The upper basin (i.e. a higher water reservoir) serves as storage. If energy is needed for a short time, the water stored in the upper basin is fed to the turbines of the turbine house in the valley. This is how the turbines drive the generators. In this way, electricity can be generated in a matter of seconds. This compensates for fluctuations in the power grid and covers power peaks. The frequency of 50 Hertz in the European interconnected grid remains stable because of the balancing of the pumped storage facilities, which react very quickly compared to other power plants.
If there is more electricity available than is currently needed, the water from the lower basin is pumped back into the upper basin. The pumps are driven by the generators, which take over the function of motors. The water is now once again available for power generation. This ability of pumped storage power plants to both absorb and release energy helps to better balance power generation and demand. This makes pumped storage power plants indispensable when it comes to reconciling ever-increasing electricity production from wind and sun with conventional power plants and the electricity requirements of consumers.
Most of the upper basins of our pumped storage power plants have natural inflows. Part of the energy produced by our pumped storage power plants is thus attributable to renewable energies. We currently operate pumped storage power plants with an installed capacity of around 1.9 Gigawatts.