Bi-Directional Energy Storage with Innovative Geothermal Heat Pump System

In topic 10.a, Advanced Geothermal Energy Storage, Bi-Directional 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. Ground source heat pumps (GSHP) represent the most energy-efficient and environmentally friendly heating and cooling solution currently available. 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, grid-scale, 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 GSHP’s is highly efficient, widely applicable, very high capacity, and affordable. The present proposal will advance new, innovative GSHP technology to allow for thermal energy storage in shallow reservoirs. This technology, termed the advective GSHP (AGHP), fundamentally changes the manner in which heat is transferred with the shallow subsurface. The AGHP has been demonstrated in full field trials, and in the present proposal, it will be combined with theory related to deep geologic, high temperature thermal storage, to investigate shallow thermal storage for building heating and cooling. This Phase I work will include numerical modeling followed by a small field test of the technology. Following a successful Phase I investigation, a Phase II study would involve a larger field test in which the thermal storage reservoir is tied to a building or series of building to provide thermal energy storage and recovery for at least one year. The ultimate goal of these commercialization efforts is disrupt the GSHP and low temperature thermal energy storage industries; the annual US market size readily exceeds $6-8 billion with conservative projections.