comparative lca of electrolyzers for hydrogen gas production1331089/fulltext01.pdf · comparative...

DEGREE PROJECT IN ENVIRONMENTAL ENGINEERING, SECOND CYCLE, 30 CREDITS

STOCKHOLM, SWEDEN 2019

Comparative LCA of Electrolyzers for Hydrogen Gas Production

SUSANNE LUNDBERG

KTH ROYAL INSTITUTE OF TECHNOLOGY

SCHOOL OF ARCHITECTURE AND THE BUILT ENVIRONMENT

Comparative LCA of Electrolyzers for Hydrogen Gas Production

Jämförande LCA av elektrolyser för vätgasproduktion

Keywords: LCA, Energy, Hydrogen Gas, Electrolyzer

Degree project course: Strategies for sustainable development, Second Cycle AL250X, 30 credits

Author: Susanne Lundberg

Supervisor: Anna Björklund

Examiner: Anna Björklund

Department of Sustainable Development, Environmental Science and Engineering

School of Architecture and the Built Environment

KTH Royal Institute of Technology

ii

Acknowledgements

This master thesis from the Royal Institute of Technology (KTH) was conducted in collaboration

with IVL Swedish Environmental Research Institute. I want to thank many people for contributing

to this thesis. First, I want to thank my supervisors at IVL: Cecilia Johannesson and Tomas Rydberg

for the guidance and knowledge regarding LCA. I also want to thank Camilla Sundin for all great

discussions and guidance in the world of chemistry. Last, I want to thank my supervisor and

examiner from KTH Anna Björklund for great advices during the whole project.

iv

Abstract

The need for energy and fuels is predicted to grow within the next decades, in parallel to the need

of decreasing the emissions to air and water to operate within the planetary boundaries. The

alternatives to consider as energy or fuel options need to be environmentally friendly, evaluated

over the whole life cycle. Hydrogen is one of the considered alternatives because it contains no

carbon and has a good environmental performance when produced from renewable sources. It

can be produced by a variety of methods, where electrolyzers have a good potential

environmental impact if powered by renewable energy. Electrolyzers cleave water into hydrogen

and oxygen, by using electricity and water. There are currently four technologies on the market

or under development but there is a lack of LCA-studies that compare these.

This study is an attributional LCA-study, evaluating the potential environmental performance of

two electrolyzers: PEMEC and SOEC. The result from this study is thereafter compared to a parallel

study of one other electrolyzer: Alkaline. The LCA study considers six impact categories: Abiotic

Depletion (element), Abiotic Depletion (fossil), Acidification Potential, Eutrophication Potential,

Global Warming Potential and Photochemical Ozone Creation Potential. The system boundary is

set as cradle to gate. The electricity source for hydrogen production is evaluated in a sensitivity

analysis, together with a scenario of future estimated developments.

The electricity during hydrogen production has the highest impact of the life cycle for PEMEC and

SOEC, where the energy source has a great impact on the result. PEMEC has the lowest potential

environmental impact, in comparison to Alkaline and SOEC, which comes from low energy

consumption and low weight of materials with high environmental impact.

Keywords

Energy, Hydrogen Gas, LCA, Electrolyzer, SOEC, PEMEC, Alkaline

vi

Sammanfattning

Energi- och bränslebehovet förväntas öka inom de närmsta decennierna, samtidigt som utsläpp

till luft och vatten måste minska för att nå uppsatta klimatmål. De alternativ som tas fram behöver

vara miljövänliga, med bra klimatresultat sett över hela livscykeln. Vätgas är ett alternativ som

övervägs, på grund av högt energiinnehåll och låga utsläpp till följd av att den är fri från kol. Vätgas

kan produceras med en mängd metoder, där genom elektrolys anses vara en av de bästa

teknikerna ur miljösynpunkt. En elektrolysör producerar vät- och syrgas genom att sönderdela

vatten med hjälp av elektricitet. Det finns fyra elektrolys-varianter på marknaden och under

utveckling, men det saknas LCA-studier där dessa jämförs mot varandra.

Denna studie är en bokförings LCA av två elektrolyser: PEMEC och SOEC, som jämförs med

resultatet från en parallell studie av en annan elektrolys-typ: Alkalisk. Potentiell miljöpåverkan

mättes i sex stycken kategorier: resursutarmning (fossila resurser och ämnen), försurning,

övergödning, global uppvärmning och fotokemiskt marknära ozon. Systemgränsen är satt från

råmaterialutvinning till vätgasproduktion. Valet av elektricitetskälla för vätgasproduktion

utvärderas i en känslighetsanalys, tillsammans med påverkan av framtida teknikers konstruktion.

Livscykelfasen ”produktion av vätgas” har övervägande högst påverkan över livscykeln för SOEC

och PEMEC, där elektriciteten är den bidragande faktorn. Elektrolysmodellen PEMEC har

uppskattningsvis lägst miljömässig påverkan över livscykeln. Den låga påverkan för PEMEC kan

härledas till låg elektricitetsförbrukning under vätgasproduktionen samt låga vikter av material

med hög miljömässig påverkan.

Nyckelord

Energi, Vätgas, LCA, Elektrolysör, SOEC, PEMEC, Alkalisk

viii

Nomenclature

AD – Abiotic Depletion

AP – Acidification Potential

BOP – Balance of Plant

CML – Institute of Environmental Sciences

CO2 – Carbon Dioxide

FU – Functional Unit

GWP – Global Warming Potential

HTE- High Temperature Electrolysis

LCA – Life Cycle Assessment

LCI – Life Cycle Inventory

LCIA - Life Cycle Impact Assessment

LTE - Low Temperature Electrolysis R&D – Research and Development

SOEC – Solid Oxide Electrolysis Cell

PEMEC - Proton Exchange Membrane Electrolysis Cell

POCP - Photochemical ozone creation potential

Materials

BCZY- yttriadoped barium cerate-zirconate

CBC- Ceria- based composites

GDC-Gadolinia-doped CeO2 or also known as cerium-gadolinium oxide, CGO)

LSCF-lanthanum strontium cobalt ferrite

LSCo-lanthanum strontium cobalt oxide

LSGM- lanthanum strontium gadolinium manganite

LSM- lanthanum strontium manganese

PrNi-praseodymium nickel

SDC-samaria-doped ceria

YDC- yttriadoped ceria

YSZ- yttriastabilized zirconium

YSZ-SDC- cermet composite

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Table of Content

Acknowledgements ................................................................................................................................................................... ii

Abstract .......................................................................................................................................................................................... iv

Sammanfattning ......................................................................................................................................................................... vi

Nomenclature ........................................................................................................................................................................... viii

Introduction .................................................................................................................................................................................. 1

1.1 Problem definition................................................................................................................................................. 3

2 Aim and Objectives .......................................................................................................................................................... 4

3 Research Design and Methodology ......................................................................................................................... 5

3.1 Research Design...................................................................................................................................................... 5

3.2 Life Cycle Assessment .......................................................................................................................................... 6

4 Background ...................................................................................................................................................................... 11

4.1 Hydrogen ................................................................................................................................................................. 11

4.2 Electrolyzers .......................................................................................................................................................... 12

4.2.1 Proton Exchange Membrane Electrolyzer Cell .......................................................................... 14

4.2.2 Solid Oxide Electrolysis Cells .............................................................................................................. 15

4.2.3 Alkaline .......................................................................................................................................................... 16

4.3 Literature Review of previous LCA studies on Electrolysis and Electrolyzers ................... 17

5 LCA of two Electrolyzers ........................................................................................................................................... 18

5.1 Goal and Scope of the LCA .............................................................................................................................. 18

5.1.1 Functional Unit ........................................................................................................................................... 18

5.1.2 System Boundaries .................................................................................................................................. 19

5.1.3 Allocation Procedures ............................................................................................................................ 20

5.1.4 Life Cycle Inventory Modelling Framework ............................................................................... 21

5.1.5 Data Quality ................................................................................................................................................. 22

5.1.6 Sensitivity Analysis .................................................................................................................................. 22

5.1.7 Assumptions and Cut-offs .................................................................................................................... 24

5.2 Life Cycle Inventory ........................................................................................................................................... 25

5.2.1 Data Collection Strategy ........................................................................................................................ 26

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5.2.2 Life Cycle Inventory of PEMEC........................................................................................................... 26

5.2.3 Life Cycle Inventory of SOEC ............................................................................................................... 28

5.2.4 Life Cycle Inventory of Transports .................................................................................................. 30

5.3 Life Cycle Impact Assessment....................................................................................................................... 30

5.3.1 Result .............................................................................................................................................................. 31

5.3.2 Sensitivity Analysis .................................................................................................................................. 34

6 Life Cycle Interpretation ........................................................................................................................................... 39

6.1 Limitations of Results ....................................................................................................................................... 39

6.2 Conclusion .............................................................................................................................................................. 40

7 Recommendations and Reflections ..................................................................................................................... 42

7.1 Recommendations for Future Studies...................................................................................................... 42

7.2 Reflections of the Electrolyzer comparison .......................................................................................... 42

7.3 Material Supply .................................................................................................................................................... 43

8 References......................................................................................................................................................................... 45

Appendix 1 - Material choices differences from the original material in the electrolyzer design 49

Appendix 2 – Calculation input of material and electricity to be modelled in relation to the FU . 51

Appendix 3 – Material inputs for the sensitivity analysis .................................................................................. 55

Appendix 4 - Data sets .......................................................................................................................................................... 57

Appendix 5 - Data set Sensitivity Analysis ................................................................................................................. 61

Appendix 6 – The results presented in numbers for PEMEC, SOEC and Alkaline ................................. 62

Appendix 7 – A comparison of the life cycle phases between SOEC and PEMEC ................................... 63

Appendix 8 – Sensitivity analysis, results of changed electricity mix .......................................................... 70

Appendix 9 - Result from Estimated Future Design, presented by category ........................................... 75

Appendix 10 – Comparison of the materials in the SOEC-design,.................................................................. 78

Appendix 11 – Comparison of the materials in PEMEC´s design.................................................................... 81

1

Introduction

Global energy demand is predicted to grow within the next decades (Romagnoli, et al., 2011) and

sustainable energy supply is a key factor to minimize the environmental damage and live within

the planetary boundaries (Rockström & Klum, 2012). The demands for environmentally friendly

energy supplies emanates from the declining of fossil energy resources in addition to climate

change, and environmental pollution. The alternative energy sources need to fulfill criteria such

as suitability for both stationary and mobile applications, no/minimal emissions of carbon dioxide

(CO2) and affordable price (Romagnoli, et al., 2011). Hydrogen can meet these demands and has

other advantages such as high energy content and ability to store and transport energy. In

addition, it can be created from renewable resources and creates no emissions of nitrogen oxides

(NOx) or sulfur oxides (SOx) during combustion. The industrial sector is currently the largest user

of hydrogen applications, but the usage is expected to grow within the transport sector too

(Bhandari, et al., 2013).

Hydrogen can be produced from both renewable and non-renewable energy sources and by a

variety of processes (Bareiß, et al., 2019). Examples of renewable ways to produce hydrogen are

for example by water splitting, such as electrolyzers, if powered by renewable energy and

examples of non-renewable hydrogen production processes are e.g. reforming or gasification of

natural gas, see Figure 1.

Figure 1. Examples of hydrogen production technologies. Steam reforming, catalytic reforming, partial oxidation and gasification are production methods for reforming of fossil resources (Lozanovski, et al., 2011), while water splitting, and biomass derived fuels are counted as renewable production technologies (Godula-Jopek, 2015). More information can be found in chapter 5.1.

There are more processes for producing hydrogen from fossil fuels, than derived from renewable

sources. Today, most hydrogen is produced from fossil resources, see Figure 2, where reforming

of fossil fuels is the dominant production process due to the low economic cost, and that the

Renewable Resources and Production Technologies

Watersplitting (if powered by renewable sources)

Fermation of biomass

Non-renewable Resources and Production Technologies

Steam reforming of natural gas

Catalytic reforming of hydrocarbon

Partial oxidation of natural gas

Watersplitting (if powered by non-renewable sources)

2

technology is well-established. The low cost is correlated with the availability and low cost of the

fossil resources feedstock (Godula-Jopek, 2015, p. 13).

Figure 2. The breakdown of the total hydrogen gas production globally. Most of the global hydrogen production derives from fossil resources (Bareiß, et al., 2019), and only 4% comes from water splitting using electrolyzers (Lozanovski, et al., 2011).

From an environmental perspective, producing hydrogen through natural gas is not sustainable

and other options need to be considered. Therefore, a preferred option for the future is to use

electrolyzers, which produce hydrogen through cleaving water into hydrogen gas and oxygen

(Zhang, 2018; Godula-Jopek, 2015). The electrolyzers produce the best environmental result if

powered by renewable energy sources. Production of hydrogen gas through electrolyzers have

many advantages, such as the low emissions occurring during the production of hydrogen, plus

the resources required for production are only water and electricity (Fischer, et al., 2016; Chi &

Hongmei, 2018). By using renewable energy sources, electrolyzers have better environmental

impact than reforming of fossil fuels. As seen in Figure 2, today's share of hydrogen production by

electrolyzers is still limited globally and only consists of approximately 4% (Bhandari, et al., 2013;

Bareiß, et al., 2019), but is expected to grow in the future when the fossil energy sources need to

be exchanged (Godula-Jopek, 2015). However, a few electrolyzer technologies are available on the

commercial market and some are under development, but none of them are free from

environmental burdens. Therefore, conducting a life cycle assessment (LCA) is beneficial for

quantifying the environmental burdens and visualize hotspots for electrolyzers’ life cycle

(Bhandari, et al., 2013).

