Utilisation of fluids with low global warming potential in supercritical Organic Rankine cycle

Organic Rankine cycle is simple and convenient technology for power and electricity production that can successfully exploit low temperature heat sources by the use of a refrigerant as a working fluid. However, as high GWP refrigerants are being phased out, the pursuit for the suitable low GWP working fluid continues. We have compared the performance of several wet, dry and isentropic fluids in a supercritical Rankine cycle. Thermal efficiency and net work produced were the primary parameters for comparison of high GWP R134a with its suggested low GWP replacements, namely R1234yf and R152a. Exergy analysis shows superior exergetic efficiency of R134a at high evaporator pressures. Nevertheless, R152a is a promising working fluid for a supercritical cycle, achieving larger net work and good thermal efficiency, albeit demanding a higher heat input.