ELECTRO-MECHANICAL BATTERIES - FUTURE SCOPING AND APPLICATIONS

MINI PROJECT 2015

EPSRC Centre for Doctoral Training in Energy Storage and its Applications MINI PROJECT 2015

Mini Project 2015

DATE AUTHOR 16 April 2015 Thomas Bryden

Thomas Bryden PhD Research Student Centre for Doctoral Training in Energy Storage and its Applications Faculty of Engineering and the Environment University of Southampton Highfield Campus Southampton SO17 1BJ UK

Email: [email protected]

Page 1 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications MINI PROJECT 2015

1 Contents

Mini Project 2015 ______1 2 Executive Summary ______4 3 Introduction ______5 4 Component Details ______6 4.1 Rotor ______7 4.1.1 Strength ______7 4.1.2 Vibration ______9 4.2 Bearing design ______9 4.3 Enclosure design ______11 4.4 Motor/generator design ______13 5 Commercial Applications ______15 5.1 Transport applications ______16 5.1.1 Purely mechanical systems ______16 5.1.2 GKN Hybrid Power ______17 5.2 Grid connected applications ______17 5.2.1 Uninterruptable Power Supply ______18 5.2.1.1 Active Power ______18 5.2.2 National grid frequency regulation ______19 5.2.2.1 Beacon Power ______20 5.2.2.2 Temporal Power ______21 5.2.3 Isolated grid renewable penetration and frequency regulation ______21 5.2.3.1 ABB______21 5.2.4 Fusion research ______23 6 Current Research ______24 6.1 Current research projects ______24 6.1.1 NASA research______24 6.1.2 Boeing research ______25 6.2 Individual component research ______26

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6.2.1 Rotor ______26 6.2.2 Bearings ______27 6.2.3 Enclosure ______27 6.2.4 Motor/generator ______28 7 Design Study ______29 7.1 Tesla Model S car ______29 7.2 Boeing 702HP satellite platform ______30 7.3 JR EAST Series 400 electric train ______31 8 Conclusions ______32 9 References ______33 Appendix A ______38 Appendix B ______39 Appendix C ______40 Appendix D ______47 Appendix E ______49 Appendix F ______51

Page 3 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications EXECUTIVE SUMMARY

2 Executive Summary

A detailed review of Electro-Mechanical Batteries (EMBs) is conducted. Future improvements that have the potential to overcome some of the EMB negative characteristics, namely low specific energy, high self discharge rates and high capital costs, are examined.

The specific energy of an EMB is limited by the maximum tensile strength of the material chosen and so will increase as new stronger, lighter materials are discovered. The self discharge rate of an EMB is currently limited by the bearings and so may be decreased as superconducting bearings are used, Boeing is currently working on an EMB that will lose only 0.9% of its stored energy per hour. The high capital cost is mainly due to the use of expensive materials and the precision manufacturing techniques required.

Initially all the components of an EMB are described and the specification limits determined, seen in Table 1.

Table 1 - EMB specification limits

SPECIFICATION COMPONENT LIMITS Mass: = (Section 4.1.1) Specific Energy Rotor material Volume: = (Section 4.1.1) Specific Power Motor/generator Power rating of motor/generator and control system Active magnetic bearing losses: Ohmic, Eddy current losses, Bearing hysteresis, power for power controller Efficiency Enclosure Proportional to Pressure^3 and Rotational Velocity^2 AC Permanent magnet motor/generator losses: Ohmic, Eddy Motor/generator current losses, hysteresis, power for power controller

Current commercial applications are then reviewed. Commercially, EMBs are available for transport applications and grid connected applications. Grid connected applications include Uninterruptable Power Supply (UPS), National grid frequency regulation, Isolated grid renewable penetration and frequency regulation and Fusion research. A table, Table 3, is created comparing the specific energy of a selection of commercially available EMBs.

Current EMB research is then described, including projects at NASA and Boeing as well as detailing research on each of the EMB individual components. The Boeing research project is particularly interesting as superconducting bearings are being used to achieve low self discharge rates. The author also suggests a method using magnetic coupling to enable multiple EMBs to be powered from one motor/generator.

Finally a brief design study is conducted to determine the sizes of EMBs required for various applications. It is stated that an EMB currently could not be used to power a car. For a satellite application it is found that current commercially available EMBs are too heavy however if an EMB was designed specifically for the satellite it may be feasible. For a train application it is determined that EMBs could be used to reuse some of the energy currently lost during braking.

Page 4 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications INTRODUCTION

3 Introduction

Flywheels have been used to store energy for thousands of years, the earliest known example is the potter’s wheel 1. A flywheel works by storing energy in a rotating mass. Nowadays, flywheels can be attached to a motor/generator to create an EMB for energy storage, technical details of which are discussed in Section 4.

Energy storage is required on a range of scales from small scale storage for handheld devices to large scale storage for national grids. EMBs are currently suitable for transport applications where they are used in regenerative braking systems 2 where their high cycle life makes them very competetive. EMBs are also currently used for frequency regulation on large 3 and small grids 4 where their fast response time enables them to keep the grid frequency within tight tolerance bounds. EMBs are also currently able to provide a few seconds of uninterruptable power supply, which can be used at data centres 5 or on small renewable grids with backup diesel generators.

EMBs are often stated in Energy Storage Technology comparison articles as having the following positive and negative characteristics when compared to other energy storage technologies 6,7,8,9,10 :

• + High specific power • + Long cycle life • + Fast response time • + No toxic components • - Low energy density • - High self discharge • - High capital costs From the Ragone plot in Figure 1 it can be seen that flywheels are in the top left compared to other energy storage technologies, indicating they have high specific power but low specific energy.

Figure 1 - Typical Ragone plot for a selection of energy storage technologies 11

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4 Component Details

All EMBs consist of the following components, the simplest and most common configuration of these components can be seen in Figure 2:

• Rotor • Bearings • Static • Rotating • Enclosure • Motor/Generator • Stator • Rotor • Control system

Figure 2 - Simplest and most common configuration of EMB components The rotor, motor/generator rotor and rotating section of the magnetic bearings are all rigidly connected together and spin at the same angular velocity. The control system is not shown in Figure 2, the control system provides electricity to and from the motor/generator. The design considerations for each of the 4 components listed above are discussed in the following sections. The influence each of the components has on the specification of the battery such as total efficiency, specific energy and specific power is described.

The energy stored in an EMB is found using Equation 1 and is discussed in Section 4.1.

1 = 2 Equation 1 Where:

• E = Energy stored in EMB (J) • I = Moment of inertia of all rotating parts (kg.m 2) • ω = Angular velocity of rotating parts (rad.s -1)

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The power obtained from an EMB depends on the motor/generator specifications and is discussed in Section 4.4.

An EMB has three energy loss mechanisms, which determine the overall efficiency, each loss mechanism is discussed in the indicated section 12 :

• Losses in bearings, section 4.2; • Windage, section 4.3; • Losses in motor/generator and control system, section 4.4;

4.1 ROTOR The rotor can be designed using various materials and shapes. The rotor is designed with two failure mechanisms in mind:

• Strength; • Vibration. Designs also consider cost, ease of manufacture and manufacturing tolerances.

The rotor has a large impact on the specific energy of the EMB as the rotor is the main energy storage component. Energy is also be stored in the motor/generator rotor and the rotating magnetic bearings however this energy is negligible compared to the rotor.

Typical rotors have a hub made of metal and a rim made of composites, as seen in Figure 3. The majority of energy is stored in the composite rim 13 .

Figure 3 - Typical rotor design with a metal hub and composite rim 14

4.1.1 Strength The design for strength involves ensuring the centrifugal stress does not exceed the maximum tensile stress in order that the rotor does not fly apart 15 . The material chosen must also have adequate toughness to give crack tolerance. Equations showing the stresses in a rotating cylinder can be seen in Appendix A 16 . In reality the EMB rotor will not be a simple shape and Finite Element Analysis would be used to determine the stresses in the rotor.

The maximum theoretical specific energy densities, in terms of mass ( m) and volume ( v) can be seen in Equation 2 and Equation 317 .

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=

Equation 217

=

Equation 317 Where:

• e = Energy stored in EMB per unit mass or volume (Equation 2 - J/kg, Equation 3 - J/m 3); • K = Shape factor; • σ = Maximum tensile strength (Pa); • ρ = Density of material (kg.m 3). The shape factor varies between 0 and 1 depending on the shape of the rotor. Some values for the shape factor can be seen in Figure 417 .

Figure 4 - Various rotor shapes and shape factor values 17 A table showing various materials and their maximum energy densities can be seen in Table 217 .

Table 2 - Characteristics of EMB materials 17

MAX TENSILE SPECIFIC SPECIFIC MATERIAL DENSITY STRENGTH ENERGY (VOL) ENERGY (MASS) kg.m -3 MPa MJ.m -3 kJ.kg -1 Aluminium 2700 500 251 93 Steel 7800 800 399 51 Glass E/Epoxy 2000 1000 500 250 Graphite HM/Epoxy 1580 750 374 237 Graphite HS/Epoxy 1600 1500 752 470

The maximum specific energy (mass) in the table of 470 kJ.kg -1 (130 Wh.kg -1) compares unfavourably to the maximum theoretical value for Lithium-ion batteries of about 400 Wh.kg -1 18 .

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4.1.2 Vibraon The vibration design is undertaken in conjunction with the magnetic bearings. A model, such as that seen in Figure 5 may be created 19 .

Figure 5 - Basic cross section model 19 The vibration design is conducted with the goal of the ensuring the bending mode frequencies do not occur within the rotor operating speeds. Magnetic bearing control becomes significantly more difficult if the bending mode frequencies fall within the rotor operating speed 13 . This is illustrated in Figure 6, where it can be seen that at certain critical speeds (the bending mode frequencies) the unbalance response is greatly increased 19 .

Figure 6 - Example plot of unbalance response at different rotating speeds 19 The speed at which the bending mode frequencies occur can be changed by modifying the rotor shape and mass. Similarly to the design for strength, the EMB rotor will not be simple shape and Finite Element Analysis is normally used to determine the bending mode frequencies.

4.2 BEARING DESIGN As stated the bearing design will be undertaken along with the rotor design to account for vibration. In modern EMB designs the bearings will almost always be magnetic. There are generally three bearing types in an EMB 13 :

• Radial magnetic bearings; • Lift magnetic bearings; • Conventional contact bearings. The radial magnetic bearings ensure that the rotor spins around the rotation axis. These radial magnetic bearings provide the spring stiffness used in the vibration design seen in Section 4.1.2.