This study, plus the results from a parallel study by Sundin (2019), includes three electrolyzers.

Two technologies are currently on the commercial market, while one is still under development.

Natural Gas

Liquid Hydrocarbons

Coal

Electrolysis

Natural Gas Liquid Hydrocarbons Coal Electrolysis

3

These three electrolyzers constitute the main technologies that currently exist, of which this study

will consider PEMEC (Proton Exchange Membrane Electrolysis Cell) and SOEC (Solid Oxide

Electrolysis Cells). PEMEC is implemented in industries, while SOEC is still in the research and

development (R&D) phase (Godula-Jopek, 2015). The parallel study considers Alkaline, which is

currently the most commonly used technology and implemented in industries (Guillet & Millet,

2015).

1.1 Problem definition

Industries need to decrease their environmental footprint for achieving a society that can operate

within the planetary boundaries (Rockström & Klum, 2012). This can be approached in multiple

ways, where focusing on changing energy carriers or fuels can be two alternatives. Hydrogen is

good from an environmental perspective, since it does not contribute to global warming, due to

insignificant carbon dioxide emissions (Romagnoli, et al., 2011). Furthermore, producing

hydrogen gas can be conducted with a variety of methods, where electrolyzers are considered the

most environmentally friendly option, (Giraldi, et al., 2015; Zhao & Schrøder Pedersen, 2018).

Therefore, the amount of electrolyzers (Zhang, 2018; Godula-Jopek, 2015), and more research on

new models is conducted for achieving a more energy efficient hydrogen production. Even though

the environmental result from electrolyzers are better than other technologies, none of these

electrolyzers are free from environmental burdens. By using Life Cycle Assessment (LCA), the

environmental assessment can be comprehensive and decreases the (Bhandari, et al., 2013).

4

2 Aim and Objectives

The aim of this master thesis is to evaluate the environmental impact of two electrolyzers: PEMEC

and SOEC, during the life cycle. In addition to evaluating the environmental impacts, the study

aims to find hotspots and to give a recommendation on what needs to be further investigated to

achieve more comprehensive future studies. This was achieved by calculating the result from an

LCA and evaluating the result in six environmental impact categories see Table 2 and the chapter

“Goal and Scope of the LCA”. The final step of this study is to evaluate which electrolyzer generates

the lowest environmental impact. The result from the SOEC and PEMEC was compared with one

other electrolyzer: Alkaline, from a parallel master thesis study of Sundin (2019).

The result of the study might be considered important for an audience interested in

understanding potential environmental impacts of the life cycle by different types of electrolyzers.

The study does not consider a specific company or application, which make it a good basis for a

general impression of the impacts. Therefore, the result might be a basis for future, more detailed,

studies.

To reach the aim of the study following research questions will be answered:

1. Which of the four electrolyzers has the best potential environmental performance? 2. Which are the environmental hotspots? 3. How does the energy source during hydrogen production impact the result for SOEC and

PEMEC? 4. What is the potential environmental impact for the future estimated development for

SOEC and PEMEC, compared to current technology? 5. What are the current data gaps and information needed for conducting a more

comprehensive LCA for future studies?

5

3 Research Design and Methodology

This chapter is divided in three parts. First, the research design is defined, followed by a description

of the LCA-methodology, and finally an explanation of the data collection strategy.

3.1 Research Design

The aim of the master thesis is to evaluate the environmental impact of four electrolyzer

technologies during the life cycle, to find hotspots and finally to give a recommendation on what

needs to be further investigated to achieve more comprehensive future studies. This was achieved

by creating an attributional LCA of two electrolyzers: SOEC and PEMEC, then comparing the

results to a parallel study by Sundin (2019) of one other electrolyzers: Alkaline. The methodology

for this study is visualized in Figure 3 and consists of three main parts. First, an LCA was carried

out according to standard ISO14040 (ISO 14040, 2006), ISO 14044 (ISO 14044, 2018). In addition

to the ISO standards, a guidance document for LCA studies on Fuel Cells and H2 Technologies was

used (Lozanovski, et al., 2011). Gabi1 was used as software, where Ecoinvent 3 (Wernet, et al.,

2016) and Thinkstep (Thinkstep AG, 2018) was used as databases for the LCA-models. The data

and information needed were collected through similar studies in peer-reviewed articles.

Assumptions were made, where data gaps occurred. The result from this study was compared

with the result from a parallel master thesis study, to answer the five research questions.

Figure 3. The procedure of the master thesis is divided into three part; LCA of two electrolyzers, comparison to the parallel master thesis study and answering the research questions.

1 Gabi is a software for conducting LCA-studies.

6

3.2 Life Cycle Assessment

LCA calculates and evaluates the environmental impact of a product or service during its life cycle,

from a system perspective (ISO 14040, 2006). The life cycle model should ideally include every

stage from the extraction of raw material, transport, manufacturing, use, and end of life treatment,

see Figure 4. An LCA quantifies natural resources and polluting emissions. Therefore, the products

or services results can be compared on an equal and transparent basis (Baumann & Tillman, 2004,

pp. 19-22; Curran, 2015). An LCA can be used for several purposes, where some suggestions from

the ISO standards are:

o Decision making, within industries, organizations or governmental organizations. Example for conducting strategic planning, make priorities, and design or redesign a process.

o Identifying opportunities for improvements on a product or service, throughout its life cycle. o Measurement tool for marketing, such as environmental product declaration. o Learning or exploration purposes.

Figure 4. The life cycle assessment evaluates the impacts of all or some stages of a product or service life cycle. The arrows represent the transports in this figure, and to illustrate a cylindric process.

There are many advantages of conducting and using the result from an LCA. First, it is a powerful

tool for structuring complex environmental problems. By using LCA, environmental damages can

be compared among products and services. This would ideally lead to more aspects being

considered when taking a decision among consumers and organizations before purchasing a

certain product or service. In other words, if a consumer receives quantitative information

regarding the environmental impact caused by a product or service, the decisionmaker might

invest in other products with an attractive environmental result. Ideally this would be start to a

positive loop where less environmental damage is caused (Curran, 2015). Secondly, since the LCA

is focusing on the whole product system, it enables avoiding sub-optimization which can occur if

only considering a few processes (Baumann & Tillman, 2004, p. 21). The method, therefore,

ensures that important categories are considered in the environmental evaluation.

Resources

Processing

ManufacturingDistribution

Use

End of Life

7

The drawbacks of using the result from an LCA study are based on the complexity of

environmental issues, and the difficulties in modeling in enough level of detail. It is difficult to

quantify these environmental issues with good quality, plus communicate data and assumptions

transparently. Assumptions may provide an angled version of the real result and the robustness

of the result should be tested in sensitivity analysis. Generally, social and economic aspects are

not included in LCA, but need to be analyzed on the side. This can be conducted by doing a Social

Life Cycle Analysis (SLCA) or Life Cycle Costing (LCC) for monetary values (Baumann & Tillman,

2004, p. 21). Moreover, the result from an LCA can be difficult to interpret due to the large amount

of data required, which need to be divided and simplified into a few categories. This simplification

might lead to uncertainties in the parameters, due to potential double counting or give a

misunderstood result (Baumann & Tillman, 2004, p. 133). These factors might limit the chances

of receiving a transparent and correct interpretation of the reality (Canis, et al., 2010; Boufateh,

et al., 2011). In addition, the emissions are grouped into impact categories and the practitioner

need to choose with to consider in the study. The choice of categories is based on values where it

can be difficult to prioritize which impact categories to evaluate the environmental or human

potential impact, due to all categories are important (Curran, 2015; Hellweg & Milá in Canals,

2014).

Attributional and Consequential LCA

An LCA study can be conducted in different ways depending on what being studied or the purpose

of the study. Generally, there are two types of LCA-studies; consequential or attributional. An

attributional LCA is describing a system as it can be observed; historical, currently or in the future,

where the consequential describes consequences of a change. A consequence of a change can be

to choose product A instead of B. In addition, an attributional LCA calculates the potential

environmental impact of a service or product and the system boundaries plus data used are

describing the system as it currently is. The potential environmental impact is describing the

average environmental burden from total production volume, where a consequential is describing

marginal data (the change of environmental burdens when the production volume changes)

(Camillis, et al., 2013).

Standards for LCA

European Committee for Standardization published the first guidelines for creating LCA in 1997

(Curran, 2015, p. 12). The standards are continuously improving and are currently described in

two documents. ISO 14040 containing the main principles and framework for reporting and

auditing, while ISO 14044 is including the demands for conducting an LCA, recommendations and

background to the environmental impacts (ISO 14040, 2006; ISO 14044, 2018).

8

According to ISO 14040, an LCA study consist of four phases: goal and scope definition, the

inventory analysis, the impact assessment phase and the interpretation phase. This method if

further explained in Figure 5.

Figure 5. The life cycle assessment framework according to the ISO14040 standard. The arrows are representing the relationships between the phases of the LCA.

The ISO14040 has requirements of what the phases shall include to fulfill its purposes. The LCA is

furthermore required to transparently explain its system boundary, and level of detail. ISO has

defined the system boundaries as a “set of criteria which unit processes are part of a product

system” (ISO 14040, 2006).

Goal and Scope Definition

The first step of an LCA is to describe the goal and scope of the study. The goal and scope can be

adjusted during the study, in relation to the other phases. However, six aspects must be described

in this section:

1. The function of the system

2. The functional unit

3. The system boundaries

4. Allocation procedures

5. Impact assessment methodology and interpretation

6. Data needs

The first phase is to study and define the function of the system/s. The second step is deciding the

functional unit (FU) to use as a basis for the study. FU shall be a reference to which the input and

output flow are related (Curran, 2015, pp. 20-24). FU can state the function provided, the quantity,

how long and to what quality (Wolf, et al., 2012). Thirdly, the system boundaries need to be

defined and show the parts in the scope such as the flows and components, preferably visualized

by a flow diagram. The goal and scope shall also include the selection of impact categories and

9

how to treat uncertainties. Moreover, the fourth aspect of the goal and scope definition defining

how to handle allocation problems arising within the study. An allocation is when a process is

including serval useful outputs. The ISO standard has recommendations for how to handle

allocations to fairly divide the environmental burdens per product. Lastly, the practitioner shall

state the impact assessment methodology and the data needs for conducting the study (Curran,

2015, pp. 28-30). The data needed to meet the goal and scope of the LCA-study need to be specified

(ISO 14040, 2006). The requirements for the quality of the data plus the geographical and

technological coverage need to be explained to ensure the transparency of the study.

Life Cycle Inventory

The second phase of the LCA is the Life Cycle Inventory (LCI). LCI includes data collection and

guidelines of how to calculate the relevant in- and outflows of a process system. The data

collection can include headings as energy flows, raw material flows, products, emissions to air or

water etc. The quality of the data needs to be considered and the data related to the functional

unit reference flows. Moreover, the LCI shall consider if allocation occur within the process (ISO

14040, 2006; ISO 14044, 2018).

Life Cycle Impact Assessment

The Life Cycle Impact Assessment (LCIA)-phase is translating the inventory results (resources and

emissions) into environmental impacts (Baumann & Tillman, 2004, p. 172). The inventory data is

connected classified and thereafter characterized to the impact categories, which simplifies the

understanding of the impact. This information will be interpreted in the final phase. According to

the ISO 14040, the LCIA-phase is requiring two core subphases and two optional. The two core

subphases are classification, and characterization. Classification is to connect each emission to the

respective impact categories. The characterization is to calculate the potential environmental

impact per category (Baumann & Tillman, 2004, pp. 134-135). The optional elements are

normalization and weighting, where normalization is “calculation the magnitude of category

indicators relative to reference information” (ISO 14040, 2006). For example, by comparing the

result relative the yearly impacts of e.g. a country (Curran, 2015, p. 208) from all categories

relative to CO2 equivalents. Weighting is when taking the results from the impact categories and

applying a weighting factor (based on value judgements) to see the relative importance of the

impact category (Curran, 2015).

LCIA methods comprise a recommended group of impact categories, indicators and

characterization factors. Impact categories includes resources, impacts on human or the

environments health (Baumann & Tillman, 2004, pp. 137-139). Several LCIA methods are

available, such as “ReCiPe” (Mark, et al., 2017), the Institute of Environmental Science (CML)

10

(Guinée, et al., 2002), or “TRACI” (Bare, 2001). ISO does not specify any recommendation of these.

Thus, the choice of impact category is depending on what is being studied (Curran, 2015, p. 143)

Interpretation of the result

The fourth and final phase on an LCA according to ISO14040 is interpretation of the result. Here,

both result from the inventory analysis and the impact assessment are considered. The result shall

be in correlation with the goal and scope, to reach relevant conclusions, explain the limitations

and finally, providing recommendations. The result shall be presented transparently, and weak

point in terms of assumptions or rationales, shall be documented (ISO 14040, 2006).

11

4 Background

This chapter introduces hydrogen as a fuel and energy carrier. The chapter explains common

methods to produce hydrogen and describe the electrolyzers technologies in more depth. Thereafter,

different electrolyzer technologies are described. This project includes three different electrolyzers.

PEMEC and SOEC will be described, while Alkaline will be shortly introduced and further described

in the other report and referenced to as (Sundin, 2019).

