How giant “batteries” in the Earth Could Slash Your Electricity Bills

“Battery storage on its own — or what people call short-duration energy storage — is very important,” said Martin Staadecker, an energy systems researcher at the Massachusetts Institute of Technology and lead author of the new study. “But you can’t just rely on lithium-ion batteries, because it would be very expensive to have enough to actually provide power for an entire week.”

As of 2022, the U.S. had 43 pumped storage hydropower facilities with a combined generation capacity of 22 gigawatts. (For perspective, the U.S. has around 150 gigawatts of wind power and 140 gigawatts of solar.) According to the Department of Energy, the U.S. has the potential to double its capacity for that kind of energy storage. In 2021, the Biden administration launched its Long Duration Storage Shot, part of the Energy Earthshots initiative, aiming to reduce the costs of the technology by 90 percent in a decade. And last year, it announced $325 million for 15 long-duration energy storage projects, including one that stores heat energy in concrete and others to make newfangled batteries made of iron, water, and air.

The researchers looked at long-duration energy storage without considering the particular technique involved, asking what would be the cheapest way to get the Western Interconnection to be 100 percent emissions-free. Their study found that long-duration energy storage would be particularly beneficial to a utility’s customers, reducing electricity costs in times of high demand on the grid, like in the late afternoon as people return home and switch on appliances at the same time that solar power on the grid is waning. More storage also means more backup power for ever-hotter heat waves, when whole regions flick on their AC units. 

Companies are figuring out how to store energy underground, too. A company called Hydrostor, based in Toronto, Canada, uses excess renewable energy on the grid to pump compressed air into subterranean caverns filled with water. That forces the water aboveground into a reservoir. When the grid needs electricity, Hydrostor lets that water flow back into the chamber, pushing the air back to the surface to drive turbines. “We’re kind of creating a piston underground of water,” said Jon Norman, president of Hydrostor. “We’re actually building a cavity out using techniques that they use in the hydrocarbon storage industry to store propane and butane.”

If a region runs low on renewable power, like when the sun sets, it would have to import carbon-free electricity from elsewhere. But that requires transmission lines that cut through hundreds or thousands of miles of land, which are difficult to get approved and expensive to build. In the scenario imagined in the study, it would cost between $83 billion and $130 billion to maintain the Western Interconnection and install infrastructure, including long-duration storage, depending on how fast the cost of the technology falls.

With long-duration energy storage, utilities can deploy more solar panels and wind turbines locally and store up their energy, rather than having to ship it from somewhere else. Kevin Schneider, an electrical engineer who studies the grid at the Pacific Northwest National Laboratory but wasn’t involved in the new research, said that could reduce the significant costs of building long-distance transmission lines. “Getting that flexibility in the system, where you can have a reservoir of electricity that you can store up and then release, that’s what allows us to not have to build as much infrastructure, and also be a little bit more resilient.”

The grid of tomorrow, then, may hum with renewable energy stored both in giant battery banks, but also stored in the landscape itself. Solar and wind power would be wasted no more.

Matt Simon is a Senior Staff Writer at Grist. This story was originally published by Grist. You can subscribe to its weekly newsletter here.This story has been updated to clarify that a cost estimate to deploy long duration energy storage included other infrastructure and maintenance on the grid.