In Vattenfall’s central control room, human operators aided by algorithms monitor the electricity grid, and the market, to judge whether their pumped hydro plants ought to be generating or pumping. Kühne adds that the frequency of alternating between these modes has gone up over time because of renewables’ variability.
If you can get the response right, however, you can make a lot of money. On its website, Vattenfall describes pumped hydro as “highly profitable.” A paper published last month estimated the effect of rising renewables in Spain between now and 2050. With gradually decreasing electricity prices, higher variability, and less need to import electricity overall, the authors found that energy storage would be utilized 12 percent more in the future—and that a system combining renewables with pumped hydro energy storage would see its profits rise.
Pumped hydro could, in principle, work in lots of places around the world, says Rosie Madge, a systems engineer at Energy Systems Catapult, a nonprofit research and innovation center: “Most countries in the world do have geographies that are suitable for it.”
A report by Madge and colleagues, published in October, scored 11 countries in terms of their suitability for pumped hydro and other long-term energy storage tech. Two notoriously flat nations, Denmark and the Netherlands, fared poorly. But the others were all extremely well-suited to conventional pumped hydro and a few, including the UK, Australia, and China, were very well-suited to the high-density version. The scores were based partly on how ready and willing each country was to deploy the tech, and also on market conditions.
But even in that analysis, it was conventional pumped hydro that appeared most deployable overall—when compared to multiple other long-duration storage technologies including high-density pumped hydro, hydrogen, ammonia, metal air batteries, compressed air, and non-pumped-hydro gravity storage.