iM3
Summary
Designed and built by Polar Night Energy, Finland, the battery uses 100t of sand to store and supply low-emission district heating in a town called Kankaanpää. It has 100kW heating power and 8MWh of capacity, and heats residential and commercial buildings, including a municipal swimming pool.
Energy utility firm Vatajankoski uses the storage to prime waste heat from their data servers. The 60°C waste heat is raised to 75-100°C before being fed into the district heating network.
Beyond this application, the sand battery concept works as a high-power and high-capacity reservoir converting excess solar and wind energy to heat, where 70% is stored at 300-500°C and can be used to heat homes or provide process heat to industry.
As sand heat storage can store several times the amount
of energy as a similar sized water tank, it is considered a more efficient method of heat transfer.
The sand in this instance is stored in a 7x4m insulated steel silo with heat transfer pipes and charged when clean and cheap electricity is available – with electrical energy transferred to heat storage using a closed loop air-pipe arrangement. Air is heated using electrical resistors and circulated in the heat transfer piping.
Heat is extracted by blowing cool air through the transfer pipes, with the air heating up as it passes through and converts water to process steam or district heating in an air-to-water heat exchanger. Chief Technology Officer of Polar Night Energy, Markku Ylönen, says, 'Our storage temperature is so high that we have no issues in providing heat for homes. We can provide 200°C steam for industries with the same principle, so temperature levels at residential systems are low in our perspective.
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