Fenagy CO2 District Heating
Klaus Jensen highlights energy collection using Güntner evaporators.

In 9 Months, Fenagy Built and Connected a 7MW CO2 Heat Pump to a Town’s District Heating Network

With a 13MW system currently in production, Fenagy sees CO2 as a ‘perfect’ fit for the demand for green district heating in Europe.

It took nine months for Danish OEM Fenagy to build, install and commission a 7MW (1,990TR) CO2 (R744) heat pump system for the city of Løsning, Denmark.

“We have a lot of projects like this in our production pipeline,” Klaus Jensen, Sales Director of Industrial Refrigeration and Heating at Fenagy, told Marc Chasserot, Founder and CEO of ATMOsphere. ATMOsphere is the publisher of NaturalRefrigerants.com.

Løsning has a population of 12,680 people, and Fenagy’s new CO2 heat pump will replace a biomass incinerator previously used by the city, with Jensen noting that the biomass system was just one heat source used by the town’s district heating network.

“Instead of burning biomass, we now use renewable energy to heat the city,” he said, adding that a water tank provides the ability to store thermal energy for use during cloudy and non-windy days.

Jensen said the thermodynamic properties of CO2 make it a “perfect” refrigerant for district heating and that Fenagy will deliver a much-larger 13MW (3,700TR) system to a different city in Denmark soon. 

Fenagy produces industrial-sized air-to-water CO2 heat pumps, with individual racks offering up to 3MW (853TR) of heating capacity. The company also manufactures large-scale water-to-water isobutane (R600a) heat pumps providing up to 1MW (284TR) of heating capacity.

System setup

The process of collecting heat from the ambient air starts with the evaporators. In the Løsning system, 18 evaporators designed by Fenagy and produced by German heat exchanger manufacturer Güntner absorb the energy in the air from the evaporation of the CO2 refrigerant.

ATMOsphere marks Güntner as a best-in-class manufacturer of natural refrigerant systems and components around the world with its second annual renewal in January 2024 of the ATMO Approved Natural Refrigerants Label.

Three identical CO2 heat pump racks form the heart of the Løsning system, according to Jensen, with each rack providing roughly 2.3MW (654TR) of heating capacity using 8-cylinder Bitzer compressors.

The heat exchangers/gas coolers on the rack, manufactured by Kelvion, extract the heat energy in the air and transfer it to water. In addition, ejectors, which Jensen said were mandatory for a CO2 heat pump, raise the system’s efficiency.

Depending on the network heating demand, hot water output from the system is either delivered to the district heating network or pumped into a water storage tank.

Jensen said a Siemens programmable logic controller operates the entire system, including the rack, evaporators and defrost cycles.

Fenagy also carries the ATMO Approved Natural Refrigerants Label, for which it was reapproved in February.

“We have a lot of projects like this in our production pipeline.”

Klaus Jensen, Sales Director of Industrial Refrigeration and Heating at Fenagy

Optimizing electrical costs

In Denmark, electrical prices fluctuate hourly based on the power generated from intermittent wind and solar sources. Electricity prices are low when those sources are active.

“Delivering hot water to the city is the first priority of a district heating plant,” Jensen said. “The second is to consume electricity at low prices.”

The water storage “battery” on the heat pump system allows the district to take advantage of renewable energy. “However, you need a heat pump that can stop and start fast to do it,” he explained.

“Within five minutes of starting, our heat pumps are up and running at full speed,” Jensen said. The units may be on and off all day, with the water storage battery providing low-cost heating to the town.

“The natural refrigerant, the energy storage and the already established district heating network in numerous [Danish] cities is a brilliant combination,” Jensen said.

Heat pumps offer efficient solutions to support district heating, with the ability to generate up to five times more heat energy per kWh than direct electrical boilers or burning gas, according to ammonia (R717) heat pump manufacturer GEA.

At the ATMOsphere (ATMO) Europe Summit 2023, Raymond Decorvet, Senior Account Executive at MAN Energy Solutions, reported a rise in the demand in Europe for large-scale heat pump projects to support heat production decarbonization.

“Within five minutes of starting, our heat pumps are up and running at full speed.”

Klaus Jensen, Sales Director of Industrial Refrigeration and Heating at Fenagy

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