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In high speed EMB designs the EMB is orientated so that it is rotating around a vertical axis 20 . The weight of the rotor due to gravity must therefore be supported. This support is provided by a magnetic lift bearing.

Conventional bearings, known as touchdown bearings, are required to support the rotor when the EMB is not in operation. Conventional bearings may also be used for safety, in the event of a magnetic bearing failure the spinning rotor will be supported by conventional bearings until it has stopped spinning 21 .

There are several magnetic bearing types, however only active magnetic bearings have found applications so far 22 . Active magnetic bearings can provide a high level of load capacity, stiffness, low level of rotational losses, and wide temperature operation range 22 . Active magnetic bearings however require continuous external energy consumption and requirement of complicated feedback control systems. “Active” means a feedback control system is required, while “passive” magnetic bearings do not require feedback.

The basic operation of an active magnetic bearing is shown in Figure 723 . A ferrous object is known to be attracted to an electromagnet, the force is always attractive, it cannot be repulsive. The position of the shaft is measured using a sensor and the current applied to the electromagnet is varied to keep the shaft in the correct location. For most applications including EMBs, there will be more than one electromagnet.

Figure 7 - Active magnetic bearings operation 23

Magnetic bearings account for significant efficiency losses in EMBs, losses arise from 24 :

• Stationary parts: • Ohmic losses; • Rotating parts: • Iron losses: • Eddy current losses; • Hysteresis losses; • Windage. All of these losses, apart from windage, are functions of the electrical current in the electromagnet 25 . Therefore, minimization of the current has a significant effect on the overall energy efficiency of magnetic bearings. Active magnetic bearings also require a position sensor, controller and power amplifier, seen in Figure 7, the power required by these components also lower the efficiency of the EMB.

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The stationary ohmic losses, or copper loss, occur as heat is produced in the electromagnet windings 26 . The heat is produced as current ( I) passes through the copper wire, which has a resistance (R), the power losses are equal to I2R.

In the rotating section the main losses generally arise from eddy currents 27 , the eddy current losses are proportional to the rotating speed squared while the hysteresis losses are proportional the rotating speed 24 . Windage losses are not discussed in this section, see Section 4.3.

Eddy current loss results in the radial magnetic force exerted on a rotor by an active magnetic bearing becoming weaker when the rotor spins at a sufficiently high speed. This is because the rotor, typically made of conductive soft-magnetic material, has induced eddy currents when spinning in the non-uniform magnetic field needed to induce a radial force 23 . Eddy current losses can be significantly reduced by lamination, seen in Figure 8. The eddy current loss is approximately proportional to the square of the thickness of the laminations 28 . The lamination thickness is determined by the cost of manufacture.

Figure 8 - Eddy currents in a non laminated rotor (left) and laminated rotor (right) 28 Hysteresis loss occurs when a material is repeatedly magnetised and demagnetised. If the magnetic field applied to a magnetic material is increased and then decreased back to its original value, the magnetic field inside the material does not return to its original value. The internal field 'lags' behind the external field. This behaviour results in a loss of energy 29 .

4.3 ENCLOSURE DESIGN The enclosure has three functions:

• To provide containment; • To maintain pressure; • To transfer heat. The containment issue will likely determine the wall thickness of the enclosure. The enclosure must be built strong enough to withstand failure of the EMB resulting in the rotor flying apart.

Windage losses occur as a result of friction between the air in the enclosure and the rotor rotating at high speed. Windage can result in severe reductions in efficiency of the EMB. Several models exist to determine EMB windage losses in non vacuum environments 30 . Modern EMBs however generally operate in as close to a vacuum environment as possible. It has been suggested that the power losses associated with windage are proportional to the vacuum pressure (a) cubed (vacuum pressure is measured in torr) and the angular velocity (ω) squared 13 , as seen in Equation 4 and Figure 9.

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= 2/ 2//1 2/

Equation 413

Figure 9 - Windage loss model, the EMB capacity in this case is 525 Whr 13 As can be seen in Figure 9 it is possible to have minimal windage losses if the vacuum is low enough pressure. In this example if the windage loss is 1W (for a spin rate of 60000 RPM and a vacuum of <1.E-03 mTorr), this equates to efficiency losses due to windage of 0.19% per hour (1/525).

Once the vacuum has been created, the vacuum quality can degrade via leakage or outgassing. Outgassing is the spontaneous evolution of gas from a solid or liquid 31 . Different materials have different outgassing rates and outgassing can be minimised by selection of materials with low outgassing or by coating the materials. Current EMB designs that operate in near vacuum conditions have a vacuum pump attached to continuously produce the required vacuum.

Heat transfer must be considered during EMB design. Any heat produced by an EMB is wasted energy and so should be avoided where possible. Inside the EMB enclosure heat may be produced through:

• Losses in bearings; • Windage; • Losses in motor/generator. This heat must be dissipated to ensure components do not get too hot. The enclosure however is likely to be a vacuum. In a vacuum heat transfer is not possible through conduction or convection and the only heat transfer occurs as a result of radiation 32 . If it is not possible to transfer all the heat out of the EMB by radiation a cooling system can be used however this should be avoided where possible as the cooling system wastes energy.

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4.4 MOTOR/GENERATOR DESIGN The aims for the motor/generator design include high efficiency, a robust rotor structure, low zero torque spinning losses, and low rotor losses 33 . In an EMB the motor/generator is usually a high-speed permanent magnet machine 8. A permanent magnet motor/generator develops a torque due to the interaction between the stator rotating field and rotor field generated by permanent magnets 34 .

The motor/generator determines the power that can be obtained from the EMB and also the usable speed range. The Power ( P), Torque ( T) and Rotational speed ( ω) are related according to Equation 5. The EMB has a minimum operation speed because, as seen in Equation 5, to obtain large powers at low speeds would require large torques, which a motor/generator may not be able to provide.

=

Equation 5 The efficiency losses that arise from the permanent magnet motor/generator are identical to those for the active magnetic bearings, including ohmic losses, eddy current losses, hyseresis losses and windage losses, these are discussed in Section 4.2.

A control system will always be required but will vary considerably depending on the motor/generator chosen. The details below are for a permanent magnet machine, which as stated above is the most commonly used motor/generator for EMB systems.

The control system typically consists of a variable-speed power electronics converter and a power controller 8, labelled in Figure 10. The converter is usually a bi-directional converter which can be single- stage (ac to dc) or double-stage (ac to dc to ac), depending on the application requirements. A power controller is required to control power system variables.

Figure 10 - Flywheel control system 34 The two inputs to the power controller are the EMB rotational speed and the amount of power to be delivered to or taken from the EMB. The power controller then determines the frequency, voltage and current to apply to the motor/generator. These inputs are created as AC power from the DC bus using pulse width modulation, seen in Figure 11.

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The control system contributes to EMB system efficiency losses as the power controller requires continuous power to operate.

Figure 11 - AC to DC to AC based power electronic converter 35

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5 Commercial Applications

EMBs are currently available commercially for transport and the following grid connected applications:

• Uninterruptable Power Supply (UPS); • National grid frequency regulation; • Isolated grid renewable penetration and frequency regulation; • Fusion research. A summary of a selection of commercially available EMBs can be seen in Table 3, the complete table can be seen in Appendix B.

The specific energy values have been calculated and include a value considering only the mass/volume of the EMB (including the rotor, bearings, enclosure and motor/generator) as well as a value including the mass/volume of the EMB plus the electronics, control and housing components.

The specific energy including electronics, control and housing has been calculated assuming one electronics, control and housing unit operates one EMB. If multiple EMBs are operated from one electronics, control and housing unit the energy density could be greater. The UPS and Isolated grid EMBs have a large difference between the specific energy when including electronics, control and housing and the specific energy of only the EMB. This difference occurs as the UPS and Isolated grid devices have been designed to fit into containers, which are large and have significant weight.

Data could not be found for the mass of the Beacon Power EMBs. The Beacon Power rotor mass however was found to be 1134 kg 36 . Assuming the same mass of rotor to mass of EMB ratio as the ABB PowerStore EMB 37 (6000kg/2900kg), the Beacon Power EMB mass can be estimated as 2350 kg. This mass equates to a specific energy of 15 Wh.kg -1. This specific energy along with the other EMB specific energies listed in Table 3 do not compare favourably with currently available lithium-ion batteries, which can have energy densities of upwards of 250 Wh.kg -1 and 800 kWh.m -3.

Table 3 - Commercially available EMBs 38,2,39,36,40,4,37,41,42

APPLICATION NAME ENERGY POWER SPEED SPECIFIC ENERGY (1) kWh kW rpm Wh.kg -1 kWh.m -3 Torotrak Flybrid (2) 0.11 60 60,000 4.4 / - 8.5 / - Transport GKN Gyrodrive 0.5 120 36,000 8.3 / 5.6 TBC / TBC UPS Active Power HD 2.9 625 7,700 3.8 / 0.59 28 / 0.43 National grid Beacon 450XP 36 360 16,000 TBC / TBC 26 / 12 Isolated grid ABB PowerStore 5 1,500 3,600 0.83 / 0.35 TBC / 0.07 Fusion CCFE 720 400,000 225 0.77 / - TBC / - 1 Calculated - Including only EMB (rotor, bearings, enclosure and motor/generator) / Including EMB + electronics, control and housing. 2 The Flybrid system does not convert the flywheel energy to electricity and so is not technically an EMB.

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5.1 TRANSPORT APPLICATIONS In the UK, the EMB market has emerged from the Formula 1 Kinetic Energy Recovery System (KERS). The Formula 1 KERS system was introduced to the sport in 2009 and has been a mainstay from 2011 43 . Although initially flywheels were used to store the energy, now conventional batteries are used and the Formula 1 system is known as Energy Recovery System (ERS).

The initial KERS system developed was a purely mechanical system. A purely mechanical system is not technically an EMB as the energy is never converted to electrical energy. Power is instead delivered to the flywheel through a shaft. If however the shaft was driven by a motor/generator the system could act as an EMB and so the technology is still relevant to this report. A further KERS system was developed by Williams Hybrid Power.

5.1.1 Purely mechanical systems The first Formula 1 KERS system was the Flybrid system, which is now owned by Torotrak 44 . The original Flybrid system specifications can be seen in Table 4.

