Performance Evaluation and Comparison of Experimental Organic Rankine Cycle Prototypes from Published Data

Abstract

The organic Rankine cycle (ORC) is a technology commonly used to convert low-grade heat (80-300 °C) into electricity, for a wide range of power (kW to MW). This technology is suitable for geothermal sources, thermal solar, biomass and waste heat recovery (WHR) from industry or engines. ORC has shown a renewed interest over the last decades thanks to its flexibility and easy maintenance. Working fluid and cycle architecture have been deeply investigated from a theoretical standpoint. Recently, there have been many experimental realization of small scale ORC with a particular investigation of the expander. Database of a hundred ORC experimental prototypes has been built from scientific literature, in order to perform a statistical analysis of ORCs. This database includes both qualitative and quantitative data on ORC facilities such as: operating conditions, performances achieved for components and complete cycle, components type and size used in the set-up, running environment of the ORC. Data compilation showed a wide variety of criteria and definition to evaluate ORC and components performances, making objective comparison complex. A distinction and classification of main criteria used in the ORC literature are presented. Then, a reflection of most suitable criteria for ORC performance evaluation is proposed, with an energy and exergy view, depending on the heat source. Finally, a preliminary database analysis is presented. Reported ORC gross electric efficiency is up to 10% and expander efficiency up to 70-80%.