of the Estonian Pumped-Hydro Energy Storage
Estonian 500MW Pumped-Hydro Energy Storage (PHES) is a semi-loop energy storage project that generates electricity using previously accumulated renewable energy. The plant is planned to become operational near Tallinn in Paldiski in year 2028 and it will offer flexibility services to the Nord Pool Spot power market. The project has a unique hybrid business model of combining power storage services and deep granite mining which remarkably improves financial viability because of multiple revenue sources.
PHES uses the Zero Terrain technology that unlike conventional pumping stations worldwide uses the height difference that occurs between surface water bodies and caverns built into the Earth’ crust.
PHES accumulates energy, when there is surplus of renewable electricity on the market. When there is little renewable electricity available the PHES generates power by flowing water from the upper reservoir to the lower reservoirs through turbines located at the depth of 730 meters below sea level. In other words, renewable energy is accumulated by pumping water from lower reservoirs to the upper reservoirs and vice versa.
PHES generates power (6GWh per 1 cycle) by 3 Francis-type pump-turbine units with nominal capacity of 506MWh/h and accumulates energy by pumping with nominal power 509 MWh/h. The nominal water flow at nominal capacity is 96m3/s.