An energy partnership in Finland recently installed the first fully operational “sand battery” in the world. The innovative technology can store green power for months on end, and its developers say it may solve the problem renewable energy has with power sources that are only available seasonally.
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The sand battery “charges” low-quality sand with heat made from relatively low-cost solar or wind-generated electricity. It can store heat at approximately 500 °C, retaining it for months in order to keep homes warm in winter.
Collaboration and Innovation: Polar Night Energy and Vatajankoski
The sand battery was constructed by Finnish startup Polar Night Energy alongside Vatajankoski, a Western Finland-based energy utility. The project has delivered the first commercially viable sand-based energy storage solution anywhere in the world.
The battery uses a patented heat storage system developed by Polar Night Energy. This system was placed on Vatajankoski’s power plant facility to provide thermal energy for Vatajankoski’s district heating network in the Western Finland district of Kankaanpää.
The system uses low-cost renewable electricity to heat sand up to 500 °C in a technique called resistive heating. This is the same method that electric fires use to generate heat from electricity.
The hot air that this generates is circulated through the sand in a heat exchange system.
The team reported that the project’s construction phase went well, especially when the novelty of the solution was taken into account. During the project, engineers discovered that the system had even more energy storage capacity than they had originally calculated.
Heat is contained within a 4 m wide and 7 m high steel container that contains Polar Night Energy’s automatic thermal energy storage system and 100 tons of low-grade sand. The sand used is durable and cheap, and it can store a lot of heat when it is contained in a small volume and heated to around 500 °C or 600 °C.
The sand battery has the capacity to store around 100 kW of heating power in addition to 8 MWh of energy storage.
The project was a part of a smart and green transition for Finnish energy distribution. Heat storage systems like this one could contribute significantly to making the most out of seasonally intermittent renewable energy sources in the national electric grid.
Heat stored in large, commercial scale systems like this one can also help move cities toward combustion-free heat production in the future.
Vatajankoski, the Finnish energy utility that is partnering with Polar Night Energy on the sand battery project, is using the heat provided by the system to prime waste heat that they have recovered from data servers.
This waste heat is only around 60 °C, but the excess heat from the sand battery can be used to raise it to around 75 °C to 100 °C and feed it into the firm’s district heating network.
Could the Sand Battery Replace Conventional Batteries?
Currently, most industrial-scale batteries used for storing electricity from intermittent renewable energy sources are made out of lithium. They are bulky and expensive and do not cope well with large amounts of excess power.
The sand battery, on the other hand, is a low-cost solution that does not require new, rare materials, and that can withstand significant power surges. Sand batteries can also quickly store high surges of energy from renewable sources, maximizing efficiency in the system.
Sand loses little energy over time, and can store heat in a sand battery for several months at 500 °C. This means that the battery can discharge hot air when energy prices are higher, enabling the district to heat homes, offices, and the local swimming pool at a much lower cost.
Meeting the Need for More Renewable Energy Storage Capacity
The sand battery has been introduced at a time when electric grids and utility companies around the world are investing heavily in renewable energy. Solar farms, wind turbines, and geothermal energy systems are springing up in great numbers all around the world, with significant improvements in renewable power technology and cost in recent years.
But increasing the renewable energy generation capacity to a national grid is only part of the solution. Storage is just as important, especially in regions more affected by seasonal weather changes such as northern Europe.
Electricity grids need to maintain balance in the network, so adding a surge of power from renewable sources – for example during a storm when wind turbines are at full capacity – could actually disrupt the network.
Effective battery storage can help engineers (and, increasingly, automated systems) maintain balance in the grid by absorbing power surges and releasing that energy later when the grid needs it.
Sand is being investigated by research groups around the world, in addition to the Finnish partnership. The US National Renewable Energy Laboratory (NREL), for example, is researching sand batteries right now.
With the first working commercial sand battery in place, it may only be a matter of time before this low-cost, efficient technology becomes commonplace in the world’s electricity grids.
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References and Further Reading
McGrath, M. (2022). Climate change: 'Sand battery' could solve green energy's big problem. [Online] BBC News. Available at: https://www.bbc.co.uk/news/science-environment-61996520 (Accessed on 7 July 2022).
The First Commercial Sand-based Thermal Energy Storage in the World Is in Operation – BBC News Visited Polar Night Energy. (2022) [Online] Polar Night Energy. Available at: https://polarnightenergy.fi/news/2022/7/5/the-first-commercial-sand-based-thermal-energy-storage-in-the-world-is-in-operation-bbc-news-visited-polar-night-energy (Accessed on 7 July 2022).