Electrolyzer Costing Method

Costing Method Parameters

The following parameters are constructed for the unit on the FlowsheetCostingBlock (e.g., m.fs.costing.electrolyzer) when applying the cost_electrolyzer costing method in the watertap_costing_package:

Description	Symbol	Parameter Name	Default Value	Units
Membrane replacement factor (fraction of membrane replaced/year)	\(f_{mem,\, replace}\)	factor_membrane_replacement	0.33	\(\text{yr}^{-1}\)
Membrane unit cost	\(C_{mem}\)	membrane_unit_cost	25	\(\text{USD}_{2012}\text{/m}^2\)
Anode unit cost	\(C_{anode}\)	anode_unit_cost	300	\(\text{USD}_{2005}\text{/m}^2\)
Cathode unit cost	\(C_{cathode}\)	cathode_unit_cost	600	\(\text{USD}_{2005}\text{/m}^2\)
Membrane, anode, and cathode fraction of total capital	\(f_{material}\)	fraction_material_cost	0.65	\(\text{dimensionless}\)

Costing Method Variables

The following variables are constructed on the unit block (e.g., m.fs.unit.costing) when applying the cost_electrolyzer costing method in the watertap_costing_package:

Description	Symbol	Variable Name	Index	Units
Total unit capital cost	\(C_{cap}\)	capital_cost	None	\(\text{USD}_{2020}\)
Fixed operating costs	\(C_{op}\)	fixed_operating_cost	None	\(\text{USD}_{2020}\text{/yr}\)
Membrane capital cost	\(C_{cap,\, mem}\)	membrane_cost	None	\(\text{USD}_{2020}\)
Anode capital cost	\(C_{cap,\, anode}\)	anode_cost	None	\(\text{USD}_{2020}\)
Cathode capital cost	\(C_{cap,\, cathode}\)	cathode_cost	None	\(\text{USD}_{2020}\)
Membrane replacement cost	\(C_{op,\, mem}\)	membrane_replacement_cost	None	\(\text{USD}_{2020}\text{/yr}\)

Capital Cost Calculations

Capital costs contribute to the majority of material costs for the anode, cathode, and membrane. Each material cost is calculated individually then summed and increased by the assumed fractional cost to estimate the total capital cost (O’Brien, 2005).

\[\begin{split}& C_{cap,\, mem} = C_{mem}A_{mem} \\\\ & C_{cap,\, anode} = C_{anode}A_{anode} \\\\ & C_{cap,\, cathode} = C_{cathode}A_{cathode} \\\\ & C_{cap} = \frac{C_{cap,\, mem}+C_{cap,\, anode}+C_{cap,\, cathode}}{f_{material}}\end{split}\]

Operating Cost Calculations

The electrolyzer costing model considers electricity as a variable operating costs and membrane replacement as a fixed operating costs. Electricity is costed using cost_flow function applied to the power variable on the unit model. Replacement costs for the anode and cathode are not currently considered in the costing function.

\[C_{op} = C_{op,\, mem} = f_{mem,\, replace}C_{mem}A_{mem}\]

Code Documentation

• watertap.costing.unit_models.electrolyzer

References

Bommaraju, T. V., & O’Brien, T. F. (2015). Brine electrolysis. Electrochemistry Encyclopedia. https://knowledge.electrochem.org/encycl/art-b01-brine.htm

Kent, J. A. (Ed.). (2007). Kent and Riegel’s Handbook of Industrial Chemistry and Biotechnology. Springer US. https://doi.org/10.1007/978-0-387-27843-8

Kumar, A., Du, F., & Lienhard, J. H. (2021). Caustic Soda Production, Energy Efficiency, and Electrolyzers. ACS Energy Letters, 6(10), 3563–3566. https://doi.org/10.1021/acsenergylett.1c01827

O’Brien, T., Bommaraju, T. V., & Hine, F. (2005). Handbook of chlor-alkali technology. Springer.

Phillips, R., Edwards, A., Rome, B., Jones, D. R., & Dunnill, C. W. (2017). Minimising the ohmic resistance of an alkaline electrolysis cell through effective cell design. International Journal of Hydrogen Energy, 42(38), 23986–23994. https://doi.org/10.1016/j.ijhydene.2017.07.184