Comparative Study of Various Hydrogen Production Methods for Vehicles

Home , Solar vehicle

Fahad Suleman

A Thesis Submitted in Partial Fulfillment

of the Requirements for the Degree of Master of Applied Science

Mechanical Engineering

Faculty of Engineering and Applied Science

University of Ontario Institute of Technology

Oshawa, Ontario, Canada

Abstract Hydrogen as an energy carrier is a promising candidate to store green energy and it has a potential to solve various critical energy challenges. Although, hydrogen is a clean energy carrier, the possible negative impacts during its production cannot be disregarded. Therefore life cycle analyses for various scenarios have been investigated in this study.

In this thesis, a comparative environmental assessment is presented for different hydrogen production methods. The methods are categorized on the basis of various energy sources such as renewables and fossil fuel. For the fossil fuel based hydrogen production, steam methane reforming (SMR) of natural gas is studied. Renewable based hydrogen production includes electrolysis using sodium chlorine cycle. Electrolytic hydrogen production is also compared using different cells such as membrane cell, diaphragm cell and mercury cell. Wind and solar based electricity is also used in electrolytic hydrogen production. Furthermore, vehicle cycle is studied on the basis of available literature to compare the hydrogen vehicle with gasoline vehicle.

The investigation uses life cycle assessment (LCA), which is an analytical tool to identify and quantify environmentally critical phases during the life cycle of a system or a product and/or to evaluate and decrease the overall environmental impact of the system or product. The LCA results of the hydrogen production processes indicate that SMR of natural gas has the highest environmental impacts in terms of abiotic depletion, global warming potential, and in other impact categories. The abiotic depletion for SMR is found to be 0.131 kg Sb eq. which is the highest among all methods. The second highest abiotic depletion value comes under electrolysis using mercury cell which is 0.00786 kg Sb eq. However, thermodynamic results suggested that SMR is the efficient method of hydrogen production because the amount of hydrogen energy produced as output in the system is larger than any other method. The energy efficiency of the system in this method is about 76.8% and the exergy efficiency is about 72.4%. In terms of vehicle cycle comparison, it is found that the gasoline vehicle appears to be the largest contributor in energy consumption and GHGs emissions. The energy consumption of gasoline vehicle is three times higher than hydrogen vehicle. Moreover, GHGs emissions of the hydrogen vehicle are 8% of the gasoline vehicle.

Acknowledgements First of all, I would like to thank the almighty Allah, for giving me the knowledge, wisdom, strength and providing me with the resources to acquire education and complete my studies in an effective manner.

I would like to express my sincere gratitude to my supervisor Dr. Ibrahim Dincer and my co-supervisor Dr. Martin Agelin-chaab for their guidance and help that made me overcome all the obstacles that I faced during the current research. I am indebted to them for providing constructive criticism and illuminating views that enabled me to execute the work to the current standard.

Furthermore, I thank my colleagues at UOIT who made an enjoyable working environment to work. I highly appreciate the help and moral support from my friends Farrukh Khalid, Sayantan Ghosh, and Canan Acar for their help and support during the preparation of this thesis. I have greatly benefited from their support and will always remember their contribution.

Last but not least, I would like to express my eternal gratitude to my parents for their endless consistent support, patience, and encouragement throughout my life. My Siblings, specially my elder brothers Subhan Ansari and Usman Toufiq; without their support and motivation I would not have been able to achieve what I have so far in life.

Table of Contents Introduction ...... 1

1.1 Motivation and Objectives ...... 4

1.1.1 Motivation ...... 4

1.1.2 Objectives ...... 4

Literature Review ...... 6

2.1 Methods of Hydrogen Production ...... 8

2.2 Fossil Fuel Hydrogen Production ...... 8

2.3 Renewable Hydrogen Production ...... 11

2.3.1 Solar Based Hydrogen Production ...... 11

2.3.2 Wind Based Hydrogen production ...... 14

2.3.3 Geothermal Based Hydrogen Production ...... 15

2.3.4 Biomass based Hydrogen production ...... 17

2.4 Nuclear Based Hydrogen Production ...... 18

2.5 Life Cycle Assessment ...... 19

Background ...... 22

3.1 Hydrogen Production Methods ...... 22

3.1.1 Natural Gas Steam Reforming ...... 22

3.1.2 Coal Gasification ...... 23

3.1.3 Partial Oxidation ...... 24

3.1.4 Electrolysis ...... 25

3.1.5 Thermochemical Water Splitting ...... 26

3.2 Life Cycle Assessment Methodology ...... 27

3.2 LCA and International Standard Organization ...... 29

3.4 Impact Assessment ...... 29

iii

3.4.1 Category Definition ...... 31

3.4.2 Characterization ...... 31

3.4.3 Normalization ...... 31

3.4.4 Weighting ...... 31

3.5 Advantages of LCA ...... 32

Systems Studied ...... 33

4.1 Hydrogen Production from Steam Methane Reforming ...... 37

4.2 Hydrogen Production via Chlorine Electrolysis Using Different Cells ...... 38

4.2.1 Mercury Cell Electrolysis ...... 38

4.2.2 Diaphragm Cell Electrolysis ...... 39

4.2.3 Membrane Cell Electrolysis ...... 40

4.3 Hydrogen Production via Wind Based Electricity ...... 41

4.4 Hydrogen Production via Solar Photovoltaic Based Electricity ...... 42

Analyses ...... 44

5.1 Environmental Impacts Assessment using LCA ...... 44

5.1.1 Emissions ...... 45

5.1.3 Resource Depletion ...... 46

5.2 Analysis of Hydrogen Production via Steam Methane Reforming...... 47

5.2.1 Energy and Exergy Efficiencies ...... 48

5.3 Analyses of Hydrogen Production Methods through Electrolysis Using Different Cell ...... 50

5.4 Analyses of Hydrogen Production through Electrolysis Using Wind Electricity ... 51

5.4.1 Energy and Exergy Efficiencies ...... 52

5.5 Analyses of Hydrogen Production through Electrolysis Using Solar Photovoltaic Electricity ...... 55

5.5.1 Energy and Exergy Efficiencies ...... 55

Results and Discussion ...... 57

6.1 Hydrogen via Steam Methane Reforming ...... 57

6.1.1 Impact Assessment Results ...... 57

6.1.2 Energy and Exergy Efficiencies ...... 64

6.2 Hydrogen from Chlorine Electrolysis Using Different Cells...... 68

6.2.1 Impact Assessment Results ...... 68

6.3 Hydrogen via Electrolysis Using Wind Electricity ...... 77

6.3.1 Impact Assessment Results ...... 77

6.3.2 Energy and Exergy Efficiencies ...... 85

6.4 Hydrogen via Electrolysis Using Solar Photovoltaic Electricity ...... 88

6.4.1 Impact Assessment Results ...... 88

6.4.2 Energy and Exergy Efficiencies ...... 97

6.5 Comparison of Various Options by CML-Method with Uncertainty Analyses ..... 98

6.5.1 Abiotic Depletion ...... 98

6.5.2 Acidification Potential ...... 99

6.5.3 Eutrophication ...... 99

6.5.4 Global Warming Potential ...... 101

6.5.5 Ozone Layer Depletion ...... 101

6.5.6 Human Toxicity ...... 102

6.5.7 Radiation ...... 103

5.5.8 Photochemical Oxidation ...... 104

6.6 Uncertainty Analyses of Steam Methane Reforming ...... 104

6.7 Uncertainty Analyses of Solar and Wind based Hydrogen Production ...... 106

6.8 Comparison of Hydrogen and Gasoline Fuels in Vehicle ...... 107

Conclusions and Recommendations ...... 115

7.1 Conclusions ...... 115

7.2 Recommendations ...... 116

References ...... 118

List of Figures Figure 1.1: Estimated U.S. Energy Use in 2013: 97.4 Quads (Adapted from LLNL U.S. Department of Energy 2013)...... 3 Figure 2.1: Specific energies of various fuels (Modified from Sami et al., 2001)...... 7 Figure 2.2: Five thermochemical routes for the production of solar hydrogen (Modified from Steinfeld, 2005) ...... 13 Figure 2.3: A schematic illustration of a basic water electrolysis system (Modified from Zheng et al ., 2010) ...... 13 Figure 3.1: Steam methane reforming block flow process (Modified from Richa et al ., 2008)...... 23 Figure 3.2: Typical high temperature coal gasification process (Modified from Casper, 1978)...... 23 Figure 3.3: Block diagram of hydrogen production by partial oxidation (Modified from Steinberg et al ., 1989)...... 24 Figure 3.4: Phases of LCA (Modified from Curran, 2012)...... 28 Figure 3.5: Inputs and outputs in LCA (Modified from Curran, 2006) ...... 30 Figure 4.1: System boundaries for life cycle assessment...... 33 Figure 4.2: Renewable solar based hydrogen production approaches ...... 34 Figure 4.3: Geothermal and wind based hydrogen production ...... 35 Figure 4.4: Fossil and nuclear based hydrogen production ...... 36 Figure 4.5: Steam methane reforming and water gas shift reaction (Modified from Spath et al ., 2001)...... 37 Figure 4.6: Hydrogen production via Na-Cl electrolysis using mercury cell (Adapted from Ecoinvent report , 2007) ...... 39 Figure 4.7: Diaphragm cell electrolysis (Adapted from Ecoinvent Report , 2007) ...... 39 Figure 4.8: Membrane cell electrolysis (Adapted from Ecoinvent report , 2007) ...... 40 Figure 4.9: Wind electrolysis system ...... 42 Figure 4.10: Schematic of solar photovoltaic based electricity (Dincer and Joshi , 2013) 43 Figure 5.1: Impact flow diagram of wind power plant...... 54 Figure 6.1: Impact flow diagram of hydrogen production via steam methane reforming. 60 Figure 6.2: Damage assessment for 1 kg of hydrogen via steam methane reforming...... 61

vii

Figure 6.3: Weighting results for 1 kg of hydrogen via steam methane reforming...... 62 Figure 6.4: Contribution of process to total environmental impact for steam methane reforming (CML method)...... 63 Figure 6.5: Effect of variation of reformer pressure on energy and exergy efficiencies. . 64 Figure 6.6: Effect of varying ambient temperature on energy and exergy efficiencies. ... 65 Figure 6.7: Effect of variation inlet pressure of reformer on mass of hydrogen...... 65 Figure 6.8: Effect of variation of ambient temperature on mass of hydrogen ...... 66 Figure 6.9: Effect of increasing hydrogen production on methane and electricity consumption...... 67 Figure 6.10: Effect of variation of reformer temperature on energy and exergy efficiencies...... 67 Figure 6.11: Damage assessment results for hydrogen production via electrolysis using different cell...... 69 Figure 6.12: Flow diagram of hydrogen production via electrolysis using mercury cell. 71 Figure 6.13: Impact flow diagram of hydrogen production using diaphragm cell...... 72 Figure 6.14: Impact flow diagram of hydrogen production using membrane cell...... 73 Figure 6.15: Weighting results for hydrogen production through electrolysis using different cell...... 74 Figure 6.16: Impact assessment chart for hydrogen production through electrolysis using different cell (CML method)...... 75 Figure 6.17: Comparison of impact categories between electrolytic hydrogen production and steam methane reforming (CML method)...... 76 Figure 6.18: Impact flow diagram of hydrogen production via wind based electricity. ... 78 Figure 6.19: Damage assessment chart for hydrogen production using wind electricity. 80 Figure 6.20: Weighting chart for hydrogen production using wind electricity...... 83 Figure 6.21: Impact assessment results for hydrogen production using wind based electricity (CML method)...... 84 Figure 6.22: Effect of variation of inlet pressure on energy and exergy efficiencies of wind based hydrogen production system...... 85 Figure 6.23: Effect of variation of ambient temperature on energy and exergy efficiencies of wind based hydrogen production method ...... 86

viii

Figure 6.24: Effect of variation in the area of wind turbine on energy and exergy efficiencies of wind based hydrogen production...... 86 Figure 6.25: Effect of increasing the amount of produced hydrogen on energy and exergy efficiencies...... 87 Figure 6.26: Effect of variation of wind velocity on energy and exergy efficiencies...... 88 Figure 6.27: Impact flow diagram of hydrogen production via electrolysis using solar photovoltaic electricity...... 90 Figure 6.28: Impact flow diagram of photovoltaic electricity...... 91 Figure 6.30: Damage assessment chart for hydrogen production using solar photovoltaic electricity...... 92 Figure 6.30: Weighting results charts for hydrogen production using solar photovoltaic.95 Figure 6.31: Damage assessment chart for hydrogen production using solar photovoltaic (CML method)...... 96 Figure 6.32: Effect of variation ambient temperature on energy and exergy efficiencies of solar based hydrogen production...... 97 Figure 6.33: Effect of variation of solar irradiation on energy and exergy efficiencies of solar based hydrogen production method...... 98 Figure 6.34: Abiotic depletion per kg of hydrogen for different hydrogen production methods...... 99 Figure 6.35: Acidification potential per kg of hydrogen for different hydrogen production methods...... 100 Figure 6.36: Eutrophication potential per kg of hydrogen for different hydrogen production methods...... 100 Figure 6.37: Global warming potential per kg of hydrogen for different hydrogen production methods...... 101 Figure 6.38: Ozone layer depletion per kg of hydrogen for different hydrogen production methods...... 102 Figure 6.39: Human toxicity per kg of hydrogen for different hydrogen production methods...... 103 Figure 6.40: Radiation per kg of hydrogen for different hydrogen production methods.103

Figure 6.41: Photochemical oxidation per kg of hydrogen for different hydrogen production methods ...... 104 Figure 6.42: Uncertainty analysis results of SMR method for abiotic depletion...... 105 Figure 6.43: Uncertainty analysis results of SMR method for global warming...... 106 Figure 6.44: Uncertainty analysis results of wind and solar based hydrogen production for abiotic depletion ...... 107 Figure 6.45: Uncertainty analysis results of wind and solar based hydrogen production for global warming potential...... 108 Figure 6.46: Uncertainty analysis results of wind and solar based hydrogen production for human toxicity ...... 109 Figure 6.47: GHG emissions of vehicle cycle ...... 110 Figure 6.48: Energy consumption of vehicle cycle...... 111 Figure 6.49: Energy consumption in vehicle distribution and vehicle disposal ...... 112 Figure 6.50: Fuel production comparison in terms of emission ...... 113 Figure 6.51: Fuel production comparison in terms of emissions ...... 113

List of Tables Table 3.1: Common thermochemical decomposition steps in S-I cycles...... 26 Table 3.2: Steps and reactions in the five-step Cu-Cl cycle for thermochemical water decomposition...... 27 Table 3.3: ISO Series for LCA ...... 29 Table 4.1: Data inputs and assumption for 1 kg of hydrogen production via steam methane reforming ...... 38 Table 5.1: Raw material inputs for the production of 1 kg of hydrogen...... 48 Table 5.2: Water and salt consumption in different cells ...... 50 Table 5.3: Input values of chemical and materials used in electrolytic hydrogen production ...... 51 Table 5.4: Energy consumption for the production of hydrogen in different electrolytic cells ...... 51 Table 5.5: Material and energy consumption in wind power plant ...... 52 Table 5.6: Inputs to solar photovoltaic based hydrogen production ...... 55 Table 6.1: Damage assessment for 1 kg of hydrogen via steam methane reforming ...... 57 Table 6.2: Weighting results for 1 kg of hydrogen via steam methane reforming ...... 58 Table 6.3: Contribution of process to total environmental impact for steam methane reforming (CML method) ...... 59 Table 6.4: Damage assessment results for hydrogen production using different cells. .... 68 Table 6.5: Weighting results for hydrogen production using different cell...... 70 Table 6.6: Process contribution of environmental impact categories ...... 70 Table 6.7a: Damage assessment results for hydrogen production using wind electricity. 79 Table 6.8a: Weighting results for hydrogen production using wind electricity...... 82 Table 6.9: Damage assessment results for hydrogen production using solar photovoltaic electricity...... 89 Table 6.10: Damage assessment results for hydrogen production using solar photovoltaic electricity...... 90 Table 6.11a: Weighting results for hydrogen production using solar photovoltaic electricity...... 93 Table 6.12: Impact assessment results for solar based hydrogen production method ...... 94

Table 6.13: Impact assessment results for solar based hydrogen production using CML method ...... 94 Table 6.14: Uncertainty data for hydrogen production through SMR ...... 105 Table 6.15: Uncertainty data for hydrogen production through wind and solar energy . 106 Table 6.16: GHG emission in vehicle cycle ...... 109 Table 6.17: Energy consumption in vehicle cycle ...... 110 Table 6.18: Energy consumption and GHGs emission comparison in vehicle cycle ..... 111

xii

Nomenclature A area (m 2) c specific heat (kJ/kg K) cp specific heat at constant pressure (kJ/kg K) cv specific heat at constant volume (kJ/kg K) D depletion number e specific energy (kJ/kg) E energy (kJ)

E& energy rate (kW) eq equivalent ex specific exergy (flow or non-flow) (kJ/kg) Ex exergy (kJ) & xE exergy rate (kW) h specific enthalpy (kJ/kg) HHV higher heating value (kJ/kg) KE kinetic energy (kJ) LHV lower heating value (kJ/kg) m mass (kg) m& mass flow rate (kg/s ) M molecular weight (g/mol) Pt point R-11 refrigerant 11 Resp. respiratory Sb stibium V velocity (m/s) Greek Letters η energy efficiency ψ exergy efficiency ρ density (kg/m 3)

xiii

Subscripts atm Atmosphere aq Aqueous cyc Cycle el Electrical endo Endothermic exo Exothermic therm Thermal Acronyms AP Acidification Potential BG Biomass Gasification CG Coal Gasification CML Centrum Milieukunde Leiden DALY Disability-adjusted Life Years DB Dichlorobenzene EP Eutrophication Potential GHGs Greenhouse Gases GWP Global Warming Potential IEA International Energy Agency LCA Life Cycle Assessment LCI Life Cycle Inventory LCIA Life Cycle Impact Assessment Na-Cl Sodium chloride NREL National Renewable Energy Laboratory ODP Ozone Depletion Potential PAF Potentially Affected Fraction PDF Potentially Disappeared Fraction PV Photovoltaics S-I Sulphur-Iodine SMR Steam Methane Reforming

xiv

Introduction

Energy is considered as a key component of all activities and plays a major role in the economic development of any country. Over time, energy demand in every sector keeps increasing due to the large amount of consumption, increasing population, change in life style and technological advancement. Almost every sector is dependent on energy which comes mainly from fossil sources. Report by International Energy Outlook ( IEO, 2013), predicted that the world energy consumption will rise by 56% between the years 2010 to 2040. In this prediction, conventional fossil fuel will share about 78% and rest of the number will be fulfilled by renewable and nuclear sources. The massive utilization of fossil fuels is responsible for climate change, greenhouse gas emissions, and pollutants

(e.g. CO, CO 2, SO x, NO x, ashes etc.). All these gases and air pollutants damage the stratospheric ozone layer and create smog. This results in people getting health issues such as lung and respiratory disorder, eye irritation and blood related disease (Granovskii et al ., 2007). The transportation sector is the second major consumer of energy where petroleum and other liquid fuels consumption are very high after electricity generation (industrial). Annual energy utilization in transportation sector increases 1.1 percent ( IEO 2013) and majority of the energy demand is being provided by fossil fuels. Moreover, the transportation industry is considered the most inefficient sector in the US in terms of fuel efficiency, about 76% of supply energy is lost as heat (LLNL, U.S. Department of Energy 2013) as shown in Figure 1.1. These negative results motivate researchers to look for an alternate of fossil fuels and a lot of work has been done in this search. Energy strategies will play an important role for future world stability. In case of energy consumption in transportation several renewable technologies are available in terms of renewable biofuels, solar car, electric vehicle etc. Each of them has some limitations for example in electric car, a battery need to charge by external electricity which also comes from conventional method. A solar vehicle is dependent on the solar radiation and might not work in areas where sun light is not consistent. Among various alternatives, hydrogen as a fuel for vehicles offers the highest potential gain which can replace petroleum products and thus decrease the Greenhouse gas (GHG) emissions and air pollution. Due to their environmental compatible property, hydrogen possibly will

1 become one of the most feasible energy carriers in the future for various applications (Midilli et al ., 2005). Many researchers have studied the properties and behaviour of hydrogen as a fuel. Hydrogen can provide ecologically benign transportation systems depending on the energy and material source (Granovskii et al ., 2006). Some study focus on the contribution of hydrogen regarding the solution of environmental problems (Dincer 2002). Environmentalists and other industrial sector professionals have encouraged the use of hydrogen in different sectors (Gupta 2009). Hydrogen is extensively available on earth along with different chemical composition such as water and natural gas. It is colorless, odorless and nontoxic. It does not produce acid rain, harmful emissions and providing 2-3 times more energy than other common fuels (Momirlan et al., 2009). In fact, hydrogen can be produced from available abundant sources by different method. Again majority of hydrogen is produced from fossil fuels using a process called steam reforming of natural gas, which is responsible for massive emissions of greenhouse gases. About 48% hydrogen demand is fulfilled by natural gas, 30% by petroleum industry, 18% from gasification of coal, 3.9% from electrolysis and remaining 0.1% from other processes (Kalamaras et al., 2013). Scientists are still looking for renewable sources of hydrogen production on large scale. Renewable-based hydrogen can lead to the notably lower environmental impacts. It depends upon many factors involved over their lifetime such as natural resource extraction, plant construction, final product distribution and utilization. Sufficient evaluation of environmental impact and use of energy throughout the production and utilization from cradle to grave is critical for the proper assessment of technologies (Granovskii et al., 2007). In order to study any operation from cradle to grave life cycle assessment (LCA) is the methodology that represents a systematic set of procedures for examining the inputs and outputs of materials and energy. A life cycle is the interlinked stages of a product or service system, from the extraction of natural resources to their final disposal. Within a LCA, the mass and energy flows and environmental impacts related to plant construction, operation and dismantling stages are accounted for. The determination of all input and output flows is often very complicated, so some simplifications and

2 assumptions are often made to facilitate an LCA. The challenge is to ensure the assumptions and simplifications (e.g., simplified models of processes) retain the main characteristics of the actual system or process being analyzed .

LLNL U.S. U.S. LLNL Adapted from from Adapted

Department of Energy 2013). of Energy Department Estimated U.S. Energy Use in 2013: 97.4 Quads ( Quads 97.4 in Use 2013: Energy U.S. Estimated

: 1 . 1 Figure Figure

1.1 Motivation and Objectives 1.1.1 Motivation With the world’s increasing population and rising global energy demand, hydrogen is considered as an ideal energy carrier due to its abundance and high energy conversion efficiencies. However, regardless of the enormous prospective benefits of using hydrogen as a fuel, the emissions related to its production is yet to be explored. The fundamental motivation of this work is the potential of minimizing emissions related to different hydrogen production methods by comparing selected methods energetically and exergetically. For this determination, comparative assessment on different hydrogen production methods is performed keeping in mind their respective emissions. A significant amount of literature has been published about several hydrogen production methods but only few of them investigated the life cycle assessment. Hence lack of literature about the impact of different hydrogen production systems on the environment restricts investment in this area. A different approach which makes this comprehensive study quite interesting is to implement life cycle assessment of hydrogen production methods using software and other available tools.

1.1.2 Objectives The main objective of this thesis is to investigate different hydrogen production methods/systems and implement the life cycle assessment methodology on these hydrogen production methods. The objective will be achieved using a commercial software (so-called: SimaPro) which has special features of impact assessment. It can assess the life cycle inventory data in a systematic way at all the different stages of a process/system.

This research study consists of the following sub-objectives: 1. Investigate different hydrogen production methods in terms of fuel sources such as renewables and fossil fuels. • Conduct a comprehensive study on each method and compare different resources which will provide source of energy to operate hydrogen production processes.

• Compare the energy consumption in each method which gives the better understanding of the hydrogen production process with less environmental impact.

2. Implement an LCA on these different methods in order to compare them in terms of carbon dioxide equivalent emissions and other pollutants. • Use LCA to identify the impact of a system on the environment throughout its life cycle. • Use LCA tool such as the SimaPro to analyse the environmental aspects of every method in a systematic way. SimaPro covers both aspects on the environment in term of raw material and emissions.

3. Analyse different hydrogen production methods energetically and exergetically to provide a better understanding of the thermodynamic analysis. • Calculate energy and exergy efficiencies of selected hydrogen production methods. • Performance a comprehensive assessment of hydrogen production methods through parametric studies to examine the effects of varying environment and other system conditions.

4. Different impact assessment methods in LCA are available such as the Eco-indicator 99, impact 2002+, CML 2 baseline 2000 etc. The Eco-indicator 99 and CML 2001 will covers major parts of this study.

5. Impact assessment was performed by considering significant environmental impacts categories which are as follows: • Ozone layer • Carcinogens • Respiratory Organics and Inorganics • Ecotoxicity • Acidification • Global warming

Literature Review Studies in the past have been conducted to investigate and compare the of hydrogen production methods. Methods of hydrogen production such as steam reforming of natural gas, thermochemical water splitting with Cu-Cl cycle and some other renewable and nuclear based process investigated and published. Few of them implemented the LCA methodology to carry out environmental impact assessment, air borne, water and soil emissions. In this chapter a brief review on several LCA studies is provided.

