Thermochemical energy storage performance of copper oxides: Effect of support materials

Thermochemical energy storage (TCES) is one of the most promising methods for utilization of solar energy. Metal oxides can exhibit reversible redox reactions that are useful for TCES applications. Especially, transitional metal oxides can undergo reduction reactions at high temperatures while absorbing energy given to the system. Later on, when the temperature goes down below a phase-transition temperature, exothermic re-oxidation reactions can take place. Air can be used both as oxygen source and heat transfer medium during the redox reactions. Recently, several studies have been published about the utilization of metal oxides for TCES applications. Among these metal oxides, copper oxides received a great attention owing to its cyclic stability and suitable redox temperature. In this study, copper oxides are used as energy storage material in combination with ZrO2, ZrO2-La2O3, MgAl2O4, Mg2Al2O4-La2O3, CeO2, CeO2-La2O3 as support materials. The best results were obtained from samples supported with MgAl2O4, Mg2Al2O4-La2O3. This most likely eventuated due to the other reversible phase transformations that take place in these systems such as formation of LaAlO3 and Cu2Al2O4. Especially Mg2Al2O4-La2O3 addition improved the system, both in terms of cyclic stability and heat capacity.