Astounding Finnish Sand Battery

[SorellaLaBefana]

...The Vatajankoski power plant is home to the world's first commercial-scale sand battery. Fully enclosed in a 7m (23ft)-high steel container, the battery con-sists of 100 tonnes of low-grade builders' sand, two district heating pipes and a fan. The sand becomes a battery after it is heated up to 600C using electricity generated by wind turbines and solar panels in Finland, brought by Vatajankoski, the owners of the power plant.

The renewable energy powers a resistance heater which heats up the air inside the sand. Inside the battery, this hot air is circulated by a fan around the sand through heat exchange pipes.

Thick insulation surrounds the sand, keeping the temperature inside the battery at 600C (1,112F), even when it is freezing outside. "We don't want to lose any heat; the average winter temperature is below 0C (32F) in Kankanpää," says Ville Kivioja, lead scientist at Polar Night Energy, who monitors the battery's per-formance online...

Eronen says that with currently available technology the process of converting heat back into electricity only has an efficiency rate of 30%. But he doesn't view that as a major issue. "In a cold country like Finland we're dumping 70% of the heat that remains after conversion on the district heating networks that needs a supply of heat almost all the time," he says.

From the BBC

This is one of the few truly innovative ideas to appear on how energy can be stored with a low adverse environmental impact.