Today’s world is in a serious need of alternate of conventional fuels. Among various alternatives, hydrogen has the highest potential in terms of availability and reduced emissions of pollutant and greenhouse gases. At present, hydrogen is mainly used as a chemical substance rather than fuel despite it has a market of fifty billion US$ for 40 Mt annual production (Dincer, 2012). Several studies such as Dincer (2012), Dincer et al. (2009), Hussain et al. (2007), Marban et al. (2006), Bockris (2002) introduced and promoted hydrogen as a future energy and their basic remarks over hydrogen can be drawn as follows:

• Hydrogen has a high quality energy carrier, which can be used for high efficiency with zero or near zero emissions. • During combustion with air or used in a fuel cell to generate electricity, only water and small quantity of NOx is a product. • It has been technically proven that hydrogen can be used for transportation, heating, and power generation, and could replace current fuels in all their present uses. • Hydrogen exhibits the highest heating value per mass among all chemical fuels as shown in Figure 2.1 and it is regenerative and environmentally friendly. Moreover, hydrogen has attractive electrochemical property, which can be utilized in a fuel cell. • Hydrogen can be stored in different forms such as in gaseous form suitable for large scale storage, in a liquid form which is suitable for air and space transportation or in the form of metal hydrides to be convenient for small scale storage requirements

160 141.9 140

120

100

80 55.8 60 45.8 46.5 47.9 50.4 39.6 40 29.7 30.2

Specific Energy (kJ/g) 14.9 20

Fuel

Figure 2.1: Specific energies of various fuels (Modified from Sami et al., 2001). These aforementioned properties of hydrogen are ideally suitable for using in a vehicle as a fuel. The technical and economic challenges of implementing hydrogen energy are still there which need to be address properly. Michael et al. (2009) highlighted the challenges and opportunities of promoting hydrogen as alternative fuel in the transport sector. The major technical challenges of introducing hydrogen as vehicle fuel includes the development of efficient and cost competitive fuel cells, designing of long period safe structure for the hydrogen storage and large scale infrastructure for hydrogen production, distribution and refueling. The economic analysis revealed that the introduction of hydrogen results in positive effects for long term by assuming the same level of difficulties as we have today. The overall impact on economic growth (GDP) into the energy system is small. The fact that hydrogen is introduced in only part of the energy system also helps to explain the relatively small impacts on GDP.

Dincer (2002) studied the hydrogen energy systems for the fuel cell. His study covers the technical, environmental and exergetic aspects of hydrogen energy systems. Exergy concept is introduced and two case studies are also discussed. Study suggested that the environmental problems relating to energy should be understood widely and ensures that the potential solutions are beneficial for the economy and energy systems. Moreover, hydrogen is the most efficient and the safest fuel; it is one of the best

7 alternatives as the most versatile fuel. Lastly, exergy analysis is an effective method to design more efficient energy systems by decreasing the inefficiencies in existing systems.

From the brief discussion above, in conclusion, hydrogen is a very promising clean fuel. In this thesis, we will concentrate on comparison of hydrogen production methods for vehicles.

2.1 Methods of Hydrogen Production Production of hydrogen is one of the important aspect including the energy consumed and emissions during the process. Currently, hydrogen that is produced covers only 2% of the world energy demand (Gupta 2009). Hydrogen can be produced from a diversity of energy resources such as fossil, renewable and nuclear using a variety technology which are discussed below.

2.2 Fossil Fuel Hydrogen Production Hydrogen can be produced from the fossil fuels by steam reforming and coal gasification. About more than 90% of hydrogen is produced from fossil fuels and steam reforming is the most common method (Ozbilen et al . 2011). In steam reforming of natural gas, three steps are involved for hydrogen production. Methane is first cleaned from impurities then mixed with steam and passed over an externally heated reactor at high temperature, where carbon monoxide (CO) and hydrogen (H 2) are produced. After this step, additional hydrogen can be generated through a water-gas shift reaction by which carbon monoxide and water is converted to hydrogen and carbon dioxide (CO 2). Finally, the hydrogen gas is then purified for use. Following is the chemical reaction for steam methane reforming and water gas shift reaction, respectively.

CH 4 + H 2O → CO + 3H 2 (2.1)

CO + H 2O → CO 2 + H 2 (2.2)

Acar and Dincer et al . (2014) compared different hydrogen production method in order to assess their economic, social and environmental impacts. The methods considered in their study are natural gas steam reforming, coal gasification, water electrolysis via wind and solar energies, biomass gasification, thermochemical water

8 splitting with a Cu-Cl and S-I cycles, and high temperature electrolysis. Environmental impacts such as global warming potential and acidification potential, and production costs, energy and exergy efficiencies of these eight methods are compared. Results indicated that biomass gasification has the lowest hydrogen production cost ($/kg). Natural gas steam reforming and coal gasification have lower costs than the rest of the methods as well. In terms of capital costs, it can be seen that natural gas steam reforming has lower costs than coal and biomass gasification.

Cormos (2011) analysed innovative processes for producing hydrogen from fossil fuels conversion (natural gas, coal, lignite) using chemical looping technique. The assessment carried out to generate hydrogen from the potential applications of natural gas and syngas chemical looping combustion. Plant which has been investigated produce 500 MW hydrogen (based on lower heating value) by covering all ancillary power consumptions.

Coal gasification is another major process of hydrogen production after steam reforming of natural gas. More than 18% of hydrogen is generated by coal (Kalamaras et al ., 2013). Coal gasification comprises three principal steps. First, the conversion of coal feedstock with steam to form a syngas and then catalytic shift conversion takes place, and lastly, purification of final product. Initially, coal is chemically reacted with high temperature and high pressure steam which has a temperature of approximately 1330ºC to produce raw synthesis gas. After syngas production, the syngas passes through a shift reactor to convert a portion of the carbon monoxide to carbon dioxide. Finally, in third step, the hydrogen product is purified (Cohce, 2010).Coal gasification process need gasifier and O 2 for the reaction process which makes this process more expensive than natural gas reforming (Cohce et al., 2011).

Huang et al. (2014) conducted the parametric study and assessment of coal gasification plant for hydrogen production. The purpose of study is to show the best steam to carbon ratio that produces the maximum system performance of an integrated gasifier for hydrogen production. Moreover, study focuses on the energy and exergy efficiency of the system and hydrogen production. When steam to carbon ratio feed in the gasifier is increased, the improvement can be seen in the energy and exergy efficiency of

9 the IGHP system. The maximum efficiency is reached with a SC of 0.9 with an energy and exergy efficiency of 53.8% and 44.8% respectively. Hydrogen production rate is at its highest at 0.61 kg/s at the same SC value. The study also concluded that the coal gasification is a very clean method of utilizing coal to meet their energy demands. The process has amount of pollution compared to coal combustion. Furthermore, in this technology the syngas can be used immediately in gas turbines, or it can be processed into hydrogen and stored for later use.

Nirmal et al . (2010) compared the energy and exergy efficiencies of an integrated coal-gasification combined-cycle power generation system with that of coal gasification- based hydrogen production system which uses water-gas shift and membrane reactors. The syngas is used to generate electricity and produce hydrogen and assessed for two coal gasification-based energy systems. The system which is used to produce hydrogen from syngas offers 35% higher energy and 17% higher exergy efficiencies than the syngas-to-electricity (IGCC) system. As far as emission is concerned, specific carbon dioxide emission from the hydrogen system was 5% lower than IGCC system. Moreover, electrical power consumption for the IGCC system in order to compress the exhaust gases to store CO 2 is above 70% which is only 4.5% for the H 2 system. To conclude, syngas-to- hydrogen system is advantageous over IGCC system in terms of power consumption, efficiency and emissions.

Rosen (1996) thermodynamically compared different hydrogen production methods. The comparison is based on the energy and exergy analyses of processes which are hydrocarbon-based such as steam methane reforming and coal gasification, non- hydrocarbon-based and integrated SMR linked to the non-hydrocarbon based. Analysis is performed using Aspen Plus software and result show the wide range efficiency variation. Energy efficiency varied from 21 to 86% whereas exergy efficiency changes from 19 to 83% for the processes considered. However, most of the time the energy and exergy efficiencies are similar because of the similarity in the magnitude of the input energy and exergy and product energy and exergy.

2.3 Renewable Hydrogen Production Hydrogen can also be produced from non-conventional renewable sources such as solar, geothermal, biomass and wind. Renewable based hydrogen production has the advantage of being environmentally friendly with zero or minimum greenhouse gas emissions. Hydrogen is not available as a separate element. It is obtain from a number of sources such as hydrocarbon, biomass, water and other chemical elements with hydrogen. Therefore, energy is required to extract hydrogen from above mentioned sources. Dincer et al . (2013) categorized four forms of energy: thermal, electrical, photonic and biochemical which drive hydrogen production process. These four forms of energy can be obtained from renewable sources that can be used to fascinate the primary energy demands for environmentally benign hydrogen production.

2.3.1 Solar Based Hydrogen Production Solar energy is widely used in power generation, heating and other useful products around the world. Suleman et al. (2014) utilized solar energy in the development of multigeneration system and in integrated solar heat pump system. Solar based hydrogen production is one of the method by which greenhouse gases can be minimized. However, solar photovoltaic is not a cost effective hydrogen production method as the PV technology is costly (Joshi et al ., 2009). The technology which is currently used for hydrogen from photovoltaic electrolysis has cost about 25 times higher than that of fossil fuel replacements. But the cost is expected to decrease due to improvement in the photovoltaic cell. Furthermore, the factor is estimated to go down to 6 (Dell et al., 2009). Various solar hydrogen production systems are available such as solar Photovoltaic, solar photo electrochemical, solar photo biological and concentrated solar thermal. Under each systems mentioned above have different processes to harvest hydrogen from water and other chemical containing hydrogen.

Joshi et al. (2011) performed a comparative performance assessment study of solar thermal and photovoltaic (PV) hydrogen production method. Numerous categories of solar hydrogen production systems are studied for their performance based on energy and exergy analysis and sustainability index. Solar thermal hydrogen production by electricity production appears to be environmentally benign method and has greater

11 efficiency than PV hydrogen production. However, the PV hydrogen production is better because it does not involve any moving parts. Moreover, the exergy efficiency of PV panel alters with the concentration of solar radiation and ambient temperature which causes lower exergy efficiency of PV hydrogen production. Proper design improvements and use of particular technologies may increase the exergy efficiency of the system.

Ganovskii et al . (2007) used exergetic life cycle assessment on hydrogen production from renewables such as solar and wind to evaluate exergy and economic efficiencies and environmental impacts. Furthermore, fossil fuel technologies for producing hydrogen from natural gas and gasoline from crude oil are compared with options using renewable energy. Solar energy considered here comprises two main systems: a solar photovoltaic system that produces electricity which in turn drives a water electrolysis division to produce hydrogen. Solar energy is converted into direct current electricity by photovoltaic elements, which is transformed by inverters to alternating current (ac) electricity and transmitted to the power grid. The 1.231-kW photovoltaic system combined with water electrolysis can produce 807.3 J s -1 of hydrogen exergy, when the efficiency of electrolysis and transmission loses have considered.

Steinfeld (2005) reviewed different solar thermochemical production of hydrogen. He divided three pathways to produce hydrogen from solar energy which are electrochemical, photochemical and thermochemical. In thermochemical hydrogen production, water is decomposed into hydrogen and oxygen through arrangements of thermal driven chemical reactions. In solar thermochemical hydrogen production, concentrated solar radiation is the energy source of high-temperature process heat for driving an endothermic chemical reaction. Five thermochemical ways for solar hydrogen production are illustrated in Figure 2.2.

Zheng et al. (2010) studied the progress in alkaline water electrolysis for hydrogen production using solar energy. Study found that alkaline water electrolysis combined with renewable solar energy can be combined into the distributed energy system by generating hydrogen for end use and as an energy storage media. Although, alkaline water electrolysis is less efficient, have issues in safety and durability. It is simple in contrast to the other major methods for hydrogen production. A basic water

12 electrolysis setup is illustrated in Figure 2.3 which has an anode, cathode, power supply and an electrolyte.

Figure 2.2: Five thermochemical routes for the production of solar hydrogen (Modified from Steinfeld, 2005)

Figure 2.3: A schematic illustration of a basic water electrolysis system (Modified from Zheng et al ., 2010)

2.3.2 Wind Based Hydrogen production Hydrogen generation from wind is also a decent option in terms of harnessing energy from renewable source. Electricity produced by wind turbines can be used for electrolysis for hydrogen production process. This method has the maximum potential of producing hydrogen with minimum pollution among renewable sources (Acar and Dincer , 2014). Wind energy technology is commercially available to provide electricity for the electrolysis of hydrogen production. However, the production of hydrogen through electrolysis from wind energy is not currently cost-competitive because of the cost of wind turbines and electrolysers which make high electricity cost relative to grid electricity.

Olateju et al . (2011) developed a detail data-intensive techno-economic model for assessment of hydrogen production in western Canada from wind energy through the electrolysis of water. This projected hydrogen plant is based on a current wind turbine unit of size 1.8 MW and has a multiple function of electricity generation and hydrogen production. During the constant flow rate electrolysers the best optimal size is found to be 3 3 240 kW (50 Nm H2/h) and for variable flow rate it is 360 kW (90 Nm H2/h). The hydrogen production price from their study is calculated as $10.15/kg H 2 and $7.55/kg

H2, respectively. As far emission is concern, emitted CO 2 is found per kg of H 2 is 6.35 kg together with delivery to upgrader. Furthermore, the system produced oxygen can be utilized commercially to reduce production price.

Akyuz et al. (2012) investigated the performance of hydrogen production from a hybrid wind-PV system. The proposed hybrid system consisted of 10 kW wind and 1 kW PV arrangement which is built to meet the load demand renewable energy sources. In their study, the wind statistics of the selected region are analyzed for sizing of the renewable energy system and performance is examined in terms of energy efficiency and

H2 production capacity. The results stated that from the month of April to July, the average range of state of charge varies between 56.6% and 88.3%. The maximum amount of hydrogen production is about 14.4 kg in the month of July provided by excess electricity because of high wind speed and solar radiations. Moreover, they found out the

14 energy efficiency of the electrolyser is varying between 64% and 70% and overall energy efficiency of wind electrolyser system varies between 5% and 14%.

Granovskii et al . (2007) studied the greenhouse gas emissions by introducing wind and solar energies for hydrogen and electricity production. They addressed the economic aspects of using renewable energies in place of fossil fuels to reduced greenhouse gas emissions. Although, there are greenhouse gas emissions from renewable technologies and are associated mainly with plant construction and the magnitudes are considerably lower. Results showed that the prospects are good for producing clean fuel “Hydrogen” through water electrolysis lead by renewable electricity. However, the cost of electricity from solar and wind is higher than natural gas power plant. Their analysis indicated that when electricity from renewable sources replaces electricity from natural gas, the declination in the cost of greenhouse gas emissions is about four times less than if hydrogen from renewable sources replaces hydrogen produced from natural gas. Similarly when renewable based hydrogen is used in a fuel cell vehicle, the cost of greenhouse gas emissions reduction tends the same value as for renewable based electricity only if the fuel cell vehicle efficiency exceeds considerably by about two times that of an IC engine vehicle.

2.3.3 Geothermal Based Hydrogen Production Geothermal based hydrogen production uses geothermal energy source for hydrogen production which is seen as an environmentally available and sustainable alternative especially for the countries having abundant geothermal energy resources. The technologies of hydrogen production can be combined with geothermal sources which will help to grow hydrogen economy faster (Maack et al., 2006).

Balta et al. (2010) examined low temperature thermochemical and hybrid cycles for hydrogen production based on geothermal energy source out of four potential methods for hydrogen production. They are: by using steam directly from geothermal, through conventional water electrolysis using the electricity generated from geothermal power plant, by using both geothermal heat and electricity for high temperature steam electrolysis and/or hybrid processes and by using the heat available from geothermal resource in thermochemical processes to disassociate water into hydrogen and oxygen.

Moreover, they compared three types of industrial electrolysis for hydrogen production with the thermochemical hybrid cycles. The findings of their study are listed as follows:

• Comparing among different thermochemical cycles, the Cu–Cl cycle acts to be the most capable low temperature cycle to produce hydrogen efficiently. • The energy and exergy efficiencies vary between 26% and 51%and 33% and 65%, respectively, for the Cu–Cl cycle. The energetic and exergetic renewability ratios of Cu–Cl are obtained as 0.36 and 0.45, respectively. • Hydrogen production from geothermal requires more research and development on the implementation this technology cost effectively and efficiently.

Yilmaz et al. (2012) considered seven models for the production and liquefaction of hydrogen by geothermal energy using electrolysis and high temperature steam electrolysis. The study emphasis the development of the economic analysis methodology and it is estimated the cost of hydrogen production and liquefaction ranges between 0.979

$/kg H 2 and 2.615 $/kg H 2 at a geothermal water temperature of 200 ◦C depending on the model. Moreover, the outcome of geothermal water temperature on the cost of hydrogen production and liquefaction is also investigated and results show the increase in the geothermal water temperature decreases in the cost of hydrogen production and liquefaction.

Balta et al . (2010) analysed the new four-step copper chlorine cycle for geothermal based hydrogen. The system inspected through energy and exergy methodology and parametric study was also implemented to investigate how individual step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures along with energy efficiency of the geothermal power plant itself. The conducted study showed that the overall energy and exergy efficiencies of the Cu-Cl cycle are found to be 21.67% and 19.35%, respectively while the variation of energy efficiency is from 15.8% to 19.35% and exergitically it is from 16.8% to 20.5%. Furthermore, the implementation of geothermal energy through hybrid or thermochemical cycles for green hydrogen production appears to be an eco-friendly and sustainable option for the countries having abundant geothermal energy resources.

2.3.4 Biomass based Hydrogen production Biomass based hydrogen production is a complex process and currently this process is unable to produce hydrogen on large scale (Canan et al . 2014). Several biomaterials such as wood waste, forestry, and agricultural remains, municipal and animal waste, and/or crops can be used as biomass for hydrogen formation. Biomass can be converting into useful forms of energy products by different procedure. The most approving thermochemical conversion processes for utilizing renewable biomass energy are pyrolysis and gasification of the waste materials (Ozbilen 2010).

Yildiz et al . (2012) performed the life cycle assessment of biomass based hydrogen production and applied LCA analysis from the period biomass production to the use of the produced hydrogen in Proton Exchange Membrane (PEM) fuel cell vehicles. Two gasification system were compared through LCA and greenhouse gas emissions are calculated. The study showed that the most energy is consumed by the hydrogen transportation step in the DG. All values are adjusted for 1 MJ/s hydrogen production for the comparison of two gasification system. Fossil energy consumption rate and emissions are determined as 0.088 MJ/s and 0.175 MJ/s, and 6.27 CO 2-eq. g/s and

17.13 CO 2-eq. g/s for the DG and CFBG, respectively.

Jiang et al . (2013) produced hydrogen from integrated system derived from biomass syngas by using membrane reactor. They utilized biomass efficiently by first gasified it into syngas then processed in a water gas shift (WGS) reactor to further enhance its hydrogen content. A single CMS membrane was used for the in situ hydrogen separation and syngas cleanup. The process showed several advantages over traditional reactor system such as more CO conversion and purity of hydrogen. However, reaction took place in the presence of common impurities such as H 2S, NH 3 and organic vapor and able to produce impurity free hydrogen. To conclude, the proposed system is a multifunctional system which involves WGS reaction, the separation of hydrogen product and the removal of syngas impurities into a single step and biomass derived hydrogen production results in an energy saving process.

2.4 Nuclear Based Hydrogen Production Nuclear energy is attractive source of energy for hydrogen production because of many reasons defines by Dincer (2012) such as it has minimum emissions of greenhouse gases as compared with conventional fossil fuel combustion and nuclear energy is adaptable to large-scale hydrogen production. Thermochemical water splitting and high temperature electrolysis are two common method of producing hydrogen using nuclear energy. Marcus et al . (2002) defined thermochemical water splitting cycles that operates at a temperature of 500 ◦C using nuclear reactors. Naterer et al . (2013) predicted five general methods to generate hydrogen from nuclear energy through water decomposition radiolysis, electrolysis, high temperature steam electrolysis, hybrid thermochemical water splitting, and thermochemical water splitting.

Ozbilen (2010) assessed nuclear energy for the production of hydrogen using copper-chlorine cycle. The life cycle methodology was implemented to explore the environmental impacts of nuclear based hydrogen. Initially, LCA implemented on the three-, four-, five-step Cu-Cl cycle for four different scenarios and different impact categories are presented on the basis of four scenario. Results showed that the global warming potential will decrease 15.8 kg to 0.56 kg CO 2-eq, if electrical energy from nuclear plant is used for all process of hydrogen production. Parametric study suggested that the increase in plant hydrogen production capacity and lifetime does not have substantial effects on impact categories per kg hydrogen production if the production capacities and plant lifetimes are sufficient. Moreover, the nuclear-based sulphur-iodine cycle and four steps Cu-Cl are the best environmentally benign hydrogen production in terms of acidification potential and global warming potential. For the sulphur iodine cycle, the global warming potential is 0.412 kg CO 2 equivalent and for the four-step Cu-

Cl cycles it is found to be 0.559 kg CO 2 -eq.

Ryland et al . (2007) investigated the technical issues and economics of hydrogen production by integrating a steam electrolysis system with the advanced CANDU Reactor ACR-1000 in Canada. Result proved that it is feasible to generate hydrogen by using nuclear reactor energy and the reactor provides both thermal and electrical energy to the steam electrolysis process. Moreover, about 15% of the steam produced by the reactor

18 would be diverted to provide thermal energy to the HTE plant. Lastly, the larger production of the hydrogen from the plant would require more thermal energy from the reactor, thus reducing the electrical output of the plant and would produce 275000 Nm 3 h- 1 of hydrogen.

2.5 Life Cycle Assessment Numerous studies on life cycle assessment of different hydrogen production method have been reported by many researchers. However, the comparison between different hydrogen production technologies through LCA is not carefully considered. Cetinkaya et al . (2012) reported comprehensive life cycle assessment (LCA) for five methods of hydrogen production, which are steam reforming of natural gas, coal gasification, water electrolysis via wind and solar electrolysis, and thermochemical water splitting with a Cu-Cl cycle. Each method is measured and compared in terms of carbon dioxide equivalent emissions and energy equivalents. Moreover, global warming potentials are quantified for each method. Results show that the hydrogen production capacities of wind turbines and PVs are comparatively less than the other methods such as, in coal gasification the production capacity is 20,000 times the wind power production in their study but wind electrolysis is the most environmentally benign method followed by solar PV power.

Ozbilen et al. (2012) applied the exergetic life cycle assessment on hydrogen production method. They examined the environmental impacts of a nuclear-based hydrogen production via thermochemical water splitting using a copper chlorine cycle. The parametric studies demonstrate that the effect of plant lifetime on environment per kg hydrogen production diminishes at large-scale production capacities. Exergetic life cycle results of their study are summarized below:

• The uranium processing is the main contributor of life cycle irreversibility of nuclear-based hydrogen production, for which the exergy efficiency is 26.7% and the exergy destruction is 2916.3 MJ.

• The plant capacity of 125,000 kg H 2/day has the lowest global warming potential

per MJ exergy of hydrogen which is 5.65 g CO 2 – eq.

• The lowest GWP per MJ exergy of hydrogen is 5.65 g CO 2-eq, for a plant capacity

of 125,000 kg H 2/day. Similarly, the equivalent CO 2 for the plant capacity of

62,500 kg H 2/day is about 5.75 g. • The results also suggested that if 98% of exergy is obtained then GWP can be

reduced to as low as 5.4 g CO 2-eq per MJ exergy of hydrogen. Similarly,

acidification potential can also be reduced from the value of 0.041 to 0.027 g SO 2- eq per MJ exergy of hydrogen, when the exergy efficiency is increased from 67% to 98%. Hajjaji et al. (2013) conducted the comparative life cycle assessment of eight hydrogen production scenarios. The comparison analysed the sustainability performance of different options in the production of H 2 and focuses on the key factor of every alternatives. The assessment is carried out by using impact assessment method such as the CML baseline 2000 and the Eco-indicator 99 through the SimaPro 7.1 package. The results indicated that the biomethane reforming systems have the lowest impact which is 0.41 pt. compare to other systems. The natural gas reforming method is not suitable in terms of environmental pollution because it has the highest emissions of global warming gas and has the greatest contribution to the abiotic depletion potential impact. However, bio-ethanol which is considered to be a biofuel (wheat derived), hydrogen production from bio-ethanol systems have a higher impact on environment than fossil CH 4 on acidification, eutrophication, ozone layer depletion and toxicological impacts. Bio- ethanol uses excessive fertilizer and machinery, where large amount of energy is consumed for reforming. Koroneos et al . (2004) examined the life cycle assessment of hydrogen fuel production processes in order to investigate the environmental aspects of hydrogen production. The advantages and possible drawbacks of the competing hydrogen production systems are reported which reveals that the large amount of environmental problems result from the operation of the different hydrogen production methods. Production from natural gas steam reforming and production from renewable sources are analysed and compared. Results explained that the use of photovoltaic energy has the worst environmental performance than all the other technologies due to low overall efficiency of the photovoltaic system. However, the use of solar, wind and hydropower

20 energy routes are proved to be the most environmentally friendly because of low equivalent emissions. Steam reforming of natural gas has the high equivalent emissions and losses of CO 2 and SO 2 to the atmosphere during production and distribution which have the major negative impact and global warming potential of the system.

Background

In this chapter, the background information of various hydrogen production methods is presented. The basic option in each method is described and discussed in order to provide an insight of different technologies. Moreover, the comparisons of various methods are made and the possible environmental issues involved with each method are also discussed.

