Storing heat in sand
01 – What is it
The sand battery is an ecological innovation that brings us one step closer to carbon-neutral district heating. The world’s first commercial solution stores electricity in the sand as heat of around 500-600 Celsius degrees, which can be fed into the district heating network. The innovation that reduces emissions from fossil fuels has brought many contacts around the world.
Vatajankoski and Polar Night Energy have built a heat-storing sand battery in Kankaanpää as a pilot project. It can be used to reduce industrial energy costs and risks related to energy availability and price fluctuations.
02 – How it works
The sand battery can be used in any area of the electricity network, and sand is a durable and inexpensive material. The actual heat storage is a steel tank, and Installed inside it, there is an automatic heat transfer system patented by Polar Night Energy. The tank is filled with sand and the thermal storage is connected to the electricity and district heating networks.
For example, in a machinery shop metal pieces can be heated in an oven at 300–500 degrees using LPG. With the help of the sand battery, a closed cycle can be created, where hot air is circulated from the sand battery heated by electric resistances to the oven. The cooled air is led back to the sand battery or fed into the district heating network instead of ending up as waste heat in the air.
03 – How it can be used
For applications where high-temperature energy is needed, for example in the wood and construction industry, bakeries, laundries and machine shops, a sand battery can be a viable solution. The heat demand of industry in Finland alone is twice as much as the use of district heat, so the emission reduction potential of the sand battery is huge.
The high temperature provided by the sand battery can be used to replace, for example, liquid or natural gas used in an industrial furnace. The sand battery also works in locations where inexpensive night electricity cannot otherwise be used or where it is difficult to achieve emission reductions due to the need for high temperatures. The cheapest hours of the week in terms of electricity price can be used to charge the sand battery.
- Sand is a durable and inexpensive material, and a lot of heat can be stored in it in a small capacity
- In sand batteries, the core is heated to around 500 Celsius degrees, the edge temperature is 150–200 degrees
- The heating power of the thermal storage, implemented as a pilot project, is 100 kW and the storage capacity is 8 MWh. It provides heat to the Kankaanpää district heating network
- The actual heat storage is a steel tank about four meters wide and seven meters high
- Polar Night Energy’s patented automatic heat transfer system is installed inside the steel tank
- The steel tank is filled with sand and the thermal storage is connected to the electricity and district heating networks