Hot sand for cold nights

Ville told WoW! News: "When we use renewable energy we cannot control how much the wind is blowing and the sun is shining. There will always be moments when there is not enough wind power and not enough solar power.”

That's why Ville and his team have come up with a way to store renewable energy by turning solar or wind-generated electricity into heat that can be kept in reserve until it's need to be pumped into people's homes to keep them warm.

Giant sand castle!

If you've ever walked barefoot on a sandy beach on a sunny day, you've maybe noticed how it can almost burn your feet. That's because sand is good at holding its warmth.

Ville's team had the idea to fill a silo - a high tower made of metal - with sand. Just ordinary sand. At times when the local solar panels or wind turbines are producing more electricity than is needed immediately, that electricity is used to heat the silo of sand, basically like you heat an electric radiator - or a Finnish sauna... The sand stays hot so that, at night, they pump air through it and the heated air is then pumped into people's homes to warm them.

A town warmed by green power

For several months, the town of Kankaanpääest, has been heated using this giant sand castle. And now bigger cities are looking seriously at installing "sand batteries" made by Ville's company Polar Night Energy. Like the batteries you're used to using every day, they store energy. But unlike normal electric batteries, they don't need rare and expensive minerals. Plain sand could be a really good, cheap way of storing green power.  

That's what Ville and his friends hope. They remember the cold winters when they were children, when the temperature in Finland regularly stayed far below zero and they played ice hockey on frozen ponds. Today, Finnish winters are milder, thanks to global warming. But Ville hopes that his work means his children can enjoy the world in the way that he did when he was little.