An energy return on investment for a geothermal power plant on the Texas Gulf Coast

Abstract

This thesis examines the energy return on investment (EROI) of a model 3 MW hybrid gas-geothermal plant on the Texas Gulf Coast. The model plant uses a design similar to the DOE Pleasant Bayou No. 2 test geothermal plant, and uses a gas engine to harness entrained methane and an Organic Rankine Cycle turbine to harness thermal energy from hot brines. The indirect energy cost was calculated using the Carnegie Mellon University Economic Input-Output Life Environmental Life Cycle Analysis (EIO-LCA) model. The EROI of the plant using the 1997 EIO-LCA energy data is 12.40, and the EROI of the plant using 2002 EIO-LCA energy data is 14.18. Sensitivity analysis was run to determine how the plant parameters affect the EROI. A literature review of the EROI of different power sources shows that the EROI of the hybrid geothermal plant is greater than the EROI of flash steam geothermal and solar, but is lower than the EROI of dry steam geothermal, wind power, nuclear, coal, gas, and hydroelectric plants. An analysis of the EROI to financial return on investment (FROI) shows that the FROI for a hybrid geothermal plant could be competitive with wind and solar as a viable renewable resource in the Texas electricity market.