EAGER: Geothermal Battery Energy Storage Technical Feasibility

University Of Utah, Salt Lake City UT

Investigators

Abstract

This EArly-concept Grant for Exploratory Research (EAGER) project addresses the geotechnical engineering research needed to assess the feasibility of using the earth (a geothermal sedimentary reservoir) as a "battery" for large-scale energy storage to help manage the intermittent nature of solar and wind electricity generation. A geothermal battery would store solar generated hot water in the earth, and withdraw it as steam or use it in a hot water binary-cycle electricity generation system when needed, particularly when solar and wind are not available. Solar and wind electricity are being introduced into electric grids to supplement conventional electricity production, driven substantially by a desire to "decarbonize" electricity production, and more recently due to falling prices of solar and wind energy. Such introduction has in some ways been "too successful" leading to short-term curtailments of some solar and wind production. Also, electricity can be provided by solar and wind only when the sun shines and the wind blows, resulting in fluctuating production of electricity. Meanwhile, the deployment of "utility scale storage" (sometimes referred to as "grid scale") has not kept pace with this intermittent nature of solar, and to a lesser extent wind. The battery concept would utilize an existing geo-heated reservoir, but one where the reservoir temperature is too low to be economically viable. The addition of heat produced by solar thermal may be able to raise the low-grade geothermal reservoir temperature enough to utilize it efficiently for steam/binary cycle electricity production. To a large extent, this storage concept is all "renewable energy" drawing on geothermal energy and solar thermal energy combined. If feasible, the implementation of this storage concept would improve the reliability and extent of solar and wind electricity throughout areas of the nation, resulting in less reliance on carbon-based fuels. Energy storage that is cost competitive is essential in order to continue the addition of solar and wind electricity without great disruptions. This project focusses on the determination if a Geothermal Battery Energy Storage System is technically feasible at a potentially competitive cost. A steering committee will meet at the start of the project to provide planning guidance, and near the conclusion of the project to provide tentative consensus conclusions. A concluding workshop will be held where findings will be reviewed and consensus conclusions presented. The results of the project will add to the existing knowledge base by exploring technical phenomena related to the Geothermal Battery Energy Storage concept, including thermal energy movement within a geo-reservoir; rock expansion that occurs when heating the reservoir; the chemical effect on the rock due to the cyclic heating and cooling of the reservoir; and the potential for induced seismicity as thermal expansion and the injection of water into the reservoir produce certain fault movements. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.