Advanced thermal management for oxygen pump assisted solar thermochemical reactor for fuel production

High-performance thermochemical cycles for fuel production require an energy-intensive reduction step due to the stringent conditions of high temperature and low oxygen partial pressure. An integrated high-temperature electrochemical oxygen pump (EOP) can enable effective in-situ oxygen removal, offering flexibility in tuning the oxygen environment with low energy consumption. However, thermal failure induced by extreme high reduction temperature, typically > 1500 °C, poses a challenge to the stability of the oxygen pump. This study proposes a thermal management strategy for oxygen pump integration by actively cooling the pump to prevent overheating. The performance of the reactor was evaluated using both numerical simulation and experimental methods. The thermochemical performance of ceria and the electrochemical performance of the EOP were assessed with and without active cooling. Results indicated that the ceria height (Hceria) was the key factor influencing reactor performance, more so than the gap distance (Dgap), temperature difference (Tdif), or mass flow rate of the cooling fluid (Mc). Increasing the Hceria from 3 mm to 7 mm improved the current density from 149.4 A·m-2 to 356.5 A·m-2 at 20 s and reduced the δ from 0.0357 to 0.0292 at 3000 s. Howevever, due to increased mass loading at increased Hceria, the overall oxygen producted increased resulting a in better reactor performance. Increasing the Dgap reduced the temperature gradient within the EOP, and hence enhancing the thermomechanical stability. An in-house oxygen pump sintered at 1373 K demonstrated an effective oxygen removal rate, operating at 162.1 A·m-2 with 0.3 V and 1373 K. However, the oxygen pump sintered at 1673 K showed a significant decrease in performance, resulting in inadequate oxygen pumping. Optimal reactor performance was achieved in the proposed CA scheme with a Tdif at 900 K, balancing the EOP oxygen removal capability in favorable operating temperature range and thermochemical reactor performance. This study provides comprehensive design guidelines and operational strategies for the integration of electrochemical oxygen pump with thermochemical reactors for practical applications.