CO2 Plume Geothermal (CPG) and the Earth Battery -- Innovative Geothermal Power Production Using Non-water Working Fluids

In topic 11.b, Dispatchable Geothermal Operations, the Department of Energy (DOE) seeks to enable more widespread deployment of geothermal as a dispatchable energy source, permitting expansion of geothermal power in general and as a compliment to growing intermittent energy sources. TerraCOH’s CO2 Plume Geothermal (CPG™) and Earth Battery™ technologies are ideally suited to meet and exceed this objective. Presently, geothermal is one of the least expensive ways to produce electricity, but it has been geographically limited to areas with very high subsurface temperatures and plentiful water. Additionally, conventional technologies have largely been limited to continuous operation to ensure equipment and reservoir stability, as well as maintain low power production costs. TerraCOH’s technologies constitute a continuum of cost-effective applications for using the earth’s geothermal heat for both the generation of renewable power and large-scale geologic energy storage. Our solutions are innovative in their use of non-water fluids, and combinations of water and non-water fluids, to harness geothermal heat and store energy in subsurface formations. By using non-water fluids – primarily CO2 – we will be able to dramatically expand the areas in the US where geothermal power and energy storage can be economically deployed, from ~1% to ~50% of the US land area. Stored CO2 can play three important roles: 1) a working fluid for efficient, low water- intensity energy conversion in Brayton Cycle turbines, 2) a supplemental fluid that creates pressure to recirculate working fluids, and 3) a shock absorber that allows diurnal/seasonal energy storage. The primary objective of our Phase 1 study is to modify our existing, extensive, coupled geophysical-mechanical numerical models of CPG™ systems, from continuous or cyclical operation to allow for true dispatchable analyses. Our models can permit diurnal/seasonal variations in production, so the next step is to allow inclusion of real electricity supply/demand curves from, for instance, an independent system operator. We must also tie in performance limitations (e.g., response times) provided by our equipment suppliers. From there, we will expand our Levelized Cost of Energy models to permit inclusion of ancillary benefits (e.g., peak shaving) that may be provided by dispatchable system operation. Our current economic models can only valuated straight power sales and credits.