The city of Vantaa in southern Finland has announced plans to build the world’s largest cavern thermal energy storage system. Spread across four main caverns located about 60 metres underground, the seasonal heat storagefacility, known as Vantaa Energy Cavern Thermal Energy Storage (VECTES), will have a total volume of about a million cubic metres, with a storage capacity of 90 GWh of energy – the annual heat consumption of a medium-sized town.
Water, heated to 140°C using a combination of renewable energy and waste heat, will be stored in the caverns, where the groundwater’s natural pressure will prevent it from evaporating, despite the fact that it’s above boiling point.The heat carried by the water will then be used during winter to smooth out any troughs in the city’s power supply that occur when renewable sources are unable to meet peak demand.By replacing the use of natural gas for heating during winter, the district’s carbon dioxide emissions are expected to be reduced by some 26,000 tons per year.
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City energy company Vantaa Energy, which aims to become carbon neutral by 2030, with an interim target of phasing out fossil fuels by 2026, will work with engineering, design and advisory group AFRY and Finnish urban development and construction company YIT to complete the project.The plant’s main design, geotechnical and rock design, structural engineering and process engineering will all be carried out by AFRY.Vantaa Energy hopes to begin construction in autumn 2022 and bring the storage system online during 2026.
‘The seasonal heat storage is a key part of our innovative investment programme, which combines new technological solutions and allows us to phase out fossil fuels in energy production as quickly as possible,’ said Vantaa Energy’s managing director Jukka Toivonen. Vantaa is also considering commissioning a 10 MW power-to-gas plant that will produce carbon-neutral synthetic methane using captured carbon dioxide and green hydrogen.