Geothermal Technologies Could Push Energy Storage Beyond Batteries
September 17, 2018
Compressed-air storage in gas wells, geothermal energy in cold-climate communities, and geothermal-solar hybrid technology could offer new options for energy storage.
Three new projects at the National Renewable Energy Laboratory (NREL) will tap geothermal energy to advance new energy storage applications as part of the U.S. Department of Energy’s Grid Modernization Initiative. The newly funded projects will explore unconventional uses of geothermal technologies to improve grid reliability, resilience, and security.
The Department of Energy's Geothermal Technologies Office announced eight new projects via the Beyond Batteries Lab Call. NREL will be leading two of these projects and will be supporting a third.
Compressed Air and Heat Could Store Energy in Depleted Gas Wells
Project Title: Alternative CAES Technology Using Depleted Unconventional Gas Wells and Subsurface Thermal Energy Storage
Conventionally, compressed-air energy storage uses excess electricity to compress air into underground salt caverns. When electrical demand grows, this energy can be released through a turbine to provide electricity.
This technology is cost-effective, but few locations possess the necessary geologic features. This NREL-led project will explore the use of a more common feature—depleted unconventional shale gas wells. Not only will the project consider storing compressed air in the depleted wells, but it will also study storing waste heat from the compression process underground to improve overall efficiency.
“This is an idea that we’ve been nurturing for a couple years and it’s exciting to get a chance to devote some real time to developing it,” said Chad Augustine, a researcher in NREL’s techno-economic analysis group who will lead the project.
Geothermal Energy Could Enable Net-Zero Energy in Cold Climates
Project Title: Exploring the Role of Geothermal in Enhancing Cold-Climate Net-Zero Communities
Today, more and more communities are producing as much energy as they consume. These "net-zero" communities rely mostly on large amounts of solar photovoltaics to reach this goal. In colder climates, such as Alaska, greater heating demands and limited sunlight for much of the year make net-zero energy a more difficult goal.
Geothermal energy, which produces both electricity and heat, could be a promising solution for such communities. This project will study the feasibility of coupling geothermal technology with energy storage to provide financially viable, reliable, and resilient energy to zero-energy communities in cold climates.
“I’m excited to bring together NREL’s experts on geothermal techno-economic analysis, net-zero energy buildings, and renewable systems optimization to make cold-climate zero energy easier to achieve,” said Dane Christensen, who manages NREL’s residential building group's laboratory work and who will lead the project.
Geothermal and Concentrating Solar Power Could Team Up to Follow Grid Load
Project Title: Geo-Solar Hybrid Power Plant with Subsurface Thermal Energy Storage to Increase Geothermal Plant Dispatchability
As increasing amounts of intermittent renewable energy sources, such as wind and solar photovoltaics, are added to the electric grid, more dispatchable power sources are required to closely follow electric load to maintain grid stability. Geothermal energy, which produces power independent of time of day or weather conditions, could help provide this dispatchability. However, most geothermal power plants currently provide only steady power output because it is not economically feasible to reduce power output to follow grid load.
This project will study the feasibility of coupling a geothermal power plant with a concentrating solar power (CSP) system to store additional heat from the CSP system in the underground geothermal reservoir. The solar heat would increase the temperature of the already hot water in the reservoir, enhancing power plant performance and efficiency. This energy storage and power plant pairing could provide seasonal load-following capabilities.
The project will be led by the Department of Energy’s Idaho National Laboratory. “NREL will support the geo-solar integration optimization to maximize the value of geothermal plant dispatchability,” said Guangdong Zhu, a researcher in NREL’s thermal systems group who will lead NREL’s portion of the project.