A-Z Site Index

Sand warms up the Finnish polar night

The inhabitants of Kankaanpää in western Finland need not worry about heating during the coming winter as much as fellow Europeans. About a hundred homes, a few offices, and the municipal swimming pool in the town have secured an all-year-round source of heating thanks to an ingenious invention: the sand battery.

The founders Founders_Markku and Tommi
The founders Markku and Tommi. Credit: PNE

Heating is important for Kankaanpää, which has a population of 11,200 souls, as the average temperature from December through March is below zero and can fall as low as -23°C.

The Vatajankoski power plant area has implemented a battery made of ordinary sand, the world’s first of its kind.

“The idea is to produce heat that you get via clean energy from the sun and wind. The heat is stored in sand. Sand is cheap and the supply is great,” says Markku Ylönen from the company Polar Night Energy which came up with the idea.

500 degrees

The term sand battery is greatly simplified but describes hundreds of tons of sand heated to around 500°C in a steel container. This then serves as a heat source. The energy, which comes from renewable sources such as wind and hydropower, is stored to allow the heat to be used on darker and colder days when the energy supply is lower. Since its launch, the company’s idea has attracted a lot of attention, not least via the Youtube channel “Now you know” and a viral news clip produced by the BBC. Renewable energy is a hot topic.

“Heat and energy sources are a growing market,” says Markku Ylönen. “We have mostly received positive feedback, but certainly the success has brought with it criticism as well. It is correct that people question this, that is how it should be. At the same time, publicity is a very good tool.”

Renewable energy

Sustainable Development Goals
Sustainable Development Goals

Renewable energy is also one of the UN’s Sustainable Development Goals (SDGs) also called the Global Goals. In the spirit of the Sand Battery, SDG 7 reads “ensure access to affordable, reliable, sustainable and modern energy for all”. A large proportion of our greenhouse gas emissions come from the way we extract, convert and use fossil energy, but renewable energy solutions are becoming cheaper, more reliable and more efficient every day.

Markku Ylönen, from Tampere, together with his colleague and co-founder Tommi Eronen, are engineers with a solid background in energy production. They are also the creative innovators behind the first sand battery for commercial use. Their invention may be the solution to one of the biggest challenges in energy production, namely a source of consistent energy supply all year round.

Solar energy stored in the sand can keep warm for months, which means that heat generated during the summer can help Finns through the long cold winter. Another factor in this context is that it is no longer possible to count on Russia’s gas and electricity supply.

Save energy

Sand is abundant and chepa, and therefore the sand battery is an interesting alternative.
Sand is abundant and chepa, and therefore the sand battery is an interesting alternative. Credit: PNE

The Finnish Ministry of Economic Affairs and Employment plans to launch a campaign in August urging the Finnish population to save energy. Similar campaigns are already underway in many EU countries such as Germany, Italy and France and are an initiative of the European Commission.

The Finnish sand battery is just right in time: green, clean energy stored in sand that is collected locally.

“We don’t want the sand transported from far away,” Markku explains of the plant, which was shipped to the site in January this year, installed in the spring and commissioned in May.

The 4×7 meter steel tank in the Kankaanpää Vatajankoski power plant area contains hundreds of tons of sand that can be heated to a temperature of 500-600°C. The sand can keep warm for months and has 100 kW of heat capacity and 8 MWh of energy capacity distributed

in the district’s heating system. The environmental aspect is a common theme.

When the wind blows

This is how the sand battery. Credit: PNE

“For example, today is a windy day. Then we use that wind to collect energy that we can use on a day when it’s not so windy,” explains Ylönen.

Energy and how to utilise it has long been a special area for Markku Ylönen and Tommi Eronen. The two met during their university years while studying energy production at Tampereen Yliopisto. The idea of starting their own business was born about ten years ago. Other energy sources were discussed, including water and solar, but after solid preparatory work, work began on building the large silo together with the Vatajankoski power plant. According to Markku Vatajankoski the Vatajankoski power plant is an open-minded partner, that has already supported innovative projects and new ideas in the past.

Low cost – great supply

“We planned the business around sand as an energy source for many reasons. Sand costs almost nothing and the supply is great,” explains Markku, adding that even the size of the grains of sand is not of decisive importance, but you can use industrial by-products that are either fine- or coarse-grained.

The corporate name Polar Night Energy derives from the concept of polar night, or midwinter darkness, which means that the sun never rises during the day; that is, the period when the sun is below the horizon.

“The name is meant to show that if there is energy production here for Finland’s darkest periods, there is enough for others as well,” says Markku Ylönen.

Today, the company employs six people and Markku believes that there is room for more employees in due course. Despite the great interest the company has garnered in the media, they have tried to keep the amount of work at a reasonable level. Future plans include both developing and refining existing operations but also expanding.

“Our big goal in the long term is to be able to influence emissions on a global level,” says Markku Ylönen.

Latest news

More from our Engagement Hub