World’s largest sand battery inaugurated

The world’s largest Sand Battery has been officially inaugurated. Developed by Polar Night Energy, this industrial-scale Sand Battery has been serving as the main production plant for the Pornainen district heating network since June.

“A couple of years ago, we started considering how to take district heating in Pornainen to the next level. It would have been easy to simply replace the old woodchip power plant with a new one of the same kind, but that didn’t align with our goals. We evaluated every possible alternative, and the Sand Battery proved to be the best option,” said Mikko Paajanen, CEO of Loviisan Lämpö, in his speech.

A Sand Battery is a high-temperature thermal energy storage system that stores affordable and clean electricity as heat in sand or other solid materials. It solves many of the challenges of the energy transition.

The Pornainen Sand Battery has performed as expected and in its first months has even exceeded its guaranteed efficiency targets. The old woodchip plant hasn’t been used at all this summer.

The inauguration was carried out by the Finnish Minister of the Environment and Climate Sari Multala, who highlighted the significant potential of thermal storage to improve the flexibility of the energy system and reduce industrial emissions.

“Energy storage plays an important role in the energy transition, where combustion-based production is phased out and society moves towards carbon neutrality. The Pornainen Sand Battery is a great example of how the clean transition can be advanced through the electrification of district heating networks,” said Minister Multala in her speech.

The municipality of Pornainen has been involved in the project from the start. A large share of the municipality’s own buildings, including the school, town hall and library, are connected to district heating.

“It is a great honor for Pornainen to host the world’s largest Sand Battery. One of our strategic goals as a municipality is carbon neutrality, and the Sand Battery plays an important role in achieving that. We are delighted that Minister Sari Multala came to our community to inaugurate this groundbreaking innovation,” said Antti Kuusela, Mayor of Pornainen.

Huge Potential from an Investor’s Perspective

Loviisan Lämpö is owned by CapMan Infra, part of the private equity firm CapMan. From an investor’s perspective, Sand Batteries hold enormous potential: they can participate in electricity reserve markets, reduce dependence on single energy sources in heat production, and serve as an excellent example of sector integration between electricity and heat.

“For us, the Sand Battery is of course a great commercial investment, but we also wanted to boldly support an innovative solution that benefits customers, the municipality, and the entire electricity market. This is a concrete example of a cost-efficient and sustainable investment. And if it works here, it will work anywhere,” said Sauli Antila, Investment Director at CapMan Infra.

The profitability of the Sand Battery is based on charging it according to electricity prices and Fingrid’s reserve markets. Its large storage capacity enables balancing the electricity grid and optimizing consumption over several days – even weeks. The reserve market operations and optimization of the Pornainen Sand Battery are managed by Elisa’s international software unit, Elisa Industriq.

“The Pornainen plant can be adjusted quickly and precisely, and it also has a remarkably long energy buffer, making it well-suited for reserve market optimization. Our AI solution automatically identifies the best times to charge and discharge the Sand Battery and allocates flexibility capacity to the reserve products that need it most. Continuous optimization makes it a genuinely profitable investment,” said Jukka-Pekka Salmenkaita, Vice President of AI and Special Projects at Elisa Industriq.

Polar Night Energy acted as the project’s main contractor and delivered the Sand Battery to Loviisan Lämpö as a turnkey solution.

“The facility is now operational and providing affordable district heating for the clients. We’ve shown that cost-effective solutions for electrifying heating do exist, it just takes courage to invest,” said Liisa Naskali, COO of Polar Night Energy.

Polar Night Energy has a clear vision for the future. Construction of an electricity production pilot will begin in the coming weeks in Valkeakoski, Finland, and the company is in active negotiations for several large-scale thermal storage projects in district heating, hot air, and process steam production.

“Industrial applications are particularly promising, especially where heat above 100°C is required, something electric boilers and heat pumps cannot provide,” added Naskali.

The inauguration of the world’s largest sand battery was celebrated on Monday, August 25, 2025, in Pornainen, Finland.