Flexibility improvement in thermal power units by coupling with adsorption-based compressed CO2 energy storage system: A comprehensive analysis

To improve power system stability, thermal power units urgently enhance the deep peaking capacity. This paper proposes to couple an adsorption-based compression CO2 energy storage system (AB-CCES) with thermal power units. Compared to energy storage systems of the same capacity, AB-CCES system more effectively regulates load fluctuations and enables high-density CO2 storage through adsorption storage. The results indicate that the maximum power output of the integrated system increases to 123.35 % and the minimum power output decreases to 19.65 %. Total coal saving reaches 10.2 tons per day. RTE, exergy efficiency, ESD and cycle efficiency of AB-CCES system are 79.40 %, 66.11 %, 5.88 kWh/m3 and 81.62 %, respectively, under design conditions with a desorption temperature of 470.24 K. The adsorption capacity of CO2 in the adsorption tower is 99.37 kg/m3, which is 54.74 times the density of CO2 (1.185 kg/m3) under the same conditions. Sensitivity analysis indicates that higher energy storage pressures and adsorption temperatures improve system performance. Release pressure should preferably be higher than the critical pressure. The economic analysis indicates that LCOE is 0.098 $/kWh and the dynamic payback period (DPP) is 5.22 years under 4-h working conditions.