A startup company from Tampere, Polar Night Energy, specializes in implementing high-temperature thermal energy storage systems. Their sand-based thermal energy storage, designed for commercial use, was the first of its kind in the world. Currently, Polar Night Energy is pursuing significant growth both in Finland and across Europe. With the help of Berggren, this new, innovative solution has been patented in a sufficiently broad scope, leaving space for future product development.
Polar Night Energy designs and projects the thermal energy storage systems entirely in-house. In practice, the thermal energy storage consists of a large mass of sand or sand-like material containing a pipeline through which air flows. Thermal energy is transported in and out via this air. Equipment for heating the air is arranged outside the sand. The air transfers heat to a medium in which it is stored. When there is a need for heat, cool air is blown into the heat storage, and the air gets warmed up as it passes through the pipes within the sand. The hot air can then be directed, via a heat exchanger, to industrial processes or district heating.
– Now that wind power and solar power have seen significant growth, we need something to balance this issue of incidence between energy production and consumption. Large-scale thermal energy storage systems like these are one solution, allowing us to efficiently store large amounts of energy generated, for instance, by wind power, says Markku Ylönen, Polar Night Energy’s CTO and co-founder.
Polar Night Energy’s first commercial sand battery was introduced in Kankaanpää in 2022, and it currently serves around one hundred buildings via the district heating network. The next project is under construction in Pornainen, where a large district heating storage is expected to supply over half of the town’s district heating.
– The Pornainen thermal energy storage will have a capacity of approximately 100 megawatt-hours, with an annual throughput of around thirty times that amount of energy. The plan is to scale it up about tenfold, which we see as the standard size – around a gigawatt-hour thermal energy storage, Ylönen sums up.
Polar Night Energy was started when Ylönen and his then-fellow student, now CEO and co-founder Tommi Eronen, began exploring how to store energy from solar or wind power. Both were studying environmental and energy technology as well as power plant engineering.
– During our studies, Tommi and I often discussed over coffee what it would take to build a self-sufficient, combustion-free energy community. We became interested in energy storage and began discussing in more detail what would be required if, say, we stored all necessary thermal energy for the entire winter. That conversation went far enough for Tommi to make it his thesis topic. I was working on my dissertation in France at the time, and we agreed that once I returned, we’d start a company if we found a good angle. In the spring of 2018, we decided to establish the company and develop this idea into a business,” Ylönen recalls.
For Ylönen, natural sciences and environmental protection have always been close to his heart. Even before founding the company, he wanted to do something to reduce energy production through combustion. Polar Night Energy and its thermal energy storages have proven a good method for this. Although the thermal energy storage itself is not a means of energy production, it allows solar and wind power to be scaled up significantly.
– Polar Night Energy is currently at a stage where we are aiming for aggressive sales growth. Besides Pornainen, we are also negotiating projects elsewhere in Finland and Europe, Ylönen sums up.
In the spring of 2024, Polar Night Energy raised €7.6 million in a Seed funding round. The funding has enabled the company to grow and hire new staff. It has also allowed the development of new technology to convert electricity into thermal energy, to store the thermal energy, and then to convert it back into electricity.
– To date, we have returned energy in the form of thermal energy. By modifying our current product, we intend to make a structure by which we can generate thermal energy suitable for existing turbines. This will allow our thermal energy storage to meet the operational requirements of the turbine world and deliver cost-effective solutions, with an efficiency high enough to help balance the electricity market. For example, a storage unit could be connected to a wind farm, absorbing part of the electricity when prices are low and returning it as electricity when prices are higher. This also supports the balance management of wind farms, Ylönen explains.
Polar Night Energy has collaborated with Berggren since almost the beginning of its business. When they were confident about the technology, they contacted Berggren.
– We received a recommendation for Berggren from one of our founding partners, Mikko Paananen, who specifically recommended Virpi Noponen. From the beginning, we worked with Virpi to assess the patentability of our technology. First, we prepared and filed a patent application for Finland. In addition to the granted Finnish patent, we have protected our technology internationally, with the US patent already approved, Ylönen celebrates.
– The primary reason we sought a patent was that, for a startup, it’s a significant credibility factor to have something others haven’t developed that can be patented. The patent greatly enhances our credibility, and it has certainly contributed to our success in the funding round. Another important reason was to make sure that no one else had patented a similar product, and we could protect ourselves with the patent, Ylönen continues.
For a startup, patent applications and the entire patenting process have been a substantial financial investment. Ylönen has a positive impression of how Berggren has understood their position from the start and used that insight to build the patents wisely.
– When Tommi and I began assessing patentability with Berggren, we didn’t know much about patents. We only had the invention. Patents are a whole world of their own, and we’re very satisfied with how Virpi has handled it. She not only wrote the patent texts for us but also explained what is being sought at each stage and suggested the arguments that would strengthen our patent’s chances of success, Ylönen commends.
– Virpi’s excellent grasp of the invention’s technical and scientific aspects has been essential in drafting and successfully applying for the patent.
For Polar Night Energy, particular consideration has been given to the scope of each element covered by the patents. For example, the medium used for storing of thermal energy was specified in the patent application to cover any solid granular material.
– Sand is a good material to start with, but it’s fully expected that we’ll develop some alternative media as well. The thermal energy storage is designed to accommodate any material with suitable thermal properties. We identified areas in the patent where broad protection was essential and where a narrower scope would suffice. In this way, we ensured that when the product is developed further, the patent will still cover these improvements. We’ve succeeded very well in that regard. Although the basic heat transfer concept remains the same, the patent allows for a wide range of applications in how we ultimately implement the heat transfer, Ylönen says.
Despite the considerable financial investments required by the patenting process, Ylönen believes it has been a worthwhile investment for Polar Night Energy. He encourages other startups to invest in protection if they have a clearly defined new invention and a patent could benefit their operations.
– The path to patenting has been absolutely worthwhile for us, even though we haven’t always been sure where it would lead. Although it’s a significant financial commitment, if you lack experience, it can take a thousand times longer than it would for a patent attorney, and the result may still be suboptimal, Ylönen concludes.
For Ylönen, the most important aspect of working with Berggren has been their client focus, especially in understanding Polar Night Energy’s position and needs. Future collaboration is also planned, not only with ongoing patent applications but also with new technology to convert thermal energy back into electricity.
– Our cooperation with Berggren has been smooth from start to finish. They’ve acknowledged that we started with little understanding of patents. The partnership has provided us with the essential information when needed, and we appreciate that Berggren keeps us informed and reminds us well ahead of deadlines. We’ve come to trust that with them, our patent is in good hands, even if we don’t think about it for several months. We don’t need to worry much about it.
– This has reached the level where if I trust anyone, it’s them. If new patentable inventions arise, we’ll discuss with them whether to proceed. I also trust that if something is better kept a trade secret rather than patented, they’ll tell us. It’s crucial to rely on the patent agency to think about the most valuable and sensible overall outcome, not just to maximize the number of patents, Ylönen concludes.
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Our client experience story has been independently produced by Kokemuksia.fi. Each story has been approved by the interviewed client, and the company featured has had no opportunity to influence the content of the story.