Supplementary Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants

Supplementary Material for: Prospective Life Cycle Assessment of LargeScale Low Temperature Water Electrolysis Plants Janis Gerhardt-Mörsdorf1, Sebastian Braukhoff2, Andreas Lindermeir3, Christine Minke1 1 Clausthal University of Technology, Institute of Energy Process Engineering and Fuel Technology, Leibnizstr. 23, 38678 Clausthal-Zellerfeld, Germany, [email protected] (CA), [email protected] 2 Clausthal University of Technology, CUTEC Clausthal Research Center for Environmental Technologies, Leibnizstr. 23, 38678 Clausthal-Zellerfeld, Germany 3 Clausthal University of Technology, Institute of Chemical and Electrochemical Process Engineering, Leibnizstr. 17, 38678 Clausthal-Zellerfeld, Germany, [email protected] Key words: Green hydrogen, PEM water electrolysis, alkaline water electrolysis, prospective life cycle assessment, process engineering, environmental impacts, sustainability Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 2 1. Description of Proton Exchange Membrane and Alkaline Water Electrolysis technologies In this section a detailed description of both the PEM (PEMWE) and alkaline water electrolysis (AWE) technologies are given along with the anticipated technological developments until 2050. 1.1 Technological development of Proton Exchange Membrane Water Electrolysis For the discussion of the electrolyzer stacks, the governing parameters are divided into operational parameters that describe the performance of the technology during operation and constructional parameters that describe the material demand for the manufacturing. The operational KPIs comprise all parameters that affect the energy and material demand for the plant operation. Table 1 gives an overview over the operational KPIs for a PEMWE state-of-the-art stack in 2025 as well the respective anticipated developments for 2030 and 2050. Central parameters for the stack performance are the current density, the cell voltage and the cell degradation rate. They have a determining influence on the amount of produced hydrogen over the lifetime and the associated specific energy demand (SED). The current density is directly proportional to the area specific amount of produced hydrogen. Consequently, the higher the current density, the more hydrogen per cell area can be produced. The cell voltage can be interpreted as an indicator for the stack efficiency. It is closely related to the performance of the stack and increases with increasing current density. The lower the cell voltage at increasing current density, the lower the associated SED. Under operation, the electrolyzer cells are exposed to a number of degradation phenomena that deteriorate the cell performance over time. This results in an increase of the cell voltage with progressing operating hours, yielding a decreasing performance and an increasing SED over time. Thus, the lower the cell degradation, the lower the SED of the stack over its complete life cycle. Note, that the assumed annual full load operation hours progressively decrease in the future. This is due to the anticipated increasing share of fluctuating renewable energy sources in the future electricity grid [1]. For a comprehensive discussion of the PEMWE cell operation including a detailed analysis of all performance parameters and degradation phenomena refer to the given literature. Table 1 Operational KPIs of the proton exchange water electrolysis (PEMWE) stack Parameter Unit 2025 2030 2050 Reference Array scaling MW 20 20 20 [2] Stack scaling MW 2.5 5 10 [3]/ [4] Current density A∙cm-2 2 3 5 [4]/[5] /[1] Cell voltage beginning of life V 1.8 1.8 1.7 [4]/[6]/[7] Cell degradation mV∙h-1 0.0048 0.0023 0.002 [5] Cell voltage EoL V 2.18 1.98 1.96 Calculation Mean cell voltage V 1.99 1.89 1.88 Calculation Stack operating pressure MPa 3 3 3 [1] Active cell area cm2 1500 3000 10’000 [4]/[1]/[3] Active stack area m2 69.45 98.1 118 Calculation Cells per stack 463 309 112 Calculation Stack lifetime h 80’000 80’000 80’000 [5] Full load operation hours per year h 8’000 4’035 3’325 [1]/Assumption An electrolysis stack represents the interconnection of