Investigation on the Application of Carbon Dioxide Power Generation Cycles in Solar Energy Heating Utilization

Abstract

In the domain of solar thermal energy utilization, the power cycles that utilize carbon dioxide as the working fluid predominantly encompass the transcritical Rankine cycle and the supercritical Brayton cycle. This study employs MATLAB programming to compute and examine the thermal efficiencies of these two cycles across a spectrum of solar collector temperatures ranging from 200 to 1000°C and carbon dioxide working fluid pressures from 10 to 40 MPa. At elevated temperatures, the thermal efficiencies of both cycles augment with the escalation in working fluid pressure; however, at reduced temperatures, the alterations in thermal efficiencies of the two cycles are converse. Furthermore, beyond a specific temperature, the thermal efficiency of the supercritical Brayton cycle consistently surpasses that of the transcritical Rankine cycle. By means of fitting, the relational expressions for the thermal efficiencies of the two cycles being equivalent were ascertained. In light of practical circumstances, it is proposed that the supercritical Brayton cycle should be adopted when the solar collector temperature exceeds 350°C, whereas the transcritical Rankine cycle is more appropriate below 350°C.