Performance of a 5 kWe Organic Rankine Cycle at part-load operation

•We presented a part load simulation of a 5 kWe Organic Rankine Cycle plant.•We compared the results for two working fluids: R245fa and SES36.•The maximum thermal efficiency of the cycle is reached at a low evaporation pressure.•The best operating point at partial load was determined.

This paper analyzes the performance of an Organic Rankine Cycle (ORC) system at part load operation. The objective is to understand its behavior from a thermodynamic perspective, identifying which elements are the most critical and which are the best operating points for each level of demanded power. This paper also compares two working fluids: R245fa and Solkatherm ES36 (SES36) for the same cycle specifications. The results have shown that the scroll isentropic efficiency has a great influence on the cycle performance and its thermal efficiency and that SES36 arises as a potential better fluid than R245fa. At the given maximum and minimum temperatures, the best operation point was determined. This allows reaching a maximum efficiency for each demanded level of power; depending on the required amount of power, the expander speed and the working pressure are adjusted.