separate cells whereas each cell consists of a number of sub components. Figure 1 shows the exploded view of a PEMWE cell. Core of a PEMWE cell is a catalyst coated membrane (CCM) that divides the cell into an anode and a cathode compartment. The ultrapure reaction water is supplied on the anode side where it is split into oxygen and hydrogen protons. The hydrogen protons migrate through the membrane and recombine to molecular hydrogen on the cathode Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 3 side. The catalysts support the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on the anode and cathode side, respectively. The CCM is sandwiched between porous transport layers (PTL) that promote the transport of reactants and products to and from the CCM. The individual cells are separated from each other by bipolar plates (BPP) and sealed with a gasket. A single stack comprises up to several hundred cells and is completed with a current collector and an end plate on each side. Individual PEMWE stacks are interconnected with a busbar in order to form an array. Table 2 gives an overview over the required materials, dimensions and respective amounts for the manufacturing of a state-of-the-art stack and technologically developed stacks in 2030 and 2050. Principal technological developments are the scale up of the active cell area along with significant material reductions, especially for the critical catalyst and coating materials. Figure 1 Exploded view of a PEMWE stack [1] Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 4 Table 2 Construction KPIs of the proton exchange water electrolysis (PEMWE) stack Parameter Unit 2025 2030 2050 Reference Active cell area cm2 1500 3000 10’000 [4]/[1]/[3] Membrane material Nafion™ N117 Nafion™ 80 𝜇m Nafion™ N112 [8]/[9] Cathode catalyst Platinum supported on Vulcan XC72 carbon black (40 wt % Pt/C) [10] Cathode catalyst loading (Pt + C) mg∙cm2 0.2 0.05 0.05 [11]/ [9]/[12] Anode catalyst Rutile iridium oxide (IrO2) on titanium dioxide (TiO2) support (weight ratio 3 IrO2/TiO2) [6]/[13] Anode catalyst loading (Ir + TiO2) mg∙cm2 2 0.5 0.1 [14]/[5] Porous transport layer material anode Titanium, 30 % porosity Titanium, 50 % porosity [6]/[15]/[16] Porous transport layer thickness anode mm 1 1 0.7 [6]/[15]/[16] Porous transport layer coating anode 0.1 mg/cm2 iridium 0.1 mg/cm2 iridium None [6]/[15]/[16] Porous transport layer material cathode Carbon paper [11] Porous transport layer thickness cathode μm 280 [11] Bipolar plate material Titanium [17] Bipolar plate thickness mm 2.5 1 0.1 [17]/[4] Bipolar plate coating material anode side Platinum [18]/[11] Bipolar plate coating amount mg∙cm2 0.04 0.04 0.02 [11] Gasket material EPDM [1] Gasket thickness mm 1 1 0.7 [1] Current collector material Copper [19] Current collector thickness mm 5 Assumption End plates material Stainless steel [1] End plates thickness mm 30 Assumption 1.2 Technological development of Alkaline Water Electrolysis As introduced for the PEMWE, the discussion of the AWE stacks follows the division of KPIs into operational and constructional. The operation of the AWE is fundamentally governed by the same physical and chemical principles and relations as the PEMWE. However, due to differences in the working principle of the technology and its implementation there are significant differences in the KPIs. For example, the AWE requires a potassium hydroxide (KOH) electrolyte to establish an appropriate environment for the reaction to propagate. Table 3 gives an overview over the operational KPIs for the AWE for a state-of-the-art stack in 2025 as well the respective anticipated developments for 2030 and 2050. For a comprehensive discussion of the AWE technology including a detailed analysis of all performance parameters and degradation phenomena refer to the given literature. Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 5 Table 3 Operational KPIs of the alkaline water electrolysis (AWE) stack Parameter Unit 2025 2030 2050 Reference Array scaling MW 20 20 20 [4] Stack scaling MW 2.5 10 10 [4]/[3] Cell voltage beginning of life V 1.8 1.7 1.7 [4]/ [3], [20] Cell degradation mV∙h-1 0.0032 0.0023 0.0021 [21] Cell voltage EoL V 1.99 1.88 1.87 Calculation Mean cell voltage V 1.90 1.79 1.78 Calculation Current density A∙cm-2 0.6 1 2 [4]/ [3] Stack operating pressure MPa 0.1 0.5 3 [4]/[9]/[3] Active cell area cm2 20’000 20’000 20’000 [4]/Assumption Active stack area m2 232 296 296 Calculation Cells per stack 116 148 148 Calculation Stack lifetime h 60’000 80’000 80’000 [3]/[21] Full load operation hours per year h 8’000 4’035 3’325 [1]/Assumption An AWE stack exhibits a similar setup as the PEMWE though materials and dimensions differ. An exploded view of an AWE cell is given in Figure 2. Significant improvements have been made to AWE technology over the decades. In this study the zero-gap setup is analyzed. Similarly to the PEMWE, the AWE stack comprises multiple cells. Central component of the AWE cell is the diaphragm, a membrane that separates the anode and cathode electrodes. A KOH and water solution is supplied to both sides. The reduction of water occurs at the cathode and OHions permeate through the diaphragm and recombine to molecular oxygen on the anode. A catalyst supports the reduction reaction and formation of hydrogen at the cathode. The electrodes are sandwiched between separator meshes that promote the steady flow of reactants and products from and to the electrodes. Separate cells are interconnected by a BPP and mounted in a cell frame that is sealed with gaskets. The AWE stack is completed by current collectors and end plates that are electrically insulated by a separator plate. The electric connection of the cells is realized with a busbar, that runs along the stack. Table 4 gives an overview over the required materials, dimensions and respective amounts for the manufacturing of a state-of-the-art stack and technologically developed stacks in 2030 and 2050. Principal technological developments are the substitution of the catalyst material along with significant material reductions. Note that according to the literature, the anticipated future cell area of AWE cells is expected to increase significantly [3]. Based on expert interviews however, in this study it is assumed that the active cell area remains constant in the future due to logistics and transportation constraints of AWE stacks with a larger active cell area. While it is technologically possible to increase the cell area significantly, the implementation is not regarded as very likely due to transport constraints with heavy duty trucks. Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 6 Figure 2 Exploded view of an AWE stack [19] Table 4 Construction KPIs of the alkaline water electrolysis (AWE) stack/ Input data for the LCI of the AWE stack construction Parameter Unit 2025 2030 2050 Reference Active cell area cm2 20’000 20’000 20’000 [4]/Assumption Membrane material Zirfon, 85 wt% ZrO2 15 wt% polysulfone (PSU) [3] Cathode electrode material Woven nickel mesh [4] Cathode electrode thickness mm 0.3 0.228 0.228 [22]/[9] Cathode electrode porosity 0.5 0.73 0.73 [22]/[9] Cathode electrode catalyst material nickel sulfide (8515 wt%) Raney-Nickel [22]/[9] Cathode electrode catalyst thickness μm 30 30 30 [22] Anode electrode material Expanded nickel sheet [4] Anode electrode thickness mm 0.3 0.228 0.228 [22]/[9] Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 7 Anode electrode porosity 0.5 0.73 0.73 [22]/[9] Separator mesh material Nickel mesh [3], [4] Separator mesh porosity 0.85 0.9 0.96 [23] Separator mesh thickness mm 5 3 1.2 [23] Bipolar plate material Stainless steel [22]/[4] Bipolar plate thickness mm 0.2 0.2 0.2 [9] Bipolar plate coating material Nickel [9] Bipolar plate coating thickness μm 8 8 8 [19] Gasket material EPDM [19] Gasket thickness mm 5 5 5 Assumption Frame material stainless steel PSU + 30 % Glass Fiber [9] Frame thickness mm 20 20 20 Assumption Frame width mm 11.55 7.12 3.35 Calculation Current collector material Copper Assumption Current collector thickness mm 6 6 6 Assumption Separator plate material HDPE Assumption Separator plate area m2 2.31 2.31 2.31 Calculation Separator plate thickness mm 20 20 20 Assumption End plate material Stainless steel Assumption End plate area m2 2.31 2.31 2.31 Calculation