The winner of the 2026 Breakthrough Award, which recognises ideas or innovations that create something new in the field of technology, is Polar Night Energy. The EUR 15,000 award is presented by Academic Engineers and Architects in Finland TEK and Tekniska Föreningen i Finland TFiF.
”Polar Night Energy has developed an innovative and scalable energy storage solution called the Sand Battery. The proportion of clean energy production in the energy system, which varies according to the weather, is increasing and creating demand for various kinds of energy storage solutions. Polar Night Energy’s Sand Battery is based on advanced technology and enables efficient conversion of energy from electricity to heat”, wrote the jury in its assessment.
Photo: Polar Night Energy's team photographed in 2025. Photographer: Kalle Särkkä.
Polar Night Energy is a Finnish company specialising in thermal energy storage solutions.
”Markku Ylönen and I used to discuss energy self-sufficiency, energy price volatility and the need to store energy when we were studying at Tampere University of Technology in the 2010s. It was already clear to us then that increasing renewable energy production would not be enough to decarbonise the energy sector without high numbers of high-capacity energy storage systems. Polar Night Energy was born in 2018”, says the company’s co-founder and CEO Tommi Eronen.
The first pilot was built in 2019, and the world’s first commercial Sand Battery was assembled in 2022. According to the company, it went ‘viral’ straight away. The innovation was featured on, for example, the BBC and the CNN.
Polar Night Energy's Sand Battery stores renewable energy as heat in sand or similar material, which enables longer storage and usability periods than electric batteries. The patented closed-loop heat transfer mechanism stores thermal energy in solid material such as sand. Solid materials are slow to release heat, which helps to keep heat loss from the system low.
”The Sand Battery reduces reliance on energy generated by combustion, enhances electricity grid stability and facilitates the transition to renewable energy. It increases local energy security and energy self-sufficiency”, Eronen explains.
Photo: Polar Night Energy's founders Tommi Eronen and Markku Ylönen. Photographer: Marjaana Malkamäki.
The system can be charged using electricity from the grid or locally produced energy, like wind and solar.
”The Sand Battery delivers affordable energy, such as clean and cost-effective process steam or district heating, as it makes it possible to take advantage of low spot prices and to make additional profits from Fingrid’s reserve markets.”
There are no strict criteria for the type of sand used in the storage system, which means that the material can be, for example, mining industry waste.
”The Sand Battery does not significantly contribute to biodiversity loss, as there is no need to open new mines, which is the case with many other energy storage solutions. Our innovation has huge potential to significantly reduce climate emissions and slow down climate change.”
Polar Night Energy’s technology has already been integrated into district heating systems across Finland. The world’s first Sand Battery was installed at the Vatajankoski power plant in Kankaanpää in 2022.
”We are currently building a two-megawatt Sand Battery for Lahti Energia in Vääksy and a pilot plant of our own in Valkeakoski, where we intend to test the Sand Battery’s ability to convert heat back into electricity.”
In addition to district heating systems, the innovation has potential in other industrial sectors that rely on process heat as well as in the global market.
What started as the vision of the two founding members is now a company employing 27 people.
”Our goal is to become the global market leader in industrial-scale thermal energy storage systems. We plan to expand our customer base from district heating suppliers to other industries and to launch a heat-as-a-service business”, Eronen says, describing what will come next for the company.
Breakthrough 2026: Polar Night Energy
Eronen Tommi
Heikkinen Simo
Heiska Sonja
Hunter-Hill Jaih
Höglund-Dönnes Annette
Kallio Hanna
Kivioja Ville
Kolu Reijo
Kumpulainen Ville
Liimatainen Jani
Lipponen Jonna
Moisala Terhi
Naskali Liisa
Niemi Juha
Niinikoski Jyri
Peltola Miika
Pietarinen Veli-Matti
Santamäki Atte
Suksi Meri
Tanskanen Joni
Toivonen Teemu
Tolvanen Visa
Ulvinen Matti
Varho Teemu
Vilhonen Venla
Ylönen Markku