4.1 Hydrogen

Hydrogen is a gaseous element at standard pressure and temperature. The gas does not smell, is

transparent, flammable, and contains much energy. Due to the high energy content, it can be used

as a fuel in vehicles or to store energy. It can be stored in a gaseous, liquid or solid state (Godula-

Jopek, 2015, p. 323). Hydrogen has been used through the last 100 years in several different

applications and is considered as an important energy carrier for future applications (Fischer, et

al., 2016), since fossil fuels need to be exchanged to sustainable alternatives. Hydrogen has many

positive characteristics such as high energy content and low environmental footprint since

hydrogen is transformed into water during combustion (Chi & Yu, 2018). In addition, hydrogen

can be used as one step towards more environmentally friendly industries, for example, as a

reducing agent instead of coal in the steel industry. On the other hand, hydrogen is flammable and

need to be handled safety (Acar & Dincer, 2018).

The environmental impact from hydrogen gas, seen from a life cycle perspective, can vary much

depending on which production method is used. In addition, the energy source for the production

process has a big impact of the overall environmental performance of the hydrogen. Hydrogen

produced through electrolysis and powered by renewable energy has better performance than if

the energy is sourced from fossil fuels. For example, using coal as an energy source to the

electrolyzer will lead to higher potential environmental impact compared to use renewable

energy sources (Ghandehariun & Kumar, 2016). Hydrogen can be created from both fossil fuels

and renewable energy sources (Acar & Dincer, 2018). There are generally four different methods

available. Natural gas through steam reforming is the most common way and stands for

approximately half of the global production (Guillet & Millet, 2015). Furthermore, hydrogen can

be produced from processing oil, coal gasification (Giraldi, et al., 2015), reforming hydrocarbon

or by biological process of biomass. It is carried out by microorganisms, like bacteria or algae who

produce hydrogen through biological processes (Godula-Jopek, 2015, p. 17).

Hydrogen gas is expected to have a promising future as a fuel for mitigation climate change

(Thomas, 2017). On the other hand, there are challenges with the technology for creating a good

transition from previous energy sources to hydrogen in a larger scale. First, the infrastructure

12

distribution needs to be further developed and implemented to use the gas as a fuel in a greater

extent (Fischer, et al., 2016; Acar & Dincer, 2018). Finally, the size of the fuel tank, in a vehicle,

needs to be enough for being comparative to other alternatives. Otherwise, the consumer would

need to refuel more often compared to other alternatives (Giraldi, et al., 2015).

4.2 Electrolyzers

Electrolyzers is a technology which splits water into hydrogen and oxygen using electricity. It

classifies as one of the best ways to produce hydrogen, due to the high efficiency and the low

energy needed (Godula-Jopek, 2015; Bareiß, et al., 2019). Even though it is categorized as a good

way to produce hydrogen, only 4% of the global production is made by electrolysis in 2010

(Guillet & Millet, 2015). However, the technology is considered especially for the steel industry,

due to the good environmental performance (Weigel, et al., 2016). The electrolysis of water can

either be done at low temperature using liquid water or at high temperature using steam (Godula-

Jopek, 2015, p. 191). The categories for low-temperature electrolyzers are Proton Exchange

Membrane Electrolyzer Cell (PEMEC) and Alkaline. High-Temperature Electrolyzers (HTE) is

divided into two techniques: Solid Oxide Electrolysis Cell (SOEC) and Molten Carbon Electrolysis

Cell (MCEC) (Giraldi, et al., 2015). The construction of an electrolyzer is described in Figure 6.

Figure 6. Inspired by Acar & Dincer (2018) the basic construction of an electrolysis. The box colored blue is representing the electrolyte, and the orange is representing the membrane.

An electrolyzer can simplified be described as an anode and a cathode with a membrane in the

middle, see Figure 6. A catalyst is often included in the electrodes and the general function is to

aid a chemical reaction to occur. Electricity is supplying the cell with negative charged electrons.

Water is entering at the anode and is separated through the membrane. 1

2O2 is collected at the

anode side, and H2 at the cathode side. This can be visualized through following chemical reaction

(Godula-Jopek, 2015, p. 33):

13

Full Reaction: 𝐻2𝑂(𝑙) → 𝐻2(𝑔) +1

2𝑂2(𝑔)

Anode: 𝐻2𝑂(𝑙) → 1

2 𝑂2(𝑔) + 2𝐻+ + 2𝑒−

Cathode: 2𝐻+ + 2𝑒− → 𝐻2(𝑔)

The characteristics of the electrolyzers are explained in Table 1. More information is available for

the Low Temperature Electrolyzers (LTE) than HTE, since it is more commercialized.

Table 1. A comparison among technical specifications. Information regarding Alkaline, PEMEC, and SOEC is gathered from Bhandari, et al., (2013) and (Godula-Jopek, 2015). Empty boxes mean data is not found.

Specification Alkaline (LTE) PEMEC (LTE) SOEC (HTE) Technology maturity Commercially

Mature2 Demonstration2 R&D2

System Lifetime (years)

20-302 10-202

System Lifetime (hours)

60000-900003 20000-600003 100003

Production Capacity (m3/h)

7603 403 403

Cell temperature (˚C) 60-802 50-802 900-10002

Hydrogen Purity (%) >99.53 99.9993 99.93

Cold start-up time, (min)

152 <152 >602

Quick start and stop cycling

Weak4 Good4 Weak4

Cost (€kW-1) 1000-12003 1860-23203 >20003

Cell area (m2) <43 <0.33 <0.013

2 (Bhandari, et al., 2013 3 (Schmidt, et al., 2017) 4 (Godula-Jopek, 2015)

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4.2.1 Proton Exchange Membrane Electrolyzer Cell

PEMEC was introduced at the beginning of 1950 (Godula-Jopek, 2015, p. 64). It is a low-

temperature technique (Breeze, 2017), which operates with a pressure up to 15 bar and a

temperature around 80ºC (Bhandari, et al., 2013). It has a lifetime of 10-20 years or 20 000–

60 000 hours (Schmidt, et al., 2017; Acar & Dincer, 2018). PEMEC is still in the demonstration

phase but is predicted to be used in a larger extent, on the commercial market, due to the great

hydrogen purity of 99.999% (Acar & Dincer, 2018; Ursua, et al., 2012) and the market is searching

for more flexible water electrolysis in terms of easy start and stop (Godula-Jopek, 2015, p. 389).

Moreover, the design of the PEMEC is expected to dramatically change within the near future. For

example, the stack lifetime will increase, and the membrane thickness will decrease (Bareiß, et al.,

2019).

In a PEMEC electrolysis, the electrolyte is not required to be liquid (Ursua, et al., 2012), and is

commonly a polymer, due to the high proton conductivity in addition to good mechanical and

chemical stability. The membrane is thin, approximately 50–250 µm, and conducts protons used

as a solid electrolyte (Godula-Jopek, 2015, pp. 63-65). The membrane has a low pH-level (Breeze,

2017). The most commonly used membrane is Nafion (Ursua, et al., 2012). The electrodes are

Nobel metal-based such as Platinum or Iridium (Bhandari, et al., 2013). The construction and the

reaction in a PEMEC are visualized in Figure 7.

Figure 7. The reaction taking place in the PEMEC, inspired by (Schmidt, et al., 2017)

According to (Bhandari, et al., 2013), the following reaction happens in a PEMEC cell:

Anode: 𝐻2𝑂 → 1

2 𝑂2 + 2𝐻+2𝑒−

Cathode: 2𝐻+ + 2𝑒− → 𝐻2

Advantages and Disadvantages

PEMEC is highly efficient and is flexible to run, because of the easy start and stop cycling. The time

to start up the electrolyzer is a large difference compared to HTE (which need time to heat up the

15

water) (Godula-Jopek, 2015, pp. 64-65). The easy start and stop are especially in favor of the

commercialization for PEMEC since the market is searching flexible electrolysis (Godula-Jopek,

2015, p. 389). Secondly, it is small by size, which simplifies transports. However, PEMEC has

historically not been the first-hand choice and therefore lack industrial majority (Godula-Jopek,

2015, pp. 64-65). This is due to disadvantages such as the limited lifetime (Smolinka, et al., 2011;

Bhandari, et al., 2013), the high investment cost (Grigoriev, et al., 2006) and the great sensitivity

towards impurities in the water (Acar & Dincer, 2018). Moreover, most of the PEMEC electrolysis

are commercially available for low scale production applications (Bhandari, et al., 2013).

PEMEC is more expensive then Alkaline, due to the high price for the membrane and the Nobel

metal-based electrodes such as platinum or iridium (Bhandari, et al., 2013). The production of

PEMEC must increase for further spread of the technology (Grigoriev, et al., 2006).According to a

study by (Schmidt, et al., 2017), many experts believe the preferred technology for electrolyzers

will shift from Alkaline to PEMEC between 2020 and 2030. The capital cost for PEMEC will be

reduced until 2020. Even further, at 2030 the price is expected to significantly decrease and

therefore together with the operational flexibility, the technology is predicted to be more

attractive than Alkaline.

4.2.2 Solid Oxide Electrolysis Cells

Solid Oxide Electrolysis Cell (SOEC) converts water to hydrogen and oxide, using solid oxide. The

technology is still in R&D phase (Acar & Dincer, 2018). The construction (materials and

components) of SOEC is similar a Solid Oxide Fuel Cell (SOFC), but the function is the opposite

(Godula-Jopek, 2015, p. 193). The reaction in a SOEC can be seen in Figure 8. SOEC is a high

temperature electrolysis which operates at temperatures of approximately 650-800°C but was

initially 800-1000°C (Godula-Jopek, 2015, p. 390). SOEC is estimated to have the shortest expected

lifetime, compared to Alkaline and PEMEC, less than 10 000 hours (Schmidt, et al., 2017).

Figure 8. Visualizing the reaction in a SOEC inspired by figure 6.2 in Godula-Jopek (2015, p. 192)

SOEC is constructed with three ceramic layers: two porous electrodes placed on both sides of the

electrolyte. The electrolyte is solid and consists of ceramics (Godula-Jopek, 2015, p. 390) or most

16

commonly zirconia. The electrodes are made by nickel or zirconia and is 50 µm thick. SOEC is a

relatively new technique and due to the technical development, the materials within SOEC is

continuously changing to raising the performance of HTE operations. The reactions at the anode

and cathode are following (Godula-Jopek, 2015, pp. 191-195):

Cathode: 𝐻2 𝑂 + 2𝑒− → 𝐻2 + 𝑂2−

Anode: 2𝑂2− → 𝑂2 + 4𝑒−

Advantage and Disadvantage

The main advantage of SOEC is generally less energy during the hydrogen gas production process,

compared to using LTE because a part of the electricity needed to split the water molecule is

replaced by heat. Therefore, SOEC is especially interesting when there is waste heat from

machines or activities around the electrolyzer (Acar & Dincer, 2018). It can contribute to lower

running cost, due to that heat sources are often available to lower prices. Other advantages with

the SOEC, compared to low-temperature electrolysis, are higher efficiency (Godula-Jopek, 2015,

p. 191; Acar & Dincer, 2018), lower material costs and the possibility to run the technology the

opposite way, as a fuel cell, or in co-electrolysis mode to produce syngas (H2+CO) from water

steam. The disadvantages with the SOEC is great material degradation, which is a result of the high

operating temperature. Therefore, the aim of the R&D is to stabilize the existing component

materials and testing new materials with better stability. Moreover, increased lifetime can also be

achieved by running the technology with lower operating temperatures. Prototypes are tested to

decrease the temperature from 650-1000ºC to 500-700ºC. The SOEC is still on a prototype scale,

with some companies aiming for a larger spread of the technology (Schmidt, et al., 2017).

4.2.3 Alkaline

Alkaline is the most commercially used technology and have been used in commercial purposes

since the early 1900s. Alkaline is a low-temperature technique, which operates at a temperature

of 40-90ºC. It has a long lifetime of 20-30 years, or 60 000-100 000 hours. Alkaline produces

hydrogen with high purity, above 99.8%. The materials within Alkaline electrolysis can vary

depending on model and purpose. The most commonly used electrolyte is sodium hydroxide or

potassium hydroxide. Commonly used electrode materials are Raney nickel together with Sulphur

addition or steel coated with nickel. The membrane is often polyphenylene sulfide (Ryton),

polysulfone bonded (Zirfon) or anion-selective polymers (Sundin, 2019). The conversion from

water to hydrogen and oxygen in a basic Alkaline electrolysis occur by following reactions:

Anode: 2𝑂𝐻− → 1

2𝑂2(𝑔) + 𝐻2𝑂 + 2𝑒−

Cathode: 2𝐻2𝑂(𝑙) + 2𝑒− → 𝐻2(𝑔) + 2𝑂𝐻−

17

Advantages and Disadvantages

Alkaline has been used for large-scale industrial applications since 1920 (Schmidt, et al., 2017;

Godula-Jopek, 2015, p. 387). Therefore, the technology is already implemented and available, and

to a relatively low cost. The low cost emanates from the material cost (Schmidt, et al., 2017;

Godula-Jopek, 2015, p. 191), capital and energy expenses (Godula-Jopek, 2015, p. 387). The

disadvantage of the technology is the slightly lower lifetime and less efficiency (Schmidt, et al.,

2017).

