Economic Analysis of the Reference Design for a Nuclear-Driven High-Temperature-Electrolysis Hydrogen Production Plant

Abstract

A reference design for a commercial-scale high-temperature electrolysis (HTE) plant for hydrogen production was developed to provide a basis for comparing the HTE concept with other hydrogen production concepts. The reference plant design is driven by a high-temperature helium-cooled reactor coupled to a direct Brayton power cycle. The reference design reactor power is 600 MWt, with a primary system pressure of 7.0 MPa, and reactor inlet and outlet fluid temperatures of 540°C and 900°C, respectively. The electrolysis unit used to produce hydrogen consists of 4,009,177 cells with a per-cell active area of 225 cm 2 . A nominal cell area-specific resistance, ASR, value of 0.4 Ohm·cm 2 with a current density of 0.25 A/cm 2 was used, and isothermal boundary conditions were assumed. The optimized design for the reference hydrogen production plant operates at a system pressure of 5.0 MPa, and utilizes an air-sweep system to remove the excess oxygen that is evolved on the anode side of the electrolyzer. The inlet air for the air-sweep system is compressed to the system operating pressure of 5.0 MPa in a four-stage compressor with intercooling. The alternating-current to direct-current conversion efficiency is assumed to be 96%. The overall system thermal-to-hydrogen production efficiency (based on the low heating value of the produced hydrogen) is 47.12% at a hydrogen production rate of 2.356 kg/s.An economic analysis of the plant was also performed using the H2A Analysis Methodology developed by the Department of Energy (DOE) Hydrogen Program. The results of the economic analysis demonstrated that the HTE hydrogen production plant driven by a high-temperature helium-cooled nuclear power plant can deliver hydrogen at a competitive cost using realistic financial and cost estimating assumptions. A plant-gate cost of $3.23 per kg of hydrogen produced was calculated assuming an internal rate of return of 10%. Approximately 73% of this cost ($2.36/kg) is the result of capital costs associated with the construction of the combined nuclear plant and hydrogen production facility. Operation and maintenance costs represent about 18% of the total cost ($0.57/kg). Variable costs (including the cost of nuclear fuel) contribute about 8.7% ($0.28/kg) to the total cost of hydrogen production, and decommissioning and raw material costs make up the remaining fractional cost.iii

A detailed techno-economic analysis of heat integration in high temperature electrolysis for efficient hydrogen production

“…Similar values are also stated by others [8,16,44] for large-scale industrial manufacturing. Based on this, 1500 V/m 2 are assumed as reference value.…”

“…They include equipment costs (without installation) for feed water preparation, boiler, piping, steam turbine, generator, condenser and cooling. The lifetime of the SOEC is assumed to be 3 years in the base case according to [8,16]. The degradation can be taken into consideration by an additional ohmic resistance [44] resulting in higher degradation at higher current densities.…”

“…Based on a report of Oh et al [40] concerning intermediate high-temperature heat exchanger for nuclear power plants, a lifetime of 13 years can be considered. The specific investment costs are estimated to be 900 V per kW transferred heat, which is conservative compared to other studies [16]. Based on these assumptions, the impact of heat integration on STPP and IHX costs as well as electricity revenue and specific cell area is presented in Fig.…”

“…An economic analysis based on this model resulted in hydrogen costs of $3.23/kg assuming specific costs of the SOEC module of $200/kW [16]. Other studies of hydrogen production by high temperature electrolysis coupled with very high temperature reactors (VHTR) have been published by Refs.…”

Using next generation nuclear power reactors for development of a techno‐economic model for hydrogen production

“…Proponents of the NuScale reactor (which has now received a design approval certificate from US Nuclear Regulatory Agency, in collaboration with Idaho National Laboratories) have claimed that it could meet the hydrogen needs of midsized, ammonia refinery plants. Next generation, high‐temperature reactors, such as gas‐cooled reactors, helium‐cooled reactors, and molten salt reactors, offer greater efficiency and higher temperature process heat that could be used to support hydrogen production …”