End plate thickness mm 30 30 30 Assumption 2. Process Model In the following section the detailed flow sheets of all plant cases for both PEM (PEMWE) and alkaline water electrolysis (AWE) technologies and the respective results of the process models are given. On array level, the detailed stream parameters of each component are given exemplarily for one array as all stack arrays are assumed to be identical. In order to determine the flow parameters of the centralized components, the inputs and outputs from the array are multiplied with the according number of 50 arrays. Likewise, the input and output streams from the stacks on array level are solely given for one stack, as all stacks are assumed to be identical. For the calculation of the stream parameters on array level, the stack parameters are multiplied with the respective stack number of each plant case. For the calculation of the electrical energy demand for the stacks, the following procedure was implemented: 1. Calculation of electricity input for one stack based on mass and energy balances 2. Calculation of electricity input for one rectifier (assumption: rectifier scaling 5 MW) with electric efficiency of 98 % [24] 3. Calculation of electricity input of medium voltage transformer on array level (assumption: array scaling 20 MW, thus 8, 4, 2 stacks in 2025, 2030 and 2050 respectively) with electric efficiency of 98 % [25] 4. Calculation of electricity input of high voltage transformer on system level (assumption: system scaling 1 GW, thus 50 arrays) Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 8 Transformers are required to handle the apparent power of the system. For the determination of the apparent power of the overall system, a power factor of 0.9 for 2025 and 2030 was assumed and 0.99 for 2050 [26]. 2.1 PEM Water Electrolysis The process model for the PEMWE was implemented according to the procedure discussed in [1]. 2.1.1 2025 Figure 3 gives the detailed flowsheet of the state-of-the-art plant in 2025. The mass flow rates and the electric power flow rates of the electrochemical process model are given in Table 5 and Table 10, respectively. Subsequently, the calculation of the material demand for each system component is implemented based on the given mass and energy streams. Figure 3 Detailed process flow diagram of the state-of-the-art (2025) 1 GW PEMWE plant Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 9 Table 5 Mass flow rates of the state-of-the-art (2025) 1 GW PEMWE plant (for the stream numbers refer to Figure 3) Stream number Pressure [barabs] Temperature [°C] Total mass flow [kg/s] Mass flow water liquid [kg/s] Mass flow water vapor [kg/s] Mass flow oxygen [kg/s] Mass flow hydrogen [kg/s] 1 1 25 52.5 52.5 0 0 0 2 30 25 52.5 52.5 0 0 0 3 30 25 1.05 1.05 0 0 0 4 30 65 373.2 373.2 0 0 0 5 32 65 373.2 373.2 0 0 0 6 31 60 373.2 373.2 0 0 0 7 31 60 46.65 46.65 0 0 0 8 30 65 45.98 45.87 0.0005 0.11 0.0001 9 33 65 0.65 0.65 0.0009 0.001 0.014 10 33 65 5.31 5.18 0.007 0.009 0.114 11 32.5 25 5.31 5.18 0.007 0.009 0.114 12 32.5 25 0.13 0 0.008 0.009 0.114 13 32.5 25 5.18 0 0 0 0 14 32.5 25 6.5 0 0.4 0.45 5.7 15 31.5 135 6.5 0 0.9 0 5.6 16 31 25 6.5 0.85 0.05 0 5.6 17 31 25 5.65 0 0.05 0 5.6 18 30 25 5.6 0 0 0 5.6 19 30 65 373.04 372.13 0.004 0.91 0.001 20 30 65 0.92 0 0.004 0.91 0.001 21 32.5 25 0.92 0 0 0.91 0.001 22 30 25 45.86 0 0.19 45.5 0.058 Table 6 Electric power of the state-of-the-art (2025) 1 GW PEMWE plant (for the stream numbers refer to Figure 3) Energy stream number Power [MW] E1 1175.91 E2 23.5 E3 5.75 E4 2.82 E5 0.08 E6 9.37 E7 2.03 E8 0.8 E9 0.8 Etot 1190.61 Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 16 Table 14 Electric power of the state-of-the-art (2025) 1 GW AWE plant (for the stream numbers refer to Figure 6) Energy stream number Power [MW] E1 1121.45 E2 21.98 E3 5.39 E4 2.64 E5 8.71 E6 0.01 E7 2.03 E8 0.33 E9 0.44 E10 22.88 E11 21.42 Etot 1177.27 2.2.2 2030 Figure 7 gives the detailed flowsheet of the future AWE plant case in 2030. The mass flow rates and the electric power flow rates of the electrochemical process model are given in Table 15 and Table 16, respectively. The implemented optimistic