Savon Voima has taken significant steps towards carbon‑neutral energy production by implementing heat pump solutions developed by Calefa at its power plants in Iisalmi and Joensuu.
At both sites, heat pump technology is used to recover previously unused waste heat and efficiently upgrade it for district heating production.
Impelementation | Iisalmi Heat Pump Solution | Joensuu AmbiHeat solution |
Heat sources | Power plant waste heat + ambient air | Flue gas scrubber condensation heat + river water |
Technology | 1 heat pump | 4 heat pumps |
Capacity | 850 kW | 6 MW + 4–5 MW |
Additional information | Reduces CO₂ emissions by 800,000 kg per year | Awarded Heat Pump City of the Year in autumn 2025 |
Iisalmi Power Plant: Waste Heat Converted into District Heating All Year Round
During the winter season, Savon Voima’s Iisalmi power plant produces district heating and electricity for a city of just over 20,000 inhabitants.
At the Iisalmi power plant, the heat pump system supplied by Calefa improves plant efficiency by utilising process waste heat that was previously discharged into the outdoor air via cooling fans.
With the new solution, the heat pump system takes care of the plant’s cooling needs and upgrades the waste heat directly into the district heating network.
During the summer, when less waste heat is generated, the heat pump system uses ambient air as its heat source. In this mode, the former cooling fans operate as energy collectors, enabling up to approximately ten per cent of Iisalmi’s summer district heating demand to be produced through electrified, non‑combustion‑based generation.
In summer operation, the heat pump system covers around 10% of Iisalmi’s district heating demand and reduces the power plant’s CO₂ emissions by 800,000 kilograms annually.
Overall, the solution improves year‑round energy efficiency, reduces CO₂ emissions, and supports Savon Voima’s goal of achieving carbon‑neutral district heating.
Joensuu Power Plant: Award‑Winning AmbiHeat System with Two Heat Sources
At the Joensuu power plant, Savon Voima and Calefa took the heat pump concept to the next level. The AmbiHeat plant built alongside the power plant utilises two separate heat sources: condensation heat from the flue gas scrubber and river water.
The solution is the first of its kind in Europe and was awarded the international Heat Pump City of the Year recognition in autumn 2025.
During the winter, the AmbiHeat plant enhances the operation of the flue gas scrubber and supplies approximately 7 MW of additional heat capacity to the Joensuu district heating network.
In summer, when combustion‑based production is not required, the heat pump plant switches to using river water as its heat source, efficiently covering a significant share of the district heating network’s summer load without boiler operation.
Flexible Energy Production Ready for Future Requirements
The Iisalmi and Joensuu projects share a common philosophy based on Calefa’s AmbiHeat technology: district heating is produced primarily from existing energy sources, waste heat and the surrounding environment, in the most efficient and low‑emission way possible.
The heat pump solutions complement Savon Voima’s production portfolio, improve power plant efficiency, and reduce dependence on combustion‑based energy production, particularly during the summer season.
The cooperation between Savon Voima and Calefa demonstrates how heat pump technology can be used to modernise existing power plants and gradually build a carbon‑neutral district heating system.
“Multiple heat sources improve heat pump efficiency and enable continuous development of district heating production efficiency throughout the year,” says Kari Anttonen, Business Director at Savon Voima Oyj.