4.3 Literature Review of previous LCA studies on Electrolysis and Electrolyzers

Several standalone LCAs have been conducted for evaluating electrolysis environmental impact,

but the literature lacks an LCA comparing the different techniques. The LCAs regarding

electrolysis are limited to focus on one independent technology. Such as the example from Giraldi,

et al., (2015), who analyzed a single high-temperature electrolysis, running on nuclear power

supply and the study conducted by Häfele, et al., (2016), that aimed to study the highest

environmental burden of SOEC. The conclusions from both these studies displayed that the

highest environmental burden was caused by the electrolysis cell itself and the hydrogen

production. Another trend in the LCA´s is to evaluate the impact from the energy supplies, such as

focusing on nuclear power plant (Giraldi, et al., 2015), wind turbines and natural gas (Zhao &

Schrøder Pedersen, 2018) or Ghandehariun & Kumar (2016) who evaluate different energy

sources. The results showed that the best environmental performance was given when the

electricity emanates from renewable energy supplies. However, Schmidt, et al., (2017) gathered

information from experts regarding the SOEC, Alkaline, and PEMEC. This study is not an LCA but

evaluates important aspects to consider in a decision situation, such as the lifetime differences or

the component materials. Moreover, Bhandari, et al., (2013) evaluated different hydrogen gas

production techniques like electrolysis. The study highlights that previous LCA studies have

reviewed electrolysis as a black box. In other words, no evaluation has considered individual

components in the machine, such as the membrane, electrolyte or electrodes. The study especially

highlights the benefit of conducting LCA studies that compare different electrolysis technologies

where the individual components also are considered. However, it does exist a gap of studies on

LCA comparing different electrolysis technologies, which use the same functional unit and power

supply. Therefore, this master thesis study is especially interesting to add to previous knowledge

of LCA on a single electrolysis type.

18

5 LCA of two Electrolyzers

This chapter is divided in the four phases of an LCA-study. First, the goal and scope of the study is

explained. Thereafter, the inventory analysis is presented, including the data found for both

technologies. The third sub-chapter is the LCIA were the result of the study is visualized. The final

chapter includes the interpretation of the result, shown in the chapter of LCIA.

5.1 Goal and Scope of the LCA

The aim of the study was to evaluate and compare the potential environmental impacts of two

electrolyzers: PEMEC and SOEC, from a life cycle perspective. Thereafter, the result from the study

was compared with one other electrolyzers: Alkaline, evaluated in another study. The result

identified the hotspots in terms of environmental impact category and life cycle phase. In addition,

to give recommendations on what need to be further investigated in future studies. The system

boundary is cradle to gate, excluding the use of the hydrogen gas and the waste handling.

The intended audience

The intended audience for this study is non-technical and external audience, who are interested

in evaluating and comparing the potential environmental impacts in these four electrolyzers. This

interest might derive from an aim to creating own LCA-studies or be a basis for future research

on electrolyzers to receive more understanding on the potential environmental impacts during

the life cycle. The presented result in this study is not brand specific and might therefore be used

as a general purpose.

5.1.1 Functional Unit

The function of an electrolyzer is to produce hydrogen (and possible oxygen if considered as a by-

product, and not an emission). The functional unit is set to 100 kg produced hydrogen gas. This

amount was chosen for three reasons. First, it is recommended to set the functional unit to one

amount produced hydrogen (Lozanovski, et al., 2011). Secondly, this is a general study without

specific use areas of the hydrogen. Therefore, further specifications regarding hydrogen purity,

pressure or temperature are not be included. The third reason considers the value of 100 kg and

were chosen to ensure a value which possible could be produced by all electrolyzers, regardless

of today’s status. Thus, the production capacity and lifetime are strongly varying (Schmidt, et al.,

2017) and 100 kg can be produced by the current technology in the electrolyzers concerned in

this study. Therefore, several similar studies, such as Giraldi, et al., (2015), have also chosen the

same amount.

19

5.1.2 System Boundaries

The system boundaries are limited to cradle to gate, excluding the end of life treatment of the

electrolyzer, see Figure 9. These boundaries derive from recommendations from the guide for LCA

studies on electrolyzers and fuel cells (Lozanovski, et al., 2011). The foreground processes are the

production of hydrogen and the transport from the electrolyzer supplier to the facility for

production. Because the study is conducted from the perspective of the consumer of the

electrolyzer i.e. the hydrogen producer, and they can influence the environmental impact by the

choice of transportation, electricity mix, the number of hours to run the machine, and how it

operates. The balance of plant (BOP) components, such as heat exchangers, casting or pipes

(Häfele, et al., 2016) are excluded from the study due to limited available data on required BOP-

components for each electrolyzer. However, results from a similar study shows that BOP-

components have minor impact, in comparison to the electricity consumption (Bareiß, et al.,

2019).

Figure 9. The system boundary of the LCA-study.

The complete life cycle of an electrolyzer includes four phases, plus the transports added between

these phases, see Figure 9. The four life cycle phases are; producing the raw materials,

manufacturing of components and the electrolyzer, producing the hydrogen and finally waste

handling. As mentioned above, this study includes the three first main steps; raw material

extraction, manufacturing of the electrolyzer and production of the hydrogen. This cut-off is set

since it is recommended in the guide for complying LCA of electrolyzers or fuel cells by

20

Lozanovski, et al., (2011) since it is the primary life cycle steps of hydrogen gas production. In

addition, the available data are correlating with this system boundaries.

Impact Categories

Impacts categories chosen for the LCIA of this study are based on the categories from the CML

method (2001). This method includes 12 different categories for characterization and

classification of emissions. Six of these categories was chosen for deeper analysis in this study and

the selection was based on the suggestions given in the FC-Hy Guide by (Lozanovski, et al., 2011).

These categories are shown in Table 2.

Table 2. The chosen impact categories for this study.

Parameter Unit Global Warming Potential (GWP 100 years), excl biogenic carbon Kg CO2-eqv

Acidification Potential (AP) Kg SO2-eqv

Photochemical ozone creation potential (POCP) Kg C2H4-eqv

Eutrophication Potential (EP) Kg PO43--eqv

Ozone depletion potential (ODP) Kg CFC11-eqv

Abiotic depletion (ADP fossil) MJ

Abiotic depletion (ADP elements) Kg Sb eq

The selected categories are assumed to cover the important environmental categories, without

double counting the effects.

Geographical Boundary

The geographical boundary was set to Europe, where the electrolyzer assembly was assumed to

take place in Germany and the production of hydrogen was assumed in Sweden. Therefore, the

electricity mix for the manufacturing of the electrolyzer is assumed to be European electricity mix

and the electricity for the hydrogen production is assumed Swedish electricity mix.

Time Boundaries

This study is conducted in 2019 and are based on current circumstances.

5.1.3 Allocation Procedures

No allocation problems arise in the electrolysis. Oxygen is also produced in the electrolysis

process but is often released as emission and therefore assumed the same in this study. See Figure

10 for a visualization of the in- and outflows of an PEMEC.

21

5

Figure 10. The in- and outflows of an electrolyzer.

A general description of the reaction in an electrolyzer is explained in Figure 10. The input is de-

ionized water and electricity, where the outputs are hydrogen and oxygen. There are no direct

emissions of CO2 but can be indirectly in connection to the production of the electricity (Bareiß,

et al., 2019).

In addition, heat is produced in the high temperature electrolyzers. Since available data are

lacking information about common ways for handling the produced heat, it is assumed to not be

handled as a by-product.

5.1.4 Life Cycle Inventory Modelling Framework

In this study, the attributional modeling framework has been applied, rather than consequential,

because the study is focusing on analyzing the potential environmental impacts of existing

technologies, rather than studying the consequences of a change. This study is not focusing on

supplying suggestions on changes in the electrolyzers or manufacturing processes, which is

commonly the focus when using the consequential framework.

The methodology for the LCI framework includes defining the goal and scope, data collection,

modeling the different scenarios, calculation of potential environmental impacts, interpretation

of the results and finally summarize the result and synthesize conclusions. No weighting has been

performed in this study. LCA is an iterative process and, therefore, the initial goal and scope have

been reevaluated due to limited available data.

*There are no direct emissions of CO2 but can be indirectly in connection to the production of the electricity (Bareiß, et al., 2019)

22

5.1.5 Data Quality

This study considers two electrolyzers, and was conducted without collaboration with a supplier,

manufacture nor research site. Due to this, no site-specific data has been available and as a result,

average data from similar LCA studies has been used. Generic data has primary been applied for

the life cycle phases manufacture of electrolyzer and production of hydrogen. Assumptions have

been made where data gaps occurred. In this study, the type, size and distance for the transports

has been estimated with basis on the sizes and an average of distance from Germany to a

prototype center for hydrogen production by electrolyzers, in Sweden.

The data for raw material extraction is defined as not specific for electrolyzer manufacture or

production, and therefore collected through the LCA inventory database Thinkstep AG (2018) and

Ecoinvent 3 (Wernet, et al., 2016). The reasons for using this database is it has a European

perspective and average data sets (Weidema, et al., 2013) and, therefore, representative for the

scope of this study.

5.1.6 Sensitivity Analysis

Sensitivity analysis is applied to test the result and how it is impacting by assumptions or other

parameters which can vary in the input data, to test the robustness of the study. The sensitivity

analysis is presented as a complement to the current design case (Curran, 2015, p. 64) to check

the consistency of the result. An example of an input parameter that can vary is if the technical

lifetime is presented as a span of 10-20 years, the average of 15 years is chosen. A sensitivity

analysis could be to test the impact of changing the lifetime to 20 years.

Two sensitivity analysis was conducted in this study. First, the electricity source for hydrogen

production was changed and thereafter, the base case was compared to a future estimated design

for PEMEC and longer lifetime for SOEC. Available data for PEMEC shows indication of decreased

material weights and longer lifetime, see Appendix 3.

Electricity Mix during Hydrogen Production

The aim of the sensitivity analysis was to evaluate the change in the electrolyzers environmental

impact by comparing electricity mixes used during hydrogen production. Previous studies have

concluded the large impact of the energy source (Giraldi, et al., 2015; Ghandehariun & Kumar,

2016; Zhao & Schrøder Pedersen, 2018). As previously stated, electricity is added in the

manufacturing of the electrolyzer and to hydrogen production. In the sensitivity analysis, the

electricity mix is changed during the hydrogen production phase, see Figure 11. The hydrogen

23

production is a large electricity consumer in the life cycle perspective and, therefore, potential

changes might contribute much in the overall result.

Figure 11. The parameters evaluated in the sensitivity analysis.

The foreground process of this study is the production of the hydrogen, where it is assumed the

hydrogen producer can impact the energy mix to supply the electrolyzer with. This sensitivity

analysis was conducted in two steps. First, the potential environmental impact from supplying the

electrolyzers with Swedish Electricity mix was compared to supplying them with other electricity

mixes: German average, Swiss average, Chinese average and European average. This was chosen

since the available energy supply differs dramatically among regions and countries. Sweden’s

electricity mix has, for example, a large amount of renewable energy, whereas China has more

energy sourced from fossil resources (Giraldi, et al., 2015; Ghandehariun & Kumar, 2016). The

second step of the sensitivity analysis was to compare different electricity sources from Sweden.

This to evaluate and to recommend the best energy source to power the electrolyzer with. The

chosen energy sources for the comparison were wind, nuclear and hydro power.

Future Estimated Design

Since electrolyzers design and performance are constantly under development, it is considered

important to compare the current design to the future estimated design. Then, it is possible to

analyze the result from a future perspective.

24

Much research is ongoing with focus on aspects such as increasing the electrolyzers lifetime,

productivity, and/or decrease material degradation (which is common for the HTE). The large

quantity of research derives from the expected amounts of electrolyzers in the future. Literature

has stated the estimated increase in lifetime, for which future estimations are published (Bareiß,

et al., 2019; Häfele, et al., 2016). Therefore, a conducted scenario has used these numbers for

estimating a possible environmental result. The differences between the base case and the future

estimated development, for PEMEC, are the material weights and the system life time, expressed

in hours. PEMEC´s lifetime in the current design is approximately 40 000 hours, while in the near

future is predicted to 90 000 hours. In addition, the material weights are predicted to decrease.

Titanium is a material which is predicted to decrease from 528 kg in the current design, to 37 kg

in the future estimated development (Bareiß, et al., 2019). The differences for SOEC are longer

estimated life time and decreased electricity consumption during hydrogen production. The

estimated life time is expected to increase from 10 000 to 20 000 hours, and the energy

consumption during hydrogen production is expected to decrease from 65 hWh/produced kg H2

to 42.9 kWh/produced kg H2. The change in life time and material weights impact the input

material weights and detailed information is given in the Appendix 3.

5.1.7 Assumptions and Cut-offs

The LCA-models were based on available data from previous LCA-studies on electrolyzers or fuel

cells. In areas where data was not available, assumptions have been made together with experts

or based on relevant literature on similar subjects. Cut-offs have been conducted where no

relevant information were found, or if it is considered outside the electrolyzer assembly. The

assumptions covering both models are listed below, while detailed assumptions for PEMEC or

SOEC is listed in the Appendix 1.

Assumptions

1. The models are based on available data and assumed to be representative of the current

technology constructions.

