The core of the innovative solution of Finish start-up Polar Night Energy is its patented high-temperature large-scale heat storage, which can store renewable electricity for months at a time, overcoming a major hurdle in energy storage.
The share of renewable energy sources must increase rapidly in our energy mix to deliver on our climate goals, however, they are highly volatile, and only partly overlap with the consumption in time. Therefore, we need more and more energy storage.
Finish start-up Polar Night Energy (PNE) found a way to combine sustainable heat production with storing excess electricity. Its breakthrough technology provides a way to refine cheap and clean surplus electricity to valuable heat in an affordable way to be used when most needed.
The battery makes use of low-grade sand and can be charged up with heat made from cheap electricity generated using solar or wind energy. The sand stores the heat at around 500 °C and warm homes during winter when energy is more expensive.
“We use sand as the storage medium, which leads to safe operation and a natural balance in the storage cycle,” the company writes about its innovation. “Additionally, sand is a cheap and abundant material, which can be heated up to 1000 °C and even higher.”
Inside the sand, there is a built-in heat transfer system that enables effective energy transportation to and from the storage. Insulation between the storage and environment ensures a long storing period, up to months, with minimal heat losses.
The size of PNE’s storage varies from tens to thousands of cubic meters and they can be placed even underground. Regarding the battery’s carbon footprint PNE says that the heat taken from the storage is as clean as the electricity fed into the storage.
The first commercial sand-based heat storage was built in Vatajankoski, an energy utility based in Western Finland. The full-scale utilisation of the storage will begin this year and it will provide heat for Vatajankoski’s district heating network in Kankaanpää, Finland. The storage has 100 kW heating power and 8 MWh capacity.
There is also a 3 MWh running test pilot in Hiedanranta, Tampere, which is connected to a local district heating grid and provides heat for a couple of buildings. In the pilot, the energy is partly from a 100 square meter solar panel array and partly from the electric grid.
The Finnish energy system is experiencing a rapid transition. The share of renewables in Finland’s total energy consumption has risen from around 27 per cent to approximately 36 per cent in the past decade and according to Finland’s National Energy and Climate Strategy, the goal is to increase the use of renewable energy so that its share in final energy consumption will exceed 50 per cent by the end of 2030. However, innovative solutions in energy storage are needed not only for up-scaling renewables but also to shield against the energy crisis unfolding in the wake of the war in Ukraine and scarce supplies.
As a response to Finland’s decision to join the North Atlantic Treaty Organization (NATO), Russia has halted gas and electricity supplies to the country. In May, Finnish-led consortium, Fennovoima abandoned a contract with Rosatom to build Finland’s third nuclear power plant, which was expected to produce approximately one-tenth of Finland’s electricity need once operational. In this context, innovative solutions are needed more than ever.