(481e) CuO-Cu2O Redox Thermochemical Storage for High-Temperature Solar Process Heat

The integration of concentrating solar thermal technologies with thermal energy storage enables dispatchable power generation and around-the-clock operation of high-temperature industrial processes such as cement manufacturing, mineral and metallurgical extraction, waste recycling, and thermochemical fuels production. In particular, thermochemical energy storage (TCS) utilizes endothermic/exothermic reversible chemical reactions to store and release solar process heat at temperatures exceeding 600°C and with relatively high gravimetric heat capacity. We report on the experimental demonstration of a lab-scale TCS reactor prototype for storing heat at 1000°C. It consists of a packed-bed reactor filled with CuO-based granules undergoing reduction-oxidation (redox) cycles with a gravimetric heat capacity of about 470 kJ/kg, as measured by thermogravimetry. Two series of 30 consecutive redox cycles were performed by swinging either the oxygen partial pressure of the gas inflow (e.g. with air or nitrogen) or the air inflow temperature, yielding stable conversion in both cases. During the heat release, a spontaneous stabilization of the outflow temperature of the system at around 1025°C (equilibrium temperature of the CuO/Cu₂O system in air) was observed, which is beneficial for the downstream process. The influence of the gas flow rate and gas inflow temperature on the TCS system performance was parametrically investigated.