of the Estonian Pumped-Hydro Energy Storage project
Estonian Pumped-Hydro Energy Storage (PHES) is an energy storage device that stores renewable electricity using the potential energy of water. PHES supplies electricity to consumers when renewable electricity is low on the electricity system by flowing water from the upper reservoir to the lower reservoirs through the turbines located at the depth of 730 meters below sea level. PHES stores energy when there is oversupply of renewable energy on the market by pumping water in the lower reservoirs back to the upper reservoirs.
This technology is well proven and reliable for already many decades. Pumped-hydro energy storage plants are the most mature and favourable large-scale storage technology, which helps balancing the power system and enables switch from fossil-based economy to renewable-based economy.
PHES generates power by three 167MW Francis-type pump-turbine units with nominal capacity of 522MWh/h and pumps water back to the upper reservoir by consuming nominal power 496 MWh/h. The nominal water flow at nominal capacity is 96m3/s at 1m/s flow velocity on the water intake screen. PHES can feed power to consumers at nominal rates 12 hours straight but in practice the need for storing and generating energy alternates within the twenty-four hours repeatedly.
One of the major advantages of this technical PHES solution is the very low environmental footprint compared to traditional hydropower and pumped-hydro plants – the construction of PHES does not require large landscape change and has no major impact on fauna and flora.