3.1 Hydrogen Production Methods Hydrogen can be generated by using diverse resources and technologies. The resources used by different methods are fossil fuel, nuclear and renewable sources. Each source has certain benefits and limitations. Fossil fuels are widely used all over the world in the production of hydrogen which is also responsible for greenhouse gas emissions and other pollution. Nuclear and renewable sources are suitable for hydrogen production in terms of clean energy but the technology needs improvement and modification in order to reduce cost and increase efficiency.

3.1.1 Natural Gas Steam Reforming About, half of the hydrogen produced in the world is obtained by steam reforming of natural gas. By this method the natural gas, methane, reacts with high temperature steam in a catalytic converter. The process needs a nickel catalyst and temperature requirement of above 1000 K (Brown, 2001). The steam methane reaction generates carbon monoxide and hydrogen. The reaction is endothermic and heat is supplied externally by burning fuel outside the reactor tube. Water gas shift reactions under high and low temperature convert the carbon monoxide to carbon dioxide and produce additional hydrogen. Hydrogen production is normally 72% to 85% efficient in natural-gas reformers; the remaining is heat that may also be reusable (Tupper, 2002). The following chemical reactions are used in the steam reforming process of methane:

3 (3.1)

The water gas shift reaction then allows water to react with carbon monoxide to produce more hydrogen as

→ (3.2)

Heat H2O Heat H2O

Natural gas CH 4

4H2 (Pure) CH 4 CO + 3H2 CO 2 + 4H2 Pretreatment Reforming Water shift Purification

Gas impurities Heat CO 2 & other impurities

Figure 3.1: Steam methane reforming block flow process (Modified from Richa et al ., 2008).

3.1.2 Coal Gasification Coal gasification is another possible technology for the production of hydrogen. In this process coal converted from a solid to a gas and resulting gas is very similar to natural gas which can be used to create different fertilizer, chemicals, and/or electric power. In coal gasification coal is broken down into its basic constituents. Coal is oxidized within the gasifier in the presence of oxygen and steam and is combined to produce synthesis gas. The gas composition leaving the gasifier comprises 29 vol% H 2, 60 vol% CO, 10 vol% CO 2 and 1 vol% inert (Agnieszka, 2003). In order to produce hydrogen, this synthesis gas is further processed using water- gas shift reactor technology to increase hydrogen and convert carbon monoxide to carbon dioxide. The clean gas is then sent to a separation system to recover the hydrogen (Cormos et al., 2008)

Steam Oxygen Steam

Gasification Shift Reaction C + 1/2O2 → CO + Heat Purification Coal H2 C + H2O → CO + H2 CO + H2O → CO 2 +H2

Ash Residue

Figure 3.2: Typical high temperature coal gasification process (Modified from Casper, 1978).

Sulfur

Syngas Shift Reaction

Desulfurization

Air N 2

Raw Gas

Air Gasification Separation Gas Purification

CO 2 H2 Feed Steam Products

Figure 3.3: Block diagram of hydrogen production by partial oxidation (Modified from Steinberg et al ., 1989).

3.1.3 Partial Oxidation Partial oxidation of hydrocarbons is another hydrogen production method. It is an exothermic reaction with oxygen and steam at moderately high pressure with or without a catalyst. In this process, heavy hydrocarbons are converted by superheated steam and oxygen to a mixture of H 2, CO, and CO 2. This process also requires water gas shift reaction to increase the H 2 amount like in steam methane reforming. In catalytic partial oxidation, methane to naphtha can be used and the reaction takes place at 590 ◦C. On the other side, the non-catalytic partial oxidation occurs at a temperature range of 1150 ◦C to 1315 ◦C and uses methane, heavy oil and coal as feedstock. The usual composition of the synthesis gas leaving a partial oxidation reactor is H 2 46 vol%, CO 46 vol%, CO 2 6 vol%,

CH 4 1 vol%, and N 2 1 vol% (Goswami et al . 2003). The following is the basic reaction for partial oxidation of heavier hydrocarbon (Richa et al., 2004):

2C nHm + H 2O + 23/2O 2 → nCO + nCO 2 + (m+1) H 2 (3.4)

3.1.4 Electrolysis Water electrolysis was first proposed by Michael Faraday in 1820 and today it is one of the industrial hydrogen production processes which does not depend on fossil energy. Electrolysis is a method of splitting chemically bonded elements and compounds by passing an electric current through them. Water electrolysis also called solid oxide steam electrolysis is a method in which water is separated into oxygen and hydrogen by passing an electric current. The electrolysis process requires the implementation of a diaphragm or separator to avoid the recombination of the hydrogen and the oxygen generated at the electrodes (Alferedo et al., 2012). So the two electrodes separated by an ion conducting electrolyte and two partial reactions take place at these two electrodes. Hydrogen is produced at the cathode and oxygen is produced at the anode and the processes are represented by the following reactions:

Cathode: 4H 2O + 4 → 2H2 + 4O H (3.5)

Anode: 4O H → O2 + 2H 2O + 4 (3.6)

Net: 2H 2O → 2H 2 + O 2 (3.7)

The process system involves a water purification plant, an electrolyzer section, gas separation, power transformer regulator, rectifiers, compressor system and the process efficiency ranges from 85 to 95% (Theodore, 2008). Here, the efficiency is the fraction of electrical energy used which is actually contained within the hydrogen. Some of the electrical energy is converted to heat, a useless by-product. About 4% of hydrogen gas produced worldwide is produced by electrolysis (Emmanuel et al., 2004). Electrolysis is considered as one of the cleanest method to produce hydrogen, when the required electricity is derived from renewable energy sources such as solar, geothermal and wind. Photo-electrolysis is another method, in which the photovoltaic cells act as electrodes that decompose water into hydrogen and oxygen gas. These methods of producing hydrogen are favourable to reducing the environmental impact and can be stored as hydrogen energy and used as fuel for vehicle or converted to electricity in fuel cells.

3.1.5 Thermochemical Water Splitting In thermochemical hydrogen production, water is decomposed into hydrogen and oxygen with the help of heat driven chemical reactions. When water and heat energy is given to the system, only hydrogen, oxygen, and waste heat are generated. In solar thermochemical hydrogen production, concentrated solar radiation is the energy source of high-temperature process heat for driving an endothermic chemical reaction. Almost 200 thermochemical cycles are available in the literature and these cycles are composed of a series of reactions which can help to attain to break water at lower temperatures as the temperature requirement for splitting of water directly into hydrogen and oxygen is too high to be practical (Serban et al , 2009). Due to economic reasons, not all the thermochemical cycles have proceeded towards experimental demonstrations. Cycles such as sulphur-iodine (S-I), copper-chlorine (Cu-Cl), cerium-chlorine (Ce-Cl), iron- chlorine (Fe-Cl), magnesium-iodine (Mg-I), vanadium-chlorine (V-Cl), copper-sulfate (Cu-SO4) and hybrid chlorine are commercially recognized after considering numerous factors like availability and abundance of materials, simplicity, chemical viability, thermodynamic feasibility and safety issues (Naterer et al ., 2008)

Sulfur–iodine and copper–chlorine water splitting cycles are the most promising methods of thermochemical hydrogen production. In the S–I and Cu–Cl cycles, heat is the energy input for splitting water to produce hydrogen rather than electricity. Moreover, both cycles have different requirements of heat quantity and source of heat flow and also different thermal efficiencies. There are different types of S-I cycles but the following three steps for thermal decomposition of water is common on most of the cycles (Wang et al. 2010)

Table 3.1: Common thermochemical decomposition steps in S-I cycles.

Steps Reactions Temperature (K)

Hydrolysis I2 (l +g ) + SO 2 (g) + 2H 2O (g) → 2HI ( g) +H 2SO 4 (l) (exothermic) 393

Oxygen Production H2SO 4 (g) → SO 2 (g) + H 2O (g) + 0.5O 2 (g) (endothermic) 1123

Hydrogen Production 2HI ( g) → I2 (g) + H 2 (g) (endothermic) 723

Similarly, there are also several types of the Cu–Cl cycle with various numbers of steps from 2 to 5 depending on reaction conditions (Lewis et al ., 2008). The cycle which involves five main steps in Cu-Cl are: (1) HCl (g) production using such equipment as a fluidized bed, (2) oxygen production, (3) copper (Cu) production, (4) drying and (5) hydrogen production.

Table 3.2: Steps and reactions in the five-step Cu-Cl cycle for thermochemical water decomposition. Steps Reactions Temperature (K)

H2 Production 2Cu ( s) + 2HCl ( g) → 2CuCl ( molten ) + H 2 (g) (exothermic) 723

Cu Production 4CuCl ( aq ) → 2Cu ( s) + 2CuCl 2 (aq ) 303-353

Drying 2CuCl 2 (aq ) → 2CuCl 2 (s) (endothermic) 372

2CuCl 2 (s) + H 2O ( g) → CuOCuCl 2 (s) + 2HCl Hydrolysis (endothermic) 648 (g)

Decomposition CuOCuCl 2 (s) → 2CuCl ( molten ) + 0.5O 2 (g) (endothermic) 773 (Source: Wang et al ., 2010)

3.2 Life Cycle Assessment Methodology Life cycle assessment (LCA) is a "cradle-to-grave" methodology for assessing products, systems and processes with the identification and evaluation of the environmental impacts associated with a product throughout its entire life cycle. The term "life cycle" denotes the main activities in the life-span of a specified product or process. In the LCA, the boundaries start with the gathering of raw materials from the earth to the final product when all materials are returned to the earth. Moreover, LCA assists the estimation of the hidden environmental impacts resulting from entire stages in a process, the impacts of which, are not often included in more traditional analyses (e.g., raw material extraction, material transportation, ultimate product disposal, etc.). This broad methodology provides a more accurate image of the true environmental balances. Figure 3.5 illustrates the general life cycle stages that are considered during analysis (Curran, 2006). Life cycle assessment is a systematic technique that consists of four main phases which are described by Curran (2012) and Figure 3.4 shows the phases of an LCA:

1. Goal and Scope Definition: This phase define the objective, intention and application of the product, process or activity. Moreover, it also explains the context in which the assessment is to be made and set the boundaries and environmental effects which are going to be reviewed for the assessment. 2. Inventory Analysis: The second phase collects an inventory of data of relevant energy and material inputs and environmental releases during the life cycle. This phase often takes more time and gathering information is difficult and not always available. 3. Impact Assessment: This phase evaluates the human and ecological impacts that are associated with identified inputs and environmental releases. 4. Interpretation: The final phase interprets and communicates the results of the assessment throughout the life cycle of the processes which are under consideration. It also classifies and understands the uncertainty and assumptions used to create the results. Moreover, it also discussed the recommendations to reduce the environmental impacts of products.

Goal and scope Inventory Impact definition Analysis Assessment

Interpretation

Figure 3.4: Phases of LCA (Modified from Curran, 2012).

3.2 LCA and International Standard Organization According to the International Organization for Standardization (ISO), LCA refers to the process of compiling and evaluating the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle (ISO 14044, 2006). The ISO has issued a series of standards and technical reports for life cycle assessment study which are referred to as the 14040 series of reports. This series consists of the documents listed in Table 3.3

Table 3.3: ISO Series for LCA

Number, Year Title Description ISO 14040 This document gives a general description and framework (1997) Principles and of LCA. It provides an overview of the practice, Framework applications as well as limitations of LCA ISO 14041 Goal and scope This gives the details of the procedure for goal and scope (1998) definition and definition including system boundary and the requirements inventory analysis for the conduct and critical review of inventory analysis. ISO 14042 This document provides guidance on the classification and (2000) Life Cycle Impact evaluation of the environmental impacts those results from Assessment the inventory analysis. Moreover, it initiate to introduce objectivity and uniformity to the impact assessment phase. ISO 14043 This document arranges the requirements for the analysis, (2000) Life Cycle interpretation and presentation of LCA results in relation to Interpretation the set goal and scope. It provides the requirement and guidance on the impact ISO 14044 Requirements and assessment as well as the nature and quality of data (2006) guidelines collected

(Source: Curran, 2012)

3.4 Impact Assessment The Life Cycle Impact Assessment (LCIA) involves the analysis and interpretation of the results of inventory analysis. It is the evaluation of potential human health and environmental impacts of the material and energy flows which are identified and released during the life cycle inventory (LCI). It develops a link between a process and its possible environmental impacts. Under the impact assessment, the important aspects of measuring environmental effects becomes significant such as the increase of carbon dioxide and other greenhouse gas emissions which have the potential to contribute to global warming.

Life cycle impact assessment also provides the basis for comparison. LCIA can determine the great potential impact among the pollutant emissions whereas inventory analysis measures the types and amounts of pollutant emissions. Processes like power generation, fuel production and other methods which have a global concerned of environmental release can be assessed by an LCIA. Moreover, the results of an LCIA provide a comparison of the relative differences in potential environmental impacts for each option.

Raw Material Inputs Acquisition Outputs

Energy Source Manufacturing Products

Wastes Transportation

Air Emissions Raw Material Use, Maintenance

Recycle, Waste Management

Figure 3.5: Inputs and outputs in LCA (Modified from Curran, 2006)

Note that the impact assessment can help decide which electricity generation option has the greatest potential to damage nature or contribute most to global warming (EPA, 2004). The basic structure of the impact assessment consists of the following:

1. Category Definition 2. Characterization 3. Normalization 4. Weighting

3.4.1 Category Definition Category definition considers categories to be analysed which have significant impact on the environment. These impact categories are recommended by the goal and scope of the study. The impact categories which are normally considered are: carcinogens, acidification, eutrophication, respiratory organics and inorganics, ozone layer, global warming/climate change, human toxicological impacts, land use, and work environment. Jensen et al. (1997) recommended building a relation to the characterization and study completeness, practicality, independence excluding dependent impact categories.

3.4.2 Characterization Characterization measure the quantity, which gives the comparative involvement of each input and output to the selected impact categories. The substances that contribute to an impact category are multiplied with a characterization factor that expresses the relative contribution of the substance. For itself it can be seen as a similarity factor. Such as, the characterization factor for CO 2 in the impact category climate change can be equal to 1, while the characterization factor of methane can be 21. This means the release of 1.0 kg of methane causes the same amount of climate change as 21 kg CO 2 (Mark et al. , 2010).

3.4.3 Normalization Several methods allow the impact category indicator results to be compared by a reference or normal value. This means the impact category is expressing potential impacts in ways that can be compared such as comparing the global warming impact of

CO 2 and methane for two alternative options. The reference may be chosen without restrictions, but sometime it is the average yearly environmental load in a country or continent, divided by the number of inhabitants is used as the reference.

3.4.4 Weighting Weighting is a subjective process and is not essentially based on scientific facts. Weighting highlights the most important potential impacts by assigning weights to different impact categories based on their perceived importance or relevance. Normalization and weighting take all environmental impacts and reduce them into a single score.

3.5 Advantages of LCA LCA can provide policy-makers with a unique technique to compare major environmental impacts. The distinctive feature of LCA is that it incorporates all processes and environmental emissions from the beginning of the extraction of raw materials to the final disposal of waste products. LCA encompasses a decision between two alternatives by determining the environmental impacts and shifting from one phase to another such as transfer of water base emissions to soil or air emissions and without the range of LCA, these transfers might be neglected. By performing an LCA, researchers can (Tupper, 2002):

• Identify impacts to one or more specific environmental areas of concern. • Develop a systematic evaluation of the environmental consequences associated with a product. • Measure environmental releases to air, water, and land in relation to each life cycle stage and/or major contributing process. • Assist in classifying significant shifts in environmental impacts between life cycle stages and environmental media. • Measure the human and ecological effects of material consumption and environmental releases to the local community, region, and world. • Compare the health and ecological impacts between two or more rival products/processes or identify the impacts of a specific product or process.

Systems Studied In this study, various hydrogen production systems are studied in order to compare them on the basis of environmental impact and efficiency. There are hundreds of methods available for hydrogen production but we categorized them on the basis of energy sources such as the energy from the fossil fuel source, renewable energy and the nuclear energy sources. Figure 4.2 to Figure 4.4 show different hydrogen production approaches on the basis of energy source and technology. This chapter presents the methods for comparison which we have considered for hydrogen production. The LCA of hydrogen production via steam reforming of natural gas has been done by several researchers and organizations. However, this study will compare SMR with other methods by utilizing renewable energy sources such as wind electricity, solar photovoltaic and nuclear energy. This study quantifies and analyses total environmental aspects of producing hydrogen via different sources. LCA is a “cradle to grave” approach, for this reason, energy requirement and production for each process is examined so that total environmental scenario and efficiencies could be presented. The general system boundaries for LCA are shown in Figure 4.1.

Figure 4.1: System boundaries for life cycle assessment

Photo- Catalysts Catalysts electrons Solar 10 catalysis Photonic +photo-initiated +photo-initiated Photo- Solar 9 Photonic + electricity + electrolysis

Photo electrodes electrodes Photo

2 H → PV- Water Water Solar 8 Electrical PV Panels + + Panels PV electrolysis electrolyzer O+ 2 High Heat H Solar 7 Electrical Electrolysis Temperature Temperature Electricity+

C +C 2 →

2H 4 Solar 6 Electrical CH Electricity + Electricity Plasmaarc decomposition Hydrogen Renewable O+ 2 H Solar 5 Electricity Electrical Electrolysis Renewable solar based hydrogen production approaches production hydrogen based solar Renewable : 2 . 4 Electricity Hybrid Hybrid Thermal + Solar 4 Thermal Na-Cl, Na-OH Water Splitting withCu-Cl, S-I, Thermochemical Figure Figure Solar 3 Thermal Na-Cl, Na-OH Na-OH Na-Cl, Water Splitting Splitting Water with Cu-Cl, S-I, S-I, Cu-Cl, with Thermochemical 2 2 H O OH+H H + O + H → → → → 2O 2H 2H O Solar 2 2 Thermal OH OH H Thermolysis H2 + S + H2 → Solar 1 S S Cracking S S Thermal 2 2 H H Thermocatalysis

O+ 2 High Heat H Wind2 Electrical Electrolysis Temperature Temperature Electricity+ O +O 2

H Wind1 Electrical Electricity Electrolysis

2 H → PV- Water Water Electrical PV Panels + + Panels PV electrolysis Geothermal7 electrolyzer O+ 2 High Heat H Electrical Electrolysis Temperature Temperature Electricity+ Geothermal 6

Hydrogen C +C 2 Renewable →

2H 4 Electrical CH Electricity + Electricity Plasmaarc Geothermal5 decomposition Geothermal and wind based hydrogen production hydrogen wind based and Geothermal : 3 . 4 O+ 2 H Electrical Electricity Figure Figure Electrolysis Geothermal4 2 2 H O OH+H H + O + H → → → → 2O 2O 2H 2H O 2 Thermal OH OH H Thermolysis Geothermal3 H2 + S S + H2 → S S Cracking S S Thermal 2 2 H H Geothermal2 Thermocatalysis Electricity Hybrid Thermal + Thermal Na-Cl, Na-OH Water Splitting withCu-Cl, S-I, Geothermal 1 Thermochemical

High High Heat High Water + + Water Electrolysis Temperature Temperature Electric Power Electric Temperature electrolyte +Heat electrolyte Cu-Cl, Heat High S-I, Na-Cl S-I, Na-Cl Nuclear Nuclear Electric Power Electric chemical cycle chemical Temperature Water + + Water electrolyte +Heat electrolyte Hybrid Thermo-

Heat High Na-OH O+Cu-Cl, Thermo- 2 S-I, Na-Cl, S-I, Na-Cl, H Electric Power Electric Temperature chemicalcycle 2 + 2 CO CO + CO

CO +H CO → → 2 2 → H O 2 Heat O 2 Coal Thermal C C +1/2O CO +H CO C C +H Gasification Hydrogen

Fossil Fuels Fossil → 2 O 2 + 4H + 2 + 2H + 4 Steam CO Thermal Reforming Naturalgas CH Fossil and nuclear based hydrogen production hydrogen based nuclear and Fossil : 4 . 4

2 2 → O +H 2 2 2 CO +H CO CO → Figure Figure → O 2 +1.26H +2.21H O 2 2 0.7 O CO Thermal 1.9 Pyrolysis Biomass 3 CO CO +H CH Bio-oil+H

2 →

2 + CO + 2 Biomass Biomass Thermal + Energy + Biomass 2 Gasification CO + H + CO Biomass O + Biomass Renewable + + 2 H

2 → CO bacteria + + bacteria Biomass 1 Fermentative Fermentative Biochemical Biomass Biomass Dark Fermentation Dark

4.1 Hydrogen Production from Steam Methane Reforming The most common method of producing hydrogen is steam reforming of natural gas and therefore this study analyzes this process first. For hydrogen production from steam methane reforming, the method is divided into a basic subsystem which is shown in Figure 4.5 The cycles and data used in the study are obtained from several studies in the literature such as Spath et al. (2001, 2004), and Ray (2010). The process starts in reforming reactor where natural gas and steam react under high temperature and pressure. After the reaction, the products passed through high and low temperature shift reactor where water-shift gas reaction occurred to produce more hydrogen. Finally, the separation of hydrogen from CO2 takes place by the process called pressure swing adsorption method. The system considered here depicts a true picture of SMR plant except several assumptions. The energy, raw material and other basic necessities are assumed for the production of 1 kg of hydrogen.

Flue Gas Natural Gas

CO 2

Steam

Reforming High Low Reactor Hydrogen Temperature Temperature Purification Shift Reactor Shift Reactor Hydrogen

Figure 4.5: Steam methane reforming and water gas shift reaction (Modified from Spath et al ., 2001).

The calculated commodities for 1 kg of hydrogen are shown in Table 4.1. The input values calculated on the basis of the available data such as Spath et al. (2001) which is similar to the typical plant available at today’s major oil refineries. The considered

37 hydrogen plant which has a production capacity of 135000 kg per day and the purity of hydrogen on industrial grade is about 99 mol% H 2.

Table 4.1: Data inputs and assumption for 1 kg of hydrogen production via steam methane reforming

Plant Inputs Values Hydrogen Purity Industrial grade ( >99.95% mol% H 2) Natural gas requirement (methane) 3.4 kg Steam requirement 9.4 kg Electricity consumption 1.13 MJ

4.2 Hydrogen Production via Chlorine Electrolysis Using Different Cells Electrolysis is another method of producing hydrogen using different chemicals. In this system, Na-Cl and Na-OH is used for electrolysis using different cells. Hydrogen is produced by the electrolysis of salt solution. Technologies which are mainly used are mercury, diaphragm and membrane cell electrolysis. Each of these technologies signifies a different method to deposit the produced hydrogen at the cathode separate from the chlorine produced at anode. In all of the cell technologies the following basic principle is used. At cathode: In a diaphragm and membrane cells, water decomposes to form - hydrogen (H 2) and hydroxide ions (OH ). In the mercury cell, a sodium/mercury amalgam is formed at anode. This reacts with water in the decomposer cell at cathode to form H 2 and OH -. The chemical reaction at the cathode is:

+ - + - 2 Na (aq) + 2H 2O(l) + 2 e H2(g) + 2 Na (aq) + 2 OH (aq) (4.1)

At anode: chlorine is formed at anode by oxidized chlorine ions and the chemical reaction is given by:

- - 2 Cl (aq) Cl 2 (g) + 2 e (4.2)

4.2.1 Mercury Cell Electrolysis A mercury cell comprises two cells: the electrolyser and the decomposer as shown in Figure 4.6. Anodes are generally composed of graphite or titanium and a mercury cathode which flows along the bottom of the cell. When a direct electric current flows on a salt

38 solution, chlorine is liberated at the anode while sodium dissolves into the mercury cathode to form an amalgam. In the decomposer, the hydrogen and a 50% sodium hydroxide solution is produced when amalgam reacts with water. The regenerated mercury is reverted to the electrolyser and this whole process is very energy intensive.

Figure 4.6: Hydrogen production via Na-Cl electrolysis using mercury cell (Adapted from Ecoinvent report , 2007) 4.2.2 Diaphragm Cell Electrolysis This technology mainly developed in the U.S at the end of 19 th century. It consists of a cell with a typically asbestos diaphragm applied to an iron grid cathode which prevents the chlorine and sodium hydroxide from mixing. Again, hydrogen is produced together with the formation of sodium hydroxide. This method requires less energy than mercury cell; however the sodium hydroxide solution has a concentration of only 10 to 12%.

Figure 4.7: Diaphragm cell electrolysis (Adapted from Ecoinvent Report , 2007)

4.2.3 Membrane Cell Electrolysis In membrane cell electrolysis which was developed around 1970, the cell is separated into two sections by a membrane that performance as an ion exchanger. Initially, the ionic compartment is filled with saturated salt brine and the cathode department filled with only water. The main advantages of membrane type electrolysis is their moderate energy consumption which is less than the diaphragm cell, more pure sodium hydroxide is produced in this technology as compared to the diaphragm cell and very small amount of environmental impacts such as no Hg and asbestos emissions.

Brine is a basic chemical used in the production of hydrogen through electrolysis. Before electrolysis, all three types of cells require few similar supplementary processes for preparation of the brine. The preparation of the salt brine can be divided in the following steps:

Figure 4.8: Membrane cell electrolysis (Adapted from Ecoinvent report , 2007) Brine production : Generally fresh salt is dissolved in water or in depleted brine from mercury or membrane process. So the basic raw material is solid salt.

Brine purification : After the brine production step brine purification is require to remove undesirable elements from the brine that affect the electrolytic process. Different chemicals are added to eliminate the various undesirable components specially, for the membrane cell, a more precise purification is needed and therefore this technology has a

40 second purification step composed of a filter and a softening step using an ion exchange unit.

