A 100 MWh sand battery goes into operation in Pornainen: a model that combines sustainability, innovation and farewell to fossil fuels.
A Pornainen, a town of 5.000 inhabitants in southern Finland, has started operating the largest sand battery never realized. A project signed Polar Night Energy and developed for Loviisan Lampo, the company that manages the local district heating. The plant is the heart of a strategy that has been in the works for over three years and aims to eliminate fossil fuels and achieve carbon neutrality by 2035.
The Sand Battery: How It Works
The structure measures 15 meters in diameter and 13 meters high and contains 2.000 tons of crushed steatite, a by-product of the construction industry. The principle is simple: electricity from renewable sources heats the sand to up to 600 °C.
The mass stores heat and releases it slowly, feeding the district heating network and providing thermal energy to local industrial plants. A system that transforms a common material into a reliable heat reserve.
Capacity and record numbers for the sand battery
With a storage capacity of 100 MWh and a thermal power of 1 MW, this sand battery can heat the entire Pornainen for a week in the middle of winter or for a month during the summer, when demand is lower. A full charge takes about four days. This is a significant improvement over to the 8 MWh prototype installed in Kankaanpää in 2022. A leap in scale that marks the transition from experimentation to concrete application.
Reducing emissions and ending fuel oil
The new plant will allow the city to cut annual CO₂ emissions related to heating by 70%: approximately 160 tons less. The use of the oil will be eliminated: it is a liquid fuel derived from petroleum, also known as fuel oil or heating oil, traditionally used to power boilers but responsible for high emissions of CO₂ and pollutants.
The system will also reduce wood chip consumption by 60% by limiting combustion during peak periods. A concrete step towards a cleaner and more stable energy system.
