing is commonly the result of self-discharge or the electrolysis of water in the electrolyte during charging.

Gearbox Usually a mechanical device containing a gearing system for the purpose of transferring forces between machines or mechanisms, often with changes of torque and speed. In wind turbines, gearboxes connect the low-speed shaft to the high-speed shaft, aiming to increase rotational speed to the speed required by the generator.

Generator An electric machine that converts mechanical (rotational) energy into electrical energy.

GLOSSARY High voltage Nominal ‘voltage’ levels equal or greater than 44 kV up to and including 132 kV.

Horizontal-axis wind The most common type of commercial utility scale wind turbine design, turbine (HAWT) where the rotor axis and the shaft is parallel to the ground and the blades are perpendicular to the ground.

Hydride A negatively-charged hydrogen ion. Metal hydrides, e.g. in nickel metal hydride (NiMH) batteries, are metals which have been bonded to hydrogen ions to form a new compound. Most hydrides behave as reducing agents in chemical reactions. Metal hydrides are used in certain fuel cells and as hydrogen storage compounds.

Hydride ion The smallest possible anion. It is made up of two electrons and a proton.

Hydrocarbon An organic compound that consists only of hydrogen and carbon atoms.

Hydrogen economy A scenario where a country uses hydrogen as the primary energy carrier in place of fossil fuels. Hydrogen would be used to provide electrical power, heat homes and power vehicles. Ideally this hydrogen would be generated from renewable energy, resulting in zero emissions.

Hydrogen fuel cell A sub-type of proton exchange membrane fuel cell in which only hydrogen and oxygen are used as fuels. The only byproducts are water, heat, and electricity. These fuel cells are the main focus for use in FCEVs.

Hydrogen The smallest of all elements, consisting of a single proton and a single electron. Hydrogen is used as fuel in most fuel cells and it is the most abundant element in the universe.

ICE Internal Combustion Engine

Induction Electromagnetic induction or just induction is a process where a conductor is placed in a changing magnetic ﬁeld or moves through a stationary magnetic ﬁeld, causing a potential difference across the conductor. This process of electromagnetic induction, in turn, causes an electrical current or in other words, induces a current.

Induction machine An AC type of generator or motor (see asynchronous).

Internal resistance The resistance to the ﬂow of an electric current within the cell or battery.

18 Inverter A device that converts direct current (DC) to alternating current (AC).

Ion An atom that becomes positively or negatively charged through the loss or gain of electrons.

Lead-acid battery This is the chemistry used in a typical car battery, the electrodes are (rechargeable) usually made of lead dioxide and metallic lead, while the electrolyte is a sulfuric acid solution.

Lift An aerodynamic force that acts at right angles to the airstream ﬂowing over an air foil.

Liquid hydrogen Elemental hydrogen in the liquid state. This can only be achieved at very low temperatures: -287° C. Please note, that this is only 20° above GLOSSARY absolute zero!

Lithium-ion battery Lithium chemistry is often used in high-performance devices, such as (rechargeable) cell phones, digital cameras and even electric cars. A variety of substances are used in lithium batteries, but a common combination is to use lithium cobalt oxide for the cathode and carbon for the anode.

Lockout/tagout To prevent the DC and AC circuits from inadvertently re-energising during wind turbine installation or scheduled maintenance work, documented lockout/tagout procedures should be followed both on the DC and AC side of the system.

Low voltage In South Africa low voltage is considered as nominal potential up to and including 1 kV.

Magnet A device that attracts ferromagnetic materials.

Magnetic field Also called magnetic flux. Historically described in terms of its effect on electric charges. An electrically charged particle moving in a magnetic field will experience a force known as the Lorentz force pushing it in a direction perpendicular to the magnetic field and the direction of its motion.

Medium-voltage grid Part of the public distribution grid with a typical nominal potential, i.e. in South Africa a nominal potential greater than 1 kV and less than 44kV.

Megawatt (MW) 1 000 kilowatts (kW) or 1 million watts (W). The standard measure of electric power generating capacity.

Megawatt hour The amount of energy used if work is done at an average rate of 1 (MWh) million watts for 1 hour.

Megawatt peak (MWp) Unit of measurement for the nominal output, e.g. the peak or maximum output of a wind turbine.

Membrane A membrane separates the two electrodes of a fuel cell. It acts as the electrolyte, allowing passage of ions between the electrodes.

Membrane electrode Membrane electrode assembly, a structured component in a PEMFC assembly (MEA) consisting of a membrane with an electrode on each side.

19 Memory effect A phenomenon in which a cell, operated in successive cycles to less than full depth of discharge, temporarily loses the remainder of its capacity at normal voltage levels (usually applies only to NiCd cells). Note, memory effect can be induced in NiCd cells even if the level of discharge is not the same during each cycle. Memory effect is reversible.

Motor/Generator An electromechanical device that can operate in two modes without changing rotational direction. As a motor, it consumes electricity to produce mechanical power. As a generator, it consumes mechanical power to produce electricity.

Nacelle The nacelle sits on top of the tower and contains the gearbox, shafts, GLOSSARY and generator etc. of a wind turbine.

Negative terminal The terminal of a battery from which electrons ﬂow in the external circuit when the cell discharges.

Neodymium-(Iron- The composition of a very powerful permanent magnet. The materials, Boron) magnet so-called rare-earth elements, are mined, processed, and sintered into shape and used in various types of AC and DC machines.

Ohm’s Law The formula that describes the amount of current flowing through a circuit. In a given electrical circuit, the amount of current in amperes (I) is equal to the pressure in volts (V) divided by the resistance, in ohms (R). Ohm‘s Law can be shown by three different formulas: • To find Current I = V/R • To find Voltage V = I x R • To find Resistance R = V/I

Open circuit The condition of a battery which is neither on charge nor on discharge (i.e. disconnected from a circuit).

Open-circuit voltage The difference in potential between the terminals of a cell when the circuit is open (i.e. a no-load condition).

Output Energy or power provided per time unit.

Oxidation A chemical reaction that results in the release of electrons by an electrode’s active material.

Oxygen The eighth chemical element with 8 protons and 8 electrons. One of the primary fuels in all fuel cells. Combines with two hydrogen atoms to create water.

Palladium (Pd) A rare metal often used as a catalyst in fuel cells. Its atomic number is 46.

Parallel connection The arrangement of cells in a battery made by connecting all positive terminals together and all negative terminals together. The ‘voltage’ of the group remains the same as the ‘voltage’ of the individual cell. The capacity is increased in proportion to the number of cells.

Permanent magnet A material that retains its magnetic properties without an external magnetic ﬁeld.

20 Pitch The angle between the edge of the blade and the plane of the blade’s rotation. Blades are turned or pitched in or out of the wind to control rotor speed.

Platinum (Pt) A rare metal often used as a catalyst in fuel cells. Its atomic number is 78. Over 80% of the world’s platinum is mined in South Africa. Platinum is a commonly used catalyst material for PEMFC technologies.

Polarity Refers to the charges residing at the terminals of a battery.

Polymer A compound made by linking small subunits (called monomers) together in a repeating pattern.

Polymer electrolyte Also referred to as proton exchange membrane. A solid polymer GLOSSARY membrane (PEM) membrane used as an electrolyte in certain fuel cells.

Polymer electrolyte A type of acid-based fuel cell that uses the transport of protons from membrane fuel cell the anode to the cathode through a solid polymer electrolyte (PEMFC) membrane. These fuel cells run at temperatures less than 100° C.

Portable fuel cell Any type of fuel cell that can be carried by hand. These are often used for emergency power applications and in high tech applications (space/ aeronautic etc.).

Power ﬂow display An animated graphic indicating the direction of the ﬂow of energy.

Pressure gradient force The primary force inﬂuencing the formation of wind from local to global scales.

Primary cell A cell designed to produce electric current through an electrochemical reaction that is not efﬁciently reversible. The cell, when discharged, cannot be efﬁciently recharged by an electric current. Alkaline, lithium and zinc air are common types of primary cells.

Rated capacity The number of ampere-hours a cell can deliver under speciﬁc conditions (rate of discharge, end voltage, temperature); usually the manufacturer’s rating.

Rechargeable Capable of being recharged; refers to secondary cells or batteries.

Redox Short for reduction-oxidation reaction. A chemical reaction in which atoms undergo a change in the oxidation number, thus usually gaining or losing electrons.

Reduction A chemical process that results in the acceptance of electrons by an electrode’s active material.

Reformate The output of a fuel reformer. Such a gas stream often contains hydrogen, carbon monoxide and carbon dioxide. Reformate gas can be fed to a fuel cell, generally after some degree of clean-up.

Reformer A device that extracts hydrogen from hydrocarbons. Part of indirect fuel cell systems in which the fuel is processed prior to injection into the fuel cell stack.

Rotor hub The centre of a rotor which holds the blades and is attached to the gearbox or generator shaft.

21 Safety checklists Checklists determine compliance with industry speciﬁc standards and to ensure consistency. Many companies use checklists as documentary evidence that they have a system in place to identify and control hazards and risks.

Savonius A drag powered vertical-axis wind turbine (VAWT) initially designed by Mr. Savonius in the 1920s and 30s.

Seal The structural part of a galvanic cell that restricts the escape of solvent or electrolyte from the cell and limits the ingress of air into the cell (the air may dry out the electrolyte or interfere with the chemical reactions).

GLOSSARY Self discharge Discharge that takes place while the battery is in an open-circuit condition.

Separator The permeable membrane that allows the passage of ions, but prevents electrical contact between the anode and the cathode. Separators can be made from a variety of non-conducting materials. Separators do not chemically react with the anode, cathode or electrolyte.

Separator plate Plates used to physically separate individual fuel cells in a stack.

Series connection The arrangement of cells in a battery conﬁgured by connecting the positive terminal of each successive cell to the negative terminal of the next adjacent cell so that their ‘voltages’ are cumulative. See “parallel connection”.

Service life (years or A general term that describes the length of time a battery can remain cycles) in service. Service life can be speciﬁed in terms of either time or duty cycles.

Service plug A high ‘voltage’ electrical disconnect device that is used when performing repairs on the high ‘voltage’ vehicle circuits.

Shaft The rotating part in the centre of a nacelle that transfers rotational motion to a gearbox or a generator.

Shallow cycling Charge and discharge cycles which do not allow the battery to approach its cut-off ‘voltage’. Shallow cycling of NiCd cells leads to ‘memory effect’, whereby the batteries end up temporarily holding less charge. Shallow cycling is not detrimental to NiMH cells and it is beneﬁcial for most lead-acid batteries.

Shelf life For a dry cell, the period of time (measured from date of manufacture), at a storage temperature of 21°C after which the cell retains a speciﬁed percentage (usually 90%) of its original energy content.

Short-circuit A condition that occurs when a short electrical path is unintentionally created. Batteries can supply hundreds of amps if short-circuited, potentially melting the terminals and creating sparks.

Short-circuit current That current delivered when a cell is short-circuited (i.e., the positive and negative terminals are directly connected with a low-resistance conductor).

22 Single cell The smallest and most basic form of a battery or fuel cell consisting of an anode, cathode and electrolyte. While batteries are used commercially as single cells, single fuel cells are only useful for testing and development purposes, e.g. predicting how a stack will perform etc.

Stack (fuel cells) Individual fuel cells connected to create a larger unit consisting of multiple stacked fuel cells. A fuel cell stack is an arrangement of individual fuel cells, usually in

series, to provide a useful output current.

Stall Is similar to pitch control, but instead of pitching the blades out of alignment with the wind, the blades are turned so that they impede further rotor movement. GLOSSARY

Starting-lighting- A battery designed to start internal combustion engines and to power ignition (SLI) battery the electrical systems in automobiles when the engine is not running. SLI batteries can be used in emergency lighting situations.

Stationary battery/ A fuel cell unit that is not movable, often used for electric power fuel cell generation for larger applications such as hospitals.

Stator The stationary part of an electric machine related to the collection of stationary parts in its magnetic circuits. The stator and rotor interact to generate power in a generator or to turn the driveshaft in a motor.

Steam reforming A process of producing hydrogen from hydrocarbons at high temperatures (700° - 1100° C) and in the presence of a metal-based catalyst such as nickel.

Storage battery An assembly of identical cells in which the electrochemical action is reversible so that the battery may be recharged by passing a current through the cells in the opposite direction to that of discharge. While many non-storage batteries have a reversible process, only those that are economically rechargeable are classiﬁed as storage batteries.

Storage cell An electrolytic cell for the generation of electric energy in which the cell after being discharged may be restored to a charged condition by an electric current ﬂowing in a direction opposite the ﬂow of current when the cell discharges. Synonym: secondary cell, also see ‘storage battery’.

Substation A facility usually owned by the national or municipal utility stepping potential difference up or down to suit the electric parameters of long-distance transmission lines.

Swept area Also synonymous with rotor diameter. The area swept by the turbine rotor.

Switch gear The combination of disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energise equipment to allow work to be done and to clear faults downstream.

23 Synchronous machine An electric machine with a special rotor construction that rotates at the same speed, thus synchronising with the stator ﬁeld. There are basically two types of synchronous machines, i.e. self-excited ones using principles similar to those of induction motors, and directly excited ones.

Terminals The parts of a battery to which the external electric circuit is connected.

Tower The base structure that supports and elevates a wind turbine rotor and nacelle.

Transformer Initially an electric device with multiple individual coils of wire wound GLOSSARY on a laminate core. Nowadays, electronic elements are used to transfer power from one circuit to another using magnetic induction, usually to step the potential difference up or down.

Trickle charging A method of recharging in which a secondary cell is either continuously or intermittently connected to a constant-current supply that maintains the cell in fully charged condition.

Turbine A rotary engine that extracts energy from the ﬂow of a ﬂuid such as air (wind), steam or water.

Upwind Synonymous with windward, i.e. the same direction from which the wind is blowing.

Vent A normally sealed mechanism that allows for the controlled escape of gases from within a cell.

Vertical-axis wind A wind turbine whose rotor spins around a vertical axis. turbine (VAWT)

Wind farm Also known as a wind power plant. A group of wind turbines often owned and maintained by one company/utility.

Wind The movement of air masses, i.e. air in motion.

Wind vane Wind vane m easures wind direction and communicates with the yaw drive to orient the turbine into the wind.

Working at height Working at height occurs frequently throughout all phases of construction and operation of wind turbines and is especially relevant when it comes to maintenance. The main focus when managing working at height should be the prevention of a fall.

Yaw drive To rotate the nacelle and the rotor around a vertical axis on a turbine tower, a yaw drive is used. This mechanism ensures that the nacelle and the rotor are constantly facing into the wind.

Zinc-carbon battery The zinc-carbon chemistry is common in many inexpensive AAA, AA, C and D dry cell batteries. The anode is composed of zinc, the cathode of manganese dioxide, and the electrolyte is ammonium chloride or zinc chloride.

24 GLOSSARY

25 PREFACE

On behalf of the German Ministry of Economic Cooperation and Development (BMZ), the Skills for Green Jobs (S4GJ) programme, together with the South African Departments of Higher Education and Training (DHET) and Science and Technology (DST), jointly developed and implemented a number of activities which aim to: 1. Support qualifi ed TVET lecturers in their continuous professional development through training in Renewable Energy and Energy Eﬃ ciency Technologies. 2. Develop and support the implementation of a new optional vocational subject on Renewable Energy Technologies for NC(V) students. 3. Develop appropriate training material, such as student textbooks and lecture guides, for the new subject. PREFACE Subsequently, we are very happy that the student book for NC(V) level 4 Renewable Energy Technologies is now available. Th e new subject and student book is for students of the technical NC(V) programmes who want to learn more about renewable energy technology, its potentials and limitations. Th e student book introduces students to the relevant technical concepts, illustrates examples from real world applications, and others exercises and practical work/experiments.

Yours in renewable energy…

26 FOREWORD BY THE DIRECTOR-GENERAL OF THE DEPARTMENT OF HIGHER EDUCATION AND TRAINING

Th e Department of Higher Education and Training is pleased to introduce the subject Renewable Energy Technologies in the National Certifi cate (Vocational) NC(V) Electrical Infrastructure Construction programme. Th is new subject is the latest addition to the vocational specialisation options off ered in Technical and Vocational Education and Training (TVET) colleges and has been developed for students who want to learn more about renewable energy generation and the technologies related therewith.

Outlined in Accord 4 of South Africa’s new growth path, government commits to the procurement of renewable energy, with the aim to expand and diversify the nation’s energy generation capacity, whilst lowering greenhouse gas emissions, in order to meet the challenges posed by climate change. To fully re- alize these commitments the economy needs informed and trained people in this fi eld, which continues FOREWORD to be a signifi cant driver for future employment. Th e Industrial Development Corporation (IDC) and the South African Development Bank (SADB) estimated in 2011 that the total employment potential in the energy generation and energy and resource eﬃ ciency categories would be 130 000 and 68000 new jobs respectively.

Under the auspices of the German Ministry of Economic Cooperation and Development (BMZ) and supported by the Department of Higher Education and Training (DHET) and the Department of Science and Technology (DST), the Skills for Green Jobs (S4GJ) programme drove the process of developing this new subject, the training material, student textbook and lecturer guide and trained TVET College lecturers on the subject matter content on new didactical training equipment as part of their continuous professional development so that they can teach the subject in a practical and progressive manner.

Th us, in January 2015 the subject Renewable Energy Technologies was successfully implemented on NC(V) Level 2 in six TVET colleges, namely Boland, Ingwe, Northlink, Port Elizabeth, Umfolozi and West Coast TVET Colleges.

Th e development and implementation of this new subject is the result of cordial collaboration and successful cooperation between Germany and South Africa and I wish the colleges, the lecturers and mostly our students a good start with Renewable Energy Technologies in 2015 and beyond.

Mr GF Qonde Director-General: Higher Education and Training

Foreword written by the Director-General for the RET Level 2 student book in 2015.

27 USING THIS STUDENT BOOK

Th is textbook is comprised of 4 topics for NC(V) level 4.

Th e structure of each topic includes various units, for example Unit 1 of Topic 1, International and National Climate Change Policies, and each unit is made up of several themes. In essence, the themes form the core of the student book. Th ey contain keywords, the desired outcomes, technical terms and defi nitions, illustrative examples, as well as questions, exercises and experiments through which the students can independently check their knowledge and understanding. Lastly, each theme ends with a bibliography section which will enable students to supplement the described subject matter.

28 TOPIC THEME 1.1.1

Introduction to Renewable Energy Resources and Energy Efﬁ ciency

Topic Overview

South Africa’s domestic economy largely depends on fossil fuels, particularly for electrical energy generation, manufacturing and transport. Subsequently, the country is one of the largest greenhouse gas (GHG) emitters on the continent and in the world. South Africa, however, is also an example of how quickly energy transition can happen. While the construction of two new coal-fi red power stations, Kusile in Mpumalanga and Medupi in Limpopo, is seriously behind schedule and over-budget by almost double the original price, South Africa’s renewable energy programme (REI4P) in 2016 has over 50 fully operational renewable energy plants and nearly 100 additional plants in development. Wind turbines play an important role in South Africa’s clean energy transition. Thus, in this topic we will introduce you to the socio-economic and environmental benefi ts of wind turbine technologies. South Africa also has a large potential to play a leading role in e-mobility in Africa. Currently, e-mobility is still an insignifi cant niche market, albeit most manufacturers have at least one model on offer. Japan already has more charging stations for e-cars than gasoline stations according to a recent study by Nissan (May 2016), and Norway aims to ban the sale of fossil fuel-based cars by 2025. These are indications that e-mobility is defi nitely coming. These developments will be defi ned by renewable energy generation into smart grids, charging networks, local standardisation, battery and fuel cell technology, electric drive train components and smart connectivity. We will thus also introduce you to the socio-economic and environmental benefi ts of hydrogen fuel cell technology and e-mobility.

Topic 1 covers the following units: Unit 1.1 Economic and Environmental Beneﬁ ts of Wind Power Systems Unit 1.2 Economic and Environmental Beneﬁ ts of Hydrogen Fuel Cell Technology and E-Mobility

29 30 Unit 1.1 Unit 1.1 covers the following three themes: Unit three 1.1 following covers the Themes in this Unit able you to: be should unit, end ofAt this the Unit Outcomes power wind generation. of benefits environmental and economic you the to debate enabling but also Atlas, Africa’sWind on South based maps resource interpret only you to not allowing wind power generation, behind rationale and history the explains unit briefly This Introduction SYSTEMS POWER WIND OF ECONOMIC AND ENVIRONMENTAL BENEFITS 1.1 UNIT (vi) (v) (ix) (iv) (viii) (vii) Theme 1.1.3 Advantages and Disadvantages of Wind of Wind PowerGeneration ThemeandDisadvantages 1.1.3 Advantages the and World Africa South in Theme Markets 1.1.2Energy Wind Theme 1.1.1Development of its History Wind Power AShort Applications: (iii) (ii) (i)

Ex as significant. Ex In Ex assessments. impact ronmental Ex Pr Li Africa. Ex Ex st and compare the advantages and disadvantages of wind power generation. of wind disadvantages and advantages the compare and st terpret resource maps from South Africa’s Wind Atlas. Africa’s Wind South from maps resource terpret ovide an overview of the world wind energy market and industry. and market energy world of wind the overview an ovide plain why wind power generation has a realistic potential to reduce CO potential a realistic power has generation why wind plain regarded be power can generation for wind potential the Africa South in where exactly plain plain a simplified cost structure for a wind farm. wind for a structure cost asimplified plain envi- developments, require infrastructure other all developments, like farm why wind plain plain when and where the industrial breakthrough for wind power started. for wind breakthrough industrial where the and when plain corn. grind and water to pump for centuries used been has energy how wind plain 2 emissions in South South in emissions

THEME 1.1.1 WIND POWER APPLICATIONS: A SHORT HISTORY

Introduction

Since antiquity, man has used wind energy. It is thus not a new idea. For centuries, windmills and wa- termills were the only source of motive power for a number of mechanical applications, some of which are even still used today. Humans have been using wind energy in their daily work for some 4000 years. Sails, for example, revolutionised seafaring and muscle power for rowing became almost obsolete. At around 700 A.D., farmers in present-day Iran, Afghanistan and China started using wind-powered devices consisting of rotor blades or fl apping sails on a vertical axis. Th ese early windmills were mostly

used to grind grain. Th us, we still speak of ‘windmills’ today, even when we are talking about machines THEME 1.1.1 that do not actually grind, such as sawmills and even wind turbines for generation of electrical energy.

Keywords

Th e fi rst wind-powered devices Th e fi rst horizontal-axis windmills Advanced horizontal-axis windmills Multi-blade windmills Modern wind turbines

Theme Outcomes

At the end of this theme, you should be able to: (i) Explain how wind energy has been used for centuries to pump water and grind corn. (ii) Explain when and where the industrial breakthrough for wind power started.

Deﬁ nition of Terms The First Wind-Powered Devices Th e earliest known use of wind power is of course the sail boat, and this technology had an important impact on later developments of sail-type windmills. Ancient sailors understood lift and used it every day, even though they did not have the physics to explain how or why it worked. Apart from sailing, the history of wind-powered devices shows a general evolution from the use of relatively small devices driven by aerodynamic drag forces (blades on a vertical axis) to larger material-intensive drag devices with sails or blades on a horizontal axis.

Th e fi rst windmills were developed to ease the tasks of grain grinding and water pumping and the earliest-known design is the vertical axis system developed in Persia and Afghanistan around 500-900 A.D. Th e fi rst known documented design is a Persian windmill, one with vertical blades made of bundles of reeds or wood which were attached to the central vertical shaft by horizontal struts (Figure 1). Th ese type of windmills are called panemone devices.

31 FIGURE 1: SIMPLIFIED DRAWING (SIDE AND TOP VIEW) OF AN EARLY VERTICAL-AXIS WINDMILL THEME 1.1.1

Image source: GIZ/S4GJ Grain grinding was the fi rst documented windmill application and was very straightforward. Th e grinding stone was aﬃ xed to the same vertical shaft . Th e mill machinery was commonly enclosed in a building, which also featured a wall or shield to block the incoming wind from slowing the side of the drag- type rotor that advanced toward the wind. Vertical-axis windmills were also used at around the same time in China. Here, the primary applications were also apparently grain grinding and water pumping.

32 The First Horizontal-Axis Windmills Th e fi rst windmills to appear in Western Europe were of the horizontal-axis confi guration. Th e reason for the sudden evolution from the vertical-axis panemone design is unknown, but the fact that improved water wheels also had a horizontal-axis confi guration may provide part of the answer. Another reason may have been the higher structural eﬃ ciency of drag-type horizontal machines over drag-type vertical machines, which can lose up to half of their rotor collection area due to shielding requirements. Th e fi rst illustrations (1270 A.D.) of horizontal-axis mills show a four-bladed device mounted on a central post (Figure 2) which was already fairly technologically advanced compared to the panemone type mills. Th ese early horizontal-axis mills used wooden cog-and-ring gears to translate the motion of the horizontal shaft to vertical movement to turn a grindstone. Th is gear was apparently adapted for use on post mills from the horizontal-axis water wheel already developed by Roman engineers.

FIG U RE 2: A POST MILL THEME 1.1.1

Image source: Shutterstock A post mill mounted on a single vertical post around which the whole mill can be turned manually to bring the sails into the wind.

33 Advanced Horizontal-Axis Windmills Around 1400, the Dutch started to refi ne their mill design, particularly with a multi-story fi xed tower. By pushing a large lever at the back of the mill, early horizontal-axis mills had to be oriented into the wind manually. Later inventions, such as smock mills (Figure 3) featured a revolving upper section, a so-called rotatable cap which featured the sails, the wind shaft and the brake wheel, plus the fantail and the mechanism to rotate the cap into the wind.

FI G U R E 3: A SMOCK MILL

THEME 1.1.1 Sweep

Spider Canister Striking rod

Windshaft Cap Break wheel Fantail Wallower wormdrive Sack hoist Dust floor Stock Grain hoppers Bin floor Upright shaft Shutter control chain Stones Stone floor Great spur wheel Tentering Stone nut gear Shutters

Reefing stage Drive to engine house added in 1908

Meal floor

Sack hoist chain

Meopharm Green, Kent 1820

Image source: S4GJ/GIZ A smock mill, which diff ers from post mills in that the main body does not rotate, with only the cap that rotates to face the wind.

34 Th e process of perfecting the windmills by making step-by-step incremental improvements in eﬃ ciency took another 500 years. During the second half of the eighteenth century, several complex but eff ective techniques were developed that made it possible for a traditional windmill to be left mostly unattended, at least when it came to changes in wind speed and direction. Figure 4 illustrates the mechanism that automatically adapted the positioning of the windmill into the wind. It consisted of a fantail and sophisticated gear work all made out of wood. By around 1900, the total amount of wind-powered mills in Europe was estimated to be around 200 000, compared to some 500 000 waterwheels. Windmills were built in the countryside and in cities and applications were diverse, ranging from the common water well, irrigation or drainage pumping to grain-grinding, saw-milling of timber, and the processing of other commodities such as paints and dyes.

FIGURE 4: A TECHNICAL DRAWING ILLUSTRATING THE MECHANISM FOR A SELF-REGULATING WINDMILL THEME 1.1.1

Image source: Wikimedia A technical drawing from 1820, illustrating the mechanism for a self-regulating windmill, based on sophisticated mechanical gear work that automatically adapted the positioning of the mills rotor into the wind.

35 Multi-Blade Windmills For centuries, an important application of windmills at subsistence level has been mechanical water pumping. Th ese systems were perfected in the United States during the 19th century and are direct-drive devices that transfer kinetic (wind) energy via gears, rods and a piston in a cylinder to pump water. Th ese mills had tails to orient them into the wind but the most important refi nement of the multi-fan-type windmill was the development of steel blades and improved gearboxes. In South Africa, these types of windmills are known as windpumps, given that their primary use was the pumping of water on farms.

FI G U R E 5: WINDPUMPS AT THE LOERIESFONTEIN MUSEUM, SOUTH AFRICA THEME 1.1.1

Image source: https://upload.wikimedia.org/wikipedia/commons/f/fd/WindmillMuseumLoeriesfontein01.jpg

Modern Wind Turbines Th e development of modern wind turbines that generate electrical energy began with technical innovations in the fi eld of aerodynamics, mechanical/electrical engineering, control technology and electronics. Since 1980, wind turbines have become larger and more eﬃ cient at rates otherwise only seen in computer technology.

Today, large-scale wind turbines (Figure 6) have the following primary components: (i) A rotor, which consists of two or more propeller-like blades that are tied to a rotating shaft . Th e force of the wind turns the blades, which transfer the kinetic energy into a rotating shaft , which in turn spins a generator to produce electric charges. (ii) A nacelle, which is the enclosed body of the turbine. In a large wind turbine the nacelle houses the drive train, gearbox and generator, or a gearless direct-drive generator. (iii) A tower, which supports the rotor and nacelle. Th e tower elevates the turbine in order to increase exposure to higher velocities of wind. (iv) A mainframe, which is a structure that contains the slip ring. It connects the nacelle and its wiring to the tower in such a way that the rotor can spin freely and face into the wind.

36 FIGURE 6: A SIMPLIFIED SCHEMATIC VIEW INTO A WIND TURBINE

Rotor blade

Wind Gear box Nacelle

Generator Overhead powerlines

Power cables THEME 1.1.1

Tower

Transformer

Image source: GIZ/S4GJ

But let us look back in history. In 1920 and 1926, Albert Betz, a German physicist and a pioneer of wind turbine technology, determined the maximum wind turbine performance, now called the ‘Betz limit’, and the optimal geometry of rotor blades. In 1950, a German professor named Ulrich Hütter detailed the theoretical basics for modern turbines with rotors of two or three blades. Hütter’s theory for blade- element momentum, developed from his aeronautical background, is said to be current even today. He applied modern aerodynamics and modern fi bre optics technology to the construction of rotor blades on the wind turbines in his experimental system.

Even earlier in the late 19th century, Poul la Cour, a Danish scientist did some experimental work on aerodynamics and practical implementation of wind power plants. He was the fi rst in Denmark to install a generator into a windmill using the mill to produce electrical energy. At the same time he educated many electricians and made it possible for farmers and craft smen to establish small power plants in the countryside. In the 1980s, Danish scientists developed small turbines with a nominal output of 20 kW to 100 kW. Th anks to state subsidies, these turbines were set up on farms and on the Danish coast to provide electric power. At the same time (1980s) in other countries, research focused on large systems, two examples being NASA’s research in the US or the German GroWiAn project. Unfortunately, these plans turned out to be too ambitious and the research at the facilities was discontinued.

However, higher cost of conventional electrical energy generation and severe environmental impacts of fossil fuels on the one hand and excellent wind resources in northern Europe on the other hand created a small but stable market for single, co-owned wind turbines and small clusters of machines. Aft er 1990, more market activity shift ed to Europe and Asia. Driven by high utility power purchase rates, the installation of 50 kW, then 100 kW, then 200 kW, then 500 kW and now 5+megawatt wind turbines by commercial consortiums and private landowners in the Netherlands, Denmark and Germany has been particularly impressive. Today large wind turbine manufacturers such as Nordex, Siemens and Enercon in Germany, Ming Yang, Goldwind and United Power from China, Gamesa in Spain, General Electric in the United States, the Sulzon Group from India and, the largest of all, Vestas in Denmark are the industry leaders. By the end of 2015, global wind power generating capacity totalled over 430 000 mega- watts (430 GW). Key attributes of this current period are: scale increase (Figure 7), commercialisation, competitiveness, grid integration, energy independence, environmental benefi ts (climate change) and turbine standardisation. Th ese type of turbines usually use 3-blade upwind, horizontal-axis rotors on a monopole tower, and direct-drive systems connected to a synchronous AC permanent magnet generator. Because the generator’s speed determines both its potential and frequency, an inverter rectifi es the ‘wild AC’ to DC and then converts it back to AC before connecting to the grid.

37 F I G U R E 7: A 7 MW OFFSHORE WIND TURBINE

THEME 1.1.1 A 380

79.80 meters

154 meters

Image source: GIZ/S4GJ Current 7 MW off shore wind turbines have a rotor diameter of 154 m. Th e length of each blade is roughly the same as the wingspan of an Airbus A380.

38 Exercises

1. List the earliest known uses of wind power. Where and when exactly were these devices developed?

……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

2. Explain the design of panemone-type windmills and explain how they function. THEME 1.1.1 ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

3. What type of windmills were developed aft er the panemone types? Explain their technologically advanced setup compared to the panemone type of windmill!

4. Try drawing the mechanical mechanism early horizontal-axis mills used, i.e. wooden cog- and-ring gears, to translate the motion of the horizontal shaft to vertical movement to turn a grindstone.

39 5. Explain the process of perfecting horizontal-axis windmills, focussing on the mechanism for self-regulating windmills, i.e. positioning of the rotor into the wind!

6. In South Africa, multi-blade windmills are known as windpumps. Explain how these mills moved themselves into the wind!

THEME 1.1.1 ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Further Information on the Resource CD

Historical development of windmills, Springer, PDF

40 THEME 1.1.2 WIND ENERGY MARKETS IN SOUTH AFRICA AND THE WORLD

Introduction

In this theme, we provide you with an overview of the world’s wind energy market and present wind resource maps from South Africa’s Wind Atlas. Furthermore, we will explain where exactly in South Africa the potential for wind power generation can be regarded as signifi cant. THEME1.1.2 Keywords

Global wind power generation in 2015 Wind Atlas South Africa (WASA) Wind power projects Renewable Energy Independent Power Producer Procurement (REI4P) Programme

Theme Outcomes

At the end of this theme, you should be able to: (i) Provide an overview of the world wind energy market and industry. (ii) Interpret resource maps from South Africa’s Wind Atlas. (iii) Explain where exactly in South Africa the potential for wind power generation can be regarded as signifi cant.

Deﬁ nition of Terms Global Wind Power Generation in 2015 In 2015, the wind power industry set new records across the world. Wind power is leading the transformation of global power systems. Wind power can now be considered mainstream, supplying competitive, reliable and clean energy for economic growth and cutting emissions in established economies. At the same time, the technology is creating new jobs in manufacturing and maintenance and is enhancing energy security. Th ese developments are long overdue and very necessary to achieve the climate objectives agreed internationally in Paris (2015) and in Marrakech (2016). Th e Paris Agreement requires decarbonised power generation by 2050 (if not before), to keep the temperature increase below 2°C above pre-industrial levels.

41 FIGURE 1: GLOBAL CUMULATIVE INSTALLED WIND POWER CAPACITY (2000 – 2015)

450,000 MW 432,883 400,000 369,705 318,463 350,000 282,842 300,000 238,089 250,000 197,946 159,016 200,000 120,690 93,924 150,000 73,957 59,091 39,431 47,620 100,000 17,400 23,900 31,100

THEME1.1.2 50,000 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Image Source: Th e Global Wind Energy Council (GWEC 2015).

Globally, at the end of 2015, almost 433 GW of wind power was installed in total (Figure 1). Particular- ly the Chinese industry continues to amaze, having installed no less than 30.8 GW of new capacity in 2015. China thus surpassed the EU in total installations, ending 2015 with 145 GW in total (Figure 2). Both Europe and the US markets performed respectably as well. Th e European off shore sector set a new record, installing over 3 GW in 2015. At the same time, new markets are emerging across Africa, Asia and Latin America.

At the end of 2015, the number of countries with more than 1 GW installed capacity was 26, including 17 countries in Europe, 4 in Asia-Pacifi c (China, India, Japan & Australia), 3 in North America (Canada, Mexico and U.S.), 1 country in Latin America (Brazil) and 1 country in Africa (South Africa). By the end of 2015 eight countries had more than 10 GW installed capacity, including China (over 145 GW), the U.S. (over 74 GW), Germany (almost 45 GW), India (over 25 GW), Spain (over 23 GW), UK (over 13 GW), Canada (over 11 GW), and France (over 10 GW). China already crossed the 100 GW mark in 2014, adding another milestone to its already exceptional history of renewable energy development.

42 FIG U RE 2: TOP 10 COUNTRIES WITH THE HIGHEST CUMULATIVE INSTALLED WIND POWER CAPACITY (2015)

Rest of the world

PR China

Brazil Italy France

Canada THEME1.1.2 United Kingdom

Spain

India USA

Germany

Country MW % Share PR China 145,362 33.6 USA 74,471 17.2 Germany 44,947 10.4 India 25,088 5.8 Spain 23,025 5.3 United Kingdom 13,603 3.1 Canada 11,205 2.6 France 10,358 2.4 Italy 8,958 2.1 Brazil 8,715 2.0 Rest of the world 67,151 15.5 Total TOP 10 365,731 84.5 World Total 432, 883 100

Data/Image Source: Th e Global Wind Energy Council (GWEC 2015).

43 Wind Atlas South Africa (WASA) WASA (2009 to 2014) is an initiative of the Department of Energy where the South African National En- ergy Research Institute (SANERI) coordinates and contracts contributions from the implementing partners, such as the Council for Scientifi c and Industrial Research (CSIR) and the University of Cape Town (UCT). Th e Wind Atlas shows the generalised, climatological (30 year) annual mean wind speed (m/s) at 100 m above ground level for the Northern Cape, Western Cape and Eastern Cape. Th e wind resource map depicts the local wind resources that a wind turbine would encounter at a particular location. Th e WASA Large Scale High Resolution (250m) Wind Resource Map (Figure 3) confi rms that South Africa has excellent wind resources.

Th e latest technology has been used to map the wind resources in the Eastern, Western and parts of Northern Cape provinces of South Africa. Th e results confi rm a very high potential with a number of locations with an annual average wind speed of more than 8 m/s (orange/red) and between 6 and 8 m/s

THEME1.1.2 (green/yellow). Th e average wind resource potential reported for South Africa is thus high. Th e WASA map shown in Figure 3 reveals the presence of high wind speeds along the coasts of the KwaZulu-Natal, Eastern Cape, Western Cape, and Northern Cape provinces. Th e Atlas is consistent in showing that the Eastern, Western and Northern Cape provinces are the most favourable locations for wind energy projects. South Africa is endowed with good wind resources and it is important to mention that it also boasts policies and programmes that support the development of a utility-scale renewable energy sector.

FI G U R E 3: LARGE-SCALE HIGH RESOLUTION WIND RESOURCE MAP

Data/Image Source: WASA project (2014)

44 Wind Power Projects Th e WASA initiative came at a critical time in the development of the wind industry in South Africa. Th e extremely robust aﬃ rmation it provided of the excellent wind resource in the country and its wide geographical distribution served to enhance developer interest and urgency and to reassure policy makers that wind is a reliable energy source. Th ese aspects have been instrumental in the rapid growth and the success of South Africa’s wind industry. Wind turbines are thus largely located along the coastal regions of the Eastern, Northern and Western Cape provinces based on the strong wind resources along these shores and further inland. Th e following graphics (Figure 4 and Table 1) detail South Africa’s wind energy projects, and where they are located. Th e Eastern Cape has the highest number of wind projects (16), the Western Cape follows with 10 and the Northern Cape with 8. With numerous utility-scale wind farm projects in South Africa, the wind-energy landscape in the country is continuing to expand.

FIGURE 4: WIND ENERGY PROJECTS IN SOUTH AFRICA THEME1.1.2

Pretoria 12

Bloemfontein

16 10

18 19 20 21 23 8 25 7 South Africa 36 17 32 24 26 2 5 14 28 31 1 3 11 13 35 Cape Town 15 34 6 22 33 27 29 30 9

Image Source: Data from REI4P project database, http://energy.org.za/ (November 2016). See also Table 1.

45 TA BLE 1: WIND ENERGY PROJECTS IN SOUTH AFRICA

Capacity Nr. Name Programme Nearest Town Status (MW) Amakhala Emoyeni 1 134.4 REI4P Window 2 Bedford Fully operational (Phase 1) 2 Chaba 20.6 REI4P Window 2 Komga Fully operational 3 Cookhouse Wind Farm 135 REI4P Window 1 Cookhouse Fully operational Approvals, planning 4 Copperton Windfarm 102 REI4P Window 4 Copperton and financing 5 Darling Wind Farm 5.2 Other Yzerfontein Fully operational Dassiesklip Wind Energy 6 26.2 REI4P Window 1 Caledon Fully operational Facility Molteno/ THEME1.1.2 7 Dorper Wind Farm 97 REI4P Window 1 Fully operational Sterkstoom 8 Eskom Sere Wind Farm 100 Other Koekenaap Fully operational Excelsior Wind Energy Approvals, planning 9 32 REI4P Window 4 Swellendam Facility and financing Approvals, planning 10 Garob Wind Farm 136 REI4P Window 4 Copperton and financing Approvals, planning 11 Golden Valley 120 REI4P Window 4 Cookhouse and financing 12 Gouda Wind Facility 135.2 REI4P Window 2 Gouda Fully operational 13 Grassridge 59.8 REI4P Window 2 Port Elizabeth Fully operational 14 Hopefield Wind Farm 65.4 REI4P Window 1 Hopefield Fully operational 15 Jeffreys Bay Wind Farm 138 REI4P Window 1 Jeffreys Bay Fully operational Approvals, planning 16 Kangnas Wind Farm 137 REI4P Window 4 Springbok and financing Approvals, planning 17 Karusa Wind Farm 140 REI4P Window 4 Sutherland and financing 18 Khobab Wind Farm 138 REI4P Window 3 Loeriesfontein Under construction Kouga Wind Farm - 19 80 REI4P Window 1 St Francis Bay Fully operational Oyster Bay Loeriesfontein 2 Wind 20 138 REI4P Window 3 Loeriesfontein Under construction Farm Longyuan Mulilo De Aar 21 2 North Wind Energy 139 REI4P Window 3 De Aar Under construction Facility Longyuan Mulilo De Aar 22 Maanhaarberg Wind 96 REI4P Window 3 De Aar Under construction Energy Facility MetroWind Van Stadens 24 27 REI4P Window 1 Port Elizabeth Fully operational Wind Farm 25 Noblesfontein 72.8 REI4P Window 1 Noblesfontein Fully operational 26 Nojoli Wind Farm 87 REI4P Window 3 Cookhouse Under construction Noupoort Mainstream 27 79 REI4P Window 3 Noupoort Fully operational Wind Approvals, planning 28 Nxuba Wind Farm 140 REI4P Window 4 Cookhouse and financing Approvals, planning 29 Oyster Bay Wind Farm 140 REI4P Window 4 Oyster Bay and financing Perdekraal East Wind Approvals, planning 30 108 REI4P Window 4 Matjiesfontein Farm and financing 31 Red Cap - Gibson Bay 111 REI4P Window 3 St Francis Bay Under construction Approvals, planning 32 Roggeveld 140 REI4P Window 4 Sutherland and financing

46 The Soetwater Wind Approvals, planning 33 139 REI4P Window 4 Laingsburg Farm and ﬁnancing Tsitsikamma Communi- 34 94.8 REI4P Window 2 Tsitsikamma Fully operational ty Wind Farm 35 Waainek 23.4 REI4P Window 2 Grahamstown Fully operational Wesley-Ciskei Wind Approvals, planning 36 33 REI4P Window 4 Peddie Farm and ﬁnancing 37 West Coast 1 90.8 REI4P Window 2 Vredenburg Fully operational Total 3460.6 Source: REI4P project database, http://energy.org.za/ (November 2016)

Renewable Energy Independent Power Producer Procurement Programme (REI4P)

Most of these projects form part of the Renewable Energy Independent Power Producer Procurement THEME1.1.2 Programme (REI4P), which aims to procure 17.8 GW of renewable energy capacity by 2030. Th e REI4P is proving to be extremely successful in assisting to meet South Africa’s energy demand, which has had a number of concerns over recent years due to demand exceeding supply capabilities. Apart from miti- gating slowed economic development growth due to unpredictable provision of power, the programme also encourages foreign investment, as well as a number of socio-economic benefi ts due to job creation and skills development. Th e programme will continue to provide benefi ts over the upcoming bidding periods, as well as permanent benefi ts through the development of local factories, as well as job creation and skills development.

Funding is provided through a variety of foreign private equity, local private equity and large commercial and development banks. Some of the funding is composed of local private equity funds for black economic empowerment purposes to represent surrounding communities. Approved projects of the programme thus far represent over R192 billion of which 28% is attributed to foreign investment. So far four rounds of bidding have been completed, with the fi ft h round of bidding to be held in 2017. Projects covered by the REI4P are amongst others, onshore wind, photovoltaic, concentrated solar power, biomass, landfi ll gas, small hydropower and biogas. In just four years, the REI4P alone has already delivered over 5 GW throughout 79 diff erent projects, which accounts for over a quarter of the 2030 renewable energy target.

47 Exercises

1. Using the GWEC data from 2015, list and rank the eight countries that had more than 10 GW of wind power installed according to their installed capacity!

2. What kind of information does the large-scale high resolution resource map in the Wind Atlas South Africa (WASA) demonstrate?

3. According to the WASA resource map, where are the most favourable locations for wind energy projects? Be as specifi c as possible!

4. Verify/compare your answer in question 3 with the facts given in Figure 4 and Table 1, i.e. locations and capacity of South Africa’s wind energy projects!

5. Th e Renewable Energy Independent Power Producer Procurement Programme (REI4P) aims to procure almost 18 GW of renewable energy capacity by 2030. Is there already any indica- tion that this target will be met?

48 Further Information on the Resource CD

(i) Global Wind Report: Annual Market Update, Th e Global Wind Energy Council (GWEC), April 2016, Brussels. (ii) Wind Atlas for South Africa (WASA), Council for Scientifi c and Industrial Research (CSIR), April 2014. (iii) Wind Atlas for South Africa Phase 1, SANERI, 2015 (iv) Wind Energy Localisation Study, Department of Trade and Industry (DTI), 2015. (v) REI4PP focus on wind, DoE/IPP Oﬃ ce, Quarter 1, 2015/16. THEME1.1.2 Your own notes

49 THEME 1.1.3 50 energy technologies such as photovoltaic or wind power plants. power plants. photovoltaic as or such wind technologies energy (i) (energy effi use of energy through reduction plished ciency), and/or (ii) more renewable/clean by using accom- be potentially of can GHG Reduction emissions technology. and of information availability the and will political specifi country circumstances, on,alia, inter depends socio-economic c mate change (GHG) gas Th greenhouse by reducing emissions. change torespond climate cli- mitigate to capacity e can Technogolies countries 2, NQF Energy Renewable Level book student the in indicated already As Scenario Mitigation Definition Terms of able you to: be should theme, end ofAt this the Outcomes Theme Keywords power wind generation. of disadvantages and Th theadvantages theme with we present you this in us, Eskom’s calculated. from is power plants energy coal of electrical unit per price the when account into Thtaken not costs. usually health and unfortunately of social are terms ey in and terms monetary in both Th change. climate and aremassive, impacts costs ese health human pollution, water of and water costs energy. Th we pay price forthe electrical the in not included are that areinstance for costs ese hidden offREI4P power andhave nuclear huge coal aside, of price ered average prices Market per cents 74 kWh. of the three round power in generation wind while R1.00/kWh, around Eskom’s costs plants coal new from energy power. nuclear of electrical and Aunit coal than cheaper already thus are technologies gy Most renewable ener- Sun. powered by are the they as or photovoltaic technologies, for wind required are input coal-fi costs for their little to buy energy. coal No or very power to electrical generate red plants Thsuffi is ere toready ESKOMand go. reliable viable, needs wind power is that evidenceavailable cient Introduction GENERATION POWER WIND OF DISADVANTAGES AND ADVANTAGES 1.1.3 THEME (iv) (iv) (iii) (ii) Reduction in CO in Reduction scenario Mitigation (i) (i) Simplififarm wind for a structure cost ed methodology and process EIA mitigation Impact assessments impact Environmental power systems of wind disadvantages and Advantages power systems of wind assessment cycle Life Explain asimplififarm. wind for a Explain structure cost ed assessments. impact environmental require developments, infrastructure other to all developments, similar farm why wind Explain power generation. of wind disadvantages and advantages the compare and List Africa. South Explain why wind power generation has a real potential to reduce CO potential areal power has generation why wind Explain 2 emissions 2 emissions in in emissions energy demand. energy in sudden peaks to meet used be also can supply and bolster can for example, gas, natural times peak During transition. agradual is renewable technologies in increasingly investing over nuclear time; and suffi almost an on ensure coal reliance its will decrease can Africa energy. South cient supply of electrical area supply fl reduces wide spread geographical wind over a of renewable resources mix A risks. uctuation provider. Th energy alow-cost bulk as used be of can energy,Wind for example, seasonality low e very grid. national the into of renewable technologies integration for an conditions perfect has Africa South Image source: S4GJ/ GIZ S4GJ/ source: Image 1: FIGURE On the other hand: other the On some facts: recall thus us Let

Electricity demand (iii) (ii) (i) (iii) (ii) (i) Wind power generation costs are already competitive. competitive. already are powerWind costs generation recent years. in rapidly power, increased wind has particularly growth, technology energy Renewable demands. global current exceeds services Th to supply energy technologies of renewable/clean energy potential technical e GHG concentrations. atmospheric in increase to the signifi contribute sources fuel of provision fossil the from cantly resulting GHG emissions etc.). (coal, gas fuels by fossil dominated still are systems energy Current increasing. is services for energy Demand energy increasesenergy renewable as down shut are coal plants old time, over are built plants coal new No A POSSIBLE TRANSITION TO RENEWABLE/CLEAN ENERGY ENERGY RENEWABLE/CLEAN TO TRANSITION APOSSIBLE GENERATION OVER TIME OVER GENERATION Time increases sources other from drops, output coal power As energy output Coal power output output energy Renewable Total energy output 51

THEME 1.1.3 THEME 1.1.3 52 al generation technologies. technologies. generation al convention- renewable and from generation electricity on utility-scale studies LCA 2,100 published more than considered NREL “harmonisation.” called aprocedure through estimates GHG in emissions reduce variability where possible, and, of variability sources primary identify literature, LCA the approach to review systematic a applied and developed NREL at the Analysts to reduce uncertainty. aiming literature, published the in confl and inconsistent estimates icting clarifying generation, for conventional GHG renewable and emissions Th project. sation (NREL) Laboratory cycle life of Energy Renewable estimates e National ers moreprecise off (LCA) Harmoni- Cycle Assessment of form aLife U.S. in the from available comprehensive is A very study decisions. investment and policy, planning to inform technologies generation conventional renewable and from on GHG emissions information comprehensive most accurate the and need lawmakers and utilities lenders, - dialogues of national part becoming increasingly is energy Clean cycle. life entire over even their ideally technologies are thus, in general, considerably lower than those of fossil fuel options. fuel of fossil those lower considerably than general, in thus, are technologies of GHG renewable emissions Lifecycle technology. for each estimates on median based able technologies coal-fi renew- to grave, than kilowatt-hour cradle more per GHGstimes 20 about releases generation red from For example, fuels. fossil from those than variable less much lower are generally and energy nuclear and from renewables cycle GHG emissions life Ththe total that show study NREL the of results ese or blue/turquoise). (grey/white gas for natural except percentile)75th highlighted is and Th 25th (between range maximum. and value, percentile 75th interquartile e value, percentile 50th value, percentile 25th minimum, range: following the using data as-published the with compared and data 126/126/47. fore.g. wind harmonised the on based calculated Th was information distributional e study, the in references used of unique number the and data harmonised the data, published reviewed of PV, category, number i.e. resource the each note displays that Please CSP, coal nuclear, and gas wind, Project Harmonization LCA NREL source: Data 2: RE U FIG to reduce CO potential a realistic power has generation wind whether arises tion ques- the over generation time, to renewable energy transition the i.e. scenario, amitigation such Considering Reduction in CO

Life cycle greenhouse gas emissions (g CO2 e/kWh) Renewable PV PV (46/46/17) COMPARISON OF LIFE CYCLE GREENHOUSE GAS EMISSIONS EMISSIONS GAS GREENHOUSE CYCLE LIFE OF COMPARISON TECHNOLOGIES GENERATION CONVENTIONAL AND RENEWABLE FOR 2 Emissions CSP (42/42/13) CSP Wind (126/126/47) Wind 1,700 1,360 1,020 340 680 0 Nuclear (130/130/34) Nuclear Non-Renewable Natural gas (62/na/38) 2 emissions in South Africa, Africa, South in emissions C o al (164/164/51) al Advantages justifi is technology renewable energy and ed. clean this surrounding controversy whether determine you can that so now present We of most these will turbines. Thwind options. fuel of of fossil those disadvantages lower and than manyareadvantages ere however considerably are power systems of GHG wind emissions section, assessment cycle life the in indicated As Systems Power Wind of Disadvantages and Advantages Project Harmonization LCA NREL source: Image FI G U R E 3: E R U G FI of operation. upstream of are GHG emissions majority the power plants, of GHGs. For wind majority vast the emits operation during combustion fuel plants, for showscoal-fi that coal power and for wind stage each of from GHGproportions emissions power red and stages cycle life Comparing technologies. of energy comparisons facilitate and to grave” “cradle from burdens environmental help determine can systems (LCA) of energy assessments cycle life indicated, As Life Cycle of Wind Assessment Power Systems (ix) (ix) (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) ~1000 gCO ~1000 ~10 gCO vide a return on investment. areturn vide pro- will installation turbine or not awind whether determine will consultants where specialist consulting, energy wind in also and maintenance and installation of turbines, manufacture the for i.e. created, have jobs been boomed, has industry energy wind where the countries many In costs. low running have fairly and low relatively maintenance are turbines Wind power to remote bring locations. can turbines Wind technologies. energy clean other coupled be with can and scale domestic on a installed be also but can installations to industrial-scale not limited are turbines Wind minimal. is base at the area land on the impact but the ground Th footprint. environmental the above small have arelatively high toweris eir turbines Wind free. is energy wind sources, energy some other Unlike generations. future to support them allowing Th fuel. fossil resources, these to burn need the reduces helpconserve to can energy is Wind Thoperation. of areupstream ofemissions GHG e majority security. energy also thus and mix energy the increases and off fuel poweron fossil supply. dependency country’s a reduce power can sustainable ers Wind energy wind gas, and oil coal, as such reserves fuel fossil Unlike arenewable resource. is Wind WIND COAL Life Cycle Life COMPARISON OF LIFE CYCLE STAGES AND GHG EMISSIONS EMISSIONS GHG AND STAGES CYCLE LIFE OF COMPARISON 2 eq/kWh 2 eq/kWh FOR WIND AND COAL POWER COAL AND WIND FOR • • • • • • • Upstream Processes construction Construction materials Construction manufacture Power construction plant Raw materials extraction Wind/turbine/farm manufacture Parts Module manufacture Raw materials extraction ~ 86% < 1% • Power plant operation operation plant Power • • • • • and operation Plant • • Operational Processes Operational Coal combustion Coal transport preparation Coal mining Coal and maintenance maintenance Power generation > 98% ~ 9% ~ 9% • turbine/farm Wind • • Coal mine land rehabil- land mine Coal • • Downstream Processes Downstream decommissioning sioning itation Power decommis- plant Waste disposal Waste ~ 5% < 1% <