Brine re-saturation : In a recirculation circuit, the brine leaving the electrolysis cell is first de-chlorinated which is the extraction with air in case of mercury and membrane cells, then the saturation with salt is prepared. In case that impure salt is used, the pH of the solution is brought to an alkaline level with caustic soda which helps to reduce the solubility of impurities. However, in order to protect the anode coating, hydrochloric acid is added to bring the pH to an acidic value. This process sometime produces carbon dioxide emissions in cases where carbonates are introduced into the brine as impurities of the added salt. The process can occur in open or in closed vessels. After the electrolysis, the final products are hydrogen, chlorine and sodium hydroxide which are separated through several processes. Hydrogen leaves the cell with high concentration, therefore does not require major process. It is just cooled in order to remove moisture and other small impurities such as Na-OH, salt and Hg in case of mercury cell.

4.3 Hydrogen Production via Wind Based Electricity The wind energy capacity around the world has been growing at an annual rate of 28% (Rifkin, 2002). According to the European Wind Association, wind energy can produce about 10% of electricity around the world by 2020. The wind/electrolysis system studied here is the same as Na-Cl electrolysis but electricity used in this system is renewable and generated from wind turbine. In case of wind, the kinetic energy per unit mass of air in motion is proportional to the square of its velocity. The electricity from the wind power plant is wheeled to a hydrogen production system where the electrolyzer converts the electricity to hydrogen. The power depends upon energy multiplied by the mass flow rate of the air which gives the cubic relationship between the power and the wind velocity. Figure 4.9 shows the simple wind turbine electricity flow for hydrogen production.

Water (H2O)

Electrolyser

Figure 4.9: Wind electrolysis system An eco-invent model is used for the electrolysis system for wind generated electricity from an 800 kW wind power plant. In the, electricity is wheeled from the wind power plant to system where the electrolyzer converts the electricity to hydrogen. Some electrical losses were neglected from the final electricity produced by the wind turbines. Such as the transmission losses, electricity needed, to pump the deionized water and finally, the power requirement for compression of the product hydrogen.

4.4 Hydrogen Production via Solar Photovoltaic Based Electricity Solar radiation is a source for renewable energy. One possible use is the production of electricity in photovoltaic appliances (PV) for hydrogen production. The most common method of solar based hydrogen production uses photovoltaic cells in combination with water electrolysis. In solar photo photovoltaic based hydrogen production, electricity requirement is fulfilled by solar photovoltaic electricity. In this study all the inputs and system requirements are similar as sodium chlorine electrolysis as we have used similar system for hydrogen production but electricity is obtained from solar photovoltaic cell instead of fossil fuel electricity from grid. PV cells are used to create electrical energy.

Photovoltaic cells convert photon energy into electrical energy. During conversion two conditions exist inside a PV material: the striking light energy must be sufficiently high to break a chemical bond in the material and thus create a free electron/hole pair, and the presence of an electrical asymmetry in the form of a p–n junction.

Figure 4.10: Schematic of solar photovoltaic based electricity (Dincer and Joshi , 2013)

Analyses

In this section, systems are analysed on the basis of LCA, energetically and exergetically. For the life cycle analysis, only environmental impacts are considered in each process mentioned here. For the goal and scope of the life cycle analysis, the functional unit is to produce one kg hydrogen. So, all calculations will be based on 1 kg hydrogen production. Moreover, some inputs and outputs data are obtained from literature for the processes. This chapter provides the inventory data which are overall inputs and outputs of all steps. The reference data obtain from different literature is used to calculate the basic requirement for the processes. Environmental impacts, energy and exergy efficiencies are calculated for the studied systems. The following assumptions are made for analyses:

• The reference environment temperature (T0) and pressure (P0) are 25°C and 1 atm, respectively. • The processes are adiabatic. • The analysis considers one kg of hydrogen produced per system, so all emissions and other quantities are provided in terms of per kg of hydrogen produced. • All processes occur at steady state. • The natural gas is composed of methane, ethane, propane, butane, hydrogen sulphide and other gases. Only methane gas is used in the LCA analyses.

5.1 Environmental Impacts Assessment using LCA

For the environmental impacts calculation, the LCA software, SimaPro, is used which contains a number of impact assessment methods. In this study, the Eco-indicator 99 is used which has the damage-oriented approach (Mark et al ., 2010). Impact categories are expressed in terms of three damage categories:

1. Damage to human health ; this category is responsible for damage to human health which is expressed as the number of year life lost and the number of years lived disabled. The index used to evaluate is called as Disability Adjusted Life Years (DALYs) which is also used by other international organization such as the World Bank and World Health Organization (WHO).

2. Damage to ecosystem quality ; this damage is responsible for destroying our ecosystem in terms of loss of species over certain region and time. This damage is expressed in Potentially Disappeared Fraction (PDF*m 2*year) per kg of emission. 3. Damage to resources; the surplus energy required for the extractions of minerals and fossil fuel in future. It expressed in MJ of surplus energy.

These damages are further divided to other impact categories such as emissions, land use and resource depletion.

5.1.1 Emissions All the emissions which come under damage to human health, damage to ecosystem and the damage to resources are also analysed. Following are the impact categories for the emissions:

• Carcinogens : Carcinogenic affects due to emissions of carcinogenic substances to air, water and soil. Damage is expressed in DALY/ kg emission • Respiratory Organics : Respiratory effects resulting from summer smog, due to emissions of organic substances to air, causing respiratory effects. Damage is expressed in DALY / kg emission. • Respiratory Inorganics: Respiratory effects resulting from winter smog caused by emissions of dust, sulphur and nitrogen oxides to air. Damage is expressed in DALY / kg emission. • Climate Change : Damage, expressed in DALY/kg emission, resulting from an increase of diseases and death caused by climate change. • Radiation: Damage expressed in DALY/kg emission, resulting from radioactive radiation. • Ozone layer: Damage expressed in DALY/kg emission due to increased UV radiation as a result of emission of ozone depleting substances to air.

The effect score for ozone layer depletion is given kg as calculated by

Ozone layer depletion (kg) = (ODP (ozone depletion potential) × airborne emission (kg)) 4

• Ecotoxicity : It is responsible to cause damage to ecosystem quality, as a result of emission of ecotoxic substances to air, water and soil.

Damage is expressed for per kg of emission:

= Potentially Affected Fraction (PAF) × area × time = PAF × m2 × year

• Acidification/ Eutrophication : Damage to ecosystem quality, as a consequence of emission of acidifying substances to air. They are produced by depositions of inorganic substances into the water and through the air affecting the soil. The source of the damage is due to several sulphates, nitrates and phosphates.

Damage is expressed for per kg of emission:

= Potentially Disappeared Fraction (PDF) × area × time = PDF × m2 × year

• Land Use : The impact of a land use on the environment also affects the surrounding regional area with the local area used because the number of species increases with area size. Damage cause by land use is expressed in Potentially Disappeared Fraction (PDF) multiplied with the area and time span:

EQ = PDF × area × time = × × where S ref is the species diversity on the reference area type, Suse is the species diversity 2 on the converted or occupied area, A is the area in m , and T is the time in years

5.1.3 Resource Depletion In the extraction of resources, the best quality resources are in general extracted first and the remaining lower quality resources are kept for future extraction. These resources will create more problems which will be experienced by future generations, as they will have to use more effort to extract remaining resources. This extra effort is expressed as “surplus energy”.

• Minerals : Surplus energy per kg mineral or ore, as a result of decreasing ore grades.

• Fossil Fuels : Surplus energy per extracted MJ, kg or m 3 fossil fuel, as a result of lower quality resources.

5.2 Analysis of Hydrogen Production via Steam Methane Reforming Analysis of hydrogen production from SMR is presented here. Only methane gas is assumed in our LCA analyses. For 1 kg of hydrogen the energy requirement from natural gas to hydrogen plant is about 159.6 MJ (Spath et al., 2001). So the amount of methane can be calculated as follows:

Energy in the natural gas to hydrogen plant = 159 MJ / kg of H 2

For 1 kg of methane = 47.13 MJ (LHV)

The amount of methane required for 1 kg of H 2 is

= 159.6 MJ /47. 13

= 3.4

The steam requirement for hydrogen plant which has a capacity of 135000 kg/day is about 1290 ton per day.

So, the amount of steam required for 1 kg of hydrogen is

= / 135000 1290

= 9.5

The electricity requirement for the hydrogen production is also fulfilled by consuming natural gas and the impact flow diagram for 1 kg of hydrogen is shown in Figure 4.7. The electricity requirement for assumed plant is about 153000 MJ per day, so for 1 kg of hydrogen it is calculated as:

= MJ kg 153000 day /135000 day

Therefore, the electricity requirement for 1 kg of hydrogen is

= MJ 1.13 kg of hydrogen

The consumption of raw material inputs, energy and other chemicals for the production 1 kg of hydrogen the environmental impacts are shown in Table 5.1. The water consumption is divided into water gas shift reactions and steam production.

Table 5.1: Raw material inputs for the production of 1 kg of hydrogen

Inputs Amount Unit Coal, hard (in ground) 159.2 gram Crude oil (in ground) 16.4 gram Iron ore (in ground) 10.3 gram Limestone (in ground) 16 gram Water unspecified natural origin 0.0198 m3 Water consumed in reforming and shift reactions 0.0048 m3 Water consumed in steam production 0.0141 m3 Natural gas, at production 5 m3 Electricity, production mix 0.314 kWh Steam 8 Kg

5.2.1 Energy and Exergy Efficiencies Energy and exergy analyses were performed on the steam methane reforming process. The general equation for energy efficiency is defined as:

(5.1) η = The hydrogen plant energy efficiency is defined as the total energy produced by the hydrogen plant divided by the total energy input to the plant which is determined by the following formula energy.

(5.2) η =

The performance of a system is usually assessed by the thermal efficiency of the system. The thermal efficiency of the system is based on a first-law energy balance and is given by:

(5.3) η = 48

The exergetic efficiency of the system is given by using the same formula as for energy efficiency but in this case the exergetic LHV value is used for hydrogen and natural gas. Moreover, in the calculation of pump and compressor work input exergy analysis is also applied. The exergetic efficiency of the steam methane reforming for hydrogen production is given as follows:

(5.4) =

In SMR of natural gas to produce hydrogen, energy input considered here comes in two forms. First is the energy content in methane gas and we have considered LHV value for methane in our system. Second energy considered here comes in form of electricity which is utilized to operate pumps and compressor in the plant. The hydrogen production process begins by compressing the natural gas and pumping the inlet water to the reformer.

For steady-state process, respective general balances for mass, energy and exergy can be written as follows:

(5.5) ∑ = ∑ (5.6) ∑ + = ∑ + (5.7) ∑ + ∑ 1 − = ∑ + +

Applying the balance equations on the pump of the water gas shift reaction, it gives mass balance equation:

(5.8) , = ,

Energy balance equation for the pump of the of the water gas shift reaction can be written as

(5.9) , ℎ, + = , ℎ,

The exergy balance equation for the pump used in SMR can be written as

(5.10) , , + = , , + ,

Methane gas is utilized as source of hydrogen production and dissociate when react with high pressure and temperature steam in reformer. The hydrogen production process starts from compressing the natural gas to the reformer. The mass balance equation for compressor is given as follows:

(5.11) , = ,

Energy balance equation for the compressor of the reformer can be written as

(5.12) , ℎ , + = , ℎ ,

Similarly, the exergy balance equation for the compressor of reformer can be written as

(5.13) , , + = , , + , 5.3 Analyses of Hydrogen Production Methods through Electrolysis Using Different Cell Analyses for hydrogen production through electrolysis of sodium chloride (Na-Cl) are presented here. The material consumption for the production of 1 kg of hydrogen through Na-Cl electrolysis is obtained from the library of SimPro and several other literatures. Different types of salts are used in the preparation of the salt brine which is utilized within the electrolysis cell such as vacuum crystallized salt from solution-mining, rock salt and solar salt. Another, essential raw material used in the hydrogen production through electrolysis is water. In the process, water is used in different unit such as in the preparation of the brine and for keeping the water ratio in the reaction to produce sodium hydroxide. Moreover, water is also used in the chlorine absorption unit. Water and salt consumption in the production of 1 kg of hydrogen is shown in Table 5.2.

Table 5.2: Water and salt consumption in different cells

Resource (g/kg of H 2) Mercury Cell Diaphragm cell Membrane Cell Salt 1750 1750 1750 Water 1.9 1.9 1.9

In the examined method, the input values of other materials for 1 kg of hydrogen used in the system is shown in Table 5.3. Materials consumed in the system have particular use in the process, such as soda powder used in the precipitations of calcium ions, barite used in the precipitation of sulphates, calcium chloride used in the precipitation and elimination of sulphates, hydrochloric acid and sodium sulphite used in the de-chlorination of brine, sodium hydroxide is used to remove magnesium and heavy ions.

Table 5.3: Input values of chemical and materials used in electrolytic hydrogen production

Materials per kg of Unit Mercury Cell Diaphragm Cell Membrane Cell hydrogen Sodium chloride kg 0.9125 0.9125 0.9125 powder Asbestos g . 0.2 - Mercury mg 3.133 - - Soda powder kg 0.00533 0.00533 0.00533 Barite kg 0.001625 0.001625 0.001625 Calcium chloride kg 0.00826 0.00826 0.00826 Hydrochloric acid kg 0.0116 0.0116 0.0116 Sodium sulphite g 0.1 0.1 0.1 Sodium hydroxide g 3 2 20

The energy consumption in the electrolytic hydrogen production varies with types of cells used. Table 5.4 gives an overview of the energy demand in different electrolytic cells.

Table 5.4: Energy consumption for the production of hydrogen in different electrolytic cells

Energy (kwh/kg of hydrogen) Mercury Cell Diaphragm cell Membrane cell Electricity 1.65 1.38 1.29 Heat (steam) - 0.61 0.18

5.4 Analyses of Hydrogen Production through Electrolysis Using Wind Electricity In the analyses of hydrogen production from electrolysis by using wind power plant electricity, all data used is similar as Na-Cl electrolysis except electrical energy. In this analysis, fossil fuel electrical energy is now replaced by electricity which is generating

51 from renewable wind energy. In the development of wind based electricity, a wind power plant is considered which have a capacity of 800kW. The electricity from the wind power plant is wheeled to a hydrogen production system where the electrolyzer converts the electricity to hydrogen. The inputs and raw material utilization in the arrangement of wind based electricity is shown in Table 5.5

Table 5.5: Material and energy consumption in wind power plant

Material Amount Unit Electricity, medium voltage 17500 kWh Aluminium 207 kg Cast iron 6480 kg Chromium steel 14500 kg Copper 1460 kg Glass fibre reinforced plastic 9660 kg Lead 0.5 kg Lubricating oil 58.8 kg Polyethylene, HDPE, granulate 621 kg Polypropylene, granulate 20 kg Polyvinylchloride, bulk polymerised 434 kg Steel, low-alloyed 3750 kg Synthetic rubber 100 kg Tin, at regional storage 0.5 kg Section bar rolling, steel 10200 kg Sheet rolling, aluminium 207 kg Sheet rolling, chromium steel 14400 kg Wire drawing, copper 1460 kg

5.4.1 Energy and Exergy Efficiencies The energy analysis of wind turbine system depends on several factor such as the wind velocity, and the area of wind turbine. The mass of air passes through the wind turbine which causes the rotation of the blade and the conversion of kinetic energy to electrical energy occurred. The mass of air is conserved in the wind turbine, so the mass balance equation for the wind turbine can be written as

(5.14) , = , where

(5.15) =

The energy balance equation for the wind turbine is the energy in the incoming air stream striking the wind turbine and leaving after certain change in temperature and velocity. The output of the wind turbine is electricity which is a function of voltage and current. Ghosh et al. (2014) analyse the wind turbine and their energy balance on wind turbine is given as

(5.16) ∆ = ( − )

The exergy balance equation of the wind turbine for hydrogen production can be written as

(5.17) = + ( − ) + ( − − )

The energy efficiency of the wind turbine is the useful work output from the turbine to the input energy to run the turbine and it can be written as

, (5.18) = where (5.19) , = and (5.20) =

Here, the area of wind turbine can be calculated by simple mathematical formula and can be written as

, D is the diameter of the rotor. =

The energy efficiency of the wind based hydrogen production system is the amount of energy content in the produced hydrogen to the energy input to the system in terms of wind electricity and sodium chloride powder which can be written as

(5.21) , =

The exergy efficiency of the system of hydrogen production using renewable wind based electricity can be written as

(5.22) =

1 MJ Electricity, at 0.0006 Pt

9.92E-9 p 4.94E-9 p Wind power Wind power 0.000454 Pt 0.00014 Pt

0.000152 kg 1.57E-5 kg 9.58E-5 kg 0.000384 kg Chromium Copper, at Glass fibre Steel, 0.000226 Pt 0.000114 Pt 7.66E-5 Pt 0.000104 Pt

9.58E-5 kg 5.63E-5 kg 2.66E-6 kg 0.000101 kg 0.000242 kg Steel, Steel, Copper, Nylon 66, Steel, 0.00014 Pt 8.1E-5 Pt 6.13E-5 Pt 6.36E-5 Pt 8.31E-5 Pt

4.82E-5 kg 6.02E-5 kg 1.01E-5 kg 0.000416 kg Ferrochromi Ferronickel, Copper Pig iron, at 9.2E-5 Pt 0.000165 Pt 5.25E-5 Pt 5.72E-5 Pt

0.00171 kg Disposal, 7.52E-5 Pt

Figure 5.1: Impact flow diagram of wind power plant.

5.5 Analyses of Hydrogen Production through Electrolysis Using Solar Photovoltaic Electricity In the analysis of hydrogen production from electrolysis by using solar photovoltaic electricity, all data used is similar as Na-Cl electrolysis except electrical energy. In this analysis, fossil fuel electrical energy is now replaced by electricity which is generating from renewable solar energy. In the development of solar based electricity, a solar power plant is assumed to have power production of 1 kWh. The electricity from the solar photovoltaic is brought to a hydrogen production system where the electrolyser converts the electricity to hydrogen with other chemical reaction. The inputs and raw material utilization in the solar based hydrogen production is shown in Table 5.6

Table 5.6: Inputs to solar photovoltaic based hydrogen production

Materials per kg of hydrogen Amount Unit Sodium chloride, powder 0.8125 kg Soda, powder 0.0053 kg Barite 0.0016 kg Calcium chloride, CaCl2 0.0083 kg Hydrochloric acid, 30% in H2O 0.0011 kg Sulphite 4.643E-05 kg Sodium hydroxide, 50% in H2O 0.0195 kg Electricity, photovoltaic 1.2940 kWh Tap water 0.0037 kg

5.5.1 Energy and Exergy Efficiencies The energy analysis of solar photovoltaic system depends on several factor such as the solar radiation and the area of solar panel. All the solar radiation emitted from the sun is assumed to be incident on the panel. Since no mass exchange occurs at the boundary of the photovoltaic panel, therefore, the input to the concentrator is fully defined by expressing its energy and exergy equation which can be written as

= (5.22) where; is the energy with respect to solar radiation entering the system, is the total effective area of the panel and is the direct solar radiation intensity from

55 the sun which can be obtain from standard solar spectrums if the total intensity of a location is known. The exergy equation of the solar panel can be written as

= (1 − ) (5.23)

The energy efficiency of the solar based hydrogen production system is the amount of energy content in the produced hydrogen to the energy input to the system in terms of solar photovoltaic electricity. The energy efficiency of the solar based hydrogen production can be written as:

, = (5.24)

The exergy efficiency of the solar based hydrogen production is also the amount of exergy content in the produced hydrogen to the input exergy of the system which can be written as:

= (5.25)

Results and Discussion This chapter consists of the results from the analysis showed in the previous chapter. In addition, there are some further discussions and comparisons among the systems described. The results and discussion are divided according to the system studied. Under each system, environmental results are discussed and then thermodynamic analyses results are presented. The environmental results are calculated using two methods such as the Eco-indicator 99 (H) and CML 2001. Impact categories of both methods are considered in each hydrogen production method considered in the previous chapter. Thermodynamic analyses results of the methods are also discussed in terms of energy and exergy efficiencies. 6.1 Hydrogen via Steam Methane Reforming 6.1.1 Impact Assessment Results In the analysis of the hydrogen production from steam methane reforming, the method is divided into four sections in order to see the environmental impact of each section through several impact categories. Figure 6.1 shows the impact flow diagram of hydrogen production via steam methane reforming. In that flow diagram, maximum parts to the environment are due to the utilization of natural gas. Four sections which are evaluated here are hydrogen production, natural gas, electricity production and steam production for the process. Table 6.1 shows the damage assessment results for producing 1 kg of hydrogen using the Eco-indicator method. For better presentation of the result, these numeric values are plotted as bar chart in terms of percentage. Figure 6.2 shows the chart diagram of damage assessment of producing 1 kg of hydrogen SMR. Table 6.1: Damage assessment for 1 kg of hydrogen via steam methane reforming Impact category Unit Hydrogen Natural gas Electricity Steam Carcinogens DALY 3.50×10 -9 1.57×10 -8 5.56×10 -8 5.49×10 -8 Resp. organics DALY 2.29×10 -8 3.29×10 -8 6.65×10 -11 9.64×10 -10 Resp. inorganics DALY 1.83×10 -6 8.4×10 -8 1.24×10 -7 5.69×10 -7 Climate change DALY 1.73×10 -6 6.10×10 -7 4.95×10 -8 4.64×10 -7 Radiation DALY 0 3.27×10 -10 1.46×10 -9 6.76×10 -10 Ozone layer DALY 0 3.09×10 -9 6.56×10 -12 2.88×10 -10 Acidification PDF* m 2yr 8.02×10 -2 4.64×10 -2 0.0004 0.0147 Land use PDF* m 2yr 0 3.90×10 -2 0.188 0.0014 Minerals MJ surplus 2.99×10 -4 3.42×10 -3 7.3×10 -4 3.33×10 -3 Fossil fuels MJ surplus 1.28×10 -1 30.1 0.135 4.98

The hydrogen production process has maximum impact on the environment in terms of climate change, respiratory inorganics, organics and acidification which covers 60%, 55%, 40% and 55% respectively. Natural gas utilization in the process has maximum effect in the ozone layer which is 90% among the different sectors and about 85% in fossil fuels which has a value in the Table 6.1 of 30 MJ surplus. This surplus energy shows that a large amount of better quality natural gas is extracted for hydrogen production and that the rest is left for future extraction and use. Moreover, natural gas contribution in land use, minerals and respiratory inorganics is also worthy of mention here. The land use impact of natural gas is about 75% ( 3.90×10 -2 PDF*m 2 yr) which is affecting local and surrounding regions. The electricity used in the process has maximum points on radiation and carcinogenic categories which is about 60% (1.46 ×10 -9 DALY) and 42% (5.56 ×10 -8) respectively, among different section of the process. In the steam production minerals and energy are used and because of this utilization it has emissions almost in all impact categories but carcinogens, minerals and ecotoxicity are worthy of mention. About 75% (3.57 ×10 -2 PDF*m 2yr) of ecotoxicity is due to steam production and about 40% for carcinogens and minerals.

Table 6.2: Weighting results for 1 kg of hydrogen via steam methane reforming

Impact Category Unit Total Hydrogen Natural gas Electricity Steam Total Pt 1.64 1.34×10 -1 1.25 1.39×10 -2 2.40×10 -2 Carcinogens Pt 4.44×10 -3 1.20×10 -4 5.39×10 -3 1.90×10 -3 1.88×10 -3 Resp. organics Pt 1.95×10 -3 7.85×10 -4 1.12×10 -6 2.27×10 -6 3.30×10 -5 Resp. inorganics Pt 0.115 6.26×10 -2 2.88×10 -2 4.23×10 -3 1.95×10 -3 Climate change Pt 9.79×10 -2 5.94×10 -2 2.09×10 -2 1.69×10 -3 1.59×10 -2 Radiation Pt 8.42×10 -5 0 1.12×10 -5 4.99×10 -5 2.31×10 -5 Ozone layer Pt 1.16×10 -4 0 1.06×10 -4 2.25×10 -7 9.85×10 -6 Ecotoxicity Pt 3.04×10 -3 2.69×10 -7 3.457×10 -3 2.01×10 -4 2.49×10 -3 Acidification Pt 1.02×10 -2 5.60×10 -3 3.24×10 -3 2.80×10 -4 1.03×10 -5 Land use Pt 3.59×10 -3 0 2.73×10 -3 1.31×10 -4 7.29×10 -4 Minerals Pt 3.09×10 -4 1.19×10 -5 1.35×10 -4 2.90×10 -5 1.33×10 -4 Fossil fuels Pt 1.40 5.10×10 -3 1.19 5.36×10 -3 0.198

Among all impact categories presented in damage assessment have values based on their units and different categories. Weighting expressed these results as a single part irrespective of their category. Figure 6.3 shows the weighting results for 1 kg of hydrogen

58 via steam methane reforming which tells that in this process major impact on environment is due to the natural gas consumption and steam production. In terms of impact categories, fossil fuels have maximum number of parts for natural gas which is 1.2 and for steam is about 0.2.

