Scientists at Lawrence Berkeley National Lab are studying using aquifers as a thermal battery to store excess heat in the summer and as a source of heat in the winter. The systems are called ATES – Aquifer Thermal Energy Storage. The idea is similar to geothermal heat pumps – which can heat and cool homes and small buildings with pipes that are buried into the Earth. For small buildings, the ground serves as a near infinite source or sink for heat, maintaining constant temperatures.
Aquifers are deep water that can run for miles under cities and across states. Water from the aquifer is withdrawn, heated using the excess energy, and put back into the ground to be stored. The ground is a wonderful insulator, and the ground can hold onto the heat for several months. In the winter, heat is drawn from the ground by pumping the water from aquifer through heating equipment, like heat pumps. The cooled water is returned to the ground.
In places where summer cooling is dominant, summer building heat is used to heat the aquifer and the heat stored for winter heating. In northern climates, building heat as well as heat from solar hot water panels and even excess power from solar PV and wind systems can be added to the aquifer. The research concluded that fossil fuel power from peaking generators could be reduced by 40%, though the system will cost 15-20% more than traditional thermal energy storage. But that advantage is that using the Earth will not require building large above ground tanks, that take up valuable land. – Steve Terry, DTC HVAC & Refrigeration Instructor
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