Bi-Directional Energy Storage with Innovative Geothermal Heat Pump System

In topic 10.a, Advanced Geothermal Energy Storage, BiDirectional Energy Storage, the Department of Energy Geothermal Technologies Office seeks to enable innovative geothermal technologies that improve the cost and effectiveness of energy storage, including for direct use and/or use with heat pumps to provide building space heating and cooling. Heating and cooling constitute approximately 48% of building energy consumption, representing a significant dollar cost to society. In addition, the vast majority of this energy is generated by fossil fuels, resulting in substantial environmental impacts. Geothermal heat pumps GHP represent the most energyefficient and environmentally friendly heating and cooling solution currently available and the most favorable heating and cooling technology to support our country’s electrification efforts. Energy storage technologies could enable increased use of variable electricity generation by time shifting excess production from when it is generated to when it is demanded. But most types of energy storage technologies cannot be used for large, gridscale, applications and can only discharge energy at capacity for time lengths ranging from seconds to minutes. Moreover, they tend to be inefficient. Low temperature thermal energy storage in shallow geologic formations for building space and water heating and cooling overcomes many of the challenges of conventional energy storage approaches. Energy storage using GHP’s is highly efficient, widely applicable, very high capacity, and affordable. Moreover, GHP’s with thermal storage can help meet present challenges of grid resiliency. The present proposal will advance new, innovative GHP technology to allow for thermal energy storage in shallow reservoirs. This technology, termed the advective GHP AGHP, fundamentally changes the manner in which heat is transferred with the shallow subsurface. The AGHP was modeled and tested successfully in a field trial in our DOE SBIR Phase I study, showing the potential of this approach to store and recover thermal energy in the shallow thermal subsurface for building heating/cooling. In the present Phase II proposal, a larger field test will be completed, in which a multiwell AGHP system will be tied to a building or series of buildings to provide thermal energy storage and recovery for 912 months. Following a successful Phase II investigation, the technology will be ready for commercial deployment with the ultimate goal to disrupt the conventional HVAC, GHP, and low temperature thermal energy storage industries; the annual US market size readily exceeds $8 billion with conservative projections.