Solid packed bed storage-based flexible retrofit solution for power plants: Novel method for multi-heat source contribution analysis and thermal performance regulation

Coupling coal-fired power plants (CFPPs), which have abundant heat sources, with thermal energy storage (TES) is a very promising concept for improving grid reliability. This paper proposes a flexible power source construction route that considers efficiency, flexibility and economy around the multi-heat source integration method, the novel TES system concept and the process control method. Firstly, a novel multi-heat source contribution analysis method is proposed by equivalently combining special cold and hot sources to construct the equivalent cycle. The new method allows visualizing the different heat sources' contributions in the form of vector diagrams. In this way, a simplified construction method for integrated systems with multi-heat sources based on graphical methods can be further proposed. Based on the novel method, a new multi-heat source integrated system is proposed. The results show that the equivalent round-trip efficiency of the novel system based on the two-tank TES (TTES) concept can reach 74.49 %, which is more than 3 % higher than reference system. Analyzing the contribution of different heat sources, the heat extraction effect of two additional heat sources in the novel system can be about 1.3 and 2.3 times better than the reference system, respectively. The innovative integration concept based on the solid packed bed TES (STES) system is evaluated in terms of economy and efficiency. The new regulation method are proposed to ensure the STES integration concept flexibility. The equivalent round-trip efficiency of the novel system based on the STES concept is more than 1.5 % higher than reference system, reaching 57.28 %. Finally, the net present values of different integration concepts are discussed. The net present value of the optimal solution can be about 0.3 %–10 % higher in different scenarios.