One of the biggest challenges for renewable power like wind and solar has always been storage, so the grid can keep running cheaply and reliably even when the wind isn’t blowing and the sun isn’t out. Though researchers in labs are racing to make better batteries, one company says we don’t need new tech—just a new application of something old. With a heavy train and a hill, gravity can take care of the problem.
Here’s how it works: When solar panels or windmills are pumping out excess power, it can be sent to a set of weighted train cars on a small hill. The train uses the power to push itself up the hill. Then, whenever the power is needed again—say on a hot day when everyone turns on an air conditioner—the train can roll down the hill, regenerating power to push back into the grid.
Why hasn't anyone tried this before? Maybe it's impractical. Or maybe, as Francesca Cava, chief operating officer for Advanced Rail Energy Storage North America, says: “Like any really simple idea, sometimes people just don’t think of it."
One of the main ways utilities store extra power now is by pumping water at dams, but that’s expensive and wasteful in places that are struggling with drought. Dams also cause environmental damage. “If you have to blast through rock and put tunnels in, that’s a lot more environmentally damaging than laying down track and having a train go up and down," Cava explains.
Current batteries aren’t a great solution either. “If you use lithium you basically destroy wherever that lithium is coming from, and afterwards there’s a huge amount of hazardous waste,” Cava says. Batteries have to be replaced often, while trains and track can last 40 years. It’s also difficult to store much power in a battery, but the train system can store as much as a gigawatt.
The company is currently getting a permit to install a small system in Nevada, and hopes to grow quickly after others see the tech in action. "Utility companies aren't very adventuresome—they would prefer to see it built before they put it in themselves," Cava says. "But our demo is working, and they're excited."