Comparative study of working fluids for a Rankine cycle operating at low temperature

The main results of a thermodynamic study on the use of a low temperature heat source (150°C as maximum) for power generation through a basic Rankine are reported in this paper. Different working fluids such as water and some hydrocarbons and coolants are studied. The procedure consisted in modifying the input pressure and temperature to the turbine. The efficiency for these fluids is a weak function of temperature, i.e., overheating the inlet fluid to the turbine does not cause a significant change in the efficiency. However, when the pressure ratio in the turbine increases, much larger values of efficiency are obtained, and also, as the input temperature to the turbine rises, the efficiency increases more sharply. As result, a maximum efficiency of 9% was obtained. It is shown the technical viability of implementing this type of process for recovering residual wastes for very low temperature, as well as an energy alternative and/or strengthener of non-conventional energy sources in non-provided zones. ► Some hydrocarbons and refrigerants are studied in ORC. ► The influence of the turbine inlet temperature and the pressure ratio is analyzed. ► The viability of implementing this process is demonstrated. ► A maximum efficiency of 9% is obtained at an inlet temperature of 110 °C using R600a.