Thermodynamic performance analysis of retrofitting decommissioned coal-fired power plant by Carnot battery energy storage

Abstract

Retrofitting decommissioned coal-fired power plants (CFPPs) to the Carnot battery (CB) with thermal energy storage (TES) could be an effective way to help the grid absorb more renewable energy. Towards the parameter matching problem in reconstructing the retired CFPP into CB, this paper proposes the feedwater temperature adjustment method and the steam parameter adjustment method to adjust the structure of the Rankine cycle. The results show that the feedwater temperature adjustment method and steam parameter adjustment method can improve the round-trip efficiency of power-to-heat (P2H) type schemes by 0.29 % to 0.95 % and 0.91 % to 0.97 %, respectively. As for CB constructed by heat pump (HP) form, the two methods can improve the round-trip efficiency by 0.09 % to 0.38 % and 0.95 % to 1.02 %, respectively. The sensitivity analysis shows that the feedwater temperature adjustment method is suitable for P2H type schemes and sensitive to variations in exhaust steam pressure. While the steam parameter adjustment method is sensitive to the heat absorption parameter on the heat source side of the matching process, a 1.36 % increase in efficiency can be achieved by regulating the thermodynamic parameters. Under combined heat and power mode, the energy utilization efficiency of CB can reach the maximum of 79.86 % (P2H) and 94.30 % (HP), respectively. At this point, two adjustment methods mentioned above can still be used to obtain efficiency gains close to the power generation model at different heat supply loads. The discounted CO2 reduction factors of different methods can reach about 0.38 t/MWh (P2H) and 0.46 t/MWh (HP) under different design conditions, respectively. This work would be expected to provide a detailed reference for the utilization of decommissioned CFPPs retrofitted to CB for renewable energy consumption.