Geothermal Heat Pump & Phase Change Material Super-Hybrid Systems

The purpose of this DOE Phase 2 grant application is to further validate the geothermal HVAC installation savings made evident from our Phase 1 research. Moreover, it is to commercialize the solutions that will make these savings possible. This is important because geothermal HVAC systems are the most energy-efficient heating/cooling system known, according to the DOE. But the technology has not gone mainstream because of the higher first cost compared to conventional HVAC systems. The incremental cost of geothermal over conventional HVAC systems is typically 40-80% and mostly if not entirely due to the bore-field. This is because drilling 100-500 feet bore-holes is costly when the geology can vary from site to site and the appropriate drilling equipment and/or professional experience may or may not be readily available. Our goal is to reduce the incremental cost of geothermal by 50% or more and thereby better ensure the energy savings achieve a net positive cash flow for the owner. While the current tax credits of 30% for residential and 10% for commercial are helpful, these incentives will expire in the next 5 years so the industry needs to achieve a lower first cost basis to continue growing and eventually become the preferred heating/cooling system for home and building owners. At present, geothermal only has about 1-3% of the total HVAC market. Our Phase 1 research shows that the size of the geothermal bore-field can be reduced up to 40% by optimizing the design/layout of the bore-field and utilizing phase-change materials (PCMs) in or around the water loop. More specifically, by eliminating bore-holes in the center of the bore-field, ground heat transfer can be improved such that 10-30% fewer bore-holes are necessary. And by adding PCMs in a holding tank or in the bore-hole grout, the number of bore-holes can be reduced another 5-10%. Therefore, two commercial products have been proposed to achieve these bore-field size reductions: (1) Bore-field design software that encourages engineers and contractors to design long or donut- shaped bore-fields to improve heat transfer and thereby minimize the number of bore-holes; (2) PCM tanks (direct heat exchange plus water mass) and/or infused grout (indirect heat exchange) that store and release energy on a seasonal basis to further minimize the number of bore-holes. We are very excited and motivated to significantly improve our nation’s economy, health, resiliency, and security through this grant opportunity.Thank you for your consideration.