Investigation of a Novel CO2 Transcritical Organic Rankine Cycle Driven by Parabolic Trough Solar Collectors

The objective of the present study is the detailed investigation and optimization of a transcritical organic Rankine cycle operating with CO2. The novelty of the present system is that the CO2 is warmed up inside a solar parabolic trough collector and there is not a secondary circuit between the solar collector and the CO2. Therefore, the examined configuration presents increased performance due to the higher operating temperatures of the working fluid in the turbine inlet. The system is studied parametrically and it is optimized by investigating different pressure and temperature level in the turbine inlet. The simulation is performed with a validated mathematical model that has been developed in Engineering Equation Solver software. According to the results, the optimum turbine inlet temperature is ranged from 713 up to 847 K, while the higher pressure in the turbine inlet enhances electricity production. In the default scenario (turbine inlet at 800 K and turbine pressure at 200 bar), the system efficiency is found 24.27% with solar irradiation at 800 W/m2. A dynamic investigation of the system for Athens (Greece) climate proved that the yearly efficiency of the unit is 19.80%, the simple payback period of the investment is 7.88 years, and the yearly CO2 emissions avoidance is 48.7 tones.