THEME 1.1.3 THEME 1.1.3 54 TA BLE 1: BLE TA later. them to mitigate trying than of rather aproject Th considered. is negative thorisation isminimise to beginning avoid or the objective main from e ects eff identifi are of projects impacts before that au- ensures assessed which and procedure ed the as assessment ThAct 107 of1998)(NEMA, Management Act defi Environmental impact e National environmental nes necessary. when mitigated and fore assessed be there- must installations energy wind from impacts Potential bats. and birds including vertebrates and invertebrates affinclusive of plants, consideredfor to be need all organisms fragmentation living ected and of habitatloss issues the mortality, and disturbance to species addition In impacts. visual and noise of form the in for example communities, and on biodiversity, land-use impacts environmental vourable unfa- (EIA). lead to Th possibly may assessments turbines impact wind of operation and e construction environmental developments, require infrastructure other to all developments, similar farm Wind Assessments Impact Environmental Disadvantages Habitat fragmentation Habitat fragmentation heritage cultural on Impacts safety Air interference Electromagnetic biodiversity on Impacts use Land impact Noise impact Visual DescriptionImpact (v) (v) (iv) (iii) (ii) (i) down to personal opinion, public acceptance of wind farms can be controversial. be can farms of wind acceptance public opinion, to personal down to come tends this While landscape/nature. the in structure atechnical i.e. pollution, Visual objection. public strong face and away dwellings from planned usually are farms wind new audible eff i.e. Noise pollution, severe. be turbine’sthe can rotors by generated ects is why is Th rates. mortality to high contributing are and bats and birds primarily to wildlife, athreat pose turbines Wind greater. even become For off grid. national to the costs connected and foundation farms top of apre-built wind shore on erected and transported manufactured, to be need will turbine wind the adequate, deemed over a signifi speeds If wind time. of period cant measuring involves out which carried to be needs survey a site First, expensive. is considered turbines wind Thlarge-scale of installation e wind resources). or outsea at hills on (constant top of coast, the Thalonging). are built turbines wind whyis is blow- not (wind is always source energy aconstant not is always wind because systems voltaic to photo- similar have adrawback power can wind inexhaustible, and abundant is wind Albeit POTENTIAL IMPACTS ASSOCIATED WITH WIND POWER AND AND POWER WIND WITH ASSOCIATED IMPACTS POTENTIAL WIND FARM DEVELOPMENT FARM WIND SALA SALA NHRA NEMA, CAA CAA NEMBA, NEMA, NFA NEMPAA, NEMBA, NEMA, B2, B3 NHRA NWA, NEMPAA, NEMICMA, NEMBA, NEMA, Act Health NEMBA, NEMA, NEMA Legislation Relevant B19 B19 B2, B11 B20 B2, B3, B20 B2, B21 B3, B6, B2, B3, B5, B9, B6, B11 B2 B) (Part Reference T h e EIA process (Figure 4) can be divided into 4 distinct components: Thdistinct into 4 divided be can 4) (Figure EIA process e CD. resource on the available is (DEA) for review authority submitted (Act Act No. Management 107 of afull/fi 1998). Environmental example, report National EIA an As the nal 5 of of Chapter terms promulgated in guidelines associated 387 and R. and 386 ment 385, No. R. Notice R. Govern- the under published regulations through controlled is complex and thus is process EIA An based. are they on which information the and for decisions accountability and environment, of the understanding approach to development, abroad participatory and atransparent making, decision informed planning, pro-active comprise short, in which, (IEM) Management Environmental of Integrated principles on the equitably. Th these assess must EIA based are the and EIA procedures e aspects bio-physical and economic social, includes this Africa South In development (minimised). proposed avoidedto the are or mitigated due may occur that impacts potential that to ensure used tool alegislative is EIA an indicated, already As EIA Process and Methodology include: power installations wind with associated measures afimitigation Common (usually applicant project by the standards. to applicable EIA therm) to prepare contracted to be needs practitioner assessment environmental independent An impacts. positive enhance and project-specifi impacts negative mitigate regulations, to EIA designed be to the need under c measures (EIA) Assessment Impact Environmental for need an the power triggers project wind anew Assuming MitigationImpact (iii) (ii) (i) (xi) (x) (ix) (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) • • • phase assessment Impact • • • • • phase Scoping • • • notification initial and Application post-project pre- and development. during mals ani- other and bats and birds invertebrates, including species of relevant monitoring Continuous species. migrating and hunting nesting, to deter on appropriate infrastructure measures raptor-proof or poles similar Installing animals. other and bats birds, of invertebrates, attraction and munities, com- to visible disturbance pollution, light development order to minimise in lighting Minimising turbines. with prone to colliding species or other raptors nesting discouraging thus features, landscape as Confi to avoid attraction turbines guring Burying electrical transmission infrastructure. species. and habitats receptors, resources, of presence sensitive the to assess surveys social and environmental pre-disturbance Conducting asite-specifi implementing and Developing plan. management spill c loss. habitat or and/ displacement to disturbance, collision-prone or vulnerable are and ranges, or have restricted threatened are that those especially for developments habitats species, away sensitive from Locating areas. routes/corridors nesting/breeding and migratory animals' other and bats and birds invertebrates, relevant outside of all Site selection measures. erosion reduction noise control- and disturbance-, control-, dust visual adequate Implementing ticable. prac- much as as areas disturbed and roads existing project’s by utilising the footprint Minimising cations to be adhered to during the construction and operational phases of the project. of the phases operational and construction the to during adhered to be cations specifi environmental prescribe - will (EMP) which Plan Management Environmental an Compile signifi to reduce the impacts. recommendations and potential of measures cance mitigation Identify identifi alternatives proposed and phase. scoping the issues in ed of all assessment specialist Detailed considered. may be that alternatives the investigate and Describe PPP. and investigation through impacts environmental potential Identify (PPP). Process Participation Public a Aff and conducting by Interested (I&APs)authorities and relevant Identify Parties ected environment. surrounding the impact potentially will project proposed how the Establish area. of the standing under- an order to establish in area study proposed on the information gather and Investigate boards. notice bids and letters, tion notifi adverts, newspaper alia, inter ca- development proposed of public the through the Notify 14 (within days). application EIA of the acknowledgement DEA Aff of Environmental (DEA). Department airs to the application EIA Submit an 55

THEME 1.1.3 THEME 1.1.3 56 Image source: GIZ/S4GJ source: Image 4: FIGURE (iv) (iv) • • • • • • • 30 day comments period comments day 30 30 day comments period comments day 30 Advise I&APs of decision of I&APs Advise Public Participation Public Participation Gazette authorities Other Ward Councillor Newspaper adverts Newspaper Municipality Landowners Notice boards • Decision may be positive or negative based on information received in the scoping and impact impact and scoping the in received on information based or negative positive may be Decision • (project developer) applicant to the (EA) once has DEA issued Authorisation Environmental • (EA) Authorisation Environmental • Process (PPP) Process assessment phases. project. proposed the regarding adecision made As with the scoping phase, the PPP is an integral and important part of the impact assessment phase. assessment impact of the part important and PPP integral the an is phase, scoping the with As A TYPICAL EIA PROCESS FOR A WIND POWER PROJECT PROJECT POWER AWIND FOR PROCESS EIA ATYPICAL PPP PPP PPP PPP ( SIMPLIFIED • Solicit comments on the Draft EIR /EMP EIR Draft the on comments Solicit • • to submit and Report Scoping Final Prepare • Report Scoping Draft on comments Solicit • of Plan and Report Scoping Draft Prepare • • • • • ) Statements (EIS) Statements EIA for Study Submit application to authorities including Submit to authorities consent of landowner(s) and fee application interest, of declaration (EIR), draft EMP and Environmental Impact Impact Environmental and EMP draft (EIR), Conduct public participation process authorities Prepare Draft Environmental Report Impact Prepare Draft relevant authorities andNotify landowners Prepare Final Environmental Report. Impact Decision Task Authority to reply in 30 days 30 in reply to Authority • • • • • • • Authority to decideAuthority within Authority to acknowledge Authority receipt within 14 within days receipt tance authority must grant grant must authority tance Accept report Accept report Reject report Request amendments Refer for reviews Require amendments Reject report Within 45 days of accep- of 45 days Within authorisation or refuse Environmental Environmental Authorities 60 days to to days 60 Data: Calculated based on selected data for European wind turbine installations (EWEA, 2007) (EWEA, installations turbine wind forEuropean data onselected based Calculated Data: MEDIUM ATYPICAL OF STRUCTURE COST 2: TABLE cost. turbine overall of the share their and turbine components of awind main Table the and 3indicates turbine wind 2MW of atypical structure CD. price Table resource the on the 2indicates available is power illustration project ple, awind (O&M). measurement exam- and an As observation and to fuel related are for technologies conventional diff very thus is farm 40-70% or wind as erent, costs of turbine of awind structure cost the technologies, fuel fossil to conventional Compared etc. equipment,grid-connection electrical foundation, turbine, the of cost the as such to “upfront” related is costs turbine for awind of energy cost total of the 90% Over Simpliﬁed Cost aWind for Structure Turbine/Farm Your notes own Total systems Control Road construction costs Financial Consultancy Electric installation rent Land Foundation Grid connection Turbine (ex works) WIND TURBINE Share of total costs (%) costs total of Share 100 0.3 0.9 1.2 1.2 1.5 3.9 6.5 8.9 75.6 - SIZED SIZED ( 2 MW ) 57

THEME 1.1.3 THEME 1.1.3 58 MAIN COMPONENTS OF A 5 MW WIND TURBINE AND THEIR THEIR AND TURBINE A WIND OF 5 MW COMPONENTS MAIN 5: FIGURE thus produce electrical energy on par or even below the cost of fossil fuels. fuels. of fossil cost or below even the on par energy produce electrical thus can at ESKOM’s of Africa coal new cost South predicted power stations. the (kWh), than 26% i.e. cheaper 74 averaged REI4P,energy akilowatt-hour cents of the wind three round In dramatically. dropped have projects farm wind for new prices Africa, South to fiin Due industry wind the in competition erce nents of a large-size wind turbine (5 MW) and their share of the overall turbine cost. cost. turbine overall the of share their and (5 MW) turbine wind alarge-size of nents compo- Main 2007). (EWEA, tower metre a100 and blades length metre 45.3 with turbine onaRepower based are Figures Data: GIZ/S4GJ source: Image 8 10 2 OVERALL SHARE OF TURBINE COSTS TURBINE OF SHARE OVERALL 2 7 3 1 14 13 12 11 10 4 5 9 6 8 Nr 14 9 Tower Transformer Yaw system Total Gearbox Generator Components Rotor bearings Rotor blades Nacelle housing Brake system Rotor hub shaft Main Main frame Power converter Pitch system 1 7 12 3 13 11 Share of total costs (%) costs total of Share 26.3 22.2 2.8 2.6 3.5 3.6 1.2 13.0 1.2 1.3 1.3 1.4 1.9 5.0 86 4 6 5 1. 1. Exercises 4. List the advantages and disadvantages of wind power systems in the table below. table the in power systems of wind disadvantages and advantages the List 4. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… 3. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… generation, energy conventional and renewables from GHG cycle emissions life the Compare 2. Advantages for the vertical and horizontal axis. horizontal and vertical for the power categories output and as demand energy time, using adiagram, in scenario transition gradual and apossible Illustrate grid. national the into renewable technologies by integrating over nuclear time and on coal reliance its to decrease conditions perfect the has Africa South emissions for wind and coal power. coal and for wind emissions of GHG terms in downstream) and operational (upstream, stages cycle life the Compare to grave’. cradle ‘from i.e. Disadvantages 59

THEME 1.1.3 THEME 1.1.3 60 ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… Further InformationFurther on Resource the CD (x) (x) (ix) (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) of EIAs. objective main the Explain 6. 5. Eva Creek Wind Project, GVEA, 2013. GVEA, Project, Wind Eva Creek 2007.Th (EWEA), Association Wind Energy European Wind Energy, Economics of e Power, of Wind 2012. Analysis IRENA Cost 2015. (DEA), Aff of Environmental Department airs Projects. for Energy Renewable Guideline EIA 12/12/20/1701. ber: Reference DEA Num- Western Province, Cape Farm, Wind Caledon proposed for the EIA ment of Energy, 2013. U.S. Depart- (NREL), Laboratory Energy Renewable National Harmonization, LCA Wind ment of Energy, 2011. U.S. Depart- Project, Harmonization LCA (NREL) Laboratory Energy Renewable National of Energy, 2015. Department Africa, South in of Energy Renewable State 2011. Mitigation, Change Climate and Sources Energy Renewable Report: Special IPCC 2016 CSIR, Africa, for Study South Aggregation PV Resource Solar and Wind power! coal and wind between downstream) and operational (upstream, stages cycle of life cost the Compare Unit 1.2

UNIT 1.2 ECONOMIC AND ENVIRONMENTAL BENEFITS OF HYDROGEN FUEL CELL TECHNOLOGY AND E-MOBILITY

Introduction

Oil is still the main resource that fuels the world’s transport economy in the form of petroleum fuels. Similarly, South Africa‘s transport system depends on petroleum fuels, petrol and diesel for almost all of its energy needs in the transport sector and beyond. South Africa relies on imports of crude oil and refined fuels to meet its liquid fuel needs. Over 60% of products refined locally are produced from the imported crude oil and about 36% of the demand is met by coal-to-liquid (CTL) synthetic fuels as well as gas-to-liquid (GTL) synthetic fuels plus a very small amount of domestic crude oil. Given that these fossil fuels are finite and the largest source of greenhouse gas emissions, clean alternative fuels are required in the future. Hydrogen is such a fuel and can provide a range of energy services while emitting only water. Focussing more on the transport sector, a growing global mobility and thus energy demand faces limited availability of fossil resources. To achieve the internationally agreed climate targets, a drastic reduction in transport-related CO2 emissions is needed. Fuel cell and battery powered electric vehicles have the potential to do exactly this, also offering substantial potential for economic growth. There are clear indications that e-mobility is definitely up-and-coming and that is why we are now introducing you to the socio-economic and environmental benefits of hydrogen fuel cell technology and e-mobility. Unit Outcomes

At the end of this unit, you should be able to: (i) Provide an overview of the hydrogen economy and clarify the function of hydrogen and its use in fuel cells. (ii) Explain why South Africa possesses competitive advantages and challenges with regard to hydrogen and fuel cell technology. (iii) Explain the advantages of combining renewable energy technologies, such as PV and wind turbines, with hydrogen and fuel cell technology. (iv) List and describe the existing and potential applications of fuel cells. (v) Compile an overview of advantages and disadvantages of hydrogen and fuel cell technology. (vi) Compile an overview of advantages and disadvantages of e-mobility. Themes in this Unit

Unit 1.2 covers two themes: Theme 1.2.1 Hydrogen and Fuel Cell Technologies Theme 1.2.1 E-Mobility

61 THEME 1.2.1 62 tion. to Volta’s related batteries used inven- century 19th the in industry 1870s, and the generator science in advent dynamo/ of the the Until conductivity. to increase electrolyte as chloride), acted which sodium (usually asolution of i.e. salt brine, in soaked or cardboard by cloth (electrodes) separated discs zinc and fl electric on ‘animal scientist, uid’ (1791). copper alternating pairs of stacked of consisted pile e voltaic Italian Th another Galvani, of Luigi ideas the rejected he subsequently and chemically generated be could pile”, fi energy “voltaic invention the in this battery, 1799. thatelectrical With Volta proved electrical rst energy. He invented the apioneer and of electrical scientist Volta, Italian an Alessandro with start us Let (early of contemporaneous 1800s). kind and related development and thus is discovery of their ground back- historical the and processes electrochemical similar on fairly based are cells fuel and Batteries Fuel Chemistry and Cellsand aLittle Batteries: History ALittle Deﬁnition Terms of able you to: be should theme, end ofAt this the Outcomes Theme Keywords theme. this of bydiff anumber in driven investigate hydrogen subsequently is in Interest will we which erentfactors (FCEVs). vehicles electric cell fuel in for use distribution hydrogen and production safe and economical clean, towards working are initiatives several infancy, their in still are hydrogen markets Although future!” of the coal ble…. the be Water will not is capa- coal of which intensity of an light, of heat and source inexhaustible an furnish together, will or singly used it, constitute which oxygen hydrogen and that one employed be day fuel, as will water that WorldAround the (1870), (1873) Days Sea the Eighty in Under and “I believe then: back professed already Twenty Leagues ousand (1864), Earth of the Center tothe Journey including stories, adventure for his known best century, 19th Vernes, Jules the not is idea. anew aFrench in novelist fuel Using hydrogen as Introduction TECHNOLOGIES CELL FUEL AND HYDROGEN THEME 1.2.1 Advantages and disadvantages of fuel cell technology cell of fuel disadvantages and Advantages technologies renewable energy Combining advantages competitive Africa’s South Theconomy e hydrogen fuel alternative an Hydrogen as cells of fuel applications potential and Existing electrolysis reversing and Electrolysis batteries and Fuel cell (v) (v) (iv) (iii) (ii) (i) Compile an overview of advantages and disadvantages of hydrogen and fuel cell technology. cell of fuel hydrogen and disadvantages and of advantages overview an Compile cells. of fuel applications potential and existing the describe and List technology. cell fuel hydrogen and with bines, tur- wind PV and as such technologies, renewable energy of combining advantages the Explain technology. cell fuel and drogen to hy- regard with challenges and advantages competitive possesses Africa why South Explain cells. fuel in use of its hydrogen and function the hydrogen economyclarify of the and overview an Provide Ludwig Mond and Charles Langerand. Mond Charles Ludwig and in Thresearchers, two ‘gaslater battery’. 1889 by by Grovewas coined the termed as cell’ ‘fuel term e hydrogen. Th with ofwas oxygen that development the led to device ofa electrolysis reversing e ofidea reaction the from generate electricity and process electrolysis the to reverse possible be it should that reasoned scientist, judge and Grove, aBritish 1883, In William Carlisle. Anthony Nicholson and William Image source: GIZ/S4GJ source: Image FIGURE 1: FIGURE sis) components, hydrogen (H of two into water decomposition (electroly- Th the electrical including discoveries, of rapidpile series a enabled e voltaic Electrolysis and Reversing Electrolysis Your notes own Water COMPARISON OF ELECTROLYSIS AND REVERSE REVERSE AND ELECTROLYSIS OF COMPARISON ELECTROLYSIS OF WATER WATER OF ELECTROLYSIS Electrical energy Electrical Electrochemical reaction Hydrogen Oxygen 2 ) and oxygen (O oxygen ) and ( Oxygen SCHEMATIC Hydrogen 2 ), in 1800 by two British researchers, researchers, British by 1800 ), two in Electrical energy Electrical Electrochemical ) reaction Water 63

THEME 1.2.1 THEME 1.2.1 64 the battery is no longer able to transform chemical energy into electrical energy. electrical into energy chemical no longer is able to transform battery the consumed, are reactants (reactants). these When substances chemical stored in energy potential forming by trans- energy supply electrical and devices storage as function hand, other on the Batteries available. (hydrogen) fuel is its forlong as as operates cell afuel by-product batteries, only water. pure is the Unlike and emissions, no harmful are there of combustion, absence of the Because etc.) available. is methanol (hydrogen, water.fuel heat and Thas as long current, occurs reaction electrical an ces e electrochemical it produ- aresult, As oxygen. hydrogen combines (fuel) with that device electrochemical an is cell A fuel Fuel Alternative an as Hydrogen GIZ/S4GJ source: Image FUEL CELL APPLICATIONS IN CUTTING 2: RE U FIG technologies. cutting-edge in applications cell fuel using are civil, and military both moremany sectors, Today vehicles. launch reusable and vehicles air uninhabited airplanes, for spacesuits, produce electricity and of NASA applications variety awide in successfully now are used devices cell fuel and unabated continued has research cell fuel 1973. in then, Since crisis energy the development, did as further pushed NASA’s NASA’s in Programmes. Space used Apollo and 1960s and interest the improved in Gemini ficell (AFC). fuel the essence were in developed cells fuel thus and of hydroxide, types alkaline rst ese Th potassium alkali with electrolyte acid sulphuric the substituted gauze, nickel expensive less with trodes elec- platinum ofimplementedreplacing modifi anumber forexample design, the original to cations Thstory. Francis 1959 engineer, He cell In fuel the a British in major chapter the next wrote Bacon omas Existing and Potential Applications of Fuel Cells for regenerative energies regenerative for power supply Storage system Siemens Electrolyzer Space shuttle propulsion (PEM FC) Air-independent Air-independent Submarine TECHNOLOGIES (PEM FC) (PEM

(PEM FC) (PEM ( H SCHEMATIC 2 /O 2 Applications ) H 2 /air - EDGE noiseless operation (PEM FC) noiseless operation (PEM FC) efficient operation (PEMefficient FC) Emission-free and energy- Delivery trucks Delivery Passenger car Passenger Emission-free and Emission-free Emission-free and Emission-free Bus Image source: Shutterstock source: Image 4: FIGURE GIZ/S4GJ source: Image FUEL CELL OPERATION 3: E R U G FI Hydrogen FUEL CELL IN A LAB CONVERTING CHEMICAL ENERGY INTO INTO ENERGY CHEMICAL CONVERTING ALAB IN CELL FUEL CONCEPTIONAL ELECTRICAL ENERGY ELECTRICAL Energy Heat Oxygen ) Heat ( SCHEMATIC AND SIMPLIFIED (for reuse) hydrogen Excess Hydrogen H H H H H H H H 2 H H H H

Catalyst

Electric Anode power

Electrolyte Cathode H Catalyst H H 0 0 H 0 H H 0 H 0 0 2 0 0 0 0 0 H 0 Oxygen Water 65

THEME 1.2.1 THEME 1.2.1 66 Image source: Shutterstock source: Image 5: E R U G FI for development. economic opportunity an but also hydrogen achallenge is distribute store and to extract, required infrastructure the preparing Nevertheless, procedures. other and reforming by fuel substances hydrogen-bearing many from extracted be can systems cell fuel of the Hydrogen and/or for stored. most transported to be needs it also sometimes and produced, to be needs more effi times to three Hydrogentwo on gasoline. running engine combustion internal an cient than effi for high potential cell’s fuel the and tion, motor is electric an coupled with cell afuel ciency. fact, In produc- for domestic potential its vehicles, electric zero-emission in cells power fuel to directly ability due to its but also applications, high-tech for various fuel alternative consideredan Hydrogen thus is HYDROGEN AS ALTERNATIVE FUEL POWERS FUEL CELL CELL FUEL POWERS FUEL ALTERNATIVE AS HYDROGEN ELECTRIC CARS SUCH AS THE TOYOTA MIRAI TOYOTA THE AS SUCH CARS ELECTRIC given that steam reforming releases carbon dioxide (CO dioxide carbon releases reforming steam that given and based fuel fossil all are materials these Given that steam. fuel-rich and to agas-phase methanol, or gasoline but gas also natural mainly hydrocarbons, liquid fuel-based fossil change that to processes refers reforming Steam reforming. for steam hydrogen is production technology dominant the Currently S4GJ/GIZ source: Image FIGURE 6: FIGURE (H molecules free as Yet, exists hydrogen rarely things. living all and water, fuels in fossil where on Earth: found every- be hydrogen can bound chemically and element nature in abundant most Hydrogen the is Processes Production Hydrogen obtained from various sources, such as fossil fuels, nuclear energy and renewable energy sources. sources. renewable energy and energy nuclear fuels, fossil as such sources, various from obtained be can processes for these required raw materials and energy the and hydrogen available production cial Th intensive. energy is production its and hydrocarbons 6) manyfor commer- (Figure pathways are ere production pathways are known, such as: such known, are pathways production However, hydrogen hydrogen process. production more sustainable asustainable consideredas be cannot 2 (ii) (ii) (i) ) in nature. Instead, for technical use hydrogen has to be extracted from resources such as water or water as such resources from extracted to be hydrogen has use for technical Instead, nature. ) in Energy Resource Organic waste Organic Geothermal Natural gas Natural ucts that can then be separated or to reformed hydrogen. separated be then can that ucts conversion Biomass costs. impact additional non-renewable is causes which and to gasoline, compared hydrogen costly production effi higher its Even considering when refi high the make cells, costs fuel in nery fuel as ciency effi of to hydrogen. produce 1kg energy of kWh electrical 50 around require cient electrolysers ahuge be factor, and hydrogen can (>99.999%). facility electrolysis for However, an costs capital purity high of producing capable it is that is of electrolysis One advantage renewable sources. Electrolysis Crude oil Crude Biomass Nuclear Nuclear Hydro Wood Wave Wind Solar Coal OVERVIEW OF HYDROGEN PRODUCTION PATHWAYS PATHWAYS PRODUCTION HYDROGEN OF OVERVIEW ( SIMPLIFIED , i.e. splitting water into hydrogen and oxygen using electricity from one of the many many one from of the electricity using oxygen hydrogen into water and splitting , i.e. via either thermochemical or biochemical conversion to intermediate prod- conversion to intermediate or biochemical thermochemical either via Electric power plant Electric power plant ) Generator Generator Generator Generator Processes Reformer Reformer Reformer Reformer Reformer Reformer 2 ) as a by-product to the atmosphere, reforming aby-productreforming ) as atmosphere, to the Electrolyser Hydrogen Product 67

THEME 1.2.1 THEME 1.2.1 68 Image source: S4GJ/GIZ source: Image 8: RE FIGU S4GJ/GIZ source: Image 7: E R U G I F Figure 8 illustrates non-sustainable and sustainable hydrogen production techniques. hydrogen techniques. production sustainable and non-sustainable 8illustrates Figure while hydrogen options production sustainable various of the overview an 7provides Figure available. commercially them to see expect we might which order in chronological the roughly thus and pathways, these of Th maturity technological the represents also above mentioned technologies the e order of (iv) (iv) (iii) Reformation s i s y Photolysis l o tion. m r e Thermolysis OVERVIEW OF SUSTAINABLE HYDROGEN PRODUCTION PRODUCTION HYDROGEN SUSTAINABLE OF OVERVIEW ILLUSTRATION OF NON Methane Heat CH PATHWAYS HYDROGEN PRODUCTION TECHNIQUES 4 , using photons in biological or electrochemical systems to produce hydrogen directly. to produce hydrogen directly. systems or electrochemical photons biological in , using CO , using solar-generated heat for high temperature chemical cycle hydrogen produc- cycle chemical temperature heat for high solar-generated , using Mechanical energy 2 Reformer ( SIMPLIFIED Electrolysis Electricity Renewable energy Hydrogen H - ) SUSTAINABLE AND SUSTAINABLE 2 Electrolysis Conversion Biomass trolysis Elec- Water Grid Photolysis Wind farm Wind Wind prospect of developing new industries. ofnew developing prospect additional the is there that Thmeans sources. systems new energy these develop to required investment e effi and aclean to create opportunity energy unique primary on sustainable based system cient energy may off converters energy cell fuel with together hydrogen er a fuel, characteristics, water. Given these only emitting while services of energy arange provide Hydrogen renewable. can and local carbon-free, are which sources from energy be to produced potential Ththe has hydrogen because arise attributes ese but compressing a gas will require energy to power the compressor. to power the energy require will but agas compressing volume, per density energy improve would the pressure hydrogen gas Increasing for storage. tanks larger requires Hydrogen thus to hydrocarbons. volume compared per density energy poor it has weight, per Th technology. density current energy good has gas albeit with hydrogen that is this transport reason for e to store or expensive hydrogen quite is hydrocarbons, fuel fossil other and to oil Compared conditions. market current not under power is cheap back to hydrogen and converting that is storage energy for grid power. wind Th like diffi sources, for storage renewable energy ergy primary e using hydrogen with culty en- role of hydrogen to the grid to provide given been has Some attention much but production, storage. Th carrier’. ‘energy hydrogen as economy a implementing in ishydrogen so not limitation key current e through uses multiple Th toend linked sources energy economy e primary ofnetwork isahydrogen 1980’s. the in advances technological with and crisis 1970’s oil the with the in heightened 1950’s. the fuel avehicle hydrogen as in (50% Interest gas until hydrogen) UK the in town as e.g. domestically, and industrially both used not is new. been system previously Hydrogen has Th fuels. fossil than of hydrogen an energy rather use as on the using hydrogen e concept of based try, ofa coun- requirements the energy supporting Thinfrastructure economy’the ‘hydrogen refers to term e HydrogenThe Economy GIZ/S4GJ source: Image FIGURE 9: FIGURE including: of bydiff anumber driven hydrogen subsequently is orin to store Interest it. to another erentfactors, one from place energy chemical to carry used be hydrogen can fuels, to fossil Similar carrier’. ‘energy or 'energyvector' but an source energy hydrogen not is an that see already we above, can From the Hydrogen as an Energy Vector (v) (v) (iv) (iii) (ii) (i) (i) Primary energy Primary source High effiHigh technologies cell fuel new with conjunction in ciencies quality Improvement air of local Diversifi fuels on dependence fossil reducing supplies, cation of energy imports of energy Reduction Reduction of CO Reduction HYDROGEN IS AN ‘ENERGY VECTOR’ OR ‘ENERGY CARRIER’ OR ‘ENERGY VECTOR’ ‘ENERGY AN IS HYDROGEN Primary energy Primary transmission 2 emissions, thus helping to mitigate climate change change climate to helping mitigate thus emissions, Water generation Hydrogen Electrolyser Oxygen Hydrogen infrastructure Hydrogen Hydrogen storage refuelling Hydrogen End use End Potential market H applications Hydrogen bus 2 69

THEME 1.2.1 THEME 1.2.1 70 your lifetime. lifetime. your in see still youeven may well that areality become hydrogen economy the will reduced, hydrogen are of storing and for transporting generation, costs current the and resolved, are cells fuel hydrogen and of signifi most the commercialisation the for as soon hydrogen. As to drivers main barriers cant two the site offthe powerrefi to technologies cell fuel only using in andcomplex Springs. nery -grid entire the of taking aim ultimate the hydrogen, with uses power that plant cell fuel a1.2 MW as well as source afuel as gas natural uses power that plant cell fuel 8MW an install to further plans Implats burg. refi metals of Johannes- east base km some and 35 in Springs, platinum at its station nery gen refuelling powered forklift cell fuel including and a hydro- s initiative (Implats) an launched Platinum for example Impala incentive. tax Treasury’s R&D the development with and (R&D) accordance research in spend i.e. to benefi for mines incentives investments, creating 2016cell fuel In governmentfrom started platinum t applications. key deployment in local by encouraging industry local aviable creating and opportunities commercialisation on investigating but also research, direct and funding continued on not depend only will opportunity this to seize infrastructure and skills knowledge, the er, creating Howev- participation. industry for global opportunities valuable to provide likely are that innovation Th cell fuel elements of Africa. South addresses in strategy technologies HySA e cell fuel hydrogen and of chain value the along innovation guides and stimulates strategy the (HySA) 2008, in Africa South Hydrogen as Branded services. ancillary and integration, systems for manufacturing, opportunities with deployment hub, cell afuel as itself position could country the Africa, South found in reserves PGM over 75% world’s with of the and known cells fuel most in used materials catalytic key er. the are PGMs (PGM) produc- metal group amajor platinum as industry cell fuel the in participate could Africa South Africa’sSouth Advantages Competitive Cells Fuel and Hydrogen (2015), Roadmap IEA Technology Sources: 2020 AND FLEET TARGETS FCEV EXISTING 2: TABLE Cells Fuel and Hydrogen (2015), Roadmap IEA Technology Sources: REFUELLING HYDROGEN PUBLIC EXISTING OF NUMBER 1: TABLE hydrogen. However, CO reducing transport and to store ways have not easy and developed renewables hydrogen from production have no dedicated they as potential, this realising from far are moment At the countries most electrolysis. power driven wind through e.g. technologies, hydrogen produced by is renewable energy where the source, fuel future the as on hydrogen economy based for a worldwide transportation potential real is there considered, things All United States Korea Japan Europe region or Country United States Korea Japan Europe Country or region or Country STATIONS AND 2020 TARGETS 2020 AND TARGETS STATIONS 2015) (before road the on FCEVs >50 >50 >100 >100 (2015) stations refuelling Existing 2 100 146 102 192 emissions and improving security of energy supply are supply are of energy security improving and emissions (2020) road the on FCEVs Planned >100 >200 >200 >400 (2020) stations Planned ~350 000 100 000 ~20 000 50 000 Th advantages e following andAdvantages Disadvantages of Hydrogen and Fuel Cell Technology providers, car manufacturers, and local, regional and national authorities. authorities. national and regional local, and manufacturers, car providers, power grid and utilities industries, relevant as such stakeholders, many among collaboration upon close hinges for infrastructure, to investments related mainly roadmap, lenges for ahydrogen technology However, countries. chal- overcoming these in exist already stations of hydrogen refuelling hundreds that given opportunity, on this to capitalise position aunique in thus are Europe and U.S., Japan, i.e. developments. Th to hydrogen infrastructure early adopters, respect e in progress reasonable very made someandcountries exists signifiimpediment absoluteno require Nonetheless, investment. capital cant would distribution and for hydrogen transport production, infrastructure necessary the Establishing for FCEVs. for fuel hydrogen demand as little too is there because stations no hydrogen are fuelling there but stations, no hydrogen no FCEVs are fuelling are problem, there there i.e. because chicken‐and‐egg classic the resembles However, challenge vehicles. this electric cell of fuel for introduction obstacle gest Th thebig- as been hasconsidered oflong hydrogen lack infrastructure. one e latter the is important themost far but by technologies, Thcell fuel adoption of widespread limiting issues number of are a ere Th disadvantages e following (vi) (vi) (v) (iv) (iii) (ii) (i) medium-sized power utility. power utility. medium-sized of a range megawatt to the appliances for small range watt the from realised, be easily fore very there- up can Scaling area. active the and cells of elementary number the by changing simply adapted be can size Fuel cell reservoir. fuel by the determined and capacity, and size cell fuel the by power, between determined scaling independent allow Fuel cells and exibility: Modularity applications. for portable especially feature interesting an is which compactness, good thus and batteries, to compared offcapacity Fuel cells storage Compactness: higher and density energy higher er industrial. and i.e. automotive, residential debate, change fi climate several international the with concerned elds optionin arealistic are cells fuel footprint, low environmental to their Due on hydrocarbons. world’s to the contribute end of dependence can and goals reduction carbon achieving in sential are es- most probably Th cells of Fuel GHGgies. reduction. perspective the from asset key is a is technolo- renewable energy various including of sources, avariety produced from be can which Sustainability: equipment. ancillary of the pieces Th are moderate noise areas. liablecause to are residential that parts only e for suitable them making systems silent relatively are Fuel cells work. maintenance ly reduced Th ideal. potential- and noise less to mechanically close is means thus state, solid SOFC) all are (PEMFC, cells of fuel types Certain parts. or moving even no rotating have practically systems Fuel cells available/supplied. of fuel amount to the proportional directly and well‐known is time Th to depletion. replenishment fuel from performance peak aterefore constant operate operation Th eventually). have (and replaced to be recharge they for time‐consuming in plugged ey to be have batteries while by refuelling, afew minutes within everywhere recharged be can Fuel cells batteries. acid lead than ranges temperature operating over wider performance more predictable of power Th outage. risk any power without quality high provide have ey Fuel cells grid. of the to or independent power parallel base acontinuous maintain can they since grid electric to the continuity and help stability provide can Fuel cells quietness: and low maintenance Reliability, technologies. renewable by ered pow- hydrogen produced by electrolysis is water the if and fuel as hydrogen used compressed is if GHG near‐zero emissions with technologies energy clean are Fuel cells emissions: Reduced eﬃ ones. larger cient as suff that as are turbines gas and eff devices engines fromscale cell fuel er small example, ects for : combustion fi Unlike not depend on size. it does because y systems drop notfor small does ciency c more 2‐3eﬃ are times cells fuel n ef- cell fuel for ICEs Interestingly, propulsion. vehicle cient than e energy, intoelectrical Th energy (ICE)conversion i batteries. and chemical of direct the to anks c E Fuel cells combine many of the advantages of both internal combustion engines engines combustion internal of both advantages of the many combine Fuel cells Fuel cells can be powered by hydrogen, the most abundant element on Earth element on Earth powered abundant be most by hydrogen, the can Fuel cells are known: are are known: are 71

THEME 1.2.1 THEME 1.2.1 72 ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… applications! cell fuel main the List 2. 1. Exercises 5. 5. briefl and operates! cell diagram fuel how aschematic Draw a explain y 4. ……………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… 3. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… Describe electrolysis and reversing electrolysis! Mention similarities and diff and Mention similarities erences! electrolysis! reversing and electrolysis Describe Draw a diagram that gives an overview of the various hydrogen pathways! production various of the overview an gives that adiagram Draw fuel? alternative an hydrogen is consideredas Why ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… orcarrier’! ‘energy vector’ ‘energy why hydrogen consideredan is Explain 6. Further InformationFurther on Resource the CD 7. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) List the advantages and disadvantages of hydrogen and fuel cell technology. cell of fuel hydrogen and disadvantages and advantages the List Technology Roadmap, Hydrogen and Fuel Cells, International Energy Agency (IEA), 2015 Agency Energy International Technology Fuel HydrogenCells, Roadmap, and of Energy, 2015 2013, AND Department 2002 BETWEEN AFRICA SOUTH IN MARKET, OFOVERVIEW DIESEL PETROL AND nology’s (DST), 2010 Tech- and of Science Department Africa, South in technologies cell fuel and HYDROGEN 2009 Fuel Partnership, & Freedom CAR Future, Technology to the Roadmap, Pathways Hydrogen Production (2015),IEA Fuel HydrogenCells Technology and Roadmap Vehicles: Th Electric Fuel Cell Cell Fuel Ahead, Today, eRoad 2013 2014 Jones &Botha, Africa, South in Industry cell fuel the Accelerating Yard Naval Kiel at German Submarine Hydrogen Fuel Cell Class -Dolphin Video: 4K

THEME 1.2.1 Your own notes NOTES

74 At the end of this theme, you should be able you to: be should theme, end ofAt this the Outcomes Theme and e-bikes. Th e-bikes. and car confi three electric are: gurations we e refer to diff to three refer mainly vehicles confi erentcar electric textbook, this gurations In cars. electric up to full engines combustion internal Th with from hybridplug-invehicles isa continuum, cars range of electric e Vehicles Electric costs. for lower demands operational market as well as requirements, emission and effeﬃ fuel E-mobility hydrogenconvert electricity. into address to the need by are motivated orts ciency that (FCEV) vehicles electric cell fuel as plug-inwell (PHEV), (BEV) as and hybrids vehicles electric ered battery-pow- include technologies powertrain trucks, and buses cars, on passenger Focussing shuttles. and evenand planes forklift ships trucks, trains, s, buses, cars, passenger e-bikes/pedelecs, including cles, propulsion of vehi- electric to enable the technologies various of concept using the represents E-mobility Electro-Mobility Deﬁnition Terms of Keywords theme. this in it to youare why introducing is nowthat we and defiAfrica South to coming also nitely is Development E-mobility Plan. E-Mobility National of Germany’s bold aim the is this byroad 2020, on the vehicles electric One million vision. mobility of long-term its zero-emission part as by 2020 bility mo- for provider electric and market lead the of becoming goal the itself set has for example Germany targets. mobility have electric also United States the and Germany, Norway, Netherlands France, the by 2020. vehicles energy alternative of 5million atarget set has and vehicles ment of alternative-energy Th generations. future the government off forexample, China in deploy- us, the for incentives various ers for of mobility freedom powered or plug-in guarantee hybrids battery-electric vehicles, electric Smart Introduction E 1.2.2 THEME - Advantages and disadvantages of e-mobility disadvantages and Advantages Your fie-bike! an be could EV rst of BEVsRange for e-mobility requirements infrastructure Charging (EMTIP) Programme Technology Innovation uYilo E-Mobility vehicles Electric Electro-mobility (iii) (ii) (i) (iii) (ii) (i) MOBILITY Compile an overview of the advantages and disadvantages of e-mobility. disadvantages and advantages of the overview an Compile for e-mobility. requirements infrastructure the Explain Defiterms. e-mobility ne the wheels directly. wheels the and/or drive batteries their to recharge on board or backup extender arange as engine bustion com- afi via internal an have batteries also power their supply. cars charge electric these xed But and of energy source primary the as bank abattery use Plug-in (PHEV), which vehicles hybrid (FCEV). vehicles electric Hydrogen-powered cell fuel it afi into bypower. plugging on-board charged power xed supply, no auxiliary with Vehicle (FEV), Electric Full to as referred sometimes (BEV), vehicle also powered electric Battery 75

THEME 1.2.2 THEME 1.2.2 76 Image Source: D. Boxberg/ GIZ D. Boxberg/ Source: Image 2: RE U FIG create’. ‘to means and isiXhosa Th connectivity. componentssmart and from name train derived is e drive uYilo electric technology, tery bat- standardisation, local networks, deficharging grids, into smart generation by ned energy renewable afi as (TIA) programme. innovation e-mobility multi-stakeholder istowards national focus e ve year Th Th vehicles. Innovation Agency the by how electric initiated to support Technology was e programme know- the generating and opportunities business new by creating of e-mobility introduction forca the Afri- ThSouth ready to seeks (NMMU) University MandelaMetropolitan EMTIP, the e Nelson at hosted uYilo E-Mobility Technology Innovation Programme (EMTIP) S4GJ/GIZ source: Image 1: FIGURE (FCEV) vehicle Fuel cell electric ICE powertrain

COMPONENT CONFIGURATIONS IN THE THREE DIFFERENT DIFFERENT THREE THE IN CONFIGURATIONS COMPONENT EV U YILO’S DC FAST CHARGING FACILITY CHARGING FAST DC YILO’S - TYPES Tank BOP FC stack Power battery electronics Power E-motor Transmission Transmission (BEV) vehicle electric Battery Electric powertrain Electric Plug-in-charger Energy battery electronics Power E-motor Transmission Gene- Tank rator vehicle (PHEV) vehicle Plug-in hybrid electric ICE Battery FC powertrain Plug-in-charger bat Energy electronics Power E-motor Transmission tery major automakers have joined forces in a bid to develop Europe’s most powerful network of electric car car of electric network abid have forces to developmajor in Europe’s joined automakers powerful most adoption of EVs. mass world’s of Four the facilitating in assist and issues these address could points charging located strategically and powerful adoption of BEVs. with network public Alarge large-scale (BEVs), to vehicles major one consideredto be barriers electric of is the concern reference to battery this insuﬃ has avehicle that fear the is with anxiety Range Particularly destination. its to reach cient range S4GJ/GIZ source: Image FI G U R E 3: E R U G FI as: such considered, to be need which diff are there and times charging of erent longeraspects face charging pump. drivers EV averagefuel at the 10 to fi minutes than less andpay for gasoline It takes some concerns. tank ll are up a infrastructures ing of suﬃ of EVs range availability the and limited the times, charging Long cient recharg- challenges. several poses to e-mobility mobility Th engine-based combustion internal from conventional switch desired e E-Mobility for Requirements Charging Infrastructure (v) (v) (iv) (iii) (ii) (i) 40 to 60 minutes. to 60 40 in charge battery about 80% deliver chargers above fast of the All model. Combo SAE the use ers Tesla’sare (see network Supercharger below), manufactur- other Nissan’s while model, CHAdeMO examples known best the and 3charging Level as charging Some refer to this Charging: Fast DC station. at home or at charging apublic of hour charging an in of range km 30 around add can Drivers ampere. up to 30 EVSE Vand power to provide Vor an Uses 240 at 220 2Charging: Level to charge. night have all and aday km 60 than less workwho travel for it those can impressive, at not all sound does this household (120 Th outlet. astandard V) and While per hour.range km up to 8 provides setup is Th charger 1Charging: the on-board Level to a Uses to connect plug e slowestcharging. of form AC relaysimply the safely. vehicle power to the Its role to is or up on apedestal. on mounted awall typically is and port, vehicle’s the and charging apower source between equipment'. intermediary It the service is vehicle for 'electric EVSE: Stands (see off below) own its uses Charging charger. -board (BEVs) vehicles electric (PHEVs). vehicles kW 3.3 on battery and on plug-in electric hybrid Fast DC 6.6 Th vehicle. are kW the chargers in vary, common themost on-board but may speed charging e battery the charges power to DC that AC It wall converts power the from factory-installed. comes 3) Figure(see charging Level 2 and Level 1 Th for device charger: On-board charging actual e TESLA’S SUPERCHARGER CHARGING PROFILE BASED ON BASED PROFILE CHARGING SUPERCHARGER TESLA’S 90 KWH MODELS 80% 40 minutes40 100% 75 minutes 77

THEME 1.2.2 THEME 1.2.2 78 behaviour. on mobility impact ahigh guarantees share market rising rapidly the required, is infrastructure other oﬃ the in sweaty and tired to arrive do not want they when them no that big advantage the With ce. older or age use in them use areas, or mountainous even hilly in them use bicycle, anormal with than further 50% around people tend to drive as trips, car urban replacing are e-bikes that evidence growing Th China. more even in and annually Europe is soldere in are e-bikes amillion Over Europe. and China in markets conquering quickly are or e-bikes pedelecs yet, Africa South in common not very Albeit Your could First EV bean E-Bike! Shutterstock source: Image 4: FIGURE sold worldwide: cars for some of electric BEVs averagerange list the indicates signifi may also coldin Range weather. be reduced vehicles. engine cantly combustion al following e Th of tradition- range do on the they as just impact have an also driver of the demands performance the and used. Th type of batteries vehicletype of and number and the Th range on weight e depends ofa BEV e Range adoption of EVs. mass facilitate rapidly hope will manufacturers car ble; abid European carfeasi- electric ina battery travel make Thlong-range is to network European new the aim of e overall Europe. across points charging 4703 individual of 3) 744 containing (Figure consists sites and minutes 75 in cars by its Tesla. owned 120 kW network charge Tesla’s supercharger current fully can network the triple signifi almost in times. will cars shorter their in cantly batteries initiative the is to replenish Th points charging of 350 individual thousands kW into plug can Thdrivers 2020. car thatelectric is means by Europe in sites charging 400 build to jointly of Understanding Group aMemorandum have signed 2017 VW from Ford the BMW, and onwards. Benz/Daimler, Mercedes installed to be points charging (iv) (iv) (iii) (ii) (i) range in the European driving cycle. cycle. driving European the in range of km 300 around sedan small the giving kWh, to 40 battery of the size the increased it has that recently in announced Europe 2015. in Renault car Th electric bestselling the was Zoe Renault e range ofkm. has a 170 Th kWh 30battery year 2016model with Leaf Nissan bestseller e of 180 arange km. has 2017 a33 in battery kWh BMW’s with available i3, new 2014. since built Th of 470 arange km. motors has dual and been battery kWh Teslahas 90 is model ModelSwith A TYPICAL E ATYPICAL - BIKE WITH REAR HUB CONFIGURATIONS HUB REAR WITH BIKE ral riding sensation than hub motors. than sensation riding ral amore of create ahub natu- and instead train bike’s power the drive arrangements Mid-drive riders. bike forconventional hub confi more Rear natural feels which tire forward. theback spin ‘pulled’ is gurations bike the that sensation the create and front wheel Front the hub motors propulsion provide by spinning S4GJ/GIZ source: Image 6: FIGURE at 25 km/h. set usually is limit Union this European the out. In cuts usually motor assistance the limit, speed At acertain of assistance. deal to agreat all motor. at Th electric to the assistance data from no ranges calculated the assistance sends amount of e ultimately and data pedalling the handles computer that chip advanced an power and of human amount the measures torque which (motion sensor sensing) pedal advanced an including circuitry, electronic an Th i.e. Europe. in controlon a mechanism, of some countries based is due to regulation function is off weredeveloped turn Pedelecs the brake. or automatically press motor will when youstoppedalling Th wind. tail constant with e battery-powered cycling feel like you will and easy really pedalling make will It Th pedal. whenonly come you on will pedalling. assistance motor you when start e electric ically automat- works assist Pedal pedalled. be must that bicycles work? electric How are Pedelecs do pedelecs S4GJ/GIZ source: Image FI G U R E 5: E R U G FI Overall power Overall Human power Human Front hub RATIOS OF ELECTRIC MOTOR ASSISTANCE IN A PEDELEC APEDELEC IN ASSISTANCE MOTOR ELECTRIC OF RATIOS DIFFERENT ELECTRIC MOTOR CONFIGURATIONS OF E OF CONFIGURATIONS MOTOR ELECTRIC DIFFERENT FOLLOWING EU REGULATIONS Rear hub Rear 25 km/h Mid-drive Speed - BIKES 79

THEME 1.2.2 THEME 1.2.2 80 Ships. of energy. source Th its hydrogen as with Cell propulsion and for Fuel stands cell FCS fuel terminology e fi the world offset was in to ship passenger inland Alsterwasser FCS rst the under 2008, August In Germany. Hamburg, in becomereality a has Themissions pollutant without sailing vision ship ofa e ZEM-Ships Vehicles FutureZero-Emission (ZEM) infrastructures. of recharging availability the and of vehicles speed and range the technologies, new of usability and acceptance aspects, safety road cost, and life battery values, residual and costs purchase adoption of for EVs rapid mass high relatively Impediments are models. FCEV BEV new and launching on of haveoff models anumber already automotive manufacturers continuously are e-mobility.and All er eﬃ promote which incentives and of strategies range have awide states member many and cient strategy Th to pursue. policies and energy- promoted Union clean its ofsubsequently European part e as EVs promising one of more as the and seen thus is E-mobility transport. for decarbonising portunity vehicle commercial a majorop- Electrifiandparticularly provides eets cars fl cation owned of privately andAdvantages Disadvantages of E-Mobility and (BEVs FCEVs) up. charged battery the keeping or for extension for range engine combustion internal auxiliary power, havein an or not they whether rely on plug- motor which and To electric (EVs) powered vehicles an use conclude, electric that those are S4GJ/GIZ source: Image 7: E R U G I F PV SHADE CANOPIES WITH INTEGRATED PUBLIC SEATING SEATING PUBLIC INTEGRATED WITH CANOPIES SHADE PV AND E AND - BIKE CHARGING DOCKS CHARGING BIKE ger aircraft to continue will future. the conventional propulsionforeseeable for using y fl However, emissions. zero specifi dueHY4, to the the passen- in larger of used hydrogen density cenergy generating while operate aircraft the theoretically technologies, can renewable energy using electrolysis take-off HY4via the power during the is loads generated hydrogen If coversuses peak ascent. that and battery alithium energy, and electrical into hydrogen directly converts that cell hydrogen fuel perature alow-tem- of system, ahydrogen storage consists Its power train powered cell. solely by ahydrogen fuel the is plane Thtwin-fuselage aircraft the offour-seater rst Engineering fi in theermodynamics, world Institute Germany’s by DLR Germany. Developed primarily offAirport, taking at Stuttgart andlanding aircraft 2016, 30, hydrogen-powered September On the experimental HY4 made its rst fi cial oﬃ ight, fl ZEM-Aircrafts undetectable. virtually and quiet extremely vibration-free, Th heat. exhaust said be to little also is with system and e surfacing without weeks merged for up to three sub- staying for slow silent cruising, system AIP to the power or switch on diesel speed at high operate Th cells. hydrogen compressed fuel propulsioncan (AIP) using air-independent system submarines e additional an propulsion and diesel feature which submarines use and design navies several Further, berthed. while gases noxious not any emit does that avessel of being distinction unique holds the ship carrier Thcar the moored. while even whensea, at ship zero-emission times, a at all ship not totally ough help to power which the batteries lithium-ion with along PV panels incorporates seas, high the sailing already is which Ace” “Emerald ship cargo the Mitsubishi, conglomerate Japanese by the Constructed presented. been has ship feeder for acontainer design asimilar design) and ship (Wärtsilä’s Norway in developed have been concepts ferry Other port. in procedures and weight ship shape, propeller lines, hull byduced optimised re- are Total needs demand. energy for peak batteries stored in is electricity on-board Excess turbines. wind from electricity Th propulsion. excess using electric the ports near be obtained e could hydrogen Th designed. been the has for cells Denmark fuel by liquid converted on hydrogen based is e propulsion Rødby, with “Vogelfl Germany forPuttgarden, Scandlines’ ferry A zero-emission linking uglinie”, S4GJ/GIZ source: Image FIGU RE 8: RE FIGU Propulsion motor 100 kW 100 SCHEMATIC DRAWING OF THE FIRST ZEM INLAND INLAND ZEM FIRST THE OF DRAWING SCHEMATIC PASSENGER SHIP FCS ALSTERWASSER Energy management & battery Hybrid system Proton motor, each 2 fuel cell systems cell 2 fuel 50 kW 50 Hydrogen storage 350 bar 350 tanks Bow thruster Bow 20 kW 20 el 81

THEME 1.2.2 THEME 1.2.2 82 2. Prepare a schematic drawing outlining the component the confidiff outlining three of drawing gurations aschematic Prepare erent EV- 2. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… 1. Exercises ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… 5. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… adoption of EVs? on rapid mass impede could factors Which 4. ……………………………………………………………………………………… 3. types, i.e. BEV, i.e. PHEV. and FCEV types, concept! this under falling vehicles the list and concept e-mobility the Explain Explain the three charging options for EVs and outline their diff for options EVs their outline charging and three erences! the Explain uYilo the programme? hosting is university Which 6. Prepare a schematic drawing indicating the three diff erent electric motor confi gurations of e-bikes! THEME1.2.2

7. Explain electric motor assistance in pedelecs!

Further Information on the Resource CD

(i) Video: 2017 Chevrolet Bolt EV Animation (ii) Video: BMW i3 Electric Car (iii) Video: TOYOTA Fuel cell - How does it work (iv) AnimationElectromobility in Germany: Vision 2020 and Beyond, gtai 2016. (v) TOWARDS E-MOBILITY: THE CHALLENGES AHEAD, Fédération Internationale de l’Automobile (FIA), 2011. (vi) Zero-Emission Ferry Concept for Scandlines, 2013 (vii) Fuel Cell Systems for Zero Emission Ships: Experience from Regular Line Operation, 2010

83 Your own notes NOTES

84 TOPIC

Basic Scientiﬁ c Principles and Concepts

Topic Overview

We now introduce you to the basic underlying principles of wind power, batteries and fuel cell technologies. The latter two technologies are both based on electrochemical principles, while the ﬁ rst technology is based on kinetic and electrical energy and the laws of electromagnetism. All three technologies have energy conversion in common and we will clarify the basic principles of electrochemical and wind power in the following units. Lastly, we will introduce you to the concept of e-mobility, as well as give you an eco-car market overview and presentation of a typical e-car drive chain, including key components and their functionality.

Topic 2 covers the following units: Unit 2.1 Basic Principles of Wind Power Generation Unit 2.2 Basic Principles of Battery and Fuel Cell Technologies Unit 2.3 Basic Principles of E-Mobility

85 86 Unit 2.1 Unit 2.1 covers the following four themes: four Unit following 2.1 covers the Themes in this Unit able you to: be should unit, end ofAt this the Unit Outcomes generation. power wind of thebasic principles explains briefly unit this and challenges faces however also energy Wind construction. initial after costs maintenance and low have relatively operational also water. turbines Wind not consume does and pollutants or air emissions carbon direct not powerenergy. cause Wind does generation renewableof form and aclean it is that is of wind Amajor advantage power supply mix. global of the part tant impor increasingly an becoming is energy energy. Wind electric into energy kinetic to convert used commonly most are water, turbines pumping and but wind today grain for milling used power was Traditionally, wind Introduction BA 2.1 UNIT (xii) (xi) (x) (ix) (viii) (vii) (vi) (v) (iv) Theme 2.1.4Theme Wind Turbine Types Functions Wind their Componentsand 2.1.3 Theme Essential Turbine 2.1.2Theme Wind Power Factors 2.1.1Theme Wind? Causes What (iii) (ii) (i) SIC PRINCIPLES OF WIND POWER GENERATION POWER WIND OF PRINCIPLES SIC

Me Me Id low and tension power lines. high- and switchgears voltage high and medium transformers, ing Ex Di Ex De functions. different Il De De Ex Ex lustrate by means of a sketch the inside of a larger wind turbine and explain the components’ the explain and turbine wind of a larger inside the of asketch by means lustrate entify training kit components or small-scale industrial components. industrial components or small-scale kit training entify fferentiate between the different wind turbine technologies and designs. and technologies turbine wind different the between fferentiate plain the most important arrangements required to connect wind turbines to the grid, includ- grid, to the turbines wind to connect required arrangements important most the plain plain why wind turbines are usually set up on apole set or tower. usually are turbines why wind plain plain wind as a type of kinetic energy and ultimately as a form of solar energy. of aform solar as ultimately and energy of kinetic atype as wind plain wind. causes what plain scribe the purpose and principle function of generator. aDC function principle and purpose the scribe holds. energy wind potential enormous the scribe scribe the principle of energy conversion. of energy principle the scribe asure wind speed using a wind machine. awind using speed wind asure environment. the in speed wind asure

- THEME 2.1.1 WHAT CAUSES WIND?

Introduction

Wind is an ever-present phenomenon. We experience wind every day as a pleasant air scent, as a light breeze or even as a storm. We usually do not really think about what wind is or what causes wind. In this theme we will thus try to explain what exactly wind is. THEME 2.1.1 Keywords

What is wind? What causes wind? Pressure gradient force Wind direction Wind speed

Theme Outcomes

At the end of this theme you should be able to: (i) Explain what wind is and what causes wind. (ii) Perform an experiment and observe how changes in air temperature can cause convection currents.

Deﬁ nition of Terms What is Wind? Wind is air in motion! Air is a mixture of several gases, mainly nitrogen (78%) and oxygen (21%). It is thus a matter and has mass and weight. We usually perceive air as invisible and odourless, and to us air oft en may not seem like anything at all. In fact we look right through it all the time – it is only during a storm that air really makes its presence known. Winds are not only able to move sailing boats and wind turbine rotors; strong winds are also able to lift roofs off buildings, blow down power lines and uproot trees. Th us wind, being air in motion, can be considered as a force due to the fact that it is able to alter the motion of objects (see student book Renewable Energy Technologies (RET) NQF Level 2 for force, mass and acceleration, F = m x a). You might also recall that we cannot see forces, but we can see or feel their eff ects. Wind is a very good example for this statement.

87 FIGURE 1: A ROTOR SPINNING FAST IN STRONG WIND THEME 2.1.1

Image source: S4GJ/GIZ Wind is air in motion and can be a force! An image of late evening light creating a shadow of the rotor blades and the wind vane in the swept rotor area of a small 1kW wind turbine located at Port Elizabeth TVET college.

What Causes Wind? Wind is caused by solar radiation that is absorbed diff erentially by the Earth’s surfaces and is converted through convective processes due to temperature and air pressure diff erences. We dealt with temperature diff erences and convection currents in student book RET Level 3, but the explanation above, by making reference to a number of diff erent factors is probably diﬃ cult to understand. Let us thus try to explain the processes that result in wind step by step.

During the day the Sun’s rays (radiation) heat up the Earth’s surfaces. Land and sea surfaces heat up diff erently. For example, radiation heats the air above the land faster than the air above the sea. Now the following can happen:

1. Warm air, being less dense and thus lighter than cold air rises upwards. As the air rises, it creates low atmospheric (air) pressure. 2. Air masses on surfaces with cooler temperatures sink down. Th e sinking creates higher atmospheric pressure. 3. When warm air rises (low air pressure), cooler air will move in (high air pressure) to replace the rising warm air. 4. Th us wind, being air in motion, oft en moves from areas where it is colder to areas where it is warmer. 5. Th e greater the diff erence between the high and low air pressure zones or the shorter the distance between the high and low pressure zones, the faster wind will blow.

