A sand-based thermal energy storage system developed by a Finnish company could enable easier access to affordable and clean energy.
Working with Vatajankoski, an energy utility based in Western Finland, the company, Polar Night Energy has constructed a steel container featuring their patented heat storage system inside. Located in Vatajankoski’s power plant area, the energy storage system provides heat for their district heating network in Kankaanpää.
Polar Night Energy’s innovative ‘sand battery’ is the world's first commercial solution to store electricity in the sand in the form of heat to be used in a district heating network. The company specialises in designing and building high temperature and zero emission heat storages.
The sand-based system enables the storage of renewable energy when energy production conditions are favourable. The stored renewable energy can subsequently be used during winter, replacing fossil-based combustion technologies that are commonly used in heating and electricity production. The current energy crisis brought about by the Russia-Ukraine war has shifted focus to renewable energy.
“The construction of the storage went well, especially considering that the solution is completely new. We managed to get everything in order despite some challenges and a short delay. Now the sand is already hot,” Polar Night Energy’s co-founder and CTO Markku Ylönen said.
Measuring 4 metres wide and 7 metres high, the steel silo has an automated heat storage system and a hundred tonnes of sand inside. As a material, sand is durable and inexpensive and can store a lot of heat in a small volume at a temperature of about 500–600 degrees Celsius, the company stated.
The heat storage has 100 kW of heating power and 8 MWh of energy capacity.
“This innovation is a part of the smart and green energy transition. Heat storages can significantly help to increase intermittent renewables in the electrical grid. At the same time we can prime the waste heat to usable level to heat a city. This is a logical step towards combustion-free heat production,” Ylönen explained.
Vatajankoski uses the heat provided by the storage to prime the waste heat recovered from their data servers, which are intended for high-performance computing. Depending on the season, the temperature of the 60-degree waste heat from the servers must be raised to 75–100 degrees before it is fed into the district heating network.
Mission Innovation, a global initiative of 22 countries and the European Union, has assessed that the potential avoided greenhouse gas emissions enabled by Polar Night Energy’s heat storage system is 169.8 Mt CO2e per year in 2030.
“It means that according to the estimate our heat storages could potentially save almost double the CO2e emissions of today’s New York City,” Polar Night Energy’s CEO Tommi Eronen said.
“It is great to see that our company has been recognised as having potential to really make a big impact for a carbon neutral world,” Eronen added.
