StarCO₂mpressors for electric buses and trains

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StarCO₂mpressors HR40 and HR60: Naturally Innovative Air Conditioning Solutions

Introducing the Danfoss BOCK® CO2 StarCO2mpressors HR40 and HR60 - a game-changer in electric bus and train air conditioning. Our innovative "star" drive design offers space-saving roof installation with the industry's lowest overall height and weight.

Experience energy-efficient and eco-friendly heat generation through a CO2 heat pump, even in frigid -20 °C conditions, without the need for auxiliary heaters. Embrace innovation for a greener future!

Key Benefits for Manufacturers and Transport Companies:

Economically and ecologically sustainable: Secured competitive advantages through an investment that is both economically and ecologically sustainable, recognized with the Busworld Innovation Award Label in 2019.

Innovative technology: Utilizes innovative radial piston technology specifically designed for mobile CO2 applications, ensuring efficiency and reliability.

Robust construction: Features a welded, robust steel housing with the lowest risk of leakage, guaranteeing durability and safety.

Space-saving design: Boasts the lowest overall height (219mm) and weight (81kg) in its power class, optimizing space utilization in vehicles.

Versatile performance: Offers a wide speed range to cover diverse power requirements for vehicle air conditioning, heating, and battery conditioning, enhancing versatility.

Tailored oil management: Includes specially adapted oil management tailored for vehicle applications, ensuring smooth operation.

Proven Reliability: Demonstrates proven practicality through successful series operations, instilling confidence in performance.

Robust Valve Design: Features a robust ring valve design, enhancing overall reliability and longevity.

Features and benefits of StarCO₂mpressors for electric buses and trains:

Compact efficiency: innovative "star" drive design with radial piston cylinders arranged in a star configuration around the crankshaft, offering an extremely compact compressor perfectly suited for CO2 refrigerant (R744) and mobile applications.

Energy efficiency: eliminates the need for energy-consuming auxiliary heaters, achieving up to 20% higher efficiency with the CO2 heat pump.

Extended vehicle range: provides approximately 40% more vehicle range, enhancing mobility and reducing operational costs.

  • Four-cylinder radial reciprocating compressor HR40 and HR60
  • Max. permissible overpressure: 150 bar/100 bar (HP/LP)
  • Weight: 81 kg
  • Height: approx. 219 mm, overall length: 600 mm
  • Wide speed range from 750 to 4,350 rpm / 12.5-75 Hz (HR60 65 Hz) for heat pump application and thermal management
  • Maximum permissible inclination: 22° continuous operation, 30° short term
  • Pipe connection with flange connection, optional solder flange
  • Displacement at 50 Hz / 2,900 1/min: HR40: 7.3 m³/h / HR60: 10,9 m³/h
  • Cooling capacity1) HR40: 7 - 35 kW/ HR60: 9 - 47 kW
  • Heating capacity2) HR40: 4 - 27 kW/ HR60: 6 - 35 kW

1) +10°C/ 40°C (100 bar) / 10 K
2) -20°C / +25°C (80 bar) /10 K

Specifically developed for mobile CO2 applications

  • Efficient reciprocating piston technology, especially part-load optimised for heat pump applications
  • Very wide speed range
  • Lowest overall height, lowest weight
  • Welded housing with reduced interfaces for lowest risk of leakage
  • Space-saving roof installation in electric buses and trains
  • Robust and reliable, proven in practice

Air conditioning and heating with climate-neutral refrigerant R744

  • Natural, non-flammable refrigerant
  • Climate neutral: no ozone depletion potential (ODP = 0)
  • The lowest global warming potential (GWP = 1)
  • Efficient operation of heat pumps down to an outside temperature of -20 °C
  • Up to 75% energy savings compared to electric heating
  • Meets the criteria of the "Blue Angel" Eco-label
  • Meets the subsidy requirements for electric bus air conditioners in Germany

BOCK® compressors with R744/CO₂ as refrigerant

  • Environmentally Friendly and Cost-Effective: CO2 is a natural, eco-friendly, and economical refrigerant compared to fluorinated alternatives. It's non-toxic, non-flammable, and colorless.
  • Low Environmental Impact: CO2, with a GWP value of 1, isn't subject to the F-Gas Regulation's "Phase-Down Scenario." Leak tests are only mandatory for systems with a 5-tonne CO2 equivalent charge, saving on testing costs.
  • No Costly Recovery: CO2 release during service work doesn't necessitate expensive refrigerant recovery, reducing maintenance expenses.
  • Expert Support: CO2 systems can have demanding characteristics, including high pressure and low critical points.
Read more about CO₂ and our solutions

Looking for spare parts?

BOCKSHOP Spare parts catalog


The online spare parts catalog allows you to find the right spare parts and accessories for BOCK compressors and units with just a few clicks. 



Type Name Language Valid for Updated Download File type
Brochure BOCK, StarCompressor English Multiple 06 Oct, 2023 2.3 MB .pdf


Compressor selection tools - VAP

The VAP tool is ideal for finding the appropriate compressors for mobile applications. By inputting the required refrigerating capacity and operating conditions, the tool will display compatible components right away. In the VAP tools you will also find additional details about the suggested compressors.

Related applications


Join the CO₂ Technology Training at our Training Center in Frickenhausen

On-site CO₂ Basic training with the tour of the training application, available in English and in German.

Gain a good awareness knowledge about CO₂ technology and register to one of our face-to-face courses. A complete transcritical supermarket cooling system, incl. heat recovery, air conditioning, parallel compression and ejector is available at our training center in Frickenhausen.