88 FIG U RE 2: DIRECTIONS OF SEA AND LAND BREEZES ALONG THE COAST

Day Night

Cool air sinks Cool air sinks Warm air Warm air rises rises

Cool air repla- Cool air replaces warm air ces warm air Warmer land Cooler land

Cooler sea Warmer sea THEME 2.1.1

Sea breezes caused by convection currents

Image source: S4GJ/GIZ Th e image shows directions of sea and land breezes along the coast caused by convection currents. A sea breeze describes a wind that blows from the ocean inland towards land. At night, the roles will usually reverse and wind will blow from the land to the ocean creating a land breeze.

Let us conclude: Air masses of diff erent temperature have diff erent pressure. Cold air has a higher pressure than ascending hot air. Th e zone in which warm air rises is called the low pressure zone. When air is warmed by radiation it rises, leaving behind less air, so there are fewer air molecules and therefore less pressure. Low pressure zones are oft en cloudy, and it might rain or snow. In high pressure zones air masses sink downwards – this increases the air pressure. Air moves from high to low pressure areas. Th is movement of warm air masses moving upward and being replaced by cooler air masses is called convection. Th e heat (energy) transfer during convection is called convectional current. Pressure Gradient Force We explained that wind is air in motion, i.e. wind originates from diff erences in air pressure within our atmosphere. Wind is thus a result of the steepness or gradient of atmospheric air pressure found between high and low pressure zones. When expressed scientifi cally, pressure change over a unit distance is called pressure gradient force and the greater this force, the faster the winds will blow (Figure 3). Th e pressure gradient force is the primary force infl uencing the formation of wind from local to global scales.

FIGURE 3: TWO DIFFERENT PRESSURE GRADIENT SCENARIOS AND THEIR RELATIVE EFFECT ON WIND SPEED

10 mb change 40 mb change 1020 mb 1010 mb 1020 mb 980 mb

Wind direction Wind direction

100 kilometers 100 kilometers

Pressure gradient Pressure gradient 0.1 mb/kilometer 0.4 mb/kilometer Wind speed will be 2 times greater

Image source: S4GJ/GIZ. Air pressure and pressure gradient is stated in millibar (mb), i.e. one thousandth of a bar, the unit of atmospheric pressure equivalent to 100 pascals.

89 Wind Direction Wind has direction and speed. Wind direction is expressed as the direction from which the wind is blowing (Figure 4). For example, easterly winds blow from East to West, while westerly winds blow from West to East.

FIGURE 4: SIXTEEN PRINCIPAL BEARINGS OF WIND DIRECTION

0° 360° N 315°

THEME 2.1.1 45° NW NE NNW NNE

WNW ENE

270° W E 90°

WSW ESE

SSW SSE SW SE 225° 135° S 180°

Image source: S4GJ/GIZ

Wind Speed Winds have diff erent levels of speed, and common terms such as breeze and gale describe how fast they blow. Wind speed (v in km/h) is the rate at which air fl ows past a point above the Earth’s surface. Wind velocity can vary throughout the day and year based on geography, topography and season. As a result, certain locations are better suited for wind turbine placement than others. In general, wind speeds are higher near the coast, off shore and inland at hilltops, since there are fewer objects and structures to slow the wind down. Commonly, wind speeds are described using a scale called the Beaufort scale, which divides wind speeds into 12 diff erent categories.

90 T A B L E 1 : BEAUFORT WIND SPEED SCALE IN KM/H

Code Speed (km/h) Description Effects on the environment 0 < 1 Calm Smoke rises vertically 1 1 - 5 Light air Smoke drifts slowly 2 6 - 11 Light breeze Leaves rustle, wind can be felt, wind vanes move 3 12 - 19 Gentle breeze Leaves and twigs on trees move 4 20 - 29 Moderate breeze Small tree branches move, dust is picked up from the ground surface 5 30 - 38 Fresh breeze Small trees move 6 39 - 51 Strong breeze Large branches move, telephone and power overhead wires whistle THEME 2.1.1 7 51 - 61 Near gale Trees move, difﬁcult to walk in the wind 8 62 - 74 Gale Twigs break off from trees 9 75 - 86 Strong gale Branches break off from trees, shingles blown off roofs 10 87 - 101 Whole gale Trees can become uprooted, structural damage to buildings 11 102 - 120 Storm Widespread damage to buildings and trees 12 > 120 Hurricane Severe damage to buildings and trees

Your own notes

91 Exercises

1. Visualising convection currents in the atmosphere (air). Do the following experiment: Use a small tank/aquarium fi lled with water placed over a bowl of hot water and a bowl of ice. Carefully place red food dye into the left side of the tank and blue food dye into the right side of the tank. Observe and describe how changes in fl uid temperature cause a convection current indicated by the red and blue food dye. THEME 2.1.1

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… 2. Because warm air is less dense and thus lighter than cool air, it rises. With this in mind, describe each of the three pictures below and decide which one correctly describes air in motion.

92 3. During summer a sea breeze can appear along the coast. Th is is due to diff erent surface temperatures, a phenomenon illustrated in the image below. Explain the term 'sea breeze' and using each of the four pictures, describe what exactly caused the breeze during the day.

Warm air High High pressure Sun ray pressure

Low Low Sea Sea pressure Sea pressure Sea THEME 2.1.1

Further Information on the Resource CD

(i) Forces Acting to Create Wind, Fundamentals of Physical Geography, 2006.

93 THEME 2.1.2 WIND POWER FACTORS

Introduction

Wind is air in motion due to temperature and air pressure gradients that are caused by solar irradiation, i.e. heat energy absorbed by the Earth’s surfaces. Wind can thus be considered as solar power in kinetic form. In this theme we are interested in identifying the key factors for the conversion of wind’s kinetic energy into useful work, i.e. wind speed and swept rotor area.

THEME 2.1.2 THEME Keywords

Wind power Crucial factors for wind power Power coeffi cient Aerodynamic effi ciency Mechanical and electrical effi ciency Calculations Theme Outcomes

At the end of this theme you should be able to: (i) Explain wind as a type of kinetic energy and ultimately as a form of solar energy. (ii) Explain the key factors aff ecting the amount of energy a turbine rotor can harness. (iii) Describe the principle of energy conversion. (iv) Describe the enormous potential wind energy holds. (v) Explain why wind turbines are usually set up on a pole or tower. Deﬁ nition of Terms Wind Power Wind possesses energy by virtue of its motion. Any device capable of slowing down the mass of moving air can extract part of the energy and convert kinetic energy into useful work. Th e mechanism used to convert air motion, i.e. kinetic energy of wind into useful work is referred to as wind energy converters, such as wind turbines which capture and convert air fl ow into a rotational movement.

Let us look at kinetic energy of wind in more detail. Using physical variables, wind power (Pwind), or

power input of wind (Pinput) can be described using the following parameters in formula (1):

1 3 (1) P wind = 2 x ρ x A x (v ) (one-half, times the air density (ρ), times the swept rotor area (A), times the cube of the wind speed (v)).

Albeit the three physical variables describing wind power (Pwind) in formula (1) are not new to us, i.e. air density (ρ), area (A) and speed (v), we shall have a detailed look at how one arrives at formula (1). Before we do this, we should consider that we have discussed power (P) and energy (E) in engineering terms in student book RET Level 2 and indicated that both terms are oft en used in everyday language but in a diff erent context and with completely diff erent meanings. In engineering, energyE ( ) is defi ned as the capacity to do work (W). Th e concept of power P( ) is a measure of how rapidly work (W) is done. Th rough the concept of work W( ), i.e. work (W) as the transfer of energy (E) from one object to another, we can measure the energy (E) transferred during interactions between systems or objects. Work (W) always requires motion of a system or parts of it. In this context we also need to remember the concept of energy conservation, i.e. energy (E) is never created nor destroyed, but merely transformed (fi rst law of thermodynamics). In practical terms, this just means that if energy (E) is transferred from one object to another, e.g. converting air fl ow (kinetic energy) into a rotational movement (mechanical energy), some

94 energy (E) will be transformed into thermal energy (heat), e.g. friction between the moving parts (bearings and shaft s etc.). Considering the above, we shall now have a detailed and step-by-step look to better understand how one 1 3 arrives at formula (1) Pwind = 2 x ρ x A x (v ) :

Step 1:

Simply put, we can defi ne work W( ) as the transfer of energy (E) from one object to another, power (P) as the rate of doing work (W), and energy as power (P) multiplied by time (t). Th ese defi nitions give us the following mathematical equations:

W (2) P = t (power is equal to work divided by time)

(3) E= P x t (energy is equal to power times time) 2.1.2 THEME

Step 2:

We have defi ned energy E( ) as the ability to do work and work (W) as a specifi c form of energy transfer. You can see there is an intimate relationship between work and energy, and albeit diff erent, work W( ) and energy (E) are treated as the same. It thus follows that power (P) can also be defi ned as energy transferred per unit time (t).

E (4) P= t (power is equal to energy transferred divided by time)

Step 3:

Wind as air molecules in motion has kinetic energy. Given that wind is nothing more than the mass of moving air molecules, we can assume that the amount of kinetic energy depends on two variables, mass (m) and velocity (v) of moving air molecules. Th us, the following equation is used to represent kinetic energy (Ek):

1 2 (5) Ek = 2 x m x v (kinetic energy is equal to one-half, times mass, times velocity squared)

Step 4:

By using formula (4) and (5), and substituting energy (Ek) in formula (4) with formula (5), i.e. one-half, 1 2 times mass, times velocity squared ( 2 x m x v ), it follows that wind power can be described as:

E 1 m 2 m (6) P = t = 2 x t x (v ) (wind power is equal to one-half, times mass fl ow rate ( t ), times velocity squared)

95 FIGURE 1: MASS OF AIR FLOWING THROUGH SWEPT ROTOR AREA (SCHEMATIC)

V THEME 2.1.2 THEME A

Image source: S4GJ/GIZ Th e volume V( ) of air fl owing through the circular swept rotor area A( ) along the length (s), i.e. the wind ‘cylinder’ indicated in orange colour, defi nes the mass m( ) of air passing through. Th us, mass m( ) can be obtained from the product of air density (ρ) and air volume (V).

Step 5:

Th e mass of air m( ) which fl ows through a surface A( ) swept by a rotor can be obtained from the product of air density (ρ) and air volume (V).

m = ρ x V

Step 6:

Redefi ning volume V( ) as area (A) times length (s) will permit us to replace the volume (V) by:

m = ρ x A x s

FIG U RE 2: VOLUME (V ) OF THE WIND ‘CYLINDER’ CAN BE REDEFINED AS THE SWEPT ROTOR AREA (A) MULTIPLIED BY THE LENGTH (S) OF THE WIND ‘CYLINDER’.

Density of air p Area, A

Wind passes along this length (s) per Wind speed v unit time (t)

Image source: S4GJ/GIZ

96 Step 7:

s m Considering that length over time is velocity ( t = v), we can now substitute the term mass fl ow rate ( t ) in formula (6) with the product of air density (ρ), swept rotor area (A) and wind speed (v):

m t = ρ x A x v

Step 8:

E 1 m 2 By inserting the term (ρ x A x v) for mass fl ow into formula (6), i.e. P = t = 2 x t x (v ), we derive at our formula (1) for wind power:

1 2 1 3 (1) Pwind = 2 x ρ x A x v x (v ) = 2 x ρ x A x (v ) THEME 2.1.2 THEME

Th us, wind power is equal to one-half, times the air density (ρ), times the swept rotor area (A), times the cube of the wind speed (v). Wind power (P) is given in watt, i.e. joules/second, density (ρ) in kg/m3, swept area (A) in square metres (m2), and the velocity (v) in metres per second (m/s). Crucial Factors for Wind Power 1 3 Th e three factors in formula (6) Pwind = 2 x ρ x A x (v ), clearly indicate that wind velocity (v) is the most crucial factor, and power output of a wind turbine rotor is thus proportional to the cube (third power) of the wind speed. In other words, if velocity of wind doubles, power increases by a factor of eight (23 = 2 x 2 x 2 = 8) (Figure 3). Th us, small changes in wind speed have a large impact on the amount of power available.

FI G U R E 3: RELATIONSHIP BETWEEN WIND SPEED AND WIND POWER

700

) 600 2 500 400 300 200

Wind (watt/m power 100

0 0 2 4 6 8 10 Wind speed (m/s)

Image source: S4GJ/GIZ. If wind speed doubles, power increases by a factor of eight (23 = 2 x 2 x 2 = 8).

Considering that wind speed increases with height, increases to the turbine tower height can result in enormous power increases generated by wind turbines (Figure 4).

97 FIGURE 4: WIND SPEEDS AND POWER INCREASE WITH HEIGHT

30 Tower height Tower

THEME 2.1.2 THEME 20

0 41 75 100 124 Increase in wind power %

Image source: S4GJ/GIZ Wind speeds increase with height (metre), and so does power (kWh in %).

Th e swept rotor area A( ) of the turbine is the second most crucial factor for power output. Th e larger the swept rotor area i.e. the size of the area through which the rotor spins, the more power the turbine can capture. Th e swept rotor area can be calculated from the length of the turbine blades using the equation for the area of a circle, i.e. A=π x r2 , where the radius is equal to the blade length (Figure 5). Th us, a small increase in blade length, i.e. equal to the radius of a circle, and considering its squared power (r2), results in a large increase in power. In other words, since the swept rotor area increases with the square of the radius, a turbine with blades twice as large will receive 22 = 2 x 2 = four times as much kinetic energy. Th e rotor area is subsequently the second most important determinant for a wind turbine.

FI G U R E 5: THE ROTOR’S SWEPT AREA

Swept area of Rotor blades diameter

Image source: S4GJ/GIZ Th e rotor’s swept area can be calculated using the formula for a circle where the radius (r) is equal to the blade length.

98 FIGURE 6: POWER OUTPUT INCREASES AS THE SWEPT ROTOR AREA INCREASES

80 m

2500 kW 72 m

2000 kW 64 m

1500 kW 54 m 1000 kW 48 m 44 m 750 kW 600 kW

40 m 2.1.2 THEME

33 m 500 kW 300 kW 27 m

225 kW

Image source: S4GJ/GIZ A typical turbine with a 600 kW electrical generator will typically have a rotor diameter of between 40 - 44 m. If you double the rotor diameter to 80 m, your swept rotor area is four times larger (22 = 2 x 2 = 4, i.e. two squared). Th is means that you also get four times as much power output from the rotor, i.e. around 2400 kWh.

Air density (ρ) is the fi nal determining factor for wind power. Air density varies with elevation and temperature. At normal atmospheric pressure and at 15°C, air weighs some 1,225 kilogrammes per cubic metre (kg/cm3), but the density decreases slightly with increasing humidity. Air is less dense at higher elevations than at sea level, and warm air is less dense than cold air. All else being equal, turbines will produce more power at lower elevations and in locations with cooler average temperatures. However, these diff erences in air density are usually considered as marginal compared to the cube power (23) of wind speed and the squared power (22) of the swept rotor area.

Power Coefﬁ cient (Cp) A common misconception is that all of the kinetic energy from the wind can be converted into mechanical and subsequently electrical energy. Th is is impossible - should the entire kinetic energy be converted, there would be no wind left , i.e. wind would be completely absorbed. Many factors make this impossible

(aerodynamic, mechanical and electrical effi ciencies). A power coeffi cient (Cp) has thus been introduced as a measure of overall wind turbine effi ciency. You might recall the symbol η , the small Greek letter eta, which is used to represent effi ciency.

Th eC p is the ratio of actual electric power produced by a wind turbine divided by the total wind power fl owing into the swept rotor area at specifi c wind speed. When defi ned in this way, the Cp represents the combined eﬃ ciency of the various turbine system components, including the turbine blades, the shaft bearings and gear train, generator and power electronics, and can be included in formula (6) so that we arrive at:

1 3 (7) P = Cp x 2 x ρ x A x (v )

Th us, power is equal to the turbine-specifi c power coeﬃ cient, one-half times the air density (ρ), times the rotor area (A), times the cube of the wind speed (v).

Power (P) is given in watt, i.e. joules/second, the Cp always has a value smaller than 1 (usually between 0.3 - 0.4), density (ρ) in kg/m3, swept area (A) in square metres (m2), and the velocity (v) in metres per second (m/s).

99 Th eC p for a particular turbine is measured or calculated by the manufacturer and usually provided at

various wind speeds. If you know the Cp at a given wind speed for a specifi c turbine you can use it to estimate the electrical power output. Please note that the power coeﬃ cient should only be used to compare

the performance of wind turbines. Th e Cp has no relationship to the eﬃ ciencies of other electrical power technologies, such as PV, gas-turbines etc. Th e energy conversion process, i.e. the kinetic energy from the wind converted to mechanical and subsequently electrical energy, can be described by three major conversion steps: aerodynamic, mechanical and electrical conversion. During each step, some energy is transformed into heat energy and in everyday language we say some energy is ‘lost’ in the process. Th is is not entirely correct, because if energy is transformed from one form into another the total energy involved in this process is conserved. Th us, the total energy involved in the interaction does not become less or more, we only cannot directly use most of the thermal energy (heat) that is radiated into the environment during transformation processes for the purpose intended. THEME 2.1.2 THEME

F I G U R E 7: ENERGY TRANSFORMATIONS RELEVANT TO A WIND TURBINE

Kinetic Mechanical Electrical energy energy energy

WIND TURBINE GENERATOR

Image source: S4GJ/GIZ

Aerodynamic Effi ciency Th e fi rst and largest ‘losses’ are due to aerodynamic processes. Th e effi ciency with which the rotor blades convert the available kinetic wind energy into rotating shaft motion (mechanical energy) is referred to as aerodynamic effi ciency. To understand this better we need to understand some basic aerodynamic principles fi rst. Th e two primary aerodynamic forces at work at rotor blades are l i , which acts perpendicular to the direction of wind fl ow, and drag, which acts parallel to the direction of wind fl ow.

100 FIGU RE 8: LIFT AND DRAG

Lift

Drag

Wind flow

Airfoil Lift motion

Drag THEME 2.1.2 THEME

Lift

Drag Wind flow Lift

Drag

Image source: S4GJ/GIZ Lift and drag, the two primary aerodynamic forces at work at rotor blades. Turbine blades are shaped similar to airplane wings, i.e. they have an air foil type of design.

In an air foil, one surface of the blade is somewhat rounded, while the other is relatively fl at. A simplifi ed explanation of lift is when wind travels over the upper curved surface of the blade, it has to move faster to reach the end of the blade in time to meet the wind travelling under the lower fl at surface of the blade. Th e faster air moves, the lower the static pressure is. Lower pressure pulls on the surface, high pressure pushes. As a result, the upper part of the airfoil is pulled and the lower is pushed. Collectively this creates the lift . Under the lower fl at surface of the blade, the wind moves slower and creates an area of higher pressure that pushes on the blade, creating a slowing down eff ect. Drag is the retarding force acting on the blade while moving through the air. Th is phenomenon is called Bernoulli’s principle (see the three videos provided on the resource CD).

Th e limited aerodynamic effi ciency of a wind turbine is caused by the braking of the wind from its upstream speed v1 to its downstream speed v2, while allowing a continuation of the fl ow regime v( 2 < v1). Th e additional losses in aerodynamic effi ciency are caused by the viscous and pressure drag on the rotor blades, and the swirl imparted to the air fl ow by the rotor. Th is allows a theoretical maximum of around 59% of the wind’s kinetic energy to be captured. Th ese fi ndings were published in 1919, by the German physicist Albert Betz, and this is thus called Betz’s limit (Figure 9). In practice only 40-50% of aerodynamic effi ciency is achieved by current rotor designs.

101 FIGURE 9: THE BETZ LIMIT

A1 v1 A2 v2 THEME 2.1.2 THEME

Image source: S4GJ/GIZ Th e Betz limit calculates the maximum theoretical eﬃ ciency of a horizontal rotor by withdrawing energy

from the wind by passing with v1 from A1 to A2. At a certain distance (A2) behind the rotor, the wind

fl ows with a reduced velocity v( 2). In other words, Betz’ limit shows that as air fl ows with a speed of v1

from a certain area A1 through a horizontal rotor, it slows from losing energy to extraction from the rotor, and spreads out to a wider area (A2) with a reduced velocity (v2). As a result, rotor geometry limits aerodynamic effi ciency (η) to a maximum of 59.3%. Mechanical and Electrical Effi ciency Overall turbine effi ciency is reduced due to mechanical transmission, i.e. various rotating gears and shaft s, and due to electrical and electronical system performance, including generator and power electronics ‘losses’, for example due to conversion of much less-than-perfect electric frequencies into precise 50 Hz power needed for the grid.

FIGURE 10: MECHANICAL AND ELECTRICAL EFFICIENCY

Aerodynamical Mechanical Electrical efficiency efficiency efficiency

Generator Low speed shaft Gearbox High speed shaft and power electronics Power out

Wind out Shaft support Wind in bearings

Image source: S4GJ/GIZ

102 Calculation Example

Considering all of the above, the next seven steps illustrate how to calculate the maximum power of an imaginary turbine and interpret Cp and power output diagrams.

Step 1: We fi rst need to designate the symbols for aerodynamic, mechanical, and electrical eﬃ ciencies (η):

ηa = aerodynamic eﬃ ciency

ηm = mechanical eﬃ ciency

ηe = electrical eﬃ ciency

Step 2:

We can now show that Cp is the product of all three subsystem eﬃ ciency types: THEME 2.1.2 THEME

(8) Cp = ηa x ηm x ηe

Step 3: We can then use the following values for each of the three eﬃ ciency types, assuming that all three subsystems operate at near maximum eﬃ ciency, and near the best operating design point of all components:

ηa = aerodynamic eﬃ ciency = 0.397 (39.7%)

ηm = mechanical eﬃ ciency = 0.96 (96%)

ηe = electrical eﬃ ciency = 0.94 (94%)

It follows that Cp = ηa x ηm x ηe = 0.397 x 0.96 x 0.94 = 0.358 (35.8%)

Step 4: 1 3 Using formula (1) Pwind = 2 x ρ x A x (v ), with wind speed at 12 m/s, an assumed standard air density (ρ) at sea level of 1.225 kg/m3, and a blade diameter of 101 m, we can calculate the power input into the turbine:

1 3 3 2 (6) Pinput = 2 x ρ x A x (v ) = 0.5 x 1.225 kg/m x 8015.07 m x 1728 m/s = 8483 kW.

Step 5:

With a Cp given at 35.8% and Pinput at 8483 kW, we can easily calculate the actual output power produced by the imaginary turbine:

Poutput = Cp x Pinput = 0.358 x 8483 kW = 3037 kW

Th e maximum calculated power of the imaginary turbine is 3037 kW.

Step 6: Look at the diagram in Figure 11. It is a diagram for a specifi c wind turbine showing the Cp and power output (kW) vs wind speed (m/s). Remember, turbines vary and each specifi c model will have its own data, this is just one example. Firstly, note that the Cp value (yellow line in chart) varies signifi cantly with wind speed. Further, please note that a power coeffi cient of 35.8% is about the Cp value in the diagram below at a wind speed of 12 m/s (indicated by a red star). For this particular turbine, maximum effi ciency occurs around the wind speed range of 8 to 10 m/s. Other turbines may attain maximum effi ciency at other speeds. Th e blue line shows the electric power produced as a function of wind speed. When the turbine reaches maximum power, which in this case is 3037 kW, it levels off (indicated by red arrow). Th is is because the turbine blades are turned or feathered to keep them from spinning too fast or breaking from too much force. Th e turbine control system will keep the rotor spinning at or near a constant value. Th ough it is not shown in the diagram, at some point the rotor is stopped for safety, and power rapidly goes to zero.

103 ( ) FIGU RE 11: POWER COEFFICIENT CP AND POUTPUT vs WIND SPEED

3500 0.600

3000 0.500 p

2500 C 0.400 2000 0.300 1500 0.200 1000 Power coefficient,Power

THEME 2.1.2 THEME 500 0.100 Electric power produced (kW)Electric produced power 0 0.000 Wind speed (m/s)

Electric power Power coefficient, Cp

Image source: S4GJ/GIZ

Cp (orange line) and electric power, Poutput (blue line). Th e top fl at part of the blue line is what is usually called rated power, or maximum power. Rated power in this case starts at about 12 m/s. Once the turbine

reaches maximum power, the power coeﬃ cient starts to fall off rapidly. Th is is because Poutput remains

constant while the Pinput increases rapidly with higher wind speed. Remember the Pinput is a function of

the wind speed cubed. Poutput stays constant while Pinput increases very quickly, thus the Cp values have to get smaller.

Step 7: Look at the diagram below (Figure 12). Th e wind power into the turbine blades is shown by the orange

line. Pinput increases with the cube of the wind velocity. Poutput is shown by the green line which levels off at 3037 kilowatts (see Step 5).

FIGURE 12: PINPUT AND P OUTPUT vs WIND SPEED

35000

30000 25000 1 3 P = 2 x ρ x A x (v ) 20000 input 15000 Pout = C x P Power (k/W)Power 10000 p input 5000

0 0 2 4 6 8 10 Wind speed (m/s)

Pinput Poutput

Image source: S4GJ/GIZ

Pinput is a function of the wind speed cubed and thus increases rapidly with increasing wind speeds. In

order to maintain system functioning Poutput is kept constant once maximum (or rated) power is reached.

104 Exercises

1. Draw a Sankey diagram to illustrate the energy transformation processes in a wind turbine where: (i) 100 units of energy are available in the incoming air (wind) as kinetic energy. (ii) 40 units are converted into rotational/mechanical energy by the rotor. (iii) 35 units are transferred by the shaft , some units are absorbed by the brake and gears as thermal energy. (iv) 33 units are converted from mechanical energy into electrical energy by the generator. (v) 30 units is the net output, as 3 units are ‘lost’ in further conversion and distribution processes. THEME 2.1.2 THEME

2. Wind turbine power calculation One of the world’s largest turbines has a rotor diameter of 126 metres. As a fi rst step, calculate the rotor sweep area using the formula for a circle, i.e. A=π x r2. Th is turbine is an off shore wind turbine. We thus know that it is situated at sea-level and can put air density (ρ) at 1.23 kg/m3. For a wind speed at 14 m/s the generator is rated at 5 MW. Use formula (1), insert the known values

and calculate Pinput. State Pinput clearly and answer the following question: Why is Pinput so much larger than the rated power of the turbine generator (5 MW)?

105 3. Size matters in wind turbines. Th e longer the rotor blades, and therefore the greater the diameter of the rotor, the more kinetic energy a turbine rotor can capture from the wind and the greater the electricity-generating capacity. Generally speaking, doubling the rotor diameter can result in a four-fold increase in energy output. Please explain why this is the case!

…………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… 4. Some people claim that in some cases, e.g. in lower wind speed areas, a smaller- diameter rotor can end up producing more energy than a larger rotor. What is your opinion? Please explain

THEME 2.1.2 THEME your view!

…………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

5. Tower height is a major factor for input power (Pinput). Please explain why this is the case! Please also estimate the Pinput % increase by doubling elevation (tower height).

Further Information on the Resource CD

(i) Aerodynamics of rotor blades, M. Ragheb, pdf 2013. (ii) WE Handbook- 2- Aerodynamics and Loads, pdf, www.gurit.com/fi les/documents/2aero- dynamicspdf. (iii) Wind Turbines Th eory - Th e Betz Equation and Optimal Rotor Tip Speed Ratio, Ragheb & Ragheb, pdf, 2011. (iv) Bernoulli’s Principle, video (v) Wind turbine air foil forces, video (vi) Wind turbine design, video

106 THEME 2.1.3 ESSENTIAL WIND TURBINE COMPONENTS AND THEIR FUNCTIONS

Introduction

Th e most common type of commercial wind turbines are horizontal axis wind turbines (HAWT). Th e rotor axis of a HAWT lies horizontal, parallel to the air fl ow, with the blades sweeping a circular plane usually situated upwind in front of the tower. In this theme we will focus on the most essential components of a HAWT. We will later also introduce you to diff erent turbine designs and their relevant components. THEME 2.1.3 THEME Keywords

Tower Yaw drive Nacelle Low-speed shaft Brakes Gearbox Generator High-speed shaft Control systems Anemometer Wind vane Rotor Blades Pitch system DC machines Working principle of a single loop DC generator DC machine types Separately-excited DC machines Self-excited DC generators Permanent magnet DC generator AC machine types: synchronous generator AC machine types: induction/asynchronous generator Wind turbine control systems Connecting small-scale renewable embedded generation (SSREG) to the grid Connecting large-scale wind power plants to the grid Transformer, switchgear and power lines

Theme Outcomes

At the end of this theme, you should be able to: (i) Illustrate by means of a sketch the inside of a larger wind turbine and explain the components’ diff erent functions. (ii) Describe the purpose and principle function of a DC generator. (iii) Explain the most important arrangements required to connect wind turbines to the grid including transformer, medium and high voltage switchgear and high and low tension power lines.

107 Deﬁ nition of Terms HAWT Subsystems Horizontal axis wind turbines (HAWT) consist of three principal components: the nacelle, rotor, and tower (Figure 1). Th e nacelle compartment is connected to the rotor hub by a shaft and contains the brakes, gears, generator and controlling mechanisms. Th e rotor, usually consisting of three wing-shaped blades connected to a central hub, converts the kinetic energy of the wind into rotational energy. Th e tower, including the supporting foundation, contains the yaw drive, and provides access to the nacelle and the height necessary to access the targeted wind resources.

FIGURE 1: HAWT SUBSYSTEMS (SCHEMATIC) THEME 2.1.3 THEME

12 13

4 6 14 3 10 5

7 2 8 11

Image source: S4GJ/GIZ Key components: Tower (1), Yaw drive (2), Nacelle (3), Low-speed shaft (4), Brakes (5), Gearbox (6), Generator (7), High-speed shaft (8), Control systems (9), Anemometer (10), Wind vane (11), Rotor (12), Blades (13), Pitch system (14).

(1) Tower, made from tubular steel, concrete or steel lattice, supports the nacelle and rotor. Taller tow- ers enable turbines to capture more kinetic energy because wind speed increases with height. (2) Yaw drive orients the nacelle and rotor into the wind (upwind concept). (3) Nacelle sits on top of the tower and contains the breaks, gears, generator and controlling mechanisms. Some nacelles are large enough for a helicopter to land on. (4) Low-speed sha , turns at about 30-100 rpm. (5) Brakes (mechanical, electrical, or hydraulic) can stop drive shaft s in emergency situations. (6) Gearbox, connects the low-speed shaft to the high-speed shaft and increases the rotational speeds up to about 1000 - 2000 rpm, as this is the rotational speed required by most generators. As indicated in Th eme 1.1.3, the gearbox is usually the third most costly component of a HAWT. Th us, some modern turbines use direct-drive generators that operate at lower rotational speed and thus do not require gearboxes. (7) Generator, converts mechanical (rotational) energy into electrical energy, i.e. a rotating magnetic fi eld induces current. Please note that two main generator types are employed, i.e. asynchronous (induction) type generators and synchronous (permanent magnet) type generators. Th e latter have the potential to work without gearboxes, but bear higher cost. (8) High-speed sha , drives the generator. (9) Control systems (electronics), for drivetrain and wind (cut in/out) speed and blade regulation (pitch/stall).

108 (10) Anemometer measures wind speed and transmits wind speed data to the control system. (11) Wind vane reacts to and measures wind direction and communicates with the yaw drive to orient the turbine into the wind. (12) Rotor, blades and hub together form the rotor. (13) Blades create lift due to their air foil cross-section and rotate the rotor. Most large commercial turbines have either two or three blades. (14) Pitch system turns the blades in or out of the wind.

DC Machines Electric machines are electromechanical energy conversion devices. Motors convert electrical energy into mechanical energy while generators do exactly the opposite, i.e. converting mechanical power into electrical power. It is the latter which are relevant to a wind turbine. However, the working principles

of motors and generators have much in common, whether it is a DC (direct current) or AC (alternating 2.1.3 THEME current) machine. In our context we will focus on DC machines. In most cases, regardless of type, DC machines consist of a stator (stationary fi eld) and a rotor (the rotating fi eld or armature). DC machines operate through the interaction of magnetic fl ux and electric current, based on the fundamental principle of Faraday’s law of electromagnetic induction. According to this law, when a conductor moves in a magnetic fi eld it cuts through magnetic lines of force, inducing an electromagnetic force emf( ) in the conductor. Th e magnitude of this induced emf depends on the rate of change of fl ux (magnetic line force). Th eemf will cause a current to fl ow if the conductor circuit is closed. Hence, the two most essential features of a generator are a magnetic fi eld and conductors which move inside that magnetic fi eld.

Working Principle of a Single Loop DC Generator Let us start with the most basic type of DC generator, a single loop (armature) generator. As indicated in Figure 2, a single loop of a rectangular conductor is placed between two opposite magnetic poles (N- pole/red and S-pole/blue). Th e corners of the rectangular conductor loop are A, B, C and D.

FIG U RE 2: A SINGLE LOOP CONDUCTOR PLACED IN A MAGNETIC FIELD (SCHEMATIC)

a A

B D

N S

C b

Image source: S4GJ/GIZ Due to mechanical input energy, e.g. wind power, the conductor rotates inside a magnetic fi eld around its axis a and b. When the loop rotates from its vertical position to its horizontal position, its two sides, i.e. AB and CD of the loop always cut through the fl ux lines of the magnetic fi eld (Figure 3). As a result, an emf is induced in both sides (AB and CD) of the loop.

109 FI G U R E 3: THE CONDUCTOR ROTATES IN A MAGNETIC FIELD INTO ITS HORIZONTAL POSITION

a Direction of rotation

D A THEME 2.1.3 THEME N C B S

Direction of flux b Direction of induced current

Image source: S4GJ/GIZ Th e conductor rotates within a magnetic fi eld into its horizontal position, thus inducing a current in the loop.

FIGURE 4: FLUX LINES - THE PICTORIAL REPRESENTATION OF A MAGNETIC FIELD

Lines of magnetic flux

S N S N

Unlike poles - 'attract'

S N N S

Like poles - 'repel'

Image source: S4GJ/GIZ

110 As the loop ABCD is closed, there will be a current circulating through the loop. Th e direction of the current can be determined by Flemming’s right hand rule (Figure 5). Th is rule says that if you stretch thumb, index fi nger and middle fi nger of your right hand perpendicular to each other, then the thumb indicates the direction of motion of the conductor, the index fi nger indicates the direction of the magnetic fi eld, i.e. N-pole to S-pole, and the middle fi nger indicates the direction of fl ow of current through the conductor. If we apply this right hand rule to our example, we can see that at the horizontal position of the loop (Figure 3), current will fl ow from point A to B and on the other side of the loop current will fl ow from point C to D.

FI G U R E 5: FLEMMING’S RIGHT HAND RULE

Motion THEME 2.1.3 THEME Magnetic field

Current

Image source: S4GJ/GIZ

If the loop rotates further, it will return to its vertical position, but now the upper side of the loop will be CD and the lower side will be AB (Figure 6), just opposite the vertical position shown in Figure 2. In this position the tangential motion of the sides of the loop is parallel to the fl ux lines of the fi eld. Hence, there will be no fl ux cutting and consequently no current induced in the loop.

FIGURE 6: ROTATING TOWARDS ITS VERTICAL POSITION THE CONDUCTOR IS NOT INDUCING A CURRENT (SCHEMATIC)

a D Direction of rotation

C A

N S

b B Direction of flux

Image source: S4GJ/GIZ

If the loop rotates further, it returns to its horizontal position but now the AB side of the loop is in front of the N-pole and the CD side stays in front of the S-pole. In this position the tangential motion of the loop

111 sides is perpendicular to the fl ux lines, hence the rate of fl ux cutting is at its maximum and according to Flemming’s right hand rule, current fl ows from B to A and on the other side from D to C (Figure 7).

F I G U R E 7: THE CONDUCTOR ROTATES INTO ITS HORIZONTAL POSITION INDUCING A CURRENT IN THE LOOP (SCHEMATIC)

a Direction of rotation

A D THEME 2.1.3 THEME

N B C S

Direction of flux b Direction of induced current

Image source: S4GJ/GIZ

If the loop continues to rotate around its axis, every time the side AB is in front of the S-pole, a current fl ows from A to B and when it comes in front of the N-pole, the current fl ows from B to A. Similarly, every time the side CD is in front of the S-pole, a current fl ows from C to D and when it comes in front of the N-pole the current fl ows from D to C. We now connect the loop with a split ring as shown in Figure 8. Split rings are made out of a conducting cylinder cut into two halves or two segments which are insulated from each other. Th e external load terminals are connected with two carbon brushes which rest on the slip ring segments.

FIGU RE 8: THE CONDUCTING LOOP IS CONNECTED TO TWO SPLIT RINGS AND TWO CARBON BRUSHES WHICH REST ON THE SLIP RING SEGMENTS

I N S I

Brush and terminal I I Segment of split ring Resistor/Load

Image source: S4GJ/GIZ

112 In Figure 9 (left -hand side) it can be seen that in the fi rst half of the revolution, current always fl ows along ABLMCD, i.e. brush 1 is in contact with segment a of the split ring. In the next half revolution (right-hand side of Figure 9) the direction of the induced current in the coil is reversed, but at the same time the position of the segments a and b are also reversed which results in brush 1 coming in contact with segment b. Hence, the current in the load resistance again fl ows from L to M via a resistor.

FIGURE 9: CURRENT FLOW UNDER LOAD RESISTANCE (SCHEMATIC)

A D D A THEME 2.1.3 THEME

B C C B

+ _ + _ a b b a 1 2 1 2

L M L M

Image source: S4GJ/GIZ

Th e position of the brushes of this DC generator is arranged in such a way that the change-over of the segments a and b from one brush to the other takes place when the plane of the rotating coil is parallel to the fl ux lines of the fi eld. Hence, there will be no fl ux cutting and consequently no current induced in the loop - in this position the induced emf in the coil is zero. Th e unidirectional (but not continuous) waveform of the DC current through the load circuit is shown in Figure 10. Th is is the basic working principle of a DC generator, explained in a single loop generator model. It would be very helpful for you to also have a look at the video clips provided on the resource CD. Several of the clips show a 3D-animation of the fl ux lines and current fl ow in a single loop conductor. Some other video clips show the complete construction and functioning of more sophisticated DC generators, i.e. brushed and brushless types with permanent magnets. Th e latter are the preferred choice of DC machines.

FIGURE 10: UNIDIRECTIONAL DC CURRENT

emf

0 90° 180° 270° 360° Cycle ( )

Image source: S4GJ/GIZ

113 DC Machine Types Instead of a single individual loop of wire as shown in the previous working principle, DC machines have many loops wound together to form a coil of wire (Figure 11), so that much more emf and therefore current can be generated for the same amount of magnetic fl ux. All generators consist of two main parts, the stator and the rotor. Th e stator is the stationary part of the machine and the rotor is the part of the machine that rotates.

FIGU RE 11: DC MACHINES HAVE MANY LOOPS OF WIRE WOUND TOGETHER TO FORM A COIL

Stator magnets THEME 2.1.3 THEME

Armature

Windings

Brushes

Commutator

Terminals

Image source: S4GJ/GIZ

Based on the type of production of magnetic fl ux DC machines can be classifi ed as follows:

FIG U RE 12: TYPES OF DC MACHINES (SIMPLIFIED)

DC machines

Separately-excited Self-excited Permanent magnet

Shunt-excited Series-excited Compound-excited

Image source: S4GJ/GIZ

114 Separately-excited DC Machines With these types of machines, the armature current does not fl ow through the fi eld windings, as the fi eld magnets are energised by an external DC source.

FI G U R E 13: SCHEMATIC DIAGRAM OF A SEPARATELY EXCITED DC MACHINE

Armature 2.1.3 THEME Field supply Armature Load

Field supply

Image source: S4GJ/GIZ

Self-excited DC Generators Th e fi eld magnets of these type of machines are energised by the current supplied by the generator itself. Th eir fi eld coils are internally connected with the armature and due to residual magnetism some fl ux is always present in the poles. When the armature rotates, some emf is produced and thus some current induced. Th is relatively small current fl ows through the fi eld coil and increases magnetic fl ux, causing a further increase of current. Th is kind of cumulative phenomenon continues until the excitation reaches the rated value of the generator. According to the position of the fi eld coils, self-excited DC generators can be sub-classifi ed as series-wound, shunt-wound and compound-wound generators.

FIGURE 14: SCHEMATIC DIAGRAMS OF SERIES-WOUND, SHUNT-WOUND AND COMPOUND-WOUND GENERATORS

DC DC DC Field Field Field Field supply supply supply Armature Armature Armature

Image source: S4GJ/GIZ

115 Permanent Magnet DC Generator Permanent magnet DC (PMDC) generators can be considered as separately-excited DC machines with a constant magnetic fl ux. PMDC machines use high strength magnets usually made from rare earth materials, such as neodymium iron/boron (NdFeB) or samarium cobalt (SmCo). Th ese type of permanent magnets provide a constant magnetic fi eld and eliminate the need for fi eld windings, thus leading to a simpler, more rugged construction. Due to their very similar design, nearly all PMDC machines can either be used as a generator or motor. In fact, the same PMDC machine may be driven electrically as a motor to move a mechanical load, or it may be driven mechanically as a simple generator to generate output power. When used as generators, PMDC machines can respond to changes in wind speed very quickly due to their strong and constant magnetic fi eld. Th ey are thus a good choice for small-scale wind turbine systems which operate at low rotational speeds, as their cut-in point is fairly low.

FI G U R E 15: SCHEMATIC DIAGRAM OF A PERMANENT MAGNET DC THEME 2.1.3 THEME GENERATOR

Field magnet Field magnet

DC armature Armature supply

Image source: S4GJ/GIZ

116 FIGURE 16: STATOR ASSEMBLY FOR A TWIN AXIAL FLUX PERMANENT MAGNET (AFPM) WIND TURBINE THEME 2.1.3 THEME

Image source: D. Boxberg Assembly of the centre set, i.e. 2 stator plates with coils back to back for a ‘four stator plate’ design which is oft en used for 1kW AFPM machines. A front stator plate with coils can also be seen in the image. A similar stator plate for the back and the non-metallic rotor are not visible in the image. Th e latter holds the permanent magnets (neodymium boron) and appears to be pressed into a heavy duty wood board or into a retainer ring. A ‘four stator plate’ design is based on four stator coil sets and two magnet rotors sandwiched between them. In the set shown in the image, each coil appears to be individually rectifi ed (AC to DC) and is wound with very small wire (approx. 0.5 mm/32 gauge) around a laminated steel core. Given that all AC coils are rectifi ed in the generator itself, DC can be sent down the monopole steel tower. Please consult the ‘Kestrel e300i Installation and Maintenance Manual’ for additional information on the resource CD.

AC Machine Types: Synchronous Generator Synchronous generators are diff erent from DC machines in that they are usually used to generate three-phase grid connected AC. Th eir simplicity and increased eﬃ ciency relates mainly to a direct drive system, i.e. the rotor is more or less mounted directly onto the generator’s main pulley shaft . However, similar to DC machines, the operation of synchronous generators is also based on Faraday’s law of electromagnetic induction. Basically, the synchronous generator’s main components consist of: 1. Stator, carrying the three separate (3-phase) armature windings (A, B and C in Figure 17) which are displaced from each other by 120°. 2. Rotor, producing a magnetic fi eld either via permanent magnets or via wound fi eld coils connected to an external DC power source.

117 F I G U R E 17: SCHEMATIC DIAGRAM OF A SYNCHRONOUS GENERATOR AND ITS AC WAVEFORM

A Stator coil outputs 2-pole +V rotor Excitation 120° 120° 120° current

B C THEME 2.1.3 THEME

+V 3-phase supply

Three stator windings 120° apart

Image source: S4GJ/GIZ Th e fi gure shows the basic construction of a synchronous generator. Th e rotor winding is connected to a DC power supply required for producing an electromagnetic fi eld around the coil. When the rotor poles turn, the magnetic fi eld also rotates at the same angular velocity. While rotating, magnetic fl ux cuts through the individual stator coils one by one and by Faraday’s law, an emf and therefore a current is induced in each stator coil. Th e magnitude of the current induced in the stator winding is a function of the magnetic fi eld intensity, which is determined by the fi eld current, the rotating speed, and the number of turns in the three stator windings. As the synchronous machine has three stator coils, the 3-phase waveform corresponds to the geometry of the coils (A, B and C). AC Machine Types: Induction/Asynchronous Generator Induction generators are based on common squirrel-cage machine types (Figure 18) and are considered as cheap and reliable. Th ey are readily available in a wide range of sizes up to multi-megawatt capacities, making them ideal for use in commercial wind power applications. Unlike synchronous generators which have to be ‘synchronised’ with the electric grid, induction generators can be directly connected to the utility grid and driven by the turbine’s rotor blades at variable wind speeds. For economy and reliability, many wind power turbines use induction generators connected to mechanical gearboxes to increase rotation speed, and thus performance and eﬃ ciency. Induction machines are also known as asynchronous machines, i.e. if they rotate below synchronous speed they can be used as a motor, and above synchronous speed they can be used as a generator producing AC. Because an induction generator synchronises directly with the main utility grid and produces the same frequency and potential, no rectifi ers or inverters are required. However, induction generators require reactive power to their windings for self-excitation. Magnetic fi eld excitation is performed diff erently via a so-called squirrel-cage structure, conducting bars embedded within the rotor body and connected together by shorting rings (Figure 18). Th ree-phase induction machines have a fi xed stator and a rotational rotor similar to synchronous generators.

118 FIGU RE 18: ASYNCHRONOUS GENERATOR DIAGRAM AND SQUIRREL- CAGE STRUCTURE (SIMPLIFIED)

End rings

Rotor shaft

B C THEME 2.1.3 THEME

Conducting bars forming 3-phase stator the squirrel cage

Image source: S4GJ/GIZ

Wind Turbine Control Systems As wind turbines increase in size and power, control systems play a major role to operate these machines in a safe manner and also to improve eﬃ ciency and quality of power conversion. Th e main objectives of wind turbine control systems are: 1. Optimising wind power capture, i.e. operating the turbine to its extract power maximum considering safe restrictions like rated power, rated speed, cut-out wind speed etc. 2. Minimising mechanical stress and protecting the systems from transient loads. 3. Power quality, i.e. conditioning generated power according to grid interconnection standards.

Your own notes

119 TA BLE 1: MAIN CONTROL TECHNIQUES USED IN WIND TURBINES

Generator torque Pitch control Yaw control Stall control control Electronic controller In a HAWT, a yaw drive is Stall control works by As the aerodynamic monitors power used to keep the rotor increasing the angle torque control output and wind facing into the wind of attack. As the wind changes, rotor speed speed. At certain high (upwind). Initially, wind- speed increases, drag changes which wind speeds the mills used ropes or chains forces on the blade subsequently changes power output will be in order to rotate the increase and lift forces output power frequen- too high, at which nacelle by means of decrease, resulting in cy. A frequency point the blades can human or animal power. reduced rotation converter is connected alter their pitch so The fantail or vane was speed. Fully stalled between the genera- that they become another historical innova- turbine blades have tor and the network to THEME 2.1.3 THEME unaligned with the tion. In the event of the ﬂat side of the maintain constant wind, slowing the change in wind direction, blade facing directly generator frequency. blades’ rotation speed the fantail could rotate into the wind, elimi- down. Pitch control the cap of a windmill nating the force of lift. requires the blades’ through a gearbox (a This is similar to pitch mounting angle to be gear-rim-to-pinion control, but instead of adjustable. system). This rotation pitching the blades positioned the rotor into out of alignment with the wind. Modern yaw the wind, it pitches drives, even though the blades to produce electronically controlled stall. and equipped with large electric motors and planetary gearboxes, have great similarities to the old windmill concept.

120 TA BL E 2: TURBINE DESIGN CONCEPTS BASED ON GENERATOR CONFIGURATION AND PITCH CONTROL

Fixed speed wind turbine A squirrel-cage induction generator (SCIG) is Type A directly connected to the grid via a transformer. This conﬁguration requires reactive external power and uses capacitors. Smoother grid connection is achieved by Gear Grid incorporating a soft starter. SCIG Softstarter

Capacitor bank

Variable speed wind turbine concept with variable rotor resistance THEME 2.1.3 THEME Wound rotor induction generator (WRIG) and pitch control is where the rotor winding of Type B the generator is connected in series with an optically controlled external resistance. This optical coupling eliminates the need of slip-rings. By varying the rotor resistance, Gear Grid the slip and thus the power output in the WRIG Softstarter system are controlled. Reactive power Capacitor bank compensation and a soft starter are required. Variable speed wind turbine concept with partial-scale power converter (DFIG) This conﬁguration is similar to the previous one, but with a stator that is directly Partial scale Type C connected to the grid, while the rotor is frequency converter connected through a partial-scale frequency converter. The latter ensures reactive power compensation and smooth grid connection. Variable speed range is +/- 30% around Gear Grid DFIG synchronous speed.

Variable speed concept with full-scale power converter This concept has full control of the synchronous speed range (0 to 100%), but given that all generated power passes through the Type D converter, power losses due to the electron- Full scale ics are higher compared to the previous frequency converter type. Various generator machines, i.e. permanent magnet excited types or squirrel- Gear Grid cage induction generators can be used. PMSG/WRSG/WRIG Typically however, a direct-driven, multipole synchronous generator without gearbox is used.

Image source: Adapted from Hansen et.al. 2004

121 FI G U R E 19: PITCH CONTROL (SIMPLIFIED) THEME 2.1.3 THEME

Image source: S4GJ/GIZ Pitch control requires the blades’ mounting angle to be adjustable so that the blades can be turned out of alignment with the wind in above-threshold wind speeds. Electronic controllers and hydraulics are used to adjust the pitch of each blade and thus the lift force, so that the rotor continues to generate power at nominal capacity even at high wind speeds.

FIGURE 20: VARIOUS BLADE ANGLES DUE TO PITCH CONTROL ENSURING MAXIMUM RATED POWER

Positive blade angle Zero degree blade angle Negative blade angle (10 degrees) for initial for running condition for overspeed (cut-off) position and low start up condition wind speed

10° -20° 0°

<3 m/s <11 m/s >11 m/s

Image source: S4GJ/GIZ Output power (orange and blue line) builds up due to increasing wind speeds, while pitch control alters the angle of attack. At 11 m/s turbine rotation is reduced towards maximum rated power (blue line).

122 FIGURE 21: PITCH CONTROL MECHANISM FOR A 1 KW WIND TURBINE THEME 2.1.3 THEME

Image source: D. Boxberg Th is type of pitch control system consists of a patented design including three nosecone pillars and centre bosses. When the turbine reaches its rated rpm, the centrifugal force generated by the blades and blade mounts begin to compress the springs. Consequently, as the blades move outward they are rotated, altering the angle of attack. Turbine rotation is also reduced towards maximum rated power and rpm. Connecting Small-Scale Renewable Embedded Generation (SSREG) to the Grid In our context, the following renewable technologies with a rated power capacity of less than 1 MVA are referred to as small-scale renewable embedded generation (SSREG): rooft op or ground-mounted PV, wind turbines, biomass/gas, landfi ll gas, and small-hydro. NERSA, the National Energy Regulator dif- ferentiates in its Renewable Energy Grid Code three SSREG sub-categories using low voltage connection options, i.e. a nominal voltage ≤ 1 kV: 1. Category A1, includes SSRE generators with a rated power in the range of 0 to 13.8 kVA. 2. Category A2, includes SSRE generators with a rated power in the range greater than 13.8 kVA but less than 100 kVA. 3. Category A3, includes SSRE generators with a rated power in the range of 100 kVA but less than 1 MVA.

We will however refer only to category A1 systems, i.e. SSRE generation with less than 13.8 kWp. We also need to consider that in most areas of South Africa, embedded photovoltaic (PV) generation is currently in higher demand than any other SSRE technology. However, many technical aspects pertaining to grid connection of PV generators also apply to wind turbines. Please note that we are not discussing the important aspect of regulatory rules for a modifi ed net-me- tering scheme (or net-billing scheme), given that these are not yet available/agreed on. Power purchase agreements based on diff erent tariff s for exporting and importing energy from small-scale embedded

123 generation currently only exist for the Cape Town metro, the Nelson Mandela Bay Municipality and the eTh ekwini municipality. We will thus only focus on the general technical aspects of grid interconnection of SSEG as far as these are available/agreed on, considering that technical standard development, following SABS regulations, is still in progress.

For small-scale generators of up to a 100 kWp, i.e. sub-categories A1 and A2, the requirements for compliance are covered in NRS 097 Grid Interconnection of Embedded Generation, Part 2: Small-scale embedded generation series of documents (NRS 097-2). So far only two of the four-part NRS series of quality of supply standards have been developed. Th ese include NRS 097-2-1: Section 1 – Utility Interface. Th e other part of this series that has been developed is the NRS 097–2-2: Section 2 – Embedded Generator Require- ments. Th e other parts of this series to be developed in the future are the: NRS 097-2-3: Section 3– Utility Framework; and NRS 097-2-4: Section 4 – Procedures for Implementation or Application.

THEME 2.1.3 THEME For quality of supply, small-scale embedded generators are also required to comply with standards set in the: 1. Grid Connection Code for Renewable Energy Plants Connected to the Electricity Transmission or the Distribution System in South Africa. 2. NRS 048-2: Electricity Supply - Quality of supply Part 2: Voltage Characteristics, Compatibility Levels, Limits and Assessment Method. 3. NRS 048-4: Electricity Supply - Quality of Supply Part 4: Application Guidelines for Utilities.

Th e above-mentioned municipalities/metros require certifi cation of the embedded generator, i.e. that any installation that is connected to their municipal grids must be certifi ed by an electrical engineer as conforming to requirements outlined in SANS 10142 ‘Wiring of Premises, Low Voltage Installations’. All inverters used in the installation must be compliant with NRS-097-2-1. Th e electrical installation must be done by a qualifi ed electrician (wireman’s licence required!), i.e. SANS 10142 needs to be followed and a Certifi cate of Compliance (CoC) must be issued in order to safely transmit power to all loads and to comply with the utility’s grid-connection requirements. Lastly, to insure the installation against any potential and related risks (in case the house burns down…), the short-term insurance industry probably also requires certifi cation of the embedded generator and the electrical compliance certifi cate.

FIG U RE 22: A TYPICAL CONFIGURATION FOR A CATEGORY A1 INSTALLATION (SCHEMATIC AND SIMPLIFIED)

Utility grid Battery bank Inverter DC DC AC AC Main loads

Wind AC AC Service controller entrance Wind AC AC Backed-up generator subpanel loads

Image source: Please note that AC and DC switch gear and earthing are not indicated!

As already mentioned in student book RET Level 2, earthing of small-scale renewable embedded systems need particular attention (see Tables B.2 to B.5 for earthing and wiring guidelines in the NRS 097). Each installation shall thus have a consumer’s earth terminal (see 3.18 of SANS 10142) at or near the point where the supply cables enter the building or structure. All conductive parts (see 3.29.4 and 6.12.3 in SANS 10142) shall be connected to the consumer’s main earthing terminal. Th e latter shall be earthed by connecting it to the supply earth terminal (see 3.78 in SANS 10142) or the protective conductor (see

124 3.15.8 in SANS 10142) and the earth electrode. Th e eff ectiveness of the supply protective conductor shall be determined in accordance with 8.7.5 in SANS 10142 (see also 6.11.1 in SANS 10142-1:2009). A suitable earth electrode must be installed where no earth electrode exists. When installed, the electrode shall be bonded to the consumer’s earth terminal and to the earthing point of the embedded generator with a conductor of at least half the cross-section of the phase conductor, but with not less than 6 mm2 copper or equivalent conductors. Connecting Large-Scale Wind Power Plants to the Grid National or municipal grid networks are complex systems and the rather vague term ‘power quality’ is oft en used to describe the interaction between power generators/plants, substations, switchgears and consumers. Considering that electrical energy cannot be stored as such, there should ideally always be a balance between power supply and demand. Th is is however hardly achieved and if renewable supply resources are connected to the grid, the matter can get even more complicated because all relevant re-

newable supply resources generate power when the source is available (eg. for wind power, suﬃ cient wind 2.1.3 THEME speeds are needed). Th is characteristic is of little importance when the amount of wind power is modest compared to the installed fossil fuel-based power plants, but if wind power grid penetration is compar- atively large, as is the case in Denmark, Germany and Spain, certain technical challenges need to be addressed. Th ese include electrical grid parameters, such as short-circuit power levels, voltage variations and fl icker, harmonics, frequency, reactive power, protection, network stability, and switching operations and soft starting. Th ese parameters can be limiting factors for the amount of wind power which can be connected to the grid. Transformer, Switchgear and Power Lines Th e main components for grid connection of wind turbines are transformers and substations. Because of potential high losses in low voltage lines, each turbine usually has its own transformer stepping the low voltage level of the turbine generator (<1kV) up to the medium voltage line (<35 kV). Power supply systems can, for example, be divided into three categories: 1. Low voltage system with nominal voltage < 1kV 2. Medium voltage system with nominal voltage above 1kV up to 35kV 3. High voltage system with nominal voltage above 35kV

Your own notes

125 FIGURE 23: SWITCHGEAR AND TRANSFORMER LAYOUT IN A TYPICAL WIND FARM CONFIGURATION (SCHEMATIC)

Gear Softstarter

SCIG Step-up transformer Capacitor bank Switch gear or breaker Tower cable Point of common Grid connection coupling THEME 2.1.3 THEME

Other wind turbine units

Image source: S4GJ/GIZ When the output power lines of the turbine generator come down the turbine tower, their voltage is usually less than the required medium voltage (<35 kV) for the wind farm’s collection system. Th us, a step-up transformer at the base of the tower increases the voltage to meet the <35 kV requirement. Next, and particularly for large wind farms, a separate substation for transformation from the medium voltage system to the high voltage system is required, i.e. stepping up of medium voltage from 132 to 400 kV which resembles the operating range typical for ESKOM’s overhead power lines. At the point of common coupling between the single turbines of a wind farm and the grid, a circuit breaker for the disconnection of the whole wind farm and individual turbines must exist. Oft en this circuit breaker is located at the medium voltage system inside a substation. Modern wind farm designs employ gas-insulated medium-voltage switchgears for this and various other applications. Depending on the operator’s requirements, these type of switchgears ensure that diff erent medium-voltage confi gurations allow individual wind turbines to be safely connected to the wind farm’s own power grid. Th is ensures a safe connection of the sustainably generated power to the high-voltage transmission grid.

