Cost analysis of alternative large-scale high-temperature solid oxide electrolysis hydrogen production facilities

We extend our past cost analysis of gigawatt-scale solid oxide electrolysis (SOE) facilities that produce high purity hydrogen gas from water by estimating construction and operating costs for three new alternative design cases: (1) offsite feed steam generation; (2) near-atmospheric pressure (NAP) stack; and (3) onsite electric boiler feed steam generation. Pressure effects on hydrogen electrode-(cathode-)supported SOE cell (SOEC) stack performance are estimated to determine facility-wide stack capital costs for achieving a fixed H₂ production at different pressures. Capital costs for modular balance of plant (BOP) process equipment are estimated for each new design case using our past equipment sizing, design, and cost data and scaling relationships. We update BOP equipment sizing and design for the NAP case using Aspen®. Vendor quotes for electric boilers are used to estimate costs for electric boiler design cases. Factory and onsite assembly and installation costs for SOEC stacks and BOP equipment are calculated using our past first-principles approach. First-of-a-kind (FOAK) and N^th-of-a-kind (NOAK) production maturity costs are estimated for all cases. Use of NAP stacks offers the lowest facility total capital cost (TCC, ∼23% lower than base) while use of small electric boilers requires the highest TCC (∼3% higher than base). H₂ production costs decrease from the base of ∼$2.17/kgH₂ to ∼$1.92/kgH₂ for 1 GW_e DC_SIP facilities utilizing NAP stacks supplied by offsites steam situated in large modules and blocks for $0.030/kWh_e and $0.009/kWh_t electricity and heat prices, respectively. We report all costs in 2021 US dollars.