Organic Fluids in a Supercritical Rankine Cycle for Low Temperature Power Generation

This paper presents a performance analysis of a supercritical organic Rankine cycle (SORC) with various working fluids with thermal energy provided from a geothermal energy source. In the present study, a number of pure fluids (R23, R32, R125, R143a, R134a, R218, and R170) are analyzed to identify the most suitable fluids for different operating conditions. The source temperature is varied between 125 degrees C and 200 degrees C, to study its effect on the efficiency of the cycle for fixed and variable pressure ratios. The energy and exergy efficiencies for each working fluid are obtained and the optimum fluid is selected. It is found that thermal efficiencies as high as 21% can be obtained with 200 degrees C source temperature and 10 degrees C cooling water temperature considered in this study. For medium source temperatures (125-150 degrees C), thermal efficiencies higher than 12% are obtained.