Table 4 - Torotrak Flybrid 38

PARAMETER VALUE UNITS Energy 0.11 kWh Power 60 kW Maximum speed range 60,000 rpm Mass 25 kg Volume 0.013 m3 4.4 Wh.kg -1 Specific energy 8.5 kWh.m -3 2.4 kW.kg -1 Specific power 4600 kW.m -3

The flywheel was connected to the transmission of the car on the output side of the gearbox via several fixed ratios, a clutch and a continuously variable transmission 38 . The Flybrid system is designed to be used for road car systems, bus and truck systems, motorsport systems and rail applications.

One disadvantage of the purely mechanical system is that the energy is delivered to the flywheel via a shaft rotating at very high speed. To keep the flywheel enclosure as close to a vacuum as possible high speed seals and a vacuum pump are required. The Ricardo Kinergy system overcomes this problem by transferring torque directly through its containment wall using a magnetic gearing and coupling system 45 . This offers the prospect of enabling the unit to be sealed for life.

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5.1.2 GKN Hybrid Power A second Formula 1 KERS system was developed by Williams Hybrid Power, known as the Gyrodrive system and now owned by GKN Hybrid Power. The system was never used in Formula 1 but is now being installed for transport applications on buses, heavy good vehicles and trucks, motor sport and trains and trams 46 .

The Gyrodrive system is different to the Flybrid system as it operates as an EMB and converts the mechanical energy to electrical energy and then back to mechanical energy for storage in the flywheel 2, seen in Figure 12. The Gyrodrive specifications can be seen in Table 5.

Table 5 - GKN Hybrid Power Gyrodrive 2

PARAMETER VALUE UNITS Energy 0.5 kWh Power 120 kW Operating speed range 18,000-36,000 rpm Only EMB (including rotor, Mass 60 kg bearings, enclosure and Specific energy 8.3 Wh.kg -1 motor/generator) Specific power 2 kW.kg -1 Mass 90 kg EMB + electronics, control and Specific energy 5.6 Wh.kg -1 housing Specific power 1.3 kW.kg -1

Figure 12 - Components of Gyrodrive system (left) and the flywheel energy storage store (right) 2

5.2 GRID CONNECTED APPLICATIONS Grid connected applications can be split into 4 categories:

• UPS; • National grid frequency regulation; • Isolated grid renewable penetration and frequency regulation; • Fusion research. The EMB UPS application has multiple competing companies providing EMB UPS services. National grid frequency regulation using EMBs is provided by Beacon Power and Temporal Power, both located in North America. For isolated grids an EMB system owned by ABB has been installed in multiple locations. EMBs for fusion research are generally constructed as one off designs to meet certain specific requirements.

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A list of EMB grid connected storage compiled from data from the US Department of Energy 47 is listed in Appendix C, UPS applications have not been included in this list.

5.2.1 Uninterruptable Power Supply UPS systems protect IT assets by providing backup power when utility power fails 48 . To provide backup power for multiple minutes either fuel-fired generators or batteries are used 49 , an EMB can be usefully integrated with either system.

In a fuel-fired generator UPS system the fuel-fired generator can come up to full power within 10 seconds, an EMB can therefore be used to provide the backup power during these 10 seconds 49 . The majority of power disturbances for which the UPS system is required last for less than 5 seconds 49 , meaning they could be handled by an EMB. The EMB has the advantage over batteries that frequent discharging and recharging is much more harmful to battery life than EMB life.

Although generally more expensive than batteries in terms of first cost, the longer life, simpler maintenance, and smaller footprint of the EMB systems makes them attractive battery alternatives for UPS systems 49 .

5.2.1.1 Active Power There are currently multiple competing companies providing UPS services, Active Power 5 has been chosen for this report as detailed information can be obtained regarding their EMBs, seen in Figure 13 and Table 6.

Figure 13 - Active Power CleanSource 625HD, flywheel (left) and storage unit containing flywheel (right) 39 For 99% of the Active Power EMB operating life the motor is running to keep the rotor spinning, about 1kW is required continuously to keep the flywheel spinning 5. When short-term backup power is required, the EMB becomes a generator. The EMB operates in a vacuum at about 0.00002 atmospheres 5.

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Table 6 - Active Power CleanSource 625HD 39

PARAMETER VALUE UNITS Energy 2.9 kWh Power 625 kW Maximum speed 7,700 rpm Mass 771 kg Volume 0.10 m3 Only EMB (including rotor, 3.8 Wh.kg -1 bearings, enclosure and Specific energy -3 motor/generator) 28 kWh.m 0.81 kW.kg -1 Specific power 6,000 kW.m-3 Mass 4899 kg Volume 6.8 m3 EMB + electronics, control and 0.59 Wh.kg -1 Specific energy housing 0.43 kWh.m-3 0.13 kW.kg -1 Specific power 93 kW.m-3

5.2.2 Naonal grid frequency regulaon EMBs on a national grid scale are currently used for frequency regulation 50 . Frequency regulation is the process of keeping the grid frequency within tight tolerance bounds 51 . This is accomplished by the ramping up or down of the generation assets. Ramping up or down of generation assets however generally takes minutes rather than seconds and so the electricity supply is always lagging behind the demand, as seen in Figure 14. EMBs can respond in seconds and so can be used to ensure the electricity supply curve follows the demand curve closely, this ensures that the grid frequency is kept within tight tolerance bounds. Companies that offer frequency regulation on a National grid scale are Beacon Power and Temporal Power.

Figure 14 - Typical generation and load regulation 52

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5.2.2.1 Beacon Power From the list in Appendix C, by far the largest EMB sites in terms of energy capacity, not including fusion research, are owned by Beacon Power. Beacon Power EMBs have been in commercial operation since 2008 and currently there are more than 400 operational flywheels 3. The two largest Beacon Power EMB storage sites are in New York and Pennsylvania, each having 200 EMBs and a power capacity of 20 MW. Beacon Power report that their EMB can complete 175,000 full depth charge and discharge cycles. The Beacon Power EMB can be seen in Figure 15 and details are given in Table 7. The Beacon Power EMBs are modular meaning each EMB has its own power control module and cooling system, also seen in Figure 15.

Table 7 - Beacon Power 450 XP 36,40

PARAMETER VALUE UNITS Energy 36 kWh Power 360 kW Operating speed range 8,000-16,000 rpm Only EMB (including rotor, Volume 1.4 m3 bearings, enclosure and Specific energy 26 kWh.m -3 motor/generator) Specific power 260 kW.m -3 Volume 3 m3 EMB + electronics, control and Specific energy 12 kWh.m -3 housing Specific power 120 kW.m -3

Figure 15 - Beacon Power flywheel (left) and multiple flywheels in module (right) 3 Beacon Power filed for bankruptcy in 2011 53 however the company has since been bought and continues to operate 54 .

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5.2.2.2 Temporal Power Temporal Power offer EMBs for similar applications as Beacon Power however Temporal Power have installed fewer EMBs. Temporal Power EMBs are made of solid steel, seen in Figure 16, some details of the Temporal Power EMB are 55 :

• Power: 500 kW - 1 MW; • Energy stored: 50 kWh; • Design life: >20 years.

Figure 16 - Temporal Power flywheel 55

5.2.3 Isolated grid renewable penetraon and frequency regulaon EMBs can help to perform two functions on isolated grids:

• UPS, similar to that discussed in Section 5.2.1; • Frequency regulation, similar to that discussed in Section 5.2.2. Isolated grids often consist of renewable energy sources with back up diesel generators to provide electricity when the renewable energy goes offline 56 . EMBs can be used in a similar fashion to how they are used for UPS applications, providing power in the time between the renewable power going offline and the diesel generator coming online. If there is no EMB, the diesel generator is kept at minimum operating level to enable quick start up, this mode of operation is very inefficient and therefore wastes diesel.

On isolated grids with renewable energy sources the power quality can be an issue resulting in large grid frequency variations. An EMB on an isolated grid can help to match the electricity supply and demand, which, as discussed in Section 5.2.2, regulates the grid frequency.

5.2.3.1 ABB The ABB PowerStore technology has been installed on many isolated grids, as of May 2013 3,000 kW had been installed and 2,100 kW was under commissioning57 . The ABB PowerStore EMB can be seen in Figure 17 and details are given in Table 8.

The ABB PowerStore has a 3,000kg rotor and is available in three power sizes 4, 500 kW, 1,000 kW or 1,500 kW. The flywheel power losses are stated as 12 kW and the power required to maintain charge is 15 kW. The EMB is designed to be easy to transport and the entire ABB PowerStore comes in either a 20ft or 40ft shipping container.

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Table 8 - ABB PowerStore 1,500 kW PS12 4,37,41

PARAMETER VALUE UNITS Energy 5 kWh Power 1,500 kW Operating speed range 1,800-3,600 rpm Only EMB (including rotor, Mass 6,000 kg bearings, enclosure and Specific energy 0.83 Wh.kg -1 motor/generator) Specific power 0.25 kW.kg -1 Mass 14190 kg Volume 71 m3 EMB + electronics, control and 0.35 Wh.kg -1 Specific energy housing 0.07 kWh.m-3 0.11 kW.kg -1 Specific power 21 kW.m -3

Figure 17 - ABB PowerStore flywheel 37 An example of ABB PowerStore system regulating the frequency on an isolated grid can be seen in Figure 18, the system with PowerStore can be seen to have less frequency variation.

Figure 18 - Frequency variations without (left) and with (right) PowerStore 4

Page 22 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications COMMERCIAL APPLICATIONS

5.2.4 Fusion research The largest single EMBs are at the Culham Centre for Fusion Energy (UK), seen in Figure 19 and Figure 20. During fusion experiments a large amount of power is required to confine a multi-mega-ampere plasma current 42 , the power required is larger than the maximum power that the centre is allowed to take from the national grid. Before each plasma current is required the EMB is charged for 9 minutes. During the 20s that the plasma current is required the EMB is discharged. At the centre there are two EMBs, each providing up to 400 MW to supplement 550 MW taken from the grid 58 , giving a total maximum power of 1.35 GW.

The EMBs at the centre have been in operation since 1983 and have completed over 85,000 cycles 59 . The rotor weighs 774 t and is 10m in diameter 42 . There are also similar, but smaller, examples of EMBs being used for fusion research in the Czech Republic and Germany, seen in Appendix C. Details of the EMBs at Culham can be seen in Table 9.

