A novel interconnect design for thermal management of a commercial-scale planar solid oxide fuel cell stack

Abstract

Solid oxide fuel cell (SOFC) is a promising technology for stable power supply with high efficiency and high quality heat utilization, but it still faces the technical challenge of low long-term durability caused by thermal imbalance of its stack. An effective, novel thermal management method is urgently required for its market deployment. This study proposes a novel interconnect design for effective thermal management and elucidates the influence of its design variables on internal thermal conditions and heat transfer characteristics of a 1-kW planar SOFC stack. Three-dimensional thermo-fluid simulations are performed on the new stack design employing the novel interconnect and the conventional stack design for comparison. The new design is developed for the purpose of uniform in-plane (horizontal) temperature distribution by modifying the displacement of gas manifolds. At the repeating-unit scale, due to the reduced thermal resistance for horizontal heat transfer of the new stack, its in-plane temperature deviation decreases by 35-60 degrees C. At the stack scale with 30 unit-cells stacked vertically, the average temperature increases by 30 degrees C, and the vertical temperature difference decreases by 50 degrees C. Such thermal fields are the combined results of reduced gaseous convection and enhanced vertical solid-phase conduction through each repeating unit. In the new stack, the amount of heat transferred to the gas within each repeating unit is generally decreased, but is recuperated by increasing solid conduction through metallic interconnects. The relatively weakened gaseous heat transfer of the new design provides more thermal load at the lowest unit of the stack than the reference design, which promotes gas pre-heating prior to reaching the unit-cells and hence results in the elevated stack temperature. Such gas pre-heating also reduces the temperature difference in the vertical direction of the new design. The lower temperature differences both in horizontal and vertical directions enable the new stack to reduce its thermal imbalance and potentially to improve long-term durability.