Geothermal energy, which relies on hot rock below the earth’s surface, has long been used as a source of heating and electricity generation. Now, according to a new study by Princeton researchers, recent advances in drilling technologies are opening the possibility for the use of geothermal as an efficient way to store large amounts of energy for the electrical grid.

A series of interconnected artificial geothermal reservoirs are created during the process of drilling, and hot, pressurized water is pumped into the reservoir’s network of channels. Fluid accumulates in the reservoir and flexes the rock, and that pressure can later be released to drive hot fluid to the surface to power turbines for electricity. These reservoirs are a great a way to store large amounts of energy when demand is low and then release the energy when demand is high. Storing energy and shifting production to the most valuable times increases geothermal profitability and acts as a perfect complement for weather-dependent variable renewable systems such as wind and solar.

“Across the western United States where there’s a lot of geothermal potential, this could be the missing piece of the puzzle to get all the way to a carbon-free electricity system in conjunction with lots of wind and solar and shorter-duration batteries and demand flexibility,” said Jesse Jenkins, the study's lead author and an assistant professor of mechanical and aerospace engineering and the Andlinger Center for Energy and Environment.