High in the Swiss Alps, two reservoirs have been repurposed to make one giant energy storage facility. While hydropower often dams (and harms) existing rivers, the Nant de Drace project raised an existing reservoir to create a massive pumped storage hydropower plant with a capacity equal to 400,000 electric car batteries. This “water battery” can easily switch from storing energy to providing it, and could power a city of 1 million people for an entire day. Using water as a medium for generation circumvents the power storage limits of lithium batteries.

Why This Matters

Storage is key for making the transition to renewable energy. In Europe alone, it will take an estimated 200 gigawatts of storage by 2030 to hit the EU’s target of 45% renewable energy by the end of the decade. That’s four times the bloc’s current capacity. Still, those renewable energy targets are essential to getting off of fossil fuels and cutting planet-damaging emissions.

"If we want to go in the direction of having clean power, Nant de Drance is one of the stepping stones on this path," Robert Gleitz, a delegate of the board of directors of Nant de Drance, told CNN.

No Water? Try A Sand Battery.

To store and balance green energy in Finland, researchers have created a sand battery. The battery works by storing heat made from renewable sources in a silo of sand. The heat can be used to warm water in the winter when energy demands are higher and more costly. The hot air from the sand battery installed in the Vatajankoski power plant runs the area’s district heating system.

"If we have some power stations that are just working for a few hours in the wintertime when it's the coldest, it's going to be extremely expensive," Elina Seppänen, an energy and climate specialist for the city, told the BBC. "But if we have this sort of solution that provides flexibility for the use and storage of heat, that would help a lot in terms of expense, I think."