FIGU RE 24: UNDERGROUND CABLE CONSTRUCTION

Conductor Insulation Metallic shield

Conductor Insulation Jacket shield shield

Image source: S4GJ/GIZ Modern wind farms oft en use medium voltage underground collection systems, i.e. 35 kV cables that are rugged and suitable for the mechanical requirements associated with direct buried applications. Th ese cables have to withstand changes in ground conditions, such as dry soil that causes cables to run hot, or wet soils where moisture can aff ect the life of the cable. Overhead transmission lines must withstand windy environments and other environmental concerns expected at wind farm locations. Overhead transmission lines form the fi nal connection to the grid.

126 FI G U R E 25: WIND FARM POWER COLLECTION SYSTEM (SCHEMATIC LAYOUT)

Prevailing wind direction

Underground power collection system

between turbines 2.1.3 THEME

Above-ground medium-voltage power collection system

Substation transformer Medium-voltage power collection system Interconnection Inter-turbine switching equipment spacing optimised High-voltage for energy produc- interconnection tion and minimising line to grid turbulence

Existing high-voltage transmission line

Image source: S4GJ/GIZ

127 Exercises

1. Th e illustration below provides a simplifi ed layout of a typical wind turbine drivetrain. Identify each component and explain its function! THEME 2.1.3 THEME

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

128 2. Try to interpret the drawings and the diagram below and describe the working principle of a DC generator (single loop). You may use numbers for the fi ve loop positions. Also indicate missing features and units in the drawing and the diagram. THEME 2.1.3 THEME

3. What are the principal diff erences between a DC motor and a DC generator?

129 4. Draw a hierarchical diagram indicating the diff erent types of DC machines! THEME 2.1.3 THEME

5. Explain why PMDC generators can be considered as separately-excited DC machines!

6. Briefl y describe the diff erences between the two principal types of AC machines, i.e. synchronous and asynchronous generators!

7. Explain the four main control techniques used in wind turbines!

……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

130 8. Explain how various blade angles due to pitch control ensure maximum rated power of a wind generator!

Further Information on the Resource CD

(i) Why large wind turbines need blade pitch control, video. (ii) Power electronics as eﬃ cient interface in dispersed power generation system, Hansen et.al., PDF, 2004 (iii) Kestrel e300i installation and maintenance manual, PDF, (iv) Small-Scale Renewable Embedded Generation: Regulatory Framework for Distributors (Draft ), NERSA, 2014 (v) Small-Scale Renewable Embedded Generation: Regulatory Rules (Consultation Paper), NERSA, 2015 (vi) Grid Connection Code for Renewable Energy Power Plants connected to the Electricity Transmission System or Distribution System in South Africa, NERSA, 2014 (vii) SANS 10142-1:2009, THE WIRING OF PREMISES, PART 1: LOW-VOLTAGE INSTALLA- TIONS, SABS, 2012 (viii) NRS 097-2-1, GRID INTERCONNECTION OF EMBEDDED GENERATION, Part 2: Small-scale embedded generation, Section 1: Utility interface, NRS/ESKOM/SABS, 2010. (ix) Wind Turbine Grid Connection and Interaction, Deutsches Windenergie-Institut GmbH Germany · Tech-wise A/S Denmark · DM Energy United Kingdom, European Communi- ties, 2001

131 THEME 2.1.4 WIND TURBINE TYPES Introduction

Wind turbines can be categorised according to a number of criteria. One obvious criterion is the position of the rotor axis, horizontal or vertical. Historical wind mills can already be diff erentiated using rotor axis position as a measure. With modern wind turbines we distinguish between a horizontal-axis wind turbine (HAWT) and a vertical-axis turbine (VAWT). Each of these two types can be further divided using various sub-criteria which we will deal with in more detail in this theme.

THEME 2.1.4 THEME Keywords

Wind turbine categorisation Horizontal-axis wind turbine (HAWT) Vertical-axis wind turbine (VAWT) Savonius and Darrieus rotors Training kit components Measuring wind speeds

Theme Outcomes

At the end of this theme you should be able to: (i) Diff erentiate between the diff erent wind turbine technologies and designs. (ii) Identify the training kit components of the wind turbine training set. (iii) Measure wind speed in the environment. (iv) Measure wind speed using a wind machine.

Deﬁ nition of Terms Wind Turbine Categorisation Some possible criteria are indicated in Table 1 to help illustrate how to distinguish between diff erent wind turbine types. Th e fi rst criterion in Table 1, the position of the rotor axis, is a very obvious one as we can distinguish between horizontal-axis wind turbines (HAWT) and vertical-axis turbines (VAWT).

132 TA BLE 1: CRITERIA FOR WIND TURBINE CATEGORISATION

Rotor Wind power Tower Generator Criteria Rotor axis Drivetrain orientation control structure technology Options HAWT Upwind Pitch Direct Tubular Asynchronous

VAWT Downwind Stall Gear box Lattice Synchronous

Horizontal-Axis Wind Turbines (HAWT) Th e rotor axis in a HAWT is parallel to the wind stream and the ground (left in Figure 1). Today almost all large commercial grid-connected wind turbines are built with a propeller-type rotor on a horizontal axis, i.e. a horizontal main shaft . Most HAWTs built today have three blades. Th e rotor blades convert

the linear motion of the wind into rotational energy that can be used to drive a generator. Th e conversion 2.1.4 THEME of linear motion into rotational motion is based on the Bernoulli principle, i.e. wind passes over both surfaces of the air foil shaped blade but passes more rapidly over the longer (upper) side of the air foil, thus creating a lower-pressure area above the air foil. Th e pressure diff erential between top and bottom surfaces results in a lift force. In an aircraft wing, the lift force causes the air foil shaped wings to rise, lift ing the aircraft off the ground. Since the blades of a wind turbine are constrained to move in a plane with the hub as its centre, the lift force causes the blades to rotate around the hub of the rotor. In addition to the lift force, a drag force perpendicular to the lift force impedes rotor rotation. A prime objective in HAWT rotor blade design is to ensure that the blades have a relatively high lift -to-drag ratio. Th is ratio can be varied along the length of the blades to optimise the energy output at various wind speeds.

FIGURE 1: POSITION OF PRINCIPAL WIND TURBINE COMPONENTS IN HAWTS AND VAWTS

Rotor diameter (D) Rotor

Gear box Rotor

Generator Rotor diameter (D) diameter Rotor Tower Tower Rotor height (H) Hub height Hub height

Gear box Generator

Image source: S4GJ/GIZ

Vertical-Axis Wind Turbines (VAWT) Th e axis of rotation in a VAWT is perpendicular to the wind stream and the ground. Th e VAWT working principal is similar to the one of the classical Persian wind mills used, i.e. the wind stream is at a right angle (perpendicular) to their rotational axis (shaft s). Modern VAWTs can be further divided into two major categories: the lift -force-driven Darrieus type turbines and the drag-force-driven Savonius type turbines.

133 FIG U RE 2: PRINCIPAL DESIGN COMPARISON OF SAVONIUS AND DARRIEUS ROTORS

Savonius type THEME 2.1.4 THEME

Darrieus type

Image source: S4GJ/GIZ

FI G U R E 3: COMPARISON OF SAVONIUS AND DARRIEUS ROTOR WORKING PRINCIPALS (SCHEMATIC)

Direction of rotation Lift force

e D

Lift force

Wind

Image source: S4GJ/GIZ Design comparison of Darrieus type rotor using cup shapes to generate drag forces (left ) and lift force driven Savonius rotor with air foil blades (right).

Since drag-based designs rotate with the wind, they cannot move faster than the wind, whereas lift -based designs can move faster than the wind. Th e drag design is very rugged and therefore suitable for diffi cult situations - however the effi ciency of wind power conversion in drag devices is approximately only half of the more effi cient lift design found in Darrieus turbines. Th e Darrieus turbines are unable to self-start; a mechanism is needed to start them before they can generate power. Currently, the trend all around the world is to combine the two mechanisms on the same axis to utilise the Savonius’ drag ability which then provides suffi cient torque to start a Darrieus wind turbine. In other words, these turbines are combined in an eff ort to minimise the limitations of each of them.

134 FIGURE 4: PROPOSED SETUPS FOR COMBINED SAVONIUS-DARRIEUS ROTORS (SCHEMATIC) THEME 2.1.4 THEME

Image source: S4GJ/GIZ Proposed setups for hybrid Savonius-Darrieus rotors. On the left : Savonius rotor either on the top or bottom of the H-type Darrieus rotor. On the right: Savonius rotor in the middle of the H-type Darrieus rotor.

Your own notes

135 Experiments

For training to be truly eff ective, it is necessary to practically apply your knowledge in hands-on experiments and real-world installations. Given that these are oft en diﬃ cult to realise in some TVET colleges, we can off er you some resources and equipment for practical work. Components required for practical activities range from low-cost components that can be used to build and experiment with simple HAWT and VAWT models, to commercial training kits and vocational training versions to simulate real wind turbine systems. We will introduce you to all of the above in Topic 4 and in more detail, but we suggest that you already start with some practical activities which are based on commercial training kits, such as the IKS Windtrainer Junior set or the leXsolar-Wind training set (one of the two options are available at your college for RET Level 4). Both types of training sets include modular experiments designed to demonstrate important aspects of wind turbine systems covered in this textbook, albeit on a miniature scale. THEME 2.1.4 THEME Training Kit Components Before you start with the fi rst practical activities, we recommend that you familiarise yourself with the training kit and identify all components of the wind turbine training set. One of the two options are available at your college, either the IKS Windtrainer Junior set or the leXsolar-Wind training set. Please consult the student manual of your respective training set for more information and descriptions of the components, as these diff er in respect to their names, forms and functions, and subsequently to their operating instructions. We will now briefl y describe the components of each training set and show you some images illustrating them. Please note that all components, particularly the wind machines and the ! rotor parts, need to be handled with care! Please also note that the rotor must not be touched during rotation/movement due to the risk of injury! IKS Windtrainer Junior Set Th eIKS Windtrainer Junior set comes in a white suitcase with a shaped foam inlet for all components except for the base board, which you will fi nd in the lid together with the instruction manual and the CD. Th e base board houses the load, resistor and storage boxes, the two multi-meters, the 12 V wind machine with its power supply and the small wind power generator. Th e latter resembles a tiny HAWT for mounting 2, 3, and 4 blades. You will fi nd a total of eight blades included, 4x straight and 4x convex. You will also fi nd eight 2 mm connector cables, a screwdriver and an anemometer. Your IKS Windtrainer Junior set does not provide you with a Savonius rotor, this optional extension was not included.

Your own notes

136 FI G U R E 5: COMPONENTS OF THE IKS WINDTRAINER JUNIOR SET IN THEIR STORAGE POSITION THEME 2.1.4 THEME

Image source: S4GJ/GIZ

FIGURE 6: IKS WINDTRAINER JUNIOR SET: SOME ASSEMBLED COMPONENTS

Image source: S4GJ/GIZ Please consult the IKS instruction manual for component assembly of each experiment. leXsolar-Wind Training Set Th e leXsolar-Wind training set comes in an aluminium suitcase with three shaped foam inlets housing all components. A custom-designed breadboard is the construction base for up to three components which can be plugged in a series and parallel connection. A 12 V wind machine is powered by a compact and intuitively usable DC power module (output 0-12 V adjustable in 0.5 V steps) to control the wind conditions in the experiments. Th e rotor set entails eight blades and there is a hub for four blades with a pitch angle of 25° and hubs for three blades with pitch angles of 20°, 25°, 30°, 50° and 90°. Th e little blue wind turbine, resembling a miniature HAWT model, needs to be connected into the turbine module plate, which has an angle scale printed on top of it. In addition to the miniature HAWT model, the leX-

137 solar-Wind training set also off ers a Savonius rotor which is already connected to a module plate. Two digital multimeter and various loads, e.g. a motor module, a light bulb, an LED-module, and a buzzer module are provided. Further, two resistor modules, one with two potentiometers (a 0-100 Ω-potentiometer and a 0-1kΩ-potentiometer) and a conventional 33 Ω resistor module are available, as well as a capacitor module (220 mF and 2.5 V). A diode is supplied to allow current to pass in one direction only and an anemometer to measure wind speed. Lastly, an optical tachometer as a ‘round per minute (rpm) counter’ and four 4 mm connector cables complete the training set.

F I G U R E 7: COMPONENTS OF THE LEXSOLAR-WIND TRAINING SET IN THEIR STORAGE POSITION THEME 2.1.4 THEME

Image source: S4GJ/GIZ Please consult the leXsolar instruction manual for component assembly of each experiment.

FIGU RE 8: TWO DIFFERENT ANEMOMETER TYPES

Image source: S4GJ/GIZ Th e anemometer in the IKS Windtrainer Junior set (left ) has a Savorius type of rotor, while the anemometer in the leXsolar-Wind set (right) uses a horizontal-axis rotor to measure wind speed.

138 TA BL E 2: SYMBOLS FOR EXPERIMENTAL SETUP BY THE LEXSOLAR- WIND TRAINING SET

Modules Symbols

Construction base

Wind machine (12V)

Wind turbine module

(HAWT model) 2.1.4 THEME

Savonius rotor (VAWT model)

DC power module, 0-12 V adjustable in V 0.5 V steps

Multimeter V A

Motor module

Light bulb module

LED module

Buzzer module

Potentiometer module

Resistor module

Capacitor module

Diode module

Anemometer

139 EXPERIMENT 1: MEASURING WIND SPEED IN THE ENVIRONMENT

Th is experiment is designed to generate a fi rst idea of the dimension, the temporal and local diff erences of wind speed. Assignment 1: Familiarise yourself with the anemometer. Please consider that you may have either the IKS Windtrainer Junior set or the leXsolar-Wind training set available at your college, so you will have only one of the two diff erent anemometer types (Figure 8). Please consult the student manual of your respective training set for more information and a description of the anemometer, as these two handheld gauges diff er in respect to their form and function, and subsequently to their operat-

THEME 2.1.4 THEME ing instructions.

Assignment 2: Use the available anemometer and measure the wind speed at 6 to 8 diff erent locations on your campus at diff erent times. Document your measurements in the table below similarly to the given examples:

No Location on campus Date/Time Wind speed (m/s) 1 GATE 8:00/9:00/10:00/12:00/14:00 6, 3, 3, 4, 1 2 OUTSIDE WORKSHOP 8:30/9:30/10:30/12:30/14:30 6.5, 3.2, 3.4, 4.5, 2

Assignment 3: Answer the following three questions below!

3.1 Specify the overall highest and lowest wind speed indicated in your table, and calculate the ratio of these two values!

Example: vmax = 6.5 m/s, vmin = 1 m/s, vmax / vmin = 6.5

vmax = …. m/s, vmin = …. m/s, vmax / vmin = ….

140 3.2 Compare the measured wind speed per location, i.e. wind speed measured at the same location but at diff erent times!

Example: Location: GATE, vmax = 6 m/s, vmin = 1 m/s, vmax / vmin = 6

Location: ………………………….., vmax = …. m/s, vmin = …. m/s, vmax / vmin = ….

…………………………………………………………………………………… ……………………………………………………………………………………… THEME 2.1.4 THEME ………………………………………………………………………………………

1 3 3.3 Recall the three factors in formula (6), i.e. Pwind = 2 x ρ x A x (v ) and consider that wind velocity (v) is the most crucial factor in the formula. Th us, power output of a wind turbine rotor is proportional to the cube (third power) of the wind speed. In other words, if velocity of wind doubles, power increases by a factor of eight (23 = 2 x 2 x 2 = 8). Use four of your

vmax / vmin values (ratios) and calculate the cube (third power) of the wind speeds to understand better how velocity infl uences power output of a wind turbine.

Examples: vmax / vmin values = 2, 3, 4, etc. 3 vmax / vmin = 2 = 2 x 2 x 2 = 8 3 vmax / vmin = 3 = 2 x 2 x 2 = 27 3 vmax / vmin = 4 = 2 x 2 x 2 = 64

141 EXPERIMENT 2: MEASURING WIND SPEED USING A WIND MACHINE

Th is experiment is designed to determine the performance values of the respective wind machines, i.e. which kind of wind speeds correspond to certain ratings of the DC regulator, either by 1 V steps or along given scale division at the control knob (potentiometer settings). Th ese measurements will characterise the respective wind machine and the resulting diagram can be used in all subsequent experiments as reference values. Assignment 1: Familiarise yourself with the anemometer and the wind machine. Please consider that you may have either the IKS Windtrainer Junior set or the leXsolar-Wind training set available at your

THEME 2.1.4 THEME college, i.e. only one of the two diff erent wind machine types (Figure 9). Please consult the student manual of your respective training set for more information and a description of the anemometer and the wind machine, as these diff er in respect to their form and function, and subsequently in their operating instructions.

FIGURE 9: TWO DIFFERENT WIND MACHINE TYPES

Image source: S4GJ/GIZ

Th e wind machine in the IKS Windtrainer Junior set (left ) is a hairdryer type of machine, while the leXsolar-Wind set (right) uses a ventilator type of machine to generate appropriate wind speeds.

Assignment 2: Use the following setup and the available anemometer to measure wind speed either at 12 diff erent 1 V steps (leXsolar-Wind set) or along the given scale division (1-10) at the control knob at the IKS Windtrainer Junior wind machine. Document your measurements in the table and use the data to create a graph in the given diagram.

142 FIGURE 10: SETUP FOR EXPERIMENT 2 (SCHEMATIC) THEME 2.1.4 THEME

Image source: S4GJ/GIZ Please consult the student manual of your respective training set for more information on the setup, e.g. distance between wind machine and anemometer.

Use the table below to document your measurements and use the diagram to draw a graph line linking the power settings with the corresponding wind speed.

Divisions 1 2 3 4 5 6 7 8 9 10 11 12 Wind speed (m/s)

Wind speed (m/s) 12

0 1 2 3 4 5 6 7 8 9 10 11 12 Potentiometer settings/ Divisions on power module

Image source: S4GJ/GIZ

143 Exercises

1. Which criteria can be used to diff erentiate between diff erent wind turbine designs?

2. Indicate the position of the main wind turbine components in both horizontal-axis wind tur-

THEME 2.1.4 THEME bines (HAWT) and vertical-axis turbines (VAWT) in a drawing!

3. Compare the design of Darrieus and Savonius types of VAWT rotors and explain what kind of forces each rotor type uses!

144 4. A Savonius drag type rotor can be combined with a Darrieus type of rotor. Please explain why this makes sense!

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… THEME 2.1.4 THEME

Further Information on the Resource CD

(i) Technical introduction on Darrieus wind turbine, . (ii) Vertical Axis Wind Turbines, M. Ragheb, 2015. (iii) Rural electrifi cation and small wind turbines, Position Paper 2012. (iv) Water pumping solutions, Kestrel, 2016. (v) e300i, Installation and Maintenance Manual, Kestrel, 2016.

Your own notes

145 146 Unit 2.2 Unit 2.2 covers the following four themes: four following covers the Unit 2.2 Themes in this Unit able you to: be should unit, end ofAt this the Unit Outcomes better. principles functional their to understand (e–mobility). systems It thereforeimportant is transport modern all almost and applications electronic portable all in role play asignificant technologies cell fuel and Battery fuels. and fossil dam, in a storedwater gas, pressurised/liquefied capacitors, but also hydrogen (fuel and cells), conversions batteries include out and these carry that or devices systems substances, comprise carriers of form energy. Such energy another into converted be can carrier’ or ‘energy vector’ ‘energy an stored in conversion and ofstorage energy energy. You that know already energy with context in appears of electrochemistry applications important most One of the particles. of charged transportation and separation i.e. processes, electrical and chemical on combined based are technologies These technologies. cell fuel and of basicprinciples battery the explains unit briefly This Introduction BA 2.2 UNIT (xiii) (xi) (xii) (x) (ix) (viii) (vii) (vi) (v) (iv) Theme 2.2.2 Electrochemical Processes in Fuel Cells in Fuel Processes Electrochemical 2.2.2 Theme Batteries in Processes Electrochemical 2.2.1 Theme (iii) (ii) (i) SIC PRINCIPLES OF BATTERY AND FUEL CELL TECHNOLOGIES CELL FUEL AND BATTERY OF PRINCIPLES SIC

Me Me Id Ex advantageous. is systems renewable energy Di Sk Ex Ex electricity. generate De Ex Di Ex De entify the training kit components for hydrogen and fuel cell experiments. cell components for kit fuel hydrogen and training the entify etch and explain a proton exchange membrane (PEM) fuel cell. (PEM) aprotonmembrane fuel exchange explain and etch scuss the principles of water electrolysis for hydrogen generation and why the association with with association for why hydrogen the and generation of electrolysis water principles the scuss fferentiate between various lead-acid battery types and explain their functional differences. functional their andexplain types battery lead-acid various between fferentiate plain why energy generation through fuel cells can be regarded as a climate–friendly technology. aclimate–friendly as regarded be can cells fuel through generation why energy plain plain why fuel cells are also referred to as electrochemical energy converters. energy electrochemical to as referred also are cells why fuel plain cell. of afuel cathode and anode at the occurring reactions electrochemical two the plain of batteries. lead-acid chemistry the plain plain general battery design, componentsconstruction. and design, battery general plain scribe the electrochemical process where hydrogen and oxygen interact within a fuel cell to cell afuel within interact oxygen where hydrogen and process electrochemical the scribe scribe the basic electrochemical processes that take place in batteries. in place take that processes electrochemical basic the scribe asure the quantities of gas produced per unit time depending on current. depending time unit produced per of gas quantities the asure asure the volume ratio of the gases produced. gases of the volume ratio the asure

THEME 2.2.1 ELECTROCHEMICAL PROCESSES IN BATTERIES

Introduction

Th is theme will briefl y introduce you to the basic electrochemical reactions and principles responsible for generating an electric current. We will introduce you to the main types of batteries and explain their basic principles of operation. THEME 2.2.1 Keywords

Battery Battery components Electrode Anode Cathode Electrolyte Atom Ion Cations Anions Chemical reaction Redox reactions Two half (reactions) make one (redox reaction) Voltaic pile: the ancestor of modern electrical batteries Electrochemical processes in the voltaic pile/galvanic cell Primary cells Zinc dry cells Alkaline dry cells Other dry cell types Secondary cells Lead-acid storage cells Other lead-acid battery types Batteries: general principle of operation Battery vs fuel cell

Theme Outcomes

At the end of this theme you should be able to: (i) Describe the basic electrochemical processes that take place in batteries. (ii) Explain general battery design, components and construction. (iii) Diff erentiate between various lead-acid battery types and explain their functional diff erences. (iv) Explain the chemistry of lead-acid batteries.

Deﬁ nition of Terms

Th e processes by which batteries provide an electric current diff er slightly from battery to battery. Th e basic electrochemical reactions however appear to be rather similar, but before we can explain and ex- pose you to the chemistry in battery operation, we need to introduce you to some new technical terms. Electrochemistry has an extensive vocabulary and a signifi cant amount of jargon. We will discuss some basic technical terms concerned with composition, structure and properties of batteries, as well as the changes they undergo during chemical reactions.

147 Battery Th e word ‘battery’ was used to describe any series of similar objects grouped together to perform a function (a battery of something, e.g. a battery of pain killers or an artillery battery). In 1749, Benjamin Franklin, one of the so-called ‘founding fathers’ of the United States and a renowned polymath, used the term to describe a series of capacitors he had linked together for his physics experiments. Later, the term would be used for electrochemical cells linked together for the purpose of providing electric power (see also ‘voltaic pile’).

Battery Components In batteries chemical reactions can create an electric current in a circuit. All batteries are made up of three basic components: two electrodes and a substance called electrolyte (see Figure 1). Th is arrangement, i.e. two electrodes separated by an electrolyte, is the basic setup required for a battery to conduct

THEME 2.2.1 an electrical current through a circuit.

FIGURE 1: THE THREE BASIC COMPONENTS OF A BATTERY

Electrode

Cathode (+)

Anode (-)

Electrolyte

Image source: GIZ/S4GJ

Electrode Electrodes are terminals through which an electric current can enter or leave a battery. Two types of terminals can be diff erentiated: a negative terminal (anode) and a positive terminal (cathode).

Anode Th e anode is the negative terminal from which electrons fl ow if a battery is connected to a circuit. In a battery, the chemical reaction between the anode and electrolyte causes a buildup of electrons (negative charge) in the anode. Th e negative electric charge moves to the cathode, but cannot pass through the electrolyte.

Cathode Th e positive terminal into which electrons fl ow if the battery is connected to a circuit. In batteries, the chemical reaction in or around the cathode uses the electrons provided via the anode. Th e only way for the electric charge to get to the cathode is through an external circuit, e.g. via a wire and/or a load.

148 Electrolyte An electrolyte1 is a substance, oft en a liquid solution, a gel or a paste that is capable of transporting electrically charged particles. Th e electrolyte also inhibits the fl ow of electrons between the anode and cathode so that the charge fl ows more easily through the external circuit rather than through the electrolyte.

Atom All matter is made up of fundamental building blocks known as atoms. Each atom consists of protons, neutrons and electrons (see Figure 2). Protons and neutrons form the nucleus or the centre of an atom. Electrons are constantly spinning in shells or orbitals surrounding the nucleus of an atom. Electrons and protons carry a charge. Th e charge of an electron is negative, while a proton carries a positive charge of the same magnitude as the electron. Electric charge, either negative or positive, is the most basic quantity in an electric circuit. THEME 2.2.1 FIG U RE 2: SIMPLIFIED STRUCTURE OF AN ATOM

q+q+ PROTONSProtons q-q- ELECTRONSElectrons q+ NEUTRONSNeutrons q+

q- q-

Each atom consists of electrons, protons and neutrons. The charge of an electron is negative and a proton carries a positive charge of the same magnitude as the electron.

Image source: GIZ/S4GJ

1 Th e term ‘electrolytes’ is also used for minerals in your body fl uids. Maintaining the right balance of electrolytes helps your body’s blood chemistry, muscle action and other processes. Sodium (Na), calcium (Ca), potassium (K), chlorine (Cl), phosphate (Ph) and magnesium (Mg) are all electrolytes. You get them from the foods you eat and the fl uids you drink.

149 Ion In an atom, the number of protons usually does not change. Th e number of electrons however, might change in an atom. Fewer or extra electrons can create an electrically charged atom called an ‘ion’. Two types of ions can be diff erentiated: a cation (positive ion) and an anion (negative ion). Th e term ‘ion’ was introduced by the English scientist Michael Faraday. It stems from the Greek word ‘ion’ meaning ‘go or move’, so called because ions move towards the electrode of opposite charge.

Cations A cation is an ion, an electrically charged particle that has fewer electrons and thus carries a positive charge. Table salt, i.e. sodium chloride (NaCl), for example, dissolves in water to form sodium cations (Na+) and chloride anions (Cl-). Th e sodium cation, denoted as Na+ carries a single positive charge: the sodium cation (Na+) lost or donated one of its electrons to the chloride anion (Cl-). Another example is 2+

THEME 2.2.1 the zinc cation, denoted as Zn . Th is cation carries a twofold positive charge, i.e. the neutral zinc atom (Zn) lost or donated two of its electrons in a chemical reaction.

Anions Anions have extra electrons that create a negative charge. Th e chloride anion (Cl-) or the hydroxide anion (OH-) both carry a single positive charge as each of them have gained one additional electron. Another 2- example for an anion is the sulphate anion SO4 which carries a twofold negative charge. Th e sulphate anion is a salt of the sulfuric acid H2SO4. Th is acid is highly soluble in water and dissociates into two ions + 2- 2- as indicated in the following equation: H2SO4  2H + SO4 , i.e. the sulphate anion SO4 has gained two additional electrons in a chemical reaction. Th e following symbols are used to diff erentiate between diff erent types of reactions: Th e arrow symbol pointing to the right (→) is used to denote a net forward reaction and usually reads as ‘yields’. Th e double arrow symbol ⇄( ) is used to denote a reaction in both directions.

FI G U R E 3: SODIUM CATIONS (Na+) AND CHLORIDE ANIONS (Cl-)

Sodium Chlorine

Na Cl

Na+ Cl-

Image source: GIZ/S4GJ Th e salt sodium chloride (NaCl) is comprised of two atoms: sodium (Na) and chloride (Cl). Th e salt forms ions in water by sodium losing/donating one electron and chloride gaining this electron. Th e sodium cation (Na+) carries a single positive charge and the chloride anion (Cl-) carries a single negative charge.

150 Chemical Reaction A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more diff erent substances, the products. Equations are the symbolic representation of a chemical reaction in the form of symbols for reactants and products. In equations, each individual reactant and product is separated from others by a plus sign (+). Th e reactant entities are placed on the left -hand side and the product entities on the right-hand side of the equation. A simple example is the equation for the reaction of table salt with water - sodium chloride (NaCl) dissolving in water (H2O) can be denoted as:

+ - H2O (l) + NaCl (s) → Na (aq) + Cl (aq) + H2O (l)

Th e physical state of chemicals is also very commonly stated in parentheses aft er the chemical symbol, especially for ionic reactions. When stating physical state, (s) denotes a solid, (l) denotes a liquid, (g) de-

notes a gas and (aq) denotes an aqueous solution. THEME 2.2.1 Table salt (NaCl) is soluble in water. NaCl dissolves into separate Na+ and Cl- ions. A hydration shell is formed around these ions and we can thus say the salt is dissolved. Th is equation could be read as: water plus sodium chloride yields sodium and chloride ions both covered by hydration shells (water molecules).

FIGURE 4: TABLE SALT (NaCl) DISSOLVES IN WATER

a) b) c)

Image source: GIZ/S4GJ Sodium and chloride ions separate and hydration shells (water molecules) are formed around the ions due to electrostatic interactions (charge–based attractions).

151

FI G U R E 5: AN ENLARGED IMAGE OF FIGURE 4 C

H 0 + + -

2 0

+ H -

2 + 0

H Na +

+ 0 H 2 - - 2 + H H + 2- 2 + + 2 - 0 H H 0 - H+ 0 + 0 H + H+ H H +

+ H

- H + 2 - 0 0 Cl 2 -

+ H

THEME 2.2.1

H +

+ + 2 2 -

Image source: GIZ/S4GJ Water molecules form hydration shells around sodium cations (Na+) and chloride anions (Cl-). Th is is the contemporary atomic understanding of a salt (NaCl) dissolved in water.

Redox Reactions Chemical reactions that involve charge transfer, i.e. electron transfer similar to the previous example where sodium transfers an electron to chloride and both atoms turn into ions, are termed oxidation/ reduction reactions. Oxidation/reduction reactions, or redox reactions in short, involve a transfer of negative charge (electrons) from one atom to another. In terms of electrochemistry, the following defi nition applies: Loss of electrons is called oxidation, and gain of electrons is called reduction. Ways to remember oxidation/reduction as chemical reactions include two mnemonic aids. Th e fi rst one is: OIL RIG, meaning oxidation is loss and reduction is gain. Th e second mnemonic aid is: LEO says GER, meaning losing electrons = oxidation and gaining electrons = reduction.

Two Half (Reactions) make One (Redox Reaction) Oxidation and reduction reactions cannot be carried out separately. Th ey always appear together in a chemical reaction. Subsequently, a redox reaction includes a reducing agent and an oxidising agent. Both form a redox couple which can be described as:

1st half reaction at the anode: reducing agent → oxidising agent + electrons (e–) 2nd half reaction at the cathode: oxidising agent + electrons (e–) → reducing agent

Each one of the two reactions is called a half-reaction and together they form a redox couple. In other words, oxidising agents gain electrons and are thus reduced. Reducing agents lose electrons and are thus oxidised.

Th e reaction where sodium chloride (NaCl) dissolves in water (H2O), denoted as

+ - H2O (l) + NaCl (s) → Na (aq) + Cl (aq) + H2O (l)

can be regarded as a simple redox couple if we consider that sodium and chloride carry no charge as table salt (NaCl). Th is situation changes when table salt (NaCl) dissolves in water. When table salt dissolves, sodium (Na) loses/donates one electron to chloride (Cl) and subsequently carries a charge of plus one (Na+) while chloride (Cl) gains one electron from sodium (Na) and subsequently carries a charge of minus one (Cl-). Th erefore, one could say that sodium (Na) was oxidised (loss of electrons) by the oxidising agent chloride (Cl). Th is is called the fi rst half-reaction and Cl was reduced (gain of electrons) by the reducing agent Na. Similar types of redox reactions take place in batteries.

152 Voltaic Pile: The Ancestor of Modern Electrical Batteries In Th eme 1.2.1 we introduced you to the voltaic pile, the fi rst electrical battery invented by A. Volta in 1799 (see Figure 6). Th is early battery consisted of stacked pairs of alternating copper (Cu) and zinc (Zn) discs which served as electrodes separated by cloth or cardboard soaked in brine, a solution of table salt

(sodium chloride, NaCl) or diluted sulphuric acid (H2SO4). Th is solution acts as an electrolyte to increase conductivity. Th e pile produced an electric current and can be considered the fi rst electrochemical cell.

FIGURE 6: THE VOLTA PILE (SCHEMATIC)

- Zn - THEME 2.2.1 Electrolyte Cu +

Zn - one voltaic cell Cu + +

Image source: GIZ/S4GJ Th e Volta pile consists of stacked pairs of alternating copper (orange) and zinc (grey) discs (electrodes) separated by an electrolyte (blue).

Electrochemical Processes in the Voltaic Pile/Galvanic Cell (simpliﬁ ed) Th e contemporary, atomic understanding of a voltaic cell element with zinc and copper electrodes separated by an electrolyte is the following: When the cell provides an electrical current through an external circuit, the metallic zinc (Zn) at the surface of the zinc electrode (anode, negative terminal) dissolves in the form of electrically charged ions (Zn2++, Zn-cation) and two negatively charged electrons (2e–) that enter into the electrolyte. Th is type of chemical reaction is called oxidation and takes place at the negative terminal, the anode. Remember, oxidation is a chemical reaction where electrons are released. Th is process is called the st1 half reaction of the redox couple and can be expressed by the following equation:

2+ – Zn → Zn (aq) + 2e

2+ While the zinc cations (Zn ) enter the electrolyte (H2SO4 , diluted sulphuric acid), two positively charged + + 2- e– hydrogen ions (H ) from the electrolyte (H2SO4  2H + SO4 ) combine with the two electrons (2 ) at the copper (Cu) electrode (cathode, positive terminal) and form an uncharged hydrogen molecule (H2), a gas. Th is reaction is called reduction and takes place at the positive terminal, the cathode. Reductions are chemical reactions where electrons are gained. Th e hydrogen molecules formed on the surface of the copper by reduction ultimately bubble away as hydrogen gas (H2). Th is process is called the 2nd half reaction of the redox couple and can be expressed by the following equation:2

+ – 2 2H (aq) + 2e  H2 (g)

Remember: (s), (aq), (l) and (g) in chemical equations refer to (s) = solid, (aq) = aqueous solution (dissolved in water), (l) = liquid, and (g) = gas.

2 + – Or more accurately: 2H3O (aq) + 2e  H2 (g) + 2H2O (l) 153 F I G U R E 7: SIMPLIFIED ELECTROCHEMICAL PROCESSES IN A VOLTAIC PILE / GALVANIC CELL

-0,76V

Zn 2e-

2+ -

THEME 2.2.1 Zn Zn +2e

+ 2- H2SO4 2H +SO4 + - 2H +2e H2 Cu +

0 V

Image source: GIZ/S4GJ Voltaic cells, also called galvanic cells, are simple electrochemical devices (batteries) that generate an electric current by using two diff erent metals that diff er in their tendency to lose electrons. For example, zinc (Zn) tends to lose electrons more easily than copper (Cu), so by placing zinc and copper metal in an

electrolyte (H2SO4, diluted sulphuric acid), a charge fl ows through a wire from the zinc electrode (anode) to the copper electrode (cathode).

Primary Cells In primary cells electrochemical reactions are irreversible (not reversible). During discharging the chemical components are permanently changed and an electric current is released until the original battery compounds are completely exhausted. Th us, these type of cells can be used only once (throwaway cells).

Zinc Dry Cells Th e most well-known primary battery has long been the common dry cell (zinc-carbon cell) which is still widely used to power common electric and electronic devices (fl ashlight battery). Modern dry cells are based on a battery unit invented by Georges Leclanché in 1866. Despite its name, the zinc-carbon dry cell

is not really dry. Th e electrolyte is a wet paste or non-fl owing jelly containing zinc chloride (ZnCl2), ammonium chloride (NH4Cl), manganese dioxide (MnO2), starch, graphite and water. Th e anode is a zinc container covered with an insulating fabric and the cathode is the carbon rod at the centre of the cell (see Figure 8). A fully charged (unused) dry cell delivers around 1.5 V.

154 FIGU RE 8: THE ZINC-CARBON DRY CELL (SCHEMATIC)

Zinc case Carbon rod

Protective THEME 2.2.1 plastic PowderedPowered carbon tube and manganese dioxide Fabric bag

Jelly containing ammonium chloride -

Image source: GIZ/S4GJ

Th e following redox reactions take place at the electrodes of the zinc-carbon cell:

Th e 1 st half reaction at the anode (negative terminal): Zn → Zn2+ + 2e– (0.74 V)

Th e 2 nd half reaction at the cathode (positive terminal): + – 2MnO2 + 2NH4 + 2e → Mn2O3 + 2NH3 + H2O (0.76 V)

Th e chemistry of this cell is more complicated than it would appear from these equations, and there are many side reactions which we do not need to consider for our purposes here. Th ese types of cells have a limited shelf life due to self-discharge. In some of the older types of zinc dry cells an attack by the acidic + ammonium ion (NH4 ) would release hydrogen gas, causing the battery to swell and rupture, oft en ruin- ing a fl ashlight or other electric devices.

Alkaline Dry Cells A more modern dry cell version introduced in 1949, is the alkaline dry cell. Th e alkaline dry cell is more expensive than a zinc-carbon cell, but it is also more eﬃ cient. Zinc is again used as reducing agent at the anode and manganese dioxide acts as the oxidising agent at the cathode. Th e electrolyte however is 40% potassium hydroxide (KOH) saturated with zinc oxide (ZnO) which permits the cell to deliver higher currents and avoids the corrosive eff ects of the acidic ammonium on the zinc. Th e cathode is a paste of manganese dioxide (MnO2), graphite and water. A plastic sleeve separates the inner steel case from the outer steel jacket. Nominal cell voltage is again 1.5 V.

155 Th e following redox reactions take place at the electrodes of the alkaline dry cell:

Th e 1 st half reaction at the anode (negative terminal): - + – Zn + 2OH → Zn2 + H2O + 2e (1.25 V)

Th e 2 nd half reaction at the cathode (positive terminal): – - 2MnO2 + H2O + 2e → Mn2O3 + 2OH (0.15 V)

FIGURE 9: ALKALINE BUTTON CELL (SCHEMATIC) THEME 2.2.1

Anode cap Cell case

Anode Gasket (Zn plus KOH electrolyte)

Separator

Cathode (MnO2 plus conductor)

Image source: GIZ/S4GJ Apart from the diff erent type of casing the chemistry of the alkaline button cell is the same as that of the standard alkaline dry cell.

Other Dry Cell Types Th ere are many more types of primary cells available which use diff erent components as reducing agent at the anode and as the oxidising agent at the cathode:

(i) Lithium dry cells use Li as reducing agent at the anode, MnO2 as the oxidising agent at the cathode and KOH as electrolyte. Th is is only one of a whole family of lithium-based batteries.

Others are: Li/SO2 , Li/SOCl2 , Li/CuO, Li-poly(vinyl pyridine)/I2 solid electrolyte. Lithium batteries will most probably replace most other types of batteries with a whole new range of high-power, low-mass cells. In the next years we could see substantial development in this area. Nominal cell voltage is around 3.0 V. (ii) Mercury batteries use a zinc-mercury amalgam as reducing agent at the anode while the cathode is a paste of mercury oxide (HgO), graphite and water. Th e mercury cell, developed in 1942, is usually produced as a button dry cell devised for use in small appliances such as watches. Th ese cells deliver only around 1.3 V, but they have the advantage of maintaining a fairly constant voltage during their lifetime. Th eir high toxicity (mercury) however is a huge environmental burden.

(iii) Silver oxide button batteries use Zn, Ag2O and KOH, and are similar to the mercury and alkaline manganese cells. Th ey have a very high storage capacity but are expensive because of the use of silver oxide.

156 Secondary Cells Primary cells as exemplifi ed above cannot be recharged eﬃ ciently. Th us, the amount of power they can deliver is limited to the chemical energy obtainable from the reactants that were placed in the cell at the time of its manufacture. Conversely, electrochemical reactions in secondary cells are reversible and the original chemical compounds can be reconstituted or reactivated by the application of an electrical potential between the cell electrodes. Consequently, secondary cells can be discharged and recharged many times.

Lead-Acid Storage Cells Th e most well-known rechargeable storage cell is the lead-acid cell, which was invented by Gaston Planté in 1859 and is still the most widely used device of its type. Th e anode consists of a lead grid fi lled with porous lead (Pb). Th e cathode is a lead grid fi lled with lead dioxide (PbO2). Th e electrolyte is a liquid

(pure H2O) containing 38% (by mass) sulfuric acid (H2SO4). THEME 2.2.1

FIGURE 10 – 16: LEAD-ACID BATTERY DISCHARGING VIA CONDUCTION BETWEEN TERMINALS

Pb PbO2

Negative Positive electrode: electrode: Porous lead Lead-dioxide H2SO4 H2O

Electrolyte: Sulfuric acid, diluted in pure water

Image source: GIZ/S4GJ

Th e conducting terminals are made of porous lead (Pb) and lead dioxide (PbO2).

FIGU RE 11

+ + H Pb H PbO H+ 2 H+ -2 SO4 -2 SO4

H2O

Image source: GIZ/S4GJ + Th e electrolyte, i.e. sulfuric acid (H2SO4) contains aqueous cations (H , hydrogen protons) and anions 2- (SO4 , sulphate anions). Th ese ions react with the electrode materials (Pb and PbO2). 157 FIGURE 12

0 Lead Pb Sulfuric acid electrolyte electrode Pb0 H+ H+ Pb0 - -2 -2 0 SO SO4 - Pb 4 H+ Pb0

Pb0 H+ H2O Pb0 THEME 2.2.1

Image source: GIZ/S4GJ 2- Th e aqueous sulphate anions (SO4 ) react with the anode material (Pb = reducing agent) and as a result, lead as the reducing agent loses two electrons and is thus oxidised. Th e ionised lead becomes a cation 2+ 2- (Pb ) and forms an ionic bond with the sulphate anion (SO4 ). Th e two electrons, carrying a negative charge, are released into the lead anode. Th is is the st1 half reaction of the redox couple and can be described with the following equation:

2- – Pb (s) + SO4 (aq) → PbSO4 (s) + 2e (in conductor)

FIGURE 13

-2 -2 Sulfuric acid electrolyte O Lead- Sulfuric acid electrolyte O Lead- dioxide dioxide Pb+4 electrode Pb+4 electrode H+ + O-2 O-2 H H O -2 -2 2 SO -2 SO 4 O 4 - SO -2 Pb+4 SO -2 Pb+4 4 - 4 H+ O-2

-2 H O -2 H+ O 2 O H2O H2O Pb+4 Pb+4

O-2 O-2

Image source: GIZ/S4GJ + 2- Th e aqueous cations (H , hydrogen protons) and anions (SO4 , sulphate anions) also react with the 4+ cathode material (PbO2). As a result, the lead cation (Pb = oxidising agent) gains two electrons and is 2+ 2- reduced to Pb . Th is cation forms an ionic bond with the sulphate anion (SO4 ) similar to the process at the anode. Th e positively charged hydrogen ions (H+) combine with the oxide ions (O2−) at the cathode nd and form water molecules (H2O). Th is is the 2 half reaction of the redox couple and can be described with the following equation:

2- + – PbO2 (s) + SO4 (aq) + 4H (aq) + 2e (in conductor) → PbSO4 (s) + 2H2O (l)

158 FIGURE 14

Pb PbO2 O-2 H O -2 0 2 Pb SO4 Pb+4 + Pb0 H+ H -2 H+ H+ O Pb0 - -2 O-2 -2 SO4 0 -2 SO4 - Pb SO -2 +4 - 4 SO Pb H+ 4 - 0 Pb -2 H+ H+ O Pb0 H+ O-2 THEME 2.2.1 H2O Pb0 Pb+4

-2 H2O O

Image source: GIZ/S4GJ Both half reactions cause the electrodes to become coated with lead sulphate, a poor conductor, and at the same time reduce the concentration of the acid electrolyte.

FIGURE 15

+ + H Pb H PbO H+ 2 H+ -2 SO4 -2 SO4

H2O

PbSO4

V ca. 2.1V ca. 1.7V

ca. 0.4V

Image source: GIZ/S4GJ

In a commercial lead-acid battery one cell consists of multiple pairs of Pb and PbO2 plates. Th e potential diff erence per cell is usually around 2.1 V and thus adds up to around 12.6 V when connected in series with 6 cells (specifi c battery types may vary). Connection of an electrical load allows a charge to fl ow from the negative to the positive terminal. Th is reduces the potential diff erence at the terminals. Th e chemical reactions however proceed and generate a continuous charge fl ow until the cell is completely discharged, i.e. lead sulphate (PbSO4) buildup at the terminals and electrolyte dilution. 159 FIGURE 16

H+ Pb PbO2 H+

-2 SO4

H2O

PbSO4 THEME 2.2.1

V ca. 1.9V ca. 1.6V

ca. 0.3V

Image source: GIZ/S4GJ Conclusion discharging: Chemical energy is converted into electrical energy through the reaction of

electrodes with an electrolyte. Diff erent electrode materials (Pb and PbO2) cause a redox potential and subsequently an electric current. Sulphuric acid is decomposed by the fl ow of charge and active material

(Pb and PbO2) is transformed to lead sulphate (PbSO4). As the cell is discharged, the terminals become coated with lead sulphate and reduce the concentration of the acid electrolyte. Th e state of charge can be estimated by measuring the density of the electrolyte. As sulfuric acid is about twice as dense as water, as the cell is discharged, the density of the electrolyte decreases.

F I G U R E 17: LEAD-ACID BATTERY CHARGING BY REVERSING THE ELECTROCHEMICAL PROCESS

+ + H Pb H PbO H+ 2 H+ -2 SO4 -2 SO4

H2O

PbSO4

V ca. 2.1V ca. 1.7V

ca. 0.4V

Image source: GIZ/S4GJ Connection of an electric power source forces charge fl ow from the positive to the negative terminal. Th e chemical reactions are driven into reverse direction, i.e. electrical energy is converted into chemical (stored) energy.

160 FIGU RE 18: LEAD-ACID BATTERY CHARGING BY REVERSING THE ELECTROCHEMICAL PROCESS

+ + H Pb H PbO H+ 2 H+ -2 SO4 -2 SO4

H O 2 THEME 2.2.1

Image source: GIZ/S4GJ Conclusion charging: Th e lead sulphate at the terminals is transferred into active electrode materials (Pb

and PbO2), i.e. the electrodes are reactivated and the concentration of the acid electrolyte becomes stronger. A secondary battery cell is thus capable of being recharged as its electrode reactions can proceed in either direction. During charging, electrical work is done on the cell to provide the energy needed to force the reaction in the non-spontaneous direction.

Please note: Th e technology of lead-acid storage batteries has undergone remarkably little change since the late 19th century. Th eir main drawback as power sources for electric vehicles is the weight of the lead. ! Th e maximum energy density is about 35 Ah/kg lead and actual values may be only half as much. Th ere are also a few other problems: (i) Th e sulphuric acid electrolyte becomes quite viscous when ambient temperature is low, thus inhibiting the fl ow of ions between the plates and reducing the current that can be delivered. Th is eff ect is well-known to anyone who has had diﬃ culty starting a car in cold weather. (ii) Lead-acid batteries tend to slowly self-discharge. A car left idle for several weeks might be unable to start if the battery is not brand new.

(iii) Over time, lead sulphate (PbSO4) cannot be converted to lead dioxide (PbO2) at the cathode. Th is is usually due to lack of complete discharge which gradually changes PbSO4 into an inert form, subsequently limiting battery capacity. Also, ‘fast’ charging can cause rapid hydrogen gas

(H2) in the electrolyte and along the lead surfaces, tearing PbO2 off the positive plate. Eventually, enough solid material accumulates at the bottom of the electrolyte to short-circuit the battery, leading to its permanent demise.

Other Lead-Acid Battery Types Th ere are many more types of primary cells available which use diff erent components as reducing agents at the anode and as the oxidising agents at the cathode. Examples include: (i) Car batteries (SLI – starter, lighting and ignition): Designed to provide a short burst of high current to crank the engine. Th is type of battery cannot handle deep discharge applications and the typical lifetime is around 1000 cycles at 20% of discharge. (ii) Deep discharge batteries: Th ese types are usually sealed and valve regulated. Th ey have thicker electrodes, usually a calcium alloy that maintains a low leakage current and more space below the electrodes for accumulation of debris preventing plates from easily shorting. (iii) Golf cart or forklift batteries: Th ese are similar to type 2 batteries but bigger and very rugged. Th ey use antimony alloy for their large electrodes and can last many years (> 10).

161 Batteries: General Principle of Operation Th e chemical reactions which take place in batteries are called redox reactions, i.e. oxidations and reductions. When both battery electrodes are connected to form a circuit, a reaction takes place between the negative terminal (anode) and the electrolyte. As a result, this reaction causes an electric current (electrons) to run through the circuit and back into the cathode where another reaction takes place. Both chemical reactions, i.e. at the cathode and anode, consume or chemically change the material of both terminals. When the material in the cathode or anode is fully consumed or changed by the reaction, the battery is no longer able to produce an electric current. At that point, your battery is ‘dead’.

Battery vs Fuel Cell Batteries and fuel cells are based on fairly similar electrochemical processes but there are some diff erences. In ordinary batteries (storage cells), the chemical components, i.e. electrodes and electrolytes, are

THEME 2.2.1 contained within the battery itself (self-contained). Th ey react and convert chemical energy into electrical energy. During this process electrodes and electrolytes are consumed. An example is the simplifi ed lead-acid battery reaction:

Pb + PbO2 + H2SO4  2PbSO4 + 2H2O

Pb (porous lead) and PbO2 (lead dioxide) are the electrodes and H2SO4 (sulfuric acid) is the electrolyte. As the battery is discharged the electrodes ‘disintegrate’ and become coated with lead sulphate (PbSO4) and the acid electrolyte (H2SO4) becomes weaker and weaker. In a fuel cell, fuel and oxidant, e.g. H2 and air, need to be supplied from an external source. Th e electrochemical energy conversion, i.e. chemical energy into electrical energy appears without consumption of its electrodes or electrolytes (see Th eme 2.2.3 for more detailed information).

162 Exercises Investigate electrochemical processes of galvanic cells Experiment 1 (i) Clarify the purpose of the experiment and its expected outcomes. Th e purpose of the experiment is to investigate electrochemical processes of voltaic cells. As a fi rst step in understanding the operation of galvanic cells, redox (oxidation-reduction) reactions need to be considered. A classic example is provided by the resulting chemical reaction when a

strip of zinc metal is placed into an aqueous solution of cupric sulphate, CuSO4. Th e expected observation is that some changes on the zinc and the cupric solution can be observed!

(ii) Ask a question, formulate an assumption or construct a hypothesis (If ... then ...).

What kind of electrochemical processes might happen when a strip of zinc metal is placed into THEME 2.2.1 a cupric sulphate solution? Th e hypothesis is: If a redox reaction takes place, then electrons are being transferred from the zinc to the cupric ion and the system behaves like a shorted battery according to the following chemical equation:

Zn (s) + CuSO4 (aq) → Cu (s) + ZnSO4 (aq) (iii) Decide what kind of material is needed to set up the experiment. Material list: 1. Zink metal strips 2. 10 grams (one tablespoon) of dry cupric sulphate (blueish colour) for the aqueous solution 3. 75 ml of distilled water 4. 100 ml glass beaker 5. One plastic table spoon

(iv) Following safety instructions: 1. Wear your PPE, particularly safety glasses, overall or coat and nitrile/latex gloves at all times while doing experiments with chemical substances. 2. Make sure to wash your hands aft er completing the experiments. 3. Waste disposal and clean-up: all solutions should be poured into a waste collection container provided by the lecturer. Do not put any solid metal in the trash. A collection container for the metal strips will provided by the lecturer.

(v) Develop an activity worksheet indicating the following: 1. Name(s) and Surname 2. Date and Time 3. Activity Title: Experiment 1 – Electrochemical Cells 4. Procedure (modus operandi) a. Prepare an aqueous solution of copper sulphate with 75 ml of distilled water and

one tablespoon (about 10 grams) of the dry chemical (CuSO4). Use the beaker and the plastic spoon! b. Put a piece of zinc metal in the cupric sulphate solution of the beaker. c. Store your setup in a safe place and try to observe what happens to the zink strip and the colour of the aqueous solution of cupric sulphate aft er around 3 hours and aft er around 24 hours (next day). Record you observations in the activity worksheet.

(vi) Analyse your results and draw a conclusion related to your hypothesis (see ii). Th e results confi rm the hypothesis. Over time, one can observe the disappearance of the blueish colour of the cupric solution, i.e. the Cu2+ ion and note further the appearance of a dark coppery plating on the zinc metal. Th e zinc metal also appears to be dissolving. Here one can observe that zinc is being oxidised while the cupric ion is being reduced. Th us, electrons are being transferred from the zinc metal to the cupric ion and the system behaves like a shorted battery. Th is is described by the following chemical equations: Oxidation: Zn → Zn2+ + 2e– Reduction: Cu2+ + 2e– → Cu

2+ 2+ Overall reaction: Zn + Cu → Cu + Zn or Zn (s) + CuSO4 (aq) → Cu (s) + ZnSO4 (aq) 163 Experiment 2 (i) Clarify the purpose of the experiment and its expected outcomes. Th e purpose of the experiment is to further investigate electrochemical processes of galvanic cells. Following up on the chemical reaction in Experiment 1, the results can be used to construct a so-called Daniell cell by separating the redox reaction observed in Exper- iment 1 into two half-reactions, i.e. one half-reaction associated with oxidation and the other one with reduction.

Oxidation: Zn → Zn2+ + 2e– Reduction: Cu2+ + 2e– → Cu

We must thus arrange the two half-reactions in such a way that they occur in separate

THEME 2.2.1 compartments of the cell. Th is must be done in a way so that the charge is forced to travel through an external device in order for the cell reaction to progress forward.

(ii) Ask a question, formulate an assumption or construct a hypothesis (If ... then ...). Is it possible to physically separate the redox-reaction of Experiment 1 into two half- reactions? Th e hypothesis is: It is possible to arrange the two half-reactions in a way that they occur in separate compartments. In the present example, we can do this by using two diff erent beakers for each two half-reactions and by connecting the two compartments with an external device (salt bridge) so that the charge is forced to travel through the device.

