Development of a Versatile and Reversible Multi-Stack Solid Oxide Cell System Towards Operation Strategies Optimization

Abstract

High Temperature Electrolysis based on Solid Oxide Cell technology is rapidly entering an industrialization phase, driven by promises of high efficiencies compared to the more market-ready solutions. To decrease the CAPEX and footprint related to module-based scale-up strategies, multiple stacks are typically assembled within the same thermal enclosure. As such, thermal phenomena become much more prominent in determining stack behavior compared to single stack test benches, and appropriate control strategies have to be developed. In this context, CEA LITEN has developed a new investigation tool (MURPHY) devoted to the operation of several Solid Oxide stacks within the same thermal enclosure. MURPHY enables stack operation in both the steam electrolysis (SOE) and the fuel cell (SOFC-H 2 ) modes. For the later, CH 4 , natural gas or NH 3 can be used as fuel, while additional gases are being considered. The one module system incorporates a compact Balance of Plant (BOP) located closely to the thermal enclosure. Its main functions are (i) to provide inlet process air by centrifugal blower towards higher efficiency, (ii) target high level of overall thermal integration and performances, (iii) actively preheat inlet gases independently of overall furnace temperature, (iv) recycle hot/cold fuel exhaust, and (v) control pressure levels distribution through multiple back-pressure valves. Overall, a high level of instrumentation was deployed to support modeling development and estimate accurate process efficiencies. MURPHY is currently compatible with four stacks of CEA standard base design [1]. Each comprising 25 cathode-supported cells each of 100 cm² active area, the corresponding maximum power range of the module is -16/4 kW DC [2], [3]. Nevertheless, the Hot Box has some capacity to adapt to different stack geometries and partner’s need. Finally, the MURPHY system is connected to the Multistack platform [4] for supply and venting of gases produced. This report details system architecture down to component level. It also puts forward preliminary experimental results related to stack operation in an environment controlled by thermal phenomena. Performance and efficiency curves obtained under parametric variations of operating conditions (Temperature, flowrates) are reported for both SOE and SOFC-H 2 modes. A special attention is given to heat performance of the overall system and its components. In this view, flow parameters (composition, temperature, pressure) at several locations over the reactant circuitries are provided. [1] G. Cubizolles, J. Mougin, S. Di Iorio, P. Hanoux, and S. Pylypko, “Stack Optimization and Testing for its Integration in a rSOC-Based Renewable Energy Storage System,” ECS Trans. , vol. 103, no. 1, pp. 351–361, Jul. 2021, doi: 10.1149/10301.0351ecst. [2] J. Aicart, S. Di Iorio, M. Petitjean, P. Giroud, G. Palcoux, and J. Mougin, “Transition Cycles during Operation of a Reversible Solid Oxide Electrolyzer/Fuel Cell (rSOC) System,” Fuel Cells , vol. 19, no. 4, pp. 381–388, May 2019, doi: 10.1002/fuce.201800183. [3] J. Aicart et al. , “Benchmark Study of Performances and Durability between Different Stack Technologies for High Temperature Electrolysis,” in 15th European SOFC & SOE Forum , Lucerne, Switzerland, May 2022, vol. A0804, pp. 138–149. [4] J. Aicart et al. , “Performance evaluation of a 4-stack solid oxide module in electrolysis mode,” Int. J. Hydrog. Energy , vol. 47, no. 6, pp. 3568–3579, Jan. 2022, doi: 10.1016/j.ijhydene.2021.11.056. Figure 1