The completed thermal storage has a capacity of 80 megawatts. It is 42 meters high and 26 meters wide. The storage can hold 20,000 cubic meters of water. It is like eight large Olympic swimming pools.
The storage is now at its highest point. Soon it will be closed and filled with water. After that, the storage will be covered with a 40 cm thick insulation layer and finished on the outside. The storage is being built by the Swedish company Granitor Rodoverken AB.
The cost of the thermal storage is 8 million euros. Its main purpose is to balance daily fluctuations in energy consumption.
"It is warm during the day, cold at night. This difference can be significant. The storage helps balance daily consumption. We don't have to turn on gas boilers in the morning or shut down base load plants during the day," said Utilitas CEO Priit Koit.
"It is a water storage. It uses a simple principle: hot water rises, cold water sinks. We can heat the water, store it, and use it later when more energy is needed," he added.
How much energy the city of Tallinn receives depends on the time of consumption.
"The main use of the storage is to balance daily consumption. The greatest need is usually in the morning when people take showers. Also in autumn and spring," said Koit.
According to Koit, similar solutions already exist in Tartu and Jõgeva. In addition, two more similar thermal storages are planned to be built in Tallinn.
Green energy is produced in the Väo energy complex. There are two high-efficiency heat and power plants, a heat pump station, and two solar parks. Soon, Utilitas will also open Estonia's first green hydrogen production unit with a filling station in Väo.