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A new method of inter-stage double heat exchange is proposed, which combines compressed air energy storage with traditional coal-fired power unit. It can not only reduce the heat storage investment of compressed air energy storage system, but also broaden the peak regulation margin of coal-fired power unit, and promote the stability of power grid under high proportion of new energy access. In this paper, the characteristics of the coupling system under different working conditions of coal-fired power unit are studied, and the techno-economic calculation and analysis are carried out. The results show that the round-trip efficiency of the compressed air energy storage system coupled with the coal-fired power unit can reach more than 70% under different working conditions, and the return on investment and payback period are optimistic. Among them, the efficiency and economy of the system are the best when the coal-fired power unit is operating at 50%THA. At this time, the rate of return on investment can reach 18.44%, and the payback period is about 5.14 years. • A new method of inter-stage double heat exchange was proposed for coupling. • The thermodynamic model of the CAES system coupled with CFP unit was established. • The coupling performance and economic performance of the system were analyzed. • The round-trip efficiency of each working condition could reach more than 70%. • The payback period of each working condition was within 6 years. [ABSTRACT FROM AUTHOR]