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

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 thecommonly 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 apumped brine system with a parallel CHP plant and power generation by an Organic Rankine Cycle (ORC)are compared for a defined massflow rate of 225 kg/s and reservoir conditions of 180C and 49 MPa. Forthe 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 sCO2case. The net power of the sCO2plant displays a significantly highersensitivity to changes of the heat demand compared to the brine-ORC system. While the average exer-getic efficiency for the brine concept is 40.9% for R245fa and 40.0% for R1233zd(E), respectively, the sCO2concept reaches an average efficiency of 72.6%. Finally, two different operation strategies for the sCO2CHP plant are investigated against the background of potential turbine part-load models.     «

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 thecommonly 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 apumped brine system with a parallel CHP plant and power generation by an Organic Rankine Cycle (ORC...     »