2. Most available information regarding materials is presented per kg/MW or kg/kW stack

of energy input in the electrolyzer. It is assumed these that amounts can be scaled linearly

with the functional unit. To explain this further, the functional unit is 100 kg produced

hydrogen, were calculations needed to be conducted to making the input of materials to

relate with the FU. In this calculation, the electrolyzers construction is assumed to be

scaled linearly. An example, 10 kg steel/1kw stack is assumed to be 20 kg steel/2kw stack.

The explanation of how the calculation of the functional unit was done, see Appendix 2

25

3. The efficiency and production rate for the electrolyzers are assumed to be equal during

the complete time frame of the lifetime.

4. Due to lack of available materials within the databases, proxies for the materials have been

chosen. This substitution has been chosen to materials with similar characteristics or

derived from the same material group in the periodic system. This assumption is assumed

to have a minor impact from a life cycle perspective. For example, Iridium was not

available and therefore added as platinum, due to Iridium is a part of the Platinum material

family and both known as Nobel metals (Bradford, 2016).

5. Assumptions has been made for transports and production locations. See the chapter 5.2

Life Cycle Inventory.

6. During a meeting conducted on 14 March, Tomas Rydberg (IVL) stated that transports are

required to be added for the materials to the assembling of the electrolyzers, to conclude

if the transports create any impact on the result between the scenarios. 1000 km has been

chosen for all materials, which is Rydberg’s qualified estimation for all materials to enter

the manufacturing facility in Frankfurt. 1000 km is an assumed average transport distance

from mines to where materials are manufactured. The transports have been added with a

dataset from Thinkstep AG (2018).

7. The BOP was excluded from this study and are assumed to be equal for all technologies.

Cutt-offs

1. Recycling, energy recovery or waste handling of the electrolyzer was not included in this

study, due to recommendations from the guide of electrolyzers and fuel cells (Lozanovski,

et al., 2011).

2. Due to the lack of detailed data, the study does not consider potential water, chemicals,

heat or waste used during the manufacturing of the electrolyzers. Thus, the study only

considers the electricity consumption for the manufacturing process.

5.2 Life Cycle Inventory

This chapter describes the information used in the study. The materials, amount and

manufacturing processes for PEMEC, SOEC and Alkaline derive from literature of similar LCA-

studies and minor information from an electrolyzer manufacturing producer.

The chosen datasets for the PEMEC and SOEC-models are described in Appendix 4. The input data

to models has been created in relation to the FU, including the efficiency, lifetime and amount of

materials, see Appendix 2 for a detailed explanation of how the input data was calculated in

relation to the FU. When data has been given as a range, the average value has been used. An

example is for PEMEC who has a given lifetime of 20 000 – 60 000 hours (Schmidt, et al., 2017),

26

were 40 000 hours has been selected. European electricity mix was chosen for the energy supply

to the manufacturing process, and Swedish electricity mix was chosen for the hydrogen

production phase. The Swedish electricity mix used for the models is explained in Figure 12.

Figure 12. Swedish Electricity Mix for 2014 was used for modelling the base case (Thinkstep AG, 2018).

The electricity mix comes from Thinkstep AG, (2018) and refers to Sweden´s mix, with reference

to 2014, were nuclear power had 45%, hydro power 44.5%, wind power 8% and biomass 6.2%

of the total electricity production.

5.2.1 Data Collection Strategy

The collection of data is emanating from literature, and by qualified assumptions from experts in

relevant areas. In addition, minor data of electricity and water use during hydrogen gas

production has been given from an electrolyzer manufacturing company. The data was modeled

in Gabi and the databases used are Ecoinvent 3 and Thinkstep.

5.2.2 Life Cycle Inventory of PEMEC

In this study, data from Bareiß, et al., (2019) are used. The study from Bareiß, et al., (2019) is

selected, because it is published very recently and is therefore assumed to be updated on the

current component materials, efficiency and electricity use. Moreover, the study from Bareiß, et

al., (2019) does not emanating from a collaboration with a manufacturer, which persuades that

the inventory data is presented transparently. The PEMEC is continuously improving (Bareiß, et

al., 2019) and the study has also presented future potential models. This data has been used for

the Future Estimated Design in this report.

27

Process Flow Chart

The process flow chart of the PEMEC is introduced in this chapter. The flow chart represents all

steps in the life cycle of the electrolyzer, from the raw materials to waste management. The steps

included in the study are marked green, and the parts excluded are market grey see Figure 13.

Figure 13. A description of the material and energy flows for PEMEC´s life cycle phases.

The process flow chart describes the materials found for a PEMEC electrolyzer, and the life cycle

steps included and excluded from the scope, see Figure 13. For the life cycle phase “manufacture

of the electrolyzer”, Bareiß, et al., (2019) has not published any data on heat, water or chemicals

used. The capacity of the PEMEC is 1 MW and the material amounts are given in kg/MW-stack.

The detailed amounts of the materials used and electricity consumption during hydrogen

production is explained in Table 3. For the detailed conversion from kg/MW-stack to the amount

of materials per functional unit, see Appendix 2.

Table 3. The amounts of materials assembled in the PEMEC. All materials emanated from (Bareiß, et al., 2019), except the electricity amount which is an estimation based on the study of (Evangelisti, et al., 2017).

Material (Bareiß, et al., 2019) Amount kg/MW-stack Amount Kg/FU Titanium 528 0.0598 Aluminum 27 0.003 Stainless steel 100 0.011 Copper 4,5 0.001 Nafion 16 0.002 Activated carbon 9 0.001 Iridium 0,75 8.5E-5

Platinum 0,075 8.5E-6

Electricity (Evangelisti et al., 2017) kWh/stack kWh/FU Electricity needed for stack assembly of an electrolyzer with the size of 1 MW. 5360

0.6

28

Next phase in the life cycle of the PEMEC is the production of hydrogen. The transport between

the manufacture and the production facility is estimated to 2364 km, see 5.3.2 Life Cycle Inventory

of Transports. However, the amounts of electricity and de-ionized water were given from NEL,

which is a manufacturer of Alkaline and PEMEC. This information is presented in Table 4. The

amount of electricity and water needed for producing 1 kg of hydrogen are derived from current

production capacity and electrolyzer design (Langås, 2019).

Table 4. The electricity and water consumption during hydrogen gas production (Langås, 2019).

Material or Energy Input Input per kg produced hydrogen Amount per FU

Electricity 57,5 kWh 5750 kWh/FU

De-ionized Water 10 liters 1000 liters/FU

5.2.3 Life Cycle Inventory of SOEC

Limited amount of information is available for LCA on SOEC, were most data found is describing

the fuel cell. The reason for only a few available sources is due to this technology is still in the

research phase and have not been further commercialized. However, the study presented in this

report is emanating an LCA on SOEC (electrolyzer) from Häfele et al (2016). This study is

representative to emanate from because it is recently published and based on a laboratory SOEC.

Due to this, it is not based on materials from a collaboration with one manufacturer and the data

are presented transparently. The study has conducted three different scenarios, where the

material degradation rate varies. This is valid data to considering because much research is

currently ongoing on lowering the material degradation (Häfele, et al., 2016)

29

Process Flow Chart

Figure 14. SOEC´s life cycle and description of which phases are included in the study.

The process flow chart in Figure 14 describes the materials found for 1 kW stack of a SOEC, and

the life cycle steps included and excluded from the scope. For the life cycle phase “manufacture of

the electrolyzer”, the article has not published any data on heat, water or chemicals used. As for

the case for the PEMEC, it was not able to be a given, due to the non-collaboration with one

manufacturer and a realistic guess could neither be provided. No available data was found on

information regarding, for example, water consumption, chemicals or heat used for the

manufacturing of the electrolyzer. See

30

Table 5 for the found data of SOEC. See table 12 in Appendix 2 for the detailed conversion from

g/kW-stack to the amount of materials per functional unit.

31

Table 5. The kind and amounts of material needed in the construction of the 1 kW SOEC-stack. All materials emanate from the study by (Häfele, et al., 2016). See Appendix 2 for the detailed conversion from 1 kW SOEC-stack to input values related to FU.

Material Amount g/kW-stack Amount kg/FU

Chromium steel 20,563 0.007

LSCF/LSCo/PrNi 38 0.013

Yttria Stabilised Zirconia (YSZ) 425 0.143

Yttria-doped Ceria (YDC) 262 0.088

Lanthanum Strontium Manganese (LSM) 4 0.001

Glass sealant paste 59 0.02

Ni/YSZ (Smidt et al., 2017; Jun Chi et al., 2018) 313 0.11

Nickel 181 0.61

Nickel as NiO 515 0.173

Electricity (stack assembly) 49,8 (kWh) 16.7

Production of hydrogen is the next phase in the life cycle of SOEC. The transport between the

manufacture and the production facility is estimated to the same length as PEMEC (to 2364 km),

see chapter Assumptions and Cut-offs. However, the inputs to the hydrogen production process

are electricity and de-ionized water. The required amount of electricity needed is given by Häfele

et al., (2016) and the de-ionized water from Mehmeti et al., (2017). The amounts are presented in

Table 6.

Table 6. The amounts of electricity and de-ionized water per production of one kg hydrogen.

Material or Energy Input Input per kg produced hydrogen Input per FU

Electricity 65 kWh 6500 (kWh/FU)

De-ionized Water 9,1 liters 910 (liters/FU)

5.2.4 Life Cycle Inventory of Transports

Two transport distances are included in this study, to evaluate potential impacts from transports

during the life cycle of the electrolyzers. Both these transports were assumed to be carried out

with a Euro 5 Truck. The first transport is for raw materials to the manufacturing facility of the

electrolyzer. This distance was estimated to 1000 km. The second transport was estimated to

2364 km for all electrolyzers.

5.3 Life Cycle Impact Assessment

The result from this LCA study is presented in this chapter, within the six chosen impact

categories. The result for each category and electrolyzer is showed, described and analyzed in

parallel. The life cycle steps: raw material extraction, transports, manufacturing of the

32

electrolyzer, electricity to hydrogen gas production and production of hydrogen gas have been

used to group the results. Finally, this chapter includes a sensitivity analysis of different electricity

mixes and the electrolyzers future estimated design.

5.3.1 Result

In this chapter, the overall result for three electrolyzers are presented, and a detailed result for

the two electrolyzers: PEMEC and SOEC. See the parallel master thesis Sundin (2019) for detailed

information regarding Alkaline. The results shown in Figure 15 describe the potential

environmental impacts from PEMEC, SOEC and Alkaline.

Figure 15. The characterized result of the chosen impact categories for 100 kg produced hydrogen gas. The technology with the highest, potential environmental impact is shown as 100% impact, and the other technologies are related proportionally to that value.

Figure 15 describes the result of the potential environmental impact of the three studied

electrolyzers. The chart shows the relationship between the three studied electrolyzers, where

the technology with the highest environmental impact shows the impact related to 100%, and the

other technology has been related proportionally to that value.

As seen in the chart, SOEC has the highest potential environmental impact in all categories. The

result derives from SOEC´s design which includes larger quantities of environmentally harmful

materials than the other technologies. This large amount is needed for big material degradation

due to the high temperature during hydrogen production (Schmidt, et al., 2017). Compared to

PEMEC, SOEC requires more electricity per kg produced hydrogen, the difference is 750 kWh/kg

produced hydrogen (6500 kWh-5750kWh). To interpret the result for SOEC and PEMEC in more

detail, the results are presented per technology, divided in life cycle phase.

33

SOEC

The highest potential impact derives from the electricity consumption for hydrogen gas

production, see Figure 16.

Figure 16. SOEC´s potential environmental impact per life cycle phase.

The large potential environmental impact from the electricity derived from the big quantity of

electricity needed to produce 100 kg of hydrogen, see Table 5, in relation to the electricity

consumption in the other life cycle phases. The impact from the energy sources is further

described in the sensitivity analysis. In addition to the energy consumption during hydrogen gas

production, the materials have over half of the impact in acidification potential and approximately

15% to eutrophication potential. Nickel has the highest impact in these categories, see Appendix

7 for a detailed explanation. The large contribution from the nickel derives from two aspects. First,

SOEC contain a heavier weight of nickel, relatively to the other materials in the SOEC-design, see

Table 5. The second reason for the large contribution to the result is the great potential

environmental impact per kg of material, compared to the other materials in the design, see

Appendix 10. Nickels mining operation contributes to high emission of sulfur dioxide, leading to

big values in the acidification potential category. The contribution to global warming is as well

related with the mine operation, and high amounts of heat and electricity from fossil sources

leading to carbon dioxide emissions. In addition, nickel is connected to high amounts of non-

renewable resources. The impact to eutrophication potential derives from the treatment of the

mining waste, in the production, are causing potential phosphate emissions to water. The abiotic

depletion is impacted from the extraction of the metals in the mining process. For clarification,

the nickel-sort that was chosen in this study is not significantly worse than other sorts in the

34

available databases. The potential impact is approximately the average of the alternatives

(Thinkstep AG, 2018).

PEMEC

The electricity for hydrogen production has the highest potential contribution in the life cycle of

PEMEC, see Figure 17.

Figure 17. The contributors to the potential environmental impact from PEMEC.

As mentioned previously, and equally to the SOEC, the electricity for hydrogen gas production has

the largest contribution to the environmental impact over the life cycle. The high value derives

from the energy source and the big impact, in the life cycle of the electrolyzers are related to the

big quantity used in the electricity for hydrogen gas production phase, in relation to the other

phases. Unlike SOEC, the contribution from the materials in the electrolyzer is minor over the life

cycle, because the weight of materials with high environmental impact is small in relation to the

FU. However, platinum has the greatest impact per kg of material compared to equal weight

between the other materials in PEMEC see Appendix 11. However, the weight of platinum in

PEMEC is minor in comparison to nickel, only 9.34E-5 kg/FU, compared to the weight of nickel in

SOEC 0.339 kg/FU. Therefore, the potential impact from platinum is small in relation to the energy

consumption for the life cycle of PEMEC.