Table 6.3: Contribution of process to total environmental impact for steam methane reforming (CML method)

Impact category Unit Total Hydrogen Natural gas Electricity Steam Abiotic depletion kg Sb eq 0.130 0.0025 0.1088 0.0018 0.0179 Acidification kg SO 2-eq 0.028 0.0176 0.0042 0.0018 0.0054 Eutrophication kg PO 4-eq 0.003 0.0016 0.0012 0.0004 0.0004 Global warming kg CO2 eq 11.956 7.426 2.1542 0.2287 2.1474 Ozone layer kg R-11 eq 3.0×10 -6 0 2.65×10 -6 1.9×10 -9 3.5×10 -7 Human toxicity kg 1,4-DB eq 3.2 2.675 0.033 0.0541 0.4084

The same process is also analysed by using the CML 2001 method. The CML 2001 impact categories which are abiotic depletion (AD), acidification potential (AP), eutrophication potential (EP), global warming potential (GWP), ozone layer depletion potential (ODP) and human toxicity potential (HP) are taken into consideration. Again, natural gas consumed in the hydrogen production by this process has maximum percentage in abiotic depletion of 0.1088 kg Sb eq and ozone layer depletion 2.65E-06 kg R-11 eq. Figure 6.4 also shows that the steam consumed in the steam methane reforming has minimum emissions in all six impact categories as followed by the electricity consumption. Table 6.3 has the numerical values for each category along with units for comparison.

1 kg Hydrogen, 1.64 Pt

5 m3 9.5 kg Natural gas, Steam, for 1.25 Pt 0.24 Pt

19.6 MJ 24.8 MJ 5.99 MJ Natural gas, Natural gas, Heavy fuel 0.147 Pt 0.175 Pt 0.0648 Pt

24.8 MJ 0.156 kg Natural gas, Heavy fuel 0.162 Pt 0.0469 Pt

0.68 m3 0.158 kg Natural gas, Heavy fuel 0.162 Pt 0.0466 Pt

0.233 m3 Natural gas, 0.062 Pt

0.272 m3 Natural gas, 0.0598 Pt

Figure 6.1: Impact flow diagram of hydrogen production via steam methane reforming.

processes, U atplant/RER forchemical Steam, Land use Land Mineralsfuels Fossil

/ Eutrophication /

Electricity, production mix US/US U US/US mix production Electricity,

reforming methane steam via of hydrogen for 1 kg assessment Damage : 2 . 6 ange Radiation Ozonelayer Ecotoxicity Acidification

U gas, atproduction/NG Natural

Figure

/H / Damage assessment Damage / /H Hydrogen,SMR Carcinogens Resp.organics Resp.inorganics ch Climate 5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: Analyzing 1 kg 'Hydrogen, SMR'; 'Hydrogen, kg 1 Analyzing

processes,U atplant/RER chemical for Steam,

Land use Land Mineralsfuels Fossil ..

/ Eutrophication /

Electricity, production mix US/US U US/US mix production Electricity,

ange Radiationlayer Ozone Ecotoxicity Acidification Natural gas, at production/NG U gas, atNatural production/NG

Weighting results for 1 kg of hydrogen via steam methane reforming methane steam via of hydrogen 1 kg for results Weighting : 3 . 6 /H / Weighting / /H

Figure

Hydrogen,SMR

Carcinogens Resp.organics Resp.inorganics ch Climate

1 0 1.4 1.3 1.2 1.1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 t P Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: Analyzing 1 kg 'Hydrogen,SMR'; kg 1 Analyzing

ng ng Human toxicity100a Human

Steam, for chemical processes,U atplant/RER forchemical Steam,

steady state

warming 500a warming Ozonedepletion layer Electricity, production mix US/US U US/US mix production Electricity, (CML method). (CML Natural gas, at production/NG U gas, atproduction/NG Natural Contribution of process to total environmental impact for steam methane reformi steam methane for impact total environmental process to of Contribution rld, 1990 / Characterization / 1990 rld, Figure 6.4: 6.4: Figure Hydrogen,SMR Abiotic depletion Abiotic Acidification Eutrophication Global 5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Method: CML 2001 (all impact categories) V2.05 / Wo / V2.05 categories) impact (all 2001 CML Method: Analyzing 1 kg 'Hydrogen, SMR'; 'Hydrogen, kg 1 Analyzing

6.1.2 Energy and Exergy Efficiencies A thermodynamic analysis of hydrogen production through steam methane reforming is presented here. The energy efficiency for the process is calculated as 76.8% while exergy efficiency is about 72.4%. Figure 6.5 shows the effect of changing the inlet reformer pressure on energy and exergy efficiencies. Increasing the reformer pressure from 800 kPa to 1200 kPa, the energy efficiency decreases from 76% to 72% and exergy efficiency decreases from 72.6% to 72.3%, because of the amount of power requirement in the compressor to compress natural gas. A similar case is presented in Figure 6.6 where changing the ambient temperature also decreases the energy and exergy efficiencies. However, this decrease in efficiencies is not large as compare to pressure variation.

0.7695 0.7255 Energy Exergy 0.725 0.769

0.7245 0.7685

0.724

0.768

0.7235 efficiency Exergy Energy efficiency Energy

0.7675 0.723

0.767 0.7225 800 900 1000 1100 1200 Inlet pressure of reformer [kPa]

Figure 6.5: Effect of variation of reformer pressure on energy and exergy efficiencies. The inlet pressure of the reformer also affects the mass of hydrogen production as well as mass of natural gas consumption. Increasing the pressure from 800 kPa to 1200 kPa, the mass of hydrogen production reduces to 0.31 kg from 0.4 kg. While mass of methane also decreases from 1.35 kg to 1 kg which is shown in Figure 6.7. Similarly, Figure 6.8 shows the declination of masses of hydrogen and natural gas as the ambient temperature increases.

0.7683 0.7245 Energy Exergy 0.7682 0.7244

0.768

0.7242 Exergy efficiency Exergy

Energy efficiency Energy 0.7679

0.7241

0.7677 300 315 330 345 360 Tο [K]

Figure 6.6: Effect of varying ambient temperature on energy and exergy efficiencies.

1.35 0.38

mCH4

mH 2 1.3 0.36 [kg] [kg]

1.25 H2 m CH4 m 0.34 1.2

1.15 0.32 800 900 1000 1100 1200 Inlet pressure of reformer [kPa]

Figure 6.7: Effect of variation inlet pressure of reformer on mass of hydrogen.

1.26 0.346 CH4 H 1.254 2 0.344

1.249 0.342 ] [kg] g 2 k

1.243 H [

CH4 0.34

m 1.238

1.232 0.338

1.227 0.336 290 300 310 320 330 340 350 Tο [K]

Figure 6.8: Effect of variation of ambient temperature on mass of hydrogen

Figure 6.9 shows the increase in the amount of hydrogen production with respect to electricity and natural gas consumption. From this method of hydrogen production natural gas is the major raw material on which hydrogen depends along with energy and other source. With the increase in hydrogen production from 0.4 to 3 kg, there is an increase in the consumption of natural gas from 2 to 11 kg. In SMR of natural gas large amount of natural gas is consumed which is also shown in impact assessment results. It is calculated and also confirmed from the past studies that 1 kg of hydrogen needs about more than 3 kg of natural gas.

The electricity consumption also increases as amount of hydrogen production increases. Large amount of fossil fuels are consumed in this method of hydrogen production which has effect on the environment in terms of human health, misbalance in ecosystem and declining the fossil fuel reserve which can be seen in the results of environmental impact. The last parameter which affects the values of energy and exergy efficiency is the reformer temperature. Increasing the reformer temperature from 600 to 800K, there is a minor decrease in the energy and exergy efficiency. However this

66 increase in temperature might increase the hydrogen production but this rate is not that much as the increase in energy consumed to increase the temperature.

12 30000

Electricity mCH 4

10 25000

] 20000 g k [

CH4 15000 m 4

10000 Electricity[kJ] consumption

2 5000 0.4 0.8 1.2 1.6 2 2.4 2.8 mH 2 [kg]

Figure 6.9: Effect of increasing hydrogen production on methane and electricity consumption.

0.7685 0.7248 Exergy Energy

0.7245

0.768 0.7242

0.7239

0.7675 efficiency Exergy Energy efficiency Energy

0.7236

0.767 600 650 700 750 800 Reformer Temperature [K]

Figure 6.10: Effect of variation of reformer temperature on energy and exergy efficiencies.

6.2 Hydrogen from Chlorine Electrolysis Using Different Cells In the analysis of the hydrogen production from Na-Cl electrolysis, we analyse this method using different cells used in the system. The diaphragm cell, membrane cell and mercury cell which are commercially used in the electrolysis of Na-Cl for chlorine, sodium hydroxide and hydrogen production. Impact assessment results are discussed for the preparation of 1 kg of hydrogen using these three cells. Figure 6.12 to Figure 6.14 show the impact flow diagram of hydrogen production using different cells.

6.2.1 Impact Assessment Results Implementing the life cycle assessment methodology on the hydrogen production from electrolysis, different cells are analysed and environmental results are calculated which are shown in Table 6.4. Bar chart diagram based on these results is presented in Figure 6.11. In this calculation results of the mercury cell are set as the benchmark and it can be seen that all results of mercury cell is 100%. Electrolysis using the mercury cell has the maximum percentage of emissions and energy consumption as compare to diaphragm and membrane cell. After mercury, and diaphragm cell also effect the environment. Moreover, in this electrolysis the energy consumption in terms of electricity is also fulfilled by fossil sources. Damage assessment results shows that almost all impact categories has percentage more than 80% with maximum value located with land use and minerals. Table 6.4: Damage assessment results for hydrogen production using different cells.

Impact category Unit Diaphragm cell Membrane cell Mercury cell Carcinogens DALY 4.91×10 -7 4.86×10 -7 5.42×10 -7 Resp. organics DALY 2.78×10 -10 2.78×10 -10 3.12×10 -10 Resp. inorganics DALY 5.34×10 -7 5.25×10 -7 6.10×10 -7 Climate change DALY 1.96×10 -7 1.92×10 -7 2.27×10 -7 Radiation DALY 1.42×10 -8 1.37×10 -8 1.66×10 -8 Ozone layer DALY 6.39×10 -11 6.36×10 -11 7.08×10 -11 Ecotoxicity PAF*m 2yr 0.042 0.042 0.046 Acidification PDF* m2yr 0.013 0.013 0.015 Land use PDF* m2yr 0.009 0.009 0.010 Minerals MJ surplus 0.062 0.063 0.064

Land use Land Mineralsfuels Fossil

using Hydrogen, liquid, mercury cell, at plant/RER U atplant/RER cell, mercury Hydrogen,liquid,

/ Eutrophication /

U'; atplant/RER cell, cury

Hydrogen, liquid, membrane cell, at plant/RER U atplant/RER cell, membrane Hydrogen,liquid,

different cell. different

mer 'Hydrogen,liquid, kg 1 and U' atplant/RER ll,

ange Radiation Ozonelayer Ecotoxicity Acidification

Hydrogen, liquid, diaphragm cell, at plant/RER U atplant/RER cell, diaphragm Hydrogen,liquid, : Damage assessment results for hydrogen production via electrolysis via production hydrogen for results assessment : Damage 11 .

6 /H / Damage assessment Damage / /H t plant/RER U', 1 kg 'Hydrogen, liquid, membrane ce membrane 'Hydrogen,liquid, kg 1 U', plant/RER t

Figure

Carcinogens Resp.organics Resp.inorganics ch Climate

5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: Comparing 1 kg 'Hydrogen, liquid, diaphragm cell, a cell, diaphragm 'Hydrogen,liquid, kg 1 Comparing

After implementing weighting criteria a better picture of the impact on the environment can be seen. In the damage assessment almost all values have similar contribution. However, weighting results have different pictures as shown in Figure 6.15. The major impact of this process is done by the category of fossil fuels extraction in all types of cells. Second category which has 0.0313 parts in mercury cell, 0.269 part in the membrane cell and 0.0273 part in the diaphragm cell.

Table 6.5: Weighting results for hydrogen production using different cell.

Impact category Unit Diaphragm cell Membrane cell Mercury cell

Total Pt 0.0766 0.0756 0.0867 Carcinogens Pt 0.0168 0.0166 0.0186 Resp. organics Pt 9.50×10 -6 9.51×10 -6 1.07×10 -5 Resp. inorganics Pt 0.0183 0.0180 0.0209 Climate change Pt 0.0067 0.0066 0.0078 Radiation Pt 0.0005 0.0005 0.0006 Ozone layer Pt 2.19×10 -6 2.18×10 -6 2.42×10 -6 Ecotoxicity Pt 0.0029 0.0029 0.0032 Acidification Pt 0.0009 0.0009 0.0011 Land use Pt 0.0007 0.0007 0.0007 Minerals Pt 0.0025 0.0025 0.0025 Fossil fuels Pt 0.0273 0.0269 0.0313

Table 6.6: Process contribution of environmental impact categories

Hydrogen, Hydrogen, Hydrogen, Impact category Unit diaphragm cell membrane cell mercury cell Abiotic depletion kg Sb-eq 6.78×10 -3 6.61×10 -3 7.86×10 -3 -3 -3 -3 Acidification kg SO 2-eq 4.60×10 4.50×10 5.30×10 -3 -1 -3 Eutrophication kg PO 4-eq 3.18×10 3.10×10 3.67×10 -1 -1 Global warming kg CO 2-eq 9.09×10 8.87×10 1.05 Ozone layer kg R-11-eq 5.99×10 -8 5.95×10 -8 6.65×10 -8 Human toxicity kg 1,4-DB-eq 4.22×10 -1 4.23×10 -1 4.49×10 -1

The CML method results have similar results about mercury cell which has maximum amount of damage on human health, human welfare and ecosystem. Membrane cell has the minimum impact on the environment as compare to other two

70 cells. However, if we compare electrolytic hydrogen production method with steam methane reforming, strong difference can be seen in all impact categories. Only eutrophication potential have enormous amount of impact which can be compared with steam methane reforming. Figure 6.15 shows the comparison between electrolytic hydrogen production and steam methane reforming. The eutrophication depletion in case of SMR is about 0.00364 kg PO 4 eq. While for electrolytic hydrogen its values are

0.00367 kg PO 4 eq. for mercury cell, 0.0031 kg PO 4 eq. for membrane cell and 0.00318 kg PO 4 eq. for diaphragm cell.

1 kg Hydrogen, 0.0867 Pt

0.842 kg 6.77 MJ Sodium Electricity, 0.0183 Pt 0.0669 Pt

5.33E-10 p 6.92 MJ Chemical Electricity, 0.0164 Pt 0.066 Pt

8.76E-5 m3 0.00672 kg 6.99 MJ Building, Facilities, Electricity, 0.00701 Pt 0.00928 Pt 0.0659 Pt

0.0163 kg 0.00113 kg 1.6 MJ 0.742 MJ 0.799 MJ Brick, at Copper, at Electricity, Electricity, Electricity, 0.00028 Pt 0.00817 Pt 0.0121 Pt 0.00896 Pt 0.0123 Pt

0.000399 MJ 0.0241 kg 0.362 MJ Pulverised Heavy fuel Electricity, 1.74E-6 Pt 0.00727 Pt 0.00685 Pt

0.36 kg 0.0246 kg 0.966 MJ Lignite, at Heavy fuel Natural 0.0068 Pt 0.00727 Pt 0.00685 Pt

Figure 6.12: Flow diagram of hydrogen production via electrolysis using mercury cell.

1 kg Hydrogen, 0.0766 Pt

0.84 kg 5.77 MJ Sodium Electricity, 0.0183 Pt 0.0571 Pt

5.32E-10 p 5.9 MJ Chemical Electricity, 0.0164 Pt 0.0563 Pt

8.73E-5 m3 0.00671 kg 5.96 MJ Building, Facilities, Electricity, 0.00699 Pt 0.00926 Pt 0.0562 Pt

0.0162 kg 0.00111 kg 1.36 MJ 0.633 MJ 0.682 MJ Brick, at Copper, at Electricity, Electricity, Electricity, 0.000279 Pt 0.00799 Pt 0.0103 Pt 0.00764 Pt 0.0105 Pt

0.0207 kg 0.000707 kg Heavy fuel Copper 0.00624 Pt 0.00369 Pt

0.0211 kg 0.149 kg Heavy fuel Disposal, 0.00624 Pt 0.00654 Pt

Figure 6.13: Impact flow diagram of hydrogen production using diaphragm cell.

1 kg Hydrogen, 0.0867 Pt

0.842 kg 6.77 MJ Sodium Electricity, 0.0183 Pt 0.0669 Pt

5.33E-10 p 6.92 MJ Chemical Electricity, 0.0164 Pt 0.066 Pt

8.76E-5 m3 0.00672 kg 6.99 MJ Building, Facilities, Electricity, 0.00701 Pt 0.00928 Pt 0.0659 Pt

0.0163 kg 0.00113 kg 1.6 MJ 0.742 MJ 0.799 MJ Brick, at Copper, at Electricity, Electricity, Electricity, 0.00028 Pt 0.00817 Pt 0.0121 Pt 0.00896 Pt 0.0123 Pt

0.0241 kg Heavy fuel 0.00727 Pt

0.0246 kg Heavy fuel 0.00727 Pt

Figure 6.14: Impact flow diagram of hydrogen production using membrane cell.

t cell.

use Land Mineralsfuels Fossil

Hydrogen, liquid, mercury cell, at plant/RER U atplant/RER cell, mercury Hydrogen,liquid,

/ Eutrophication /

U'; atplant/RER cell, cury

U atplant/RER cell, membrane Hydrogen,liquid,

ll, at plant/RER U' and 1 kg 'Hydrogen, liquid, mer 'Hydrogen,liquid, kg 1 and U' at plant/RER ll,

ange Radiationlayer Ozone Ecotoxicity Acidification

: Weighting results for hydrogen production through electrolysis using differen using electrolysis through production hydrogen for results : Weighting Hydrogen, liquid, diaphragm cell, at plant/RER U at plant/RER cell, diaphragm Hydrogen,liquid, 15 . 6 /H / Weighting / /H t plant/RER U', 1 kg 'Hydrogen, liquid, membrane ce membrane 'Hydrogen,liquid, kg 1 U', plant/RER t

Figure Figure

Carcinogens Resp.organics Resp.inorganics ch Climate

8 6 4 2 0

30 28 26 24 22 20 18 16 14 12 10 t P m Comparing 1 kg 'Hydrogen, liquid, diaphragm cell, a cell, diaphragm liquid, 'Hydrogen, kg 1 Comparing Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method:

500a

cell erent Hydrogen, liquid, mercury cell, at plant/RER U at plant/RER cell, mercury Hydrogen,liquid, w 500a arming 40alayer depletion Ozone toxicity Human cury cell, at plant/RER U'; atplant/RER cell, cury

Hydrogen, liquid, membrane cell, at plant/RER U at plant/RER cell, membrane Hydrogen,liquid, (CML method). ll, at plant/RER U' and 1 kg 'Hydrogen, liquid, mer 'Hydrogen,liquid, kg 1 and U' at plant/RER ll, Hydrogen, liquid, diaphragm cell, at plant/RER U at plant/RER cell, diaphragm Hydrogen,liquid, rld, 1990 / Characterization / 1990 rld, t plant/RER U', 1 kg 'Hydrogen, liquid, membrane ce membrane liquid, 'Hydrogen, kg 1 U', plant/RER t : Impact assessment chart for hydrogen production through electrolysis using diff using electrolysis through production hydrogen chart for assessment : Impact 16 . 6 Figure Figure Abiotic depletion Acidification Eutrophication Global 5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Comparing 1 kg 'Hydrogen, liquid, diaphragm cell, a cell, diaphragm 'Hydrogen,liquid, kg 1 Comparing Wo / V2.05 categories) impact (all 2001 CML Method:

500a Hydrogen,SMR

warming 500a warming 40a layer Ozonedepletion toxicity Human y cell, at plant/RER U' and 1 kg 'Hydrogen,SMR'; kg 1 and U' atplant/RER y cell, electrolytic hydrogen production production hydrogen electrolytic Hydrogen, liquid, mercury cell, at plant/RER U atplant/RER cell, mercury Hydrogen,liquid, ll, at plant/RER U', 1 kg 'Hydrogen, liquid, mercur liquid, 'Hydrogen, kg 1 U', atplant/RER ll, Hydrogen, liquid, membrane cell, at plant/RER U atplant/RER cell, membrane Hydrogen,liquid, and steam methane reforming (CML method). reforming methane and steam : Comparison of impact categories between between categories impact of : Comparison rld, 1990 / Characterization / 1990 rld, 17 . t plant/RER U', 1 kg 'Hydrogen, liquid, membrane ce membrane 'Hydrogen,liquid, kg 1 U', plant/RER t 6 Figure Figure Hydrogen, liquid, diaphragm cell, at plant/RER U atplant/RER cell, diaphragm Hydrogen,liquid, Abiotic depletion Abiotic Acidification Eutrophication Global 5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % a cell, diaphragm liquid, 'Hydrogen, kg 1 Comparing Wo / V2.05 categories) impact (all 2001 CML Method:

6.3 Hydrogen via Electrolysis Using Wind Electricity In the analyses of hydrogen production using wind electricity, the same electrolytic process is assumed. In this case membrane cell is used instead of mercury and diaphragm cell because it has minimum impact on the environment. Figure 6.18 shows the impact flow diagram of hydrogen production through wind based electricity.

6.3.1 Impact Assessment Results In the environmental assessment of hydrogen production through wind based electricity, major chemicals and energy and waste is considered. In this manner the process will be evaluated more carefully.

Table 6.7 shows all the major contributors in the production of 1 kg of hydrogen through electrolysis. Figure 6.19 depicted the values of these tables in a bar chart format which shows that the major influence on environment is due to the sodium chloride powder and from the chemical plant. For the chemical plants the value for carcinogens particle which are danger for human health causing cancer is 3.70 ×10 -7 (DALY). The chemical plant has also major effect on ecosystem and the value for ecotoxicity is about 0.038 PAF*m 2yr. The third large impact category under the chemical plant is minerals which have effect of future energy deficiency of 0.104 MJ surplus.

The second most dominant material which covered almost every impact category is sodium chloride powder. Sodium chloride is essential components in the electrolysis for hydrogen production. The radiation value (comes from radioactive radiation) for sodium chloride powder is the largest area covered in the bar of radiation as shown in Figure 6.19. Fossil fuel category for sodium chloride also contain significant amount of impact which is about 0.128 MJ surplus of energy. Transportation is another category in this process which also contributes emissions and other impacts on the environment. The significant percentage values for transportation come under fossil fuels, acidification, ozone layer and respiratory organics. The effect of transportation in fossil fuels is 0.0291 MJ surplus of energy which covers about 18% among other different process. The ozone layer effect for transport through the truck is about 2.42 ×10 -12 DALY and for rail transport is about 2.79 ×10 -14 DALY. Other process chemicals such as sodium hydroxide can be seen in all impact categories. Sodium hydroxide is also a product of Na-Cl electrolysis for

77 hydrogen production. In this process, electricity is generated through renewable wind power options which have less impact on environment shown in Figure 6.19.

1 kg Hydrogen 0.0562 Pt

0.847 kg 1.35E-9 p Sodium Chemical 0.0184 Pt 0.0415 Pt

1.16 MJ 0.00022 m3 0.017 kg Electricity, Building, Facilities, 0.0114 Pt 0.0176 Pt 0.0235 Pt

1.22 MJ 0.00256 kg 0.0051 kg 0.000734 kg Electricity, Copper, at Chromium Electronics 0.0116 Pt 0.0185 Pt 0.00757 Pt 0.00631 Pt

1.24 MJ 0.000432 kg 0.00322 kg 0.000104 kg Electricity, Copper, Steel, Printed 0.0117 Pt 0.00997 Pt 0.00471 Pt 0.00549 Pt

0.00163 kg 0.00193 kg 5.18E-5 kg Copper Ferronickel, Printed 0.00853 Pt 0.00528 Pt 0.00474 Pt

0.352 kg Disposal, 0.0154 Pt

Figure 6.18: Impact flow diagram of hydrogen production via wind based electricity.

Table 6.7a: Damage assessment results for hydrogen production using wind electricity.

Impact Calcium Unit Na-Cl Soda Barite HCl Sulphite category chloride

Carcinogens DALY 1.56×10 -7 1.15×10 -9 1.35×10 -6 3.54×10 -9 5.65×10 -10 3.17×10 7 Resp. organics DALY 6.2×10 -11 7.66×10 -13 9.74×10 -6 2.70×10 - 3.66×10 -13 2.5×10 -14 Resp. DALY 9.82×10 -3 2.0×10 -9 1.77×10 -6 6.53×10 -9 5.9×10 -10 1.2×10 -10 Climate change DALY 3.06×10 -3 4.9×10 -10 6.38×10 -6 1.54×10 -9 1.9×10 -10 1.3×10 -11 Radiation DALY 1.60×10 -9 8.35×10 -12 4.81×10 -6 2.80×10 - 1.2×10 -11 7.4×10 -13 Ozone layer DALY 9.2×10 -12 5.80×10 -14 1.53×10 -6 2.10×10 - 1.5×10 -12 4.8×10 -15 Ecotoxicity PAF* m2yr 0.0152 0.0001 9.75×10 -6 0.0003 5.39×10 -45 3.01×10 -6 Acidification PDF* m2yr 0.0023 9.92×10 -5 4.59×10 -6 0.0003 1.45×10 -5 2.47×10 -6 Land use PDF* m2yr 0.0033 4.19×10 -7 3.13×10 -6 0.0001 1.21×10 -5 7.46×10 -7 Minerals MJ surplus 0.0352 0.0002 1.01×10 -5 0.0006 9.53×10 -5 5.02×10 -7 Fossil fuels MJ surplus 0.1287 0.0010 0.0002 0.0034 0.0009 6.56×10 -5

Table 6.7b: Damage assessment results for hydrogen production using wind electricity.

