Energy, exergy, economic (3E) analysis, optimization and comparison of different Carnot battery systems for energy storage

Energy storage is the key to solve the grid connection problem of renewable energy. Carnot Battery is one of the promising energy storage technologies nowadays. In this work, four Carnot Battery systems were constructed using organic Rankine cycle and vapor compression heat pump. Energy, exergy and economic (3E) models of the aforementioned systems were built. Using genetic algorithm as the optimization method, the levelized cost of storage was employed as the objective function. The systems were investigated, analyzed and compared according to the optimization results. The results show that regenerative systems that consist of a regenerative vapor compression heat pump present better thermo-economic performance. With thermal storage temperature increasing from 90 °C to 130 °C, the value of levelized cost of storage gradually decreases from 0.42 $/kWh to 0.29 $/kWh. The power-to-power efficiency decreases continuously with the increase of thermal storage temperature, however, the variation of exergy efficiency with thermal storage temperature is non-monotonic. The maximum value of 19.12% is achieved in system BORC-RVCHP when the thermal storage temperature is 100 °C. Also, it can be found that the value of the levelized cost of storage increases gradually with the lift of power-to-power efficiency. The cost and exergy destruction of each component are also calculated and compared. Two components that take the largest proportion in total investment cost are turbine and compressor for all the considered system configurations in this work.