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

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. •Glycine doubled the energy storage density of limestone after 40 CaLP-TCES cycles•A novel CaLP-TCES system that integrates CO2 power cycle and steam power cycle was proposed•CaLP-TCES in fullday time mode is more applicable for the concentrated solar power•Higher operating carbonation temperature, conversion rate, and pressure ratio benefit the system's efficiency