Thermochemical energy storage performance of Al2O3/CeO2 co-doped CaO-based material under high carbonation pressure

The calcium looping energy storage is a promising technique for thermochemical energy storage in concentrated solar power plants. Nevertheless, natural CaO-based materials, such as limestone, have an obvious decline in energy storage capacity during cyclic CaO/CaCO3 energy storage. In this work, a novel Al2O3/CeO2 co-doped CaO-based material for energy storage is synthesized by a wet-mixing method. And the thermochemical energy storage performance of the Al2O3/CeO2 co-doped CaO-based material under high carbonation pressure is studied. Additionally, the influences of the doping amount of Al2O3/CeO2, the carbonation pressure and the temperature on the energy storage performance of the synthetic material are discussed. The main compositions of the synthetic material are CaO, Ca12Al14O33 and CeO2. When 5 wt% Al2O3 and 5 wt% CeO2 are doped on CaO, the synthetic material shows the highest and most stable energy storage capacity under the carbonation pressure of 1.3 MPa during 30 cycles. The Ce3+ ions existing on the surface of the synthetic material can create oxygen vacancies on the surface of CaO and increase the amount of surface adsorbed oxygen, which facilitates the carbonation of CaO. In addition, the synthetic material possesses strong basicity and provides a large surface area and pore volume during the multicycle energy storage. The high energy storage performance of the synthetic material is attributed to the high pressure in the carbonation process, the good support of Ca12Al14O33 and the catalytic function of CeO2. The synthetic material can reduce the overall cost in concentrated solar power plants, thus it appears promising.