As a low-cost grid-scale electrical storage, Carnot battery has attracted increasing interest due to the rapid growth of renewable energy. However, the low-grade efficiency and technological maturity are the problems in the development of the Carnot batteries. This paper proposes a technical approach to transform the thermal power stations into high-efficiency storage plants, combining existing equipment with new technologies. For this, a case study using a typical 1000MW supercritical coal-fired plant is investigated in this paper. The dynamic cycle and the high-temperature reservoir are comprehensively re-designed to enhance the round-trip efficiency of the Carnot battery. The results show that the optimization of the Rankine cycle increases the cycle efficiency by ~2% through rising the feedwater temperature. In the design of the high-temperature reservoir, volcanic rocks are used as the storage medium to be heated at 750~800 Â°C, combined with the cascade utilization of thermal energy, which makes a great contribution to the round-trip efficiency of 49.5%. Based on the obtained results, it is concluded that the high-temperature Rankine Carnot battery has the potential to become a promising grid-scale electrical storage in the coming future.
Keywords Carnot battery, electrical storage, Rankine cycle, renewable energy, round-trip efficiency