Figure 19 - Flywheel Generator Construction in 1981 at the Culham Centre for Fusion Energy 60

Table 9 - Culham Centre for Fusion Energy EMB 42

PARAMETER VALUE UNITS Energy 720 kWh Power 400,000 kW Operating speed range 112.5-225 (1) rpm Mass 934,000 kg Specific energy 0.77 Wh.kg -1 Specific power 0.43 kW.kg -1 1 The speed range can be extended down to 67.5 rpm should additional energy be required

Figure 20 - Cross section of the EMB 42

Page 23 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications CURRENT RESEARCH

6 Current Research

Two large non-university EMB research projects are currently being conducted by NASA and Boeing, seen in Section 6.1. Research is also being conducted regarding each component in the EMB, seen in Section 6.2.

6.1 CURRENT RESEARCH PROJECTS NASA has conducted EMB research with the goal of using EMBs for spacecraft. Boeing’s research has focused on using the EMB for grid scale storage. The two EMBs can be seen in Figure 21.

Figure 21 - NASA G2 flywheel module 13 (left), Boeing modular flywheel design 61 (right)

6.1.1 NASA research The NASA Glenn Research Center has been researching flywheel energy storage systems for over 30 years. NASA is currently making investments to transition their experience from space applications to the markets of terrestrial use 62 .

NASA is especially interested in EMBs for space applications as an EMB can provide simultaneous energy storage and attitude control 62 , seen in Figure 22. In this example there are four EMBs, by controlling which EMB power is sent to or taken from the EMBs can be spun at different rates. Momentum conservation means that this can be used to control the orientation of the spacecraft.

Figure 22 - NASA flywheels in attitude control configuration 62

Page 24 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications CURRENT RESEARCH

6.1.2 Boeing research The Boeing EMB research aim is to produce a “Low-Cost, High-Energy Density Flywheel Storage Grid Demonstration”63 . The project uses advanced fibre technology and superconducting bearings. The projected cost is $100/kWh, which compares favourably to Lithium ion batteries, which have a cost of over $500/kWh, however it compares less favourably with pumped hydro storage, which has a cost of less than $23/kWh 20 .

In contrast to the majority of previous EMB research Boeing is attempting to obtain low energy loss with time, as seen in Figure 23. Boeing can accomplish this as they are using superconducting bearings. Superconducting bearings require power for cooling and this is included in all efficiency calculations.

Figure 23 - Energy loss with time of Boeing Flywheel with superconducting bearings 63 Boeing has created a Power Budget for the EMB design, seen in Figure 24. The continuous requirements represent the efficiency losses of the EMB with time and power transfer represents the efficiency losses of the EMB while it is being charged and discharged. For the present design the continuous requirements indicate that the EMB would lose 10.4% of the total energy stored per hour (522 W / 3000 Wh). The future design however has losses of 0.9% per hour (136 W / 15000 Wh). Energy losses of 0.9% per hour would enable the EMB to store energy for daily demand and renewable energy generation variations on the grid.

Page 25 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications CURRENT RESEARCH

Figure 24 - Power budget for Boeings present 5 kWh design (left) and future 15 kWh design (right) 61

6.2 INDIVIDUAL COMPONENT RESEARCH Research is also being conducted on each component detailed in Section 4.

6.2.1 Rotor As seen in Figure 4 and Equation 2 and Equation 3 the shape of the rotor varies the shape factor, which is proportional to the specific energy. Shape factors for thick composite rings are 0.305, the maximum shape factor is 1. Therefore to obtain significant (order of magnitude) increases in Energy stored the shape of the rotor is not so important.

As seen in Equation 2 and Equation 3 the material of the rotor plays a key role in determining the maximum specific energy. Materials currently exist with higher strength and lower density than those listed in Table 2, for example carbon nanotubes, which have energy densities over 1125 Wh.kg -1 64 . New manufacturing methods however would be required to make use of new materials 65 . The graph in Figure 25 shows the potential specific energy of flywheels in the future.

Figure 25 - Energy density of various energy storage technologies 63

Page 26 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications CURRENT RESEARCH

6.2.2 Bearings As stated in Section 4.2, currently only active magnetic bearings have been adopted commercially. There are however several other well-known methods of achieving noncontact suspension using forces of electromagnetic nature 22 :

• Diamagnetic (not superconducting) materials; • Conducting objects interacting with time-varying magnetic fields; • Gyroscopic torques; • Superconducting materials; Of these technologies, currently superconducting materials are the most promising and significant research has been conducted regarding using high temperature superconducting materials for bearings66 . Superconducting bearings do not require a feedback control system, however refrigeration is required to cool the high temperature superconductor. Superconducting bearings also have reduced stiffness, leading to more complicated dynamics 67 .

6.2.3 Enclosure Creating the vacuum is not currently a limiting factor in EMB design. Industrial vacuum processes can create vacuums up to 7.5 x 10 ^-11 torr 68 . For the NASA G2 flywheel module 13 , a turbo molecular vacuum pump was used to create a vacuum of 10 -6 torr, the anticipated windage losses from this vacuum were less than 1W, this loss is small as the EMB capacity was 525 W.hr.

The NASA EMB was rotating at 60,000 rpm. In the future, if stronger lightweight materials are used the EMB will have to rotate faster and so the vacuum may become more critical.

One issue is that in current flywheel designs a vacuum pump is continuously required to maintain the vacuum 61 , as seen in Boeing’s power budget in Figure 24. The POWER THRU EMB, seen in Figure 26, uses a molecular vacuum sleeve on the EMB shaft 69 . The shaft speed, combined with the sleeve's helical grooves, maintains the system's high vacuum without a vacuum pump. It should be noted however that compared to other modern EMBs the POWER THRU vacuum is not particularly high, only 5x10 -3 torr.

Figure 26 - POWER THRU EMB with molecular vacuum sleeve 69

Page 27 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications CURRENT RESEARCH

6.2.4 Motor/generator The motor/generator chosen for the EMB depends on the application, trade offs include price, power, efficiency and idle losses.

For applications that require low idle losses the standard motor/generator choice (permanent magnet ac synchronous machine) may not be as suitable as the motor has idle losses 70 . In practice however it may be simpler to disconnect the motor/generator from the rotor while the flywheel is in idle mode.

Research has also been conducted into high speed motor/generators and it has been suggested that motor/generators could be designed to spin up to 300,000 rpm 71 .

In Section 5.1.1 it was noted that Ricardo had developed a magnetic coupling system to enable their purely mechanical system to be sealed for life. This magnetic coupling system could be used in EMBs, this would enable the motor/generator to be in a separate enclosure to the main rotor, seen in Figure 27.

An advantage of this system would be that only one motor/generator would be required for multiple EMBs. Current EMB applications require the EMB to constantly either be charging or discharging, however in the future, if projects such as Boeing’s research project seen in Section 6.1.2 are successful EMBs may be used for storing energy for longer time periods. In this case there would be a time period where the EMB is not charging or discharging when a motor/generator would not be required.

A further advantage of this configuration for long time period storage is that having the motor/generator separate eliminates the motor/generator idle losses.

Figure 27 - EMB with magnetic coupling system

Page 28 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications DESIGN STUDY

7 Design Study

A design study was conducted to use EMBs for the following applications:

• Replace the battery in the Tesla Model S car; • Replace the battery in the Boeing 702HP platform, a commercial geostationary telecoms satellite; • Provide storage for regenerative braking on the JR EAST Series 400 electric train. Basic calculations have been conducted in each case and reasons why an EMB would or would not be suitable for the application are discussed.

7.1 TESLA MODEL S CAR Currently an EMB or multiple EMBs would not be able to replace the battery in the Tesla Model S car, seen in Figure 28.

Figure 28 - Tesla Model S 72 (left) and the battery pack 73 (right)

A calculation to determine the theoretical size of the required EMB 74,72,75 , seen in Appendix D, found the EMB would need to be 0.28 m3 and weigh 450 kg, when using Graphite HS/Epoxy, seen in Table 2. These values compare unfavourably to the current Tesla Model S Battery, which is 0.13 m 3 and weighs 340 kg. The EMB volume and mass calculated are theoretical and do not include the motor/generator, which will increase the mass and volume even further. The EMB mass and volume would be further increased as safety concerns would require a large enclosure.

A car battery is also required to store energy for multiple hours and no EMBs are currently able to store energy for this length of time.

In the future, as stronger lighter materials are discovered, EMBs may be able to provide the required energy density. Research is also being conducted to reduce the EMB energy loss with time. If it became possible to use an EMB in a car, advantages would include no capacity degradation with time, which is currently a problem with electric vehicles 76 , and less environmental impact during the life cycle of the battery.

Page 29 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications DESIGN STUDY

7.2 BOEING 702HP SATELLITE PLATFORM A geostationary telecoms satellite is a more suitable application for an EMB than a car, less energy is needed to be stored, there is more space and the energy only needs to be stored for a maximum of 72 minutes (the eclipse duration during equinoxes) 77 . As described in Section 6.1.1 an advantage of using an EMB in space applications is that the EMB can also perform the attitude control of the spacecraft. As seen in Figure 22 NASA suggested using four EMBs for this purpose.

The maximum power requirement of a Boeing 702HP platform, seen in Figure 29, is 18kW 78 . Therefore the capacity of the battery must be 21.6 kWh (18*72/60). The energy capacity of each of the 4 EMBs must therefore be 5.4 kWh. To make the design more realistic an EMB that can currently be obtained is used for the design. The Active Power CleanSource 625HD Series for UPS applications, seen in Section 5.2.1.1, is chosen as when comparing this EMB to other commercially available EMBs the Active Power EMB has a capacity (2.9 kWh) close to that required and a comparatively good specific energy, seen in Table 3.

Figure 29 - Boeing’s 702HP Satellite Platform 79 Using a similar method to Section 7.1, a calculation was conducted, seen in Appendix E, and it was determined that each EMB would need to be 0.24 m3 and weigh 1700 kg, giving total values for all 4 EMBs of 0.94 m3 and 6900 kg. This compares to the current total stowed volume of the Boeing 702HP of 86.6 m3 and launch mass of up to 5900 kg. The mass of the EMB is therefore currently an issue. The Active Power EMB chosen does not spin at particularly high speeds (7,700rpm), however the EMBs currently available that spin at higher speeds are much smaller and have smaller energy capacities. The theoretical mass, using currently available materials, seen in Table 2, of a 21.6 kWh EMB is 46 kg. In the future, as larger EMBs are built to spin at high speeds an EMB may be suitable for satellites. Some notes on the calculation include:

• Spinning losses are accounted for, it is stated in Section 5.2.1.1 that 1kW is required to keep the Active Power EMB spinning, the capacity of each EMB has been calculated as 6.6 kWh (5.4+1*72/60); • It is assumed the Active Power EMB could be increased from 2.9 to 6.6 kWh without efficiency losses; • It is assumed that charging and discharging of the EMB is 100% efficient; • Not included in the calculation is the electronics control system. EMBs have the disadvantage that an inverter is required because the motor uses AC power and the satellite electronics will use DC power. EMBs once again have the advantage that the energy capacity does not degrade with time. Currently conventional batteries on satellites are oversized to ensure that at the end of the lifetime there is still enough battery capacity. This advantage, along with the possibility of using EMBs for satellite attitude control mean that there is the possibility that EMBs could be made for spacecraft with less mass and volume than conventional batteries in the future.