35

Comparison between SOEC and PEMEC

To further interpreted the result from each life cycle phase, a comparison of PEMEC and SOEC

related to Global Warming Potential (GWP) are shown in Figure 18. As previously mentioned, the

hotspot for PEMEC and SOEC is the electricity consumption in hydrogen production.

Figure 18. Comparision of SOEC and PEMEC related to GWP.

GWP was chosen as an example to visualize the pattern of the result in this study. Thus, the result

of all categories is similar. The charts for the other impact categories can be found in Appendix 7.

However, the high contribution from the electricity derives from the large amount of electricity

needed for producing 100 kg of hydrogen, in relation to the electricity consumption in the

manufacturing phase and the electrolyzer size. The difference between SOEC and PEMEC derives

from the quantity electricity used, since the source of electricity are equal.

The materials in SOEC has higher contribution to acidification potential, than the electricity

consumption, see Figure 27 in Appendix 7. The reason for the great contribution derives from the

nickel, see Figure 28 and the reason to the big impact is because the extraction process of nickel

requires much non-renewable resources (Thinkstep AG, 2018).

5.3.2 Sensitivity Analysis

Two sensitivity analyses have been carried out. First, the energy source for hydrogen production

has been changed. In addition, a sensitivity analysis of changing the input materials to a future

36

estimated design. The results are showing the potential environmental impact for the whole life

cycle of the electrolyzers.

Energy source

The assumption regarding the energy source for hydrogen production has been tested in a

sensitivity analysis. The energy source for the base case is Swedish electricity mix, and the result

has been compared towards a variation of countries electricity mixes plus renewable energy

sources origin in Sweden. The result from SOEC and PEMEC is presented as GWP (kg CO2

equivalents) for all life cycle steps. The results from the other five categories are presented in

Appendix 5.

The result from the change of energy sources, related to GWP, for PEMEC and SOEC is presented

in Figure 19. The results from the other environmental impact categories described in Appendix

8.

Figure 19. The results from adjusting the energy source for hydrogen production. The impact is measured in CO2 equivalents per FU.

As seen in Figure 19, Chinas electricity mix is contributing to the highest values of CO2 equivalents.

Swedish wind-, hydro or nuclear power contributes to the lowest amounts. The energy source

impacts the electrolyzers life cycle performance dramatically and the result derives highly on the

amounts of fossil contra renewable energy sources. Chinas electricity mix consists of 75% coal

(Thinkstep AG, 2018) and, therefore, has the greatest contribution to PEMEC´s GWP (4990 kg CO2

eq.), while Swedish hydro power has the lowest (50.6 kg CO2 eq.). The amount CO2 equivalents

decreases by 99 times when changing energy source from China Electricity Mix to Swedish

Hydropower. However, the results for the other five impact categories indicates equal pattern to

37

GWP, except abiotic depletion (element) where Swedish wind- and hydro power contributes

much, see Appendix 8. The reason to the big impact on abiotic depletion is the large amount of

non-renewable resources, deriving from the power plant constructions (Thinkstep AG, 2018).

However, the differences between SOEC and PEMEC is primarily connected to the amount of

electricity consumed during hydrogen production. SOEC consumes 6500 kWh to produce 100 kg

hydrogen, while PEMEC consumes 5750 kWh, see Appendix 2.

Future Estimated Development

In this chapter, the results from the comparison of today’s material amounts and lifetime of the

electrolyzers towards the future estimated technology are tested. PEMEC´s life time is expected

to increase from 20 000-60 000 hours to 90 000 hours and the material weights are expected to

decrease (Bareiß, et al., 2019). The new material weights are described in Appendix 3. The

potential environmental impacts, for SOEC´s future estimated design, are connected to an increase

of lifetime from 10 000 hours to 20 000 hours and a decrease of energy consumption during

hydrogen production from 65 kWh/kg produced hydrogen to 42.9 kWh/kg (Häfele, et al., 2016).

The results show the potential contribution to global warming, by comparing the future estimated

technology, and the current design. The results from the other categories are having equal pattern

and are, therefore, presented in Appendix 9.

The chart presented in Figure 20 displays a comparison between PEMEC and SOEC´s future

estimated development to the current design, in the category GWP.

38

Figure 20. A comparison between the current technology to the future estimated design of SOEC and PEMEC.

SOEC has the largest difference between current and future technology, and therefore discussed

further. The impact from GWP for the future estimated development of SOEC derives from the

decrease of electricity consumption during hydrogen production and the longer life time that

minimize the material inputs. Most decrease of GWP comes from the lower electricity

consumption during hydrogen production, see Figure 21.

Figure 21. The lower amount of electricity consumption decreases the potential carbon dioxide emissions with 78 kg CO2 equivalents per FU, when powered by Swedish electricity mix.

39

A lower electricity consumption during hydrogen production is improving the result for SOEC. In

addition, the lower amount of materials is decreasing the potential CO2 eq. with approximately

half, see Figure 22.

Figure 22. The input material weights are decreasing, in relation to the longer life time in the future estimated scenario, which lower the potential impact for GWP to approximately half.

However, from a life cycle perspective, the improvement from the material is minor in comparison

to the electricity consumption. The improvement is approximately 2.5 kg CO2 eq., in comparison

to the decrease due the lower energy consumption of over 50 kg CO2 eq.

PEMEC is expected to have a longer lifetime plus lower material weights in the design, therefore,

the input values decrease. PEMEC´s whole improvement is, therefore, connected to the

electrolyzer design, see Appendix 3, for a quantified description of the changed input material

weights. The result from this comparison shows that receiving less potential environmental

impact from the electrolyzers, the focus should be on the electricity consumption rather than

decreasing of material weights and longer lifetime.

40

6 Life Cycle Interpretation

This chapter consists of two parts. The first part is an explanation of the circumstances and

limitations that might have impacted the results of the electrolyzers potential environmental impact.

The secondly part describes the conclusions drawn in relation to the research objectives.

6.1 Limitations of Results

The results are based on available data where the quantity and quality of this data vary among the

technologies. The results are in relation to the FU of the study. Possible impacts on the results can

have occurred, if the available data does not transparently document all information of important

life cycle steps, such as detailed information regarding the manufacturing. More information is

available for Alkaline than the other technologies, which could be explained by the technology’s

maturity. Obvious differences were adjusted during modeling, where some detailed information

about the manufacturing process was not included from the model of Alkaline. The water

consumption during the manufacturing process found high and was therefore adjusted i.e. less

water was added in the model, see Sundin (2019) for more information. Additional aspects that

could have impacted the results are the level of detail about material sorts. In addition, the

information regarding the electrolyzers was gathered from more than four, distinct sources. In

this study, it is assumed that these are representative for a general application.

Characteristics of the hydrogen gas, such as the purity, temperature and pressure, are excluded

from the functional unit, but are important to highlight since different use areas for hydrogen gas

requires specific qualities. Adding characteristics to the hydrogen gas is important from a system

perspective, because it could require other equipment around the electrolyzer. Therefore, adding

such characteristics is recommended for future studies. The reason for excluding the

characteristics in this study is because the hydrogen gas produced is not dedicated a certain

purpose. In this respect, the potential environmental impact might be impacted if the electrolyzer

needs extra equipment to, for example, change the purity of the hydrogen.

Due to limited available data, the potential impacts from the BOP are excluded from the scope of

this study. This might be considered important since the sizes of the electrolyzers are different

and it can therefore have an impact on the weight of the machine foundation, number of pipes, etc.

The BOP could have an impact on all phases of the electrolyzers life cycle, such as material or

transport.

The materials chosen are based on the available materials in Thinkstep AG (2018) and Ecoinvent

3. These material choices were prioritized to first select data which represent Europe, and

secondly Global. The global datasets are averages from many countries, and the impact from this

might vary depending on actual origin. Nickel is, as an example, chosen with a global basis and are

41

having a great contribution to the impacts of the materials. Due to this large contribution, it might

be considered important to test the variation in the impact’s differences among the origin of the

materials.

The SOEC contain materials which are not included in the available databases, where substitutes

have been chosen. In addition, PEMEC includes three sorts of nickel which was added as one type

in the model. Future LCA-models should include more detailed material choices, even though the

result from this study does not indicate that the raw materials are the main contributor.

6.2 Conclusion

In this study, the electricity supply for the hydrogen production contributes the most to the

potential environmental impact for Alkaline, PEMEC and SOEC, with less influence from the

components. The reasons are the electricity source and the great amount of electricity required

in the current hydrogen gas production processes.

Nickel has the highest contribution to the impact of the materials in the SOEC design. This impact

derives from two reasons. First, the material has a higher potential environmental impact per kg,

than the other materials in SOEC. In addition, the weight of nickel is higher than the other

materials.

The result of this study answers the research questions:

• Which of the four electrolyzers are having the best potential environmental performance?

The result of this study shows that PEMEC has the lowest environmental result in five of six selected

categories, from all stages of the life cycle. This is a result of low weight of potentially environmental

harmful materials, plus low energy consumption during the hydrogen production phase.

• Which are the environmental hotspots?

In this study, the highest environmental impact for PEMEC, Alkaline and SOEC are the electricity for

hydrogen production. This high impact is caused by large electricity consumption and the energy

source.

• How does the energy source during hydrogen production, and the future estimated design impact the environmental result for SOEC and PEMEC?

The energy source during hydrogen production has a great impact on the overall result of this study.

Energy mixes with fossil sources have a higher impact than renewable sources, and lead to a great

increase of the total potential environmental impact of SOEC and PEMEC.

42

• What is the potential environmental impact for the future estimated development for SOEC and PEMEC, compared to current technology?

SOEC´s and PEMEC´s future estimated design is decreasing the environmental impact in all

categories, compared to the current design. Related to GWP, the difference is around 17% better for

SOEC and approximately 2% for PEMEC. SOEC´s improvement derives from the lower energy

consumption during hydrogen production, together with minor improvement from the lower weights

of input materials (in relation to the functional unit calculation, due to a longer life time). PEMEC´s

improvement is minor and connected to a longer lifetime, which decreases the input materials in

relation to the functional unit. In addition, PEMEC has lower weights of materials in the future

estimated design.

• What are the current data gaps and information needed for conducting a more comprehensive LCA for future studies?

The current data gaps are:

1. Detailed information regarding the manufacturing of the electrolyzer, such as the type of manufacturing processes, chemicals- and water use.

2. Detailed information on the materials in the electrolyzer design. 3. Information on the BOP-components. 4. Transportation distances for the materials and the electrolyzer and the kind of transport.

43

7 Recommendations and Reflections

This chapter consists of three parts. First, a recommendation for future studies is described. Secondly,

a reflection of comparison between the electrolyzers is explained and finally, a discussion of materials

in the electrolyzer design.

7.1 Recommendations for Future Studies

A strong recommendation for future studies is to include more detailed information on up- and

downstream processes in the model, which might be achieved by having a close collaboration with

manufactures of electrolyzers. This might enhance getting greater firsthand information

regarding sorts and amounts of materials plus detailed manufacturer information such as

amounts of chemicals, energy or manufacture method for different components. By doing this, the

comparability among the life cycle phases will be secured better.

Furthermore, adding characteristics to the FU to ensure equal product quality is recommended.

This could be carried out by specifying certain use of the hydrogen, that requires specific

characteristics such as purity, pressure and temperature.

Another reflection is to add all life cycle phases to the LCA-model, including the waste handling,

to ensure all relevant inputs to the models are counted for. Since the electrolyzers are including

non-renewable materials from scarce resources, it is important to consider the end life treatment.

In addition, it might be considered important to evaluate the environmental performance by

adding heat (for HTE) and oxygen during hydrogen production as a by-product. By handling these

as by-products instead of emissions would result in an allocation procedure.

Furthermore, the scope of this study is limited to only focusing on the potential environmental

impacts from the electrolyzers and excluded the potential economic and social issues. Further

studies can include these issues to enhance a more comprehensive study that covers all pillars of

sustainability.

7.2 Reflections of the Electrolyzer Comparison

The electricity consumption during hydrogen production has the highest environmental impact

on the life cycle for SOEC and PEMEC. The high impact is due to the large quantity of electricity

used, together with the energy source. The focus should be the source of electricity, rather than

comparing technologies, for achieving good environmental performance for the electrolyzers. In

addition, the result from this study indicates that focus for R&D, for achieving a good

44

environmental result, should be to decrease the energy consumption instead of focusing on

decreasing the material weights or changing the material sort in the design.

Since the accessible energy sources are differing among regions, it is also important to consider

the location of the electrolyzer. A region with access to renewable energy sources, but with a long

distance to the location be where the hydrogen is intended to be used, can be more appropriate

since hydrogen gas can be transported long distances.

