In Finland, Vaanta Energy is developing the project for the world’s largest underground system storage system. The company plans to create underground caves with a total energy capacity of 90 GWF to provide heating to the entire city throughout the year (source).
With the increasing use of renewable energy sources like wind and solar plants, the need for effective energy storage is crucial. Unlike battery storage systems that are suitable for small-scale use, industries require large-scale solutions. Vaanta Energy aims to store thermal energy innovatively using underground caves.
Finland is a leading producer of thermal energy for central heating systems in the EU. In 2023, the country produced 37.3 tweads of heat, with over 50% coming from renewable sources and 14% from heat energy waste.
The Varato project includes the creation of three caves, each measuring over 300 meters in length, 40 meters in height, and 20 meters in width, located 100 meters underground to form the world’s largest storage system of its kind, with a total volume of 1,100,000 m3, including technological premises.
During times of excess renewable energy production, the caves will be filled with hot water using two 60 MW boilers to maintain high pressure, allowing water to be heated to 140 ℃ without evaporation.
The system will also utilize industrial heat waste for heating water, operating as a hybrid system that switches between electricity and other energy sources based on cost-effectiveness. Varato has the capability to store thermal energy equivalent to charging 1.3 million electric vehicles, ensuring energy security and environmental stability in the region.
The estimated cost of the project is €200 million, with construction expected to begin in the summer of 2024 and completion targeted for 2028. While specific heating costs are undisclosed, the project is anticipated to significantly reduce energy expenses and provide stable, eco-friendly heat supply.