FI G U R E 19: SCHEMATIC SETUP FOR EXPERIMENT 2

q q V

Salt bridge Copper + 2- Zinc 2 Na SO4 (cathode) (anode)

2 e- 2 e-

2+ 2+ 2- Zn Cu SO4 Cu 2- Zn SO4

Image source: GIZ/S4GJ

164 (iii) Decide what kind of material is needed to set up the experiment. Material list: 1. Zink metal strips functioning as an anode 2. Copper metal strips functioning as a cathode

3. 10 grams (one tablespoon) of dry copper sulphate (CuSO4 , blueish colour) for the aqueous solution in beaker A

4. 10 grams (one tablespoon) of dry zinc sulphate (ZnSO4 , white colour) for the aqueous solution in beaker B

5. 10 grams (one tablespoon) of sodium sulphate, also known as sulphate of soda (Na2SO4 , white colour) for the aqueous solution in beaker C 6. 225 ml of distilled water 7. Th ree 100ml glass beakers

8. Th ree plastic tablespoons, one for the copper sulphate, one for the zinc sulphate and one for THEME 2.2.1 the sodium sulphate 9. One plastic or glass U-tube 10. One plastic syringe (60 ml) 11. Cotton wool 12. Two cables (red and black) with crocodile clamps 13. One multimeter

(iv) Develop an activity worksheet indicating the following: 1. Name(s) and Surname 2. Date and Time 3. Activity Title: Experiment 2 – Electrochemical Cells 4. Procedure (modus operandi) a. Use a white board marker and mark one beaker with a large A and the other beakers with a large B and a large C. b. Prepare solution A: an aqueous solution of copper sulphate with 75 ml of distilled water

and one tablespoon (about 10 grams) of the dry chemical (CuSO4). Use beaker A! c. Prepare solution B: an aqueous solution of zinc sulphate with 75 ml of distilled water

and one tablespoon (about 10 grams) of the dry chemical (ZnSO4). Use beaker B! d. We will use beaker A and beaker B as the two half cells. e. Prepare solution C: an aqueous solution of sodium sulphate with 75 ml of distilled water

and one tablespoon (about 10 grams) of the dry chemical (Na2SO4). Use beaker C! f. Prepare the salt bridge: We will use a U-tube as a salt-bridge to link beaker A and B. Use

solution C (Na2SO4) to fi ll the U-tube and create a salt bridge. Th e syringe is useful for fi lling the tube. Th e cotton balls are needed to plug each end of the salt bridge. 1. Insert one cotton plug into one end of the U-tube. 2. Fill the syringe with solution C and use the syringe to fi ll the U-tube. 3. Make sure that no gaps or big bubbles appear in the tube, as this would seriously impede current fl ow. 4. Close the other end of the U-tube with a cotton plug, leaving some cotton protruding from each end of the tube. g. Place the salt bridge in such a way that it connects beaker A with beaker B. h. Make sure that both ends of the U-tube are immersed in solution A and solution B (see Figure 19). i. Insert a copper strip into beaker A and a zinc strip into beaker B. j. Set the multimeter to a low DC setting (< 1 V). k. Connect the two cables to the multimeter and the two metal strips (see Figure 19). l. Record your observation/measurement in the activity worksheet. Record any changes in the voltmeter reading. Note the maximum reading. Note any changes at the copper and the zinc electrode.

165 (iv) Analyse your results and draw a conclusion related to your hypothesis (see ii). Th e results confi rm the hypothesis. Th e setup is an example of an electrochemical cell and produces a current which can be measured in volt (usually between 0.7 and 1.1 V). Each beaker acts as a half-cell and the salt bridge serves as a barrier between the two diff erent electrolytes while allowing the fl ow of charges. When the cell is set up, electrons fl ow from the zinc electrode through the wire/cable to the copper cathode. As a result, zinc dissolves in the anode solution to form Zn2+ ions. Th e Cu2+ ions in the cathode half-cell pick these electrons up and convert the cupric ion to pure Cu atoms on the cathode. Like any battery, the Daniell cell does not last forever – it only lasts as long as there are Cu2+ ions available and the zinc electrode is not consumed. In reality, the production of current diminishes as the concentration of the electrolyte at the zinc electrode increases, while the electrolyte at the copper electrode decreases. In fact, the positive ions produced by the zinc 2-

THEME 2.2.1 electrode need SO4 ions to balance the charges. Th e exact opposite occurs in the copper solution, which becomes depleted of positive ions. In other words, charge transfer from the zinc electrode to the copper ions takes place along a circuit. Th e potential diff erence refl ects the greater electrochemical activity of zinc over copper. Th e current fl ow depends on the size and rate of the reaction:

Zn (s) + CuSO4 (aq) → Cu (s) + ZnSO4 (aq)

TA BLE 1: STANDARD ELECTRODE REDUCTION POTENTIALS (E° V) OF SELECTED METALS

Half-reaction Li+ + e–  Li Mn2+ + 2e–  Mn Zn2+ + 2e–  Zn (E° V) −3,04 −1,18 −0,76 Half-reaction Pb2+ + e–  Pb Cu2+ + 2e–  Cu Ag+ + e–  Ag (E° V) −0,13 +0,34 +0,8

It is important to remember that these are not absolute values, but potentials that have been measured relative to the potential of hydrogen if the standard hydrogen electrode is taken to be zero. In the examples we used earlier, the zinc’s electrode reduction potential is −0,76 and copper’s is +0,34. So, if an element or compound has a negative standard electrode reduction potential, it means it forms ions easily. Th e more negative the value, the easier it is for that element to form ions, i.e. to be oxidised and be a reducing agent. If an element or compound has a positive standard electrode potential, it means it does not form ions as easily.

Please note: To increase the potential diff erence you may want to consider setting up a battery of ! galvanic cells as indicated in Figure 20.

166 FIGURE 20: SCHEMATIC SETUP OF DANIELL CELLS IN SERIES CREATING A BATTERY

V THEME 2.2.1

Image source: GIZ/S4GJ

Further Information on the Resource CD

(i) Th e Chemical Process Inside A Bosch Battery. Video by Bosch. (ii) Electrochemistry, Chemical reactions at an electrode, galvanic and electrolytic cells A Chem1 Reference Text, Stephen K. Lower @ Simon Fraser University, PDF.

Your own notes

167 Your own notes NOTES

168 THEME 2.2.2 ELECTROCHEMICAL PROCESSES IN FUEL CELLS

Introduction

is theme will brie y introduce you to the basic electrochemical reactions relevant to fuel cells and explain their basic principles of operation.

Keywords THEME 2.2.2

Fuel cell vs battery Redox reaction Proton exchange membrane fuel cell (PEMFC) PEFC components Electrodes Anode Cathode Electrolyte Catalyst PEMFC components and operation Electrolysis of water for hydrogen generation Electrolysis: a redox reaction Training kit components Regression line

Theme Outcomes

At the end of this theme you should be able to: (i) Describe the electrochemical process where hydrogen and oxygen interact within a fuel cell to generate electricity. (ii) Explain the two electrochemical reactions occurring at the anode and cathode of a fuel cell. (iii) Explain why fuel cells are also referred to as electrochemical energy converters. (iv) Sketch and explain a proton exchange membrane (PEM) fuel cell. (v) Discuss the principles of water electrolysis for hydrogen generation and why the association with renewable energy systems is advantageous. (vi) Explain why energy generation through fuel cells can be regarded as a climate-friendly technology. (vii) Identify the training kit components for hydrogen and fuel cell experiments. (viii) Measure the volume ratio of the gases produced. (ix) Measure the quantities of gas produced per unit time depending on current.

Deﬁ nition of Terms Fuel Cell vs Battery e processes by which fuel cells provide an electric current di er slightly from battery processes, as explained in eme 2.2.1. Fuel cells need to be supplied with fuel and oxidants from an external source. Batteries on the other hand contain their chemical components, i.e. electrodes and electrolytes. Fuel-cell operation is based on reversing electrolysis, generating an electrical current as long as external fuel, such as hydrogen, methanol etc. and oxidants such as air, are available. Various types of fuel cells exist, including proton exchange membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), alkaline fuel cells (AFCs), molten-carbonate fuel cells (MCFCs) and solid-oxide fuel cells (SOFCs). Among the di erent types of fuel cells, polymer electrolyte fuel cells (PEFCs), which include PEMFC, receive the

169 most attention because of their higher electrical e ciency, power density and durability. Similar to batteries, fuel cell technologies involve an extensive vocabulary and a signi cant amount of jargon. Some basic technical terms concerned with composition, structure and properties of fuel cells (focussing on PEMFC), are provided below. Redox Reaction A fuel cell is a device that converts the chemical energy from a fuel and oxidants, e.g. hydrogen and oxygen, into electrical energy through a redox reaction. is process involves two half-reactions which are catalysed at separate electrodes (see Table 1).

TA BLE 1: STANDARD ELECTRODE REDUCTION POTENTIALS (E° V) OF HYDROGEN AND OXYGEN THEME 2.2.2

Anode Cathode

+ – + – Half-reaction 2H + 2e  H2 (g) O2 (g) + 4H + 4e  2H2O

(E° V) +/- 0 +1,23

FIGURE 1: TWO HALF-REACTIONS OCCUR AT THE ANODE AND CATHODE ASSEMBLY OF A FUEL CELL

V 4e- Electrical energy

O2 4H+ Atmospheric oxygen 2- - + 2O 2H2 Hydrogen - +

2H2O Water - +

Anode Cathode Membrane

+ - + - 2H2 4H + 4e O2+ 4H + 4e 2H2O

Image source: GIZ/S4GJ

PEFC Components Similar to batteries, PEM fuel cells are made up of two electrodes, i.e. the anode and the cathode, and an electrolyte. In addition, each fuel cell has sealings and ow plates (see Figure 1) through which the fuel is passed to reach the electrodes. is arrangement of two electrodes separated by an electrolyte is the basic setup required for a fuel cell to conduct an electrical current through a circuit. In a PEFC, anode, electrolyte (membrane) and cathode are put together in a sandwich structure. To achieve higher output voltages and higher power, single cells are o en combined into a large fuel cell stack.

170 FIG U RE 2: THE BASIC COMPONENTS OF A POLYMER ELECTROLYTE FUEL CELL (PEFC SCHEMATIC VIEW)

Anode Cathode H2 O2 - + THEME 2.2.2

Flow plate Sealing Electrode Electrode Sealing Flow plate Electrolyte

Image source: GIZ/S4GJ

Electrode In fuel cells two types of electrode terminals can be di erentiated: a negative terminal (anode) and a positive terminal (cathode). Both are usually made of porous carbon containing platinum (Pt) or platinum alloy as a catalyst.

Anode e anode, the negative terminal, is also called the fuel electrode due to the fact that fuel, for example hydrogen, is supplied here. e half-reaction occurring at the anode (see redox reaction) requires a catalyst.

Cathode e chemical reaction occurring at the cathode uses the electrons, the hydrogen ions and the oxygen to form water. is half-reaction also requires a catalyst.

Electrolyte In a PEFC, the electrolyte is a polymer membrane (see polymer membrane). is membrane is capable of transporting electrically charged particles, i.e. conducting hydrogen ions from the anode to the cathode. e electrolyte also inhibits the ow of electrons between the anode and cathode.

Catalyst A catalyst is a substance that participates in a chemical reaction without being consumed or changed. Catalysts modify and increase the rate of the chemical reaction. In other words, catalysts lower the activation energy required for a reaction without altering the reaction equilibrium. In a fuel cell, catalysts such as platinum (Pt) or platinum alloy are used in the electrodes to lower the activation energy required for the redox reaction (see Figure 3).

171 FI G U R E 3: CATALYST REACTION SITES (Pt) AT POROUS CARBON ELECTRODES

Pt reaction sites V H O Hydrogen Oxygen 2 O H2 2 O2 H+ H+ 10nm

THEME 2.2.2 Water Carbon

H2O Pt reaction sites Anode Electrolyte Cathode at the cathode

Image source: GIZ/S4GJ

In this schematic drawing the H2 and O2 fuel pathways are shown on the right-hand side of the illustration. e le -hand side shows the reaction side of the catalytic oxygen reduction, and subsequent forming of water molecules on the surface of platinum (Pt) sites in more detail. ese catalytic sites are located as multi-layered Pt membranes on the porous carbon electrode structures. us, at the cathode the catalyst lowers the activation energy required for the redox reaction which causes electrons, hydrogen ions and oxygen to react and to produce water. At the anode the catalyst lowers the activation energy required for the redox reaction, which causes decomposition of hydrogen into protons and electrons.

Polymer membrane Polymer membranes separate the two electrodes of a fuel cell, thus acting as the electrolyte by allowing passage of ions between the electrodes while inhibiting electron conduction. Na on membranes for example are synthetic polymers used in PEMFCs, permitting hydrogen ion transport while preventing electron conduction. Such membranes are very thin, only a few micrometres. e cation exchange membrane is positioned between a backing lm and a coversheet (see Figure 4).

FIGURE 4: A PROTON EXCHANGE MEMBRANE (PEM)

Backing film

Membrane

Coversheet

Image source: GIZ/S4GJ

172 Proton Exchange Membrane Fuel Cell (PEMFC) Components PEMFCs are a type of proton exchange fuel cells that take their name from the special polymer membrane used as the electrolyte. Typical cell components include the ion exchange membrane, an electrically conductive porous backing layer, an electro-catalyst at the interface between the backing layer and the membrane, and ow plates that deliver the fuel and oxidant to the reactive sites via ow channels. e most common material for this membrane is Na on, a per uorinated sulphonic acid polymer. e membrane is compressed between the two porous carbon electrodes coated with a minimum amount of platinum catalyst. Platinum is essential for the reaction to take place, due to the low operating temperature of this type of fuel cell. e assembly of the membrane and the electrodes is called membrane electrode assembly (Figure 5). A PEMFC stack is composed of a series of single cells separated by bipolar plates with integrated gas ow channels (Figure 6).

Proton Exchange Membrane Fuel Cell (PEMFC) Operation THEME 2.2.2 e fuel gas (usually hydrogen) and the oxidant (air or pure oxygen) are supplied to the membrane electrode assembly (MEA). Here fuel and oxidant pass through a series of plates, which di use them in the most uniform way to the two membrane sides. A PEMFC transforms the chemical energy liberated during the electrochemical reaction of hydrogen and oxygen into electrical and thermal energy. e exothermic redox reaction is shown in Figure 5.

A stream of hydrogen is delivered to the anode side of the MEA. At the anode side it is catalytically split into protons and electrons, conducting the oxidation reaction. ese protons permeate through the polymer electrolyte membrane to the cathode side. e electrons travel along an external load circuit to the cathode side of the MEA, thus creating the current output of the FC. In the meantime, a ow of oxygen is delivered to the cathode side of the MEA. ere, oxygen molecules are reduced and, subsequently, react with the protons permeating through the membrane to form water molecules and also liberating heat.

FI G U R E 5: COMPONENTS AND OPERATION OF A PEMFC (SCHEMATIC)

V Hydrogen e - e - e - e - e - Oxygen e -

e - H + --- e H + O 2H O 2 H + - O - 2 H +

+ - - 2- 2H2 4H +4e O2+4e 2O

H2O Heat

Anode/ Gas diffusion Membrane Gas diffusion Cathode/ Flowplate layer layer Flowplate with catalyst with catalyst

Image source: GIZ/S4GJ

173 FIGURE 6: A PEMFC STACK COMPOSED OF A SERIES OF SINGLE CELLS SEPARATED BY BIPOLAR PLATES

Bipolar-plate with flow field

Membrane

Gas diffusion layer with catalyst THEME 2.2.2

End plate

Image source: GIZ/S4GJ

Your own notes

174 Electrolysis of Water for Hydrogen Generation Compared to most other hydrogen production processes (see eme 1.2.1), electrolysis o ers a more sustainable hydrogen production pathway. One advantage of electrolysis is that it is capable of producing high purity hydrogen (>99.999%). However, re nery costs for electrolysis are huge, mainly due to the high amount of electric power needed to produce pure hydrogen. Nonetheless, if the required power is supplied via renewable technologies (see experiments further on: Operation of the electrolyser with PV cells and wind turbine as a hybrid system), negative environmental impact costs, compared to fossil fuel combustion, could drastically be reduced (see also eme 1.2.1: Hydrogen as an energy vector). Electrolysers are electrochemical devices which work like a fuel cell in reverse and can split water into its constituent molecules, hydrogen (H2) and oxygen (O2), by passing an electric current through water (Figure 7). THEME 2.2.2 F I G U R E 7: ELECTROLYSIS: AN ELECTRIC CURRENT SPLITS WATER TO PRODUCE HYDROGEN AND OXYGEN

e- - +

H2 O2

H O e-

e- H+ OH-

H2O

Image source: GIZ/S4GJ

175 Electrolysis: A Redox Reaction In pure water, a reduction reaction takes place at the cathode. Electrons combine with hydrogen cations to form hydrogen gas.

+ − Reduction at cathode: 4H (aq) + 4e → 2H2 (g)

Oxidation occurs at the anode, generating oxygen gas and releasing electrons to the anode to complete the circuit.

+ − Oxidation at anode: 2H2O (l) → O2 (g) + 4H (aq) + 4e

Combining either half reaction pair yields the following overall decomposition of water into oxygen and hydrogen: THEME 2.2.2 Overall reaction: 2H2O (l) → 2H2 (g) + O2 (g)

e number of hydrogen molecules produced is thus twice the number of oxygen molecules produced. Assuming ideal e ciency, the produced hydrogen gas therefore has twice the volume of the produced oxygen gas (Figure 8). e number of electrons pushed through the water is twice the number of generated hydrogen molecules and four times the number of generated oxygen molecules.

FIGU RE 8: ELECTROLYSIS: GAS QUANTITY RATIOS AND REDOX REACTION

Hydrogen gas H Oxygen gas O2( g) 2 (g) 1 volume of gas 2 volumes of gas

ElectrolyteAnode (graphite)(water)

Anode Cathode (graphite) (graphite)

+ -

- + At the cathode: 4e + 4H (aq) 2H2(g) 2- - At the anode: 2O (aq) - 4e O2(aq)

Overall: 2- + 2O (aq) + 4H (aq) 2H2 (g) + O2 (g)

Image source: GIZ/S4GJ When a DC voltage is applied, water molecules at the anode are oxidised to oxygen. At the cathode, protons (H+ ions) are reduced to hydrogen gas by incorporating the electrons released from the oxygen at the anode.

176 Experiments For training to be truly e ective, it is necessary to practically apply your knowledge in hands-on experiments and real-world installations. Given that these are o en di cult to execute in most TVET colleges, we can o er you some resources and equipment for practical work. Components required for practical activities include fuel cell training kits to simulate real fuel cell operations. We will introduce you to all of the above in Topic 4 in more detail, but we suggest that you already start with some practical activities

which are based on the IKS H2 Trainer Junior Set available at your college for RET Level 4. is training set includes modular experiments designed to demonstrate, albeit on a miniature scale, important aspects of fuel cell operation covered in this textbook.

Training Kit Components Before you start with the rst practical activities, we recommend that you familiarise yourself with the

training kit and identify all of its components. Please also consult the student manual in the training set THEME 2.2.2 for more information and descriptions of the components, as well as the operating instructions. We will brie y describe the components and show you some images illustrating them. Please note that all compo- ! nents, particularly the fuel cell and the electrolyser, need to be handled with care!

FIGURE 9: IKS H 2 TRAINER JUNIOR SET

Image source: Doerthe Boxberg

177 FIGURE 10: SETUP FOR EXPERIMENT 1 THEME 2.2.2

Image source: Doerthe Boxberg

e fuel cell training set comes in a red suitcase with a shaped foam inlet for all components except for the base board, which you will nd in the lid together with the instruction manual and the CD. e base board houses the electrolyser, gas storage and fuel cell, experimentation modules and multimeters. e power supply and other accessories come separately. Table 2 lists the components supplied and its symbols used in the experiment descriptions.

Safety and Commissioning Read the notes on safety before starting with the experiments. Prepare the individual devices for the experiments, particularly the electrolyser, the fuel cell and the gas storage set. Use only distilled water for operation. Ensure that all connections have the correct polarity. Remove all tting caps from the sleeves and store them in the correct baseplate compartment. Be careful with the Plexiglas housing of each de- ! vice as they are sensitive to impact stress.

Your own notes

178 TA BL E 2: SYMBOLS USED FOR DEVICES IN THE EXPERIMENTAL SETUPS

V A

Timer V A

V A O2 H2

O2 H2 O2 H2 V A V A Electrolyser

O H + - 2 2 + -

O2 H2 THEME 2.2.2 + - + - Power supply / Power regulator

+ -

H2 O2

Gas storage H2 O2 O2 H2 O H V A 2 2 + - V A + - H O H2 2 O2 2 O2 H2 O2 H2

+ - O2 H2 O H Fuel cell 2 2 O2 H2 + + - - + - + -

2 multimeters with 2 mm connectors V A

H2 O2

O2 H2

Measuring box with variable resistor O2 H2

+ - H2 O2

+ -

PV modules and light source V A O2 H2

+ - O2 H2

Wind machine (12V) and HAWT

H2 +O2 -

179 O2 H2

H2 O2 + -

O2 H2

+ - In this theme we will start with the rst two experiments only and will continue with the other experiments in eme 4. However, with the set of equipment supplied, the following experiments are possible: (i) Measurement of the volume ratio of the generated gases (ii) Measurement of the generated volumes of the gases per unit of time depending on the current (iii) Determination of the power e ciency and the Faraday e ciency of the electrolyser (iv) Determination of the U/I-characteristic of the electrolyser (v) Determination of the power e ciency and the Faraday e ciency of the fuel cell (vi) Determination of the U/I-characteristic of the fuel cell

Experiments in combination with the Solartrainer Junior: (i) Operation of the electrolyser with PV cells

Experiments in combination with the Windtrainer Junior:

THEME 2.2.2 (i) Operation of the electrolyser with a wind turbine

Experiments in combination with the Solartrainer Junior and the Windtrainer Junior: (i) Operation of the electrolyser with PV cells and wind turbine as a hybrid system (ii) Building up of a stand-alone operation net

Your own notes

180 Exercises

Experiment 1: Measure the volume ratio of the gases produced

is experiment is designed to generate a rst idea about electrolysis and hydrogen production by using an electrolyser. Electrolysis of water is a redox reaction yielding the following overall decomposition of water into oxygen and hydrogen:

Overall reaction: 2H2O (l) → 2H2 (g) + O2 (g)

As you can see in the above equation, the number of hydrogen molecules produced is twice the number of oxygen molecules. Assuming ideal e ciency, we can expect that the produced hydrogen

gas has twice the volume of the produced oxygen gas (Figure 8). In this experiment, we attempt to THEME 2.2.2 examine the ratio of the produced gases and attempt to verify the above-mentioned equation as a scienti c statement. If required, please consult the student manual of your training set for more information, e.g. description of the devices and their operating instructions.

FIGU RE 11: SETUP OF EXPERIMENT 1 (SCHEMATIC)

O2 H2 H2 O2

+ -

Image source: GIZ/S4GJ

Assignment:

For this experiment you need the power supply / power regulator, the electrolyser and the gas storage units. Further, you will need two cables and two of the transparent silicon tubes. Set the experiment up as indicated in Figure 11. Ensure that all connections have the correct polarity. Use distilled water and the syringe to ll the gas storage unit up to the 0 ml mark. Ensure that the correct sleeves of gas storage unit are closed with the red tting caps (see Figure 10). is prevents the gases from steaming out of the storage unit. Set the power regulator to maximum and wait until 20 ml of hydrogen gas has been produced. Determine the gas volume of oxygen. Document your measurements in Table 3.

181 TA B L E 3: GAS VOLUMES

Gas volumes in ml

Hydrogen

Oxygen

THEME 2.2.2 Determine the volume of gases produced:

Volume H2 : Volume O2 = ………… : …………

Explain your ndings, making reference to the redox reaction:

…………………………………………………………………………………………………………..………

182 Experiment 2: Measure the quantities of gas produced per unit time depending on current

is experiment is designed to generate further ideas about electrolysis and hydrogen production by using an electrolyser. As we have seen from the theory and in Experiment 1, electrolysis of water results in quantitative relationships of gas volumes. e ratio of produced volumes of H2 and O2 are approximately 2 : 1, and correspond with the equation of the redox reaction.

FIG U RE 12: SETUP FOR EXPERIMENT 2 THEME 2.2.2

Image source: Doerthe Boxberg

We could observe further relationships between other factors if we consider, for example, the quantity of electrical charge that passes through the electrolyte per unit time. is relationship is described by Faraday’s rst law of electrolysis. It states, that the gas volumes produced due to ow of charge through water are directly proportional to the quantity of the electrical current passed through it.

is can be expressed as m ∝ Q, whereas m = mass (or volume) of gases produced and Q = charge (quantity of current).

In this experiment we thus attempt to examine this relationship between quantity of charge and gas volumes, aiming to verify Faraday’s rst law.

If required, please consult the student manual of your training set for more information, e.g. description of the devices and their operating instructions.

183 FI G U R E 13: SETUP OF EXPERIMENT 2 (SCHEMATIC)

O2 H2 H2 O2 THEME 2.2.2 A + -

Image source: GIZ/S4GJ

Assignment:

For this experiment you will need the power supply / power regulator, the timer, one multimeter, the electrolyser and the gas storage units. Furthermore, you need three cables and two of the transparent silicon tubes. Set the experiment up as indicated in Figure 12 and 13. Ensure that all connections have the correct polarity. Use distilled water and the syringe to ll the gas storage unit up to the 0 ml mark. Ensure that the correct sleeves of gas storage unit are closed with the red tting caps (see Figure 10). is prevents the gases from steaming out of the storage unit. Set the power regulator to 0 mA and the multimeter to 2000 mA. Consult Table 4, rst column, and conduct your measurements with the six di erent current settings. In other words, set the six current values in six 100 mA steps from 0 – 500 mA and document your volume measurements per advised time interval in Table 4 below.

Calculate the values for the volume di erences (ΔV in ml) and the volume di erences per time (ΔV in ml/min) for each type of gas.

184 TABLE 4: GAS VOLUMES

Hydrogen Oxygen

Current (I) Time (t) Volume H2 ∆V ∆V/t Volume O2 ∆V ∆V/t mA in min in ml in ml in ml/min in ml in ml in ml/min

Start End Start End

0 0 0 0 0 0 0 0 0 0

100 6 0 0

200 5 THEME 2.2.2

300 3

400 2

500 2

Register your calculations, i.e. volume di erences per time (ΔV in ml/min) against the six current values (0 – 500 mA) in Figure 15. Indicate the oxygen values as red dots and the hydrogen colours as blue dots in the diagram. Now nd the best- tting straight line through the points for each gas type (see Figure 14 as an example). ese two lines are so-called linear regression lines. Use red and blue for each line in Figure 15 and discuss your results. If almost all of your calculated values are on or very close to the respective regression line, one can assume that the proposed gas volumes are proportional to the current and Faraday’s rst law (m ∝ Q) is veri ed. If this is not the case, check your calculations again and/or repeat the experiment.

FIGURE 14: TWO TYPES OF GRAPHS ILLUSTRATING SIMPLE LINEAR REGRESSIONS

Graph A Graph B Dependent variable Dependent variable

Independent variable Independent variable

Image source: GIZ/S4GJ A simple linear regression uses one independent variable, and it describes the relationship between the independent variable and dependent variable as a straight line.

185 FI G U R E 15: REGRESSION LINES / GAS QUANTITIES VS CURRENT

5 Oxygen

Hydrogen

THEME 2.2.2 3

∆V in ml/min in ∆V

0 100 200 300 400 500 600

Current (mA)

…………………………………………………………………………………………………………..………

186 Further Information on the Resource CD

(i) Video: TOYOTA Fuel cell - How does it work (mp4). (ii) Video: How does a fuel cell work, Naked Science Scrapbook (mp4). (iii) Video: How It’s Made Hydrogen Fuel Cells (mp4). (iv) Video: Hydrogen Fuel Cells, Ballard explains PEM fuel cells (mp4). (v) Video: PEM Fuel Cell- How it works (mp4). (vi) Comparison of Fuel Cell Technologies, US department of energy, 2016 (pdf). THEME 2.2.2

Your own notes

187 188 Unit 2.3 Unit 2.3 covers the following two themes: two following covers the Unit 2.3 Themes in this Unit able you to: be should unit, end ofAt this the Unit Outcomes solutions. mobility alternative someof thebasic principles you to introduces unit This concepts. mobility new as hydrogen powertrains and to electro additive or petrol substitute fuel as biofuels from ranging developed, have approaches been of different avariety purpose For this impacts. transport unwanted and negative most to minimise and concepts, mobility sustainable test to develop and thus is aim the Globally, no sustainable. longer consideredas be can form current its in transportation and that mobility fact the have to led emissions nitrogen-oxide and diesel-particle including effects, mental environ- negative and other effect greenhouse anthropogenic energy-related the as Various such factors Introduction BA 2.3 UNIT (v) (vi) (iv) Theme 2.3.2 Essential E-Car Components and their Functions their Componentsand E-Car Essential 2.3.2 Theme Compared 2.3.1Eco-Car Types Theme (iii) (ii) (i) SIC PRINCIPLES OF E

and their functionality. their and Pr Ex Pr Co Li Ex st the various fuel options relevant for the automotive for sector. the relevant options fuel various the st ovide a detailed sketch of the powertrain of a typical e-car, including key components key including e-car, of atypical powertrain of the sketch adetailed ovide overview. market eco-car an ovide plain why fuel cells provide interesting opportunities for e-mobility concepts. for e-mobility opportunities interesting provide cells why fuel plain plain why alternative fuels are important for modern mobility concepts. mobility for modern important are fuels why alternative plain mpare different eco-car types. eco-car different mpare

- MOBILITY THEME 2.3.1 ECO-CAR TYPES COMPARED

Introduction

Climate action and the modernisation of the economy are two sides of the same coin. Subsequently, it is important to incentivise investments in innovations, as this could result in more sustainable mobility options and job-creating growth. However, our notion of mobility usually hinges on modernising individual and personalised automotive transport. Innovation however does not stop here: in the short- term more and more transport services will be shared and soon a growing number of them might even 2.3.1 THEME be automated. Driverless cars are also in the not too distant future. Th us, in this theme we will introduce you to the main types of alternative passenger cars, as well as other transport options.

Keywords

Sustainable mobility concepts Alternative fuel options Diff erent eco-car types Hybrid electric vehicles (HEVs) Plug-in hybrid electric vehicles (PHEVs) Battery electric vehicles (BEV) Fuel cell electric vehicles (FCEV) EV market overview Global markets EU markets Chinese markets Japanese markets US markets

Theme Outcomes

At the end of this theme you should be able to: (i) Explain why alternative fuels are important for modern mobility concepts. (ii) List the various fuel options relevant for the automotive sector. (iii) Explain why fuel cells provide interesting opportunities for e-mobility concepts. (iv) Compare diff erent eco-car types. (v) Provide an eco-car market overview. (vi) Provide a detailed sketch of the powertrain of a typical EV, including key components.

Defi nition of Terms Sustainable Mobility Concepts In recent years, the automotive sector in developed countries has gained renewed momentum with the growth in the demand for passenger cars, especially in emerging countries. Making conventional transport sustainable is however far from being achieved. Th e transport sector continues to be one of the largest emitters of CO2 (Figures 1 and 2) and a considerable source of air pollution, severely impacting on human health, especially in urban areas. Th is needs to be considered as a cost that burdens public spending, ranging from health- all the way to cleaning services. Overall, 13% of an average European household’s budget is spent on mobility, which is very ineffi cient. In the EU, a passenger car is parked on average 92% of the time and, when the car is used, fewer than two of its fi ve seats are occupied. Furthermore, even though a car sold in 2014 was 25% more effi cient in terms of CO2 emissions than one sold in 2000, growth in travelled distance and car ownership, due to a lack of 189 alternative solutions, and the increased average weight of vehicles, have excessively off set effi ciency gains. Finally, the 2015 car emission scandal in Germany and France (VW, Audi, Renault etc.) highlighted the

need to reduce carbon emissions and air pollutants altogether, since CO2 is only part of the problem.

FIGURE 1: GREENHOUSE GAS EMISSIONS OF DIFFERENT SECTORS IN THE EU

13 THEME 2.3.1 THEME 12

06 1997 2007 1990 1991 1992 1993 1994 1995 1996 1998 1999 2000 2001 2002 2003 2004 2005 2006 2008 2009 2010 2011 2012 2013 2014

Transport Energy Industries Residential and Commercial Agriculture Waste and Others Industry

Image source: S4GJ/GIZ (Data by EEA, GHG data viewer 2015) Greenhouse gas emissions of diff erent sectors in the EU (% change between 1990 and 2014)

190 FIG U RE 2: GREENHOUSE GAS EMISSIONS FROM TRANSPORT IN THE EU

Domestic aviation Other Railways Domestic navigation

International aviation 1 1 1 1 12% International navigation

12% THEME 2.3.1 THEME

72%

Road transportation

Image source: S4GJ/GIZ (Data by EEA, GHG data viewer 2015) Greenhouse gas emissions from transport in the EU (2014, in %)

Th e transport sector is therefore both a curse and a blessing for most economies and societies - on the one hand, transport and logistics provides its economic lifeblood, on the other hand it hampers the very economic gains it helps to increase by being less sustainable than desired. Renewable fuel options and modern mobility concepts are thus important for the transformation of transport and the low-carbon transition. A more competitive global mobility market is emerging, and new players, including China who is the new largest passenger e-car market (mainly BEV and PHEV light-duty types) in the world, are putting pressure on established car manufacturers in Europe and the US (Figure 3).

FI G U R E 3: GLOBAL MARKETS OF ELECTRIC VEHICLES (BEVS AND PHEVS)

China 645,708

Europe 637,552

United States 570,182

Japan 147,488

Norway 135,276

The Netherlands 113,636

France 108,065

United Kingdom 91,627

Germany 74,754

100,000 200,000 300,000 400,000 500,000 600,000

Image source: S4GJ/GIZ (Data by Argonne National Laboratory, and OECD/IEA, 2016) – Cumulative registrations as of December 2016 by country/region

191 Alternative Fuel Options Vehicles that operate primarily on fossil-based hydrocarbon fuels such as petrol or diesel historically dominated passenger car and truck sales. In the last two decades however, sales of cars that operate on alternative fuels like ethanol, natural gas and electric power have been growing. Millions of fl exible fuel vehicles, e.g. vehicles that can run on a mixture of about 85% ethanol and 15% petrol have been sold primarily in North and South America in the past decade. At the same time, a number of European and Japanese automobile manufacturers developed bi-fuel models that can run equally well on both autogas and petrol. Autogas is the common name for liquefi ed petroleum gas (LPG) when it is used as a fuel in internal combustion engines in vehicles as well as in stationary applications, such as generators. It is a mixture of propane and butane. Lastly, new models of electric vehicles (EV), including fuel cell electric vehicles (FCEV), battery electric vehicles (BEV) and plug-in hybrid electric vehicles types have also entered the market in increasing numbers. Relative to fossil-based hydrocarbon fuels, many of these fuels, depending on how they are produced,

THEME 2.3.1 THEME reduce overall emissions of CO2 into the atmosphere. In fact, operating a vehicle exclusively on electric power or hydrogen produces no harmful GHG emissions if these types of fuel are generated from renewable resources, including PV or wind turbine plants. Interest in hydrogen as an alternative fuel for transportation applications developed as a result of increasing social awareness of environmental degradation. Th e possibilities of reducing environmental challenges by selecting more environmentally-friendly energy systems, e.g. fuel cell systems, have a high potential for green energy conversion. Th e eﬃ ciency of applying hydrogen-powered fuel cell technologies, for example as in FCEVs (Figure 4), depends on the characteristics of the many production steps and chains involved, which include manufacturing, distribution and the conversion of the chemical energy of hydrogen into mechanical work in a vehicle (Figure 4). Adequate evaluation of environmental impact and energy consumption throughout the overall hydrogen production and utilisation life cycle, in comparison with that of mineral fuels, is critical for making proper strategic decisions about its competitiveness in the future. Investing in transitional technologies such as hybrid cars or fully electrical solutions, be it FCEVs or BEVs, is a feasible and available option. In addition, the transition towards a low-carbon mobility system requires a sizeable amount of private and public investment to improve access to alternative fuel infrastructure capacities.

FIGURE 4: FCEV OPERATING PRINCIPLE SIMPLIFIED (SCHEMATIC)

STEP 5 STEP 4 Motor is POWER supplied activated to motor H and vehicle Hydrogen refueling moves H2 Current

Fuel cell stack Battery Power Motor Current generation

High-pressure Air (Oxygen) O Oxygen Hydrgen 2 H2 hydrogen tank

H2O

STEP 2 STEP 6 Oxygen and STEP 3 Water STEP 1 hydrogen POWER and water emitted Air (oxygen) supplied to fuel generated through outside taken in cell stack chemical reaction vehicle

Image source: S4GJ/GIZ

192 Different Eco-Car Types Th e electrifi cation of vehicles is a not too distant reality and a critical juncture between modernisation and sustainability. E-cars however are diff erent in terms of engine components, range, energy eﬃ ciency and costs. One could, for example, diff erentiate between diff erent degrees of vehicle electrifi cation with diff erent impacts on CO2 emissions. Consequently there are indeed diff erent solutions available (Figure 5).

FI G U R E 5: DIFFERENT DEGREES OF VEHICLE ELECTRIFICATION

ICE THEME 2.3.1 THEME HEV

PHEV

FCEV

BEV

0 20 40 60 80 100

Image source: S4GJ/GIZ (Data by Industrial Innovation for Competitiveness, JRC) Estimate of percentage of electrifi cation for each category. ICE = Internal combustion engine, HEV = Hybrid electric vehicle, PHEV = Plug-in hybrid electric vehicle, FCEV = Fuel cell electric vehicle, and BEV = Battery electric vehicle

Hybrid Electric Vehicles (HEVs) Hybrid cars can either be partly fossil fuel (or biofuel) powered or partly electric or hydrogen-powered. Most combine an internal combustion engine with an electric engine, though other variations do exist. Th e internal combustion engine is oft en either a petrol or diesel engine.

FIGURE 6: SIMPLIFIED HEV DESIGN CONCEPT (FWD SCHEMATIC)

Electric motor Transmission High-voltage battery Combustion engine

Air conditioning compressor

Power electronics High-voltage lines

Image source: S4GJ/GIZ Th is HEV with four-wheel drive (4WD) uses both a conventional internal combustion engine and an electric motor. Th e latter functions as an alternator, drive unit and starter motor. Both propulsion systems transfer their power via a clutch to the transmission system.

193 Usually, HEVs start off using the electric motor, then the mineral fuel engine cuts in as load or speed rises. Th e two motors are controlled by an internal computer which ensures the best economy for the driving conditions. Oft en the energy for the electric engine is provided by the car’s own braking system to recharge the battery. Th is is called regenerative braking, a process which converts some kinetic energy into electric energy for the battery pack. Th e Honda Civic Hybrid and Toyota Camry Hybrid are both examples of HEVs, as are the older versions of Toyota’s Prius, one of the highest-volume and most successful electrifi ed cars sold until now.

Plug-In Hybrid Electric Vehicles (PHEVs) PHEVs are similar to conventional hybrids in that they have both an electric motor and an internal combustion engine, except that PHEV batteries are larger and can be charged by plugging them into an outlet. So why opt for a PHEV instead of a conventional hybrid? Well, unlike conventional HEVs, PHEVs

THEME 2.3.1 THEME can substitute electric power from the grid with mineral fuels. Th eir range is however limited before the combustion engine kicks in, usually between 50 – 100 km on a full charge (full electric km of range). Th ough this does not sound like a great distance, many people living in metros drive less than this distance each day. Almost all car manufacturers nowadays off er PHEVs: Audi (A3 E-tron), BMW (330e, X5 xdrve40e and the sleek futuristic supercar i8), Chevy (Bolt), Chrysler (Pacifi ca), Ford (C-max energy), Hyundai (Ioniq and Sonata), Kia (Niro), Mercedes (C350, S550 and GLE550e), Mitsubishi (Outlander), Porsche (918 Spyder, Cayene S and Panamera S), Toyota (Prius Prime), and Volvo (XC90 T8).

F I G U R E 7: SIMPLIFIED PHEV DESIGN CONCEPT (FWD SCHEMATIC)

Air High-voltage battery conditioning compressor

Combustion engine Electric motor 2

Electric Gearbox motor 1 Power electronics 2

Battery Power electronics 1 High-voltage lines Charging contact charger

Image source: S4GJ/GIZ Th is type of PHEV design is unusual in that it uses a twin drive, i.e. two electric motors. One of the electric motors is used exclusively as an alternator or starter and the other electric motor is used as an electric motor and alternator. Th e two electric motors and the combustion engine are connected to each other via clutches. Th e high-voltage battery in the PHEV can also be charged via an external outlet or charge station.

194 Battery Electric Vehicles (BEVs) Battery electric vehicles run exclusively on electric power via on-board batteries that are charged by plugging them into an outlet or charging station. Smaller and medium cars such as the BMW i3, Chevy Spark EV, Mercedes B Electric, Nissan LEAF, Fiat 500e, Ford Focus Electric, Kia Soul EV, Mitsubishi iMiEV, Smart Electric Drive, and VW e-Golf fall into this category, though there are many other BEVs on the market. Th ese type of vehicles have no combustion engines, but have longer electric driving ranges compared to PHEVs. Th ough there are emissions associated with charging BEVs, they never produce tailpipe emissions and are thus ideal for inner-city and city-to-city commuting. Th e BEVs currently on the market reach around 100 to 200 km per full charge, though the new generation models, such as the Tesla Model S, can travel over 350 km on a single charge. As battery technology continues to improve, BEV ranges will extend even further, off ering an even larger number of drivers the option of driving exclusively on electric power. THEME 2.3.1 THEME FIGU RE 8: SIMPLIFIED BEV DESIGN CONCEPT (FWD SCHEMATIC)

High-voltage battery

High-voltage heating system

Power electronics

Air conditioner compressor

Electric motor High-voltage lines Charging contact Battery with gearbox charger

Image source: S4GJ/GIZ A BEV is a purely electric-powered vehicle without a combustion engine. Th is type of BEV design uses a front-wheel drive (FWD), while other designs, such as the Tesla models, are based on rear-wheel propulsion. Please note that all electric cars are also available in 4WD, for example Tesla’s model X. Th e large battery can either be positioned as indicated in the drawing or can be located along the fl oor section. Th e battery can only be charged using regenerative braking or an external power source. Th e electric motor powers the drive chain directly via a transmission and diff erential. Th e driver operates the vehicle exactly the same way as a vehicle with an automatic transmission.

195 Fuel Cell Electric Vehicles (FCEVs) FCEVs use an electric-only motor similar to a BEV. However, instead of recharging a battery via an outlet or a charging station, FCEVs store and use hydrogen gas as fuel (Figure 4). Th e fuel cell stacks in FCEVs provide electric power to the electric motor, which powers the vehicle just like a BEV. And like BEVs, there is no emission forming from FCEV tailpipes - the only by-product is water (Figure 5). Refi lling with hydrogen can take as little as 5 minutes at a fi lling station. But similar to charging PHEVs or BEVs from non-renewable resources, producing hydrogen also generates emissions. However, producing hydrogen from renewable sources via electrolyses can produce an alternative and nearly emission-free fuel. Moreover, hydrogen fuelling infrastructure, similar to public electric vehicle charging stations, needs to be developed. With increased public policies aimed at getting more of these vehicles on the road, FCEVs can become a large part of future transportation systems. Th e Hyundai Tucson, its ix 35 and Toyota Mirai are both examples of passenger car FCEVs. Other examples include fuel cell powered busses (Toyota/Hino, Tata, Citaro/Daimler/Ballard Power, Th or Industries, Irisbus etc.), trains (Alstrom/Coradia iLint) and

THEME 2.3.1 THEME marine vessels such as the Zemships (see Topic 1) and submarines (HDW Type 212 and 214).

FIGURE 9: SIMPLIFIED FCEV DESIGN CONCEPT (FWD SCHEMATIC)

High-voltage battery Air conditioning compressor

Power electronics

High-voltage heating Fuel system cell

Electric motor High-voltage lines Hydrogen fuel tank

Image source: S4GJ/GIZ Th e FCEV is fuelled with hydrogen and obtains the electrical energy for the electric motor from a fuel cell module stack. Th ere is no combustion engine. Th e high-voltage battery can also be charged externally via a special battery charger.

EV Market Overview Global Markets Currently, passenger EVs are available in over 40 markets with over 100 model specifi cations. Th ese include all global BEV and PHEV passenger car sales, light trucks in the USA/Canada and light commercial vehicles in Europe. Th e number of plug-in electric cars on the world’s roads surpassed the 2 million vehicles landmark at the end of 2016. As indicated in Figure 3, China has overtaken the EU and US in market size. In terms of electric car adaptation, Norway is the world leader and has shown how fast a national car market can shift to EVs. One in three new cars sold in Norway are now EVs, a proportion that is rising every month, spurred on by big tax breaks for new EVs and a major nation-wide investment in charging infrastructure. Norway and the Netherlands, which is also an EV market leader, both aim to

196 phase out all new fossil-fuel car registrations by 2025. Th e world’s bestselling EVs in the fi rst half of 2016, according to sales statistics from EV-Volumes.Com, were the Nissan Leaf, followed by the expensive Tesla Model S. But the third and fourth spots were taken by models from the Chinese fi rm Build Your Dreams (BYD), with the Tang SUV and the Qin model. Chevrolet’s Volt took fi ft h place.

EU Markets Th e plug-in share in Norway is off the charts (Figure 10). No other country comes close to the 24% share which Norway has achieved during 2016. Nearly one quarter of 2016 car and light commercial vehicle (LCV) sales were EVs, including a BEV share of 13% and a PHEV share of 11%. Th e Netherlands retains its 2nd rank in Europe. Among the big 5 EV markets in Europe, France clearly leads, followed by the U.K., Germany and Italy. In nearly all European markets, PHEVs grew faster than pure BEVs. THEME 2.3.1 THEME FIGURE 10: SHARES OF EV SALES IN EUROPEAN MARKETS (2016)

BEV PHEV Volume Change vs 2015

0 % 1 % 2 % 3 % 4 % 5 % BEVs PHEVs

Norway Norway has 24 % combined share, 13 % for EV, 11 % fpr PHEV - 5 % + 163 %

Netherlands + 5 % - 52 %

Iceland - 7 % + 323 %

Sweden - 1 % + 85 %

Switzerland - 12 % + 6 %

Belgium + 45 % + 228 %

Austria + 122 % + 20 %

France + 26 % + 28 %

UK + 4 % + 54 %

Finland - 4 % + 191 %

Portugal + 12 % + 109 %

Germany + 13 % + 21 %

Luxembourg + 273 % + 309 %

Denmark - 72 % + 28 %

Ireland - 17 % + 205 %

Spain + 39 % + 98 %

Italy + 14 % + 77 %

Others + 64 % - 1 %

Total Europe + 8 % + 20 %

Image source: S4GJ/GIZ (Data by EV-Volumes.Com)

Chinese Markets China has not only become the biggest automotive market in the world, but also the biggest EV market in the world. In 2016, the country’s fl eet of EVs stood at around 650 000 units. You probably have not heard much about EV types sold in China - we will thus introduce you to three of China’s largest all-electric vehicle (BEV) manufacturers.

197 Plug-in hybrids still dominate the Chinese EV market with Build Your Dreams’ (BYD’s) Tang and Qin models still holding the two top sales spots with over 20 000 new deliveries each in 2016. But China’s EV market diff ers in its variety of EV models on off er. Over 60 EV models are available and 13 of these models have sold over 10 000 units in 2016. In comparison, only 5 EV models sold more than 10 000 units in the US in 2016, including Tesla’s Model S, Tesla’s Model X, Chevy’s Volt, Ford’s Fusion Energi, and the Nissan LEAF. While BYD’s plug-in hybrids dominate, some BEVs have made progress in 2016. BYD’s e6 for example is a compact cross-over with an updated powertrain, including a 82 kWh battery pack which might reach a range of over 350 km. Aft er BYD, Geely is probably the second most well-known Chinese carmaker outside of China, especially since its acquisition of Volvo. 2016 was the fi rst full year of production for its Emgrand EV, which is based on its LPG-powered sedan version. Th e BEV is equipped with a 45 kWh battery pack suﬃ cient for a 250 km range. Geely managed to deliver 12 000 units of this BEV in 2016. Th e company has been working with Volvo to develop a new EV platform architecture which might form the base for a

THEME 2.3.1 THEME successful BEV production programme. Beijing Automotive Group, also known as BAIC Group, is a state-owned automaker with joint-ventures of global car brands like Mercedes and Hyundai. Its EU260 model arrived in 2016 and held the top spot for BEVs with over 18 000 deliveries.

Overall, one can expect Chinese EV manufacturers to step up their production ranges in the next few years, as the national government is preparing to let foreign manufacturers build EVs in China without having to share technology with a local joint-venture. Th is move is likely to increase competition and consequently the quality of EVs available in the Chinese car market. Given the extremely high levels of air pollution in the inner cities, BEVs are a priority for China’s transition to electric propulsion.

Japanese Markets Th e Japanese EV market consists almost entirely out of Japanese car manufacturers. Over the past few years, the Nissan LEAF for example has dominated the market. Although the fi rst generation Toyota Prius PHEV had respectable sales, together with the release of the Toyota Prius Prime, the second generation PHEV version of the Prius might be just as successful. One could thus expect that Nissan will produce a second generation LEAF model, with for example a 40 kWh-plus version.

US Markets In 2016, 30 diff erent EV models were on off er and with far over half a million EVs, the US is the third largest EV market. Five diff erent models sold at least 10 000 units, including Tesla’s Model S, Tesla’s Model X, Chevy’s Volt, Ford’s Fusion Energi, and the Nissan LEAF. More than half of all EV sales took place in California, driven by the state’s zero-emission vehicle (ZEV) mandate, which requires a certain percentage of car manufacturers’ sales to be ZEVs. California’s goal is to put 1.5 million ZEVs on the roads by 2025. Th is is a very ambitious target and it is anyone’s guess if other federal states will follow the Californian example (probably not).

Your own notes

198 Exercises

1. Briefl y explain the relevance of alternative fuels for modern mobility concepts.

…………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… THEME 2.3.1 THEME ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………

2. Which alternative fuel options do you know? …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

3. Briefl y explain why fuel cell technologies are relevant for e-mobility concepts. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

199 4. Use the following component symbols and place them (draw) in the correct positions in the vehicle drawings so that you can illustrate three diff erent EV types.

Components Symbols Components Symbols THEME 2.3.1 THEME

Power electronics Battery charger

High-voltage Charging contact lines

High-voltage Fuel cell stack battery

Gearbox Electric motor

Combustion Fuel tank engine

200 Fuel Cell Electric Vehicle (FCEV) THEME 2.3.1 THEME

Battery Electric Vehicle (BEV)

Plug-In Hybrid Electric Vehicle (PHEV)

201 Further Information on the Resource CD

(i) Video: 2017 Chevrolet Bolt EV Animation (mp4) (ii) Video: BMW i3 Electric Car Animation (mp4) (iii) Electric vehicles in Europe: gearing up for a new phase? McKinsey & Company (2016) (iv) Electro-mobility in Germany: Vision 2020 and Beyond, www.gtai.com (2015) (v) Towards Low-Emission Mobility, Driving the Modernisation of the EU Economy, EPSC Strategic Notes, Issue 17, 20 July 2016 (vi) Global EV outlook 2016, Beyond one million electric cars, OECD/IEA, 2016 THEME 2.3.1 THEME

Your own notes

202 THEME 2.3.2 ESSENTIAL E-CAR COMPONENTS AND THEIR FUNCTIONS

Introduction

At fi rst glance electric vehicles (EVs) look quite similar to vehicles powered by internal combustion engines (ICE). Th e chassis or body of many electric vehicles on the road today come from vehicles that once contained an ICE. In most electric vehicles, even the interior has remained unchanged and almost all electric vehicles contain the same accessories as their internal combustion cousins. However, an EV can

operate far more eﬃ ciently and environmentally friendly than an ICE car, while off ering more immedi- 2.3.2 THEME ate torque (rotational force) and smooth power delivery compared to ICEs. Th e electric powertrain and its electronic control system, as well as the rechargeable battery supplies and its management and unique system components such as regenerative braking, makes the EV’s design unique and fundamentally different to ICE cars. Th ere are however also major disadvantages in EV technology, for example the relative weight of batteries compared to an equivalent tank of fuel. In this last theme of Topic 2 we will introduce you to the essential components of an EV powertrain and their functions.

Keywords

EV powertrain Control systems Regenerative braking Single-pedal speed control Batteries Charging infrastructure FCEV components External circulating humidifi er (previous system) Fuel cell boost converter High-pressure hydrogen storage tanks Hydrogen refuelling

Theme Outcomes

At the end of this theme, you should be able to explain the functionality of an EV’s key components.

Deﬁ nition of Terms EV Powertrain of BEVs Th e powertrain of a motor vehicle includes by defi nition both the engine or motor and the drivetrain. Th e latter is the group of components that deliver power to the driving wheels (clutch, transmission, diff , shaft s etc.).

203 FIGURE 1: POWER TRAIN, I.E. ENGINE AND DRIVETRAIN OF A CONVENTIONAL ICE CAR (FWD)

Differential Driveshaft U-joint U-joint Balancer

U-joint U-joint

THEME 2.3.2 THEME Engine

Transmission

Fywheel / Clutch

Image source: S4GJ/GIZ (adapted aft er Wikimedia, https://upload.wikimedia.org/wikipedia/commons/5/5d/Transverse_engine_ layout.png)

An EV’s drive system performs the same functions as that of a vehicle powered by an internal combustion engine (Figure 1), i.e. transmitting mechanical energy to the traction wheels. However, the components used in an EV powertrain are very diff erent to a standard ICE vehicle (Figure 2).

FIG U RE 2: POWERTRAIN OF A MODERN BEV

Image source: https://upload.wikimedia.org/wikipedia/commons/f/f3/Tesla_Motors_Model_S_base.JPG Tesla’s model S chassis, showing the rear powertrain in front and the battery unit located in the fl oor section between the front and the rear axles.

204 Modern BEVs use three-phase AC synchronous motors, composed of a magnet rotor and coil stator (see also Th eme 2.1.3 and Figure 3 below). Passing a current through the motor turns the stator into an electrical magnet and generates magnetic force. Th rough this magnetic force, the rotor turns and produces dynamic power. Th e stronger the magnetic force, the higher the torque (rotational force). Similar to wind turbine generators, as indicated in Th eme 2.1.3, the two main methods of raising magnetic force are (i) using a powerful permanent magnet, and (ii) applying a powerful current. Th ese facts also apply to electric motors in BEVs, given that a large amount of power is required to move an object as heavy as a car. Th erefore, high output lithium-ion batteries are generally used for EVs and their electric engines (Figure 3) use powerful permanent magnets to enhance magnetic force.

FI G U R E 3: THREE-PHASE AC SYNCHRONOUS PANCAKE MOTOR FOR A MODERN BEV THEME 2.3.2 THEME

Image source: http://wonderfulengineering.com/download-electrical-motor-images-free-here/

Currently, there are several diff erent drive system designs in use, including EVs with single large electric motors coupled to the rear wheels through a diff erential housing. Other designs utilise two smaller electric motors to power each wheel separately through independent driveshaft s. Th e most eﬃ cient design to date utilises powertrains which are attached directly to the wheel. Th ese are referred to as in- wheel motors. By eliminating drive shaft s and diff erentials, mechanical losses between the motor and wheels are minimised. While standard ICE vehicles require transmission units to provide the vehicle with a certain torque (rotational force) at certain speeds by changing the gear input/output ratio, modern BEVs do not need sophisticated transmission technologies. In EVs the change in gear ratio is governed by the speed (RPM) at which the vehicle’s electric engine is turning. Transmission units add complexity and weight to a car and also reduce its eﬃ ciency due to friction/mechanical losses. It is thus an advantage that EVs do not require major transmission systems, driveshaft components, and in some designs, not even axles or diff erentials. Further, the powertrain of newer EVs integrates the electric motor, inverter, reducer and power delivery module (PDM) into a smaller and lighter package. Th is integration reduces the number of moving parts, such as the driveshaft , as well as some high-voltage components, while also optimising the torque output of the motor and the reduction gear ratio.

205 FIGURE 4: IN-WHEEL ELECTRIC MOTOR FOR A MODERN BEV THEME 2.3.2 THEME

Image source: https://upload.wikimedia.org/wikipedia/commons/2/27/Honda_FCX_rear_in-wheel_motor_Honda_Collection_ Hall.jpg

Control Systems Th e most complex and important system in an EV is the control system. Th e control system is responsible for governing the operation of the electric vehicle. Th e control system receives inputs from the operator, feedback signals from the motor module and other systems within the EV. Th e control system must receive and process data from other systems in milliseconds. Th is requires the control system to contain a microprocessor, just like a computer. Th ough no two control systems are identical, most of the feedback signals are similar. Table 1 lists common components of a control system and the feedback signals that are sent to the microprocessor.

TA BLE 1: EXAMPLES OF FEEDBACK SIGNALS SENT FROM EV COMPONENTS TO THE CONTROLLER SYSTEM

Components Feedback signal Winding temperature Rotor speed (RPM) Electric motor Current (and direction of current) Potential difference Potential difference Traction battery Output current Temperature Accelerator pedal Potential difference as a function of pedal position FWD/REV Shift selector Range selection

206 Th e control system must continuously monitor the various feedback signals. For instance, if the temperature of the windings in the motor gets too hot, the magnetic properties of that motor can be permanently altered or the windings may melt. By feeding a signal back to the microprocessor, the control system can limit the output of the motor if it senses a temperature rise. Th e same limiting or shutdown of any system can take place if an undesirable condition is or has occurred. Other feedback signals send information to the microprocessor to control the speed of the vehicle. Th e accelerator pedal functions in much the same way as in conventional vehicles: as the pedal is depressed, an increasing signal (potential diff erence) is sent to the microprocessor, which instructs the motor controller to increase the amount of current in the motor windings, causing the motor to spin faster. As the signal from the accelerator pedal is decreased, the motor spins slower.

Early controller versions used a simple variable resistor type of controller governing the acceleration and speed of the EV. Full current and power was drawn from the battery at all time. At lower speeds

when little power was needed, high resistance was used to reduce the current to the motor. Th is resulted 2.3.2 THEME in a large percentage of the battery’s energy being wasted as heat dissipated by the resistor. Modern controllers adjust speed and acceleration through an electronic process called pulse width modulation (PWM). Switching devices such as very fast, high-current rated transistors rapidly interrupt, turning the fl ow of current to the motor on or off as needed. High power is achieved when the intervals (time between pulses) are very short. By increasing the time between pulses, the current is limited.