Page 30 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications DESIGN STUDY

7.3 JR EAST SERIES 400 ELECTRIC TRAIN Trains are currently a target market for EMB companies in the transport industry. Both the Flybrid system and the Gyrodrive EMB, described in Section 5.1, state trains as an application of the technology.

A calculation 80,81 , seen in Appendix E, shows that an EMB placed in a JR EAST Series 400 train carriage would need to store 1.5 kWh and be able to supply 120 kW. This calculation assumes that 5% of the train kinetic energy is recovered through the regenerative braking 82 .

Figure 30 - JR East 400 Series A commercially available EMB, such as the GKN Hybrid Power Gyrodrive, could be used on the JR EAST train. The Gyrodrive system can store 0.5 kWh of energy and can deliver 120 kW of power. Therefore, to meet the energy requirement, 3 of these Gyrodrive EMBs could be placed in each train carriage. The Gyrodrive system weighs 90kg and so the total weight of 270 kg is only a small fraction of each carriage weight of 50,000 kg 80 .

From the JR EAST website 83 rough assumptions are made that a train makes a stop every 15 minutes and operates for 14 hours per day, therefore the EMB might be used 56 times per day. This equates to saving 84 kWh per day per carriage.

An EMB is well suited to a train because of the high cycle life. 56 charge/discharge cycles per day equates to 20,000 charge/discharge cycles per year, assuming the train is operating every day. A conventional battery would significantly degrade within the first few years of operation while an EMB would not.

The decision whether to install an EMB on a train would most likely be an economic one. 84 kWh per day per carriage is only worth about £8.40 per day or about £3,000 per year per carriage. The payback period would be calculated based on this saving and the initial cost of the EMB. The installation of a generator on the train driveshaft would also have to be completed, which may require significant reengineering of the train carriage and may not be practical.

Page 31 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications CONCLUSIONS

8 Conclusions

A detailed review of EMBs has been conducted and the limitations of EMB specifications discussed.

The theoretical specific energy of an EMB is determined by material stresses. As stronger, lighter weight materials are discovered it is likely that the specific energy of EMBs will increase, however this will also require increases in angular velocity. Currently, EMBs have significantly less specific energy than other energy storage technologies.

The power supplied by the EMB is limited by the motor/generator and is currently very high compared to other energy storage technologies.

Current EMBs all have very high rates of self discharge compared to other energy storage technologies. There is however no theoretical reason for these high rates of self discharge. Advances in bearing technology, possibly using superconductors, is likely to dramatically reduce these self discharge rates. If these self discharge rates are reduced new applications, such as grid load levelling, will be a possibility for EMBs.

A further issue with EMBs is the high cost. Expensive advanced composite materials, which also require complex manufacturing techniques, are required to make high specific energy EMBs.

EMBs will always have the advantages over other energy storage technologies of long cycle lives and high specific powers. Also the lack of toxic materials in an EMB mean that they have less negative environmental impact than other energy storage technologies. If the issues, specific energy, self discharge and cost, are overcome then EMBs will become a serious competitor to other energy storage technologies in a variety of applications.

Figure 31 - One of the largest EMB sites in the world in Stephentown, New York by Beacon Power 3

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9 References

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53 Hals, T. and Rampton, R. (2011) Beacon Power bankrupt; had U.S. backing like Solyndra . Reuters [Online] Available from: http://uk.reuters.com/article/2011/10/31/us-beaconpower-bankruptcy- idUSTRE79T39320111031. [Accessed: 23 March 2015]. 54 Reuters. (2015) UPDATE 1-Beacon Power finds buyer, Energy Dept sees return . [Online] Available from: http://www.reuters.com/article/2012/02/06/beacon-idUSL2E8D6G5620120206. [Accessed: 23 March 2015]. 55 Temporal Power. (2012) Temporal Power. [Online] Available from: http://temporalpower.com/. [Accessed: 23 March 2015]. 56 Hamsic, N. et al. (2007) Increasing Renewable Energy Penetration in Isolated Grids Using a Flywheel Energy Storage System. International Conference on Power Engineering, Energy and Electric Drives (POWERENG) . 57 Duarte, T. (2013) Grid Stabilisation through ABB . ABB. [Online] Available from: http://www02.abb.com/global/zaabb/zaabb011.nsf/bf177942f19f4a98c1257148003b7a0a/c55b882b3b d48fcbc1257b72003caf51/$file/grid+stabilisation+through+abb.pdf. [Accessed: 12 March 2015]. 58 Culham Centre for Fusion Energy. (2015) IET Power Academy: Roles . [Online] Available from: http://www.ccfe.ac.uk/power_academy_roles.aspx. [Accessed: 12 March 2015]. 59 Rendell, D. et al. (2014) Thirty Year Operational Experience of the JET Flywheel Generators . EFDA JET. 60 EUROfusion. (2013) Power supply . [Online] Available from: https://www.euro-fusion.org/fusion/jet- tech/jets-flywheels/. [Accessed: 24 March 2015]. 61 Strasik, M. et al. (2010) An overview of Boeing flywheel energy storage systems with high-temperature superconducting bearings. Supercond. Sci. Technol. 23. 62 NASA Glenn Research Center. Flywheel Program . [Online] Available from: http://www.grc.nasa.gov/WWW/portal/pdf/flywheel.pdf. [Accessed: 25 March 2015]. 63 Roe, G. (2012) Boeing Flywheel Energy Storage Technology . Boeing. [Online] Available from: https://www.uaf.edu/files/acep/BoeingFlywheelOverview_06_20_2012.pdf. [Accessed: 25 March 2015]. 64 Zhang, R. et al. (2011) Superstrong Ultralong Carbon Nanotubes for Mechanical Energy Storage. Advanced Materials . 23 (30). p.3389-3391. 65 Brauer, S. Critical National Need: Advanced Composites for Flywheels . Nanotech Plus, LLC. [Online] Available from: http://www.nist.gov/tip/wp/pswp/upload/187_advanced_composites_for_flywheels.pdf. [Accessed: 23 March 2015]. 66 Hull, J. R. (2000) Topical Review Superconducting bearings. Supercond. Sci. Technol. . 13. 67 Viznichenko, R. et al. (2008) Advantage of superconducting bearing in a commercial flywheel system. Journal of Physics: Conference Series . 97. 68 Umrath, W. (2007) Fundamentals of Vacuum Technology . Oerlikon Leybold Vacuum. 69 POWER THRU . (2015) Carbon Fiber Flywheel Technology . [Online] Available from: http://www.power- thru.com/carbon_fiber_flywheel_technology.html. [Accessed: 13 March 2015]. 70 Gruber, W. et al. (2014) Comparison of Different Motor-Generator Sets for Long Term Storage Flywheels. International Symposium on Power Electronics, Electrical Drives, Automation and Motion . 71 Wang, W., Hofmann, H. and Bakis, C. E. (2005) Ultrahigh Speed Permanent Magnet Motor/Generator for Aerospace Flywheel Energy Storage Applications. IEEE International Conference on Electric Machines and Drives . p.1494-1500. 72 Tesla. (2015) Model S . [Online] Available from: http://www.teslamotors.com/en_GB/models. [Accessed: 18 March 2015]. 73 Cunningham, W. (2010) Tesla Model S: The battery pack . CNET. [Online] Available from: http://www.cnet.com/news/tesla-model-s-the-battery-pack/. [Accessed: 18 March 2015].

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74 Anderman, M. (2014) The Tesla Battery Report . Advanced Automotive Batteries. [Online] Available from: http://www.advancedautobat.com/industry-reports/2014-Tesla-report/Extract-from-the-Tesla-battery- report.pdf. [Accessed: 18 March 2015]. 75 dpeilow (2015) Long Term Care of Your Tesla Battery: It’s Not Rocket Science (Maybe) . Speak EV. [Online] Available from: https://speakev.com/threads/long-term-care-of-your-tesla-battery-its-not-rocket-science- maybe.6705/. [Accessed: 18 March 2015]. 76 Cobb, J. (2012) Nissan Leaf Owners Hope For The Best, Fear The Worst . hybridCARS. [Online] Available from: http://www.hybridcars.com/nissan-leaf-owners-hope-best-fear-worst-50263/. [Accessed: 18 March 2015]. 77 Maini, A. K. and Agrawal, A. (2014) Satellite Technology: Principles and Applications . 3rd Ed. John Wiley & Sons. 78 Boeing. (2015) 702 Fleet . [Online] Available from: http://www.boeing.com/boeing/defense- space/space/bss/factsheets/702/702fleet.page. [Accessed: 11 March 2015]. 79 MilsatMagazine. (2012) PRIME: Teamwork = WGS-4 Launch Success. [Online] Available from: http://www.milsatmagazine.com/story.php?number=403303969. [Accessed: 11 March 2015]. 80 Ishizuka, M. (2013). Kawasaki’s Approach to US High Speed Rail . Kawasaki heavy Industries, Ltd. [Online] Available from: http://www.apta.com/mc/rail/previous/2013/program/Documents/IshizukaM_Kawasakis-Approach-to- HSR.pdf. [Accessed: 28 March 2015]. 81 World Heritage Encyclopaedia (2015) 400 Series Shinkansen . [Online] Available from: http://ebook2.worldlibrary.net/articles/400_Series_Shinkansen. [Accessed: 28 March 2015]. 82 South West Trains (2012) South West Trains invests £2.2m in regenerative braking system to drive greener trains . [Online] Available from: http://www.southwesttrains.co.uk/Launch-of-regenerative-braking.aspx. [Accessed: 28 March 2015]. 83 JR EAST Japan Railway Company. (2015) JR-EAST Train Reservation . [Online] Available from: http://www.eki-net.com/pc/jreast-shinkansen- reservation/english/wb/common/timetable/e_yamagata_d/02.html. [Accessed: 28 March 2015].

