Performance analysis of carbon dioxide based combined power cycle for concentrating solar power

Abstract

A detailed analysis of a combined power block system using carbon dioxide integrated with a thermal energy storage system and solar field is presented. The combined power block system consists of a topping supercritical carbon dioxide recompression Brayton cycle and its waste heat is recovered by coupling a bottoming transcritical carbon dioxide power cycle. Transcritical carbon dioxide power cycle is selected owing to its temperature glide merit and better heat transfer characteristics than conventional waste heat recovery cycle systems using other working fluids. A molten salt that can operate at relatively higher temperature than nitrate solar salt is selected as a storage medium and as heat transfer fluid between thermal energy storage system and external heat exchanger of power block. A complete mathematical model for the heliostat field, solar receiver, thermal energy storage, and power block system has been developed. The discretized heat exchanger approach has been implemented to accurately capture the properties of working fluid and to provide more refined results. Theoretical analysis of the system includes first and second law efficiencies and power output. The research findings suggest that the integrated combined cycle configuration is a promising alternative for efficient energy conversion and the established framework provides a profoundly potential way to utilize concentrated solar power.