Storing hot materials while it’s cold and storing cold materials while it’s hot isn’t anything new in concept, but transplanting the idea in geothermal science is both attractive and economic. For example, the Defense Department spends $3.5 billion on the energy needed by its bases, out of which most money go to cooling and heating.
Ron Falta and Fred Molz, from Clemson University in South Carolina have received a $991,000 grant from the DoD to create a thermal energy storage called “Subsurface Thermal Energy Storage” (STES) that could help them reduce the money spent in this direction.
The DoD considered five military bases for the project, among which are the Marine Corps Recruit Depot at Parris Island and the Marine Corps Air Station in Beaufort, as well as locations in California and Rhode Island. “This technology has the potential to greatly reduce energy costs and greatly reduce carbon emissions,” said Falta, a professor in Clemson’s environmental engineering and Earth sciences department. “At the same time, it allows for the integration of renewable energy into the infrastructure of the base, and it provides a clear path for reducing base carbon emissions and carbon footprint.”
“STES is a technology where low-cost or waste energy, heat or cold, is harvested when it is produced or when it is available, stored in the subsurface using borehole heat exchangers or water wells, and then used when the heat or cold is expensive or difficult to obtain,” said Molz, an emeritus professor in the department. “This method of heating and cooling is far more efficient than conventional HVAC systems, and it could be 15 percent to 30 percent more efficient than current geothermal heat pump systems.”
The underground sediments have natural insulating properties. They have been used since ages, but using a conventional heat pump to transfer the heat between buildings and the underground is something new that might just work not only for the military, but also for civilian homes.
The researchers’ aim is that their system can pay for itself in 10 years and assure a carbon dioxide reduction of at least 15 percent, equal to the saved energy. The current prototype installation stretches on a 20,000 square feet building, with the existing cooling systems retrofitted, which saves money compared to the case when they would have to build new ones from scratch.