Thermodynamic comparison of direct supercritical CO2 and indirect brine-ORC concepts for geothermal combined heat and power generation

Christopher Schifflechner, Fabian Dawo, Sebastian Eyerer, Christoph Wieland and Hartmut Spliethoff

Renewable Energy, 2020, vol. 161, issue C, 1292-1302

Abstract: Petrothermal reservoirs contain a tremendous technical potential without major regional restrictions. The application of supercritical CO2 (sCO2) as a heat carrier might be a promising alternative to the commonly discussed usage of water. This study evaluates both heat carriers for a CHP application. A novel CHP plant layout for a thermosiphon with direct utilization of sCO2 for power generation and a pumped brine system with a parallel CHP plant and power generation by an Organic Rankine Cycle (ORC) are compared for a defined mass flow rate of 225 kg/s and reservoir conditions of 180 °C and 49 MPa. For the ORC with R245fa the annual amount of net electricity is 3% higher than for the ORC with R1233zd(E) and 8% higher than for the sCO2 case. The net power of the sCO2 plant displays a significantly higher sensitivity to changes of the heat demand compared to the brine-ORC system. While the average exergetic efficiency for the brine concept is 40.9% for R245fa and 40.0% for R1233zd(E), respectively, the sCO2 concept reaches an average efficiency of 72.6%. Finally, two different operation strategies for the sCO2 CHP plant are investigated against the background of potential turbine part-load models.

Keywords: Enhanced geothermal systems (EGS); Supercritical CO2 (sCO2); Organic Rankine Cycle (ORC); Geothermal energy; Combined heat and power (CHP); CO2 plume geothermal (CPG) systems (search for similar items in EconPapers)
Date: 2020
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Citations: View citations in EconPapers (7)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:161:y:2020:i:c:p:1292-1302

DOI: 10.1016/j.renene.2020.07.044

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