Danfoss’s compressor technologies are supporting the development of hydrocarbon high-temperature heat pumps (HTHPs) for industrial process heat applications, targeting future output temperatures of up to 150°C (302°F) using hydrocarbons in cascade, including propane (R290), isobutane (R600a), butane (R600) and isopentane (R601a).
Ivan Rangelov, Industrial Heat Pump Director at Danfoss, outlined the current state of the technology and what lies ahead in an interview with Marc Chasserot, CEO and Co-Founder of ATMOsphere, at Mostra Convegno Expocomfort (MCE) 2026. The event was held March 24‒27 in Milan. ATMOsphere is the publisher of NaturalRefrigerants.com.
“Our KS2/3 semi-hermetic screw compressor is already approved for up to 90°C [194°F] using hydrocarbons,” said Rangelov. “We are testing now, in the lab and in a couple of field tests, to go up to 100°C [212°F], with performance approval expected before the end of summer.”
Danfoss is collaborating on hydrocarbon HTHPs with the Danish Technological Institute (DTI) and Danish heat pump and chiller manufacturer Fenagy, with funding from Denmark’s Energy Technology Development and Demonstration Program (EUDP). The project aims to decarbonize industrial processes that rely on fossil fuel-based steam, with temperature outputs of up to 130°C (266°F) to meet the low-pressure steam requirements of the food and beverage industry. Reaching 150°C will open other markets, including pulp and paper, textiles and dryers.
The roadmap: Since isobutane’s reasonable condensing temperature tops out at 110‒120°C (230‒248°F), Rangelov said that Danfoss is working with DTI and Fenagy on a butane solution to reach 135°C (275°F), and will then investigate isopentane to reach up to 150°C. The project aims to combine the hydrocarbon systems with a water steam recompressiom cycle, with the latter bringing the steam temperature from around 130°C to a target of 200°C (392°F).
- Danfoss expects to start testing units with the new semi-hermetic screw compressor at a condensing temperature of 135°C (275°F) to support water output at 130°C after summer 2026.
- “Going to 130°C is so challenging for the equipment that we’ve decided to run without the integrated inverter, and we removed the slide valve,” Rangelov said.
- Once the equipment can reliably deliver 130°C water with butane, the project will focus on reaching 140°C (284°F), with the roadmap extending to 150°C using isopentane.
The final product: Fenagy plans to offer several different HTHP capacity sizes for stepwise decarbonization, with a modular design that allows flexible grid-friendly solutions, according to Rangelov.
- Smaller-capacity units will use Danfoss’s Bock semi-hermetic piston compressors.
- Larger-capacity units, approximately 700‒800kW (199‒227.5TR) are being tested with KS series of semi-hermetic screw compressors.
Expanding portfolio: In October 2025 Danfoss acquired Italian screw compressor manufacturer Palladio Compressors. The KS series semi-hermetic screw compressors used in the hydrocarbon HTHP project were part of the acquisition.
- Danfoss aims to extend the current 1MW (284TR) maximum compressor size of the KS series to 1.5MW (427TR), according to Rangelov, with availability in 2027.
- Rangelov noted that the KS1 compressor, which features an externally accessible oil filter, is to his knowledge the first semi-hermetic screw compressor with an integrated inverter suitable for use with hydrocarbons.
- “Palladio’s advanced technology complements our portfolio, enhancing our compressor solutions for industrial heat pumps and large commercial and industrial refrigeration,” said Fabio Klein, Divisional President of Commercial Compressors at Danfoss.
Quotable: “If we can go all the way to 150°C, as much as a quarter of all industrial process heat needs can be covered by [natural refrigerant] heat pumps,” Rangelov said. “For the food and beverage industry, the ability to reuse waste heat from the cooling system rather than rejecting it to ambient air provides another benefit.”
“If we can go all the way to 150°C, as much as one-third of all process heat needs can be covered by [natural refrigerant] heat pumps.”
Ivan Rangelov, Industrial Heat Pump Director at Danfoss
This information on the refrigerants used in this project and its timeline have been updated.