7.3 Material Supply

Raw materials are critical to Europe´s economy, because the scarcity of some materials would

impact the industry, environment and technology (European Commission, u.d.). The European

Commission has compiled a list of critical materials for Europe. The materials are evaluated by

the economic importance and the supply risk. The economic importance is based on the

importance of the material for use within the EU and the consequences of limited access, plus

considering substitutes in these applications. The supply risks are evaluated based on the risks

for a disruption of the supply of the materials (for example the import reliance or critically of

substitutes). European Commission (u.d.) highlights the importance of increasing the circularity

for these materials and to increase local extraction. Local mining can, in addition to less risk in

terms of economic consequences, lead to better ecological and social development, since todays

mining activities are situated in developing countries with less strict environmental and social

regulations (Carvalho, 2017). Toxic mine waste leads to high concentration of chemicals in the

water and food chain, having crucial effects on the human health (Nordstrom, 2011).

The list of critical raw materials is updated every third year, where 20 materials was included in

the report for 2014. Here, the highest ranked material-group for is the platinum family, which are

included in the PEMEC. Iridium and platinum (platinum group) are greatly dependent on import

and a disruption would lead to a high economic risk for EU (COM, 2014). More critical materials,

in terms of economic risks, are added in the report from British Geological Survey et al., (2017),

such as manganese and nickel (components in SOEC), titanium (material in PEMEC). Moreover,

lanthanum (included in SOEC) are very high ranked regarding supply risks (British Geological

Survey, et al., 2017).

Critical raw materials might be an obstacle for companies and government to invest in

electrolyzers, because of the risk of stopping the supply of energy carrier and fuel, because of

scarcity of ex spare parts. The supply of materials in the electrolyzers can cause problems in terms

45

of limited availability of materials for manufacturing. An increased amount of electrolyzers results

in higher demands for these critical raw materials. A society who has implemented hydrogen gas

as a fuel, energy carrier or chemical to the industry in a large extent, would be greatly affected if

the supply would stop or decrease. To minimize the risks of scarce materials in the future, it might

be important to consider substitutes for these materials or purchasing electrolyzers with less

critical materials in the design. In addition, electrolyzers waste handling are crucial since the

circularity of these materials must increase. The production methods for hydrogen gas are

important to consider achieving a sustainable result over the whole life cycle. The implemented

technologies for energy carriers need to be secure in the supply, the material extraction and waste

handling, to not challenge future generations to meet their needs in terms of toxicity in food chain

in addition access to energy supply.

46

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50

Appendix 1 - Material choices differences from the original material

in the electrolyzer design

Detailed assumptions for SOEC and PEMEC

The material choices in Gabi is preferably the same as the materials in the electrolyzer design. However, due to limited amounts of material choices in the available data bases, this was not possible for all materials. Then, substitute materials have been chosen with the intention to be as alike the material as possible, in terms of properties or derive from the same material group in the periodic system. This was especially the case for SOEC, who has unique materials for the specific purpose of electrolysis.

SOEC

Table 7. The material choices differences from the original material in the electrolyzer design

Material choices differing from the original material in the electrolyzer design

Original Material Material Chosen in Gabi

(Comment)

Lanthanum Strontium Manganese (LSM)

Lanthanum (50%) Manganese (50%)

This material is an alloy and is therefore added as two separate materials (lanthanum and manganese), assuming the alloy consist of 50% lanthanum and 50% manganese.

Nickel Oxide Nickel 99,5% Lanthanum strontium cobalt ferrite (LSCF)/lanthanum strontium cobalt oxide (LSCo)/praseodymium nickel (PrNi)

Praseodymium LSCF is a specific ceramic oxide derived from lanthanum cobaltite of the ferrite group.

Yttria Stabilised Zirconia (YSZ)

Lanthanum oxide

Yttriadoped Ceria (YDC) Cerium oxide

Glass Sealant Paste Glass Fibre

PEMEC

Table 8. The material choices for the materials in the original electrolyzer design

Material choices differing from the original material in the electrolyzer design

Original Material Material Chosen in Gabi (Comment) Iridium Platinum Iridium is a part of the

platinum family and have similar characteristics.

Nafion Polytetrafluoroethylene granulate (PTFE)

This material is a flour polymer too.

51

The electricity needed for the manufacturing of the electrolyzer was not available in

any available literature where the amounts of materials needed was published. Therefore, the

values presented in the data gathering emanates from production of PEMFC, with the assumption

that these values are equal between an electrolyzer and a fuel cell.

52

Appendix 2 – Calculation input of material and electricity to be modelled in relation to the FU

The functional unit (100 kg produced hydrogen) is calculated in four steps to finally be modelled as input material per 100 kg produced hydrogen. The

calculation is first explained in words, then the specifications for PEMEC and SOEC are explained in Table 9 and the calculations for PEMEC and SOEC are

described in Table 10. I have taken an example from PEMEC to explain the procedure.

Table 9. Characteristics of SOEC and PEMEC in the current design. The lower heating value is the released heat when combusting hydrogen (Godula-Jopek, 2015).

Specification

PEMEC SOEC

Effectivness (%) (Jun Chi et al., 2018) 73.5 99

Life time Electrolyzer (hours) (Schmidt et al., 2017) 40 000 10 000

Energy content in H2 (kJ/kg) (Godula-Jopek, 2015) 119 800 Lower Heating Value (LHV)

1. The energy per second out from the electrolyzer is calculated by multiplying the electrolyzers capacity with the efficiency. PEMEC´s efficiency is 73,5% and SOEC´s approximately 99% (Jun Chi et al., 2018) PEMEC´s capacity is 1 MW (or 1 000 kJ/s) and SOEC´s 1kW (or 1 kJ/s) (the sizes are connected to the specific electrolyzer evaluated in this study).

2. To get kg produced per hour, the number from step one was divided with the energy content of hydrogen (119800kJ/kg). 3. The amount of hydrogen gas produced during the estimated life time were calculated by multiply the production/hour with the lifetime of the

electrolyzers. PEMEC life time (40 000 hours) and SOEC (10 000 hours).

4. To get the input materials/FU, the amounts of the materials (kg) was divided with the amount hydrogen produced during the lifetime and multiplied with 100 kg.

53

Table 10. Explanatory table of the calculation process of the total hydrogen production during the electrolyzers life time.

1. Hydrogen out from Electrolyzer = Capacity*Efficiency

PEMEC SOEC

1000 (kJ/s) * 0.735=735 (kJ/s) 1 (kJ/s) *0.99=0.99 (kJ/s) 2.To get kg/hour produced, the number from step one is divided with energy content for hydrogen (119 800 kJ/kg)

PEMEC SOEC

735 [𝑘𝐽

𝑆] ∗

1

119 800[

𝑘𝑔

𝑘𝐽] ∗ 3600 [

𝑠

ℎ] = 22.1 [

𝑘𝑔 𝐻2

ℎ] 0.99 [

𝑘𝐽

𝑆] ∗

1

119 800[

𝑘𝑔

𝑘𝐽] ∗ 3600 [

𝑠

ℎ] = 0.0297 [

𝑘𝑔 𝐻2

ℎ]

3. The amount of hydrogen produced during the estimated life time is calculated by production/hour multiplied with estimated life time

PEMEC SOEC

22.1*40 000=883 472 (kg H2) 0.0297*10 000=297 (kg H2)

54

Table 11. The input materials in a 1 MW PEMEC. The numbers are converted from 1 MW-stack to amounts related to 100 kg produced hydrogen.

4. Amount input material per 100 kg produced hydrogen. This information is given by the study from Bareiß el al., 2019.

PEMEC

Material Amount kg/MW-stack

Amount Material/Amount hydrogen produced during lifetime *100 (kg)

Titanium 528 0,059764172

Aluminium 27 0,003056122

Stainless steel 100 0,011318972

Copper 4,5 0,000509354

Nafion 16 0,001811036

Activated carbon 9 0,001018707

Iridium 0,75 8,48923E-05

Platinum 0,075 8,48923E-06

Electricity (Evangelisti et al., 2917) (stack assembly) (kWh) 5360 0,606696901

Energy and water consumption during production of hydrogen. This information emanates from an email by the company NEL.

Material Amount per 100 kg produced hydrogen

Input

Electricity 57,5 kWh/kg 5750

De-ionized Water 10 kg/kg produced hydrogen 1000

Output

Oxygen 794

Hydrogen 100 kg

55

Table 12. The materials in a SOEC in one kW stack and converted in relation to 100 kg produced hydrogen.

SOEC. All information emanates from the study by Häfele, et al., (2016)

Material

Amount kg/kW-stack

Amount Material/Amount hydrogen produced during lifetime *100 (kg)

Chromium steel 0,02056

3 0,00691

LSCF/LSCo/PrNi 0,038 0,01277

Yttria Stabilised Zirconia (YSZ) 0,425 0,14286

Yttriadoped Ceria (YDC) 0,262 0,08807

Lanthanum Strontium Manganese (LSM) 0,004 0,00134

Glass sealant paste 0,059 0,01983

Ni/YSZ (Smidt et al., 2017; Jun Chi et al., 2018) 0,313 0,10521

Nickel 0,181 0,06084

Nickel as NiO 0,515 0,17311

Electricity (stack assembly) kwh/kW-stack 49,8 16,73973

Energy and water consumption during production of hydrogen. All information emanates from the study by Häfele, et al., (2016)

Material Per 100 kg produced hydrogen

De-ionized water (kg/kgH2) (Mehmeti et al., 2017) 9,1 910

Electricity (kwH/kgH2) 65 6500

Oxygen 794

56

Appendix 3 – Material inputs for the sensitivity analysis

The life time and the material amounts are the changes from the current design to the future estimated development. The input values are calculated equally to the procedure described in Appendix 2. The material amounts for PEMEC are decreased by the values shown in Table 13. Table 13. The materials used for modelling the PEMEC, with a capacity of 1 MW.

Material (kg) Current Design Future Estimated Development Titanium 528 37 Aluminium 27 54 Stainless Steel 100 40 Copper 4.5 9 Activated Carbon 9 4.5 Iridium 0.75 0.037 Platinum 0.075 0.010

In addition to the changed materials, the life time of the electrolyzer is expected to increase from 40 000 hours (in average) to 90 000 (Bareiß, et al., 2019). This decreases the input materials, in relation to the FU as Table 14. Table 14. The quantities of input materials for the PEMEC model in relation to the future estimated development.

PEMEC

Material Amount kg/MW-stack (Material amount/amount hydrogen produced during life time) *100 (kg)

Titanium 528 0,026561854 Aluminium 27 0,001358277 Stainless steel 100 0,005030654 Copper 4,5 0,000226379 Nafion 16 0,000804905 Activated carbon 9 0,000452759 Iridium 0,75 3,77299E-05 Platinum 0,075 3,77299E-06 Electricity (Evangelisti et al., 2917)((kWh/cell)*8) dvs kwh/MW-stack 5360 0,269643067

57

The lifetime for SOEC is expected to increase from 10 000 hours to around 20 000 hours. The material inputs changes in correlation with the FU as described in Table 15. Table 15. The input of materials in relation to a longer life time.

SOEC. All information emanates from the study by Häfele, et al., (2016)

Material Amount kg/kW-stack (Material amount/amount hydrogen during life time) *100 (kg)

Chromium steel 0,020563 0,003456015

LSCF/LSCo/PrNi 0,038 0,006386644

Yttria Stabilised Zirconia (YSZ) 0,425 0,071429574

Yttriadoped Ceria (YDC) 0,262 0,044034231

Lanthanum Strontium Manganese (LSM) 0,004 0,000672278

Glass sealant paste 0,059 0,009916105

Ni/YSZ (Smidt et al., 2017; Jun Chi et al., 2018) 0,313 0,05260578

Nickel 0,181 0,030420595

Nickel as NiO 0,515 0,086555836

Electricity (stack assembly) 49,8 8,36986532 Table 16. The electricity and water consumption during hydrogen production for SOEC. The energy consumption has decreased from 6500 kWh to 4290 kWh.

Material Per 100 kg produced hydrogen

De-ionized water (kg/kgH2) (Mehmeti et al., 2017) 9,1 910

Electricity (kwH/kgH2) 65 4290

Oxygen 794

Energy and water consumption during production of hydrogen. All information emanates from the study by Häfele, et al., (2016)

58

Appendix 4 - Data sets

The data is presented in for the processes and material choices in GaBi.

Data set for the LCA-model of PEMEC in Gabi

Table 17. The data set used for the model of PEMEC in Gabi.

Resource - Processes Raw Materials

Dataset in GaBi Type Nation Source Parent Folder Last change

Titanium titanium production, primary agg GLO Ecoinvent 3 242: Manufacture of basic precious and other non-ferrous metals 2019-01-15

Aluminium Aluminium sheet mix agg EU-28 Thinkstep Metal production 2018-02-01

Stainless steel Stainless steel sheet (EN15804 A1-A3) p-agg EU-28 Thinkstep Stainless steel sheet 2018-02-01

Copper Copper sheet mix agg EU-28 DKI/ECI Copper 2018-02-01

Nafion Polytetrafluoroethylene granulate (PTFE) Mix agg DE Thinkstep Plastic Production 2018-02-01

Activated carbon Market for activated carbon, granular agg GLO Ecoinvent 3 2029: Manufacture of other chemical products n.e.c.

Iridium Platinum mix agg GLO Thinkstep Metal production 2018-02-01

Platinum Platinum mix agg GLO Thinkstep Metal production 2018-02-01

Electricity Electricity Production (consumption mix) LC EU-28 Thinkstep Electricity 2018-10-08

Resource - Transport of PEMEC


Truck B2a. TruckTrailer 28-34 t, MPL 22 t, Euro 5

59

Table 18. The data set used for the hydrogen production process. The electricity source is for the base case.

