As the world is advancing towards a hydrogen society, solid oxide electrolysis cell systems are gaining increasing attention owing to their overwhelming thermodynamic advantages. Solid oxide electrolysis cell systems operate at high temperatures; therefore, they can achieve a substantially high energy conversion efficiency, which is critical in determining the techno-economic feasibility of green hydrogen production. However, one key concern to be resolved prior to market deployment is maintaining high operating temperatures. In this study, the thermal aspects of currently verified solid oxide electrolysis cell systems are reviewed based on standardized criteria. First, the basic concept of the thermal integration of solid oxide electrolysis cell systems is introduced. Second, standardized thermodynamic indices are introduced to enable consistent performance evaluation and capture thermal characteristics from a system-level perspective. Particularly, this review presents complete information on the system efficiency, specific energy consumption, specific thermal energy consumption, and system thermoneutral voltages. Third, based on the aforementioned discussion, the recently verified solid oxide electrolysis cell systems are reviewed, focusing on their thermal aspects. The analysis on ten verified SOEC systems from different institutions suggest that system thermal integration and operating conditions must be designed considering external thermal energy consumption. Furthermore, several future milestones in solid oxide electrolysis cell system verification are discussed. Currently, five institutions are developing kilowatts to megawatt scale SOEC systems and most of them are considering ironworks and nuclear power plants as external heat sources. This review is expected to shed light on the hitherto overlooked thermal aspect of solid oxide electrolysis cell systems and suggest a future direction for system design and demonstration.
Bibliographical noteFunding Information:
In 2020, FuelCell Energy teamed up with Idaho National Laboratory to deliver a 250 kW SOEC system integrated with the nuclear environment funded by the U.S. Department of Energy (U.S. Industry Opportunities for Advanced Nuclear Technology Development, within Pathway 2 - Advanced Reactor Development Projects) [80,84] . They aim to deliver 250 kW of SOEC system to the nuclear environment by 2022. Based on FuelCell Energy’s compact solid oxide architecture stack and INL’s system build-up experience, they aim to deploy modular 200 to 500 MW SOEC systems by 2026 and demonstrate the profits of nuclear hydrogen production technology [73,85] . One of their project objectives is to curb nuclear plant curtailment and to facilitate renewable energy build-up by showing the profitability of the SOEC system in terms of hydrogen production  . To deal with the case in which only an electrical connection to the nuclear plant is available, the system will also be equipped with an electrical steam generator. Currently, it is difficult to identify the detailed methods of integration; however, it will soon be out in the market once the preliminary results of the project are obtained.
This study was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2019R1C1C1005152 ) and the Ministry of Trade, Industry and Energy (MOTIE), South Korea and Korea Institute for Advancement of Technology (KIAT), South Korea through the International Cooperative R&D program ( P0021202 ).
© 2022 Elsevier Ltd
All Science Journal Classification (ASJC) codes
- Building and Construction
- Mechanical Engineering
- Management, Monitoring, Policy and Law