In these advanced control systems, it is possible to limit the amount of current that fl ows to the motor, based on a switch selection. Th is allows the operator to adjust to a driving style that fi ts a particular situation. For instance, if a driver needs a certain range (in km) from a single charge, the range selection can be set so that the microprocessor will limit the amount of output current from the motor controllers to a preset limit. If the preset limit is, for example, set at 100 A, the microprocessor will not allow any current above this limit to fl ow to the motors. In this mode, acceleration ability is sacrifi ced for range. If the driver is in an area where the vehicle must climb steep grades, the range selector can be set so that the maximum current capability of the motor controller and motor can be used. Th e range selection feature adds to the eﬃ ciency of the motor controller. Th e ultimate goal of a control system is to maximise the energy stored within the traction battery and to prevent unsafe conditions from occurring within the electric vehicle.

Regenerative Braking Every time a vehicle’s brakes are applied and the vehicle slows down, the kinetic energy that propelled it forward is transformed and dissipates as heat, thus becoming useless for vehicle propulsion. Th is amount of energy, which could have been utilised to do work, is essentially no longer available for the application. Let us explain the matter in a more concrete way: In a traditional braking system, brake pads produce friction in the brake’s drum or disk to slow or stop the driveshaft and ultimately the vehicle. Th us, with the application of friction, kinetic energy is converted into heat energy. With regenerative brakes in EVs on the other hand, the system that drives the vehicle can also do the majority of the braking. How does this work?

207 FI G U R E 5: ACCELERATION AND MAGNETIC BRAKING SIMPLIFIED

S N N S S N S Power flows N into motor N S THEME 2.3.2 THEME S N

N S N Power flows out of motor S S S N N N S N S

Image source: S4GJ/GIZ – Stator = orange, Rotor = blue. Th e top drawing in Figure 5 illustrates acceleration in an electric motor. Th e stator’s rotating magnetic fi eld leads the rotor’s magnetic poles. Consequently, the magnetic forces act in the same direction as the shaft ’s rotation. Subsequently, the car moves or accelerates forward at a constant pace. Th e bottom drawing indicates magnetic braking. Th e stator’s rotating magnetic fi eld lags the rotor’s magnetic poles. Consequently, the magnetic forces act in the opposite direction to the shaft ’s rotation. Subsequently, the car slows down.

We outlined the working principles of motors and generators in Th eme 2.1.3, indicating that motors and generators are electromechanical energy conversion devices that have a lot in common. Consequently, a motor can be converted into a generator and vice versa. Let us quickly recall: In a motor, a current passes through the coil or is induced in the rotating coils, generating torque. In a generator, the mechanical turning of a coil in a magnetic fi eld produces an electromotive force (emf) in the coil. Th us, the rotation of the coil continually changes (sinusoidal) the magnetic fl ux through the coil, thereby generating a potential diff erence. Electric motors when operated as generators convert mechanical energy into electrical energy. Th is principle is used in regenerative braking. However, the term regenerative braking does not really explain why an EV slows down when the acceleration pedal is fully lift ed/off the fl oor (single-pedal speed control). With conventional brakes, it is friction that slows down the car. With the EV, it is magnetic force that slows down the vehicle. How does this work? Th e armature of the motor is slowed down by the force of inducing current (emf) in the windings as it passes over the opposing poles of the magnets in the stator (Figure 5). In other words, when electric power to the motor is cut, the stator’s rotating magnetic fi elds continue in the same direction as the rotor rotation, but the motor’s electronic controller directs the stator’s magnetic poles to lag behind the rotor’s opposite poles.Th e magnetic forces now pull against the direction of shaft rotation (magnetic braking).

208 Single-Pedal Speed Control Single-pedal speed control uses magnetic braking and the brake pedals only control the friction brakes, which most EVs also have as a kind of backup system in situations where regenerative braking simply cannot supply enough stopping power. Th e vehicle’s electronics must therefore decide which braking system is appropriate at which time. It is even possible for the driver to select certain presets to determine how the vehicle reacts in diff erent situations. For instance, in some vehicles a driver can select whether regenerative braking should begin immediately when the driver’s foot comes off the accelerator pedal and whether the braking system will take the car all the way to a stop or will let the car coast slightly. Oft en regenerative braking is implemented in conjunction with anti-lock braking systems (ABS), so the regenerative braking controller is similar to an ABS controller which monitors the rotational speed of the wheels and the diff erence in that speed from one wheel to another. Th e brake controller thus not only monitors the speed of the wheels, but can calculate how much torque is available to generate electric power that is fed back into the batteries.

Designing a single pedal to control an EVs’ speed, i.e. either up or down or constant, is consequently 2.3.2 THEME mainly based on soft ware. Writing that soft ware requires some real talent. Determining the path, frequency and strength of electric power into and out of the motor, which in turn controls the magnetic fi elds in the motor making it go faster or slower is fully electronically controlled.Th is is the direction modern automotive engineering is taking.

FIGURE 6: SINGLE-PEDAL SPEED CONTROL MECHANISM

Max Power to motor to Power Coasting 0 Magnetic braking Magnetic

Max Lift off Pedal travel To fl oor

Image source: S4GJ/GIZ

209 Batteries Battery prices have fallen dramatically already and in 5-10 years, they are likely to be made suﬃ ciently small and cost-eff ective for EVs to become aff ordable for the average consumer (Figure 7 and 8). Lithium-ion batteries are crucial for EVs and for storage solutions. It is estimated that global production capacity will increase dramatically between 2016 and 2020. Production will take place in so-called mega- or gigafactories with annual production capacities between 1 and 54 GWh. In 2016, Tesla’s fi rst gigafactory was the centre of attention for its growing momentum behind green energy, electric cars and battery production. However, as exciting as this project is, it is actually just one of multiple large-scale factories being built, most of them in China. All lithium-ion plants in China currently have a capacity of 16.4GWh, but by 2020 they will combine to a total of around 108 GWh.

F I G U R E 7: ESTIMATIONS FOR BATTERY COST REDUCTIONS AND

THEME 2.3.2 THEME PERFORMANCE IMPROVEMENTS

2015 2020

Battery cost 14,250 USD -63%

5,250 Battery weight 250 kg -52%

120 Battery capacity 30 kWh

20 +50% Battery range 275 km

160 +72%

Image source: S4GJ/GIZ aft er Goldman Sachs (2016)

210 FIGU RE 8: GROWTH PROJECTION FOR LITHIUM BATTERIES (PRODUCTION CAPACITIES IN GWH)

CHINA USA (108 GWH) (38 GWH) 62%

22% 2.3.2 THEME

13% 3% S.KOREA (23 GWH)

POLAND (5 GWH)

Image source: S4GJ/GIZ (Data by Benchmark Mineral Intelligence 2016)

FIGURE 9: CUTAWAY OF AN EV SHOWING THE FLOOR POSITION OF THE BATTERY UNIT

Image source: https://upload.wikimedia.org/wikipedia/commons/f/fe/Nissan_Leaf_cutaway_at_FutureFest_2016_01.jpg

211 Charging Infrastructure A high-voltage vehicle can consume between 3.3 kW and 10 kW of electrical power while the high-voltage battery is being charged. Normal household sockets have one phase and supply a maximum current of 16 A at 230 V (AC).

P (single-phase) = U x I = 230 V x 15 A* [1 VA ~ 1 W] = 3450 W = 3.45 kW (absolute)

* In a residential setting the standard DB has a rated main circuit breaker (main switch) of 60 A. Light circuits normally have 10 A, geyser and plug circuits 15 – 20 A and the stove circuit 35 A. Th e diff erent ratings are designed to prevent overload and associated risks. Due to electrical losses during charging (power dissipation), the value must be corrected to 3.4 kW of

THEME 2.3.2 THEME the absolute value.

If the BEV can be charged using a three-phase socket, for example via a charging station or an industrial outlet, electrical power increases. As a result, the charging process is shorter. In a symmetrical three- phase four-wire system, the three-phase conductors have the same voltage as the system neutral. Th e voltage between line conductors is √3 times the phase conductor to neutral (potential diff erence). Th us, when calculating power (VA) in a three-phase installation, a factor of 1.73 is introduced (√3 = 1.73, 230V x √3 = 400 V).

P (three-phase) = 400 V x 15 A x 1.73 = 10380 W = 10.38 kW

FIGURE 10: TWO DIFFERENT CHARGING CABLES (400 V LEFT AND 230 V RIGHT)

Image source: S4GJ/GIZ

212 FIGU RE 11: SIX DIFFERENT CONNECTOR TYPES (FROM LEFT TO RIGHT: US, EU, CHINA AND JAPAN) THEME 2.3.2 THEME

Image source: S4GJ/GIZ - Across the world a large number of diff erent connector types are used for a wide range of EVs.

FIG U RE 12: STANDARD VDE THREE-PHASE CONNECTOR FOR CHARGING BEVS

Ground Pilot line Neutral

Phase L1

Phase L2

Phase L3

Image source: S4GJ/GIZ - VDE = Association for Electrical, Electronic & Information Technologies During the charging process, the vehicle body is grounded for electrical safety via the electrical connection (protective conductor). Th e safety contact of the charging connector activates the charger in the vehicle. Th e vehicle cannot be driven when the cable is connected. Th e connector contacts are scoop- proof with deep sockets to prevent connector cocking angle. In addition, a pilot line is used. Th is type of connector and charging socket on the vehicle allow a charging process to be performed safely in any weather conditions.

213 FCEV Components

FI G U R E 13: FCEV COMPONENTS SIMPLIFIED (SCHEMATIC)

POWER CONTROL UNIT FUEL CELL BOOST CONVERTER BATTERY to optimally control both is used to obtain an which stores fuel cell stack output output with higher energy recovered under various operational voltage than the input from deceleration conditions and drive battery and assists fuel charging and discharging cell stack output during acceleration THEME 2.3.2 THEME

O2 H2O

E-MOTOR HIGH-PRESSURE powered by fuel cell HYDROGEN stack and battery FUEL CELL STACK TANKS

Image source: S4GJ/GIZ

Fuel Cell Boost Converter Th e development of a high-capacity fuel cell boost converter made it possible to increase the voltage of the motor, reduce the number of fuel cell stack cells and reduce the size and weight of the system. Inno- vations to the voltage-boost control and case structure also result in exceptionally quiet operation.

High-Pressure Hydrogen Storage Tanks In modern FCEVs, lighter weight storage tanks show a more favourable ratio of storage mass per tank weight (hydrogen storage density) than in earlier models. Th is has been achieved through innovations based on various layer structures, including a plastic liner to seal in hydrogen, a plastic layer reinforced with carbon fi bre to ensure pressure resistance and a glass fi bre layer to protect the outer surface of the tank.

Hydrogen Refuelling In response to new hydrogen fuelling standards (Japan, the US, and Europe), fuelling times of approximately 3 minutes can been achieved but vary based on ambient temperature fuelling pressure. Hydrogen fuelling under the new standards (SAEJ 2601) relies on an advanced control system, based on various feedback loops and communication fl ows (Figure 14).

214 FIGURE 14: HYDROGEN FUELLING CONTROL SYSTEM FOR FCEVS (SIMPLIFIED)

Pressure Tank sensor information Infrared ray Temperature transmitter H 2.3.2 THEME sensor 2 Hydrogen Nozzle High-pressure hydrogen tank Communication functions given to Vehicle Hydrogen station

Image source: S4GJ/GIZ

Your own notes

215 Exercises

1. Briefl y explain why electronic control systems are important for EVs.

…………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… THEME 2.3.2 THEME …………………………………………………………………………………… ………………………………………………………………………………………

2. Briefl y explain the single-pedal speed control mechanism.

3. Briefl y explain the principle of regenerative braking.

Further Information on the Resource CD

(i) Video: EN - Bosch Regenerative Braking (mp4) (ii) Video: Hyundai Sonata Hybrid Motor Animation (mp4)

216 Your own notes NOTES

217 Your own notes NOTES

218 TOPIC

Occupational Health and Safety

Topic Overview

As discussed in the previous two levels of Renewable Energy Technologies (RET), the Occupational Health and Safety Act (OHS) regulates responsibility for health and safety at the workplace. The OHS Act not only outlines the workers’ rights in terms of health and safety, but also indicates the employee’s responsibilities to avoid dangerous situations and to take appropriate precautions, e.g. against the risk of falling from heights. The RET industry segments are growing, and subsequently more and more people will be employed - health risks at the workplace will thereby also potentially increase. It is therefore important that you know and understand the relevant hazards and safe work practices related to wind turbine, fuel cell and e-mobility technologies.

Topic 3 covers the following units: Unit 3.1 Hazards and Safe Work Practices related to Wind Turbine Technologies Unit 3.2 Hazards and Safe Work Practices related to Fuel Cell Technologies Unit 3.3 Hazards and Safe Work Practices related to E-Mobility Technologies

219 Unit 3.1 Unit 3.1 covers the following two themes: two Unit 3.1 following covers the Themes in this Unit able you to: be should unit, end ofAt this the Unit Outcomes at risk. health and safety their put could have appropriately not trained been they for which processes workers in involved experienced or new less the Especially work environment. this in exist that hazards of the aware mayers not fully be sector, some work- industry new arelatively is energy wind that Considering to completely hazards. new lead however potentially energy wind with associated processes or working New technologies same. the often are industries to other compared challenges but the unique, are turbines wind dismantling possibly and servicing maintaining, erecting, of sitting, aspects (OHS) Many concern. aprime safety becomes and health occupational to management, project maintenance and installation logistics, manufacturing, from ranging sector energy wind of the aspects of workers number now employed various creasing in in- an to emerge. With begin to grow, continues challenges new industry energy wind global the As Introduction TO WIND TURBINE TECHNOLOGIES RELATED PRACTICES WORK SAFE AND HAZARDS 3.1 UNIT Theme 3.1.2 to Wind related Safe WorkTurbine Practices Technologies Theme 3.1.1 to Wind related Turbine Hazards Technologies (iii) (ii) (i)

Ex technologies. Ex Ex plain how employees can be involved in health and safety processes and procedures. and processes safety and health in involved how be employeesplain can turbine to wind related harm any from employees safe toare ensure steps practicable plain technologies. turbine to wind related hazards workplace plain

THEME 3.1.1 HAZARDS RELATED TO WIND TURBINE TECHNOLOGIES

Introduction

Wind energy is a renewable technology and far less harmful to the environment and climate compared to fossil fuel technologies. Just as in any other type of industry, wind energy workers can be exposed to hazards that could result in fatalities and serious injuries during the various phases of wind turbine projects. Th e objective of this theme is thus to provide an overview of the OHS challenges in the wind energy sector, focussing on small-scale turbine installations, in order to raise your awareness. THEME 3.1.1 Keywords

Risks and hazards Safety hazards Chemical hazards Transportation hazards Construction hazards

Theme Outcomes

At the end of this theme, you should be able to explain workplace hazards related to wind turbine technologies.

Deﬁ nition of Terms Risks and Hazards Occupational health and safety (OHS) issues associated with wind turbine technologies include working in remote areas, extreme weather conditions, confi ned spaces, awkward postures, electrical risks, falls from height, musculoskeletal disorders, physical and psychosocial loads, various aspects of work organisation and exposure to dangerous substances at the production stage and also during maintenance operations. A risk can be defi ned as the probability of being injured. Hazards comprise the potential of work equipment or processes to cause harm to people or damage to property or the environment.

Safety Hazards When working on wind turbines there are various safety hazards that you could face, including: (i) Electrical hazards: Workers in the wind power industry are exposed to a variety of potentially serious electrical hazards. Oft en, these include electrical shock and severe burns from arc fl ashes. Falls and also crushing injuries have been reported as a result of these injuries. (ii) Falling hazard: Workers who erect and maintain wind turbines work at heights and are thus exposed to falls with potentially dangerous consequences (serious injuries or death).

Th ese two types of safety hazards, i.e. electrical and falling hazards can result in fatalities and serious injuries. Th e examples given below illustrate the diﬀ erent fatalities and incidents which can occur:

(i) An excavator was being oﬀ -loaded from a trailer. Th e trailer was parked on a rural road adjacent to an access road for a wind turbine. Th e excavator operator rotated the upper works of the machine prior to moving the machine oﬀ the trailer. During the rotation, the boom accidentally made contact with an 11kW power line. At the same time, a worker touched the trailer and received a severe electric shock. He sustained entry wounds in his hands and exit wounds in his feet and was transported and admitted for observation to a local hospital 200 km away from the work site.

221 (ii) A technician was checking the electrical connections of a turbine and came into contact with a bus bar. An arc fl ash erupted, causing severe injury to the victim. He had to be taken to hospital and treated for his injuries. (iii) A worker and two co-workers were removing and replacing a broken bolt in the turbine nacelle approximately 60 meters above the ground. As they were heating the bolt with an oxygen-acet- ylene torch, a fi re started. One worker retreated to the rear of the nacelle, away from the ladder access area. Th e two co-workers were able to descend the tower. Th e worker that was trapped by the fi re fell to the ground and struck an electrical transformer box. He was declared dead on the scene. (iv) An electrician descended the ladder that accessed the nacelle when he slipped and fell from the ladder. He was wearing his company-furnished safety belt, but the safety lanyards were not attached. Both lanyards were later discovered attached to their tie-oﬀ connection at the top of the nacelle.

THEME 3.1.1 (v) A site foreman replacing a 400 V circuit breaker turned the rotary switch to what he thought was the open position in order to isolate the circuit breaker. However, he did not test the circuit to ensure that it was de-energised. Unfortunately, the rotary switch was now in a closed position, and the circuit breaker remained energised by backfeed from a transformer. Using two plastic- handled screwdrivers, the foreman shorted two contacts on the breaker and caused a fault. Th e resulting electric arc caused deep fl ash burns to his face and arms and ignited his shirt. He was hospitalised and remained in a specialised burn unit for some time.

Chemical Hazards Chemical hazards are present when a worker is exposed to chemical substances be it solids, liquids or gases. Th ese substances can have dangerous health eff ects and could cause illnesses, skin irritation or breathing problems. Most hazardous chemicals routinely referred to in the wind turbine industry are epoxy-based resins and glass-reinforced plastic (GRP). Epoxy resins are synthetic chemicals traditionally used in paints, glue or composite materials. Th ey are oft en used in the manufacture of wind turbine system components. Th ere is a risk of contracting contact allergy and dermatitis when using these chemicals. Wind turbine blades are produced from GRP. Th e GRP manufacturing process is relatively simple, but worker exposure to the solvent (styrene) vapour which is released during the process, is notoriously diffi cult to control. In addition to chemical hazards from exposure to epoxy resins, styrene and solvents, there are also other harmful gases, vapours and dusts created during manufacture, installation and maintenance processes to consider. Dust and fumes from fi breglass, hardeners, aerosols and carbon can cause problems, including dermatitis, dizziness, drowsiness, sleepiness, liver and kidney damage, blisters, chemical burns and negative reproductive eff ects.

FIGURE 1: PPE REQUIRED FOR WORKING WITH RENEWABLE ENERGY TECHNOLOGIES

Image source: S4GJ/GIZ. Th e above illustrates the minimum PPE required for working with renewable energy technologies.

222 OHS Risks associated with the Transportation of Wind Turbine Components Th e movement and handling of some very heavy and/or large wind turbine components is a substantial logistical challenge and bears potential for health risks and/or damage to property. Transportation and handling of wind turbine components to or at the worksite is no small feat and requires considerable planning. Challenges and risks are specifi c to each location. In South Africa for instance, wind turbine installation sites are mainly located in coastal areas or in remote coastal hinterlands where the required wind conditions exist. Oft en, these sites are diﬃ cult to access and are far away from settlements or towns where emergency personnel and facilities are available. Th e hazards associated with the transport of wind turbine components include: (i) People and load falls: Unsecured or inappropriately secured loads that shift are diﬃ cult to un- load. Sending someone up onto the trailer to handle such loads puts them at risk of falling. (ii) Overturning vehicles: In serious cases of load shift , the vehicle can become unbalanced and overturn.

(iii) Collision with other vehicles: Oft en remote installation locations will require the use of minor THEME 3.1.1 roads and tracks for the transportation of wind turbine components. Due to the size of transport vehicles there will be occasions when they have to cross the centre of a road or even move along the wrong side of a roundabout, and this can put other road users at risk. (iv) Fatigue: Fatigue caused by driving long distances without an appropriate break can potentially result in sleep-related accidents.

OHS Risks associated with the Construction of Wind Turbines Construction is seen as the most complicated and possibly the most dangerous stage in a wind turbine’s life cycle, as it involves the installation of major components, among them the foundation and transition pieces and the assembly of the wind turbine. It includes most of the heavy lift ing of turbine components together with the completion of multiple tasks in quick succession, and this could present a number of safety issues. Examples of hazards encountered during construction phases include: (i) Falling structures, loads or objects during lift ing operations (ii) Falls from heights (iii) Mechanical hazards, such as contact with moving parts (iv) Ergonomic physiological eff ects as a result of heavy lift ing and repeated movements (v) Fatigue from climbing ladders or working in confi ned spaces (vi) Working with dangerous substances (vii) Time pressure (viii) Insuffi cient or lack of safety equipment (ix) Lack of competence or skills (x) Lack of communication between diff erent actors/companies involved in the operation (xi) Exposure to noise and vibration

223 Exercises 1. Explain the OHS risks associated with electrical work on wind turbines. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

THEME 3.1.1 ……………………………………………………………………………………… ……………………………………………………………………………………

2. Explain the OHS risks associated with chemical work on wind turbine components. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

3. Explain the OHS risks associated with the construction of wind turbines. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Further Information on the Resource CD

(i) Working in the wind safely, Guidelines on emergency arrangements including fi rst aid, Eu- ropean Wind Energy Association, 2013. (ii) HAZARD IDENTIFICATION CHECKLIST: OCCUPATIONAL SAFETY AND HEALTH (OSH) RISKS IN THE WIND ENERGY SECTOR, European Wind Energy Association, E-Fact 80, 2015.

224 THEME 3.1.2 SAFE WORK PRACTICES RELATED TO WIND TURBINE TECHNOLOGIES

Introduction

Every employer is legally required to take every measure that can be reasonably expected to avoid or limit all foreseeable hazards and risks to the safety and health of the employee. Employees are also expected to take appropriate measures with regards to fi rst aid for accidents, fi refi ghting and the evacuation of employees and other individuals on site and to maintain contact with the relevant external emergency

services. Following industry-specifi c best practices and guidelines will clearly provide a safer work envi- 3.1.2 THEME ronment. However, even if industry adheres to all specifi c best practices this does not relieve employees of their duty to ensure compliance with relevant safety guidelines and best practices. Th us, in this theme we will fi rst introduce you to a basic checklist for the prevention of accidents and damage to health in the wind energy sector and secondly, indicate some prevention and mitigation measures for selected hazards.

Please note:

In RET Level 2 we introduced you to relevant safe work practices: in Th eme 3.1.1, 3.1.2, 3.1.3 and 3.1.4 we oﬀ ered some generic information on OHS, while Th eme 3.1.5 dealt specifi cally with electrical safety. Please consider consulting these sections again, as their safety information applies to wind energy applications as well!

Keywords

Safety checklists Prevention and mitigation measures for selected hazards Working at height Electrical installations Lift ing operations Working in remote locations

Theme Outcomes

At the end of this theme, you should be able to: (i) Explain practicable steps to ensure the prevention of harm to employees working with wind turbine technologies. (ii) Explain how employees can be involved in health and safety processes and procedures.

Deﬁ nition of Terms Safety Checklists Th e best way to reduce accidents in the workplace is to be proactive in terms of prevention. Well-informed employees who have identifi ed and can control hazards and risks are important for every company. Safety checklists are a great way to determine compliance with industry specifi c standards and to ensure consistency. Many companies use checklists as documentary evidence that they have a system in place to identify and control hazards and risks. Under the exercises you will fi nd a checklist for the prevention of accidents and damage to health in the wind energy sector (small-scale installations only). Th is checklist can be used as initial documentary evidence for compliance with relevant standards in a work environment or in a training facility. Th e checklist aims to illustrate some specifi c health and safety aspects and work area arrangements associated with

225 the logistics, installation, maintenance and decommissioning of small-scale wind energy applications. Please note that the list is by no means exhaustive. More comprehensive information is available on the CD. Prevention and Mitigation Measures for Selected Hazards OHS hazards during the construction, operation, and decommissioning of wind turbines are generally similar to those of most industrial facilities and infrastructure projects. Th ey may include physical hazards, such as working at heights, working in confi ned spaces or working with rotating machinery and falling objects. We will focus primarily on hazard prevention related to working at heights, electrical installations, lift ing operations and working in remote locations. Working at Height Working at height occurs frequently throughout all phases of construction and operation and is espe-

THEME 3.1.2 THEME cially relevant when it comes to maintenance. Th e main focus when managing working at height should be the prevention of a fall. However, additional hazards that may also need to be considered include falling objects and adverse weather conditions (wind speed, extreme temperatures, humidity, and wet- ness). Managing working at height activities requires suitable planning and the allocation of suﬃ cient resources. Preferred mitigation methods may include: (i) Eliminating or reducing the necessity of working at height. During the planning and design phases of an installation, specifi c tasks should be assessed with the aim of removing the need to work at height, if practicable. Examples of this would include assembling structures and carrying out ancillary works at ground level, then lift ing the complete structure into position to the extent that is feasible and cost eﬀ ective. (ii) If working at height cannot be eliminated, use work equipment or other methods to prevent a fall from occurring. Collective protection systems, such as edge protection or guardrails, should be implemented before resorting to individual fall arrest equipment.

In addition to the above, the following points should be considered as methods of preventing incidents: (i) Ensure that all structures are designed and built to the appropriate standards. (ii) Wherever possible, suitable exclusion zones should be established and maintained underneath any activities that are carried out at height to protect workers from falling objects. (iii) Ensure that all employees working at height are trained and competent in doing so and that they are able to use the rescue systems that are in place. (iv) When working at height, all tools and equipment should be fi tted with a lanyard where possible, and capture netting should be used if practicable. (v) Avoid conducting tower/pole installation or maintenance work during poor weather conditions, especially if there is a risk of lightning strikes. (vi) An emergency rescue plan should be in place detailing the methods to be used to rescue workers.

FIGURE 1: FUSES AND SURGE PROTECTION FOR A SMALL-SCALE WIND TURBINE INSTALLATION (OFF-GRID)

Image source: S4GJ/GIZ.

226 Electrical Installations Wind turbine operations include working with electrical components such as generators, transformers, batteries and cables. Working with and around these electric components can be very dangerous, as these are capable of delivering high power to loads and thus potentially lethal electric shocks. Electrical work should therefore be carried out by qualifi ed and competent tradesmen only. However, as a general rule and before you start working with any electrical components, you must assume that all power lines are energised, unless you have confi rmed and ensured (lockout/tagout) that the power line has been de- energised. Beware that if you touch an energised power line or energised equipment, electric energy will attempt to travel through your body. When an electric current is conducted through your body, your body is in opposition (resistance) to that current, resulting in dissipation of energy, usually in the form of heat. Th is is the most basic eﬀ ect of electrical energy on living tissue, i.e. skin, muscles, organs etc. If you become part of an electric circuit, your tissue acts as a resistor and consequently the tissue heats up. If the current is

strong enough, which is almost always the case in wind turbine installations, the amount of heat gener- 3.1.2 THEME ated can be suffi cient to burn body tissue. A high current enters and leaves the body violently, causing burns or even blowing out an exit hole. Another eff ect of electric current on the body is electric shock (electrocution). Th is is perhaps the most signifi cant type of electrical hazard. If the strength of an electric current is suffi cient and is conducted through your body, its eff ect will overload your nervous system and prevent you from being able to ac- tuate your muscles appropriately. If you are triggered by an involuntary external current through your hands, your forearm muscles responsible for bending fi ngers contract, clenching your fi ngers into a fi st. You will be unable to let go of the live wire or conductor. Th us, stopping the current as quickly as possible is essential. However, even when the current has been stopped, victims may not regain voluntary control over their muscles for a while, as the nervous system is still in disarray. Th e muscle controlling the lungs and the heart can also be aff ected by the electric current, a condition known as fi brillation. A fi brillating heart fl utters rather than beats, and is ineff ective at pumping blood to vital organs in the body. Th e consequences of this can be fatal. Last but not least, we need to remind you about the danger of an arc fl ash, a short circuit explosion that fl ashes from one exposed live conductor to another or from an exposed live conductor to the ground. Th e ionised air in an arc fl ash creates very hot plasma that is electrically conductive. Oft en, the explosion lasts for only a fraction of a second but its temperatures can easily reach over 1000º C.

FIG U RE 2: LOCKOUT/TAGOUT PROCEDURES

Image source: http://www.shutterstock.com/pic-189125360/stock-photo-electrical-breaker-box-locked-out-for-service-inspec- tion-or-installation-lockout-tagout.html?src=Pg62903boBiVDso523piZw-1-1&ws=1

To prevent the DC and AC circuits from inadvertently re-energising during wind turbine installation or scheduled maintenance work, documented lockout/tagout procedures should be followed both on the DC and AC side of the system.

227 Managing electrical installation work requires suitable planning and the allocation of suﬃ cient resources. One preferred mitigation method is the lockout/tagout procedure: (i) Th e circuit or equipment must fi rst be de-energised. (ii) Every person working on the circuit or equipment must verify that the system is de-energised prior to starting work. (iii) Every person working on the system must employ his/her own lock to isolate the energy. (iv) Th e locked system must be properly identifi ed with tags to indicate that the system must not be tampered with. (v) As each person completes his/her task, they remove their padlock and tag. (vi) Before re-energising the system, all covers and panels must be securely reattached. (vii) A system cannot be re-energised until the fi nal lock is removed. (viii) People who perform lockout/tagout must be trained. (ix) Employees who work around locked and tagged equipment must be trained on the hazards of

THEME 3.1.2 THEME electricity and the importance of leaving the locks and tags intact. Lifting Operations Lift ing operations are oft en an integral component of the construction of any wind energy facility. Dur- ing the construction phase, components are typically assembled and transported to the site where assembly will take place. Th is involves using lift ing equipment to lift loads of varying dimensions and weights numerous times. Th e management of lift ing operations requires the use of competent personnel, thorough planning, eﬀ ective communication, and a high level of supervision when carrying out a lift . Consideration should be given to the following: (i) Ensure all relevant information is known about the load, e.g. the size, weight, method of slinging and attachment points. (ii) Ensure all lift ing equipment is suitable, capable of supporting the load, is in good condition, and in receipt of any statutory inspections required. (iii) Ensure all supervisors, equipment operators and slingers are trained and competent in the operation of lift ing equipment and intended lift ing techniques. (iv) Exclusion zones are to be established and maintained in order to prevent any unauthorised access to lift ing areas. (v) When lift ing large loads, ensure weather conditions are favourable for the task. Working in Remote Locations When operating in remote locations far away from hospitals or other emergency facilities, planning is vital in ensuring the safety of employees. Points to consider when planning to work in remote areas: (i) Suitability of communication equipment available for the work crew. (ii) Th e training and competence of personnel working remotely and the readiness of all necessary safety equipment at the location. (iii) Means for managers to track the exact location of the working crew. (iv) Local emergency plan in place. (v) Provision of suitably qualifi ed fi rst-aid-trained personnel in the work crew.

Exercises

1. Sample Hazard Identi cation Checklist Make use of the following checklist and answer the questions, for example: (i) Does the hazard exist at the workplace? (ii) Are the hazards controlled to minimise negative infl uences on safety and health of all workers? Answering ‘NO’ or ‘Don’t know’ to one of the following questions indicates a need for improvements to be made in the workplace. ‘YES’ = Satisfactory ‘NO’ or ‘Don’t know’ = Unsatisfactory = Urgent attention needed!

228 Don’t Questions YES NO know Has a competent safety coordinator been appointed to coordinate and oversee safety actions and to update disseminated safety information? Do supervisors/foremen provide leadership in addressing and promoting OHS? Is access to the work site controlled and are appropriate levels of supervision in place? Are there written emergency procedures and plans in place that consider major incidents, i.e. how the rescue of workers will be undertaken or how the co-ordination with the emergency services will work?

Have an appropriate number of first aiders been appointed? 3.1.2 THEME Are there sufficient first aid kits available? Is an accident reporting system in place? Are site-specific and task-specific risk assessments being carried-out? Are all workers aware of these risk management mechanisms and procedures? Is the use of sub-contractors appropriately managed? Is there a system that identifies all hazardous substances? Is exposure to chemicals and dust eliminated or, if not possible, reduced to a minimum? Is work arranged so that manual handling operations such as lifting and carrying or repetitive manual handling of even light items, are avoided, and where not possible, reduced to a minimum? Have the frequency and methods of communication between all parties involved in the wind turbine project been considered and agreed on? Do all workers know when work will cease due to difficult weather conditions? Has working at height been considered in an appropriate risk assessment? Can working at heights activities be eliminated or reduced? Are all fall prevention provisions and fall arrest equipment suitable and sufficient and are they regularly inspected? Are workers appropriately trained to use these? Are all lifting operations subjected to a full risk assessment? Are workers involved in lifting operations appropriately trained? Is lifting equipment regularly inspected and suitable for the specific task? Have all operational and maintenance activities been risk assessed? Is there a safe system of work procedures in place to manage work activities on or near live electrical systems? Is there a permit to work procedures in place for electrical work? Is the electrical work carried out by qualified and competent tradesmen? Are effective safety measures and procedures for electrical isolation and grounding in place? Has the fault level of the generator, transformer and cable layout been appropriately calculated and are adequate circuit breakers installed? Are wind turbines and their associated hardware compatible with the relevant network operator’s distribution code and safety rules?

229 Are all electrical tools/equipment approved for work? Are workers provided with suitable PPE? Is appropriate fault protection in place to selectively disconnect faulty components? Are suitable ﬁre extinguishers regularly checked and appropriately located, and are workers trained to use them?

2. Best Practices for Avoiding Electrical Injury Following a list of best practices can protect employees from electrical injury. Score your experience on each item based on your workshop practice, by using the following guidelines: 3 = We/I do this consistently and purposefully 2 = We/I do this sometimes, but not always - must be more consistent

THEME 3.1.2 THEME 1 = We/I really must improve on this item

Item 3 2 1 We never assume a power source is de-energised unless checked personally. We use tools and equipment only for their designed purpose. We have an emergency response plan for electrical emergencies. We periodically practice the emergency response plan for electrical emergencies. We use lockout/tagout procedures. We keep electrical enclosure doors closed and locked. We discard tools and cords that are frayed or damaged. We ground all electrical equipment. We avoid using tools with missing ground prongs. We maintain required clearances from all power lines when working at a turbine construction site. We contact utilities to locate buried power line locations. We identify safe routes where cranes and other equipment must travel.

Do you reach a score of 36?

Further Information on the Resource CD

(i) Occupational safety and health in the wind energy sector, European Wind Energy Associa- tion, 2013. (ii) Safety and Health in Wind Energy, University of Wisconsin Oshkosh, 2011.

230 THEME 1.1.1 Unit 3.2

UNIT 3.2 HAZARDS AND SAFE WORK PRACTICES RELATED TO FUEL CELL TECHNOLOGIES

Introduction

Th is unit is an introduction to the hazards associated with fuel cells and the fuels that they use. It also gives simple straightforward advice on safe work practices, aiming to minimise and control the potential risks emerging from this rapidly developing technology. We also aim to make you more aware of your responsibility to prevent an incident that could jeopardise the acceptance of these new technologies. Fuel cell vehicles (FCVs) consist mainly of three principal subsystems: the fuel cell stack, a battery and electrical propulsion. We will now deal with the latter two subsystems in Unit 3.2 (e-mobility).

Unit Outcomes

At the end of this unit, you should be able to: (i) Explain workplace hazards related to fuel cell technologies. (ii) Explain practicable steps to ensure the prevention of harm to employees working with fuel cell technologies. (iii) Explain how employees can be involved in health and safety processes and procedures.

Themes in this Unit

Unit 3.2 covers the following two themes: Th eme 3.2.1 Hazards related to Fuel Cell Technologies Th eme 3.2.2 Safe Work Practices related to Fuel Cell Technologies

231 THEME 3.2.1 HAZARDS RELATED TO FUEL CELL TECHNOLOGIES

Introduction

Th e major hazards associated with fuel cell technologies may be divided into the following categories: (i) working with dangerous substances including fi re and explosions, (ii) electric shock, and (iii) general safety hazards, for example manual handling. As indicated in Topic 2, diﬀ erent types of fuel cells have been developed. Th e potential hazards a fuel cell presents are heavily dependent on the nature of the fuel and electrolyte it uses. Our focus in this theme is on polymer electrolyte membrane (PEM) fuel cells (PEMFC) only, and regarding dangerous substances, fi re and explosions, we will mainly focus on hydro-

THEME 3.2.1 THEME gen- related hazards.

Keywords

How PEM fuel cells work Fuels: Fire and explosion hazards Hydrogen properties and related hazards Fuel cells and electric hazards

Theme Outcomes

At the end of this theme, you should be able to explain workplace hazards related to fuel cell technologies.

Deﬁ nition of Terms Brief Review: How PEM Fuel Cells Work To better understand the potential hazards PEMFC present, we will briefl y review their basic modes of operation. A fuel cell is a device that harnesses the energy liberated when hydrogen, or a hydrogen-rich fuel, reacts with oxygen to produce water. Normally, when hydrogen and oxygen react in an uncontrolled environment, a hot fl ame and heat energy is released. In the controlled environment of a fuel cell, a fl ame is not produced, but the reaction produces electrical energy and a certain amount of heat. Like a battery, a fuel cell is an electrochemical device where an electric current is produced as a result of chemical reactions that take place at the electrodes. A battery, however, stores electric energy in the form of chemical energy and needs regular recharging or replacement, while a fuel cell continues producing electric energy as long as it is supplied with fuel. A single PEM fuel cell consists of an electrolyte membrane sandwiched between two thin porous electrodes, the anode and the cathode. Th e anode of the cell is coated with special catalysts which assist in splitting each hydrogen molecule into two protons (H+ ions) and two negatively charged electrons. Th e electrons leave the anode and travel to the cathode, providing an electric current in the external circuit. Oxygen, usually from air, is fed to the cathode of the cell where it reacts with hydrogen protons and the electrons returning from the external circuit, to produce water. Fuels: Fire and Explosion Hazards All fuels suitable for use in fuel cells can potentially catch fi re and so present a signifi cant fi re and explosion hazard. Fuels are thus called “dangerous substances” and regulations are in place that include avoiding sources of ignition and the release of dangerous substances into the workplace. All types of fuels, such as hydrogen, petrol, methane, LPG etc. can easily catch fi re and may produce an explosion. However, before an explosion can occur, a fl ammable mixture of the fuel and air must form and a source of ignition must be present to ignite it. Petrol and methane are fuels routinely used by millions of people every day. Most users are aware of the properties of these fuels and what needs to be done to handle them safely. Th e properties and risks of hydrogen are oft en not so widely known and this can result in the risk of not being properly controlled. Th e

232 hazards of hydrogen are thus discussed in some detail below, followed by a brief summary of diﬀ erent or additional hazards of other fuels. Hydrogen Properties and Related Hazards Hydrogen is a very fl ammable gas and can cause fi res and explosions if it is not handled properly. Hy- drogen is a colourless, odourless, and tasteless gas. It is thus very diﬃ cult to detect a hydrogen leak with our human senses and by the time it is detected, hydrogen concentrations might have already exceeded its lower fl ammability limit. Hydrogen has some unusual properties, and if these are not known or no appropriate measures were taken, then the likelihood of hydrogen escaping and a fi re or explosion occurring may be greater than with many other fuels. Some of the most important properties of hydrogen that make it so volatile are: (i) Very wide fl ammability range (ii) Very low ignition energy required

(iii) Possibility of detonation 3.2.1 THEME (iv) Low viscosity (v) High diﬀ usivity (vi) Much lighter than air

In the event that hydrogen catches fi re, it burns with a fl ame that is almost invisible and readily forms an explosive mixture with air. Th e range of hydrogen/air concentrations that can explode is extremely wide, much wider than almost any other fuel. Mixtures containing as little as 4% hydrogen, which is the lower explosion limit (LEL), up to as much as 75%, the upper explosion limit (UEL), will readily ignite and explode. If a fl ammable mixture of hydrogen and air is allowed to form, the likelihood of an explosion occurring is very high, because the energy necessary to initiate a hydrogen/air mixture is very small. Hydrogen gas has a very low viscosity and it is thus very diffi cult to prevent hydrogen systems from developing leaks. Pipework that was leak tight when pressure tested with nitrogen will oft en be found to leak profusely when used on hydrogen duty. Th is property increases the likelihood of a fl ammable mixture forming. On the other hand, hydrogen is much lighter than air and is also very diff usive. When it escapes it moves upwards very rapidly. If a leak occurs in an open or well-ventilated area, its diff usivity and buoyancy reduces the likelihood of a fl ammable mixture forming in the vicinity of the leak. Almost all hydrogen is currently stored in high-pressure cylinders. Cryogenic storage of liquid hydrogen for fuel cell use may however become more widespread in the future. Hazards resulting from the very low storage temperatures used for liquid hydrogen, around -250º C, include severe cold-burns and the condensation of oxygen enriched liquid air on unprotected pipework. At atmospheric pressure, liquid hydrogen boils at -253º C and should hydrogen leak from cryogenic storage, it will be very cold and thus heavier than air. As a result, leaking gas oft en sinks initially, forming a fl ammable atmosphere at low level before warming up, becoming buoyant and rising. Th is is in marked contrast to a leak of compressed hydrogen, where the accumulation of a fl ammable concentration of hydrogen is always at high level.

FIGURE 1: BASIC STRUCTURE OF A HYDROGEN SAFETY SYSTEM Figure 1: Basic structure of a hydrogen safety system

Prevention measures

Leak

Leak detection

Safety measures

Incidents Ignition

Risk assessment Risk Evaporation Flame detection

Safety vents and barriers

Damage minimisation measures

Image: S4GJ/GIZ

233 Fuel Cells and Electric Hazards As indicated in earlier sections, electric shock can be a life-threatening hazard and must not be over- looked in the design, operation and maintenance of fuel cells and its associated equipment. Electrical hazards usually arise from two distinct areas within fuel cell installations: the normal single- and/or three-phase AC supply into the system and the high current DC power output of the fuel cell stack. With larger units there may be a third area - the AC output of an inverter connected to the fuel cell stack. Potential and current produced by each cell element in the stack is usually quite small. However, even relatively small stacks could generate an output that may provide large electrical currents, which can be life threatening. Large fuel cell stacks, as those found in FCVs or containerised units (prime power or UPS), certainly provide large and potentially lethal currents. Safety Issues of Hydrogen in Vehicles We have now outlined generic hydrogen hazards related to its properties. While these generic hazards

THEME 3.2.1 THEME certainly apply to FCVs as well, hydrogen on board a FCV may pose specifi c safety hazards. Th e hazards related to FCVs should be considered in situations where the vehicle is inoperable, when the vehicle is in normal operation and in collisions. Hydrogen as a source of fi re or explosion may arise from the fuel storage tanks, from the fuel supply lines or from the fuel cell stack. Th e stack itself poses the lowest risk, although in a fuel cell, hydrogen and oxygen are only separated by a very thin polymer membrane. In case of a membrane rupture hydrogen and oxygen would combine, but here the fuel cell would lose its potential which should be easily detected by a control system. In that case the supply lines need to be immediately disconnected. Th e fuel cell operating temperature in PEMFCs is relatively low (60° to 90°C). However hydrogen and oxygen may combine on the catalyst surface and create ignition conditions. Th e potential damage would however be limited due to the small amount of hydrogen present.

In a FCV, the largest amount of hydrogen is present in the tanks. Several tank failure modes could be considered in both normal operation and collision, such as: (i) Catastrophic tank rupture due to manufacturing defects or caused by abusive handling of the tank, stress fracture, and puncture by a sharp object or even external fi re combined with failure of pressure relief valves. (ii) Massive leaks due to faulty pressure relief valves or induced faults in the tank wall, or puncture by a sharp object. (iii) Low leak due to stress cracks in the tank liner, faulty pressure relief valves, faulty coupling from tank to the feed line, or impact-induced openings in the fuel line connection.

FIG U RE 2: A FUEL CELL POWERED BUS MANUFACTURED BY TOYOTA (JAPAN)

Image source / Photo courtesy of Wikimedia: https://en.wikipedia.org/wiki/Fuel_cell#/media/File:TOYOTA_FCHV_Bus.jpg

234 Several studies conducted on behalf of various automobile companies performed detailed assessments of probabilities of these failure modes. Th e overall conclusion of these studies indicates that most failure modes are highly unlikely. Th e greatest potential risk appears to be a slow leak in an enclosed home or public garage, where an accumulation of hydrogen could lead to a fi re or an explosion if no hydrogen detection or risk mitigation devices or measures such as passive or active ventilation are applied. Avoidance or minimisation of failure will be outlined in the next theme. Lastly, various testing of FCVs, hydrogen vehicle fuelling and maintenance stations by national and international agencies such as the Society of Automotive Engineers (SAE), resulted in guidelines and standards for FCV testing, e.g. Recommended Practice for Electric Fuel Cell and Hybrid Electric Vehicle Crash Integrity Testing (SAE J-1766, 2014).

FI G U R E 3: HYDROGEN TANKS ON THE HONDA FCX CLARITY PLATFORM THEME 3.2.1 THEME

Image source / Photo courtesy of Wikimedia: https://en.wikipedia.org/wiki/Hydrogen_tank#/media/File:Honda_FCX_plat- form_rear_Honda_Collection_Hall.jpg

Your own notes

235 Exercises 1. List the most important properties of hydrogen. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

THEME 3.2.1 THEME ……………………………………………………………………………………… ……………………………………………………………………………………

2. Explain the hazards related to the properties of hydrogen. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Further Information on the Resource CD

(i) Safety issues of hydrogen in vehicles, Frano Barbir, Energy Partners (PDF). (ii) Safety Planning for Hydrogen and Fuel Cell Projects, UNITED STATES DEPARTMENT OF ENERGY, 2016..

236 THEME 3.2.2 SAFE WORK PRACTICES RELATED TO FUEL CELL TECHNOLOGIES

Introduction

In this theme, we will give you some basic advice on safe work practices with PEM fuel cells and FCVs, aiming to minimise and control potential risks. We trust that this guidance makes you more aware of your responsibility to prevent any incidents in relation to this technology. THEME 3.2.2 Keywords

Non-FCV safe work practices Hydrogen safety checklist Th e Hindenburg disaster FCV safe work and application practices

Theme Outcomes

At the end of this theme, you should be able to: (i) Explain practicable steps to ensure the prevention of harm to employees working with fuel cell technologies. (ii) Explain how employees can be involved in health and safety processes and procedures.

Deﬁ nition of Terms Non-FCV Safe Work Practices Hydrogen safety for containerised fuel cell units (prime power or UPS) or under lab conditions, much like all fl ammable gas safety, relies on fi ve key considerations: (i) Recognise hazards and defi ne mitigation measures (ii) Ensure system integrity, i.e. keep the hydrogen in the system (iii) Provide proper ventilation to prevent accumulation, i.e. manage discharge (iv) Ensure that leaks are detected and isolated/mitigated (v) Train personnel, ensuring that hazards and mitigations are understood and that established work instructions are followed, i.e. manage operations Hydrogen Safety Checklist For both new and experienced hydrogen users, safety checklists identify considerations necessary to ensure safe use and installation of hydrogen fuel. Th e following checklist is rather generic and applies to all types of hydrogen systems. However, the checklist is organised using the above-mentioned key considerations. Examples are included to help in identifying specifi c prevention measures. Please note that the checklist is kept very basic, as it is not possible in our context to include more variables.

237 Key considerations Actions Hazard recognition and mitigation Identify risks related to hydrogen properties (ﬂammability, ignition etc.). Follow applicable codes and standards.

Identify potential hazards from adjacent facilities and nearby activities.

Address common failures of components such as ﬁtting leaks, valve failures, control hardware and software failures, and power outages.

Hazard isolation Store hydrogen outdoors. Ventilate indoors.

Provide horizontal separation to prevent spreading hazards to/from other systems’ structures and THEME 3.2.2 combustible materials.

Consider worst-case scenarios Design and select only compatible equipment capable of maximum credible pressure.

Provide relief devices that safely vent hydrogen to prevent overpressure conditions.

Perform system pressure tests to verify integrity after initial construction, maintenance, bottle replacements etc.

Protect system Mount hydrogen cylinders. Install automatic shut-off. Demobilise supply vehicles before delivery. Protect system against accidental impact and vandalism. Use warning signs. Size storage appropriately.

Manage discharge Discharge hydrogen outdoors or into a laboratory ventilation system that assures proper dilution to avoid build-up of hydrogen under ceilings/roofs and other partly enclosed spaces.

Detect and mitigate Provide automatic leak detection and shutdown/ isolation. Provide alarms for actions. Detect and mitigate sensor or process control faults.

Appropriate ﬁre protection with extinguishers, sprinklers, etc.

Manage operations Establish safe operating- and emergency procedures, and preventive maintenance schedules including lockout/tagout etc.

Train personnel regularly for safe work practices. Monitor incidents, near misses, compliance etc.

The Hindenburg Airship Disaster Despite the volatility of a gas like hydrogen, which combusts far more easily compared to other vehicle fuels, hydrogen FCVs are considered to be as safe as other types of cars with internal combustion engines or EV types. Hydrogen FCVs are however burdened with a somewhat unfortunate reputation, courtesy of Germany's infamous LZ 129 Hindenburg, the hydrogen-fi lled airship (zeppelin) that exploded over Lakehurst, New Jersey in 1937. Th e airship was fi lled with hydrogen for buoyancy and the theory that a hydrogen leak was ignited by a static spark is the most widely accepted crash hypothesis. Th e cause of ignition and the fi re’s initial fuel however, is still unclear and various hypotheses ranging from sabotage, static spark, lightning, engine failure etc. are still making the rounds.

238 FIGURE 1: THE HINDENBURG ZEPPELIN DISASTER IN 1937 THEME 3.2.2

Image source / Photo courtesy of Wikimedia: https://upload.wikimedia.org/wikipedia/commons/1/1c/Hindenburg_disaster.jpg

FIG U RE 2: A MODERN HYDROGEN-POWERED AIRCRAFT

Image source / Photo courtesy of Wikimedia: https://en.wikipedia.org/wiki/Hydrogen_vehicle#/media/File:Boeing_Fuel_Cell_ Demonstrator_AB1.JPG - Th e Boeing fuel-cell demonstrator (Diamond HK36 Super Dimona EC-003) on display at the 2008 Farnborough Airshow

FCV Safe Work and Application Practices All safety-engineered hydrogen FCVs, such as the Toyota Mirai, the Hyundai ix35 FCEV and the Honda FCX Clarity, can be considered to be as safe as any other modern types of cars, be it with conventional internal combustion engines or other EV types. Potentially dangerous failure of FCVs in relation to hydrogen storage tanks have been outlined in the previous theme. Avoidance or minimisation of these failures includes: (i) Leak prevention through proper system design, selection of adequate equipment and testing standards, allowing for tolerance of shocks and vibrations, locating pressure-relief devices, protecting the high-pressure lines etc. (ii) Automated leak detection (iii) Ignition prevention through automatic elimination of all sources of electric sparks (disconnecting the battery bank etc.); by designing the fuel supply lines so that they are physically separated from all electrical devices as far as possible; by including both active and passive ventilation

239 Lastly, there are fairly comprehensive codes and standards promulgated that address FCV fuelling and on-board vehicle safety. Th ese codes and standards include, inter alia, the SAE series of documents such as: Recommended Practice for General Fuel Cell Vehicle Safety (SAE J2578), Fuel Cell Systems in Fuel Cell and other Hydrogen Technologies (SAE J2579), Compressed Hydrogen Surface Vehicle Refuelling Connection Devices (4SAE J2600 and SAE J2601.6).

FI G U R E 3: A MODERN HYDROGEN-POWERED SUV THEME 3.2.2

Image source / Photo courtesy of Wikimedia: https://en.wikipedia.org/wiki/Hydrogen_vehicle#/media/File:Hyundai_ix35_fuel_ cell._Spielvogel.JPG

Your own notes

240 Exercises 1. List and explain some key considerations to ensure hydrogen safety for containerised fuel cell units (prime power or UPS) or when working with hydrogen under lab conditions. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… THEME 3.2.2 ……………………………………………………………………………………… ……………………………………………………………………………………

2. List and explain some considerations to ensure hydrogen safety for FCVs. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Further Information on the Resource CD

(i) Safety issues of hydrogen in vehicles, Frano Barbir, Energy Partners (PDF). (ii) Safety Planning for Hydrogen and Fuel Cell Projects, UNITED STATES DEPARTMENT OF ENERGY, 2016..

241 THEME 1.1.1 Unit 3.3

UNIT 3.3 HAZARDS AND SAFE WORK PRACTICES RELATED TO E-MOBILITY TECHNOLOGIES

Introduction

As indicated in earlier themes, the major diﬀ erence between electric vehicles (EVs) and conventional combustion-powered vehicles can be found in the three subsystems of EVs: the battery bank (storage and supply), the electrical propulsion system (electric motor and transmission) and their electronic control systems. Regarding hazards and safe work practices, this unit will only focus on the fi rst two subsystems and particularly on high peak currents.

Unit Outcomes

At the end of this unit, you should be able to: (i) Explain workplace hazards related to e-mobility technologies. (ii) Explain practicable steps to ensure the prevention of harm to employees related to e-mobility technologies. (iii) Explain how employees can be involved in health and safety processes and procedures.

Themes in this Unit

Unit 3.1 covers the following two themes: Th eme 3.3.1 Hazards related to E-Mobility Technologies Th eme 3.3.2 Safe Work Practices related to E-Mobility Technologies

242 THEME 3.3.1 HAZARDS RELATED TO E-MOBILITY TECHNOLOGIES

Introduction

Electric vehicles (EVs) represent a diﬀ erent technology compared to conventional vehicles that are powered by internal combustion engines. Th is means that new safety hazards, mainly related to the characteristics of high current energy storage systems and electric powered motors, may be present. While a safety engineered EV can be considered to be as safe as any other modern conventional vehicle, the EV’s unique two subsystems, i.e. the battery bank (storage and supply) and the electrical propulsion system (electric motor and transmission) do present some potential hazards. In this theme we will thus deal with the general electric safety issues in EVs. THEME 3.3.1

Please note:

We already dealt with electric safety in RET Level 2, particularly in Th eme 3.1.5 and in earlier sections of this textbook. Please consider consulting these sections again as they apply to EV components and systems as well!

Keywords

Battery safety hazards Electrical hazards Chemical hazards Cumulative chemical and electrical eﬀ ects

Theme Outcomes

At the end of this theme, you should be able to explain workplace hazards related to e-mobility technologies.

Deﬁ nition of Terms Brief Review: Dangers Involved in Working with High Peak Current Systems As indicated in earlier sections of this textbook all your muscle reactions, conscious ones like moving your body or subconscious ones like your heartbeat, are controlled by electrical (neutral) stimulation. Th ese stimulations are conducted inside your body through nerve pathways in a similar way to currents in electrical circuits. If you come into contact with live electric components, current can fl ow through your body. Even low direct currents (DC) above approximately 30 mA can potentially cause temporary heart pulse disturbances. If higher currents enter your body, serious external and/or internal burns can occur and in some cases dangerous ventricular heart fi brillation can result. If components of an electrical system are short-circuited the risk of arcing (arc fl ash explosion) appears. Th is can cause serious external burns on your body, particularly to your eyes.

243 FIGURE 1: EV WARNING DECALS

WARNING: HIGH VOLTAGE VEHICLE TO REDUCE THE RISK OF POSSIBLE SERIOUS INJURY (SHOCK OR BURN) OR DEATH:

THEME 3.3.1 COMPONENTS MARKED WITH THE HIGH VOLTAGE SYMBOL CONTAIN HIGH VOLTAGE AND HIGH TEMPERATURES AND SHOULD BE AVOIDED, SERVICE MUST BE PERFORMED BY QUALIFIED PERSONNEL ONLY. AVERTISSEMENT: CIRCUITS HAUTE TENSION DU VÉHICULE POUR RÉDUIRE LES RISQUES DE BLESSURES GRAVES (CHOCS OU BRULURES) OU MORTELLES: LES ÉLÉMENTS ACCOMPAGNÉS DU SYMBOLE HAUTE TENSION ONT UNE TENSION ET DES TEMPÉRATURES ÉLEVÉES ET DOIVENT ÈTRE ÉVITÉS. LA RÉPARATION ET L‘ENTRETIEN DOIVENT ÉTRE EFFECTUÉS PAR UN TECHNICIEN QUALIFIÉ SEULEMENT.

Image source: S4GJ/GIZ EV warning decals are usually located on or next to high ‘voltage’ components.