Resource - Process of Hydrogen

Dataset in GaBi

Type Nation Source Parent Folder Last change

Input

Electricity Electricity mix agg SE Thinkstep Supply grid mix 2018-02-01

De-ionized water

Water (deionised) agg EU-28 Thinkstep Water 2018-02-01

60

Data set choices for the model of SOEC in Gabi

Table 19. The data set for the manufacture of the SOEC-model.

Resource - Processes raw materials


Electricity (Stack assembly) Electricity Production (consumption mix) LC EU-28 Thinkstep Electricity 2018-10-08

Chromium steel

Stainless steel (based on cold rolled 304) (Eurofer, 2008, RER): Used when unspecified LC Eurofer Thinkstep Eurofer 2018-03-30

Lanthanum strontium cobalt ferrite (LSCF)/lanthanum strontium cobalt oxide (LSCo)/praseodymium nickel (PrNi)

Praseodymium oxide to generic market for mischmetal agg GLO Ecoinvent 3 Manufacture of basic chemicals 2019-01-15

Yttria Stabilised Zirconia (YSZ) Market for lanthanum oxide agg GLO Ecoinvent 3 Manufacture of basic chemicals

Yttriadoped Ceria (YDC) Cerium oxide to generic market for polishing powder agg GLO Ecoinvent 3 Manufacture of basic chemicals

Lanthanum Strontium Manganese (LSM)

Lanthanum & manganese production agg

CN and RER

Thinkstep and Ecoinvent 3

Manufacture of basic chemicals and Manufacture of basic precious and other non-ferrous metals 2019-01-15

Glass sealant paste Glass Fibre Production agg RER Ecoinvent 3 Manufacture of glass and glass products 2019-01-15

Ni/YSZ (Smidt et al., 2017; Jun Chi et al., 2018) Market for nickel, 99,5% agg GLO Ecoinvent 3

Manufacture of basic precious and other non-ferrous metals 2019-01-15

Nickel Market for nickel, 99,5% agg GLO Ecoinvent 3 Manufacture of basic precious and other non-ferrous metals 2019-01-15

Nickel as NiO Market for nickel, 99,5% agg GLO Ecoinvent 3 Manufacture of basic precious and other non-ferrous metals 2019-01-15

Resource - Transport of PEMEC Dataset in GaBi Type Nation Source Parent Folder Last change

Truck B2a. TruckTrailer 28-34 t, MPL 22 t, Euro 5

61

Table 20. The data set for hydrogen production process for SOEC.

Resource – Plan Process of Hydrogen Production


Input

Electricity Electricity mix agg SE Thinkstep Supply grid mix 2018-02-01

De-ionized water Water (deionised) agg EU-28 Thinkstep Water 2018-02-01

Output

Hydrogen Hydrogen Valuable Other Fuels 2016-01-01

Oxygen Oxygen Inorganic emissions to air 2017-01-01

62

Appendix 5 - Data set Sensitivity Analysis

This appendix describes the different electricity sources used to evaluate the impact for the hydrogen production process.

Table 21. The data sets for the sensitivity analysis of changing the electricity mix.

The Sensitivity Analysis choices for Electricity Mix Source

Dataset in GaBi Nation Source Parent Folder

Electricity Production (consumption mix) EU-28 Thinkstep Electricity

Electricity from Hydropower SE Thinkstep Electricity from Hydro power

Electricity fron Nuclearpower SE Thinkstep Electricity from Nuclear power

Electricity from Windpower SE Thinkstep Electricity from Wind power

Electricity supply mix SE Thinkstep Production Mix

Electricity supply mix CN Ecoinvent 3 Production Mix

Electricity supply mix CH Ecoinvent 3 Production Mix

Electricity supply mix DE Ecoinvent 3 Production Mix

63

Appendix 6 – The results presented in numbers for PEMEC, SOEC and Alkaline

The quantified result from the comparison between PEMEC, SOEC and Alkaline is described in this appendix. The result is presented in numbers to enable further

interpretation, instead of limiting the presentation of the result related to the technology with highest potential environmental impact.

Table 22. The quantified result for the four electrolyzers in the chosen impact categories.

Impact Category PEMEC SOEC Alkaline Unit

Abiotic Depletion (ADP elements) 0.001 0.001 0.001

kg Sb eq

Abiotic Depletion (ADP fossil) 1750 1410 1570 MJ

Acidification Potential (AP) 0.881 1.98 1.32 kg SO2 eq

Eutrophication Potential (EP) 0.168 0.224 0.17 kg

Phosphate

eq

Global Warming Potential (GWP 100

years), excl biogenic carbon

260 322 231 kg CO2 eq

Photochem. Ozone Creation Potential

(POCP)

0.104 0.161 0.116 kg Ethene

eq

64

Appendix 7 – A comparison of the life cycle phases between SOEC and

PEMEC

This appendix shows the result between the life cycle phases for SOEC and PEMEC. All categories have the

potential highest contribution from the electricity during hydrogen production. However, the materials in

SOEC impact the result in some categories. Nickel is the main contributor to this result, were the pattern is

equal in all impact categories. The distribution between the impacts from Nickel and the other materials are

described in pie charts to each category.

GWP

See Figure 23 for a comparison between SOEC and PEMEC related to GWP in a quantitative chart and see Figure 23 for the contribution from the materials in SOEC.

Figure 23. The result of the contributions from each life cycle step for PEMEC and SOEC

65

Figure 24. The impact to GWP from the materials in the SOEC-design.

Abiotic Depletion (ADP elements)

In addition to the energy consumption, SOEC has an impact from the materials Figure 25.

Figure 25. The potential impact of the category Abiotic Depletion (elements) and the life cycle phases which are contributing to this

value.

Majority of the contribution from the materials derive from nickel, see Figure 26.

66

Figure 26. SOEC´s materials potential environmental impact in the Abiotic Depletion (elements) category.

Abiotic Depletion (ADP fossil)

The comparison between SOEC and PEMEC are shown in Figure 27. SOEC has slightly higher potential environmental impact in the category abiotic depletion (fossil), than the PEMEC. The difference between SOEC and PEMEC is only 40 MJ.

Figure 27. Potential impact to Abiotic Depletion visualized over the life cycle.

The contribution to abiotic depletion (fossil) from the materials are shown in Figure 28.

67

Figure 28. The contribution from SOEC´s materials to Abiotic Depletion (fossil).

Acidification Potential (AP)

SOEC´s contribution from the material is big in comparison to the electricity consumption, see Figure 29.

Figure 29. The life cycle steps contribution to acidification potential.

SOEC´s impact from the materials derives from the nickel, see Figure 30.

68

Figure 30. The materials in SOEC´s designs impact to acidification potential.

Eutrophication Potential (EP)

Figure 31. The contribution per life cycle steps of PEMEC to Eutrophication Potential.

SOEC´s impact to Eutrophication Potential from the materials comes from nickel, see Figure 32.

69

Figure 32. Nickel contributes most to the Eutrophication Potential.

Photochemical Ozone Creation Potential The life cycle phases contribution to Photochemical Ozone Creation Potential are shown in Figure 33.

Figure 33. The potential impact to the Photochem. Ozone Creation Potential.

As well as for the other technologies, SOEC´s impact on the materials derives from nickel, see Figure 34.

70

Figure 34. The material impact to Photochem. Ozone Creation Potential for SOEC.

71

Appendix 8 – Sensitivity analysis, results of changed electricity mix

The results from the change of electricity mixes are described in charts per environmental impact category, comparing SOEC to PEMEC. The results are showing the

total impact for the whole life cycle. The results for SOEC are marked red, and PEMEC blue. The potential environmental impacts correlate with the amount of

renewable and non-renewable energy sources in the electricity mixes except for abiotic depletion where Swedish wind power has high contribution, because of the

wind power construction (Thinkstep AG, 2018).

Abiotic Depletion (elements)

The comparative chart between PEMEC and SOEC´s potential environmental impact in relation to Abiotic Depletion (elements), see Figure 35.

Figure 35. The result from changing the electricity mixes for PEMEC and SOEC, in relation to Abiotic Depletion (elements).

72

Abiotic Depletion (fossil)

The comparative results for the potential impact to Abiotic Depletion (fossil) are described in Figure 36.

Figure 36. The potential environmental impact related to Abiotic Depletion (fossil).

73

Acidification Potential

Figure 37. Comparison between different electricity mixes impact on the potential impact to Acidification Potential for SOEC and PEMEC.

74

Eutrophication Potential

Figure 38. Comparison between different electricity mixes impact on the potential impact to Eutrophication Potential for SOEC and PEMEC.

75

Photochemical Ozone Creation Potential

Figure 39. Comparison between different electricity mixes impact on the potential impact to Photochemical Ozone Creation Potential for SOEC and PEMEC.

76

Appendix 9 - Result from Estimated Future Design, presented by category

The Estimated Future Design is considering parameters that will change soon. For PEMEC, the future

estimated design consists of longer life time (90 000 hours instead of 40 000 as average) plus a decrease of

material weights (Bareiß, et al., 2019). SOEC´s future estimated design consists of longer life time too (20 000

hours) plus decrease of energy consumption during hydrogen production (from 6500 kWh to 4290 kWh, in

relation to the FU) (Häfele, et al., 2016). The result is presented per chosen impact category. The potential

impact of GWP is shown in the report.

Figure 40. Potential impact to Abiotic Depletion (fossil) from future estimated development compared to current design for SOEC and PEMEC.

Figure 41. Potential impact to Abiotic Depletion (elements) from future estimated development compared to current design for SOEC and PEMEC.

77

Figure 42. Potential impact to Acidification Potential from future estimated development compared to current design for SOEC and PEMEC.

Figure 43. Potential impact to Eutrophication Potential from future estimated development compared to current design for SOEC and PEMEC.

0

0,05

0,1

0,15

0,2

0,25

SOEC Current design SOEC FutureEstimated

Development

PEMEC Currentdesign

PEMEC FutureEstimated

Development

Eutrophication Potential[kg

78

Figure 44. Potential impact to Photochem. Ozone Creation Potential from future estimated development compared to current design for SOEC and PEMEC.

The potential environmental performance decreases in the future estimated development, compared to the

current design, as seen in all categories presented in Figure 40, Figure 41, Figure 42, Figure 43 and Figure

44. The greatest difference is for SOEC in the GWP-category, which depends on the electricity consumption.

The lower input materials make a small change in the potential impact result, but the larger difference

relate to the energy consumption.

79

Appendix 10 – Comparison of the materials in the SOEC-design,

For SOEC, the material impacts are caused by nickel. To evaluate if the potential environmental impact from

nickel only depends on the greater weight, or if the material per kg is higher too, a comparison to the other

material are presented. The comparison was related to the same weight. Nickel has the highest contribution

in most of the impact categories, especially to Abiotic Depletion (elements), Acidification Potential,

Eutrophication Potential and Photochemical Ozone Creation Potential.


Figure 45. The impacts per kg from all materials in the SOEC, related to Abiotic Depletion.

Photochem. Ozone Creation Potential

Figure 46. The impacts per kg from all materials in the SOEC, related to Abiotic Depletion.


0,00E+001,00E-042,00E-043,00E-044,00E-045,00E-046,00E-047,00E-048,00E-049,00E-041,00E-03

[kg Sb eq.]

0

0,02

0,04

0,06

0,08

0,1

0,12

0,14

[kg Ethene eq.]

80

Figure 47. The impacts per kg from all materials in the SOEC, related to Abiotic Depletion (fossil).


Figure 48. The impacts per kg from all materials in the SOEC, related to Acidification Potential.

0

100

200

300

400

500

600

[MJ]

00,5

11,5

22,5

33,5

[kg SO2 eq.]

81


Figure 49. The impacts per kg from all materials in the SOEC, related to Eutrophication Potential.

GWP

Figure 50. The impacts per kg from all materials in the SOEC, related to GWP.

0

0,02

0,04

0,06

0,08

0,1

0,12

[kg Phosphate eq.]

0

5

10

15

20

25

30

[kg CO2 eq.]

82

Appendix 11 – Comparison of the materials in PEMEC´s design

The potential environmental impact from PEMEC´s materials are limited. But to evaluate the impact from the

materials in the PEMEC´s design, a comparison off all materials, in relation to equal weight, is presented.


Figure 51. The impacts per kg from all materials in PEMEC, related to Abiotic Depletion (elements).


Figure 52. The impacts from the materials in PEMEC, related to Abiotic Depletion (fossil).

00,20,40,60,8

11,21,41,61,8

2

[kg Sb eq.]

0

50000

100000

150000

200000

250000

300000

350000

400000

[MJ]

83


Figure 53. PEMEC´s materials impact on Acidification Potential.


Figure 54. The materials in PEMEC´s impact to Eutrophication Potential.

0

100

200

300

400

500

600

700

800

[kg SO2 eq.]

0

5

10

15

20

25

[kg Phosphate eq.]

84

Global Warming Potential

Figure 55. The materials in PEMEC contribution to GWP

Photochemical Ozone Creation Potential

Figure 56. The materials in PEMECs impact on Photochemical Ozone Creation Potential.

0

5000

10000

15000

20000

25000

30000

35000

40000

[kg CO2 eq.]

0

5

10

15

20

25

30

35

[kg Ethene eq.]

85

TRITA TRITA-ABE-MBT-19543

www.kth.se

www.kth.se

http://www.kth.se/

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