Check Out This Sand Battery That Can Store Heat for Months on End

Check Out This Sand Battery That Can Store Heat for Months on End
Image: Polar Night Energy

Engineers in Finland have developed a new thermal energy storage solution: a big silo stuffed with sand. Hell yeah, we love a sand battery.

As originally reported by the BBC, the sand-based high-temperature heat storage solution is now in operation at the Vatajankoski power plant area in Finland. It’s the first sand-based energy storage solution to be developed by Polar Night Energy, a Finnish energy company.

The energy storage system provides heat for the Vatajankoski district heating network in Kankaanpää. It’s not an electricity storage system.

“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,” says Markku Ylönen, the co-founder and CTO of Polar Night Energy.

“We have already learnt that our system has even more potential than we initially calculated. It’s been a positive surprise.”

The battery storage system involved a four-metre-wide, seven-metre-high steel container, with hundreds of tonnes of sand stuffed inside. Polar Night Energy says that sand makes a durable and inexpensive heat storage solution, capable of storing a lot of heat in a small volume, at a temperature of 500-600 degrees celsius (roughly one-third of the temperature needed to make glass from sand, 1,700 degrees celsius). The company claims that it’s capable of 100kW heating power and 8MWh of energy capacity.

But why would you want to store heat? Well, let’s let Ylönen explain:

“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.”

Here’s a quick explainer of how it works: the silo sand is warmed up by resistive heating, which generates hot air that circulates in the sand through a heat exchanger.

When electricity prices rise in the district, heat is expelled from the silo and sent into the district heating system, making its way around Kankaanpää. It’s a solution that adds flexibility to the heating system of the area, alleviating the pressure placed on both fossil fuels and renewables.

But, again, it’s not intended to be an electrical battery, but a heat battery. As pointed out by the BBC, when you convert the heat to electricity, the efficiency falls dramatically.

But this does posit a good case for heating systems not requiring direct and high-cost energy from the grid, with the ability to store heat for months on end.

Right now I’m wearing an Oodie with an oil heater blasting beside me, surrounded by LEDs. It’s pretty cold in Sydney, so I, for one, reckon this sand battery could have a positive future.