Battery Safety Hazards As discussed in previous sections, electrifi cation is the most viable way to achieve clean and effi cient transportation that is crucial for sustainable and global development. In the near future, electric vehicles (EVs) including HEVs, PHEVs, FCVs and BEVs will dominate the clean vehicle market. Key EV components are powerful battery systems designed to provide suffi cient electric power for traction. Due to their purpose (traction) these traction batteries are very diff erent compared to the ordinary rechargeable 12 V lead–acid batteries in conventional vehicles with internal combustion. Th e latter ones, so-called SLI batteries, are mainly required for starting, lighting, and ignition. Traction batteries on the other hand are required to power the propulsion systems of EVs. Traction batteries are thus designed to have a high capacity. Please note that Ah or Wh (or kWh) capacity is used to represent a battery’s capacity, while Wh/kg is used to represent specifi c energy, also called gravimetric energy density, to defi ne how much energy a battery can store per unit mass. Th ese traction batteries need to be rechargeable and thus various lithium-ion battery cathode and anode materials are available. With diff erent EV sizes, their associated battery systems diff er as well. PHEVs, for example Toyota’s Prius, are furnished with relatively small batteries, i.e. less than 10kWh. Subcompact EVs are usually equipped with 12 – 18 kWh capacity, mid-sized family sedans may have 20 – 40 kWh capacity, and luxury models are boasting 60 – 90 kWh to provide extended driving range and high performance. Th us, the amount of power EVs require for their propulsion is realised by battery-powered high ‘voltage’ systems. EVs with high ‘voltage’ systems have components that work with voltages above 60 VDC or above 25 VAC. In fact, some luxury high performance EVs, such as Tesla’s S Model, require very high levels of electrical power, i.e. direct currents between 400 V and 650 V and very high peak currents. Considering all of these facts, we can understand that these high ‘voltage’ components, apart from on board electrical energy storage (battery), also high ‘voltage’ cables, protective relays and electric loads (e.g. motors), represent not only potential electric hazards, but also mechanical and chemical hazards.

244 FIG U RE 2: HIGH ‘VOLTAGE’ COMPONENTS OF A TYPICAL BEV Figure 2: (HighSCHEMATIC „voltage“ components) of a typical BEV (schematic)

Front drive unit A/C compressor High voltage cabling (if equipped) Battery coolant heater Rapid splitter

Charger THEME 3.3.1

DC-DC converter High voltage battery Front junction box Cabin heater Charge port Rear drive unit

Image source: S4GJ/GIZ

Electrical Hazards Current fl ow through the battery and all conductive material creates heat. Th us, the heat generated by an electric current during charge/discharge processes needs to be managed by electronic thermal management systems. Th e battery also has to be protected against high electrical currents and short circuits created by internal, external or by mechanical damage. Depending on the battery design, the heat created by these high currents may exceed the global battery cooling effi ciency or create a local hot spot. Lastly, the state of charge of the battery needs to be controlled. Overcharge and over discharge generates unwanted reactions which could accelerate temperature increases in the battery. In addition, overcharge creates more chemical instability of some battery materials. Th is is the reason why electronic protection devices, generally based on potential thresholds, are required for lithium-ion batteries. Chemical Hazards Th e substances contained inside the battery may present some chemical risks. Even though the lithium- ion battery will most probably not release any substances during normal conditions of use, a case of accidental exposure has to be considered, in particular the possibility of rupture of the casing due to mechanical damages or internal pressure. In this case, the following hazards can be observed: (i) Spillage: Hazards linked to the corrosive and fl ammable properties of the electrolyte (ii) Gas emission: Hazards linked to the fl ammable properties of volatile organic substances Cumulative Chemical and Electrical Effects In the case of on-board energy storage systems there is a potential cumulative eff ect of chemical and electrical hazards. In some specifi c circumstances it leads to so-called ‘thermal runaway’ conditions, for example, in case of a short circuit, heat accumulation will increase the cell temperature to the point where the organic solvent leaves the cell via the vent. At this time, any hot spot may induce a fi re. Th us, the possible consequences of cumulative chemical and electrical eff ects are: (i) Fire (ii) Toxic or harmful gas emissions: carbon monoxide (CO), organic electrolytes etc. (iii) Ejection of parts

245 Exercises 1. Explain electrical, chemical and cumulative hazards related to EVs! …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

THEME 3.3.1 ……………………………………………………………………………………… ……………………………………………………………………………………

Further Information on the Resource CD

(i) Electric Vehicle Safe Design Checklist, Electrical Safety Working Group (ESWG), 2014. (ii) INFORMATION FOR FIRST AND SECOND RESPONDERS RESCUE AND TRAINING MANUAL, HIGH VOLTAGE (HV) LITHIUM-ION BATTERIES, CTIF, 2014.

246 THEME 3.3.2 SAFE WORK PRACTICES RELATED TO E-MOBILITY TECHNOLOGIES

Introduction

Th roughout EV development and life cycle, care must be taken to minimise potential risks for all who come into contact with these new technologies including developers, assembly line workers, service technicians, vehicle occupants and fi rst responders. In this theme we thus describe some basic on-board safety systems of EVs, focussing on vehicle service and operation. THEME 3.3.2

Keywords

Recognising EVs and their safety hazards Servicing EVs safely Service tasks on EVs

Theme Outcomes

At the end of this theme, you should be able to: (i) Explain practicable steps to ensure the prevention of harm to employees related to e-mobility technologies. (ii) Explain how employees can be involved in health and safety processes and procedures.

Defi nition of Terms Recognising EVs and their Safety Hazards Th e main dangers in EV service and operation appear to be electrocution and the possibility of the car turning on accidentally while work is being performed. Th ese serious risks make safety training a priority. Most EVs are easily recognisable, but some models are not necessarily distinguishable from their internal combustion counterparts. In addition, some EV models, Hyundai’s Ioniq for example, come with three diff erent powertrains: HEV, PHEV and BEV. A mix-up could create serious problems for workers who are not able to tell the diff erence. To address safety concerns, most car manufacturers have developed certain indicators that can help workers identify the specifi c type vehicle model. In addition, colour coded high voltage cables in EVs warn of their potential danger. Usually these are orange but some models have blue cables instead. Servicing EVs Safely Ideally, workers should avoid contact with ‘high-voltage’ cables and components, unless the high-voltage battery has been disconnected. Many EV manufacturers have installed a safety switch or mechanism to disconnect the battery from the vehicle’s electrical system. Th e location of this will depend on the model. If working on a live electrical system cannot be avoided, proper personal protective equipment (PPE), including heavy rubber Class 0 rated gloves are required. Ordinary latex or neoprene gloves are not suffi cient enough to protect against a high ‘voltage’ shock. Even the Class 0 gloves need to be inspected to make sure they do not have any pin holes or cracks that would potentially allow direct contact between skins and live electric components. Other precautions include: (i) Turning the ignition OFF and making sure that the key or key fob is away from the vehicle before it is serviced or repaired. (ii) Ensuring the READY light is not on. (iii) Waiting 15 minutes before working on the vehicle aft er the battery has been disconnected.

247 FIGURE 1: LITHIUM-ION BATTERY PACK OF AN EV THEME 3.3.2

Image source / Photo courtesy of Wikimedia: https://commons.wikimedia.org/wiki/File:Nissan_Leaf_012.JPG A lithium-ion battery pack of an EV with colour-coded high ‘voltage’ cables.

Service Tasks on EVs Th e following generic service tasks indicate the type of work which might need to be performed during a service of an EV:

Battery System: (i) Perform high voltage disconnect procedures. (ii) Select, test and use proper safety gloves. (iii) Select, qualify and use proper electrical testing equipment and leads. (iv) Retrieve and detect diagnostic trouble codes (DTCs), determine repairs. (v) Diagnose problems caused by damaged or failed harnesses, connectors, terminals and fuses. (vi) Diagnose high voltage battery pack malfunctions. (vii) Remove and reinstall high voltage battery pack. (viii) Test, diagnose and repair high voltage leaks/loss of isolation. (ix) Test, diagnose and repair high voltage battery pack heating and cooling systems. (x) Test, diagnose, repair or replace high voltage battery pack internal components. (xi) Test and diagnose charging problems when using EV supply equipment. (xii) Reconnect/enable high voltage system.

Drive System: (i) Perform high voltage disconnect procedures. (ii) Select, test and use proper safety gloves. (iii) Select, qualify and use proper electrical testing equipment and leads. (iv) Retrieve and detect diagnostic trouble codes (DTCs), determine repairs. (v) Diagnose problems caused by damaged or failed harnesses, connectors, terminals and fuses. (vi) Remove and install rotor from stator. (vii) Diagnose motor-rotor position sensor (resolver or encoder type). (viii) Diagnose drive/traction motor-generator assembly for improper operation, such as an inopera- tive condition, noise, shudder, overheating, etc. (ix) Diagnose improper electrically actuated parking pawl operation, determine repairs. (x) Identify transmission fl uid and coolant fl uid requirements, verify fl uid levels.

Power electronics/controllers: (i) Perform high voltage disconnect procedures. (ii) Select, test and use proper safety gloves. (iii) Select, qualify and use proper electrical testing equipment and leads. (iv) Retrieve and detect diagnostic trouble codes (DTCs), determine repairs.

248 (v) Diagnose problems caused by damaged or failed harnesses, connectors, terminals and fuses. (vi) Identify procedures necessary to establish the proper vehicle operational power mode during service (OFF, ACCESSORY, POWER ON, READY TO DRIVE).

Please note the typical operational power modes:

OFF All systems are OFF. The engine and electric drive system are powered off.

Same as ACC on a conventional vehicle. ACCESSORY In this mode the engine will not run, nor will the vehicle move under electric power.

POWER ON Equivalent to KOEO – Key ON/Engine OFF

Equivalent to KOER – Key On/Engine Running

READY TO DRIVE In this mode the vehicle is ready to drive. The engine is running, or is OFF and ready THEME 3.3.2 to run if so commanded. The electric drive system is also ready for a drive command.

(vii) Diagnose the cause of a hybrid system warning displayed on the instrument panel and/or a driveability complaint. (viii) Diagnose impact sensor problems, determine repairs. (ix) Diagnose AC/DC inverter overheating, determine repairs. (x) Diagnose AC/DC inverter failure, determine repairs. (xi) Replace AC/DC inverter cooling pump. (xii) Remove and install AC/DC inverter. (xiii) Diagnose failures in the data communications bus network, determine repairs. (xiv) Locate and test the ‘voltage’ level of capacitors. (xv) Diagnose, locate and safely disable/enable safety interlocks. (xvi) Diagnose failed DC/DC converter, determine repairs. (xvii) Remove and install DC/DC converter. (xviii) Test high ‘voltage’ cable integrity and loss of isolation. (xix) Perform 12-volt battery testing. (xx) Diagnose system main relay (SMR)/contactor malfunctions, determine repairs.

249 Exercises 1. Explain the practicable steps to ensure safe EV servicing. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

THEME 3.3.2 ……………………………………………………………………………………… ……………………………………………………………………………………

2. List and explain the relevant service tasks for the EV battery and drive system, and electronic controllers. …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Further Information on the Resource CD

(i) Ford Focus Electric Emergency Response Guide, 2013. (ii) Ford Focus Electric Battery Removal Guide, 2016. (iii) Tesla Model S Emergency Response Guide, 2016. (iv) Coda Emergency Response Guide, 2012

250 Your own notes NOTES

251 Your own notes NOTES

252 TOPIC

Application of Wind Turbine and Fuel Cell Systems and Batteries

Topic Overview

is textbook has covered a wide range of renewable technologies and their principal backgrounds. In Topic 4 we will combine some basic mathematical skills and engineering science, and focus on experiments and practical work. In other words, we will be focussing on technology application and problem solving with an emphasis on practical skills, because whatever eld you as an aspiring artisan or technician choose to go into, you will need to have a sound basic understanding of these skills for successful further learning, be it manufacturing, servicing or repairs. To make this RET training programme truly e ective, it is necessary to practically apply your knowledge in hands-on experiments or real-world installations. Given that the latter is o en di cult to realise in some TVET colleges, we o er you modular experiments designed to demonstrate most of the aspects of small-scale wind turbine and fuel cell systems covered in this textbook, albeit on a limited scale.

Topic 4 covers the following units: Unit 4.1 Connect Wind Turbine Components using Didactical Training Kits or Small-Scale Industrial Components Unit 4.2 Connect Fuel Cell System Components using Didactical Training Kits Unit 4.3 Explain the Operation and Performance of Batteries for Renewable Energy Systems

253 THEME 4.1.1 Unit 4.1

UNIT 4.1 CONNECT WIND TURBINE COMPONENTS USING DIDACTICAL TRAINING KITS OR SMALL-SCALE INDUSTRIAL COMPONENTS

Introduction

In Unit 2.1 we introduced you to the basic underlying principles of wind power technologies, covering some elementary aspects of kinetic and electrical energy and the laws of electromagnetism. In this unit you need to practically apply your knowledge in hands-on experiments and Do-It-Yourself (DIY) activities, or even real-world installations if your college installed a small turbine, for example Kestrel’s 1 kW island system. However, given that only few colleges installed the latter, this unit will focus on modular experiments using didactical training kits. Unit Outcomes

At the end of this unit, you should be able to: (i) Identify the components of wind turbine training sets (IKS or leXsolar respectively). (ii) Determine the output power of a generator at di erent wind speeds. (iii) Determine the output power of a generator depending on the number of blades, blade position/ pitch and blade shape. (iv) Record the V/I characteristic line of a generator at a constant number of revolutions. (v) Record the V/I characteristic line of a generator on the resistor with drive rotor at constant wind speed. (vi) Charge an accumulator using a wind generator. (vii) Set up an isolated network. (viii) Perform testing and fault nding on all of the above setups. If available, perform testing and fault nding on installed small-scale installations and, in hypothetical context, large-scale installations. (ix) Re ect on the installation, commissioning and servicing of electrical equipment and cabling on turbines, transformers and substations, high-voltage switchgear and erection of high- and low-tension power lines. Themes in this Unit

Unit 4.1 covers the following two themes: eme 4.1.1 Experiments with Wind Turbine Training Sets eme 4.1.2 Build your own Wind Turbine

254 THEME 4.1.1 EXPERIMENTS WITH WIND TURBINE TRAINING SETS

Introduction

e components required for building and experimenting with simple HAWT models are available in two commercial training kits, the IKS Windtrainer Junior set or the leXsolar-Wind training set. At least one of the two types of training kits need to be available at your college for RET Level 4. Keywords

Wind power (input) THEME 4.1.1 Generator power (output) Blade number Blade shape Blade position / pitch I/V characteristics Charging Network setup Testing and fault nding Installation, commissioning and servicing High-voltage switchgear High- and low-tension power lines Theme Outcomes

At the end of this theme, you should be able to: (i) Identify the components of wind turbine training sets (IKS or leXsolar respectively). (ii) Determine the output power of a generator at di erent wind speeds. (iii) Determine output power of a generator depending on the number of blades, blade position/pitch and blade shape. (iv) Record the I/V characteristic line of a generator at a constant number of revolutions. (v) Record the I/V characteristic line of a generator on the resistor with drive rotor at constant wind speed. (vi) Charge an accumulator using a wind generator. (vii) Set up an isolated network. (viii) Perform testing and fault nding on all of the above setups. If available, perform testing and fault nding on installed small-scale installations and, in hypothetical context, large-scale installations. (ix) Re ect on the installation, commissioning and servicing of electrical equipment and cabling on turbines, transformers and substations, high-voltage switchgear and erection of high- and low-tension power lines. Deﬁ nition of Terms Training Kit Components Identify which type of training set is available at your college - either the IKS Windtrainer Junior set or the leXsolar-Wind training set. Familiarise yourself with the respective training kit and identify all individual components before you start with the practical activities/experiments. As already indicated in eme 2.1.4, you need to consult the student manual of your respective training set for more information and descriptions of the components, particularly for operating instructions and experimental setup.

Please remember that all components, particularly the wind machines and the rotor parts, need to be handled with care! Please note that the rotor must not be touched during rotation/movement due to the risk of injury! ! Consider all safety instructions as outlined in the respective student manuals! 255 FIGURE 1: THE IKS WINDTRAINER JUNIOR SET (LEFT) AND THE LEXSOLAR-WIND TRAINING SET (RIGHT) THEME 4.1.1

Image source: Dörthe Boxberg

FIG U RE 2: EACH TRAINING KIT USES DIFFERENT COMPONENTS

Image source: Dörthe Boxberg

e individual components of each training kit - either the IKS Windtrainer Junior set or the leXso- lar-Wind training set - are rather di erent regarding their design and their speci cations. Compare for example the wind machine from IKS (le ) with the one from the leXsolar (right). It is thus important that you familiarise yourself with the respective training kit and all of its individual components before you start with the practical activities.

Activity 1: Wind power input und generator output

Please consider that you may have either the IKS Windtrainer Junior set or the leXsolar-Wind training set available at your college! In the IKS Windtrainer Junior set this activity is called Experiment 1! In the leXsolar-Wind training set this activity is called Experiment 1.2. Also, see and perform the follow- ! ing related Experiments 1.1 and 1.3! Regarding the required components and setups, please consult the student manual of your respective training set! Objective is activity is designed to determine the relationship between wind machine input and generator output, i.e. what kind of correlation exists between wind speed (input) and generator output. In other words, we want to nd out if generator ‘voltage’ (output) is indeed a function of wind power input.

256 Background information In eme 2.1.2 we explained the three most crucial factors relevant to determine wind power (input) and obtained the following formula: 3 Pwind = (v ) ଵ ଶ ߩܣ According to this formula wind velocity (v) is the most crucial factor for input power, followed by the

swept rotor area (A) and air density (ρ). erea er, we introduced the power coe cient (Cp) as a measure 3 of overall wind turbine3 e ciency. e Cp is de ned as the ratio of power Poutputoutput = (watt, W) produced by (v a) Pwind = (v ) wind turbine divided by the total power input. When de ned in this way, the C representsଵ the combined � p e ciency of the various turbine system components, including the turbine blades, the shaଶ bearings and � ܥ݌ ߩܣ gear train, x � generator x � x and power electronics. e output power of a wind turbine generator can thus be described as: 3 THEME 4.1.1 Poutput = p (v ) � � x � x � x � x Ideally, all kinetic input energy can be converted� to mechanical and subsequently electrical energy. Aero- dynamic, mechanical and electrical power losses however make this impossible - thus the introduction of

the power coe cient (Cp) as a measure of overall turbine e ciency. In other words, due to aerodynamic, mechanical and electrical power losses, overall turbine e ciency is limited and optimisation of all wind turbine elements is crucial. As explained under aerodynamic e ciency in eme 2.2.1, rotor blades are crucial and elementary parts of a wind turbine. Rotor blades extract the linear kinetic energy present in the wind and convert it to rotary sha motion which again drives the generator. Much experimentation has been carried out to optimise turbine rotors regarding to blade number, blade shape, and blade position/pitch.

FI G U R E 3: INSERTING THE ROTOR BLADES (IKS WINDTRAINER JUNIOR)

Image source: Dörthe Boxberg

257 FIGURE 4: WIND TURBINE AND ROTOR BLADE SETS (LEXSOLAR) THEME 4.1.1 Image source: Dörthe Boxberg

Hypothesis It can be expected that generator output is indeed directly proportional to wind power input: the higher the wind speed, the higher the rotational rotor speed and subsequently the generator output. Conse- quently, a linear correlation between output ‘voltage’ and power input (wind speed) can be assumed.

FI G U R E 5: SCHEMATIC SETUP OF ACTIVITY 1 USING IKS WINDTRAINER JUNIOR

Figure 5: Schematic set-up of activity using IKS Windtrainer Junior

Power r supply achogenera to rT Speed Wind energieanlage Wind turbine control Genera to

OFF DC DC V A

Volt (U) Ampere (I) Multimeter

Image source: S4GJ/GIZ

258 FIGURE 6: SCHEMATIC SETUP OF ACTIVITY 1 USING THE LEXSOLAR- WIND TRAINING SET

Figure 5: Schematic set-up of activity 1 using the leXsolar-Wind training set THEME 4.1.1

Image source: S4GJ/GIZ.

Setup Please note that the rotor con guration for this activity is di erent for each training kit. IKS for example uses a rotor con guration of 4 at blades adjusted at a 45º pitch angle (see also Activity 4). e leXsolar kit requires a 3-blade con guration (air foil type blades) adjusted at a 25º pitch angle (see also Activity 4). Conducting the activity Follow the instructions for this experiment according to your respective training set as indicated under “Assignment” in the IKS workbook (Experiment 1), and under “Execution” in the leXsolar manual (Ex- periment 1.2) and perform testing and fault nding as required. Ensure that the rotor blade locking bolts (Figure 7) are tightened with caution, not more than hand-tight. Consider that the rotor might need some time to produce consistent output values for each setting - record your measurements only when the readings on the multimeter no longer uctuate. Further, ensure that you use the predetermined charts for speed readings (v in m/s or rpm).

F I G U R E 7: CAREFULLY TIGHTEN THE ROTOR BLADE LOCKING BOLTS

Image source: Dörthe Boxberg

259 Measurements Use the respective tables to document your measurements (generator ‘voltage’) for each knob division (IKS) or wind machine setting (leXsolar). Consult the predetermined charts to determine the corresponding wind speeds (v in m/s).

Result interpretation Enter the measured ‘voltage’ values against their respective speed values (m/s) into your respective chart. Connect the dots by drawing a line for each ‘voltage’-/ wind speed pair. Interpret the resulting line in your chart by answering the following three questions and the questions in your respective workbook:

(i) Describe the relationship between the two variables ‘voltage’ and ‘wind speed’! THEME 4.1.1 ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

(ii) Explain the correlation between the two values! ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

(iii) Can you accept the hypothesis or must you reject it? Explain your views! ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

260 FIGU RE 8: HYPOTHETICAL PROGRESSION OF THE OUTPUT CURVE IN THE LEXSOLAR CHART Figure 8: Hypothetical progression of the output curve in the leXsolar chart

6 Output in volt (V)

4 THEME 4.1.1 3

Wind speed in m/s 0 0 1 2 3 4 5 6 7 8

Image source: GIZ/S4GJ

FIGURE 9: HYPOTHETICAL PROGRESSION OF THE OUTPUT CURVE IN THE IKS CHART

Figure 8: Hypothetical progression of the output curve in the IKS chart

11 Wind speed in m/s 10

1 ‚ Divisions on voltage‘ knob 0 0 1 2 3 4 5 6 7 8 9 10

Image source: GIZ/S4GJ

261 Activity 2: Generator output as a function of blade number

THEME 4.1.1 is activity is designed to determine whether generator output power is indeed a function of blade numbers. We want to nd out whether the number of blades, i.e. 2, 3 or 4 blades, has an in uence on the output power of the generator. Background information Each rotor design has its unique purpose. Let us consider two extremes, the iconic multi-blade windmill rotor and the modern three-blade HAWTs. e multi-blade windmill has been and is still used to pump water. ree-blade HAWTs are used to generate electrical power. Rotor design thus depends on what you want to do with the turbine, i.e. pumping water or generating electrical power. e important aspect here is that the number of blades dictates the relationship between rotational speed of the rotor hub/sha and the torque that is produced by the rotor. e swept area of a multi-blade windmill rotor is almost fully covered with blades. As soon as wind reaches the rotor, each blade produces an angular momentum on the rotor sha (torque). Since we have a lot of blades, this momentum is multiplied. However, as the rotor begins to turn, each blade will create drag which in turn limits the rotational speed of the rotor. A mechanical pump needs a lot of torque. In this case, rotational speed is secondary and what you are really a er is creating as much torque as possible - a rotor with lots of blades is thus the best choice for the job.

FIGURE 10: DIFFERENT HAWT TYPES

One blade Two blades Three blades Multi-blade

Image source: GIZ/S4GJ

Today, almost 90% of installed HAWTs have three rotor blades. As we could see in multi-blade windmill rotors, with more blades on a rotor the torque would be higher, i.e. the force that creates rotation, and the slower the rotational speed because of the increased drag caused by wind ow resistance. But we can also recall that turbines used for generating electrical power need to operate at high speeds and actually don't need that much torque. us, rotors require a compromise regarding high rotational speed, minimum

262 stress, and the number of blades suited for a particular turbine to produce the optimal amount of power. A one-bladed turbine is the most aerodynamically e cient con guration. However, it is not very practical because of stability/stress problems. Turbines with two blades o er the next best design, but are af- fected by a wobbling phenomenon. Since wind turbines must ideally always face into the wind, the blades will have to change their direction vertically when there is a shi in wind direction. is is referred to as “yawing”. In the case of a two-bladed system, when the blades are vertical, i.e. in line with the tower and the axis of rotation, there is very little resistance to the yawing motion. But when the two blades are in the horizontal position, the blades span a greater distance from the axis of rotation and experience maximum resistance to yawing. As a result, the yawing motion starts and leads to stress on the turbine due to blade chattering. A turbine rotor with three blades on the other hand shows very little vibration or chatter. is is due to the fact that when one blade is in the horizontal position its resistance to the yaw force is counter-bal- anced by the two other blades. A three-bladed turbine usually represents the best combination of high rotational speed and minimum stress, and is thus a good compromise for power generation. e number THEME 4.1.1 of blades can thus be considered as a trade-o of many aspects which the designer has to be concerned about. Hypothesis It can be expected that generator output power is indeed in uenced by the number of rotor blades. e higher the number of blades, the higher the torque, but, the slower the rotational speed. To produce a high amount of electric power however, turbines need to operate at high speeds. One could assume that a compromise regarding high rotational speed and minimum stress would o er the best rotor design. Consequently, a compromise of 3 or 4 blades might be the ideal rotor con guration.

FIGU RE 11: THE IKS WINDTRAINER JUNIOR SETUP FOR ACTIVITY 2, 3 AND 4

Image source: Dörthe Boxberg

Setup Both training kits use 2, 3 and 4 blade rotor con gurations to investigate potential e ects of blade numbers on generator output.

263 FIG U RE 12: SCHEMATIC SETUP OF ACTIVITY 2, 3 AND 4 USING IKS WINDTRAINER JUNIOR

Figure 12: Schematic set-up of activity 2,3 and 4 using IKS Windtrainer Junior

Power r supply achogenera to rT Speed Wind energieanlage Wind turbine control Genera to THEME 4.1.1

OFF OFF DC DC DC DC V A V A

Volt (U) Volt (U)

Ampere (I) Ampere (I) Multimeter Potentiometer Multimeter

Image source: GIZ/S4GJ

FI G U R E 13: SCHEMATIC SETUP OF ACTIVITY 2, 3 AND 4 USING THE LEXSOLAR-WIND TRAINING SET

Figure 13: Schematic set-up of activity 2,3 and 4 using the leXsolar-Wind training set

V A

Image source: GIZ/S4GJ

264 FIGURE 14: ENTER THE MEASURED VALUES INTO THE TABLES PROVIDED THEME 4.1.1

Image source: Dörthe Boxberg

Conducting the activity Follow the instructions for this experiment according to your respective training set, i.e. as indicated under “Assignment” in the IKS workbook (Experiment 3), and in the leXsolar manual (Experiment 9.2). Perform testing and fault nding as required. A certain number of blade arrangements are required and you need to make sure that the locking bolts are tightened with caution - not more than hand-tight. Consider that the individual rotor arrangements, i.e. 2, 3 and 4 blade rotor con gurations might need some time until they produce consistent output values for each setting, i.e. potential di erence (‘voltage’, V in volt, V) and current (I in milliampere, mA). Record your measurements only once the readings on the multimeters no longer change/ uctuate. Further, ensure that you use the predetermined charts for speed readings (v in m/s or rpm). Lastly, maintain similar blade shape and pitch arrangements for each rotor con guration, i.e. 2, 3 and 4 blade rotor setups. Measurements Use the respective tables to document your measurements for each rotor con guration, i.e. a 2, 3 and 4 blade rotor design (Figure 14). Calculate the power output (P = V x I, in mW) and consult the predetermined charts for speed readings (v in m/s or rpm). Result interpretation Enter the respective power values (mW) against their respective speed values (either m/s or rpm) for each rotor con guration (a 2, 3 and 4 blade rotor design) into your chart. Connect the dots by drawing a line for each rotor con guration. Use di erent colours for each rotor con guration, e.g. use a red pen for a 2-blade con guration, a blue pen for a 3-blade con guration and a green pen for a 4-blade con guration. If you do not have di erent colours available, mark each of the three lines with a di erent symbol, e.g. a triangle, a circle and a square. Each rotor con guration is now represented by a separate line. Each of the three lines illustrates the dependency of power output on rotor speed. Interpret the three resulting lines in your chart by answering the following three questions and the questions in your respective workbook:

265 (i) Which rotor con gurations/rotor speeds generated the highest power outputs (mW)? ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… THEME 4.1.1 (ii) Explain the correlation between rotor con gurations, i.e. number of blades and generated output power! ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

(iv) Consider and re ect on your ndings in context of large-scale installations. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

266 FI G U R E 15: HYPOTHETICAL PROGRESSION OF CURVES IN DIFFERENT CHARTS Figure 15: Hypothetical progression of curves in different charts

6 P in mW

4 THEME 4.1.1 3

v in m/s 0 0 1 2 3 4 5 6 7 8 Two-blade rotor Three-blade rotor Four-blade rotor

150 140 P in mW 130 120 110 100 90 80 70 60 50 40 30 20 10 v in m/s 0 0 200 400 600 800 1000 1200 1400 1600 1800

Two-blade rotor Three-blade rotor Four-blade rotor

Image source: GIZ/S4GJ

e top image is a leXsolar chart example, below is an IKS chart example. Both charts show hypothetical results (power vs speed) for the three di erent rotor con gurations.

267 Activity 3: Generator output power as a function of blade shape

THEME 4.1.1 is activity is designed to determine whether generator output power is indeed a function of blade shape. In other words, we want to nd out whether blade shape (i.e. near air foil cross-section, or less optimised pro les, e.g. at or level blades), has an in uence on the output power of the generator.

FIGURE 16: CURVED ROTOR BLADES (CONCAVE / CONVEX) FROM IKS’S WINDTRAINER JUNIOR SET

Image source: Dörthe Boxberg

Background information Modern, high capacity wind turbines typically have rotor blades with a cross-section very similar to an aeroplane or bird wing. is type of shape is also known as an air foil. An air foil has air owing around it and, as a result, is subject to aerodynamic forces which create movement. Wind turbine blades experience mainly two aerodynamic forces: li and drag which appear perpendicular to each other.

268 F I G U RFigure E 17: 17:AIR Air FOIL foil cross-selectionCROSS-SECTION and aerodynamicAND AERODYNAMIC forces FORCES

Lift

Thrust Drag THEME 4.1.1 Weight

Image source: GIZ/S4GJ

In an air foil, the upper surface of the blade is more rounded than the lower surface. A simpli ed explanation of li is when wind travels over the upper curved surface of the blade, it has to move faster to reach the end of the blade in time to meet the wind travelling under the lower at surface of the blade. Since faster moving air tends to rise in the atmosphere, the curved surface ends up with a low-pressure area above it and creates an e ect known as li (see the three videos provided on the resource CD on the Bernoulli’s principle). As explained in eme 2.2.1 and already in RET Level 2 ( eme 2.1.1), it is essentially the li force that creates the angular momentum in the rotor blades. Opposing the li ing force is the drag force, perpendicular to li and parallel to the direction of motion. Drag causes turbulence around the trailing edge of the blade as it cuts through the air. is turbulence has a braking e ect on the blade - thus we want to make this drag force as small as possible. e combination of li and drag causes the rotor to spin. Hypothesis It can be expected that generator output power is indeed in uenced by the blades’ shape. Compared to blades with a at shape, one could assume that blades with a cross-section similar to an air foil (concave/ convex) would receive more li and less drag (Bernoulli principle). us, an optimised angular rotor momentum and higher rotational speed at equal wind conditions subsequently results in higher power outputs. Setup To investigate potential e ects of blade shape on generator output, both training kits use two blade shapes: blades with optimised shapes (air foil type, concave/convex types) and at blades. e experimental setup is the same as described in Activity 2 (see Figure 11, 12 and 13). Conducting the activity Follow the instructions for this experiment according to your IKS workbook assignment or the leXsolar manual. Perform testing and fault nding as required. Consider that the IKS assignment requires a two-blade rotor arrangement, while the leXsolar manual requires a three-blade arrangement. A certain number of blade arrangements are required and you need to make sure that the locking bolts are tightened with caution - not more than hand-tight. Mount the at blades rst and maintain the given angle of attack (60º). Set the given wind speed and ensure that you use the predetermined charts for speed readings (v in m/s or rpm). A er measuring ‘voltage’ (V in volt) and current (I in milliampere) for the at blades, mount the concave/convex blades (IKS) or the air foil type blades (leXsolar) and take similar measurements in accordance to the rst round of settings. Consider that the di erent con gurations might need some time until they produce consistent output values for each setting - record your measurements only once the readings on the multimeters no longer change/ uctuate.

269 Measurements Use the respective tables to document your measurements (V in volt and I in milliampere) for each shape con guration. Calculate the power output (P = V x I, in mW) and consult the predetermined charts for speed readings (v in m/s or rpm).

FIGU RE 18: ENTER THE MEASURED VALUES INTO THE TABLES PROVIDED AND ANSWER ALL QUESTIONS THEME 4.1.1

Image source: Dörthe Boxberg

270 FI G U R E 19: HYPOTHETICAL CURVE PROGRESSION (POWER VS WIND SPEED) Figure 19: Hypothetical curve progression (power vs wind speed)

6 P in mW

4 THEME 4.1.1 3

v in m/s 0 0 1 2 3 4 5 6 7 8

Image source: GIZ/S4GJ A chart example for the leXsolar training kit Result interpretation e IKS workbook requires you to answer only two questions. e leXsolar manual on the other hand requires you to enter the respective power values (mW) against the respective speed value (either m/s or rpm) of each blade type into a chart. Connect the dots by drawing a line for each rotor con guration. Use di erent colours for each of the two blade shapes, e.g. use a red pen for a at-blade con guration and a blue pen for air-foil con guration. If you do not have di erent colours available, mark each of the three lines with a di erent symbol, e.g. a triangle and a circle. Each rotor con guration is now represented by a separate line. In other words, each of the two lines illustrates the dependency of power output on blade shape. Interpret the two resulting lines in your chart by answering the following four questions and the questions in your respective workbook:

271 (i) Which blade shapes / rotor speeds generated the highest power outputs (mW)? ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

THEME 4.1.1 ………………………………………………………………………………………

(ii) Explain the correlation between blade shape and generated output power! ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

(iv) Consider and re ect on your ndings in the context of large-scale installations. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

272 Activity 4: Generator output power as a function of blade position/pitch

is activity is designed to determine whether generator output power is indeed a function of blade THEME 4.1.1 pitch. We want to nd out whether blade pitch, i.e. the angle of attack, has an in uence on the output power of the generator. Background information e angle of attack of a rotor blade is the pitch/tilt angle between the direction of the apparent/oncoming wind and the chord line of the blade. Tilt or pitch is the angle of incidence with respect to the oncoming wind (represented by α in the gure below).

FIGURE 20: ANGLE OF ATTACK, ANGLE OF INCIDENCE OR PITCH ANGLE

Figure 20: Angle of attack, angle of incidence or pitch angle

Lift

Drag

Angle of attack

Image source: GIZ/S4GJ

e angle of attack determines the amount of li and drag. As the pitch angle becomes larger, more li is created. As the angle becomes even larger, usually between 20º - 30º, the blade will begin to stall, thus decreasing li . If the rotor blades are in stall position (the lower at part of the blade would be facing into the wind), the blades would not be rotating.

273 FIGURE 21: RELATIONSHIP BETWEEN LIFT, DRAG AND ANGLE OF ATTACK (PITCH) Figure 21: Relationship between lift, drag and sngle of attack (pitch)

Low lift Low drag Angle of attack 5° Laminar ﬂ ow

Maximum lift Approaching stall Drag THEME 4.1.1 Separation point 15°

Stalled condition Low lift Separation point High drag

Turbulent air fl ow Insuffi cient lift to sustain turbine power generation Laminar fl ow

Image source: GIZ/S4GJ

FIG U RE 22: PITCH CONTROL ADJUSTMENTS ALONG THE CORD LINE OF ROTOR BLADES

Image source: GIZ/S4GJ

274 ere is an ideal range of wind speeds to produce optimal output power for each turbine type. However, wind o en uctuates in and out of this speed range, making it hard to reach a consistent power output from a turbine. us, if a rotor could adjust the pitch of its blades based on the speed of the incoming wind, it would be possible to produce close to ideal amounts of power across a large range of wind speeds. e relationship between wind speed, rotation rates of the turbine and the power output of the turbine is therefore critical. Consequently, it is important to keep the rotor blades at an optimum angle of attack, increasing li and e ciency. Large blades therefore o en show a twisted design throughout their length. In addition, the pitch control mechanism allows for the adjustment of pitch angles so that the blades can be turned in or out of alignment with the wind, permitting optimum power generation at di erent wind speeds. Please consider that it is certainly generally important to improve e ciency of machines and processes, but cost reductions are usually more important than pure e ciency. us, in industry the objective is usually to achieve the most economical design. Many possible solutions for an application may exist, however high e ciency with expensive designs cannot win in a cost-concerned economy. THEME 4.1.1 Hypothesis It can be expected that generator output power is indeed in uenced by blade position/pitch. One could assume that the ideal stationary angle of attack corresponds strongly with a certain wind speed. Setup Use an experimental setup as described in Activity 2 (see Figure 11, 12 and 13). To investigate potential e ects of blade position/pitch on generator output, both training kits use a three-blade con guration with various angles of attack. However, the settings of each training kit are di erent: IKS uses two di erent wind speeds (6 and 8 m/sec) and seven di erent angles of attack, from 0º to 90º in increments of 15º, with only one blade shape type, i.e. at blades. leXsolar on the other hand requires only one wind speed setting with ve di erent angles of attack with irregular increments, but compares two blade shapes (air foil type versus at blades) at the same time. Conducting the activity Follow the instructions for this experiment as indicated in the IKS workbook assignment or in the leXso- lar-Wind manual. Perform testing and fault nding as required. A certain number of blade arrangements are required and you need to make sure that the locking bolts are tightened with caution - not more than hand-tight. Mount the at blades rst and start with the minimum angle of attack (IKS = 0º and leXsolar = 20º). Set the given wind speed and measure ‘voltage’ (V in volt) and current (I in milliampere). Consider that the di erent con gurations might need some time until they produce consistent output values for each setting. Record your measurements only once the readings on the multimeter no longer uctuate. Measurements Use the respective tables to document your measurements (V in volt and I in milliampere) for each wind speed and angle of attack con guration. Calculate the power output (P = V x I, in mW).

275 FI G U R E 23: HYPOTHETICAL PROGRESSION OF CURVES IN DIFFERENT CHART TYPES Figure 23: Hypothetical progression of curves in different chart types

300 P in mW

250

200

150 THEME 4.1.1

100

v in m/s 0 0 10 20 30 40 50 60 70 80 90 100 Air foil proﬁ le Flat proﬁ le

130 P in mW 120

110

100

0 0 15° 30° 45° 60° 75° 90°

8 m/s 6 m/s Angle of attack

Image source: GIZ/S4GJ e top image is a leXsolar chart example and below is an IKS chart example. Both charts show hypothetical results (power vs pitch angle). Result interpretation Both IKS and leXsolar require that you enter the respective power values (mW) against their respective angles of attack (angle of incidence) into a chart. Connect the dots by drawing a line for each wind speed (IKS) or blade pro le type (leXsolar). Use di erent colours or indicate the dots/lines with a di erent symbol, e.g. a triangle and a circle. Each of the two lines illustrates the dependency of power output on blade position/pitch. Interpret the two resulting lines in your chart by answering the following four questions and the questions in your respective workbook:

276 (i) With which pitch angles and at which wind speed was the highest power output (mW) generated? ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

……………………………………………………………………………………… THEME 4.1.1

(ii) Explain the correlation between pitch angle and wind speed! ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

277 Activity 5: I/V characteristics of generators (DC)

Please consider that you may have either the IKS Windtrainer Junior set or the leXsolar-Wind training set available at your college! In the IKS Windtrainer Junior set this activity is called Experiment 5. Also perform Experiment 6! ! In the leXsolar-Wind training set this activity is titled Experiment 10! Regarding the required components and setups, please consult the student manual of your respective training set! Objective is activity is designed to record the I/V characteristics of a generator at a constant number of revolu-

THEME 4.1.1 tions. is will allow you to determine the internal resistance at maximum power output of the generator. Background information Current–voltage characteristics or I/V curves show a relationship, typically represented as a chart or graph, between the electric current (I) which ows through a circuit, device, or material, and the corresponding potential di erence (V) across it. e simplest I/V characteristic involves a resistor, which according to Ohm's law exhibits a linear relationship between the applied ‘voltage’ and the resulting electric current (Figure 24 and charts in Figure 26). However, factors such as resistor temperature or characteristics of the resistor material can produce a non-linear relationship as well.

FIGU RE 24: RELATIONSHIP BETWEEN ‘VOLTAGE’ (V ) AND CURRENT (I) IN A CIRCUIT

„ Figure 24: Relationship between voltage“ (v) and current (I) in a circuit

Current ﬂ ow A Ammeter

R Circuit Voltage V V resistance

Linear value R

Voltage -V +V

Image source: GIZ/S4GJ e relationship between ‘voltage’ (V) and current (I) in a circuit of constant resistance (R) would produce a straight line and a slope equal to the value of the resistance.

e relationship between potential di erence (V), current (I) and resistance (R) forms the basis of Ohm’s law. us, an increase of potential di erence in a linear circuit of xed resistance will cause an increase of current. Similarly, if we decrease potential di erence, current values will increase as a result. Likewise,

278 if we increase resistance, current decreases for any given ‘voltage’ and if we decrease resistance, current values will increase. Consequently, we can see that current ow around a circuit is directly proportional (V) to potential di erence (V↑ causes I↑), but inversely proportional (I/ ) to resistance (R↑ causes I↓). Similar to larger industrial generators, our mini-DC-generator in the turbine∝ has internal resistance due to the resistance of its winding (and if it is not brush-less, the resistance of the brush contacts). When current ows through the generator, ‘voltage’ will drop due to its internal resistance and will consequently reduce the available power output. Maximum power output of a generator can be achieved when load resistance equals internal resistance. is statement is expressed by the maximum power transfer theo- rem stating that to obtain maximum external power from a source (whether a battery or generator/ dynamo) with a nite internal resistance, the resistance of the load must equal the resistance of the source as viewed from its output terminals.

Hypothesis THEME 4.1.1 Considering the above proportionalities between potential di erence (V), current (I) and resistance (R), we can expect that maximum power output of a turbine generator depends, among other things, on load resistance. Setup For the IKS training kit, use the experimental setup as indicated in Figure 11, 12 and 13 (identical to activity 2, 3 and 4 setups). IKS uses a 4-blade rotor, at blades with 60º angles of attack and a constant wind speed of around 1000 rpm, i.e. at a generator ‘voltage’ of 1.5 V. Current and ‘voltage’ are measured at di erent load settings (resistance, R in ohm, Ω) from 0 Ω up to 100 Ω and the power output calculated (P = V x I, in mW). e leXsolar setup (Figure 25) requires a 3-blade rotor with air foil type blades and a 25º angle of attack. Initially, set the potentiometer to maximum (∞) by using the 1 kΩ and the 100 Ω knob. By using the potentiometer module, set di erent potential di erence values, i.e. start your measurements at a ‘voltage’ setting of 5.3 V and reduce ‘voltage’ in steps of 0.2 V, i.e. 21 steps from 5.3 V to 1.4 V and three 0.5 V steps from 1 V to zero volt. Measure current (I) and calculate load resistance (R = V/I in Ω) and power output (P = V x I, in mW) based on your current measurements and ‘voltage’ settings. Conducting the activity Follow the instructions for this experiment as indicated in the IKS workbook assignment or in the leX- solar-Wind manual. Perform testing and fault nding as required. Keep in mind that the multimeter readings might need some time until they produce consistent output values for each setting. Record your measurements only once the current and ‘voltage’ readings on the multimeters are more or less constant.

279 FI G U R E 25: SCHEMATIC SETUP OF ACTIVITY 5 USING THE LEXSOLAR WIND TRAINING SET

Figure 25: Schematic set-up of activity 5 using the leXsolar-Wind training set THEME 4.1.1 V A

Image source: GIZ/S4GJ Measurements Use the respective tables to document your measurements (V in volt and I in milliampere). Calculate the power output (P = V x I, in mW). Enter the respective current (mA) and ‘voltage’ (V) values into a I/V chart. Connect the dots by drawing a line. Next, enter the calculated power output values (mW) versus the measured ‘voltage’ (V) values into the chart. Connect the dots by drawing a I/V regression line and a power output curve. Use di erent colours for the I/V characteristics and the power output curve. Result interpretation Both IKS and leXsolar manuals require that you interpret your results, i.e. the charts. Try to do this by answering the following ve questions and the questions in your respective workbook:

(i) Do your I/V measurements allow drawing a regression line into the chart? Explain the correlation between your I/V measurements! ……………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

(ii) Explain why generator ‘voltage’ decreases by decreasing resistance. Consider in your answer that reduced resistance increases current, which again results in an increase of self-induced ‘voltage’ (emf) which opposes the generator ‘voltage’. ……………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

280 (iii) If you have drawn a bell-shaped curve representing the power output, depending on generator ‘voltage’, map the point of maximum output and then determine load resistance at this point. You can calculate internal resistance by relating your point of maximum output to your I/V line. us, internal resistance (R = V/I in Ω) for the IKS generator is: 720 mV / 80 mA = 9 Ω and internal resistance of the leXsolar generator is around 35 Ω. Compare the load resistance values, the point of maximum output, with your generator’s internal resistance. ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

…………………………………………………………………………………… THEME 4.1.1 ………………………………………………………………………………………

(iv) Can you accept the hypothesis or must you reject it? Explain your views! ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

(iv) Consider and re ect on your ndings in the context of large-scale installations. ……………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… …………………………………………………………………………………… ………………………………………………………………………………………

281 FIGURE 26: HYPOTHETICAL PROGRESSION OF I/V LINES AND OUTPUT CURVES IN DIFFERENT CHART TYPES Figure 26: Hypothetical progression of I/V lines and output curves in different chart types

200 300

250

150 200 Generator current (mA) Generator Generator output (mW) Generator THEME 4.1.1 100 150

100

500 50

0 0

Figure 26: HypotheticalGenerator progression voltage of I/V (V) lines and output curves in different chart types

200 300

250

150

200 Generator current (mA) Generator Generator output (mW) Generator

100 150

100

500 50

0 0

Generator voltage (V)

Image source: GIZ/S4GJ e image on top is a leXsolar chart example and below an IKS chart example. Both charts show hypothetical results for an I/V line and a power output curve.

282 Activity 6: Charging/discharging using accumulators and designing a DC island system

Please consider that you may have either the IKS Windtrainer Junior set or the leXsolar-Wind training set available at your college! In the IKS Windtrainer Junior set this activity is called Experiment 10. Also perform Experiments 11 ! and 12! In the leXsolar-Wind training set this activity is titled Experiment 6.1. Also, perform Experiments 6.2, 7.1 and 7.2! Regarding the required components and setups, please consult the student manual of your respective

training set! THEME 4.1.1 Objective is activity is designed to examine storage and discharge characteristics of an accumulator using a wind generator. Background information Special application of energy storage in connection with wind energy systems can be found in so-called island systems. In this case, the electrical energy generated by wind turbines, for example with the relatively small Kestrel 1 kW turbine, is stored in large accumulators - in the case of the Kestrel setup in a 102 Ah, 48 V battery bank - to be available for consumption in case insu cient wind power limits immediate power generation. us, wind energy island systems, o en in combination with PV systems, allow independent power supply. ese type of systems are most o en used in remote areas where grid power is not at all or not easily available, for example on isolated farms, for telecommunication or medical stations, on drilling platforms, or in inaccessible mountain regions. In the following experiments capacitors are used as accumulators to illustrate the principle of charging and discharging via a wind energy system. Hypothesis Wind energy systems are suitable as island systems to supply power either immediately or via stored power in accumulators (capacitors). Setup For the IKS training kit, use the experimental setup as indicated in Figure 27 and 28 (charging and discharging). IKS uses a 4-blade rotor, convex blades with 60º angles of attack and a constant wind speed of around 8 m/s. IKS uses a so-called GoldCap capacitor which is a device with high capacity. e leXsolar setup (Figure 29) requires a 3-blade rotor with air foil type blades and a 25º angle of attack, the capacitor and the LED module. Observe the polarity when setting up the experiment. Consider that at the start of the experiment, the LED is not connected to the setup. Ensure that cable 1 and cable 2 are plugged into the respective sockets (Figure 29).

283 F I G U R E 27: SCHEMATIC SETUP OF ACTIVITY 6 USING IKS WINDTRAINER JUNIOR

Figure 27: Schematic set-up of activity 6 using IKS Windtrainer Junior Wind energieanlage Wind turbine

Setup for step A, B and C THEME 4.1.1

OFF OFF DC DC DC DC V A V A

Volt (U) Volt (U) Ampere (I) Ampere (I) Wind energieanlage Wind turbine

Setup for step D

OFF OFF DC DC DC DC V A V A

Volt (U) Volt (U) Ampere (I) Ampere (I)

Image source: GIZ/S4GJ

284 FIGU RE 28: DETAILED VIEW FOR ACTIVITY 6 CONNECTIONS USING IKS’S CAPACITATOR MODULE Figure 28: Detailed view for activity 6 connections using IKS´s capacitator module

Connections for step A, B and C Connections for step D

Gold cap Gold cap THEME 4.1.1

Image source: GIZ/S4GJ

FIGURE 29: SCHEMATIC SETUP OF ACTIVITY 5 WITH THE LEXSOLAR WIND TRAINING SET Figure 29: Schematic set-up of activity 5 with the leXsolar-Wind training set

10 cm

1 2

Image source: GIZ/S4GJ

285 Conducting the activity Follow the instructions for this experiment as indicated in the IKS workbook assignment or in the leXso- lar-Wind manual. Perform testing and fault nding as required. Consider that the multimeter readings might need some time until they produce consistent output values for each setting. Record your measurements only once the current and ‘voltage’ readings on the multimeters are more or less constant. Measurements Only IKS requires measurements (in Step F). Use the respective table and chart to document and plot your measurements (V in volt, I in milliampere and t in min). Result interpretation Both IKS and leXsolar manuals require that you interpret your results by answering the questions in your respective workbook. A er you have answered these questions review the hypothesis. Can you ac-

THEME 4.1.1 cept or must you reject it? Explain your views!

Further Information on the Resource CD

(i) IKS workbook (ii) leXsolar manual

286 THEME 4.1.2 BUILD YOUR OWN WIND TURBINE (DIY)

Introduction

As indicated in earlier sections such as eme 2.1.4, we can distinguish between di erent wind turbine types. Based on one of the most common criteria, the position of the rotor axis, we can for example distinguish between horizontal axis wind turbines (HAWT) and vertical axis turbines (VAWT). In this theme we will introduce you to the idea of building your own wind turbine. Given that we would like to encourage you to build a fully functional model which gives you the chance to apply your knowledge and practical skills, we suggest building a VAWT, more speci cally a model that resembles a Savonius type of

model. 4.1.2 THEME is design is based on the Finnish engineer S.J. Savonius’ (1922) idea of mounting two half-cylinders on a vertical sha . is type of turbine can accept wind from any direction and its aerodynamics operates on the basis of drag: one half-cylinder creates more drag in moving air than the other, causing the sha to spin. One advantage is that you can quite easily design and build all major parts for both the mechanical components (frame, sha and half-cylinders) and the electrical components (stator and rotor plate).

FIGURE 1: DIY – BUILDING A HAWT AND/OR A VAWT (SAVONIUS MODEL)

Image source: Dörthe Boxberg Theme Outcomes

At the end of this theme, you should be able to: (i) Understand the design for a VAWT (Savonius model). (ii) Construct all required components for a Savonius model using basic tools and materials. (iii) Assemble all components into a functional model. (viii) Perform testing and fault nding on the proposed setups. Background information

In Unit 2.1 we introduced you to the basic underlying principles of wind power technologies, covering some elementary aspects of kinetic and electrical energy and the laws of electromagnetism. In this theme you need to practically apply your knowledge in hands-on Do-It-Yourself (DIY) activities. is model uses a relatively simple and e cient way to generate electric power: it uses a stator (stationary eld) and a rotor (the rotating eld or armature). e model is thus a simple machine that operates through the interaction of magnetic ux and electric current, based on the fundamental principle of electromagnetic induction (see eme 2.1.3). is is the same basic principle used in almost all wind turbines, even in the large-scale commercial ones.

287 Duration If all materials are available, you will most probably need around 4 hours to complete the model. Safety! Some of the required tools, e.g. utility knives and jigsaws, can be potentially dangerous. So please use them with caution! e blades of most utility knives can be extended and locked into place. Extend the blades only far enough to cut all the way through the material, no further, and make sure they are locked into position while cutting. Also, remember that hot glue can cause serious burns when coming in contact with your skin. e permanent magnets you will be using can cause serious damage to electronic devices. Be sure to keep them away from credit cards, USB sticks or any other devices on which information is stored magnetically/electronically. Tools and materials

THEME 4.1.2 THEME For this activity a number of tools (Figure 2) and materials (Figure 3) are required. For each construction step we will indicate the required materials.

FIG U RE 2: SOME OF THE TOOLS YOU WILL NEED FOR THIS ACTIVITY

Image source: Dörthe Boxberg

288 FI G U R E 3: THE MATERIALS YOU NEED THEME 4.1.2 THEME

Image source: Dörthe Boxberg

FIGURE 4: THE TWO VAWT DESIGNS ONCE ASSEMBLED

Image source: Dörthe Boxberg

289 Construction Step 1: Building the frame As you can see in Figure 4, 11 and 12, our VAWT (Savonius) model requires only a simple frame consisting of a baseplate, two stands, a cross-beam and a central axis. e latter functions as the sha for the turbine blades (two half-cylinders) and the vertical- and cross-beams can be built by using three 22 mm x 22 mm square dowels. e baseplate will not only function as a foundation, but also as the stator (stationary eld).

TA BLE 1: MATERIAL REQUIRED FOR STEP 1

Quantity Item Description and Sources Any type of wood, e.g. plywood or pine boards with 150 mm x 300 mm x 1 Wooden base 20 mm dimensions can serve as the VAWT base.

THEME 4.1.2 THEME These should be around 22 mm x 22 mm and are required to build 3 Square dowels the frame. You need two 300 mm pieces for the vertical parts and one 200 – 250 mm piece for the cross-beam.

4 Wood screws Required for joining the frame elements to the baseplate.

The dowel Ø 6 mm serves as the central shaft for the two half-cylinders 1 Round dowel and thus forms the turbine’s rotor blades.

The washers aim to keep the central shaft in place and are ﬁxed to the 2 Washer central beam and the baseplate. The washer hole diameter shall not be more than 7 - 8 mm.

1 Hot glue One cartridge should be sufﬁcient.

Read the following instructions carefully before you start working: (i) Prepare the baseplate: Use a pencil, ruler and compass and draw the following pattern onto the plate (Figure 5).

FI G U R E 5: PATTERN ON THE BASEPLATE Figure 5: Circular pattern on base board for coil positioning and vertical square dowels

80-100 mm

140-160 mm

Image source: GIZ/S4GJ Draw this circular pattern onto the base board for coil positioning and vertical square dowels

(ii) Sharpen one end of the round dowel (6 mm) using a pencil sharpener. Place a short wood screw into the centre of the baseplate circle so that its head can accommodate the pointed end of the round dowel (central sha ).

290 (iii) Drill a Ø 8 mm hole into the centre of the cross-beam (22 mm x 22 mm square dowel). Using hot glue, join a washer exactly over the cross-beam hole. (iv) Position the two 300 mm vertical square dowels onto the baseplate as indicated on the base board in Step 1. Ensure a 90º angle between the vertical beams and the baseplate by using a framing square. Once you are con dent that the beams are correctly positioned, carefully use hot glue to x them onto the baseplate (v) Once the glue has cooled and hardened you can start assembling all frame elements, i.e. the vertical pieces and the cross-beam. Do not use glue to x the cross-beam onto the vertical ones - use wood screws as you might later want to remove the cross-beam so that you can work on the turbine. (vi) Insert the round dowel (central sha ) through the hole of the cross-beam into the indentation/ head of the wood screw. Ensure a 90º angle between the central sha and the baseplate using a framing square. Ensure that the central sha (round dowel) turns freely. Use only wood screws

to nally assemble the cross-beam onto the vertical beams. 4.1.2 THEME

FIGURE 6: IMPROVED STATOR COIL DESIGN

Image source: Dörthe Boxberg Construction Step 2: Fabrication and assembly of stator coils As shown in Figures 8 and 9, our VAWT (Savonius) model can work with di erent stator designs, i.e. three, four, six or eight coils. All designs will produce a functional model on condition that all instructions are carefully followed. Based on our experience however, the eight coil design is the most rewarding one and we will thus focus on this design.

TA BL E 2: MATERIAL REQUIRED FOR STEP 2

Quantity Item Description and Sources To build a winding jig we recommend using a 22 mm PVC pipe up to 1 PVC pipe 100 mm long.

You require a reel of enamel-coated magnet wire. Wire diameter is ideally 1 Magnet wire between 0.2 – 0.5 mm. The total length required for the 0.2 mm wire is 120 m and 80 m for the 0.5 mm wire.

