Energy storage is innovative in Estonia and Zero Terrain technology is unique in the world.

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What is a Pumped-Hydro
Energy Storage?

Water powered electricity storage in Estonia with a 500 MW capacity. This means the underground water reservoirs can store and release up to 6 000 MWh of electrical power per an 12-hour cycle. In order to produce electricity, a hatch will be opened in water intake,
seawater will flow into underground reservoir through inflow channel via electricity turbines. In order to consume electricity, water from reservoirs will be pumped back into the sea. Want to know more? Keep reading below.

Reservoirs, water intake inflow channel, turbine room, entrance shaft, ventilation and cable shafts and access tunnels are planned underground, ca at the depth of 500-600 m inside the rocks of crystalline basement. At the proposed scale, the pumped hydro energy storage is the cheapest option for energy storage.

Estonian PHES project will have significant impact on Estonian economy and solving challenges related to climate change, foremost by: 

– reducing CO2 emmissions in energy sector; 

– lowering the variable cost of electricity production; 

– enabling large scale integration of renewable energy sources; 

– contributing to the increase of GDP; 

– increasing tax revenues; 

– reducing grid tariffs for other consumers; 

– enhancing the security of supply for mineral resources in Harjumaa

Based on the character of Estonian PHES and its location relative to Pakri nature area and Pakri birds area (outside Natura-areas), the Strategic Environmental Assessment stated that the intended activity will not lead to the loss and division of area of habitats, nor such impact on water reserves, which could endanger preservation and well-being of species and habitats that are under protection in the areas.

The storage project enables saving in generation capacity which means we do not have to build as many new power plants. This kind of storage capacity is vital for facilitating the uptake of variable renewable energy sources, such as wind and solar energy. The project is also on the list of Projects of Common Interest (PCI) which includes projects that are of strategic importance in executing the European Union’s policies.

Estonian PHES with its 500 MW capacity is able to produce up to 6000 MWh of electrical power in 12 hours. The capacity factor of the power plant is 80%, which means that for pumping the filled reservoir complemetly dry will consume 7500 MWh. 

The current record for electricity consumption is 1587 MW. This happened in one afternoon in 2010. In similar extreme cases, when there happens to be lack of electricity production in the system at the same time, Estonian PHES (500 MW) will thus be able to cover one third of Estonian peak consumption for up to 6 hours. 



In Paldiski, Estonia. The power plant will be built underwater of Pakri Peninsula. Suitable natural and geological conditions (sufficient sea depth, bedrock is amphibolite gneiss), proximity of energy infrastructure, synergies with existing and planned industries and green-oriented municipality make Paldiski the best location for pumped-hydro storage project.

Alexela Group and Sunly Innovation have financed the projects development. Peep Siitam is the CEO and Project Manager for Energiasalv Pakri. He is supported by Alexela and Sunly.

In order to construct Paldiski PHES, four documents/permits are necessary, for which the bodies conducting proceedings and making decisions are different institutions: 

– Detailed Spatial Plan for allowance to build construction works that are functionally in connection with the coast inland and at the sea area; decision-maker is the Council of Lääne-Harju Rural Municipality; 

– for use of construction works one must have permit for use of construction work issued on the basis of Building Code;

– Superficies Licence for building onto the seabed which will be followed by application for construction permit. For construction the sea water intake it is necessary to build artificial island with the basis square of ca 12 ha. Decision-maker is the Technical Surveillance Authority;

– Permit for special use of water for sinking the solid substances onto the seabed and for taking water from the sea and for directing water back to the sea. The decision maker is the Ministry of Environment / Environment Agency.

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