Varanto - VECTES
Giga-CTES in Finland

Varanto – VECTES (Vantaa Energy Cavern Thermal Energy Storage) is a project building the worldwide largest cavern thermal energy storage (CTES, volume of ~1 Mio. m3, capacity of 90 GWh, pressurised, 140°C max. storage temperature, Fig. 1.2b) servicing the Vantaa DH system (591 km grid length). Down to a depth of ~60 m, four equally sized caverns (horizontal: 370 m, 18 m, vertical: 35 m) will be excavated in 2024-25 and the project is planned to be completed and in operation in 2026/27. 

In Vantaa Energy’s journey towards zero-emission energy production amidst the challenges posed by variable renewable sources like wind and solar power, effective energy storage emerges as a crucial solution. The adoption of thermal energy storage, including a seasonal system, plays a pivotal role in this transition. Notably, surplus heat generated from waste-to-energy processes is harnessed to replace natural gas during peak heating demand in winter. The strategic storage of waste heat not only enhances resource efficiency but also allows for the redistribution of surplus energy, reinforcing Vantaa Energy’s commitment to sustainable practices. This innovative approach positions the company at the forefront of environmentally conscious energy production, fostering a future marked by efficiency and reduced environmental impact.

Thermal-mechanical simulations of the ground have been performed, with the exclusion of convective groundwater effects, to ensure that any potential induced ground deformations are minimal, such as regional ground heave on a millimetre scale. A standard environmental impact assessment has been initiated to incorporate this aspect and secure approval for the project. Additionally, preliminary discussions have been held with both public and private partners regarding the potential reuse of excavation material, aiming to substitute rock extracted from quarries.