Electricity Impact Transport Transport Unit Na-OH Chemical wind category truck train power

Carcinogens DALY 1.06×10 -8 1.41×10 -9 1.07×10 -11 3.70×10 -7 1.36×10 -8 Resp. organics DALY 6.15×10 -12 2.37×10 -11 3.09×10 -13 8.60×10 -11 1.08×10 -11 Resp. DALY 1.20E-08 1.56×10 -8 3.61×10 -10 1.48×10 -7 1.88×10 -8 Climateinorganics change DALY 4.47×10 -9 3.01×10 -9 8.07×10 -11 2.58×10 -8 3.03×10 -9 Radiation DALY 3.27×10 -10 2.75×10 -11 4.22×10 - 1.03×10 -9 5.31×10 -11 Ozone layer DALY 1.39×10 -12 2.42×10 -12 2.79×10 -14 8.27×10 -12 8.29×10 -13 Ecotoxicity PAF*m 2yr 0.0009 0.0004 1.33×10 -5 0.0382 0.0047 Acidification PDF* m 2 yr 0.0003 0.0006 1.16×10 -5 0.0025 0.0002 Land use PDF* m 2yr 0.0002 0.0002 1.15×10 -5 0.0079 0.0009 Minerals MJ surplus 0.0012 0.0002 2.14×10 -5 0.1043 0.0139 Fossil fuels MJ surplus 0.0155 0.0291 0.00040 0.1152 0.0153

.organics Carcinogens

ant/RER U ant/RER CH U CH

Sodium chloride, powder, at plant/RER U powder,atplant/RER chloride, Sodium U Barite,atplant/RER U H2O,plant/RER at in 30%acid, Hydrochloric atpl mix, production H2O, hydroxide,in 50% Sodium U 800kW/RER plant power atElectricity,wind paper, 11.2%Disposal, water, sanitarytolandfill/ Transport, freight, rail/RER U Transport, freight, rail/RER

Ecotoxicitylayer Ozone Radiation Resp.inorganics Resp

tion esidual material landfill/CH U landfill/CH material esidual

Eutrophication /

Damage assessment chart for hydrogen production using wind electricity wind using production hydrogen chart for assessment Damage : 19 . 6

Hydrogen via electrolysis (wind) electrolysis via Hydrogen U Soda, powder,atplant/RER storage/CHU CaCl2, atregional chloride, Calcium U atplant/RER Sulphite, U organics/RER/I plant, Chemical water,electrolysis,0% NaCl r tosludge, Disposal, Transport,>16t,lorry fleet average/RER U Figure Figure

assessment Damage / /H

change Climate fuels Fossil Mineralsuse Land Acidifica 5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: (wind)'; electrolysis via 'Hydrogen kg 1 Analyzing

The weighting values for impact categories are shown in Table 6.8. Weighting of impact categories shows that the chemical plant in the hydrogen production process has most impact on the environment. Figure 6.20 shows the weighting bar chart for wind based hydrogen production method in which the chemical plant contribution can be seen in almost all impact categories. The carcinogen particulates from the chemical plant hold the maximum number of part which is about 0.0127 Pt. On the other side sodium chloride which is another main contributor in the hydrogen production through wind electricity has also maximum value in carcinogen with 0.0053 parts. This carcinogen is affecting the human health in terms of life threatening disease cancer. Sodium chloride also has significant weight on fossil fuel and respiratory inorganics with 0.0051 parts and 0.0034 parts respectively.

The same process is analysed using the CML method to examine the damage in terms of abiotic depletion, global warming potential, ozone layer and other. Table 6 .10 show the values for the impact categories. The CML method also shows that the chemical plant and sodium chloride are major contributors of environmental impact in the production of 1 kg hydrogen. Chemical plants have large impact under human toxicity which has a value of 0.506 kg 1.4-DB eq. Sodium chloride has abiotic depletion values of 9.82 ×10 -4 kg Sb eq. which is about 45% among other processes and material. The second large contributor in abiotic depletion is the chemical plant which has a value of 8.47 ×10 -4 kg Sb eq. and covers 35% of chart area as shown in Figure 6.21. The global warming potential, ozone layer depletion and eutrophication values for sodium chloride are 1.4 ×10 -1 kg CO2 eq., 8.59 ×10 -9 kg R-11 eq and 5.43 ×10 -4 kg PO 4 eq. respectively. For the chemical plant values are 0.12 kg CO 2 eq. 7.96 ×10 -9 kg R-11 and 6.62 ×10 -4 kg PO 4 eq. respectively. The electricity generated by wind source which is used in this method has very little impact on environment. The global warming potential for wind electricity is 1.38 ×10 -2 kg

CO 2 eq. which covers only 5% among other impact categories. The abiotic depletion for wind based electricity is about 1.06 ×10 -4 kg Sb eq. which also covers 5% of the bar area among other category. These results reveal that electricity from wind nearly free from environmental pollution which is a better option of hydrogen production using this electricity in the process of electrolysis.

Table 6.8a: Weighting results for hydrogen production using wind electricity.

Calcium Impact category Unit Na-Cl Soda Barite HCl Sulphite chloride

Climate change Pt 0.0010 1.68 ×10 -5 2.18 ×10 -4 5.29 ×10 -5 6.72 ×10 -6 4.61 ×10 -7 Fossil fuels Pt 0.0051 3.82 ×10 -6 8.88 ×10 -4 0.00013 3.75 ×10 -5 2.61 ×10 -6 Minerals Pt 0.0014 7.66 ×10 -6 4.00 ×10 -7 2.36 ×10 -5 3.79 ×10 -6 1.99 ×10 -7 Land use Pt 0.0002 2.93 ×10 -6 2.19 ×10 -7 9.47 ×10 -6 8.43 ×10 -7 5.22 ×10 -8 Acidification Pt 0.0002 6.94 ×10 -6 3.21 ×10 -7 2.17 ×10 -5 1.02 ×10 -6 1.73 ×10 -7 Ecotoxicity Pt 0.0011 7.08 ×10 -9 6.82 ×10 -7 2.21 ×10 -5 3.77 ×10 -6 2.10 ×10 -7 Ozone layer Pt 3.17 ×10 -7 1.98 ×10 -9 5.24 ×10 -10 7.19 ×10 -9 5.46 ×10 -8 1.65 ×10 -10 Radiation Pt 5.49 ×10 -5 2.86 ×10 -7 1.65 ×10 -7 9.58 ×10 -7 4.13 ×10 -7 2.55 ×10 -8 Resp. inorganics Pt 0.0034 7.05 ×10 -5 6.06 ×10 -4 0.00022 2.05 ×10 -5 4.03 ×10 -6 Resp. organics Pt 2.14 ×10 -6 2.62 ×10 -8 3.34 ×10 -9 9.24 ×10 -8 1.25 ×10 -8 8.06 ×10 -6 Carcinogens Pt 0.0053 3.95 ×10 -5 4.63 ×10 -4 0.00012 1.93 ×10 -5 1.09 ×10 -6

Table 6.8b: Weighting results for hydrogen production using wind electricity.

Impact Transport, Transport, Electricity Disposal, Unit NaOH Chemical category truck rail wind power electrolysis

Climate change Pt 0.0002 0.0001 2.76 ×10 -7 0.0009 0.0001 1.67 ×10 -5 Fossil fuels Pt 0.0006 0.0012 1.61 ×10 -7 0.0046 0.0006 5.28 ×10 -5 Minerals Pt 4.92 ×10 -5 1.04 ×10 -5 8.51 ×10 -7 0.0041 0.0006 5.57 ×10 -7 Land use Pt 1.40 ×10 -5 1.56 ×10 -5 8.05 ×10 -7 0.0006 6.54 ×10 -7 2.93 ×10 -6 Acidification Pt 2.11 ×10 -5 4.86 ×10 -5 8.12 ×10 -7 0.0002 1.62 ×10 -7 1.96 ×10 -6 Ecotoxicity Pt 6.31 ×10 -5 2.99 ×10 -3 9.27 ×10 -7 0.0027 0.0003 1.45 ×10 -6 Ozone layer Pt 4.76 ×10 -8 8.30 ×10 -8 9.55 ×10 -10 2.83 ×10 -7 2.84 ×10 -7 4.16 ×10 -9 Radiation Pt 1.12 ×10 -5 9.40 ×10 -7 1.44 ×10 -7 3.51 ×10 -7 1.82 ×10 -7 1.57 ×10 -7 Resp. Pt 0.0004 0.0005 1.24 ×10 -5 0.0051 0.0006 2.42 ×10 -5 Resp. organics Pt 2.11 ×10 -7 8.12 ×10 -7 1.06 ×10 -8 2.94 ×10 -7 3.70 ×10 -7 3.58 ×10 -8 Carcinogens Pt 0.0004 4.82 ×10 -7 3.66 ×10 -6 0.0127 0.0005 5.75 ×10 -5

.organics Carcinogens ant/RER U ant/RER

CH U CH . Sodium chloride, powder, at plant/RER U atpowder, plant/RER chloride, Sodium U at Barite,plant/RER U at H2O,plant/RER in 30% acid, Hydrochloric atpl mix, H2O,production hydroxide, in 50% Sodium U 800kW/RER plant power atwind Electricity, paper, 11.2% Disposal, water, sanitarytolandfill/ Transport, freight, rail/RER U Transport, freight, rail/RER Ecotoxicitylayer Ozone Radiation Resp.inorganics Resp tion esidual material landfill/CH U landfill/CH material esidual / Eutrophication / Weighting chart for hydrogen production using wind electricity using production for hydrogen chart Weighting : 20 . 6 Figure Figure Hydrogen via electrolysis (wind) electrolysis via Hydrogen U Soda,atpowder, plant/RER storage/CHU CaCl2, atregional chloride, Calcium U at plant/RER Sulphite, U plant,organics/RER/I Chemical water,electrolysis,0% r NaCl tosludge, Disposal, Transport,>16t,lorry fleet average/RER U /H / Weighting / /H Climate change Climate fuels Fossil Mineralsuse Land Acidifica

9 8 7 6 5 4 3 2 1 0

19 18 17 16 15 14 13 12 11 10 t P m Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: (wind)'; viaelectrolysis 'Hydrogen kg 1 Analyzing 83

500a city city ant/RERU CH U CH Sodium chloride, powder, at plant/RER U powder,atplant/RER chloride, Sodium U atplant/RER Barite, U atH2O,plant/RER in 30% acid, Hydrochloric atpl mix, H2O,production hydroxide, 50%in Sodium U 800kW/RER plant power atwind Electricity, paper, 11.2%Disposal, water, sanitarytolandfill/ Transport, freight, rail/RER U Transport, freight, rail/RER warming 500a warming 40a layer Ozonedepletion toxicity Human

(CML method). esidual material landfill/CH U landfill/CH material esidual : Impact assessment results for hydrogen production using wind based electri wind based using production hydrogen for results assessment : Impact Hydrogen via electrolysis (wind) electrolysis via Hydrogen U Soda, powder,atplant/RER storage/CHU CaCl2, atchloride, regional Calcium U atplant/RER Sulphite, U organics/RER/I plant, Chemical electrolysis,water,0% r toNaCl sludge, Disposal, Transport,>16t,lorry fleet average/RER U 21 . rld, 1990 / Characterization / 1990 rld, 6 Figure Figure

Abiotic depletion Abiotic Acidification Eutrophication Global

5 0 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Wo / V2.05 categories) impact (all 2001 CML Method: Analyzing 1 kg 'Hydrogen via electrolysis (wind)'; electrolysis via 'Hydrogen kg 1 Analyzing

6.3.2 Energy and Exergy Efficiencies Thermodynamic analysis of hydrogen production through sodium chlorine electrolysis using wind electricity is presented here. The energy efficiency for the process is calculated as 67.98% while exergy efficiency is about 60.57%. Figure 6.22 shows the effect of changing the inlet pressure on energy and exergy efficiencies. Both efficiencies are decreasing on increasing the pressure at which Na-Cl is coming towards the electrolyser. The energy efficiency decreases from 67% to 56% while exergy efficiency reduced to 55% from 66% as pressure rose to 120 kPa.

0.68 0.6 Energy

0.66 Exergy 0.58

0.64 0.56

0.62

0.54

0.6 Exergy efficiency Energy efficiency 0.52 0.58

0.56 0.5 104 108 112 116 120

Inlet pressure [kPa]

Figure 6.22: Effect of variation of inlet pressure on energy and exergy efficiencies of wind based hydrogen production system.

In general, surrounding conditions also play an effective role on the efficiencies of the system. Figure 6.23 shows the effect of variation of ambient temperature on energy and exergy efficiencies. At operating condition the energy efficiency is about 68% which decreases to 48% as temperature rose to 310K. Similar results can be seen for exergy efficiencies, with the increase of ambient temperature the exergy efficiency decreases from 60% to 43%. During the electrolysis, the surrounding temperature should be

85 moderate, high temperature might affect the efficiency of the system which can be seen by our result. 0.7 0.65 Energy Exergy 0.65 0.6

0.6 0.55

0.55 0.5 Exergy efficiency Exergy Energy efficiency Energy

0.5 0.45

0.45 0.4 298 302 306 310

Tο [K] Figure 6.23: Effect of variation of ambient temperature on energy and exergy efficiencies of wind based hydrogen production method

0.72 0.64 Energy

0.7 Exergy 0.62

0.68 0.6

0.66

0.58 0.64 efficiency Exergy Energy eficiency Energy 0.56 0.62

0.6 0.54 300 310 320 330 340 350 2 Area of Wind Turbine [m ]

Figure 6.24: Effect of variation in the area of wind turbine on energy and exergy efficiencies of wind based hydrogen production.

Figure 6.23 shows the effect of changing the area of wind turbine on energy and exergy efficiencies. In this study, when the area of wind turbine increases both energy and exergy efficiencies decrease, which is opposite what is expected. Generally, whenever the area of wind turbine increase, the electricity production also increases to be used for the hydrogen production. But during the electrolysis optimum amount of voltage and current is required. After that condition, a saturation point occurs and no further voltage or current effect the electrolysis process. In other words, the hydrogen production might increase with the increase in the area of wind turbine but that rate is not that much as increase in energy input to the system in terms of electricity. Similar results can be seen in Figure 6.26 where efficiency is decreasing by increasing the wind velocity.

The above discussion is also verified by the result shown in Figure 6.25 where both the efficiencies increase by the increase in the amount of hydrogen production. When the mass of hydrogen increases from 0.3 kg to 1 kg, energy efficiency increases from 26% to 87% and the exergy efficiency increases from 30% to 82%. This result is obvious as previously defined efficiency by hydrogen as a potential useful product.

0.9 Energy 0.9 Exergy 0.8

0.7 0.75

0.6 0.6 0.5 Exergy efficiency Exergy Energy efficiency Energy 0.45 0.4

0.3 0.3

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

mH 2 [kg]

Figure 6.25: Effect of increasing the amount of produced hydrogen on energy and exergy efficiencies.

0.8 0.7 Energy Exergy 0.65 0.7 0.6

0.6 0.55

0.5 0.5 Exergy efficency Exergy

Energy efficiency Energy 0.45 0.4 0.4

0.3 0.35 4.8 5.2 5.6 6 Velocity of Wind [m/s]

Figure 6.26: Effect of variation of wind velocity on energy and exergy efficiencies. 6.4 Hydrogen via Electrolysis Using Solar Photovoltaic Electricity In the analyses of hydrogen production using solar photovoltaic electricity, the same electrolytic process is assumed as studied in the wind based hydrogen production. Among three cell, membrane cell is used instead of mercury and diaphragm cell because it has minimum impact on environment. Figure 6.27 shows the impact flow diagram of hydrogen production using solar photovoltaic electricity.

6.4.1 Impact Assessment Results In the environmental assessment of hydrogen production through solar photovoltaic electricity, major chemicals and energy and waste is considered. In this way the process will be evaluated more carefully.

Table 6.9 and Table 6.10 show the all major contributor in the production of 1 kg of hydrogen through electrolysis using solar energy. Figure 6.29 depicted the values of these tables in bar chart format which shows that the major influence on environment is due to the sodium chloride powder, from the chemical plant. Moreover, solar based electricity has also impacts on environment which can be seen in the bar chart. In this method electricity from solar is the third large process of contributing overall emissions.

For the chemical plants the value for carcinogens particle which are danger for human health causing cancer is 3.70 ×10 -7 (DALY). The chemical plant has also major effect on ecosystem and the value for ecotoxicity is about 0.038 PAF*m 2yr. These results are almost similar to the result of wind based hydrogen production except for power requirement which is electricity. The values for solar electricity are more than wind electricity which can be seen in Figure 6.29.

The second most dominant material in solar based hydrogen production which has covered almost every impact category is sodium chloride powder. Sodium chloride is essential components in the electrolysis for hydrogen production. The radiation value for sodium chloride powder is the 1.6 ×10 -9 DALY which covers about 45% of area in the bar of radiation as shown in Figure 6.29. The maximum value for electricity from solar photovoltaic comes under ozone layer and respiratory organics which are 1.25 ×10 -11 and 9.55 ×10 -11 DALY respectively. These categories can be seen on the damage assessment chart which covers 35% among all categories.

Table 6.9: Damage assessment results for hydrogen production using solar photovoltaic electricity.

Impact Sodium Calcium Unit Soda Barite HCl Sulphite category chloride chloride Carcinogens DALY 1.56×10 -7 1.15×10 -9 1.35×10 -10 3.54×10 -9 5.65×10 -10 3.17×10 -11 Resp. organics DALY 6.24×10 -11 7.66×10 -13 9.74×10 -14 2.70×10 -12 3.66×10 -13 2.35×10 -14 Resp. inorganics DALY 9.82×10 -8 2.06×10 -9 1.77×10 -10 6.53×10 -9 5.99×10 -10 1.18×10 -10 Climate change DALY 3.06×10 -8 4.90×10 -10 6.38×10 -11 1.54×10 -9 1.96×10 -10 1.35×10 -11 Radiation DALY 1.60×10 -9 8.35×10 -12 4.81×10 -14 2.80×10 -11 1.21×10 -11 7.46×10 -13 Ozone layer DALY 9.27×10 -12 5.80×10 -14 1.53×10 -14 2.10×10 -13 1.59×10 -12 4.81×10 -15 Ecotoxicity PAF*m 2yr 0.0152 0.0001 9.75×10 -6 0.0003 5.39×10 -5 3.01×10 -7 Acidification PDF* m 2yr 0.0023 9.92×10 -5 4.59×10 -6 0.0003 1.45×10 -5 2.47×10 -6 Land use PDF*m 2yr 0.0033 4.19×10 -5 3.13×10 -6 0.0001 1.21×10 -5 7.46×10 -7 Minerals MJ surplus 0.0352 0.0002 1.01×10 -5 0.0006 9.53×10 -5 5.02×10 -6 Fossil fuels MJ surplus 0.1287 0.0010 0.0002 0.0034 0.0009 6.56×10 -5

Table 6.10: Damage assessment results for hydrogen production using solar photovoltaic electricity.

Sodium Impact Transport, Transport, Chemical Electricity, Unit hydroxide, category truck rail plant photovoltaic 50% in H 2O Carcinogens DALY 1.06 ×10 -8 1.41 ×10 -9 1.07 ×10 -10 3.70 ×10 -7 8.19 ×10 -8 Resp. organics DALY 6.15 ×10 -12 2.37 ×10 -11 3.09 ×10 -13 8.60 ×10 -11 9.55 ×10 -11 Resp. inorganics DALY 1.20 ×10 -8 1.56 ×10 -8 3.61 ×10 -10 1.48 ×10 -7 4.17 ×10 -8 Climate change DALY 4.47 ×10 -3 3.01 ×10 -9 8.07 ×10 -11 2.58 ×10 -8 1.28 ×10 -8 Radiation DALY 3.27 ×10 -10 2.75 ×10 -11 4.22 ×10 -12 1.03 ×10 -9 3.89 ×10 -10 Ozone layer DALY 1.39 ×10 -12 2.42 ×10 -12 2.79 ×10 -14 8.27 ×10 -12 1.25 ×10 -11 Ecotoxicity PDF*m 2yr 0.0009 0.0004 1.33 ×10 -5 0.0383 0.0058 Acidification PDF*m 2yr 0.0003 0.0007 1.16 ×10 -5 0.0026 0.0010 Land use PDF*m 2yr 0.0002 0.0002 1.15 ×10 -5 0.0080 0.0008 Minerals MJ surplus 0.0012 0.0003 2.14 ×10 -5 0.1044 0.0160 Fossil fuels MJ surplus 0.0155 0.0292 0.0004 0.1153 0.0759

1 kg hydrogen 0.0622 Pt

0.848 kg 1.35E-9 p 4.66 MJ Sodium Chemical Electricity, 0.0184 Pt 0.0415 Pt 0.00887 Pt

1.27 MJ 0.000221 m3 0.017 kg Electricity, Building, Facilities, 0.0125 Pt 0.0176 Pt 0.0235 Pt

1.33 MJ 0.00287 kg 0.00443 kg 0.000734 kg Electricity, Copper, at Chromium Electronics 0.0127 Pt 0.0208 Pt 0.00657 Pt 0.00632 Pt

1.35 MJ 0.000486 kg 0.000104 kg Electricity, Copper, Printed 0.0127 Pt 0.0112 Pt 0.0055 Pt

0.00184 kg Copper 0.00959 Pt

0.395 kg Disposal, 0.0174 Pt

Figure 6.27: Impact flow diagram of hydrogen production via electrolysis using solar photovoltaic electricity.

1 MJ Electricity, 0.0019 Pt

5.55E-7 p 7.55E-7 p 3kWp 3kWp 0.000454 Pt 0.000595 Pt

1.91E-5 m2 5.72E-6 p 2.77E-5 m2 Photovoltaic Inverter, Photovoltaic 0.000365 Pt 0.000423 Pt 0.000455 Pt

8.38E-5 kg 0.00377 MJ 2.75E-5 m2 7.19E-8 kg Copper, at Natural gas, Photovoltaic Nickel, 0.000606 Pt 2.73E-5 Pt 0.000332 Pt 6.49E-7 Pt

1.42E-5 kg 0.0467 MJ 0.0111 kg Copper, Natural gas, Disposal, 0.000327 Pt 0.000305 Pt 0.000487 Pt

Figure 6.28: Impact flow diagram of photovoltaic electricity.

ant/RER U ant/RER CH U CH US U US

use Land Mineralsfuels Fossil

/ Eutrophication /

Sodium chloride, powder, at plant/RER U powder, plant/RER at chloride, Sodium U Barite, atplant/RER U H2O, atplant/RER in 30%acid, Hydrochloric atpl mix, H2O,production hydroxide, in 50% Sodium photovoltaic,plant/ at mix production Electricity, paper,11.2% Disposal, water, sanitarytolandfill/ Transport, freight, rail/RER U Transport, freight, rail/RER

electricity.

U landfill/CH material esidual

ange Radiationlayer Ozone Ecotoxicity Acidification assessment chart for hydrogen production using solar photovoltaic photovoltaic solar using production hydrogen chart for assessment

Damage Damage

: 29 . 6 hydrogen via electrolysis using photovoltaic using electrolysis hydrogenvia U Soda,powder, atplant/RER storage/CHU CaCl2, chloride, regional at Calcium U atplant/RER Sulphite, U organics/RER/I plant, Chemical water,electrolysis,0% r toNaCl sludge, Disposal, >16t,Transport,lorry fleet average/RER U /H / Damage assessment Damage / /H tovoltaic'; Figure

Carcinogens Resp.organics Resp.inorganics ch Climate

5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: pho using electrolysis via 'hydrogen kg 1 Analyzing

According to the weighting Figure 6.30, the processes which have major weight are the chemical plant, sodium chloride and solar electricity. The maximum parts can be seen under the category of carcinogens in which the chemical plant has 0.0127 parts, sodium chloride has 0.0053 parts, and solar electricity has 0.0028 parts and the remaining for others. The second maximum parts can be seen under the category of fossil fuels in which sodium chloride has 0.0051 parts, the chemical plants has 0.0046 parts and another mentionable process contributor is solar electricity which has 0.003 parts. The third category which has maximum number of parts is respiratory inorganics in which the chemical plant has maximum parts of 0.0051 with sodium chloride of 0.0034 parts and solar electricity has 0.0014 parts.

Table 6.11a: Weighting results for hydrogen production using solar photovoltaic electricity.

Impact Calcium Unit NaCl Soda Barite HCl Sulphite category chloride

Carcinogens Pt 0.0053 3.95×10 -5 4.63×10 -6 0.0001 1.93×10 -5 1.1× 10 -5 Resp. organics Pt 2.14×10 -6 2.62×10 -8 3.34×10 -9 9.24×10 -8 1.25×10 -8 8.1 ×10 -10 Resp. Pt 0.0034 7.05×10 -5 6.06×10 -6 0.0002 2.05×10 -5 4.0 ×10 -6 Climate change Pt 0.0010 1.68×10 -5 2.18×10 -6 5.29×10 -5 6.72×10 -6 4.6 ×10 -7 Radiation Pt 5.49×10 -5 2.86×10 -7 1.65×10 -7 9.58×10 -7 4.13×10 -7 2.5 ×10 -8 Ozone layer Pt 3.17×10 -7 1.98×10 -9 5.24×10 -10 7.19×10 -9 5.46×10 -8 1.6 ×10 -10 Ecotoxicity Pt 0.0011 7.08×10 -6 6.82×10 -7 2.21×10 -5 3.77×10 -6 2.1 ×10 -7 Acidification Pt 0.0002 6.94×10 -6 3.21×10 -7 2.17×10 -5 1.02×10 -6 1.7 ×10 -7 Land use Pt 0.0002 2.93×10 -6 2.19×10 -7 9.47×10 -6 8.43×10 -7 5.2 ×10 -8 Minerals Pt 0.0014 7.66×10 -6 4.00×10 -7 2.36×10 -7 3.79×10 -6 1.9 ×10 -7 Fossil fuels Pt 0.0051 3.82×10 -5 8.88×10 -6 0.0001 3.75×10 -5 2.6 ×10 -6

The CML method shows the same results as wind based hydrogen production except the electricity results. In the solar based hydrogen production, the abiotic depletion is about 4.30 ×10 -4 kg Sb eq, which was 1.06 ×10 -4 kg Sb eq. In the wind based electricity, global warming potential is 5.88 ×10 -2 kg CO 2 eq which was 1.38 ×10 -2 kg CO 2 eq. In the wind based electricity and ozone layer depletion is 1.52 ×10 -8 kg R-11 eq. which was 5.95 ×10 -10 kg R-11 eq.

