Theoretical and technical analysis of the photo-thermal energy cascade conversion for fuel with high-temperature combustion

Abstract

This study theoretically reveals the advantages of the photo-thermal energy cascading conversion over single thermal energy or a radiative energy conversion. It also analyzes the potential of the photo-thermal energy cascading conversion relying on typical power generation units with different parameters and considers the research outlook. The results demonstrate that the cascade conversion is more critical for high-temperature conditions since there are limitations for single radiation energy; thus, oxy-fuel combustion at a high temperature is more suitable. In consideration of technology conditions, the cascade system based on ultra-supercritical units can theoretically increase efficiency by more than 20% points under oxy-fuel combustion, whereas the efficiency of the cascade system based on combined cycle units can be theoretically increased by 15% points. The efficiency of the cascade system based on the small-parameter organic Rankine cycle unit can be increased by over 30% points according to the actual technology, and the small-scale unit could be applied in distributed energy systems. It is also pointed out that the further improvement of the system lies in the design of staged thermo-photovoltaic and complex thermal cycles to realize the cascade utilization of photo energy or thermal energy.