A (don't laugh) 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 fioul (do you know what that is?)
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.
Intelligence and flexibility: an accumulation that follows the market
A distinctive aspect of the system is its ability to adapt to electricity prices. The system monitors market trends and plans charging cycles at the most convenient times, thus optimizing economic efficiency as well as energy efficiency. A battery that not only stores heat, but also opportunities.
The construction of the battery involved dozens of companies and over a hundred workers. It is a model ready to be adopted in other similar realities. The infrastructure demonstrates that simple technologies, local materials and careful planning can make a difference.
Heat from Sand: A Signal for the Future
La sand battery by Pornainen is not just a technical installation. It is a message: the future of urban heat can be born from accessible, robust and sustainable technologies. An idea that brings together industrial waste, ingenuity and political will, and that shows how sand can heat more than we imagine.
For more details: polarnightenergy.com.
