Pumped storage power plants (PSWs)
This large-scale storage solution has been in existence for 90 years but is currently still the most efficient. Pumped storage power plants have an efficiency factor of between 75 and 80 per cent. These special hydroelectric power plants can store large quantities of electricity. When there is a surplus of electricity, water is pumped into a higher reservoir; when needed it flows back down via turbines and generators, bringing the stored electricity back into the grid. PSWs can therefore compensate for fluctuations quickly and flexibly. One of the oldest pumped storage power plants is the Koepchenwerk in Herdecke, which RWE started operating in 1930; since 2016 it has been the property of the Stiftung Industriedenkmalpflege und Geschichtskultur (Foundation for the Preservation of Industrial Monuments and Cultural History). Although a new construction is now serving as storage at that location, overall the significance of PSWs is decreasing. “Because electricity prices fluctuate less now than they used to, they are noticeably under increasing economic pressure. New builds are not profitable enough these days,” says Christian Metzger, innogy’s Senior Manager for Energy Storage.