Page 37 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications

Appendix A

• Stresses in a rotating cylinder The radial ( r) and hoop ( H) stresses in a rotating cylinder can be seen in Equation 6 and Equation 7.

= 3 − 8 Equation 6

= 3 − 1 3 8 Equation 7 Where:

• σ = Stress (Pa); • ν = Poisson’s ratio; • ρ = Density of material (kg.m 3) • ω = Angular velocity (rad.s -1); • R = Radius of cylinder (m); • r = Distance from centre of cylinder (m); The equations show how the maximum stress in a rotor is in the centre, seen in Equation 8.

= = 3 8 Equation 8 Longitudinal stress may also need to be considered for longer cylinders.

Reference: Hearn, E. J. (2013) Mechanics of Materials: An Introduction to the Mechanics of Elastic and Plastic Deformation of Solids and Structural Components. 2nd Ed. Elsevier.

Appendix B

• Commercially available EMBs

Only EMB (rotor, bearings, enclosure and motor/generator) EMB + electronics, control and housing

Application Name Min Max Energy Power speed speed Mass Volume Specific energy Specific power Mass Volume Specific energy Specific power Wh. kWh. kW. kW. Wh.k kWh. kW. kW. kWh kW rpm rpm kg m3 kg -1 m-3 kg -1 m-3 kg m3 g-1 m-3 kg -1 m-3 Torotrak 0.11 60 - 60,000 25 0.013 4.4 8.5 2.4 4600 ------[1] Flybrid Transport GKN 0.5 120 18,000 36,000 60 - 8.3 - 2 - 90 - 5.6 - 1.3 - [2] Gyrodrive Active Power UPS 2.9 625 - 7,700 771 0.10 3.8 28 0.81 6000 4899 6.8 0.59 0.43 0.13 93 [3] CleanSource 625HD Beacon National [4], Power 450 36 360 8,000 16,000 - 1.4 - 26 - 260 - 3.0 - 12 - 120 grid [5] XP ABB [6], PowerStore Isolated grid 5 1,500 1,800 3,600 6,000 - 0.83 - 0.25 - 14190 71 0.35 0.07 0.11 21 [7], 1500kW [8] PS12 Fusion CCFE JET 720 400,000 112.5 225 934,000 - 0.77 - 0.43 ------[9]

Calculated value

[1] Flyb rid Automotive Limited. (2014) Original F1 System . [Online] Available from: http://www.flybridsystems.com/F1System.html. [Accessed: 10 March 2015]. [2] GKN Hybrid Power (2015) Gyrodrive by GKN Hybrid Power . [Online] Available from: http://www.gkn.com/land systems/brands/hybrid -power/media/downloads/Brochures/Downloads/GKN - Hybrid-Power-Brochure.pdf. [Accessed: 11 March 2015]. [3] Active Power. (2015) CleanSource 625HD . [Online] Available from: http://www.activepower.com/UKen/cleansource -750hd/. [Accessed: 11 March 2015]. [4] Beacon Power. (2015) Flywheel Energy Storage Systems . [Online] Available from: http://beaconpower.com/wp -content/themes/beaconpower/inc/beacon_power_brochure_081414.pdf. [Accessed: 12 March 2015]. [5] Beacon Power. (2015) Flywheel Ene rgy Storage System . [Online] Available from: http://www.mytopschool.net/mysti2d/activites/polynesie2/ETT/C011/21/StockageEnergie/files/Documents/FESS_Tech_Data_Sheet.pdf. [Accessed: 12 March 2015]. [6] ABB. (2015) PowerStore . [Online] Available from: http://www08.abb.com/global/scot/scot221.nsf/veritydisplay/e13f1d26d87e9167c1257c37002e38bf/$file/9AKK100580A2551_Powerstore_Brochure_EN_HR_%28Dic2013%29.pdf. [Accessed: 12 March 2015]. [7] Bender, D. (2015) Flywheels: An Overview of Applications and Technology . Helix Power Corporation. [Online] Available from: http://www.ewh.ieee.org/r6/san_francisco/pes/pes_pdf/Flywheels.pdf. [Accessed: 12 March 2015] [8] Griffin & Company Logistics. (2015) Container Information . [Online] Available from: http://www.wlgriffi n.com/reference/container_info.pdf. [Accessed: 12 March 2015]. [9] Huart, M. and Sonnerup, L. (1985) JET Flywheel Generators, Proceedings of the Institution of Mechanical Engineers, Part A: Jo urnal of Power and Energy . 200 (2). p.95 -100.

Appendix C

• List of Grid Connected Energy Storage Flywheels (not including UPS) Reference: Deparment of Energy. (2015) DOE Global Energy Storage Database. [Online] Available from: http://www.energystorageexchange.org/. [Accessed: 12 March 2015].

Power Duration Capacity Name Location Status Type Details (kW) (Min) (kWh)

Amber Kinetics is developing a flywheel system from sub-scale research prototype to full-scale mechanical flywheel battery and will conduct both a commercial-scale and a utility-scale demonstration. The goal is to deliver a cost-effective prototype flywheel system that can be grid connected and electrically charged and discharged. The system will have built-in sensing components that can determine frequency and voltage characteristics of the grid and can override the grid signal to manage the amount of electricity discharged. The flywheel stores energy in a spinning rotor that is connected to an electric motor that converts electrical energy into mechanical energy. To recover the energy the motor is electrically reversed and used as a generator to slow Amber Kinetics Fremont, down the flywheel converting the mechanical energy back into electrical energy. Amber Kinetics will Flywheel California, Contracted 10 60 10 Misc improve the traditional flywheel system by engineering breakthroughs in three areas, resulting in link Energy Storage United States higher efficiency and radically reduced cost: magnetic bearings, low-cost rotor, and high-efficiency Demonstration motor generator. This technology can also be used to optimize existing infrastructure. The 48- month project contains 3 phases. Phase 1: engineering of a 10kW/10kWh prototype system, includes demonstration of flywheel system, rotor performance, and demonstration of low-loss bearings and motor (Completed) Phase 2: commercial-scale prototype development, includes 100 kWh flywheel energy storage systems, with focus on scale up and cost reductions Phase 3: grid- connected demonstration, includes MWh size grid-connected demonstration of system performance and cycle life. Interim report available at: http://www.smartgrid.gov/sites/default/files/pdfs/tpr_final_phase1_amber_kinetics.pdf

This 20 MW plant is comprised of 200 Beacon Power Series 400 flywheels that provide frequency Beacon Power regulation services to grid operator PJM Interconnection. Beacon flywheels recycle energy from the 20 MW grid in response to changes in demand and grid frequency. When generated power exceeds load, the Hazle Flywheel flywheels store the excess energy. When load increases, the flywheels return the energy to the grid. Township, Frequency Operational 20,000 15 5000 Beacon The flywheel systems can respond nearly instantaneously to the ISO control signal at a rate that is link Pennsylvania, Regulation Plant 100 times faster than traditional generation resources. The plant can operate at 100% depth of United States (Hazle discharge with no performance degradation over a 20-year lifetime, and can do so for more than

Township, PA) 100,000 full charge/discharge cycles. The flywheels are rated at 0.1 MW and 0.025 MWh, for a plant total of 20.0 MW and 5.0 MWh of frequency response

Beacon Smart Beacon's flywheel energy storage system (FESS) was located at Pacific Gas and Electric’s San San Ramon, Energy Matrix De- Ramon research center. It employed seven 6-kilowatt-hour flywheels, each the size of a small California, 100 15 25 Beacon link FESS, San Commissioned refrigerator, ganged together to form a system that could absorb or discharge 100 kilowatts of power United States Ramon for 15 minutes.

In August 2003, Fuji Electric installed a 200 kW Urenco Power Technology Flywheel adjacent to 1.8 MW of wind turbines. The flywheel helped reduce the fluctuations on the system and allowed the Dogo, diesel engines, which were stabilizing the turbines, to operate at higher efficiency, thereby reducing Dogo Island De- Shimane, 200 n/a n/a Misc the use of diesel fuel. In June 2004, Urenco abandoned the flywheel for power quality market and link Flywheels Commissioned Japan removed all previously installed flywheels. Read the DOE/EPRI 2004 report on ES for Grid Connected Wind Generation Applications: http://www.sandia.gov/ess/publications/EPRI- DOE%20ESHB%20Wind%20Supplement.pdf

Research project of a micro-grid including 170kWp of solar panels, 15kW of wind generation and Toulouse, Smart ZAE high efficiency power conversion systems connected to a DC-bus with an energy storage system Midi Under Flywheel 100 60 100 Misc (battery + flywheels). An Energy Management System drives the ESS in order to minimize energy link Pyrenées, Construction Project costs for the area and use of public AC grid. Flywheels (10kW/10kWh) are developed by LEVISYS France and are magnetically levitated with passive magnets

The project aims to foster the integration of various renewable energy technologies in order to save energy, reduce costs and increase reliability, and in the process open the door to a smart power grid in the region of Gipuzkoa. In its first stage, the i-Sare micro-grid will serve as a test bench for San Sebastián, developing and experimenting with different technologies that will become the future of power grids Micro-Grid I- Under Gipuzkoa, 0 n/a n/a Misc worldwide. The project's other aims are to become a reference for new generations in terms of link Sare (Flywheel) Construction Spain operating this kind of system and increasing awareness about power. At the same time, it will become a laboratory for testing and certifying solutions that are developed by companies in the sector, leading to the creation of new products that will create jobs with high added value in our region. http://www.icrepq.com/icrepq'13/437-arrizubieta.pdf

Coral Bay is the gateway to the Ningaloo Reef World Heritage Area in Northwestern Australia, where power demand increases significantly during the tourist season. A PowerStore grid-stabilizing system and DCS power management solution oversees the town’s power supply, which consists of seven 320 kilowatt (kW) low-load diesel generation units combined with three 200 kW wind turbines. PowerStore’s 500 kW flywheel technology enables the wind turbines to supply up to 95 percent of Coral Bay’s energy supply at times, with a total annual wind penetration of 45 percent, while maintaining city grid standards of power stability and quality. Power station data indicates more than 80 percent of Coral Bay’s power is wind generated for one-third of the year. The data also shows that for nearly 900 hours per year, wind provides more than 90 percent of Coral Bay’s power supply. PowerStore maximizes an environmentally friendly solution.

