Experimental validation of a 0.3 kW ORC for the future purposes in the study of low-grade thermal to power conversion

Organic Rankine cycle (ORC) is a promising development direction for energy conservation and environmental protection, as it can effectively convert low-temperature waste heat into mechanical work. This article focuses on the experimental performance study of what is likely the world's smallest scroll expander used in a 0.3 kW microORC system. The system uses R1233zd-E as the working fluid, and the expander is repurposed from a scroll compressor of an air conditioner, with a displacement of 11.1 mL/rev. In the first part of the experiments, the influence of the system pressure difference and the expander rotational speed on the system performance is investigated while keeping the expander inlet superheating fixed. The maximum system efficiency, expander efficiency, and power output were 5.46 %, 72.4 %, and 0.266 kW, respectively. In the second part of experiments, the effect of changing the heating source temperature on the system is explored while keeping the expander rotational speed and inlet pressure fixed. As the superheat increased, both the expander and cycle efficiency increased. In addition, this study combines the experimental results with previous data on small-scale ORC systems and discusses the similar trends, indirectly demonstrating that the 0.3 kW micro-ORC can achieve similar behavior as predicted in a large-scale ORC.