Fenagy Heat Pumps
Klaus Jensen shows off Fenagy's isobutane heat pump.

Fenagy Shows Off 3MW CO2 Heat Pump Rack and New 1MW Isobutane Heat Pump in Exclusive Factory Tour Video

The Danish manufacturer is ready to meet the European demand for large-scale heat pumps.

Danish heat pump manufacturer Fenagy is ready to meet the European market demand for large-scale heat pumps.

It demonstrated this during a recent tour of its manufacturing facility in Aarhus, Denmark. Klaus Jensen, Sales Director of Industrial Refrigeration and Heating, showed Marc Chasserot, Founder and CEO of ATMOsphere, a 3MW (853TR) CO2 (R744) rack designed for an air-to-water heat pump and a new water-to-water 1MW (284TR) isobutane (R600a) heat pump. ATMOsphere is the publisher of NaturalRefrigerants.com.

According to Jensen, Fenagy has produced 3MW CO2 racks for roughly a year and a half. Previously, 2.2MW (626TR) was its highest-capacity CO2 rack. Jensen said racks can be connected to provide higher capacities, with the company currently working on a 13MW (3,696TR) district heating project for a city in southern Denmark.

The 3MW racks contain up to:

  • Eight compressors, normally 8-cylinder Bitzer compressors, according to Jensen
  • Six “monster-sized” ejectors developed in collaboration with Norwegian University of Science and Technology that, according to Jensen, allow constant operation at high pressures
  • Two Kelvion heat exchangers/gas coolers, each with a 1.5MW (427TR) capacity
  • Two Temprite oil separators
  • A control panel equipped with Fenagy software on a Siemens platform for real-time monitoring

In addition to building larger CO2 heat pumps, Fenagy has also begun working with hydrocarbons, specifically isobutane. Jensen said Fenagy started working with isobutane because of customer requests involving district heating projects with high return water temperatures of 45‒50°C (104‒122°F).

“Here, CO2 is not perfect as a standalone refrigerant,” Jensen said. “We started thinking about combining CO2 with isobutane, using isobutane heat pumps to subcool the water and CO2 system.”

As a refrigerant, CO2 works best with large temperature changes, Jensen explained. When cold water enters the gas cooler, CO2 supplies high outflow temperatures. Hydrocarbons, however, are more comparable to conventional refrigerants and work well with low changes in temperature and without transcritical operation, he added.

“It’s completely different, and that opens new markets to us,” Jensen said.

New markets

Fenagy can supply up to 95°C (203°F) hot water with isobutane, even with a high water-return temperature, Jensen said. “We can heat water from 70 to 90°C [158 to 194°F] or 60 to 70°C [140 to 158°F], which is different from CO2.”

The lower operating pressures of hydrocarbons also simplify the system, allowing the use of screw compressors, according to Karsten Sand, Mechanical Design Engineer at Fenagy.

“The screw compressors reduce the required components and piping compared to the reciprocating units in CO2 heat pumps,” Sand says in a video posted to Fenagy’s LinkedIn page.

On Chasserot’s tour, he viewed Fenagy’s hydrocarbon production area. It contained a step-up water-to-water R600a heat pump system to provide cooling and heating for a biogas application. According to Jensen, Fenagy will meet the 9MW (2,559TR) capacity requirement using three “machines,” each equipped with three 1MW (284TR) Bitzer screw compressors, with each compressor containing roughly 50kg (110lbs) or less of isobutane.

Each machine contains three individual heat pumps to step up the water temperature incrementally, Jensen said, with the “modular approach optimizing the efficiency of the system.”

Going bigger

According to Sand, Fenagy is developing a larger hydrocarbon heat pump using a 2,000m3-per-hour (528,344gal-per-hour) Bitzer compressor, allowing a single heat pump to provide 2MW (569TR) capacities. Three units combined in “series or parallel” will provide up to 6MW (1,706TR) capacities.

“We are getting inquiries for water output at 110, 120, even 140°C [230, 248 and 284°F] for other applications,” Jensen said.

Using other hydrocarbons at different points could help achieve these higher temperatures. “Propane [R290] ‒ good at lower temperatures ‒ could benefit the system with isobutane operating better at the higher ranges,” Jensen said.

Besides the biogas industry, the company sees potential for the machines in other markets, including geothermal and carbon capture.

Partially owned by Swedish wholesaler Beijer Ref, Fenagy provides natural refrigerant CO2 and hydrocarbon solutions for the industrial and district heating markets.

Fenagy carries the ATMOsphere ATMO Approved Natural Refrigerants Label, with reapproval obtained last February. The label marks the company as a best-in-class manufacturer of natural refrigerant systems and components around the world, with Fenagy initially approved for it in May 2023.

“We are getting inquiries for water output at 110, 120, even 140°C [230, 248 and 284°F] for other applications.”

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

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