Coral Bay Coral Bay, The following statement is repeated for all PowerStore projects: PowerStore Western Operational 500 0.6 5 PowerStore The PowerStore is a compact and versatile flywheel-based grid stabilizing generator. Its main link Flywheel Australia, purpose is to stabilize power systems against fluctuations in frequency and voltage. It includes state- Project Australia of-the-art inverters and virtual generator control software. It enables the integration of intermittent and often erratic renewable generation and the higher utilization of renewable energy generators, protecting remote communities from exposure to volatile oil prices. PowerStore safeguards conventional microgrids, and ensures the safe integration of large amounts of wind and solar energy, reducing emissions and dependency on fossil fuels. High-speed software controls the power flow into and out of the flywheel, essentially making it a high inertia electrical shock absorber that can instantly smooth out power fluctuations generated by wind turbines or solar arrays. PowerStore acts like a STATCOM (advanced grid technology that quickly stabilizes voltage and improves power quality) and in addition is capable of rapidly absorbing or injecting real power within an isolated power network. It can stabilize both voltage and frequency, hold 18 MWs (megawatt seconds) of energy and shift from full absorption to full injection in 1 millisecond to stabilize the grid.

The world’s first high penetration, solar photovoltaic diesel power stations were commissioned in 2010 in the towns of Nullagine and Marble Bar, in Western Australia. The projects include more than 2,000 solar modules and a solar tracking system that follows the path of the sun throughout the day. When the sun is shining, PowerStore grid-stabilizing technology and DCS power management Marble Bar Marble Bar, solution ensures maximum solar energy (100% peak penetration) goes into the network by lowering PowerStore Western Operational 500 0.6 5 PowerStore diesel generation, up to the minimum loading of the generation units. When the sun is obscured, the link Flywheel Australia, PowerStore covers the loss of solar power generation as the DCS ramps up the diesel generation, so Project Australia the network has an uninterrupted energy supply. The solar energy systems generate over 1 gigawatt hour (GWh) of renewable energy per year, supplying 60 percent of the average daytime energy for both towns, saving 405,000 liters of fuel and 1,100 metric tons of greenhouse gas emissions each year.

New Zealand’s Scott Base and America’s McMurdo Station in Antarctica are important research bases and home to about 1,200 people in the Antarctic summer. They have always relied completely on fossil fuels for power and heating, until a new system based on wind turbines, a new distributed Antarctica NZ Ross, Ross control system and PowerStore grid-stabilizing technology was commissioned in 2009. The bases ABB Island, Operational 500 0.5 4.2 PowerStore still need back-up diesel generators, but three 333 kilowatt (kW) wind turbines reduce the amount of link PowerStore Antarctica diesel required for power generation by around 463,000 liters, and cut CO2 emissions by 1,242 Flywheel metric tons per year, while lowering the risks of transporting and storing liquid fuel in this precious environment. A frequency converter interconnects the Scott and McMurdo bases, which operate at different frequencies - 50 Hz (NZ) and 60 Hz (US), allowing power flow in both directions.

BHP Billiton’s Leinster nickel mine in Western Australia is the third-largest producer of nickel concentrate in the world. Ore is extracted from 1,000 meters underground with a large, electrically driven winder, which at 8.5 megawatts (MW) of demand shift over 120 seconds is a large cyclic load, Leinster Nickel Leinster, given the unit’s average power consumption is just 2 MW. To upgrade the winder’s power supply, Operation Western De- BHP installed a 1 MW PowerStore system, which reduced the total demand shift to 6.5 MW while 1,000 0.6 10 PowerStore link PowerStore Australia, Commissioned adding 1 MW of spinning reserve to the system. Its flywheel-based energy storage system provides

Flywheel Australia peak lopping and overcomes transient and cyclic loads on grid connected or isolated systems. The mine was able to increase winder production without affecting power system reliability. Fully automated, PowerStore gets power to the winder when it’s needed most, and provides high resolution data of winder performance and local electrical grid disturbances.

Flores (the Azores) Flores, The

PowerStore Azores, Operational 500 0.6 5 PowerStore See repeated statement in Coral Bay PowerStore Flywheel Project link Flywheel Portugal

Project

Graciosa (the Azores) Graciosa, The

PowerStore Azores, Operational 500 0.6 5 PowerStore See repeated statement in Coral Bay PowerStore Flywheel Project link Flywheel Portugal

Project

This facility, which has a budget of 1.2 million euros, will be located next to the 66 kilovolt (kV) Lanzarote Mácher substation, in the municipality of Tías in Lanzarote. The flywheel can inject into or absorb Tias, PowerStore from the grid a maximum power of 1.65 MW for about 12 seconds, providing a total of about 18 Lanzarote, Operational 1,600 0.3 8 PowerStore link Flywheel megawatts per second (MWs) of energy, depending on the programming of the equipment. This will Spain Project also help mitigate the effects of sudden changes in system frequency within pre-established parameters, giving it stability, something that is very important in isolated systems.

Endesa'a STORE project aims to demonstrate the technical and financial viability of large-scale storage systems to improve the reliability and operation of the grid in weak and isolated island networks. It explores operational possibilities for the arbitrage of power, voltage regulation, load leveling and peak shaving, and frequency regulation. Project STORE has three demonstration plants in the Canary Islands: • Lithium-ion battery system, with total installed capacity of 1MW/3MWh • A Playa flywheel with total installed capacity of 0.5MW/18MWs This project's key goal is to increase the Endesa Santiago, La inertia of the insular electricity system and regulate the frequency, thereby increasing the quality of STORE: La Gomera, Operational 500 0.5 4.2 PowerStore link supply and the integration of renewable energy, validating the technical feasibility and efficiency of Gomera Project Canary the technology. • Ultracapacitors with total installed capacity of 4MW/20MWs With a budget of Islands, Spain Euro 11 million, the project is partly financed by The Centre for Industrial Technological Development (CDTI) (a Business Public Entity, answering to the Ministry of Economy and Competitiveness) and the European Union. This ABB Powerstore flywheel provides 0.5 MW/ 18 MWs of storage. It will provide inertia and active power for primary voltage regulation, as well as helping to continuously stabilize voltage on the island.

Norfolk Temporal Power’s flywheel energy storage (FES) technology is currently being deployed by Hydro Clear Creek County, Under One Networks Inc. to provide renewable energy integration support in Ontario, Canada. This 10- Flywheel Wind 5,000 6 500 Temporal link Ontario, Construction flywheel 5MW installation will provide local power quality support, by balancing real and reactive Farm Project Canada power flows from a 20MW wind farm.

NRStor was selected by Ontario's Independent Electricity System Operator (IESO) through a Harriston, NRStor Minto selective RFP process to deliver 2 MW of frequency regulation services to the Ontario electricity Town of Flywheel grid. Temporal Power Ltd. is the flywheel manufacturer and will be supplying the 10-flywheel 2MW Minto, Operational 2,000 15 500 Temporal link Energy Storage facility. Ontario, Project Canada http://www.temporalpower.com

The system will be a 6 MW wayside energy storage system (WESS) type installation when complete. LA Metro The 1st phase is a 2 MW flywheel based energy storage system, consisting of 4 units (500 kW) each Wayside Los Angeles, capable of producing 2.08 kWh of usable energy. The goal is to reduce the transit authority's utility Flywheel California, Operational 2,000 0.3 10 Misc link bill by absorbing regenerative braking energy and delivering it back when the train accelerates away Energy Storage United States from the station. A controller, independent of the WESS, will be utilized to command the WESS to System charge and discharge as required.

Annual consumption is very dependent on whether JET is operational or in shutdown. The peak of Abingdon, consumption here is during a 300s JET pulse – where over 300 megawatts of electrical power is EFDA JET Oxfordshire, pulled from the grid, and up to 400 megawatts is supplied from two large flywheels located in Operational 400,000 0.5 3333.3 Fusion link Fusion Flywheel United Culham, U.K. However, this is only for 30 seconds, every 20-30 minutes. Kingdom http://www.efda.org/faq/new-what-is-the-annual-electricity-consumption-of-the-jet-plant/

The flywheel system was required as an onsite power supply for fusion pulse experiments, which require a high amount of energy that was unavailable on the grid in Prague. The fusion equipment (COMPASS-D tokamak) was previously used in UKAEA, United Kingdom. The equipment Institute of required electrical input power of 50 MW for pulse duration for about 2-3 seconds during operation. Prague, Plasma Physics Such power was accessible in Culham Laboratory directly from the 33kV grid. However, only 1 MW Prague, Czech Operational 70,000 0.1 116.7 Fusion link (IPP) Flywheel power is available from the 22kV grid at the campus of the Academy of Sciences in Prague, where Republic System IPP Prague is located. Therefore, several solutions to provide the necessary input power were considered. Installation of two flywheel generators was chosen as a solution. They provide the necessary power (70 MW, 100 MJ) as well as a reasonable redundancy in case of flywheel system failure.

The facility utilizes three flywheel generator systems for on-site power that is required for high Max Planck energy fusion experiments. The name and technical details of each flywheel is as follows: EZ2, built Institute Garching bei in 1973, has a nominal apparent power of 167 MVA, a power factor of 0.93, a resulting active power ASDEX- München, at nominal values of 155 MW, and a pulse duration of 9.7 sec. EZ3, built in 1977, has a nominal Operational 387,000 0.1 645 Fusion link Upgrade Pulsed Bavaria, apparent power of 144 MVA, a power factor of 0.86, a resulting active power at nominal values of Power Supply Germany 124 MW, and a pulse duration of 4.4 sec. EZ4, built in 1987, has a nominal apparent power of 220

System MVA, a power factor of 0.49, a resulting active power at nominal values of 108 MW, and a pulse duration of 6.7 sec.

HSCL Ansan, Development of rotor system of composite hub and rim, capable of delivering both high power and Composite Hub Gyeonggi-do, Contracted 100 30 50 Misc link high energy. and Rim Korea, South

ABB announced it has received an order to deliver two PowerStore units as part of a microgrids solution to stabilize the power grid and increase renewable energy on Kodiak Island in Alaska. Kodiak ABB ABB’s Microgrids Business in Raleigh, NC, worked closely with Kodiak Electric Association (KEA) PowerStore to develop and deliver the microgrid solution. KEA, a rural electric cooperative which generates and Flywheels for Kodiak, distributes electrical power in Kodiak, Alaska, uses hydro, wind, battery energy storage, and diesel Microgrid Alaska, Contracted 2,000 0.2 6.7 PowerStore link generation sets to produce power for the island. The ABB PowerStore units will provide voltage and Stability and United States frequency support for a new crane to be installed at Kodiak Island’s port facility. They can also Harbor Crane extend the life of the battery systems by up to 6 years, and provide renewables integration by helping Operation to manage the intermittencies from a 9 MW wind farm on the island. Longer battery life will improve sustainability of KEA’s power system.

