Design and experimental analysis of a mini ORC (organic Rankine cycle) power plant based on R245fa working fluid

• Few technologies allow exploiting low-temperature thermal energy.
• The prototype of a small ORC power plant has been realized.
• Parametric analysis of power performance.
• The realized pilot plant featured 1 kW output power and a cycle efficiency slightly greater than 9%.

ORC (organic Rankine cycles) represent a sound solution for the exploitation of thermal energy available at low temperature.The prototype of a small ORC power plant has been realized at the Energy Systems Laboratory of Cassino University. In this paper, the plant design, the experimental methodology and the thermodynamic analysis of the work cycle have been illustrated. The aim of the work is to assess the feasibility of small-scale ORC plants.The basic idea is to analyze the performance of a small ORC plant able to exploit low-temperature heat sources.Thus, a simple organic Rankine cycle has been analyzed and R245fa as working fluid has been selected. Due to the small working fluid flow rates, a volumetric machine, in particular a scroll expander, has been chosen for mechanical power generation.The hot source temperature has been varied in the range 75–95 °C and the cold sink temperature ranged between 20 °C and 33 °C. The R245fa vapor maximum pressure varied from 6 up to 10 bar. In this operating range, the best obtained results were: electric power equal to 1.2 kW, specific work about 20 kJ/kg and cycle efficiency slightly greater than 9 percent.