World’s largest cavern thermal energy storage to be built in Vantaa

Innovative energy storage solutions will play a key role in the carbon-free energy systems of the future. The VECTES (Vantaa Energy Cavern Thermal Energy Storage) is a seasonal energy storage project, which enables harnessing the warmth of summer for the cold winter days. The facility will be the world’s largest cavern thermal energy storage with 1,000,000 m3 in size. It will have a storage capacity of 90 GWh of energy – the annual heat consumption of a medium-sized town.

VECTES answers to the challenge posed by the increasing share of variable renewable energy sources. Seasonal fluctuation of energy demand and generation is significant and the supply of renewable energy cannot meet peak demand. Seasonal storage makes it possible for excess heat to be stored in the summertime and used to cut the demand peaks during high-demand days in the winter. The seasonal storage will be charged with energy in the summer that is either renewable or would otherwise be wasted, such as waste heat from air conditioners, solar and geothermal.

This state-of-the-art project is a major milestone in on the path to fossil free production in Vantaa. Stored energy replaces natural gas usage in winter, reducing district heat’s CO2 emissions by 26 000 tons per year. The facility will contribute to multiple policy objectives of the European Green Deal: increasing resource-efficiency by exploiting waste heat sources, accelerating the integration of renewable energy generation and enabling the full integration of different energy systems.

The feasibility of the facility is based on the unique and innovative storage of hot water at exceptionally high temperature of 140°C, a solution which enables larger storing capacity while being cost-efficient. The application is very competitive and scalable also to other regions, thus contributing to the decarbonization of energy systems across Europe. Planned completion of the project is in 2026.