Thermochemical energy storage by calcium looping process that integrates CO2 power cycle and steam power cycle

Abstract

Calcium looping (CaLP) is a promising thermochemical energy storage (TCES) technology. However, the effects of natural CaO-based precursors, and organic acid modifications on the conversion of CaO heat carriers in CaLP-TCES systems, are rare. Hence, a novel CaLP-TCES system that integrates the CO2 power cycle and steam power cycle to make full use of the energy was proposed. The effects of different CaO-based raw materials and organic acid modifications on the thermochemical energy storage performance of the CaO heat carriers in CaLP-TCES system are investigated. Results showed that limestone is the best option for CaLP-TCES when compared with other natural materials. The glycine-modified limestone retained a carbonation conversion of 28.5% during the 40th carbonation, which is 100% higher than that of the raw limestone. The global system efficiencies in the fullday time mode are always ∼72% higher than that in daytime mode. Hence, the glycine-limestone is a promising heat carrier for the CaLP-TCES system, and the CaLP-TCES in fullday time mode is more applicable for concentrated solar power. 850 °C might be a good option for the carbonation process, and the higher carbonation conversion rate and pressure ratio would be more beneficial for the global system efficiency.