This is an excerpt from an article featured in ATMOsphere’s “Clean Cooling for Data Centers 2025” report, which can be downloaded here. ATMOsphere is the publisher of NaturalRefrigerants.com. You can read part 1 of this story here.
To better address sector-specific needs, Fenagy is developing tailor-made modules that meet data center safety and redundancy requirements. These standardized yet customizable units can operate in cooling-only mode when heat recovery is not required or in combined mode when both cooling and heating demand exist, similar to the company’s existing heat pumps and chillers.
Around 90% of Denmark’s future data centers are expected to be built on the west coast, near offshore windfarms but away from major population centers. While this provides cheap renewable power, it limits opportunities for heat reuse due to the remote location. To serve such facilities, Fenagy is developing system concepts that integrate free cooling with mechanical cooling to maximize flexibility.
“If you don’t have any need for the heat, you might as well use free cooling and avoid work on a mechanical compressor or chiller,” said Klaus Hoberg Jensen, Sales Director of Industrial Refrigeration and Heating at Fenagy.
Fenagy has said it sees enormous growth potential in aligning Europe’s booming data center sector with its push to decarbonize heating through district heating networks. The manufacturer is currently engaged in six large data center projects, mostly in Denmark and Finland, covering installed IT power capacities of 10–30MW. A potential 200MW hyperscale facility project is also in early planning.
“To enable the data center business case, they’re building a completely new industry next to it,” said Hoberg Jensen. Within the next three to five years, Fenagy expects data centers to represent as much as 25% of its total business due to the size of the projects and systems.
Entering the data center sector
Fenagy’s first data center project is located in Kajaani, Finland, where an existing colocation facility is being expanded to provide additional server capacity. The installer on the project is Caverion.
The first phase of the project targets 13.5MW of IT power capacity matched by approximately 13.5MW (3,838TR) of cooling capacity. The heat pumps capture the resulting waste heat and reuse it in the local district heating network, delivering roughly 18MW (5,118TR) of heating output. Across operating conditions, the heating COP is expected to be between 4.2–5, with “the same scalability for the full installation,” according to Hoberg Jensen.
Previously synthetic chillers provided cooling for the facility’s servers, and excess heat was rejected via dry coolers. The expansion project replaces this setup with Fenagy heat pumps that cool the servers and recover waste heat for use in the city’s district heating network, which is operated by the local energy company.
While the new heat pumps can handle the facility’s full cooling load, its original chillers and dry coolers will remain in place to provide additional redundancy and cover cooling demand during periods of reduced heating demand. The 18MW installation, scheduled for completion in early 2026, is the first phase of a larger 30MW upgrade. Once operational, the 18MW of waste heat will provide heating for roughly 3,500 households in the local community.
“It was a straight-up competition that we won on the basis of having the best technical solution, price and COP.”
Klaus Hoberg Jensen,
Sales Director of Industrial Refrigeration and Heating at Fenagy
System design
Fenagy supplied six customized HCI-3000 units, each incorporating three independent refrigerant circuits – two using isobutane and one using propane. All three circuits have a charge of 50kg of refrigerant each. The modular approach ensures high reliability, according to Fenagy.
The units provide 20°C (68°F) water for server room cooling independent of the return temperature from the district heating network, which is about 50°C (122°F). The system then lifts waste heat from the cooling loop from around 30°C to 85°C (185°F) to meet the district heating network’s requirements. Fenagy’s hydrocarbon solution was selected in an open public tender against HFC and HFO competitors, despite Finland having no bans or restrictions on synthetic refrigerants at the time.
“It was a straight-up competition that we won on the basis of having the best technical solution, price and COP,” said Hoberg Jensen. “With HFCs and HFOs, it’s going to be difficult to deliver 85°C.”
