A giant "water battery" in the Swiss Alps is finally operational, 14 years after construction began. The Nant de Drance Hydropower Plant can store enough power to charge 400,000 car batteries.
Until fusion (fingers crossed for the next few decades/centuries) is capable of solving all of our power needs, we have a problem to deal with in renewable energy sources: what to do when more power is produced than we actually need. On particularly windy or sunny days, production from wind and solar farms can outstrip demand for that power. While this is obviously a better problem than the reverse, and sometime even leads to a situation where consumers are paid to consume electricity, storage solutions are needed for days when the sun isn't shining and the wind is still.
The Nant de Drance Hydropower Plant is one novel solution for storing large amounts of this excess energy. It's not exactly a new idea, but it is effective nonetheless. During times when renewable energy sources are producing more energy than the demand, the excess energy is used to pump water from the plant into the Vieux Emosson reservoir above. The water can then be used by the hydropower plant below when more power is needed, using the water to power turbines as it passes through at 360 cubic meters per second.
The idea has been dubbed a "water battery", in that the energy is "stored" as water, just at a slightly higher altitude than it was previously. While the efficiency isn't perfect, it is far, far better than letting the excess power go to waste.
"There are losses like any storage, but the yield is very good," director Alain Sauthier told Reuters. "We have about 80% efficiency over the complete cycle."
“In less than ten minutes we can reverse the direction of rotation of the turbines and switch from electricity production to storage," he added to Swissinfo. "Such flexibility is key in order to react promptly to the needs of the electricity grid and adapt electricity generation and consumption. Otherwise, you risk a collapse of the grid and blackout".
The plant is capable of providing storage for much of Europe, not just Switzerland. Now fully operational, it is one of the most powerful plants on the continent.