Performance evaluation of a solar transcritical carbon dioxide Rankine cycle integrated with compressed air energy storage

Solar thermal power generation is a promising technique in renewable energy utilization with the advantages of techno-economic, energy storability, power continuity, and stability. The present paper designed a solar transcritical carbon dioxide Rankine cycle integrated with compressed air energy storage, which could resolve the impact of solar energy intermittence and enhance the technical flexibility in solar thermal power and storage. An original system configuration with heat recovery of the compressed air was proposed to improve the system performance. The effects of carbon dioxide mass flow rate and heat source temperature on the performances of Rankine cycle and energy storage system were evaluated in the charging process. The results indicate that the air compression heat recovery could enhance the Rankine cycle performance, and weakened the negative effect of pump power at high carbon dioxide mass flow and air storage pressure. As the carbon dioxide mass flow and the air storage pressure increase, the system performance decreases severely due to the negative effect of pump power. The positive impact of expander power on system performance is more evident at the low mass flow of carbon dioxide, especially at high air storage pressure. As the heat source temperature decreases, the negative effect of pump power on the system performance gets severe, especially at the high mass flow. The air storage pressure has a more visible impact on the exergy efficiency at the low mass flow. Compression heat recovery results in a low exergy efficiency of the energy storage system in the initial charging process. The exergy efficiency is also affected by the air exergy in the isothermal storage chamber with a constant volume with a rapid heat transfer from the chamber to the environment.