and pessimistic performance scenarios solely affect the electricity demand for the stacks and hence, for the arrays. The respective electricity demands for the optimistic and pessimistic performance scenarios for 2030 are given in Table 17. Figure 7 Detailed process flow diagram of the 2030 1 GW AWE plant Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 17 Table 15 Mass flow rates of the 2030 1 GW AWE plant (for the stream numbers refer to Figure 7) Stream number Temperature [°C] Pressure [barabs] Total mass flow [kg/s] Mass flow water liquid [kg/s] Mass flow oxygen [kg/s] Mass flow hydrog en [kg/s] Mass flow KOH [kg/s] 1 25 1.01 55.84 55.84 0 0 0 2 25 5.5 55.84 55.84 0 0 0 3 25 5.5 1.12 1.12 0 0 0 4 25 5 1.30 1.30 0 0 0 5 94 5 88.72 62.44 0 0 26.28 6 100.33 6.5 176.34 123.77 0 0 52.56 7 90 6 176.34 123.77 0 0 52.56 8 90 6 44.08 30.94 0 0 13.14 9 95 6 21.94 15.33 0.001 0.03 6.57 10 95 6 87.74 61.33 0.005 0.12 26.28 11 95 5 0.32 0.19 0.005 0.12 0 12 95 5 87.42 61.14 0 0 26.28 13 25 5 0.13 0.01 0.005 0.12 0 14 25 5 0.13 0.01 0.005 0.12 0 15 25 5 6.72 0.35 0.25 6.12 0 16 295.78 31 6.72 0.35 0.25 6.12 0 17 230 30.5 6.72 0.35 0.25 6.12 0 18 271.24 30.5 6.72 0.63 0 6.09 0 19 25 30 6.72 0.63 0 6.09 0 20 25 30 6.15 0.06 0 6.09 0 21 25 30 6.09 0 0 6.09 0 22 95 6 22.15 15.33 0.25 0.0003 6.57 23 95 6 88.60 61.33 0.98 0.0012 26.28 24 95 5 1.08 0.10 0.98 0.0012 0 25 95 5 87.52 61.23 0 0 26.28 26 25 5 1.08 0.10 0.98 0.0012 0 27 25 5 0.98 0.00 0.98 0.0012 0 28 25 5 0.09 0.09 0 0 0 29 25 5 49.08 0.18 48.84 0.06 0 Table 16 Electric power of the 2030 1 GW AWE plant (for the stream numbers refer to Figure 7) Energy stream number Power [MW] E1 1127.29 E2 22.09 E3 5.41 E4 5.31 E5 8.48 E6 0.21 E7 2.16 E8 0.21 E9 0.29 E10 24.39 Etot 1163.03 Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 18 Table 17 Electricity demand for the 2030 AWE stack operation in the pessimistic and optimistic scenario cases Component Pessimistic Base Optimistic Stack input [MW] 6.87 5.31 4.86 Inverter input [MW] 7.01 5.41 4.95 Array transformer input [MW] 28.60 22.09 20.22 System transformer input [MW] 1.459.32 1.127.29 1.031.67 Specific energy demand H2 production [kWh/kg H2] 66.54 51.40 47.04 2.2.3 2050 Figure 8 gives the detailed flowsheet of the future AWE plant case in 2050. The mass flow rates and the electric power flow rates of the electrochemical process model are given in Table 18 and Table 19, respectively. The implemented optimistic and pessimistic performance scenarios solely affect the electricity demand for the stacks and hence, for the arrays. The respective electricity demands for the optimistic and pessimistic performance scenarios for 2050 are given in Table 20. Figure 8 Detailed process flow diagram of the 2050 1 GW AWE plant Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 19 Table 18 Mass flow rates of the 2050 1 GW AWE plant (for the stream numbers refer to Figure 8) Stream number Temperature [°C] Pressure [barabs] Total mass flow [kg/s] Mass flow water liquid [kg/s] Mass flow oxygen [kg/s] Mass flow hydrog en [kg/s] Mass flow KOH [kg/s] 1 25.00 1.01 55.84 55.84 0 0 0 2 25.24 30.50 55.84 55.84 0 0 0 3 25.24 30.50 1.12 1.12 0 0 0 4 24.91 30 1.16 1.16 0 0 0 5 104.3 30 86.47 60.87 0 0 25.60 6 110.34 30 171.86 120.62 0 0 51.21 7 110.54 31.5 171.86 120.62 0 0 51.21 8 100 31 171.86 120.62 0 0 51.21 9 105.44 31.00 42.74 29.88 0.003 0.06 12.80 10 105.44 31.00 85.49 59.75 0.005 0.12 25.60 11 105.44 30.00 0.17 0.04 0.005 0.12 0 12 105.44 30.00 85.32 59.71 0 0 25.60 13 25.00 30.00 0.17 0.04 0.005 0.12 0 14 24.91 30.00 0.13 0.00 0.005 0.12 0 15 25.01 30.00 6.43 0.06 0.25 6.12 0 16 230.00 30.00 6.43 0.06 0.25 6.12 0 17 271.91 30.00 6.43 0.34 0 6.09 0 18 67.29 30.00 6.43 0.34 0 6.09 0 19 24.84 30.00 6.43 0.34 0 6.09 0 20 24.84 30.00 6.15 0.06 0 6.09 0 21 24.84 30.00 6.09 0.00 0 6.09 0 22 105.44 31.00 43.18 29.88 0.50 0.001 12.80 23 105.44 31.00 86.36 59.75 1.00 0.001 25.60 24 105.44 30.00 1.00 0.02 0.98 0.001 0 25 105.44 30.00 85.36 59.73 0.03 0 25.60 26 25.00 30.00 1.00 0.02 0.98 0.001 0 27 25.00 30.00 0.98 0.00 0.98 0.001 0 28 25.00 30.00 0.02 0.02 0 0 0 29 25.00 30.00 48.92 0.03 48.83 0.06 0 Table 19 Electric power of the 