For a hundred years, the Kuhankoski hydroelectric plant utilized waste heat from its own generators for heating. In Easter of 2023, the old plant was left in reserve as its replacement became operational. The plant no longer provided the necessary waste heat, requiring another solution that would keep the plant in good working order.

“Kuhankoski is a valuable heritage site. We needed to find a heating solution for the plant, since from that point onwards, it would serve only as a backup, and for the most part, remain unused,” says Hannu Ruotsalainen, who serves as the CEO of Koskienergia Oy.

At the planning phase, Hannu’s team came up with the idea of using waste heat from the new plant for heating the old plant. The biggest challenge was the new plant’s nature as a peaking power plant; sometimes it would stay unused, then run at full capacity, or at any capacity in between, generating a highly variable amount of waste heat.

At the tendering phase, the company investigated if equipment suppliers could offer a heating solution that could adapt quickly to changing conditions.

“For example, not a single hydroelectric set manufacturer we asked for a quotation had experience in anything like this. Finally, we found a simple and insightful solution, which is based on ground source heat pump technology,” Ruotsalainen says.

Oilon’s ground source heat pump is the heart of the heating system

The solution uses the side streams from the new plant’s energy production as the system’s “ground loop”. The heat pump recovers waste heat from generator cooling water, which would otherwise simply be pumped back into the river with the excess heat. The heat is extracted from the cooling system’s secondary side by a heat exchanger. A heat pump transfers the energy to the old hydroelectric plant, which is right next to the new one.

The primary component of the heating system is an Oilon RE 96 ground source heat pump with a 96-kW heating capacity. If the new hydroelectric plant runs at partial capacity or additional heating is required due to, for example, extremely low temperatures, the heat pump is supplemented by four 23-kilowatt air-to-water heat pumps. Additionally, the system has a 107-kW electric boiler as a backup.

“We built the solution offered to Koskienergia around an Oilon ground source heat pump, since the units have proven themselves as high-quality products with extreme reliability. Another thing we appreciate is Oilon’s life cycle services. The unit will serve well for a couple of decades, and the end customer won’t ever have to deal with potential problems alone,” says Sami Päijänen from Lämpöpalvelu Oy, the overall heating system supplier in the project.

“If there is an issue, we have quick access to local support and service – in Finnish, of course.”

The plant was in normal service during installation, which was a major challenge. To ensure safety, careful advance planning was required. As the site itself had a unique heritage, Lämpöpalvelu Oy paid special attention to the appearance and placement of recirculating fans and other visible equipment.

Ruotsalainen praises the end result in every respect.

“Now we can sell all the electricity we produce in the marketplace instead of wasting it on heating. I’d estimate that we’ll save tens of thousands of euros every year. Additionally, this is a great boon for the climate, as the hydroelectric power we produce will hopefully replace energy produced by fossil fuels.”

Learn more about Oilon ground source heat pumps here.