Performance Analysis of a Carnot Battery System Coupled Ca(Oh)2/Cao Thermochemical Heat Storage and Coal-Fired Power Plant

Abstract

To enhance the utilization of renewable energy, accelerate the transition of the role of coal-fired power plant, and reduce carbon emissions, a Carnot battery system integrated thermochemical energy storage and coal-fired power plant is designed and analyzed. This system employs a sCO2 Brayton reverse cycle to transfer electricity to heat, utilizing CaO/Ca(OH)2 as the heat storage material. In the energy release scenario, the hydration reaction releases heat to the reheat steam, thus replacing a portion of the reheat energy. Aspen Plus is used to construct the system and is validated by practical operating data. The thermodynamic analysis shows the coupled system achieves a round-trip efficiency of 51.4% and an exergy efficiency of 44.5%. The implementation of the Carnot battery can effectively reduce coal consumption by more than 7.3%. However, it may elevate the flue gas temperature at the high temperature reheater outlet beyond the operational limits. To address this problem, a feasible boiler heat exchanger area adjustment scheme is proposed based on the heat balance analysis of the boiler. Additionally, the effects of the extraction capacity and pressure on system performance are examined. Regenerative steam at 0.03 MPa with an extraction capacity of 10.0 kg/s represents the optimal selection.

Keywords: Carnot battery, Thermochemical energy storage, Exergy analysis, Efficiency optimization, Boiler heat balance, Boiler improvement