2050 1 GW AWE plant (for the stream numbers refer to Figure 8) Energy stream number Power [MW] E1 1121.98 E2 21.99 E3 10.78 E4 10.56 E5 7.83 E6 0.03 E7 2.03 E8 0.22 E9 0.29 Etot 1132.38 Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 20 Table 20 Electricity demand for the 2050 AWE stack operation in the pessimistic and optimistic scenario cases Component Pessimistic Base Optimistic Stack input [MW] 12.55 10.56 9.71 Inverter input [MW] 12.81 10.78 9.91 Array transformer input [MW] 26.13 21.99 20.22 System transformer input [MW] 1333.42 1121.98 1031.67 Specific energy demand H2 production [kWh/kg H2] 60.80 51.16 47.04 3. Life cycle inventory for the construction of the water electrolysis plants In this section, the material demand for the construction of the plants for both technologies in every plant case is presented. 3.1 PEM Water Electrolysis Table 21 gives the material demand for the construction of every PEMWE plant case. A detailed exploded depiction of a state-of-the-art PEMWE stack is given in Figure 1. No fundamental technological developments for the overall stack design are assumed until 2050. The general layout and design of the stack is anticipated to remain the same. The most substantial technological developments for the PEMWE stacks and cells stem from the employed materials and their respective amount. For a detailed discussion and modeling of the manufacturing of a PEMWE stack including a detailed calculation of the material demand for all stack components refer to [1]. Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 21 Table 21 Material demand for the construction of the 1 GW PEMWE plants for every plant case. Note that the material demand for components that were modelled with ready-to-use datasets from ecoinvent (e.g. housing, motors, pumps, data cable) is not considered in this table Material Components Unit 2025 2030 2050 Titanium Stack t 797.36 249.15 22.59 Carbon Paper Stack t 7.00 4.67 1.41 Nafion Stack t 24.64 6.01 1.36 Platinum Stack t 0.15 0.04 0.009 Activated Carbon Stack t 0.19 0.03 0.01 Iridium Stack t 1.97 0.36 0.02 Titanium Dioxide Stack t 0.85 0.11 0.006 Rubber Stack. Heat Exchanger t 66.44 32.70 8.76 Copper Stack. Transformer. Rectifier t 433.82 427.78 416.83 Stainless Steel Stack. Heat Exchanger. Gas Water Separator t 3527.97 3465.38 3404.97 Carbon Steel Transformer. Heat Exchanger t 1581.55 1574.68 1562.65 Copper Stack. Busbar. Transformer. Rectifier t 433.82 427.78 416.83 Polyvinyl Chloride (PVC) Cooling Tower. Rectifier t 28.20 26.64 25.07 Fiber Reinforced Plastic Cooling Tower t 20.28 18.44 16.59 Concrete Cooling Tower m3 132.65 120.59 108.53 Transformer Oil Transformer t 702.13 694.03 679.86 Insulation Material Transformer t 16.99 16.15 14.69 Wood Transformer t 86.10 84.17 80.80 Porcelain Transformer t 6.53 6.21 5.65 Paint Transformer t 5.23 4.97 4.52 Aluminum Power Cable. Rectifier t 112.65 112.65 112.65 Polyvinyl Fluoride Power Cable t 44.54 44.54 44.54 3.2 Alkaline Water Electrolysis Table 22 gives the material demand for the construction of every AWE plant case. A detailed exploded depiction of a state-of-the-art AWE stack is given in Figure 2. No fundamental technological developments for the overall stack design are assumed until 2050. The general layout and design of the stack is anticipated to remain the same. The most substantial technological developments for the AWE stacks and cells stem from the employed materials and their respective amount. For a detailed discussion and modeling of the manufacturing of a AWE stack including a detailed calculation of the material demand for all stack components refer to [19]. Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 22 Table 22 Material demand for the construction of the AWE plants for every plant case. Note that the material demand for components that were modelled with ready-to-use datasets from ecoinvent (e.g. housing, motors, pumps, data cable) is not considered in this table Material Components Unit 2025 2030 2050 Carbon Steel Transformer, Heat Exchanger t 1658.24 1647.62 1639.95 Stainless Steel Stack, Transformer, Piping, Heat Exchanger, Gas Water Separator t 6915.76 4088.06 3650.18 Nickel Stack, Heat Exchanger t 4518.15 790.24 129.58 Nickelsulfide Stack t 47.27 0.00 0.00 Raney Nickel Stack t 0.00 26.64 13.32 Copper Stack, Transformer, Rectifier t 799.47 514.17 433.17 Rubber Stack, Heat Exchanger t 65.98 28.06 14.73 Polysulfone Stack t 0.00 58.79 13.84 Fiber Glass Stack t 0.00 37.95 8.93 HDPE Stack, KOH Separators t 544.02 114.89 296.25 Zirfon Stack t 160.78 30.09 3.42 Polyvinyl Chloride (PVC) Cooling Tower, Rectifier t 31.38 28.25 28.25 Fiber Reinforced Plastic Cooling Tower t 11.06 7.38 7.38 Concrete Cooling Tower m3 72.35 48.24 48.24 Transformer Oil Transformer t 694.50 695.32 680.30 Insulation Material, Transformer t 16.20 16.28 14.73 Wood Transformer t 84.28 84.48 80.90 Porcelain Transformer t 6.23 6.26 5.67 Paint Transformer t 4.98 5.01 4.53 Aluminum Power Cable, Rectifier t 112.65 112.65 112.65 Polyvinyl Fluoride Power Cable t 44.54 44.54 44.54 Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 23 4. Supplementary Results In this section the results for the impact categories acidification potential (Figure 9), eutrophication potential fresh water (Figure 10), eutrophication potential marine (Figure 11), eutrophication potential terrestrial (Figure 12), land use (Figure 13), energetic resources: non-renewable (Figure 14), ozone depletion potential (Figure 16), and water use (Figure 17) are given for the life cycle of every plant case for both technologies in all analyzed background scenarios. Figure 9 Acidification Potential of the production of 1 kg hydrogen from PEMWE and AWE of all analyzed foreground and background scenarios. Lefthand side shows the propagation of the absolute Acidification Potential until 2050. The impacts for the NDC and Peak Budget 1150 background scenarios are depicted transparent for better legibility. Righthand side shows the relative share of the life cycle phases in the Base background scenario. The given values refer to the share of the plant operation phase Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 24 Figure 10 Eutrophication Potential Fresh Water of the production of 1 kg hydrogen from PEMWE and AWE of all analyzed foreground and background scenarios. Lefthand side shows the propagation of the absolute Eutrophication Potential Fresh Water until 2050. The impacts for the NDC and Peak Budget 1150 background scenarios are depicted transparent for better legibility. Righthand side shows the relative share of the life cycle phases in the Base background scenario. The given values refer to the share of the plant operation phase Figure 11 Eutrophication Potential Marine of the production of 1 kg hydrogen from PEMWE and AWE of all analyzed foreground and background scenarios. Lefthand side shows the propagation of the absolute Eutrophication Potential Marine until 2050. The impacts for the NDC and Peak Budget 1150 background scenarios are depicted transparent for better legibility. Righthand side shows the relative share of the life cycle phases in the Base background scenario. The given values refer to the share of the plant operation phase Supporting Material for: Prospective Life Cycle Assessment of Large-Scale Low Temperature Water Electrolysis Plants 25 Figure 12 Eutrophication Potential Terrestrial of the production of 1 kg hydrogen from PEMWE and AWE of all analyzed foreground and background scenarios. Lefthand side shows the propagation of the absolute Eutrophication Potential Terrestrial until 2050. The impacts for the NDC and Peak Budget 1150 background scenarios are depicted transparent for better legibility. Righthand side shows the relative share of the life cycle phases in the Base background scenario. The given values refer to the share of the plant operation phase Figure 13 Land Use of the production of 1 kg hydrogen from PEMWE and AWE of all analyzed foreground and background scenarios. Lefthand side shows the propagation of the absolute Land Use until 2050. The impacts for the NDC and Peak Budget 1150 background scenarios are depicted transparent for better legibility. Righthand side shows the relative share of the life cycle phases in the Base background scenario. The given values refer to the share of the plant operation phase