Thermal management of solid oxide electrolysis cell systems: Integration principles, coupling with external heat sources and integration of heat storage technologies

For efficient and low-cost operation, Solid Oxide Electrolysis Cell (SOEC) systems require a well-designed heat integration architecture. In this work, SOEC thermal integration and thermal coupling with external heat source are discussed. SOEC systems strongly benefit from such a thermal coupling which can reduce the total electricity consumption by 17 %. A literature review of systems proposing such a thermal coupling is presented. Emphasis is placed on the nature and temperature of the heat sources and on the SOEC operation mode. The choice of an operation mode is influenced by considerations on the available heat input and on the system efficiency, production rate and durability. A focus is placed on the integration of heat storage systems in a SOEC architecture. The operation of SOEC systems must be continuous and stable to avoid temperature gradients and pressure differences. When coupling with a fluctuating heat source, heat storage offers a very interesting solution to match heat production and demand. When integrating with heat storage, SOEC architectures can be divided into three configurations. The first one includes a fluid loop, to which sensible storage systems are well adapted. In the second one, steam is directly generated from the heat input and steam storage systems such as latent storage or accumulators are preferred. Eventually, the third configuration corresponds to the storage of the heat produced in SOFC mode and its use in SOEC mode. Different heat storage systems are proposed in this case and lead to an improvement of 5 to 13 % in the system round-trip efficiency.