Enhancing flexibility of coal-fired power plants via compressed air energy storage integration: A 4E (Energy, Exergy, Economic, Environmental) and operational performance analysis

This study presents an innovative integration of a coal-fired power plant (CFPP) with a compressed air energy storage (CAES) system to enhance operational flexibility and efficiency. A comprehensive 4E (Energy, Exergy, Economic, Environmental) thermoeconomic model was developed to evaluate the coupled system, with a focus on quantifying performance metrics under low-load conditions. Key quantitative findings demonstrate that the integrated system achieves a round-trip efficiency (RTE) of 85.1 % and reduces the levelized cost of electricity (LCOE) by 23 % compared to standalone CAES systems. The feedwater temperature of the CFPP is elevated by 60.3 °C at 40 % turbine heat acceptance (THA) load condition, significantly improving boiler efficiency and enabling a 20 °C increase in economizer outlet flue gas temperature, thereby stabilizing denitrification system performance. Economically, the total equipment procurement cost is $36.83 million, corresponding to a LCOE at $0.165/kWh, with air compressors and expanders together accounting for more than 60 % of the capital expenditure. Environmentally, annual CO2 emissions are reduced by 13,618 tons through enhanced energy utilization of CFPP. Operational constraints reveal that the maximum allowable CAES capacity is 137.28 MW under 40 % THA load condition, limited by deaerator steam flow requirements. These results validate the system's ability to address low-load instability in CFPPs while balancing cost-effectiveness and decarbonization goals, offering actionable insights for grid-scale energy storage integration.