Wednesday 3 August 2022


While we move away from fossil fuels, it does not make sense to turn to lithium-ion batteries and another mined resource. It is exciting that a simpler method is keeping people comfortable in our high-tech age.

With the gas and electricity disruption to Europe, Finland has designed a heat storage unit that warms peoples’ homes by little more than a steel container filled with sand.

That 'little more' includes solar energy. The sand battery is connected to the grid, turned on in summer and hot air piped through the sand heats it to 500o-600oC, which keeps people warm through the long European winter. This way people in Kankaanpää, a town near Helsinki, warmed their homes, office buildings and public swimming pool by a 7 metre insulated silo and 100 tonnes of  sand.

Finland’s Polar Night thermal energy also delivers high temperature heat for industries, and is a useful replacement for gas, removing up to 16% of emissions. Chief executive officer Markku Ylönen says a bigger battery 20 metres in diameter and 10 metres high can be quickly built in any steel workshop, and on the economics scale 100 times bigger equates to only a 20 to 30 times in cost.

Thermal energy is not new, but until recently burning gas has been cheaper to generate the higher temperatures needed for industry. Australia's ANU Sustainable Energy Systems (SES) Centre is focused on replacing old gas heat pumps with thermal, to deliver greater than 1,000ºC temperatures to factories.

"Stored thermal can be used in food processing, the aluminium industry, cement manufacture, iron and steel, ceramics and plastics," says ANU director Professor Andrew Blakers.

"A few thousand cubic metres of storage will keep a factory running but as thermal storage can't be piped in like gas, factories will need to install their own rooftop systems and build their own storage silos, for heat using cheap daytime solar electricity.”

SES has already patented thermal storage similar to Finland’s using molten silicon instead of sand, and is looking to trial crushed rock and molten salt.

-        Pat Edwards


Published in the "Voices for the Earth" column in The Clarence Valley Independent ,July 27, 2022.