1 Masking tape 10 mm width.

291 Read the following instructions carefully before you start working: (i) Prepare the winding jig: You are required to use a saw to cut a 5 – 10 mm slot along the whole length (100 mm) of the 22 mm PVC pipe. (ii) Winding the coils: Carefully wind the indicated wire length (120 m/0.2 mm wire or 80 m/0.5 mm wire) around the winding jig for each individual coil. Ensure that around 50 mm of wire is kept uncoiled at both ends (see Figure 6). (iii) Once a coil is completely wound, remove it carefully from the jig and maintain its shape by wrapping masking tape around the coil. Work thoroughly, as maintaining the shape, its thickness and the number of turns for each coil will later pay o by optimising the generator’s output. (iv) Indicate the winding direction on all eight coils using a pencil or felt pen. (v) Carefully scrape around 10 – 15 mm of the enamel insulation from the wire ends. (vi) Test all coils with a multimeter to ensure current ow. Choose an appropriate resistance range on the tester, for example 100 or 200 ohm. Connect the free ends of the coils with each other by

THEME 4.1.2 THEME ensuring that a current can ow through the coils in a clockwise direction. Continue with the next steps if your reading is appropriate.

F I G U R E 7: CLOCKWISE CONNECTION OF EIGHT COILS Figure 7: Clockwise connection of eight coils. Test for current ﬂ ow with a multi-meter.

Image source: GIZ/S4GJ Clockwise connection of eight coils. Test for current ow with a multimeter.

FIGU RE 8: ROTOR AND STATOR OPTION FOR VAWT DESIGN #1

Image source: Dörthe Boxberg Rotor and stator option for VAWT Design #1 (half-cylinders made out of PET bottle)

292 FIGURE 9: ROTOR AND STATOR OPTION FOR VAWT DESIGN #2 THEME 4.1.2 THEME

Image source: Dörthe Boxberg Rotor and stator option for VAWT Design #2 (half-cylinders made out of PVC pipe) Construction Step 3: Stator assembly As indicated in Step 2 and shown in Figures 8 and 9, our VAWT (Savonius) model can work with di erent stator designs, i.e. three, four, six or eight coils. All designs will produce a functional model on condition that all instructions are carefully followed. However, based on our experience the eight coil design is probably the most rewarding one and we will thus focus on this design.

TA B L E 3: MATERIAL REQUIRED FOR STEP 3

Quantity Item Description and Sources Baseboard with 1 See Step 1 frame

8 Coils See Step 3

1 Solder + ﬂux A basic solder station will do.

1 Hot glue One cartridge should be sufﬁcient.

Read the following instructions carefully before you start working: (i) Position all eight coils equally onto the baseboard using the circular pattern you have drawn in Step 1. (ii) Ensure that all free ends of the coils are still connected with each other and that a current can ow through the coils in a clockwise direction (see Step 2). (iii) Use solder to permanently x the connections between the eight coils. Test the connections using a multimeter. Ensure that two ends are free to connect the multimeter and later the recti er to the coil/stator arrangement (see Step 2). (iv) If you are con dent that the coils are equally positioned and current ow is ensured, carefully hot glue them onto the baseplate. (v) Using a multimeter, test the stator arrangements (coils) again.

293 Construction Step 4: Fabrication and assembly of rotor plate/disk As indicated in Step 3 and in the previous gures, our VAWT (Savonius) model can be built by using different rotor disk designs, i.e. up to 8 magnets can be used (Figure 9). All indicated designs will produce a functional model on condition that all instructions are carefully followed. However, based on our experience, the eight magnets/eight coil design is the most rewarding one and we will thus focus on it.

TABLE 4: MATERIAL REQUIRED FOR STEP 4

Quantity Item Description and Sources Round neodymium-iron permanent magnets with a diameter 8 Magnets between 10-25 mm and a thickness of between 2.5 - 4 mm are ideal. THEME 4.1.2 THEME 8 Washer Diameter slightly larger than the magnet diameter.

1 Cardboard An A4 size cardboard sheet is required to build a rotor disk.

1 Hot glue One cartridge should be sufﬁcient.

Read the following instructions carefully before you start working: (i) Prepare the rotor disk: It is very important that the diameter of the rotor disk corresponds with the stator diameter positioned on the baseboard. It is thus recommended to use a similar circular pattern for the rotor disk as we have used for the stator. Figure 10 illustrates the pattern and the position of the magnets.

FIGURE 10: CIRCULAR PATTERN ON CARDBOARD FOR ROTOR DISK

Image source: GIZ/S4GJ

(ii) Draw two circles with the same diameter onto the cardboard. Cut the two circles out and glue them together so that you produce a single circle. (iii) Position the eight washers as indicated in Figure 10. is arrangement is important as it ensures that the position of the magnets corresponds with the arrangements of the coils. (iv) If you are con dent that your magnet/coil arrangement is correctly aligned, carefully hot glue the washers onto the rotor disk. (v) While the glue cools and hardens, you need to determine the polarity of your magnets using a magnetic compass. Indicate the polarity (N or S) on each side of each magnet. (vi) Once the washers are in their correct position and the glue has cooled and hardened you can start placing the magnets onto the washers. Use the alternating polarity arrangement as indicated in Figure 11. (vii) Punch a little hole into the disc’s centre to accommodate the central sha (6mm round dowel).

294 FIGU RE 11: MAGNETS NEED TO BE PLACED IN AN ALTERNATING POLARITY ARRANGEMENT THEME 4.1.2 THEME

Image source: GIZ/S4GJ

Construction Step 5: Fabrication and assembly of rotor blades As you can see in the Figures 13 and 14, our VAWT (Savonius) model can be built by using di erent rotor blade designs, i.e. two half-cylinders can be made out of a plastic bottle or by using a PVC pipe. Both designs will produce a functional model on condition that all instructions are carefully followed.

TA B L E 5: MATERIAL REQUIRED FOR STEP 5

Quantity Item Description and Sources Most soft drinks are sold in plastic bottles made from polyethylene 1 Plastic bottle terephthalate (PET). You can reuse an empty bottle for your model. Clear water bottles with a uniform shape and diameter are the most suitable ones.

As an alternative to the plastic bottle design you can also use a PVC pipe 1 PVC pipe (80 - 100 mm) to build the rotor blades.

Two or three A4 sized cardboard sheets are required to build two top and 1 Cardboard bottom covers (end pieces) for the rotor blades.

Read the following instructions carefully before you start working: (i) Prepare the top and bottom covers: Glue the two or three cardboard sheets together so that you produce a single sheet with an approximate thickness of 10 mm. (ii) Use a pencil, ruler and compass and draw the following pattern onto the cardboard (Figure 12). Ensure that the circle’s diameter (80 – 100 mm) or radius (40 – 50 mm) corresponds with the diameter of your plastic bottle or PVC pipe.

295 FIG U RE 12: CIRCULAR PATTERN ON CARDBOARD FOR TOP AND BOTTOM COVER OF TURBINE BLADES Figure 12: Circular pattern on cardboard for top and bottom cover of turbine blades 80-100 mm 80-100 mm 80-100 mm 80-100 mm THEME 4.1.2 THEME

Image source: GIZ/S4GJ

(iii) Using a utility knife, cut the two covers (end pieces) out and punch a small hole into its centre so that the central sha could pass through it. (iv) Mark one cover as top end piece and the other as bottom end piece. (v) Using a utility knife, cut the top and base part of the water bottle so that what remains is the central cylinder of the plastic bottle. e length of the cylinder can be between 250 - 150 mm. (vi) Cut the plastic cylinder in the middle so that you produce two equal half-cylinders. Each half-cylinder shall function as a turbine blade. (vii) Use sand paper to carefully bu all edges of the two half-cylinders. Sanding will avoid skin cuts and also improves adherence of the glue. (viii) Apply hot glue around one half circle of the top end piece. Quickly position one side of the top end piece to the half-cylinder. Hold both components in position until the glue cools and hardens. (ix) Apply hot glue around the other half circle of the top end piece. Quickly position the second half-cylinder onto it. Hold both components in position until the glue cools and hardens. (x) Repeat the instructions given in (viii) and (ix) for the assembly of the bottom end piece so that both end pieces are glued to the half-cylinders. (xi) Glue the assembled rotor disk onto the bottom end piece. (xii) Once the glue has cooled and hardened, place the almost completed turbine into the frame, i.e. over the coils, and push the round dowel (6 mm) with the sharpened end through the top end piece ( rst from the horizontal beam) and then through the bottom end piece. Construction Step 6: Final turbine assembly If you have followed the recommended steps, all your turbine components are now ready for assembly.

TA BLE 6: MATERIAL REQUIRED FOR STEP 6

Quantity Item Description and Sources 1 Wind machine Use the IKS or leXsolar wind machine for testing.

1 Hot glue One cartridge should be sufﬁcient.

Read the following instructions carefully before you start assembling the turbine: (i) Test that the central sha with the turbine blades turns freely between the cross-beam and the baseboard. (ii) Once you are con dent that your assembly turns freely in the frame, set the distance between the magnets on the rotor disk and the coils on the stator/base board to approximately 3mm. (iii) Connect a multimeter to the stator coils. (iv) Position the wind machine around 150 – 300 mm away from the turbine and test for current

296 ow. You should be able to measure between 1 – 3 VAC. (v) If you are not satis ed with the output of the spinning turbine, carefully adjust/reduce the distance between the rotor disk and stator coils until you are satis ed with the output. (vi) Finally, hot glue the central sha to the rotor blades and the rotor disk, keeping the position set in the previous step (v).

FI G U R E 13: ASSEMBLED VAWT DESIGN #1 THEME 4.1.2 THEME

Image source: Dörthe Boxberg Half-cylinders made out of a PET bottle

FIGURE 14: ASSEMBLED VAWT DESIGN #2

Image source: Dörthe Boxberg Half-cylinders made out of a PVC pipe

297 Construction Step 7: Rectiﬁ er fabrication Our current turbine design functions as an alternator, subsequently producing an alternating current (AC). To turn this alternating current (AC) signal into a strong enough constant ‘voltage’ (DC) signal, devices called ‘recti ers’ can be used. In other words, the conversion of an alternating current (AC) into a continuous current (DC) is called recti cation. Small signal diodes can be used as recti ers in low-power, low-current applications. ese semi-conductor signal diodes will only conduct current in one direction - from its anode to its cathode (forward direction). Our VAWT model must be considered as a low-power application and for these, half-wave recti ers are most o en used. However, they have the disadvantage of their output amplitude being less than the input amplitude. is is due to the fact that there is no output during the negative half-cycle, so half the power is not available and the output is pulsed DC resulting in excessive ripple. To overcome these disadvantages, a number of diodes can be connected to produce a full-wave recti- er. An ideal type of circuit is, for example, a full-wave bridge recti er. is type of recti er uses four

THEME 4.1.2 THEME individual rectifying diodes connected in a closed-loop con guration to produce the desired output. Although we can use four individual diodes to make a full-wave bridge recti er, pre-made bridge recti - er components are available o -the-shelf in a range of di erent sizes that can be soldered directly into a prototyping circuit board. Lastly, in order to produce a steady DC current from a recti ed AC source, a lter or smoothing circuit is very useful. is can be done by using a capacitor placed across the DC output of the recti er. e full- wave bridge recti er gives us a greater mean DC value with less superimposed ripple, while the output waveform is twice the frequency of the input supply frequency. We can therefore increase the average DC output level by connecting a suitable smoothing capacitor across the output of the bridge circuit as shown in Figure 15. Please note that a diode bridge can also be designed to rectify poly-phase AC inputs. For example, for a three-phase AC input, a half-wave recti er consists of three diodes, but a full-wave bridge recti er consists of six diodes.

FI G U R E 15: CIRCUIT DIAGRAM OF A FULL-WAVE BRIDGE RECTIFIER AND SMOOTHING CAPACITOR Figure 15: Circuit diagram showing a full-wave bridge rectiﬁ er and smoothing capacitor

Bridge rectiﬁ er

D4 D1

AC Input

D D 2 3 DC Output Smoothing capacitor

Image source: GIZ/S4GJ

TA B L E 7: MATERIAL REQUIRED FOR STEP 7

Quantity Item Description and Sources Small standard 2 pin rectiﬁer diodes will do. They usually come in assort- 4 Diodes ment kit sets. Please note that the silver ring on the diodes indicates the cathode side of the diode.

1 Capacitor A small smoothing capacitor (3900 µf) will do.

1 PCB A small prototyping circuit board will do.

1 Solder + ﬂux A basic solder station will do.

298 Read the following instructions carefully before you start working: (i) Complete the electrical circuitry of the full-wave bridge recti er according to Figure 15 or use any other suitable circuit. (ii) Test the recti er unit with your assembled VAWT design (set 6). Use di erent loads, such as LEDs or buzzers that already activate in the millivolt range.

FIGURE 16: SIMPLE STATOR PLATE BASED ON 3 COIL DESIGN WITH A SIX DIODE RECTIFIER UNIT THEME 4.1.2 THEME

Image source: Dörthe Boxberg

F I G U R E 17: CONNECTING/SOLDERING THE COILS TO A RECTIFIER UNIT

Image source: Dörthe Boxberg

299 Testing and fault ﬁ nding We have continuously indicated that all proposed designs will produce a functional model on condition that all instructions are carefully followed. However, during assembly or due to lack of appropriate material, construction mistakes may occur causing a dysfunctional setup. In the following section we thus o er you some hints for troubleshooting.

TA BLE 8: TROUBLESHOOTING

Problem Causes Recommended Solutions The pointed end of the dowel is binding in the wood screw posi- Re-sharpen the dowel, or smooth it tioned in the centre of the base with sandpaper. Turbine turns too slowly or board. THEME 4.1.2 THEME only with difﬁculty. Bring the wind machine closer to Wind machine too far away from the turbine or replace it by a blower the turbine. with a higher power rating.

Magnetic force too weak. Substitute with stronger magnets.

Magnets are not positioned in Re-check and correct magnet accordance with coils. orientation on rotor disk.

Re-check and correct coil orienta- Coils are not positioned clockwise. tion on stator/baseboard.

Turbine turns too slowly or only See above. No or not sufﬁcient output with difﬁculty. readings. Ensure proper insulation free Poor multimeter/load connections. connections.

Set to low AC (before rectiﬁer) or Multimeter setting. DC (after rectiﬁer).

Multimeter readings are sufﬁcient Use different loads such as LEDs or but loads (LEDs, buzzer etc.) do not buzzers that already activate in the function. millivolt range.

Further Information

Further information and inspirations for the design and assembly of functional VAWT models can be found at http://www.picoturbine.com. PicoTurbine is generally a good source of ideas and resources for renewable energy education and STEM projects.

300 THEME 4.1.1 THEME 4.1.2 THEME Unit 4.2 Unit

UNIT 4.2 CONNECT FUEL CELL SYSTEM COMPONENTS USING DIDACTICAL TRAINING KITS

Introduction

In Unit 2.2, eme 2.2.2 we introduced you to the basic underlying principles of fuel cell technologies, covering some elementary aspects of electrochemistry. One of the most important applications of electrochemistry appears in context with energy storage and conversion of energy. In this unit you will apply your knowledge in hands-on experiments using the didactical hydrogen training kit.

Unit Outcomes

See theme outcomes.

Themes in this Unit

Unit 4.2 covers only one theme: eme 4.2.1 Experiments with Fuel Cell Training Sets

301 THEME 4.2.1 EXPERIMENTS WITH FUEL CELL TRAINING SETS Introduction

e components required for experimenting with simple fuel cell models are available in the hydrogen training kit. At least two training kits need to be available at your college for RET Level 4. In eme 2.2.2 you were already introduced to the training kit components and carried out two experiments: (i) determining the volume ratio of the gases produced, and (ii) measuring the quantities of gas produced per unit time depending on current. In this theme we will continue with more experiments, including determination of I/V characteristics of the electrolyser and the fuel cell, and operating the electrolyser with

THEME 4.2.1 THEME other renewable energy technologies.

Keywords

Electrolysis Hydrogen E ciency factor Overpotential I/V characteristic Fuel cell Photovoltaic electrolysis systems Load matching Wind power electrolysis systems

Theme Outcomes

At the end of this theme, you should be able to: (i) Identify training kit or industrial components for experiments. (ii) Determine the energy and faradaic e ciency of the electrolyser. (iii) Determine the I/V characteristic line of the electrolyser. (iv) Determine the I/V characteristic line of the fuel cell. (v) Set up an isolated network. (vi) Operate the electrolyser with solar cells. (vii) Operate the electrolyser with a miniature wind turbine. (viii) Operate the electrolyser with solar cells and a miniature wind turbine. (ix) Perform testing and fault nding on all of the above setups.

Deﬁ nition of Terms Training Kit Components Before you start/continue with the experiments, we recommend that you again familiarise yourself with the training kit and identify all of its components. Please also consult the student manual in the training set for more information and descriptions of the components, as well as the operating instructions. In eme 2.2.2 we already brie y described the components and illustrated them with some images, but please consult eme 2.2.2 again and note that all components, particularly the fuel cell and the electrolyser, need to be handled with care! Safety and Commissioning Always read the notes on safety before starting with the experiments. Use only distilled water to operate the electrolyser and the fuel cell. Ensure that all connections have the correct polarity. Carefully store all tting caps from the sleeves in the correct baseplate compartment. Be careful with the Plexiglas housing ! of each device as these are sensitive to impact stress.

302 Preparation for Storage A er each experiment, follow the recommended steps for storing the training kit components in the case. Also remember: (i) Water needs to remain in the electrolyser to prevent the membrane from drying out. us, carefully close the connecting sleeves with the tting caps. (ii) During operation, humidity buildup in the fuel cell is usually su cient to protect the membrane. us, carefully close the connecting sleeves with the tting caps. (iii) e gas storage container needs to be completely empty - use the syringe and a micro ber cloth to achieve this.

Activity 1: Electrolyser efﬁ ciency THEME 4.2.1 THEME

Objective

is activity is designed to determine e ciency values of the electrolyser as dependent variables of current intensity (‘amperage’). Please note that in Activity 1 we consider only electric e ciency but not faradaic e ciency nor faradaic losses. In the IKS training set this activity is called ‘Experiment 3’.

Background information Electrolysis o ers a sustainable hydrogen production pathway. One advantage of electrolysis is that it is capable of producing high purity hydrogen (around 99.99%). However, re nery costs for electrolysis are huge, mainly due to the high amount of electric power needed to produce pure hydrogen. Most common industrial electrolysers have a nominal hydrogen production e ciency of around 70%. Nonetheless, if the required power is supplied via renewable technologies - see experiments ‘Operation of the electrolyser using PV cells’ and ‘Electrolyser operation using a miniature wind turbine’ - negative environmental impact costs, compared to fossil fuel combustion, could drastically be reduced.

How does an electrolyser work? Electrolysers are electrochemical devices which work like a fuel cell in reverse and can split water into its constituent molecules, hydrogen (H2) and oxygen (O2), by passing an electric current through water (Figure 1). When water is decomposed, the ratio of hydrogen gas to oxygen gas produced is 2:1 as stated in the reaction:

+ - Anode 2 H2O  4 H + 4 e + O2

+ - Cathode 4 H + 4 e  2 H2

Total 2 H2O (l)  2 H2 (g) + O2 (g) (E = - 1.23 V)

us, theoretically a potential di erence of 1.23 V is required from an external source to decompose water into its constituent molecules. In practice however, due to electrical and faradaic losses the potential di erence required to split water always exceeds 1.23 V. e di erence between the theoretical decomposition potential, i.e. 1.23 V, and the actual decomposition potential is called ‘overpotential’. For example, if 2.23 V is the actual potential required to cause water to decompose, then the overpotential would be 2.23 V minus 1.23 V = 1 V. e overpotential is a function of the electrode material, the electrode surfaces, the type and concentration of the electrolyte, the current density and temperature. Overpotential is always needed to overcome electrode interactions and is particularly common in electrochemical reactions where gases are involved.

303 FIGURE 1: ELECTROLYSIS REACTION: 2 H2O (L) 2  H2 (G) + O2 (G) THEME 4.2.1 THEME

Image source: GIZ/S4GJ

Energy e ciency (η) is determined as the ratio between useful energy output and energy input. E ciency factors of the electrolyser can be calculated by determining the gas volumes produced and the amount of current used. us, in our case η can be calculated by dividing the amount of chemical energy produced (Ech), i.e. stored in the produced hydrogen gas, by the electrical energy used (Eel).

Chemical energy produced can be de ned as:

Ech = Ho x Vexp

Whereby Ho = Chemical energy / fuel value of hydrogen = 11.7 J/ml (Joule per ml) and

Vexp = Volumes of hydrogen obtained in the experiment.

Electrical energy (in Joule) used can be de ned as:

Eel = U x I x t

Hypothesis It can be expected that due to losses in the electrolyser, such as ohmic resistance and resulting heat, e - ciency is a dependent variable of current intensity.

Setup To investigate e ciency values of the electrolyser, follow the experimental setup as described in the IKS manual Experiment 3 (see also Figure 2). Conduct two measurements as required with two di erent current values, i.e. I = 100 mA and I = 500 mA. Perform testing and fault nding as needed.

304 FIG U RE 2: SETUP FOR ACTIVITY 1

H2 O2 O2 H2 A THEME 4.2.1 THEME

V + -

Image source: GIZ/S4GJ

Measurements Measure potential and hydrogen volume levels for each current setting and register the produced hydrogen volumes (start volume = 0). Use the table in the manual to document your measurements. We indicated some hypothetical results in Table 1 and 2 to illustrate the activity. Result interpretation

e energy e ciency factor η has been given as Ech over Eel. Chemical energy produced is de ned as Ech = Ho x Vexp, whereby Ho = 11.7 J/ml (Joule per ml). Electrical energy used has been de ned as Eel = U x I x t, in Joule. We can now calculate the energy e ciency factor η using the hypothetical results from Table 1 for each current setting using Table 2.

TA BLE 1: HYPOTHETICAL RESULTS (BLUE FONTS) OF ACTIVITY 1

I (mA) V (V) t (min) H2 Start Volumes (ml) H2 End Volumes (ml) H2 ∆ Volumes (ml) 100 1.5 12 0 8 8 500 2 4 8 23 15

TA BL E 2: CALCULATING ENERGY EFFICIENCY FACTOR USING HYPOTHETICAL RESULTS η E = H x V E = U x I x t Energy Efﬁciency Factor I (mA) ch o exp el (J) (J) (%) η 100 11.7 J/ml x 8 ml = 93.6 1.5 V x 0.1 A x 720 s = 108 (93.6 J / 108 J) x 100 = 86.6 500 11.7 J/ml x 15 ml = 175.5 2 V x 0.5 A x 240 s = 240 (175.5 J / 240 J) x 100 = 73.1

305 FI G U R E 3: SETUP FOR ACTIVITY 1 THEME 4.2.1 THEME

Image source: Dörthe Boxberg

Remember that we introduced you to the concept of proportionality. In engineering, two variables are proportional if a change in one is always accompanied by a change in the other. ink of two variables X and Y. A directly proportional relationship occurs when X and Y both increase or they both decrease. An indirectly proportional relationship occurs when X increases and Y decreases. As calculated in Table 2 by using hypothetical results, the energy e ciency factor η decreases with increasing current intensity. In other words, η appears to be indirectly proportional to I. Consequently, a higher potential di erence is required for electrolysis to compensate for resistance (ohmic) losses (dissipating heat). Interpret your results further by answering the questions in your IKS workbook and by answering the following:

(i) Can you accept the hypothesis or must you reject it? Explain your views!

306 Activity 2: Electrolyser I/V characteristics

Objective is activity is designed to determine the electric properties of the electrolyser by interpreting its I/V characteristics. In the IKS training set this activity is called ‘Experiment 4’.

Background information As already indicated in eme 4.1.1, current–voltage characteristics or I/V curves show a relationship between the electric current (I) and the corresponding potential di erence (V) across it. e I/V char-

acteristics for most electrical loads, such as resistors, motors/generators, bulbs etc. usually show a linear 4.2.1 THEME relationship between current and potential.

Hypothesis It can be expected that the electrolyser’s I/V characteristic shows a linear relationship.

Setup With the exception that you do not need a timer, the experimental setup from Activity 1 can also be used for Activity 2. Follow the experimental setup as described in Activity 1 and perform testing and fault nding as needed.

Measurements Several measurements are required for current values between 0 to 100 mA. erea er, measurements should be taken in 100 mA steps, i.e. between 100 mA and 500 mA. Measure potential and hydrogen volume levels for each current setting and register the produced hydrogen volumes (start volume = 0). Use the table in the manual to document your measurements. We indicated some hypothetical measurements in Table 3 to illustrate the activity.

TA B L E 3: HYPOTHETICAL RESULTS (BLUE FONTS) OF ACTIVITY 2

I (mA) V (V) 0 1.44 20 1.50 40 1.53 60 1.57 100 1.60 200 1.69 300 1.75 400 1.80 500 1.89

307 FIGURE 4: ELECTROLYSER I/V CHART BASED ON HYPOTHETICAL RESULTS OBTAINED FROM TABLE 3

550

500

450

400

350

300 THEME 4.2.1 THEME 250 Current (mA) 200

150

100

0 0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 Potential difference (V)

Image source: GIZ/S4GJ

Result interpretation Enter the respective current (mA) and ‘voltage’ (V) values into a I/V chart. Connect the dots by drawing a line. As visualised in the chart and unlike many other loads, a minimum ‘voltage’ value, the so-called decomposition potential, in our case around 1.44 V must be supplied to the electrolyser before electrolysis and current ow can be detected. Corresponding with Activity 1, a directly proportional relationship between current and ‘voltage’ can be observed, i.e. current increases when ‘voltage’ increases. Interpret your results further by answering the questions in your IKS workbook and by answering the following:

(i) Can you accept the hypothesis or must you reject it? Explain your views!

308 Activity 3: Fuel cell I/V and P/I characteristics

Objective is activity is designed to determine the electric properties of the fuel cell by interpreting its I/V characteristics. In the IKS training set this activity is called ‘Experiment 6’.

Background information Some information on current–voltage characteristics (I/V curves) were already provided in the previous activity. In addition to I/V characteristics, we will also examine the fuel cell’s power maximum deter-

mined by its P/I characteristics. 4.2.1 THEME

Hypothesis It can be expected that the fuel cell’s I/V characteristics shows a linear relationship, while the P/I characteristics will form a curve indicating the cell’s optimum, i.e. maximum power at reversal point in the curve.

FI G U R E 5: SETUP FOR ACTIVITY 3

O2 H2 V

H2 O2

O2 H2 + - + - A

Image source: GIZ/S4GJ

Setup Follow the experimental setup as indicated in Figure 5 and 6, and as described in the IKS workbook. Per- form testing and fault nding as needed.

Measurements

e aim of the rst measurement is to determine the open circuit ‘voltage’ (Voc). us, the ammeter should not be connected in the rst measurement. erea er, set the ammeter to 10 A, and take all following measurements in 200 mA steps, i.e. between 200 mA and 1800 mA. Measure potential (V) for each current setting and calculate power (mW). Use the table in the workbook to document your measurements. We indicated some hypothetical measurements in Table 4 to illustrate possible results.

309 FIGURE 6: SETUP FOR ACTIVITY 3 THEME 4.2.1 THEME

Image source: GIZ/S4GJ

TABLE 4: HYPOTHETICAL RESULTS (BLUE FONTS) OF ACTIVITY 3

I (mA) V (V) P (mW) 0 0.91 0 200 0.72 144 400 0.65 260 600 0.58 348 1000 0.51 510 1200 0.45 540 1400 0.32 448 1600 0.27 432 1800 0.18 324 Result interpretation Enter the respective current (mA) and ‘voltage’ (V) values into the chart. Connect the dots by drawing a line. erea er, enter the respective power values (mW) into the chart. Connect the dots by drawing a line. We recommend using di erent colours to di erentiate the I /V line (blue) from the P/I curve (orange) in the chart. Indicate the maximum power point with an arrow.

310 F I G U R E 7: COMBINED I/V AND P/I CHART BASED ON HYPOTHETICAL RESULTS OBTAINED FROM TABLE 4

Potential (V) Power (W) 1,0 1,0

0,9 0,9

0,8 0,8

0,7 0,7

0,6 0,6 Power optimum 0,5 0,5 4.2.1 THEME

0,4 0,4

0,3 0,3

0,2 0,2

0,1 0,1

0 0 0 0,2 0,4 0,6 0,8 1,0 1,2 1.4 1,6 1,8 2,0 Current (A)

Image source: GIZ/S4GJ

Interpret your results further by answering the questions in your IKS workbook and by answering the following questions:

(i) Why is the value of the fuel cell for open circuit ‘voltage’ (Voc) below the theoretical value of 1.23 V? Explain your views! ...... (ii) What is the relationship between current and ‘voltage’ regarding proportionality? Explain your views! ......

(iii) Determine maximum power (Pmax) of the fuel cell. Recall the proportionality between the energy e ciency factor η and current intensity. Explain your view in context with your Activity 3 results! ......

(iv) Can you accept the hypothesis or must you reject it? ......

311 Activity 4: Electrolyser operation using PV cells

Objective is activity is designed to showcase electrolyser operation using renewable energy technologies (RET) as power supplies, in this case PV cells. In the IKS training set this activity is called ‘Experiment 7’. Please note that this activity requires the IKS PV training set (Solartrainer Junior, RET Level 2). Background information We already indicated in the previous sections that hydrogen production can ideally be realised by using renewable energy technologies (RET) as a power source. Hydrogen production via electrolysis powered

THEME 4.2.1 THEME by RET is a promising approach for storing solar energy. However, for this technology to be economically competitive, it is critical to develop RET-powered electrolysis systems with high e ciencies, so-called solar-to-hydrogen (STH) e ciencies.

In this activity, we aim to demonstrate the potential of photovoltaic electrolysis systems for solar energy storage. e aspect of cost-e ectiveness can unfortunately not be demonstrated by our miniature components. We thus focus on realising electrolyser operation using the PV modules from the IKS PV training set (RET Level 2). Our miniature photovoltaic electrolysis system needs to produce a large enough potential di erence to operate the electrolysers with no additional power input. Subsequently, to optimise system e ciency, the maximum power point of the PV cells needs to complement the operating capacity of the electrolysers. In other words, the electrolyser serves as the load for the PV cells. e technique to determine an optimally matched load is called load matching.

Open circuit ‘voltage’ (Voc) and short circuit current (Isc) of the PV cells need to be determined rst, followed by PV cell I/V characteristics. It is therefore recommended to review Experiment 11 (I-V curve of a solar cell) in the RET Level 2 textbook (Unit 4.2, p. 356). Additionally, the results of Activity 2 are required, i.e. the electrolyser’s I/V characteristics, to discuss and compare the I/V characteristics of the PV cells and the electrolyser. is is due to the fact that an intersection between the I/V characteristics of the two devices is required to power our miniature photovoltaic electrolysis system. In other words, the PV system needs to supply a certain minimum ‘voltage’ and current intensity for the production of hydrogen (electrolysis starting point).

Hypothesis Under the condition that the PV system (2, 3 or 4 PV cells connected in series) supplies the minimum ‘voltage’ and current intensity for the electrolysis, hydrogen production can be expected. Setup Follow the experimental setup as indicated in Figure 8 and 9 and as described in the IKS workbook. We recommend reviewing Experiment 11 (I-V curve of a solar cell) in the RET Level 2 textbook (Unit 4.2, p. 356). Perform testing and fault nding as needed.

312 FIGU RE 8: RET LEVEL 2 TRAINING SET: 2, 3 OR 4 PV CELLS CONNECTED IN SERIES

Cell inclination 90°!

Spotlight

(Halogen) OFF OFF DC DC DC DC V A V A THEME 4.2.1 THEME

Volt (U) Volt (U) Ampere (I) Ampere (I) Multimeter Multimeter

Image source: GIZ/S4GJ

FIGURE 9: THE ELECTROLYSER POWERED BY 2, 3 OR 4 PV CELLS CONNECTED IN SERIES

Cell inclination 90°!

Spotlight (Halogen) O2 H2 OFF DC DC V A

Volt (U)

Ampere (I) Multimeter + -

Image source: GIZ/S4GJ

Measurements

Firstly, measure open circuit ‘voltage’ (Voc) and short circuit current (Isc) of each PV cell arrangement, i.e. 2, 3 or 4 PV cells connected in series (set up according to Figure 8). Secondly, set the activity up as indicated in Figure 9 and start measuring the current values at the electrolyser (I electrolyser ) for each PV cell arrangement, i.e. 2, 3 or 4 PV cells connected in series. Observe the buildup of hydrogen gas. We indicated some hypothetical results for these measurements in Table 5 to illustrate the activity.

313 Result interpretation Use the values you have registered in Activity 2, i.e. the electrolyser’s I/V characteristics, and transfer them into the chart (Figure 10). Next, draw the electrolyser’s I/V characteristics of the di erent PV cell arrangement, i.e. 2, 3 or 4 PV cells connected in series, into the chart. Lastly, consider how hydrogen production could be increased, e.g. by using additional PV cells.

TA B L E 5: HYPOTHETICAL RESULTS (BLUE FONTS) OF ACTIVITY 4

PV cells 1 2 3 4

Voc (mV) 0.5 1.1 1.65 2.15

Isc (mA) 148 149 150 149

I electrolyser (mA) 0 0 60 140 THEME 4.2.1 THEME

FIGURE 10: HYPOTHETICAL ELECTROLYSER AND PV CELL I-V CHARACTERISTICS

300

250

200

150

100

0 0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2

Electrolyser 1 Solar cell 2 Solar cell 3 Solar cell 4 Solar cell

Potential difference (V)

Image source: GIZ/S4GJ

314 Interpret your results visualised in the chart (Figure 10) by answering the questions in your IKS workbook and by answering the following:

(i) Which of the di erent PV cell arrangements, i.e. 2, 3 or 4 PV cells connected in series, provide su cient power to operate the electrolyser? More speci cally: (A) Indicate in the chart the minimum potential di erence value (and number of PV cells) required to start electrolysis. (B) Indicate in the chart the minimum current intensity (and number of PV cells) required to start hydrogen production...... THEME 4.2.1 THEME ......

(ii) Can you accept the hypothesis or must you reject it? ......

(iii) Could hydrogen production be increased by using additional PV cells? Consider the black PV cell I-V curve in the chart! ......

315 Activity 5: Electrolyser operation using a miniature wind turbine

Objective is activity is designed to showcase electrolyser operation using renewable energy technologies (RET) as power supplies, in this case a miniature wind turbine. In the IKS training set this activity is called ‘Ex- periment 7’. Please note that this activity requires the IKS wind power training set (Windtrainer Junior, RET Level 4). Background information Similar to the previous activity, we aim to demonstrate the potential of wind turbine electrolysis systems

THEME 4.2.1 THEME for solar energy storage. With our miniature components we focus on realising electrolyser operation using the wind turbine from the IKS wind training set. e turbine needs to produce a large enough potential di erence to operate the electrolysers with no additional power input. e electrolyser thus serves as the load for the turbine; the technique to determine an optimally matched load is called load matching.

Open circuit ‘voltage’ (Voc) and short circuit current (Isc) of the turbine needs to be determined rst, followed by the turbine I/V characteristics. It is therefore recommended to review Activity 5 in eme 4.1.1 (I-V curve of wind turbine generator) in Unit 4.1. Similar to the PV modules in Activity 4, the turbine needs to supply a certain minimum ‘voltage’ and current intensity for the production of hydrogen (electrolysis starting point). Hypothesis Under the condition, that the generator in our miniature wind turbine supplies su cient power for the electrolysis, hydrogen production can be expected. Setup Follow the experimental setup as indicated in Figure 11 and 12 and as described in the IKS workbook. According to Activity 5 in eme 4.1.1, we recommend a setup using a 4-blade rotor and curved blades, but with a 75º angle of attack and a maximum wind speed of around 10 m/s. We recommend reviewing Experiment 4 (I-V curve of a turbine generator) in eme 4.1.1. Perform testing and fault nding as needed.

FIGU RE 11: SETUP FOR Voc AND Isc MEASUREMENTS OF THE TURBINE GENERATOR

OFF OFF DC DC DC DC V A V A

Generator Tachogenerator Volt (U) Volt (U) Ampere (I) Ampere (I) Multimeter Multimeter

Image source: GIZ/S4GJ

316 FIG U RE 12: TURBINE GENERATOR CONNECTED TO POWER THE ELECTROLYSER Generator Tachogenerator O2 H2

OFF DC DC V A 4.2.1 THEME + -

Volt (U) Ampere (I) Multimeter

Image source: GIZ/S4GJ

Measurements

Firstly, measure open circuit ‘voltage’ (Voc) and short circuit current (Isc) of the turbine generator (according to setup in Figure 11). We indicated some hypothetical results in Table 6 to illustrate possible measurements. Secondly, set the activity up as indicated in Figure 12 and start measuring the current values at the electrolyser (I electrolyser ). Observe the buildup of hydrogen gas. Reduce the wind speed (vwind) at the wind machine until the electrolyser current reaches zero (I = 0). At this point, document the threshold values of the turbine, i.e. wind speed (vwind in m/s), Voc and Isc. We indicated some hypothetical results in Table 7 to illustrate possible measurements for this limiting case.

TA BLE 6: HYPOTHETICAL RESULTS (BLUE FONTS): MEASURING Voc AND Isc OF THE TURBINE GENERATOR

Voc (V) 3.3

Isc (mA) 105

I electrolyser (mA) 105

TA B L E 7: HYPOTHETICAL RESULTS (BLUE FONTS): MEASURING WIND

SPEED (Vwind), Voc AND Isc OF THE TURBINE AT ELECTROLYSER CURRENT (I = 0 mA)

Voc (V) 1.4

Isc (mA) 10

vwind (m/s) 5

Result interpretation Use the values you have registered, i.e. the electrolyser’s I/V characteristics (see Activity 2 and 4) and the wind turbine characteristics at 10 m/s and the threshold values as documented at the limiting case (electrolyser current I = 0 mA), and transfer them into the chart (see Figure 13). Assume, for approximation, a straight line for both wind turbine characteristics.

317 FI G U R E 13: HYPOTHETICAL I-V ELECTROLYSER AND PV CELL I-V CHARACTERISTICS

300

250

200

150 THEME 4.2.1 THEME Current (mA) 100

0 0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 Potential difference (V)

Wind turbine at electrolyser current I=0 Wind turbine at 10m/s I/V electrolyser

Image source: GIZ/S4GJ

Interpret your results visualised in the chart (Figure 13) by answering the questions in your IKS workbook and by answering the following:

(i) At which point, i.e. point of intersection between the characteristic lines, does the turbine generator provide su cient power to operate the electrolyser? ......

(ii) Can you accept the hypothesis or must you reject it? ......

Further Information on the Resource CD

(i) IKS student workbook Hydrogen Trainer Junior (ii) IKS student workbook Solar Trainer Junior (iii) IKS student workbook Wind Trainer Junior

318 Your own notes NOTES

319 THEME 4.2.1 THEME Unit 4.3

UNIT 4.3 CONFIGURING BATTERIES FOR RENEWABLE ENERGY SYSTEMS

Introduction

In Unit 2.2, eme 2.2.1 we introduced you to di erent types of batteries and the basic principles of electrochemistry. In this unit you need to apply your knowledge in practical activities using small sealed lead-acid batteries.

Unit Outcomes

See eme 4.3.1.

Themes in this Unit

Unit 4.3.1 covers only one theme: eme 4.3.1 Experiments with Batteries

320 e.g. inclined, laterally or even upside-down due to their construction. due to or their upside-down even laterally inclined, e.g. orientation, any in mounted be can they for example batteries, type acid lead rechargeable to ordinary However, compared of have advantages anumber testing. SLAs functional speci regular and c charging cleaning, require still batteries SLA misleading. free‘ is ‘maintenance term the note that please tenance, rent ( At the end of this theme, you should be able you to: be should theme, end ofAt this the Outcomes Theme and set them up in parallel and series connections for measurements of potential di of potential for measurements connections series and erence ( parallel up in them set and (12 (SLA) lead-acid batteries V, or sealed gel cell work with 7Ah) we will activities four following the In Working Sealed Lead-Acid with Batteries Deﬁnition Terms of Keywords Boxberg Dörthe source: Image 1: FIGURE crimping. and stripping for cutting, pliers cable ing includ- connections, the to prepare afew tools need you only 2mm, of at least adiameter with cables and SLA) to your according types lugs (F1 terminal or F2 batteries, the 1below. from Figure Apart in dicated in- (SLA)are lead-acid batteries sealed small with for experimenting components and required etools Introduction BATTERIES WITH EXPERIMENTS THEME 4.3.1 Battery handling Battery failure Battery Overcurrent (SLA) lead-acid batteries Sealed Crimping Polarity parallel and Series (v) (v) (iv) (iii) (ii) (i) I ). SLA cells are also called ‘maintenance free’ batteries. Albeit SLAs do not require constant main- constant do not require SLAs Albeit batteries. free’ ‘maintenance called also are ). cells SLA List the precautions required when handling, installing, charging and maintaining batteries. maintaining and charging installing, handling, when required precautions the List (fault failure of battery causes common List nding). for e requirements the maintenance. and storage Explain battery ective requirements. disconnecting and overcurrent State current. and ‘voltage’ total measure and parallel series, in batteries Connect REQUIRED TOOLS AND COMPONENTS AND TOOLS REQUIRED V ) and cur- ) and 321

THEME 4.3.1 THEME 4.3.1 322 To carry out the next four activities successfully, consider the following: following: consider the successfully, activities four next outTo the carry Activities for Preparations Important Boxberg Dörthe source: Image 2: RE U FIG with venting and overcharge cause ame. guidelines: these following you are that ensure us, may mismatch or terminal cell with working of battery, type asafe consideredas be can cells SLA Albeit Safety (xi) (xi) (x) (ix) (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) (iv) (iii) (ii) (i) Verify your assumptions as indicated in Step 2, 6, 7 and 8. 7and 6, 2, Step in indicated as assumptions your Verify ( potential Measure steps above eight now! the execute Follow and battery the connect Only rst! (current). capacity and ‘voltage’ nominal double both will connection series with parallel Combining parallel. in circuits battery the to wire leads to negative (black/blue) leads negative and leads constant. remain (red) values leads positive potential to positive and connect us, increased is circuit battery the in current nominal the parallel, in connected are Remember, batteries when series. in circuits battery to wire (black/blue) leads constant. remain (red) values leads current positive and to negative connect us, increased is circuit battery of the potential nominal the series, in connected are Remember, batteries when (negative). (positive) red in black/blue and marked are leads negative the and leads epositive appropriate tools. the using crimp and lug carefully for the connections cable the Prepare (copper expensive). of is material waste and Avoid resistance mum. increased to amini- lengths cabling the keep diagram, circuit your and design example to the According (b) (a) following the to answer attempt Always rst: on paper. diagram acircuit as activity for each design circuit required Complete/redraw the terwards! or box af- acontainer in them secure and activities the during unattended Never leave batteries damage! show apparent physical that batteries Never work with state-of-charge! have identical and (same match type/specs) that cells connect Only batteries! the connecting below before you exercises start of for the each rating desired the to achieve i.e. on paper doing, you what are know and diagram goggles acircuit Wear safety design rst values can be expected in each activity? activity? each in expected be can values Based on your battery specs, e.g. 12 di e.g. V, potential specs, which 7Ah, on battery your Based erence ( con be must of circuit kind What gured? BATTERIES CONNECTING WHEN POLARITY TO PAY ATTENTION V ) and current ( current ) and I ). V ) and current ( current ) and I ) Image source: Dörthe Boxberg Dörthe source: Image 4: FIGURE Boxberg Dörthe source: Image 3: E R U G FI FOUR SLA FOUR SLA FOUR CONNECTED IN SERIES AND PARALLEL AND SERIES IN s CONNECTED SERIES IN s CONNECTED 323

THEME 4.3.1 THEME 4.3.1 324 TA BLE 1: 1: BLE TA 5: E R U G FI Follow steps: these ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… 3. ………………………………...... ………………………………………… con be must of circuit kind What gured? 2. 1. 5. 5. diagram. circuit your and (cable) design example connection to the each according Prepare 4. Conﬁguration 1: Increasing maintaining potential, current 1: Activity expected in your circuit? Do your calculations below: calculations your Do circuit? your in expected Based on your battery specs, which potential di potential which specs, erence ( on battery your Based to it le (example next design, diagram circuit your draw 5and ) Figure Consider Measure potential and current and document your results in Table in results 1. your document and current and potential Measure batteries. the connect Carefully BELOW: DOCUMENT YOUR MEASUREMENTS MEASUREMENTS YOUR DOCUMENT ILLUSTRATION THE TO NEXT DIAGRAM CIRCUIT YOUR DRAW I (A) V (V) V ) and current ( current ) and ( V AND AND I ) I IN THE TABLE TABLE THE IN ) values can be be can ) values TA BL E 2: 2: E BL TA 6: FIGURE Follow steps: these 5. 5. diagram. circuit your and (cable) design example connection to the each according Prepare 4. ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… 3. ………………………………...... ………………………………………… con be must of circuit kind What gured? 2. 1. Activity 2: Activity expected in your circuit? Do your calculations below: calculations your Do circuit? your in expected Conﬁguration 2: Increasing maintaining current, potential Measure potential and current and document your results in Table in results 2. your document and current and potential Measure batteries. the connect Carefully di potential which specs, erence ( on battery your Based to it le (example next design, diagram circuit your draw 6and ) Figure Consider BELOW: DOCUMENT YOUR MEASUREMENTS MEASUREMENTS YOUR DOCUMENT ILLUSTRATION THE TO NEXT DIAGRAM CIRCUIT YOUR DRAW I (A) V (V) V ) and current ( current ) and ( V AND AND I ) I IN THE TABLE TABLE THE IN ) values can be be can ) values 325

THEME 4.3.1 THEME 4.3.1 326 TA B L E 3: 3: E L B TA 7: E R U G I F Follow steps: these ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… 3. ………………………………...... ………………………………………… con be must of circuit kind What gured? 2. 1. 5. 5. diagram. circuit your and (cable) design example connection to the each according Prepare 4. ed in your circuit? Do your calculations below: calculations your Do circuit? your in ed Based on your battery specs, which potential di potential which specs, erence ( on battery your Based to it le (example next design, diagram circuit your draw 7and ) Figure Consider Measure potential and current and document your results in Table in results 3. your document and current and potential Measure batteries. the connect Carefully Conﬁguration 3: Increase current and potential two-fold 3: Activity BELOW: DOCUMENT YOUR MEASUREMENTS MEASUREMENTS YOUR DOCUMENT ILLUSTRATION THE TO NEXT DIAGRAM CIRCUIT YOUR DRAW I (A) V (V) V ) and current ( current ) and ( V AND AND I ) I IN THE TABLE TABLE THE IN ) values can be expect- be can ) values TABLE 4: 4: TABLE 8: RE FIGU Follow steps: these 1. 1. 5. 5. diagram. circuit your and (cable) design example connection to the each according Prepare 4. ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… ………………………………...... ………………………………………… 3. ………………………………...... ………………………………………… con be must of circuit kind What gured? 2. expected in your circuit? Do your calculations below: calculations your Do circuit? your in expected Consider Figure 8 and draw your circuit diagram next to it le (example next design, diagram circuit your draw 8and ) Figure Consider Measure potential and current and document your results in Table in results 4. your document and current and potential Measure batteries. the connect Carefully di potential which specs, erence ( on battery your Based Conﬁguration 4: Increase current and potential four-fold 4: Activity BELOW: DOCUMENT YOUR MEASUREMENTS MEASUREMENTS YOUR DOCUMENT ILLUSTRATION THE TO NEXT DIAGRAM CIRCUIT YOUR DRAW I (A) V (V) V ) and current ( current ) and ( V AND AND I ) I IN THE TABLE TABLE THE IN ) values can be be can ) values 327

THEME 4.3.1 THEME 4.3.1 328 overcurrent with individual and appropriately sized fuses. appropriately sized and individual with overcurrent against protected be can battery every and each loadfuse, to the addition in and eventuality this against To currents. guard large very potentially causing failure, separator due e.g. to electrode circuit, short load. the internally and can batteries Batteries lel-connected well: as however concerns ere are other paral- the between i.e. overcurrent, an against circuit the to protect adequate to be appears one fuse di potential current, increasing aterence maintaining and aimed bank battery connected aparallel In GIZ/S4GJ source: Image 9: FIGURE circuit. of the parts all through overcurrent stopsan circuit a series su V,to 4x12 V=48 will fuse one appropriately sized in disconnect any since circuit, the to protect ce di potential to increase series in e.g. erence, connected batteries individual four with bank For abattery system. the from battery the disconnecting terminal, battery positive on the circuit the open/interrupt will device protection the appears, circuit ashort case In battery. the of output terminal positive at the placed usually are devices but these breakers, or circuit on fuses based also is protection circuit Short cables. battery of the rating current the lower be than always should rating fuse the for. rated it case, is any In than more current loaddraws the case in connection shut the down and circuit the open/interrupt system. will battery of devices the and or consumers, types inverter ese an as such load, the between placed are that breakers or circuit fuses uses usually protection Overcurrent Circuit Short and Overcurrent system. current adirect properly in not function will they as for only AC rated service, devices not Do use use. for rated DC are that breakers or circuit fuses to use important it is system current adirect in sider that con- always Please o protection. overcurrent thus and devices on disconnect DC er you overview abrief we section, following the In needed. are systems for battery protection overcurrent and devices connect shock/arc and chemical appropriate dis- DC thermal, risks, ash To required. are minimise assessments speci on each risk-/hazard based and Accordingly, various system, energised. being c battery always as systems you consider battery should batteries, functional in energy stored electrical de-energise easily you cannot as avoided equipmentBut, be should wheneverpossible. on energised working that textbooks RET other all in and textbook of this sections earlier all you in advised we clearly You that may recall Protection Overcurrent and Disconnecting Fuse BATTERIES CONNECTED IN SERIES IN CONNECTED BATTERIES INDIVIDUAL FOUR FOR PROTECTION OVERCURRENT Load battery bank self-destructs due to inadequate fusing protection, costs hardly matter. hardly costs protection, fusing due to inadequate self-destructs bank battery However, automotive a fuses. when than more expensive far are for protection arc fuses acting fast very Further, once. protection provide only can they that is fuses of using Adisadvantage lay before blowing. de- have atime some fuses that Remember breakers. circuit most than rating interrupt arc have ahigher fuses more una arule, are or less As and parts variations. have no by moving temperature they ected event circuit. that of ashort are the in system fuses the of using from eadvantages remove batteries the and short the clear will fuse the installed, and properly If sized terminal. battery positive putbe on the rating. should interrupt arc of fuses ahigh with types ese fuses acting fast very are category last the In to started. get afew times current rated the draw amotor as can motor starts, the delay while will fuse blow. the motors that so it with will used faster are the of fuses fuse, the past types ese drawn blows. fuse before for the afew seconds rating its loadto exceed current the the allow ehigher of fuses fuse adual-element called is Here afuse delay fuses. time place we can category next the In aguide: as calculation following the use could (< systems 100 Wp) battery one single 12 circuits VDC in for small fuses /select but to size protection, consumers. and loads for overcurrent small standards with various ere are circuits choice to protect agood be would fuses one cartridge-type 12 volt Above 5ampere, battery. with below 5ampere circuits DC in used be for example tabs. can of connecting fuses with body types plastic ese encapsulating an or endcaps metal with cylinders or ceramic have glass these Usually automotive are fuses. types smallest considered. to be need of fuses types e three systems, For battery most currents. fault against circuit the protects afuse i.e. circuit, the opens/disconnects and melts material fusible the fuse, of the rating the exceeds current the When ends. its afusible/smeltable conductor has between that adevice is A fuse Fuses GIZ/S4GJ source: Image 10: FIGURE (vi) (vi) (v) (iv) (iii) (ii) (i) above example only for small single battery systems. battery single for only small above example Use the more is complicated. applications DC for larger protection overcurrent Calculating breakers. circuit and fuses of cables, sizing for the batteries and inverter your with came that manual instruction the you use We that recommend always cables. circuit of the rating current the lower be than always should rating fuse lated calcu- the case, any In 10 used. be Ashould usually size, next or the a9Afuse example, this In 7.5 by 20%: value Ax1.2 current =9A calculated the Increase P/V=I battery: the from drawn current of maximum Calculation W of 90 maximum atotal in drawing consumers with 12 circuit VDC BATTERIES CONNECTED IN SERIES IN CONNECTED BATTERIES INDIVIDUAL FOUR FOR PROTECTION OVERCURRENT , 90 W/12 V=7.5, 90 A Load fuse Main . types ese 329

THEME 4.3.1 THEME 4.3.1 330 In addition to the battery safety instructions given in Unit following: 3, in consider the given instructions safety battery to the addition In Batteries Maintaining and Handling when Required Precautions long-term inactivity. during cycling prevents and at 100 %readiness batteries maintains 1ampere. technology than charging ethree-step di potential aregulated the via 13.4 of less erence of around voltacurrent and starts step oat charging %charged. 98 is battery the until en declines 14.4 current at aconstant kept voltthe is ‘voltage’ and the of charging type this With begins. let’s 14.4 say charging potential, volt, absorption acertain reaches battery the charger. When of the rating current and ‘voltage’ maximum at the charger by the replaced technique. common is capacity energy e battery %of where upthe to 80 charging bulk is step rst a is chargers smart special with charging regulated three-step longevity. Nowadays, and performance maximum ensures charging appropriate battery and Regular models. cycle deep the especially batteries, AGM most and SLA all for example technologies, charging special require types battery Most modern Charging Batteries (Vaseline). jelly or petroleum grease temperature of high amount To asmall use batteries. connectors, prevent and of corrosion cables to lead-acid harmful are that minerals and forwater chemicals re dissolved carries water domestic as ll distilled Use only charge. to have need their at afull only batteries and regularly checked levels uid lead-acid Serviceable connections. loose and by dirty caused problems are battery Many tightened. and secure connections cable and clean be always should bank abattery in Batteries hazards. or chemical the from electrical possible safe batteries people against your keep enclosures unauthorised protect and for or outdoor indoor suitable application. are and mounted or pole- ground be can they i.e. ese poses, pur- materials. aluminium, for or from other various made steel used be can berglass, containers ese vented enclosures are or boxes containers Battery issues. important are maintenance and storage Battery EnclosureRequirements and Battery Maintenance Effective for acircuit. components to isolate in switch aload-break use frequently. Rather operated to be meant not thus are breakers out Circuit quickly. wear and forcefully very operate mechanisms spring-driven breaker. However, youthe heavy, can reset it trips then When their and circuit problem the x the in once. more than used be it can that advantage the has breaker Acircuit apart. trip breaker’s contacts breaker circuit Amagnetic trips. then breaker circuit Athermal on design. its pending de- oneways, of in two circuit the open i.e. trip, It will rating. its exceeds breaker the through passing acurrent case in acircuit open/interrupt can that device protection amechanical is breaker A circuit Circuit Breakers (xi) (xi) (x) (ix) (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) Last but not least, recycle old batteries. old batteries. recycle but not least, Last attention. medical immediate seek and water eyes, to the exposure running with 15 for atminutes least them ood event water. of the In with thoroughly wash acid, to battery exposure event of accidental the In batteries. the sion, do not short-circuit To of chance batteries. reduce the before connecting proper polarity re or explo- verify Always times. at all tools Use appropriate insulated suProvide for provision cooling. to make bank abattery in batteries between cient space outside. to the vent batteries always ment installations, or enclosure For compart- gases. produce explosive can Batteries area. awell-ventilated in batteries Install ment. environ- astable in batteries install Always temperature. in to changes sensitive are Batteries identical. are batteries all to ensure date and fortype age, label battery each Check batteries. old orNever untested use Use proper batteries. li with working when techniques ing batteries. Wear appropriate with PPE working when batteries. around you have working when someone near Never Always work alone. generates a magnetic the amagnetic generates that so increases, current the eld as heats up when the current draw exceeds its rating and and rating its exceeds draw current up the when heats Common Causes of Battery FailureCommon (Fault Causes Battery of Finding) periods of non-use all account for approximately 85% of battery failures. 85% for account approximately of battery of non-use all periods or prolonged water, of temperatures, domestic use excessive 100 Ah, strati than larger batteries in cation electrolyte under/overcharging, loss, electrolyte from sulfation i.e. of preventive maintenance, Lack of batteries: type deep-cycle stationary for and lead-acid list failure following the Consider operation. during material active shed plates their as replacement, need and o time at in some point main the fail being will However,enders. batteries all sulfation and loss water below with listed by one or more failures caused of are the failures Most wet-cell (viii) (vii) (vi) (v) (iv) (iii) (ii) (i) Further InformationFurther on R the esource CD (v) (v) (iv) (iii) (ii) (i) Fast recharging rates recharging Fast temperatures due to high or corrosion growth Positive grid sulfation calcium water,Use for of example domestic causing temperatures or high Freezing plate shedding positive i.e. Age, Undercharging sulfation Lead due to heat or overcharging of electrolyte Loss Datasheet GEL and AGM Batteries, Vitron, pdf. Vitron, AGM and GEL Batteries, Datasheet Megger, Testing Guide, pdf. Battery Paper, POWERTHRU White pdf. About e Truth Batteries, pdf. ABB, applications, current for direct Circuit-breakers Schneider, pdf. currents, Short-circuit characteristics, system distribution DC 331

THEME 4.3.1 Your own notes NOTES

332

Skills for Green Jobs (S4GJ)

Department of Higher Education and Training (DHET)