Case study: Repowering of ORC system by means of experimental test bench with supercritical carbon dioxide, proposal, and field experience improvements

Abstract

Although organic Rankine cycles (ORCs) have cornered the small-scale energy harvesting market, the generation capacities produced by sCO 2 cycles far exceed those of ORCs, reaching higher powers and efficiencies. This paper analyzes the results of the field tests performed in 2022 at the Grupo Dragón, Nayarit, Mexico, facilities, in which the objective was to validate the operation of the ORC IDEA-10 system with a capacity of up to 10 kWe. The thermodynamic states reached during the test time lapses in which there was full operational stability and with direct loads are analyzed. The results obtained together with proposals for improvement led to compare the performance of ORCs with sCO 2 systems for low temperature geothermal sources. The efficiencies of simple sCO 2 cycles (5.32%) turned out to be lower than that of ORC at the same temperatures (9.7%), however, the efficiency of the sCO 2 cycle improved notably in a regenerative configuration, given the properties of CO 2 near its critical point, reaching efficiencies above 25% even at low temperatures compared to conventional ORCs with efficiencies below 10%. Finally, the basis for the implementation of sCO 2 in low enthalpy geothermal applications was established, designing an experimental circuit with results obtained in the literature.