Table 6.13b: Weighting results for hydrogen production using solar photovoltaic electricity.

Chemical Transport Transport, Electricity Impact category Unit Na-OH plant, , truck rail photovoltaic organic Carcinogens Pt 0.0004 4.82×10 -5 3.66×10 -6 0.0126 0.0028 Resp. organics Pt 2.11×10 -7 8.12×10 -7 1.06×10 -8 2.94×10 -6 3.27×10 -6 Resp. inorganics Pt 0.0004 0.00053 1.24×10 -5 0.0051 0.0014 Climate change Pt 0.0002 0.00010 2.76×10 -6 0.0009 0.0004 Radiation Pt 1.12×10 -5 9.40×10 -7 1.44×10 -7 3.51×10 -5 1.33×10 -5 Ozone layer Pt 4.76×10 -8 8.30×10 -8 9.55×10 -10 2.83×10 -7 4.29×10 -7 Ecotoxicity Pt 6.31×10 -5 2.99×10 -5 9.27×10 -7 0.0026 0.0004 Acidification Pt 2.11×10 -5 4.86×10 -5 8.12×10 -7 0.0001 6.86×10 -5 Land use Pt 1.40×10 -5 1.56×10 -5 8.05×10 -7 0.0006 5.93×10 -5 Minerals Pt 4.92×10 -5 1.04×10 -5 8.51×10 -7 0.0041 0.0006 Fossil fuels Pt 0.0006 0.0012 1.61×10 -5 0.0046 0.0030

Table 6.12: Impact assessment results for solar based hydrogen production method

Sodium Calcium Impact category Unit Soda Barite HCl chloride chloride Abiotic depletion kg Sb-eq 9.82 ×10 -4 1.56 ×10 -5 2.34 ×10 -6 4.94 ×10 -5 7.06 ×10 -6 -4 -5 -6 -5 -6 Acidification kg SO 2-eq 7.29 ×10 2.20 ×10 1.51 ×10 6.79 ×10 4.92 ×10 -4 -6 -6 -5 -6 Eutrophication kg PO 4-eq 5.43 ×10 6.41 ×10 1.02 ×10 2.00 ×10 2.95 ×10 -1 -3 -4 -3 -4 Global warming kg CO 2-eq 1.42 ×10 2.25 ×10 2.96 ×10 7.10 ×10 9.09 ×10 Ozone layer kg R-11-eq 8.59 ×10 -9 5.30 ×10 -11 1.45 ×10 -11 1.91 ×10 -10 1.45 ×10 -9

Table 6.13: Impact assessment results for solar based hydrogen production using CML method

Impact Sodium Transport, Chemical Electricity, Unit categories hydroxide truck plant photovoltaic Abiotic kg Sb-eq 1.55 ×10 -4 1.04 ×10 -4 8.47 ×10 -4 4.30 ×10 -4 depletion -4 -5 -4 -4 Acidification kg SO 2-eq 1.04 ×10 7.80 ×10 8.27 ×10 2.98 ×10 -5 -5 -4 -4 Eutrophication kg PO 4 -eq 7.21 ×10 2.07 ×10 6.62 ×10 1.88 ×10 -2 -2 -4 -2 Global warming kg CO 2-eq 2.07 ×10 1.40 ×10 1.20 ×10 5.88 ×10 Ozone layer kg R-11-eq 1.31 ×10 -9 2.08 ×10 -9 7.96 ×10 -4 1.52 ×10 -8

ant/RERU . CH U CH US U US

use Land Mineralsfuels Fossil

/ Eutrophication /

Sodium chloride, powder, at plant/RER U powder, atplant/RER chloride, Sodium U atBarite,plant/RER U atH2O,plant/RER in 30%acid, Hydrochloric atpl mix, production H2O, hydroxide, in 50% Sodium photovoltaic, atplant/ mix production Electricity, paper, 11.2%Disposal, water, sanitarytolandfill/ Transport, freight, rail/RER U Transport, freight, rail/RER

esidual material landfill/CH U landfill/CH material esidual

ange Radiation Ozonelayer Ecotoxicity Acidification

Weighting results charts for hydrogen production using solar photovoltaic solar using production hydrogen for charts results Weighting :

30 . 6 hydrogen via electrolysis using photovoltaic using electrolysis viahydrogen Soda,U powder, atplant/RER storage/CHU CaCl2, atchloride, regional Calcium U atplant/RER Sulphite, U plant,organics/RER/I Chemical water,electrolysis,0% NaCl tor sludge, Disposal, Transport,>16t,lorry fleet average/RER U Figure Figure /H / Weighting / /H tovoltaic';

Carcinogens Resp.organics Resp.inorganics ch Climate

9 8 7 6 5 4 3 2 1 0

21 20 19 18 17 16 15 14 13 12 11 10 t P m Method: Eco-indicator 99 (H) V2.08 / Europe EI 99 H 99 EI Europe / V2.08 (H) 99 Eco-indicator Method: Analyzing 1 kg 'hydrogen via electrolysis using pho using electrolysis via 'hydrogen kg 1 Analyzing

ant/RERU CH U CH U US

500a warming 40a layerdepletion Ozone

Sodium chloride, powder, at plant/RER U powder,at plant/RER chloride, Sodium U plant/RER atBarite, U H2O,at plant/RER in 30%acid, Hydrochloric atpl mix, H2O,production hydroxide, in 50% Sodium photovoltaic, plant/ at mix production Electricity, paper, 11.2%Disposal, water, tosanitarylandfill/ Transport, freight, rail/RER U Transport, freight,rail/RER

esidual material landfill/CH U landfill/CH material esidual

(CML method). chart for hydrogen production using solar photovoltaic solar using production hydrogen chart for

hydrogen via electrolysis using photovoltaic using electrolysis viahydrogen U Soda,powder, at plant/RER storage/CHU CaCl2, regional atchloride, Calcium U plant/RER at Sulphite, U plant,organics/RER/I Chemical water,electrolysis,0% NaCl r tosludge, Disposal, Transport,>16t,lorry fleet average/RER U Damage assessment Damage :

Characterization / 1990 ld, 31 tovoltaic'; . 6

Figure Abiotic depletion Abiotic Acidification Eutrophication Global

5 0

95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10

100 % Method: CML 2001 (all impact categories) V2.05 / Wor / V2.05 categories) impact (all 2001 CML Method: Analyzing 1 kg 'hydrogen via electrolysis using pho using electrolysis via 'hydrogen kg 1 Analyzing

6.4.2 Energy and Exergy Efficiencies Thermodynamic analysis of hydrogen production through sodium chlorine electrolysis using solar electricity is presented here. The energy efficiency for the process is calculated as 46.34% while exergy efficiency is about 45.41%. These efficiencies are less than the efficiencies in steam methane reforming and wind based hydrogen production.

Figure 6.32 shows the effect of changing the ambient temperature on energy and exergy efficiencies. Both efficiencies are decreasing on increasing the ambient temperature. However, this decrease in the efficiencies are not that much significant. The energy efficiency decreases slightly from 46.34% to 46.29% while exergy efficiency also increased to 45.41% from 45.38% as pressure rose to 350 K from 300 K. Figure 6.33 shows the effect of increasing the solar irradiation on energy and exergy efficiency of the solar based hydrogen production method. Irradiation is proportional to the power generation and increasing the electricity corresponds to increase in the input energy. This increase in the input energy causes both efficiencies to decrease because most of the photovoltaic cell has an efficiency of 20% and the rate at which input energy increases is greater than the rate of output. 0.4634 0.4542 Energy

Exergy 0.4633 0.4541

0.4632 0.454

0.4631 0.4539 Exergy efficiency Exergy Energy efficiency Energy

0.463 0.4538

0.4629 0.4537 300 310 320 330 340 350

Tο [K] Figure 6.32: Effect of variation ambient temperature on energy and exergy efficiencies of solar based hydrogen production.

0.54 0.52 Energy Exergy 0.52 0.5

0.5 0.48 0.48 0.46 0.46 0.44 Exergy efficiency Exergy Energy efficiency Energy 0.44

0.42 0.42

0.4 0.4 14000 15000 16000 17000 18000 2 Iο [W/m ]

Figure 6.33: Effect of variation of solar irradiation on energy and exergy efficiencies of solar based hydrogen production method. 6.5 Comparison of Various Options by CML-Method with Uncertainty Analyses In this section, environmental impacts of for one kilogram of hydrogen production for different processes are compared. The CML 2001 impact categories which are abiotic depletion potential, acidification potential, eutrophication potential, global warming potential, ozone depletion potential and human toxicity are considered for comparison purposes.

6.5.1 Abiotic Depletion Abiotic depletion potential is related with effect on non-living natural resources. It can be observed from Figure 6.34 that the abiotic depletion potential for steam methane reforming is much higher than all other methods. Using large amount of fossil fuels in SMR is responsible for this amount of depletion. From the Figure 6.34, abiotic depletion for SMR method is about 0.1309 kg Sb-eq. In other process such as electrolysis using mercury, diaphragm and membrane cell, abiotic depletion is almost similar with mercury

98 on top with a figure of 0.0079 kg Sb-eq. diaphragm cell with 0.0068 kg Sb-eq. and membrane cell with 0.0066 kg Sb-eq. In the solar photovoltaic electrolysis, abiotic depletion is least with 0.00026 kg Sb-eq after wind electrolysis with 0.0002 kg Sb-eq.

0.1400 0.1309 0.1200

0.1000 kg kg eqSb )

0.0800

0.0600

0.0400

Abiotic depletion ( Abiotic depletion 0.0200 0.0068 0.0066 0.0079 0.0002 0.0026 0.0000 Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis SMR wind photovoltaic diaphragm membrane mercury cell cell cell

Figure 6.34: Abiotic depletion per kg of hydrogen for different hydrogen production methods. 6.5.2 Acidification Potential Acidification potential comes as a result of acid deposition of acidifying pollutants on soil, water, biological organisms, ecosystems and materials. Figure 6.35 depicted that the acidification potential for steam methane reforming is the highest among all other methods. The value of acidification for SMR in the Figure 6.35 is about 0.0289 kg SO 2- eq. The second highest acidification potential is for electrolysis using mercury cell with

0.0053 kg SO 2-eq. and then for diaphragm and membrane cell with a difference of 0.0001 kg SO 2-eq. From the results of acidification potential it can be seen that wind based hydrogen production is most effective method of hydrogen production with minimum impact result. The acidification potential for wind based hydrogen is about 0.0002 kg

SO 2-eq. After wind based hydrogen production, solar photovoltaic hydrogen is an efficient way of hydrogen production with an acidification potential of 0.0021 kg SO 2eq.

6.5.3 Eutrophication Results of eutrophication are quite different than abiotic depletion and acidification. From Figure 6.36, hydrogen production using mercury cell contain the highest value of

99 eutrophication with 0.0037 kg phosphate-eq. SMR is the second highest method in terms of eutrophication potential with 0.0036 kg phosphate-eq. only 0.0001 value less than the mercury cell electrolysis. The membrane cell electrolysis has a value of 0.0032 kg phosphate-eq. followed by the diaphragm cell with 0.0031 kg phosphate-eq. Again wind based electrolysis has a minimum impact on the environment with eutrophication value 0.0001 kg phosphate-eq.; followed by the solar based hydrogen with an eutrophication impact of 0.00015 kg phosphate-eq.

0.0350 0.0289 ) 0.0300 eq 2 0.0250 kg SO kg 0.0200

0.0150

0.0100 0.0046 0.0045 0.0053

Acidification ( 0.0050 0.0021 0.0002 0.0000 Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis SMR wind photovoltaic diaphragm membrane mercury cell cell cell

Figure 6.35: Acidification potential per kg of hydrogen for different hydrogen production methods.

0.0040 0.0037 0.0036 0.0035 0.0032 0.0031 0.0030

0.0025

0.0020 0.0015 0.0015

0.0010

0.0005 0.0001 Eutrophication (kg phosphate-eq ) 0.0000 Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis SMR wind photovoltaic diaphragm membrane mercury cell cell cell

Figure 6.36: Eutrophication potential per kg of hydrogen for different hydrogen production methods.

100

6.5.4 Global Warming Potential Global warming potential (GWP) is the result of human emissions on the radioactive forcing of the atmosphere which is responsible for temperature rise at the earth’s surface and this is generally related to ‘greenhouse effect”. It can be observed from Figure 6.37 that the most important contributions for global warming potential come from utilization of natural gas in steam methane reforming method. SMR has the value of 11.956 kg CO 2- eq. The rest of the methods are far behind than SMR. The lowest value of global warming potential comes under the wind based electrolysis with 0.0325 kg CO 2-eq. After wind solar based electrolysis can be seen in the Figure 6.37with an amount of 0.37 kg CO 2-eq. Hydrogen production through electrolysis using mercury contain relatively higher amount of global warming potential than diaphragm and membrane cell. The value of mercury cell is about 1.051 kg CO 2-eq, for diaphragm cell it is 0.909 kg CO 2-eq. and for membrane cell the value of global warming potential is about 0.8872 kg CO 2-eq which is minimum among three cells.

14.0000 11.9567 12.0000 eq ) 2 10.0000

8.0000

6.0000

4.0000 Global warming (kg CO Global warming 2.0000 0.9090 0.8872 1.0510 0.0325 0.3700 0.0000 Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis SMR wind photovoltaic diaphragm membrane mercury cell cell cell

Figure 6.37: Global warming potential per kg of hydrogen for different hydrogen production methods. 6.5.5 Ozone Layer Depletion Ozone layer depletion is the weakening of the ozone layer as a result of emissions. This thinning of ozone layer is responsible for a greater portion of solar UV-B radiation reaching the earth’s surface. From Figure 6.38 , almost all of the method has minimum contribution on

101 ozone layer depletion except steam methane reforming with a value of 3.0 x 10 -06 kg R-11-eq. The hydrogen production via wind based electrolysis contributes the minimum ozone layer depletion with 2.24 × 10 -09 kg R-11-eq.

3.50E-06 3.00E-06 3.00E-06

2.50E-06

2.00E-06

1.50E-06

1.00E-06

Ozone layer layer depletion(kg OzoneR11-eq ) 5.00E-07 2.24E-09 3.70E-08 5.99E-08 5.95E-08 6.65E-08 0.00E+00 Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis SMR wind photovoltaic diaphragm membrane mercury cell cell cell

Figure 6.38: Ozone layer depletion per kg of hydrogen for different hydrogen production methods. 6.5.6 Human Toxicity Human toxicity category deals with the effects of toxic substances on the human environment. Figure 6.39 shows the values of human toxicity of different hydrogen production methods. It can be seen that steam methane reforming and photovoltaic electrolysis contributed large amount of human toxicity with SMR 3.179 kg 1, 4- dichlorobenzene equivalents and for photovoltaic based hydrogen it is 0.8034 kg 1, 4- dichlorobenzene eq. Diaphragm cell and membrane cell sharing almost equal amount of human toxicity of 0.4221 kg 1,4 DB-eq. and 0.4229 kg 1,4 DB-eq. Again the wind based electrolysis has the minimum contribution in environmental impact which is 0.0782 kg 1, 4 DB-eq. in this case.

102

3.5000 3.1796 3.0000

2.5000

2.0000

1.5000

1.0000 0.8034 0.4221 0.4229 0.4489 0.5000

Human toxicity (kg (kg 1,4-DBHuman eqtoxicity ) 0.0782 0.0000 Electrolysis Electrolysis Electrolysis Electrolysis Electrolysis SMR wind photovoltaic diaphragm membrane mercury cell cell cell

Figure 6.39: Human toxicity per kg of hydrogen for different hydrogen production methods.

6.5.7 Radiation Radiation includes impacts arising from releases of radioactive substances along with direct exposure to radiation, such as building materials. If the radiation level is high, it can be harmful to both human as well as animals. Figure 6.40 show the radiation results for different hydrogen production methods. The main contributor in the radiation is the hydrogen production form electrolysis using mercury cell with 1.66 x 10 -08 DALY.

1.80E-08 1.66E-08 1.60E-08 1.42E-08 1.37E-08 1.40E-08

1.20E-08

1.00E-08

8.00E-09

6.00E-09 Radialtion (DALY) 4.00E-09 3.10E-09 3.43E-09 2.46E-09 2.00E-09

0.00E+00 Hydrogen via hydrogen via Hydrogen Hydrogen Hydrogen Hydrogen, electrolysis eletrolysis diaphragm membrane mercury cell SMR (wind) photovoltaic cell cell

Figure 6.40: Radiation per kg of hydrogen for different hydrogen production methods.

103

5.5.8 Photochemical Oxidation Photo-oxidants formed by the influence of ultraviolet light, through photochemical oxidation of Volatile Organic Compounds (VOCs) and carbon monoxide in the presence of nitrogen oxides. Figure 6.41 show the photochemical oxidation for different hydrogen production methods in which SMR is the largest contributor of photochemical oxidation with 1.98 x 10 -03 kg Ethene-eq. The minimum contributor in this category is the wind based hydrogen methods where renewable energy is utilized to reduced pollution and other impacts. The photochemical oxidation for wind hydrogen production is 9.04 x 10 -05 kg Ethene-eq. These results encouraged that renewable based hydrogen has minimum environmental emissions as compared to fossil fuel based hydrogen production .

2.50E-03

1.98E-03 2.00E-03

1.50E-03

1.00E-03

5.00E-04 1.85E-04 1.81E-04 2.12E-04

Photochemical Oxidation (kg Oxidation(kg Ethene-eq)Photochemical 9.04E-05 1.04E-04 0.00E+00 Hydrogen via hydrogen via Hydrogen Hydrogen Hydrogen Hydrogen, electrolysis eletrolysis diaphragm cell membrane cell mercury cell SMR (wind) photovoltaic

Figure 6.41: Photochemical oxidation per kg of hydrogen for different hydrogen production methods 6.6 Uncertainty Analyses of Steam Methane Reforming Data used in the LCA have uncertainties and the result will slightly deviate from actual value. For example, SO x emission during burning of 1 kg of heavy oil is about 10 grams. However, in 95% of the cases the value lies between 5 and 15 grams, depending on the sulphur content of the oil. For this purpose, uncertainty analysis of results is necessary.

The uncertainty data for producing 1 kg of hydrogen through steam methane reforming are shown in Table 6.14 and all the values are calculated at the 95%

104

confidence level. The original abiotic depletion value for SMR method is about 0.1309 kg Sb-eq. and uncertainty analysis calculated the error chances of 95% surety. The minimum and maximum values at 95% confidence interval are shown in Figure 6.42 which result in 0.1309 ± 0.040 kg Sb-eq. The measured standard error of mean for ADP is about 0.005 with coefficient of variation is 15.50%.

Table 6.14: Uncertainty data for hydrogen production through SMR Impact Coefficient of Std. err. of Unit Mean Median SD category Variation mean Abiotic depletion kg Sb eq 0.132 0.130 0.020 15.50% 0.005 Acidification kg SO2 eq 0.029 0.028 0.004 13.80% 0.004

Eutrophication kg PO 4 eq 0.004 0.003 0.001 15.60% 0.005

Global warming kg CO 2 eq 12 12 0.439 3.67% 0.001 Human toxicity kg 1,4-DB eq 3.19 3.14 0.244 7.63% 0.002 Ionising DALYs 2.5E-09 1.45E-09 3.93E-09 153% 0.049 radiation Ozone layer kg CFC-11eq 3.E-06 2.31E-06 2.28E-06 75.60% 0.024 Photochemical kg C H eq 0.002 0.002 0.000277 13.90% 0.004 oxidation 2 4

Characterization Abiotic depletion

0.024

0.022

0.02

0.018

0.016

0.014

0.012

Probability0.01

0.008

0.006

0.004

0.002

0 0.096 0.099 0.102 0.104 0.107 0.109 0.112 0.114 0.117 0.119 0.122 0.124 0.127 0.13 0.132 0.135 0.137 0.14 0.142 0.145 0.147 0.15 0.152 0.155 0.158 0.16 0.163 0.165 0.168 0.17 0.173 0.175 0.178 kg Sb eq Figure 6.42: Uncertainty analysis results of SMR method for abiotic depletion. For the global warming potential, the mean and median value is 12 which has a coefficient of variation of about 3.67% and from Figure 6.43 it can be written as 11.957 ±

0.8 kg CO 2-eq. at 95% confidence interval. This slight variation in value is due to the difference in maintenance and other operating parameters of the process.

105

0.024

0.022

0.02

0.018

0.016

0.014

0.012

Probability0.01

0.008

0.006

0.004

0.002

0 11.211.2 11.3 11.4 11.4 11.5 11.5 11.6 11.7 11.7 11.8 11.8 11.9 11.9 12 12 12.1 12.1 12.2 12.2 12.3 12.3 12.4 12.5 12.5 12.6 12.6 12.7 12.7 12.8 12.9 12.9 13 13 13 13.1 kg CO2 eq Figure 6.43: Uncertainty analysis results of SMR method for global warming.

6.7 Uncertainty Analyses of Solar and Wind based Hydrogen Production The comparison of uncertainty analysis between wind and solar based hydrogen production is conducted on the 95% confidence level. The uncertainty value is given in Table 6.15 where A represents the data of wind based electrolysis and B is the solar based hydrogen production. The difference of the abiotic depletion potential values is about 29.2% where mean and median values are -0.0003. From the probability of getting -3.6e- 4 kg Sb-eq. is 0.07 which is the maximum. These uncertainties results are because of the slight difference in the assumed data. However, this minor difference indicated that the results of the impact categories give the real picture of the emissions. Table 6.15: Uncertainty data for hydrogen production through wind and solar energy

Impact Coefficient Std. err. of A >= B Mean Median 2.50% category of Variation mean Abiotic depletion 29.20% -0.0003 -0.0003 -310% -0.00212 -0.0979 Acidification 34.60% -0.0002 -0.0002 -456% -0.00201 -0.144 Eutrophication 36.70% -0.0001 -0.0001 -588% -0.00156 -0.186 Global warming 29.40% -0.0412 -0.0413 -314% -0.292 -0.0993 Human toxicity 48.90% 0.0002 -0.0109 3.67E+03 -1.09 116 Ionising radiation 31.90% -3.4×10 -10 -1.82×10 -10 -562% -3.76×10 -9 -0.178 Ozone layer 2.90% -2.32×10 -8 -2.28×10 -8 -57.80% -4.95×10 -8 -0.0183

106

0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04

Probability0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 -2.33e-3 -2.17e-3 -2e-3 -1.84e-3 -1.59e-3 -1.35e-3 -1.1e-3 -9.39e-4 -6.93e-4 -5.3e-4 -3.66e-4 -1.21e-4 4.31e-5 2.07e-4 3.7e-4 5.34e-4 6.97e-4 8.61e-4 1.02e-3 1.19e-3 1.35e-3 1.52e-3 1.68e-3 Uncertainty analysis of 1 kg 'Hydrogen via electrolysis (wind)' (A) minus 1 kg 'hydrogen via electrolysis using photovoltaic' (B), Figure 6.44: Uncertainty analysis results of wind and solar based hydrogen production for abiotic depletion The comparison between wind and solar hydrogen based on global warming potential is also conducted. The uncertainty data for global warming potential is also shown in Table 6.15 and Figure 6.44 shows the uncertainty bar diagram. The maximum

probability difference is about 0.085 on the value of -0.046 kg CO 2 emissions. For human

toxicity, the mean and median values are 0.0002 and -0.0109 kg CO 2-eq. Moreover, the

maximum probable value is around -0.01 kg CO 2-eq. 6.8 Comparison of Hydrogen and Gasoline Fuels in Vehicle Energy consumption in vehicle is developing large amount of pollution level on environment and about 26.6% of energy is consumed in the transportation sector all over the world. Researchers have been investigating various options for alternatives to fossil fuels and propose hydrogen as a potential one to replace conventional fuels for vehicles. In this section, a case study is presented on the basis of the fuels used in vehicle. The selected fuels are hydrogen and gasoline. The vehicle cycle are studied from literature such as Weiss et al. (2000), Hussain et al. (2007) and Sorensen (2004). The vehicle cycle has major stages in its production such as vehicle material production, vehicle assembly and vehicle use.

107

In vehicle material production, all the greenhouse gas emissions and energy use in the material production are evaluated. Regular automobile consume about 890 kg of ferrous metals, 100 kg of different plastics, roughly 80 kg of aluminum, and about 200 kg of other materials (Weiss et al., 2000). Furthermore, PEM fuel cell powered automobile incorporates polymer membrane, platinum, graphite, etc. In vehicle assembly, greenhouse gases and energy requirement in the supply chain of vehicle parts are included. All the automobile parts are assembled and this process is associated with several difficult steps. In the use of vehicle, all the emissions and energy consumption are taken into account including vehicle maintenance throughout its life. Specific distance value is required for the life of automobile and Sorensen (2004) assumed the distance of 300,000 km. For comparison purposes, the assumption is made for energy consumption in PEMFC powered automobile is 650 kJ/km and for internal combustion engine it is about 2730 kJ/km.

