Experimental research of a small biomass organic Rankine cycle plant with multiple scroll expanders intended for domestic use

Abstract

This paper presents the results of the experimental research carried out on an organic Rankine cycle (ORC) system with two volumetric expanders running in serial and parallel mode. Both tested expanders had a nominal power of 1 kWe. The heat source used was a boiler with a nominal power of 35 kWt, powered by wood biomass. The main aim of the study was to determine the parameters and isentropic efficiency of expanders operating in the ORC, when connected in series or parallel. The analysis showed that the maximum thermal efficiency of the cycle with expanders operating in serial mode was 3.07%, and in parallel mode was about 3.31%. The maximum second-law efficiency of the system with expanders operating in serial and parallel mode was 8.82% and 9.53% respectively. When the set of expanders operated in serial mode, the maximum electrical power measured after the rectifier was about 993 We, and in the parallel mode about 1,206 We. In both operation modes, the average thermal power supplied to the condenser was approximately 22 kWt at an average temperature of the fluid of 72–73 °C. This amount of heat could be used for the preparation of domestic hot water and/or for space heating in a single-family house. The article fills the literature gap on experimental studies of scroll expanders running in serial and parallel modes in ORC microsystems, which are very few at this moment.