This Beacon Flywheel Energy Storage System (FESS) is the continuation of the system at the SCE Tehachapi Tehachapi, PG&E San Ramon research center. After successful trials, Beacon swapped the seven 15 kW system De- Beacon Gen 4 California, 100 15 25 Beacon for a one 100 kW system. The project was funded and owned by the California Energy Commission link Commissioned FESS United States (CEC) and the single 100 kW unit is was deployed to the Southern California Edison Tehachapi Windfarm in 2010.

Beacon Power Tyngsboro, 500 kW Massachusetts Located at Beacon Power headquarters, this 0.5 MW Flywheel Energy Storage System (FESS) Operational 500 15 125 Beacon link Flywheel , United supplies frequency regulation services to ISO-NE.

Tyngsboro, MA States

TDX Corporation is the Alaska Native Village Corporation, (ANC) for the Community of St. Paul. TDX financed and built the first and only North American owned and operated high penetration hybrid power plant in Alaska on St. Paul Island. The generation for the high penetration hybrid microgrid system is provided by a 225kW Vestas V27 wind turbine, and two 150kW Volvo diesel generators, along with smart switch technology and a synchronizing condenser. Originally St. Paul TDX St Paul commissioned in 1999, the plant supplies electricity and heat to an industrial/airport facility, and has Island, Island Beacon Contracted 165 n/a n/a Beacon reduced the cost of electricity and heat to 40% of the original diesel based generation cost. Beacon’s link Alaska, Flywheel Demo technology will enable TDX to further improve wind utilization, delivering projected fuel savings of United States up to 30 percent over existing (pre flywheel) consumption levels. This project received sponsorship from the Alaska Energy Authority’s Emerging Energy Technology Fund to demonstrate the flywheel energy storage system’s ability to improve system efficiencies in remote and harsh environments and create a model for use across Alaska’s remote grid community and other island and remote grid systems.

This 20 MW plant comprises 200 Beacon Power Series 400 flywheels that provide frequency regulation services to grid operator NYISO. Beacon flywheels recycle energy from the grid in Beacon Power response to changes in demand and grid frequency. When generated power exceeds load, the 20 MW Stephentown, flywheels store the excess energy. When load increases, the flywheels return the energy to the grid.

Flywheel New York, Operational 20,000 15 5000 Beacon The flywheel systems can respond nearly instantaneously to the ISO control signal at a rate that is link Frequency United States 100 times faster than traditional generation resources. The plant can operate at 100% depth of

Regulation Plant discharge with no performance degradation over a 20-year lifetime, and can do so for more than 100,000 full charge/discharge cycles. The flywheels are rated at 0.1 MW and 0.025 MWh, for a plant total of 20.0 MW and 5.0 MWh of frequency response.

Appendix D

• Tesla Model S EMB Mass and Volume analysis.

EMB Mass and Volume Analysis

Mini Project: El ectro -mechanical Batteries Future Scoping and Project Applications Calculation Tesla Model S Car Author Thomas Bryden Date 18-Mar-15

Objectives Determine the mass and volume of an EMB to replace the Lithium ion batteries in a Tesla Model S Car and compare results with current batteries.

References [1] Tesla. (2015) Model S . [Online] Available from: http://www.teslamotors.com/en_GB/models. [Accessed: 18 March 2015]. [2] dpeilow (2015) Long Term Care of Your Tesla Battery: It’s Not Rocket Science (Maybe) . Speak EV. [Online] Available from: https://speakev.com/threads/long-term-care-of-your-tesla-battery-its-not- rocket-science-maybe.6705/. [Accessed: 18 March 2015]. [3] Peña-Alzola, R., Sebastián, R., Quesada, J. and Colmenar, A. (2011) Review of Flywheel based Energy Storage Systems. Proceedings of the 2011 International Conference on Power Engineering, Energy and Electrical Drives. [4] Anderman, M. (2014) The Tesla Battery Report . Advanced Automotive Batteries. [Online] Available from: http://www.advancedautobat.com/industry-reports/2014-Tesla-report/Extract-from-the- Tesla-battery-report.pdf. [Accessed: 18 March 2015].

Inputs

ET.c 60 kWh Tesla battery capacity [1]

DoD T 97 % Tesla depth of discharge in range mode [2]

-3 EEMB.v 752 MJ.m EMB specific energy (Volume) [3]

-1 EEMB.m 470 kJ.kg EMB specific energy (Mass) [3]

VT.c 0.018 l Tesla volume of 1 cell [4] mT.c 0.048 kg Tesla mass of 1 cell [4] nT.c 7104 - Tesla number of cell [4]

Calculations

ET = E T.c * DoD T 58.2 kWh Available energy from Tesla battery

VEMB = E T / E EMB.v 0.28 m3 Volume of EMB to have same energy mEMB = E T / E EMB.m 446 kg Mass of EMB to have same energy

VT = V T.c * n T.c 0.13 m3 Volume cells in Tesla battery pack mT = m T.c * n T.c 341 kg Mass of cells in Tesla battery pack

Outputs

3 VEMB 0.28 m Volume of EMB to have same energy mEMB 446 kg Mass of EMB to have same energy

VT 0.13 m3 Volume cells in Tesla battery pack mT 341 kg Mass of cells in Tesla battery pack

Appendix E

• Boeing 702 HP Satellite EMB Mass and Volume analysis

EMB Mass and Volume Analysis

Mini Project: Electro -mechanical Batteries Future Scoping and Project Applications Calculation Boeing 702 HP Geostationary Satellite Author Thomas Bryden Date 11-Mar-15

Objectives Determine the mass and volume of an Active Power EMB to replace the Lithium ion batteries in a Boeing 702 HP Geostationary Satellite car and compare results with current Satellite dimensions and weights.

References [1] Boeing. (2015) 702 Fleet . [Online] Available from: http://www.boeing.com/boeing/defense- space/space/bss/factsheets/702/702fleet.page. [Accessed: 11 March 2015]. [2] Maini, A. K. and Agrawal, A. (2014) Satellite Technology: Principles and Applications . 3 rd Ed. John Wiley & Sons. [3] Active Power. (2015) Flywheel Technology . [Online] Available from: http://www.activepower.com/flywheel-technology/. [Accessed: 11 March 2015].

Inputs

PB 18 kW Boeing power requirement [1]

tB 72 mins Boeing time power is required for [2]

nEMB 4 Number of EMBs required

PLoss.EMB 1 kW EMB Spinning loss [3]

EEMB.v 28 kWh.m -3 Specific energy (Volume) of EMB

EEMB.m 3.8 Wh.kg -1 Specific energy (Mass) of EMB

HB 7.5 m Boeing height [1]

WB 3.5 m Boeing width [1]

LB 3.3 m Boeing length [1] mB 5900 kg Boeing mass [1]

Calculations

EB = P B * t B 22 kWh Energy to be stored to power Boeing

EEMB.i = E B / n EMB 5.4 kWh Energy to be stored per EMB

Eloss.EMB = P Loss.EMB * t B 1.2 kWh Spinning losses

EEMB.ind = E EMB.i + E loss.EMB 6.6 kWh Energy required to be stored per EMB

3 VEMB.ind = E EMB.ind / E EMB.v 0.24 m Volume of single EMB mEMB.ind = E EMB.ind / E EMB.m 1737 kg Mass of single EMB

VEMB = V EMB.ind * n EMB 0.94 m3 Volume of EMB to have same energy mEMB = m EMB.ind * n EMB 6947 kg Mass of EMB to have same energy

3 VB = H B * W B * L B 87 m Volume of Boeing

Outputs

3 VEMB 0.94 m Volume of EMB to have same energy mEMB 6947 kg Mass of EMB to have same energy

VT 87 m3 Volume of Boeing mB 5900 kg Mass of Boeing

Appendix F

• JR EAST EMB Mass and Volume analysis

EMB Mass and Volume Analysis

Mini Project: Electro -mechanical Batteries Future S coping and Project Applications Calculation JR EAST Series 400 Electric Train Author Thomas Bryden Date 20-Mar-15

Objectives Determine the energy and power requirements of an EMB for use on a JR EAST Series 400 Electric train.

References

[1] Ishizuka, M. (2013). Kawasaki’s Approach to US High Speed Rail . Kawasaki heavy Industries, Ltd. [Online] Available from: http://www.apta.com/mc/rail/previous/2013/program/Documents/IshizukaM_Kawasakis- Approach-to-HSR.pdf. [Accessed: 20 March 2015]. [2] South West Trains (2012) South West Trains invests £2.2m in regenerative braking system to drive greener trains . [Online] Available from: http://www.southwesttrains.co.uk/Launch-of-regenerative- braking.aspx. [Accessed: 20 March 2015]. [3] World Heritage Encyclopaedia (2015) 400 Series Shinkansen . [Online] Available from: http://ebook2.worldlibrary.net/articles/400_Series_Shinkansen. [Accessed: 20 March 2015].

Inputs

mJR 50 ton JR EAST estimate of mass of 1 train carriage [1]

vJR.ax 240 km/hr JR EAST maximum train speed [1]

eff 5 % Estimate of regenerative braking efficiency [2]

aJR 2.6 km/h/s Deceleration of train [3]

Calculations

EJR.max = 0.5 * m JR * V JR.max 2 31 kWh Energy in 1 train carriage at maximum speed

EEMB = E JR.max * eff 1.5 kWh Energy to be stored in EMB

PJR.max = m JR * a JR * V JR.max 2407 kW Maximum power taken from train

PEMB = P JR.max * eff 120 kW Power to be delivered to EMB

Outputs

EEMB 1.5 kWh Energy to be stored in EMB

PEMB 120 kW Power to be delivered to EMB

EPSRC Centre for Doctoral Training in Energy Storage and its Applications Email: [email protected] Web: www.energystorage-cdt.ac.uk

The University of Sheffield University of Southampton

Department of Chemical & Biological Engineering Faculty of Engineering and the Environment University of Sheffield University of Southampton Robert Hadfield Building Highfield Campus Portobello Street Southampton Sheffield SO17 1BJ S1 4DW UK UK