Enabling CCS via Low-temperature Geothermal Energy Integration for Fossil-fired Power Generation

Abstract

Among the key barriers to commercial scale deployment is the cost associated with CO2 capture. This is particularly true for existing large, fossil-fired assets that account for a large fraction of the electricity generation fleet in developed nations, including the U.S. Fitting conventional combustion technologies with CO2 capture systems can carry an energy penalty of thirty percent or more, resulting in an increased price of power to the grid, as well as an overall decrease in net plant output. Taken together with the positive growth in demand for electricity, this implies a need for accelerated capital build-out in the power generation markets to accommodate both demand growth and decreased output at retrofitted plants. In this paper, the authors present the results of a study to assess the potential to use geothermal energy to provide boiler feedwater preheating, capturing efficiency improvements designed to offset the losses associated with CO2 capture. Based on NETL benchmark cases and subsequent analysis of the application using site-specific data from the North Valmy power plant, several cases for CO2 capture were evaluated. These included geothermally assisted MEA capture, CO2BOLs capture, and stand-alone hybrid power generation, compared with a baseline, no-geothermal case. Based on Case 10, and assuming 2.7 MMlb/h of geothermally sourced 150°C water, the parasitic power load associated with MEA capture could be offset by roughly seven percent, resulting in a small (∼1 percent) overall loss to net power generation, but at levelized costs of electricity similar to the no-geothermal CCS case. For the CO2BOLs case, the availability of 150 ˚C geothermal fluid could allow the facility to not only offset the net power decrease associated with CO2BOLs capture alone, but could increase nameplate capacity by two percent. The geothermally coupled CO2BOLs case also decreases LCOE by 0.75 ¢/kWh relative to the non-hybrid CO2BOLs case, with the improved performance over the MEA case driven by the lower regeneration temperature and associated duty for CO2BOLs relative to MEA.