There’s a big hole in the ground at a site on the eastern side of the Czech Republic. It’s near the border with Poland, to the north, and Slovakia, to the west. Right now, that hole looks like a dark pit of nothingness. But in it, several researchers see a potential solution to a looming energy problem.
The pit measures some 7 meters (23 feet) across and 274 meters (899 feet) down. That makes it almost as deep as the Eiffel Tower is tall. The shaft plunges into a wide, underground coalfield that stretches into Poland. Until 2021, the hole was used as a mine. The coal that came out of it was burned to generate electricity.
But if everything goes according to plan, that hole will soon play a very different role in generating electricity.
Engineers believe the mine could be remodeled to store energy. It would work as a kind of underground rechargeable battery. But it’s nothing like a AAA or AA, nor the batteries that power electric cars. It wouldn’t be small and would stay in place for years, if not decades. And it wouldn’t use rare metals or have positive and negative terminals.
Instead, this battery would be enormous — and run on gravity.
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