Synergetic characteristic of a novel thermally-driven CCHP system based on supercritical and transcritical CO2 cycles

Abstract

A novel poly-generation system is proposed based on supercritical carbon dioxide (SCO2) Brayton cycle and transcritical carbon dioxide (TCO2) refrigeration cycle to meet the seasonal energy demand in buildings. The thermodynamic model of the combined cooling, heating and power (CCHP) system was constructed based on the laws of thermodynamics, and seasonal operation modes were also analyzed. The Techno-economic performance of CCHP system was analyzed and compared with the single output systems and organic working fluids. The results show that the temperature of the turbine inlet in SCO2 cycle should be close to the heat source temperature and the temperature of the condenser outlet should be close to the critical temperature. The optimal pressure of the condenser outlet for coefficient of performance is about 9.3 MPa, while it is 8.6 MPa for power generation. The optimum thermodynamic and economic performance cannot be achieved simultaneously. The power generation of CO2 is 13.13% worse than that of organic working fluids and coefficient of performance of former is worse than that of latter. As the manufacturing cost goes down over time, the CCHP system based on CO2 will further improve its economic performance in the future.