WA has plenty of sun and wind and an abundance of dirt – so what are the chances that a battery made of sand ends up being a part of our energy future? 

It might sound far-fetched but with Finland’s Polar Night Energy recently announcing that it was operating a commercial sand battery, it may not be the stuff of science fiction. 

In fact, the science behind the sand battery is relatively simple and involves very few moving parts. 

Cheap electricity, generated by solar panels or wind turbines, is used to power a heat exchanger which then acts upon sand contained within what is effectively a big (4m-wide, 7m-high) steel tank or silo. 

The storage unit for the heated sand. Photo: Polar Night Energy

Heated up to between 500 and 600 degrees Celsius, the sand is capable of storing 8MWh of energy at a power rating of 100kW.  

The natural properties of the sand means it can retain its “heated-up” temperature for several months, offering the opportunity to cheaply store excess power generated by renewables and use the associated heat later on. 

“Whenever there’s this high surge of available green electricity, we want to be able to get it into storage really quickly,” Polar Night Energy co-founder Markku Ylönen told the BBC. 

The sand battery is currently being put to use at a power plant in the Finnish town of Kankaanpaa, where it’s contributing to the district heating system and even helping warm the local swimming pool. 

It was previously pilot tested in northern 2020-21 winter, heating a couple of buildings in the Finnish city of Tampere. 

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While these early ventures prove the technology works, there are still questions around how applicable sand batteries are for other environments. 

The sand battery concept is particularly well-suited for parts of Northern Finland that see no sun at all during winter but which generate more electricity than needed in warmer months through renewables. The long duration of energy storage means the sand can provide a cheap and clean addition to the heating mix for homes and offices months after it is first put to high temperature. 

But in many parts of Australia, particularly those with a plentiful supply of sun year-round, there isn’t much demand for “district heating.”  

Therefore, the applicability of the sand battery for warmer environments might well rest on industrial uses and the eventual ability to more easily convert the stored heat back into electricity. 

“It’s really easy to convert electricity into heat,” Ylönen told the Disruptive Investing show on YouTube.  

“But going back from heat to electricity, that’s where you need turbines and more complex things.” 

 As for the sand that’s required, it certainly doesn’t have to be anything special. In fact, the inventors say they are happy to use sand that nobody else wants, provided they can access a hundred tonnes of it. 

Leftover sand from the Polar Night Energy battery.