Thermodynamic assessment of the dry-cooling supercritical Brayton cycle in a direct-heated solar power tower plant enabled by CO2-propane mixture

This paper proposes an improved recompression combined cycle configuration to explore the potential of using CO2-propane in a direct-heating solar power tower (SPT) plant. The effects of critical parameters on overall performance were detailly analyzed. The exergy distribution of CO2 and CO2-propane cycles was compared respectively after being optimized by a genetic algorithm. The results show that the exergy loss of regenerators was reduced, and the entire exergy efficiency of the SPT plant was improved by configuring two high -temperature regenerators. The cycle performance of propane, serving as the second additive, becomes more significant when the cooling temperature is increased. The overall thermal efficiency of the CO2-propane-configured SPT plant is 2.08% higher than using CO2 alone at a condensation temperature of 50 degrees C. Meanwhile, the exergy efficiency of the SPT plant with CO2-propane cycle decreases less (1.67%) than CO2 (2.02%) when the condensation temperature rises from 42 degrees C to 50 degrees C. However, the temperature difference of the receiver would decrease when using CO2-propane. This study provides a valuable reference for the application of CO2-propane mixture in the dry-cooling Brayton cycle of the direct-heated SPT plant.

Automated summary

This paper proposes an improved recompression combined cycle configuration using CO2-propane in a direct-heating solar power tower (SPT) plant. The effects of critical parameters on overall performance were analyzed in detail. The study shows that the exergy loss of regenerators was reduced, and the entire exergy efficiency of the SPT plant was improved by configuring two high-temperature regenerators. The use of CO2-propane mixture provides a valuable reference for the application in the dry-cooling Brayton cycle of the direct-heated SPT plant.