Back in the 1970s, the Tennessee Valley Authority built what remains one of the largest energy storage facilities in the world: a pumped-storage hydropower plant. A pump takes water from the Tennessee River, shoots it up a giant shaft and holds it there until electric power needs peak during the day. At that point, the water is allowed to drain back down, spinning turbines that can generate enough power for a million homes. It’s almost like a gravity-powered battery as big as a cathedral … buried deep inside a mountain. Marketplace’s Lily Jamali spoke with Robert Kunzig, a freelance journalist who recently wrote about this in depth for the publication Science. He says pumped-storage hydro is attracting a lot of interest, thanks in part to generous tax credits from the 2022 Inflation Reduction Act.