Integration of compressed air energy storage into combined heat and power plants: A solution to flexibility and economy

To achieve carbon neutrality, conventional coal-fired combined heat and power (CHP) plants require higher operation flexibility to improve the grid's accommodation for renewable energy. Based on the promising converging interests between compressed air energy storage (CAES) and CHP, a novel CHP-CAES system with higher operation flexibility, energy efficiency, and round-trip efficiency (RTE) is proposed in this paper. The novelty of this system is that the released compression heat of CAES during the charge process can be recovered by the CHP, and the heat consumed during the discharge of CAES comes from the primary district heating network (DHN) instead of CHP. Firstly, the theoretical feasibility of the proposed CHP-CAES system is verified. Then, the operation flexibility, energy efficiency, and RTE of the CHP-CAES system are investigated. Results show that when the output heat of the CHP-CAES system is the design value of 150 MW, the power overload capacity can be increased by 3.04 %, and the feasible minimum load is decreased by 2.00 % of the design power. The maximum energy efficiency of the CHP-CAES system is increased from 68.38 % to 69.57 %, compared with the separate CHP system. Besides, the RTE of the CAES component is increased from 64.35 % to 77.05 %. Further, optimized scheduling strategies of this CHP-CAES system are proposed for the renewables accommodation scenario. Results show that the imbalance between power provision and demand can be notably reduced from 416.68 MWh to 1.01 MWh after the integration of the CAES system. Moreover, the profitability of the CHP-CAES system also would be improved by 14,449CHY by adopting the proposed scheduling strategies on the reference day, benefiting from the time-of-use (TOU) electricity price.