0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 Probability0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 -0.324 -0.301 -0.278 -0.255 -0.232 -0.209 -0.186 -0.163 -0.14 -0.117 -0.093 -0.07 -0.047 -0.024 -0.001 0.022 0.045 0.068 0.091 0.114 0.137 0.16 0.184 0.207 0.23 Uncertainty analysis of 1 kg 'Hydrogen via electrolysis (wind)' (A) minus 1 kg 'hydrogen via electrolysis using photovoltaic' (B), Figure 6.45: Uncertainty analysis results of wind and solar based hydrogen production for global warming potential.

108

Table 6.16: GHG emission in vehicle cycle

Hydrogen Vehicle Gasoline Vehicle Vehicle Cycle (Tons of CO 2) (Tons of CO 2) Vehicle material production 3.63 3.52 Vehicle assembly 1.65 1.76 Vehicle use 0 59.03 Total 5.28 64.31

0.075

0.07 0.065 0.06 0.055

0.05 0.045 0.04 0.035 Probability 0.03 0.025 0.02 0.015 0.01

0.005 0 -1.26 -1.16 -1.06 -0.96 -0.86 -0.76 -0.66 -0.56 -0.46 -0.36 -0.26 -0.16 -0.06 0.03 0.13 0.23 0.33 0.43 0.53 0.63 0.73 0.83 0.93 1.03 1.13 Uncertainty analysis of 1 kg 'Hydrogen via electrolysis (wind)' (A) minus 1 kg 'hydrogen via electrolysis using photovoltaic' (B),

Figure 6.46: Uncertainty analysis results of wind and solar based hydrogen production for human toxicity

The greenhouse gas emission from both types of vehicle is compared on the basis of available literature. Vehicle cycle related emissions are listed in Table 6.16 based on

300,000 km and it shows the gasoline vehicle has the highest emission of 59 tons of CO 2. While on the other hand, hydrogen vehicle has no emission on the environment throughout its life cycle. However, in the vehicle material production, the hydrogen based vehicle has more emissions than the gasoline vehicle. This is due to the platinum and graphite conventional material consumption in the manufacturing of hydrogen vehicle as shown in Figure 6.47.

109

Hydrogen Vehicle (Tons of CO2) Gasoline Vehicle (Tons of CO2) 70 64.31 59.03 60

GHG GHG emissions, Tons of CO 10 3.63 3.52 5.28 1.65 1.76 0 0 Vehicle material productionVehicle assembly Vehicle use Total

Figure 6.47: GHG emissions of vehicle cycle The energy consumption data listed in Table 6.17 and Figure 6.53 show that the gasoline vehicle has the highest energy consumption throughout its life when it covered the distance of 300,000 km. This 819 GJ of energy is responsible for large amount of emissions in terms of CO 2, SO 2 and NO x. The difference in the amount of energy consumed between the hydrogen vehicle and gasoline vehicle is about 624 GJ of energy.

Table 6.17: Energy consumption in vehicle cycle

Vehicle Cycle Hydrogen Vehicle (MJ) Gasoline Vehicle (MJ)

Vehicle material production 54600 49800 Vehicle assembly 24300 25500 Vehicle use 195000 819000 Total 273900 894300 (Source Hussain et al., 2007)

Energy consumption in vehicle assembly step is higher for the gasoline vehicle which is 255 GJ as compared to the hydrogen vehicle which is 243 GJ energy as shown in Figure 6.48. Several complex parts are assembled for internal combustion engine such as piston, combustion system etc. However, the hydrogen vehicle consumed more energy in the vehicle material production cycle. About 48 GJ more energy is consumed in the material production for the hydrogen vehicle.

110

1000000 Hydrogen Vehicle (MJ) Gasoline Vehicle (MJ) 894300 900000 819000 800000 700000 600000 500000 400000 273900 300000 195000 200000 Energy Consumption (MJ) Consumption Energy 49800 100000 54600 24300 25500 0 Vehicle material Vehicle assembly Vehicle use Total production

Figure 6.48: Energy consumption of vehicle cycle

Other steps of vehicle cycle include vehicle distribution and vehicle disposal. In the vehicle distribution all the energy requirement and GHGs emission are incorporated during the transport of vehicles from manufacturing and assembly center to the dealers. On the other hand, in the vehicle disposal, the vehicle is disposed for scrap. The overall energy required in this process is the sum of all energy needed to move all scrap material to the shredder and other disposal material. The energy consumption in vehicle distribution requires more energy than the vehicle distribution. This step consumes about 6 times more energy than vehicle disposal as shown in Table 6.18.

Table 6.18: Energy consumption and GHGs emission comparison in vehicle cycle

Hydrogen Gasoline Hydrogen Vehicle Gasoline Vehicle Vehicle Cycle Vehicle (MJ) Vehicle (MJ) (Tons of CO 2) (Tons of CO 2) Vehicle distribution 2100 2100 0.11 0.11 Vehicle disposal 300 300 0 0

111

2500 Vehicle distribution Vehicle disposal

2000

1500

1000 Energy Energy consumption (MJ) 500

0 Hydrogen Vehicle (MJ) Gasoline Vehicle (MJ)

Figure 6.49: Energy consumption in vehicle distribution and vehicle disposal

Fuel cycle is another important process which involves several steps for the production of fuel. Emission throughout the production of hydrogen fuel is calculated in the previous section, where several processes are studied. This fuel cycle is studied by Weiss et al. (2000) and Hussain et al., (2007) which include the energy consumption in the conversion of natural gas to hydrogen and crude oil to gasoline. Moreover, total greenhouse gases emission is also compared between hydrogen and gasoline for vehicle. In this thesis, the damage on the environment is measured in different impact categories and comparison is made between 1 kg of hydrogen through wind electrolysis with 1 kg of gasoline produced in refinery.

Figure 6.50 shows the comparison between hydrogen and gasoline production. The emissions are calculated on the bases of 1 kg of fuel. Abiotic depletion is 100 times higher in gasoline production as compared to hydrogen through wind electrolysis. Large amount of non-living natural resources are consumed in gasoline production such as crude oil, coal, heavy metals in the refinery and raw material extraction. The acidification emission is also higher in gasoline production in comparison with hydrogen production.

About 0.0031 kg SO 2-eq. is emitted and deposited on the environment in gasoline fuel production. Acidification is the acidifying pollutants deposit on the soil, surface and

112 ground water and other biological organisms. However, eutrophication emissions are comparatively higher in hydrogen fuel production which is about 0.0014 kg PO 4-eq.

Eutrophication measure the excess nutrients in terms of NO x and PO 4 and all the excess nutrients emitted on the environment is also damaging the ecosystem quality.

0.0300

0.0246 0.0250

0.0200

0.0150

Emissions (kg) Emissions 0.0100

0.0050 0.0031 0.0023 0.0019 0.0014 0.0005 0.0000 Abiotic depletion (kg Sb-eq.) Acidification (kg SO2-eq) Eutrophication (kg PO4-eq.) Hydrogen wind electrolysis Gasoline at Refinery

Figure 6.50: Fuel production comparison in terms of emission

0.9000 0.7815 0.8000

0.7000 0.6402

0.6000

0.5000

0.4000 0.3250

Emissions (kg) Emissions 0.3000

0.2000 0.1532

0.1000

0.0000 Global warming (kg CO2-eq.) Human toxicity (kg DB-eq.) Hydrogen wind electrolysis Gasoline at Refinery

Figure 6.51: Fuel production comparison in terms of emissions

113

The global warming potential in gasoline production is greater than hydrogen fuel production. The value of global warming potential is about 0.6402 kg CO 2-eq. whereas in hydrogen it is about 0.325 kg CO 2-eq. All the greenhouse gases emissions are higher in crude oil distillation which is also an energy intensive process. Again in this process, large amount of fossil fuel resources are burnt to produce gasoline fuel. On the other side, human toxicity values are higher in hydrogen fuel production which is about 0.7815 kg dichlorobenzene equivalent. Toxic chemicals which are hazardous to the human health includes heavy metals, benzene emissions etc.

The benefit of using hydrogen based vehicle is presented through vehicle cycle case study. Several previous studies are combined for energy consumption and GHGs emission to give comparison between hydrogen vehicle and gasoline vehicle. Different periods of vehicle cycle are also compared. It is found that during the vehicle cycle of an automobile, energy consumption and GHGs emissions of gasoline vehicle are higher than that of hydrogen automobile and the largest contributor to the energy consumption and GHGs emissions is the vehicle use stage of the gasoline vehicle cycle.

114

Conclusions and Recommendations 7.1 Conclusions This thesis study investigated the environmental impacts of hydrogen production using different methods. Even though hydrogen is a clean energy carrier, the negative impacts during its production cannot be disregarded, and therefore life cycle analyses for various scenarios were implemented.

LCA methodology was implemented in order to calculate the environmental impact of the hydrogen production. LCA software called SimaPro is used in which several methods are available. In this study, the Eco-indicator 99 and CML 2001 methods are implemented. Three damage categories were expressed such as damage to human health, damage to ecosystem quality and damage to resources. After analyzing the systems in terms of environmental impacts, thermodynamic analyses were conducted to study the systems energetically and exergetically. The vehicle cycle was studied in order to compare the hydrogen fuel based vehicle with conventional vehicle using several steps. The systems energy and exergy efficiencies were calculated. Moreover, parametric studies were also conducted to examine the effects of different parameters on the system .

The study concluded that hydrogen production from steam methane reforming has the maximum load on the environment in terms of emissions and other impact categories. However, this method has the highest energy and exergy efficiencies because large quantity of hydrogen is produced with almost an equal quantity of input energy (electricity) as compared to other methods. The comparative environmental impact findings of the studied system are concluded below;

• Using the CML method for impact categories, the abiotic depletion for SMR is found to be 0.131 kg Sb eq. which is the highest among all methods. The second highest abiotic depletion value comes under electrolysis using the mercury cell which has 0.00786 kg Sb eq. and then with the diaphragm cell with 0.00678 kg Sb eq, the membrane cell with 0.0061 kg Sb eq., the solar electrolysis with 0.0026 and the wind electrolysis with 0.00228 kg Sb eq.

115

• The global warming potential is highest in SMR of hydrogen production which is

12 kg CO 2 eq. After SMR method, electrolysis using the mercury cell has 1.05 kg

CO 2 eq. but in the diaphragm cell with 0.909 kg CO 2 eq. the membrane cell with

0.887 kg CO 2 eq, the solar based hydrogen with 0.37 kg CO 2 eq. and the wind

based with 0.325 kg CO 2 eq. • The thermodynamic results suggested that steam methane reforming is the most efficient method of hydrogen production because the amount of hydrogen energy produced as output in the system is larger than any other method. The energy efficiency of the system in this method is about 76.8% and the exergy efficiency is about 72.4%. • During the vehicle cycle, the gasoline vehicle has the highest energy consumption throughout its life when covered a distance of 300,000 km. Moreover, it also has

the highest GHGs emission which is about 50 tons of CO 2. On the other hand, a hydrogen vehicle has no emission on the environment throughout its life cycle.

In summary, hydrogen energy is projected to play a key role in a pollution free environment. However, the negative impacts during its production cannot be disregarded. This thesis investigated the environmental impact of hydrogen which shows that steam methane reforming of natural gas has the highest emissions which is responsible for damage to human health, damage to ecosystem quality and damage to resources. In order to replace this method, renewable based hydrogen production was also studied which suggested that solar and wind based hydrogen production have minimum effects on the environment.

7.2 Recommendations This study might help policy makers to put more effort in hydrogen production using renewable energy, since this thesis found that hydrogen production from renewable sources is a sustainable way. The following recommendations are provided for future works:

• Methods such as coal gasification, plasma gasification, partial oxidation, thermochemical, gasification of biomass and photochemical hydrogen production should be investigated through life cycle analysis. 116

• Geothermal, tidal and other renewable energy based hydrogen production methods should also be studied by using life cycle assessment methodology. • More detailed LCA models should be designed to get more accurate results of the studied systems. • Exergoenvironmental and exergoeconomic analysis should be performed for different hydrogen production methods. • Specific • Comprehensive optimization studies should be conducted to determine optimum operating parameters for hydrogen production. • Other types of vehicles for different life times should also be studied for comparison purposes.

117

References Acar C, Dincer I “Comparative assessment of hydrogen production methods from renewable and non-renewable sources” International Journal of Hydrogen Energy 39 (2014) 1–12 Agnieszka K “Hydrogen by Thermo-catalytic Decomposition of Methane” Master’s thesis, Southern Illinois University (2003) Akyuz E, Otkay Z, Dincer I “Performance investigation of hydrogen production from a hybrid wind-PV system” International Journal of Hydrogen Energy 37 (2012) 16623 – 16630 Alferedo U, Gandia L. M., Sanchis P “Hydrogen Production from Water Electrolysis: Current Status and Future Trends” Proceedings of the Institute of Electrical and Electronic Engineers 100 (2012) Althaus H J, Chudacoff M, Hischier R, Jungbluth N, Osses M and Primas A “Life cycle inventories of chemicals” Ecoinvent report 8, EMPA Dubendorf, Swiss Center for Life Cycle Inventories, Dubendorf (2007) Balta M. T., Dincer I, Hepbasli A “Energy and exergy analyses of a new four-step copper chlorine cycle for geothermal-based hydrogen production” Energy (2010) 3263 – 3272 Balta M. T., Dincer I, Hepbasli A “Potential methods for geothermal-based hydrogen production” International Journal of Hydrogen Energy 35 (2010) 4949 – 4961 Bockris J. M. “The origin of ideas on a Hydrogen Economy and its solution to the decay of the environment” International Journal of Hydrogen Energy 27 (2002) 731 – 740 Brown L. F. “A comparative study of fuels for on-board hydrogen production for fuel-cell-powered automobiles” International Journal of Hydrogen Energy 26 (2001) 381 – 397 Casper M. S. “Hydrogen Manufacture by Electrolysis, Thermal Decomposition and Unusual Techniques” Chemical Technology Revolution 102 (1978), 1 – 362 Cetinkaya E, Dincer I, Naterer G. F. “Life cycle assessment of various hydrogen production methods” International Journal of Hydrogen Energy 37 (2012) 2071 - 2080 Cohce M. K. “Thermodynamic Performance Assessment of Three Biomass Based Hydrogen Production Systems” Master’s thesis, University of Ontario Institute of Technology, (2010) Cohce M. K., Dincer I, Rosen M. A. “Energy and exergy analyses of a biomass- based hydrogen production system” Bioresource Technology 102 (2011) 8466 - 8474 Cormos C “Hydrogen production from fossil fuels with carbon capture and storage based on chemical looping systems” International Journal of Hydrogen Energy 36 (2011) 5960 – 5971

118

Cormos C, Starr F, Tzimas E, Peteves S “Innovative concepts for hydrogen production processes based on coal gasification with CO 2 capture” International Journal of Hydrogen Energy 33 (2008) 1286 – 1294 Curran M. A. “Life Cycle Assessment Handbook: A Guide for Environmentally Sustainable Products” John Wiley and Sons (2012) Curran M. A., “Life cycle assessment: Principles and practice”, Scientific Applications International Corporation (SAIC) (2006) R-06/060 Daj R, Dell R. M., “Fuels - hydrogen production coal gasification” Encyclopedia of Electrochemical Power Sources (2009) 276 – 292 Dincer I “Technical, environmental and exergetic aspects of hydrogen energy systems” International Journal of Hydrogen Energy 27 (2002) 265 – 285 Dincer I, “Green methods for hydrogen production” International Journal of Hydrogen Energy 37 (2012) 1954-1971 Dincer I, Joshi A. S. “Solar based hydrogen production systems” Springer, New York (2013) Emmanuel Z, Elli V, Nicolaos L, Christodoulou N, George N. K. “A review on water electrolysis” Center for Renewable Energy Sources, Greece (2004) Ghosh S, Dincer I “Development and analysis of a new integrated solar-wind- geothermal energy system” Solar Energy 107 (2014) 728-745 Goswami D.Y., Mirabal S.T., Goel N., Ingley H. A., “A review of hydrogen production technologies” Proceedings of the ASME First International Conference on Fuel Cell Science, Engineering and Technology (2003) 21 – 23 Granovskii M, Dincer I, Rosen M. A. “Air pollution reduction via use of green energy sources for electricity and hydrogen production” Atmospheric Environment 41 (2007a) 1777 –1783 Granovskii M, Dincer I, Rosen M. A. “Environmental and economic aspects of hydrogen production and utilization in fuel cell vehicles” Journal of Power Sources 157 (2006) 411–421 Granovskii M, Dincer I, Rosen M. A. “Exergetic life cycle assessment of hydrogen production from renewables” Journal of Power Sources 167 (2007b) 461– 471 Granovskii M, Dincer I, Rosen M. A. “Greenhouse gas emissions reduction by use of wind and solar energies for hydrogen and electricity production: Economic factors” International Journal of Hydrogen Energy 32 (2007c) 927 – 931 Hajjaji N, Pons M. N., Renaudin V, Houas A “Comparative life cycle assessment of eight alternatives for hydrogen production from renewable and fossil feedstock” Journal of Cleaner Production 44 (2013) 177 – 189 Hussain M. M., Dincer I, Li X “A preliminary life cycle assessment of PEM fuel cell powered automobiles” Applied Thermal Engineering 27 (2007) 2294 – 2299

119

ISO. “Environmental management - life cycle assessment - requirements and guidelines (ISO 14044)” International Organization for Standardization, Geneva, (2006) Huang J, Dincer I “Parametric analysis and assessment of a coal gasification plant for hydrogen production” International Journal of Hydrogen Energy 39 (2014) 3294 – 3303 Jensen A, Christiansen K, Elkington J “Life Cycle Assessment – a guide to approaches, experiences and information sources” Environmental Issues Series, EEA United Kingdom (1997) Jiang Y, Mingyang T, Liu P. K, Sahimi M, Tsotsi T. T. “Hydrogen Production from Biomass-Derived Syngas Using a Membrane Reactor Based Process” Industrial and Engineering Chemistry Research 53 (2013) 819 – 827 Joshi A. S., Dincer I, Reddy B. V. “Performance analysis of photovoltaic systems: A review” Renewable and Sustainable Energy Reviews 13 (2009) 1884–1897 Joshi A. S., Dincer I, Reddy B “Solar hydrogen production: A comparative performance assessment” International Journal of Hydrogen Energy 36 (2011) 11246 – 11257 Kalamaras C. M., Efstathiou A. M. “Hydrogen Production Technologies: Current State and Future Developments” Conference Papers in Energy, Hindawi Publishing Corporation (2013) 1 – 9 Koroneos C, Dompros A, Roumbas G, Moussiopoulos N “Life cycle assessment of hydrogen fuel production processes” International Journal of Hydrogen Energy 29 (2004) 1443 – 1450 Lewis M. A. “Update on the Cu–Cl cycle R & D effort In: Workshop of the ORF Hydrogen Project at AECL Chalk River Laboratories” Ontario, October 17, 2008 25 – 33 Maack M. H., Skulason J. B. “Implementing the hydrogen economy” Journal of Cleaner Production 14 (2006) 52–64 Marbán G, Valdés-Solís T “Towards the hydrogen economy?” International Journal of Hydrogen Energy 32 (2007) 1625 – 1637 Marcus G. H. Levin E “New designs for the nuclear renaissance” Physics Today 54 (2002) 54–64 Mark G, D Schryver D, Michiel O, Sipke D, Roest D “Introduction to LCA with SimaPro 7” Pre-consultants (2010a) Mark G, Michiel O, Schryver A D, Marsia V, Sander H “ SimaPro database manuals: Method library” Prs-consultants (2010b). Midilli A, Ay M, Dincer I, Rosen M. A. “On hydrogen and hydrogen energy strategies I: current status and needs” Renewable and Sustainable Energy Reviews 9 (2005) 255–271

120

Midilli A, Dincer I “Key strategies of hydrogen energy systems for sustainability” International Journal of Hydrogen Energy 32 (2007) 511-524

Molburg J C, Richard D “Hydrogen from steam methane reforming with CO 2 with CO 2 capture” Paper for 20th Annual International Pittsburgh Coal Conference, Pittsburgh (2003) 15 – 19 Naterer G F, Dincer I, Zamfirescu C, “Hydrogen Production form nuclear energy” Springer (2013) Naterer G F, Gabriel K, Wang Z. L., Daggupati V. N., Gravelsins R, “Thermochemical hydrogen production with a copper-chlorine cycle. I: oxygen release from copper oxychloride decomposition”, International Journal of Hydrogen Energy 33(2008) 5439-5450. Nirmal V, Reddy B. V., Rosen M. A. “Hydrogen production from coal gasification for effective downstream CO2 capture” International Journal of Hydrogen Energy 35 (2010) 4933 – 4943 Olateju B, Kumar A “Hydrogen production from wind energy in Western Canada for upgrading bitumen from oil sands” Energy 36 (2011) 6326 – 6339 Ozbilen A, Dincer I, Rosen M. A. “A comparative life cycle analysis of hydrogen production via thermochemical water splitting using a Cu-Cl cycle” International Journal of Hydrogen Energy 36 (2011) 11321-11327 Ozbilen A, Dincer I, Rosen M. A. “Exergetic life cycle assessment of a hydrogen production process” International Journal of Hydrogen Energy 37 (2012) 5665 – 5675 Ozbilen A. Z. “Life cycle assessment of nuclear-based hydrogen production via thermochemical water splitting using a copper-chlorine (Cu-Cl) cycle” Master Thesis (2010) University of Ontario Institute of Technology. Pant K. K., Gupta R. B. “Fundamentals and use of hydrogen as fuel” Taylor and Francis Group (2009) Ray E “Hydrogen production from steam reforming” Chemical Engineering 117 – 128 (2010) Richa K, Biddhi D, Shawney R L “Comparison of environmental and economic aspects of various hydrogen production methods” Renewable and Sustainable Energy Reviews 12 (2008) 553 – 563 Richa K, Buddhi D, Sawhney R. L. “Sources and technology for hydrogen production: a review” International Journal of Global Energy Issues 21 (2004) 154 – 78 Rifkin J, “The Hydrogen Economy” (2002) New York, 189. Rosen M. A. “Thermodynamic comparison of hydrogen production processes”, International Journal of Hydrogen Energy, 21 (1996) 349-365.

121

Ryland D. K., Li H, Shandankar R “Electrolytic hydrogen generation using CANDU nuclear reactors” International Journal of Energy Research (2007) 31 1142 – 1155 Sami M, Annamalai K, Wooldridge M “Co-firing of coal and biomass fuel blends” Progress in Energy and Combustion Science 27 (2001) 171–214 Serban M, Lewis M. A., Basco J. K., “Kinetics study of the hydrogen and oxygen production reactions in the copper-chloride thermochemical cycle”, AIChE 2004 Spring National Meeting New L A. Simpson A, Lutz A “Exergy analysis of hydrogen production via steam methane reforming” International Journal of Hydrogen Energy 32 (2007) 4811–4820 Sorensen B. “Total life-cycle assessment of PEM fuel cell car” Energy and Environment Group, Roskilde University, Denmark, (2004) Spath P L, Mann M K “Life cycle assessment of hydrogen production via natural gas steam reforming” National Renewable Energy Laboratory NREL/TP-570-27637 (2001) Spath P L, Mann M K “Life cycle assessment of hydrogen production via wind/electrolysis” National Renewable Energy Laboratory NREL/MP-560-35404 (2004) Steinberg M, Cheng M. C., “Modern and prospective technologies for hydrogen production from fossil fuels”, International Journal Hydrogen Energy 14 (1989) 797 – 820 Suleman F, Dincer I, Agelin-chaab M, “Development of an integrated renewable energy system for multigeneration” Energy (2014a) 1 – 9 Suleman F, Dincer I, Agelin-chaab M, “Energy and exergy analyses of an integrated solar heat pump sysem” Applied Thermal Engineering 73 (2014b) 557 – 564 Theodore W. H. “Hydrogen Production Using Geothermal Energy” Master’s thesis, Utah State University, (2008) U.S. Environmental Protection Agency and Science Applications International Corporation “LCAccess - LCA 101. 2001” (2004). http://www.epa.gov/ORD/NRMRL/lcaccess/lca101.htm . U.S. Annual Fuel consumption data available at LLNL, U.S. Department of Energy 2013) https://flowcharts.llnl.gov/ U.S. Energy Information administration “International Energy Outlook 2013” Office of energy analysis, U.S. Weiss M. A., Heywood J. B., Drake E. M., Schafer A., Au Yeung F. F.” On the road in 2020”, MIT EL 00-003, Energy Laboratory, Massachusetts Institute of Technology, Massachusetts (2000) 02139-4307

122

Wang Z. L., Naterer G. F., K S Gabriel, R Gravelsins, V N Daggupati “Comparison of sulfur–iodine and copper–chlorine thermochemical hydrogen production cycles” International Journal of Hydrogen Energy 35 (2010) 4820 – 4830 Wendt H, Imarisio G “Nine years of research and development on advanced water electrolysis. A review of the research programme of the Commission of the European Communities” Journal of Applied Electrochemical. 18 (1988) 1–14 Yildiz K, Hepbasli A, Dincer I “Life cycle assessment of hydrogen production from biomass gasification systems” International Journal of Hydrogen Energy 37 (2012) 14026 – 14039 Yilmaz C, Kanoglu M, Bolatturk A, Gadalla M “Economics of hydrogen production and liquefaction by geothermal energy” International Journal of Hydrogen Energy 37 (2012) 2058 – 2069 Zeng K, Zhang D “Recent progress in alkaline water electrolysis for hydrogen production and applications” Progress in Energy and Combustion Science 36 (2010) 307–326

123