LCS-FY2019-PP-08
SOFC Systems (Vol. 7):
Technology and Cost Assessments of High-Temperature Steam Electrolysis
Summary
Hydrogen production/storage costs with steam electrolysis were investigated through the techno-economic analysis of solid oxide electrolysis cells (SOEC), assuming the use of excess electricity produced by renewable energy sources in future. Based on the information about the production costs of solid oxide fuel cells (SOFC), SOEC was compared to Lithium ion batteries (LIB) in terms of energy storage cost.
For the present system costs of SOEC and LIB, the advantage of hydrogen storage using a reversible SOFC/SOEC system in comparison with the charge/discharge cycle of LIB was demonstrated under the assumption of a hydrogen storage duration longer than approximately 4 days using an electricity cost equivalent to the grid cost, 12 JPY/kWh. For the system costs of future and advanced cases, the advantages of the reversible SOFC/SOEC system were also demonstrated, assuming hydrogen storage durations of approximately 2 days and 1 day. Furthermore, the requirements to achieve the Japanese government’s cost target of 30 JPY/Nm3-H2 for hydrogen production were investigated. Under the conditions of a 24 h duration for hydrogen storage, an electricity cost of 5 JPY/kWh, an operation rate of 60% and a SOEC system cost of 88 JPY/W, the result suggests that the target cost can be achieved.
Through the investigations stated above, the following issues are identified as future challenges: development of SOEC module which can follow the fluctuations of renewable energies; prolonging the lifetime of SOEC modules and downsizing them; cost reduction of auxiliaries such as a compressor and a hydrogen storage cylinder, downsizing of a heat exchanger, and development of proton-conducting fuel cells as a new technology. Also, the following issues are important: utilization and market development of hydrogen storage corresponding to the time constant of the fluctuation of renewable energies, i.e., time, day, week, month, and the development of small- and middle-class SOEC systems.
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