A Finnish startup – Polar Night Energy – has revealed technology which can use renewable energy to make sand really hot, so the heat can be used in homes when it’s not sunny or windy.
The new heat storage system is a 23-foot steel silo filled with over 100 tons of low-grade sand (which isn’t suitable for construction).
The company then blows hot-air blown through a system of pipes to heat up the sand. Once heated, the sand is able to hold around 500–600C of heat for months at a time.
This means that energy generated by renewables in the hot summer months can be used to heat homes in winter. That translates to about 100kW of heating power and 8Mhw of energy storage capacity.
Polar Night Energy teamed up with Finnish utility Vatajankoski to build the world’s first commercial sand-based high-temperature heat storage system.
The prototype facility is located in Kankaanpää. In future it the silo would be connected directly to solar and wind power sources, but initially the plant was powered by the Finnish grid and waste heat from a neighbouring data-centre.
The site uses power when prices are cheap to heat the sand, but when prices rise the system is then used to heat water for the local districts municipal heating system. This means water warmed by the plant is then pumped into local offices, houses and the town swimming pool.
Solutions like this are critical to transitioning to greener energy sources. Renewables are criticised for their lack of on-demand power. Being able to store renewable energy when it produces surplus energy is a logical step to to ensure that power is provided where needed from green sources.