StarCO2mpressor HR40

The proven new milestone and Award Winner in electric bus, air conditioning and heating.


StarCO2mpressor is the new generation of CO2 mobile compressors for air conditioning and heating. The innovative drive gear design offers new chances for electric bus air conditioning combining with heat pump as well as railway climate control. Cylinders are arranged in a star shape around the crankshaft achieving a compact and light weight design perfectly suited for the natural refrigerant CO2 (R744).


Winner of the Busworld Innovation Award 2019.

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The StarCO2mpressor from BOCK pays off with the climate neutral R744 refrigerant for functional and environmentally advantages in bus and rail air conditioning:

  • Natural, non-flammable refrigerant
  • Climate neutral: no Ozone Depletion Potential (ODP = 0) and the lowest Global Warming Potential (GWP = 1)
  • Efficient operation of heat pumps down to an outside temperature of -20 °C
  • Meets the criteria for the eco-label “Blauer Engel” (Blue Angel)
  • Meets the requirements of many national support programs
  • CO2 air conditioning: award criterion in the hybrid bus
  • Promotion of the German Federal Ministry for the Environment
  • Nature Conservation, and Nuclear Safety (BMUB)

Advanced and proven drive gear design:

  • Cylinders arrayed in a star shape around the crankshaft
  • Designed for transcritical use with R744 refrigerant

Very smooth operation:

  • Robust drive gear with multiple bearings: high comfort for bus and train users

Space-Saving lightweight:

  • 220 mm height: perfect for roof installation
  • 81 kg weight: 25 % less weight compared to standard compressors with same performance class

 Wide speed range:

  • 12.5 Hz to 75 Hz heat pump performance

High-performance oil pump:

  • Constant oil supply up to 22° inclination during continuous operation
  • 30° short-term

Welded, robust steel housing:

  • Lowest leakage potential
  • High reliability
  • Consequent reduction of potential leakage points
  • Especially developed for transcritical CO2 applications

Innovative radial reciprocating technology specially designed for mobile CO2 applications:

  • Space saving roof installation in electric buses and railways
  • Low height, low weight
  • Increased effectiveness in air-cooling and heating
  • Complete climate control: heat pump function – even at outside temperatures of -20 °C
  • Achieving plus 20 % efficiency with combined heat pump solution
  • Pioneering solution: state of the art efficiency rates in air conditioning and heating
  • Eliminates the need auxiliary heaters
  • Increases vehicle range up to 40 %.

Economically and ecologically: New standard for mobile CO2 compressors:

  • Robust welded steel housing
  • Special Oil management
  • Very smooth operation
  • Advantageous suitability proven in series use of renowned automotive manufacturers
  • Suitable investment for manufacturers and transportation companies wanting to be competitive in the market of electromobility

BOCK StarCO2mpressor is the latest state of the art technology:

  • Four-cylinder radial reciprocating compressor HR40
  • Max. permissible overpressure: 150 bar/100 bar (HD/ND)
  • Weight: 81 kg
  • Height: approx. 220 mm, overall length: 600 mm
  • Maximum permissible inclination: 22° continuous operation, 30° short-term
  • Pipe connection with flange connection, optional soldering sleeve
  • Displacement with 50 Hz / 2,900 1/min: 7.3 m3/h
  • Cooling1/heating2 capacity: 7 – 35 kW / 5 – 28 kW

1) based on evaporation temperature +10 °C, superheat 10K, high pressure 100 bar, gas cooler outlet +40 °C
2) related to evaporating temperature -20 °C, superheat 10K, high pressure 80 bar, gas cooler outlet +25 °C


12,5kW / 17HP (motor code)

Compressor type

Radial reciprocating



Maximum pressure


Number of cylinders


Displacement range (m3/hr)

7,30 m3/h (50 Hz – 2900 1/min)

Variable or single speed

Variable: 1,8 – 11,0 m3/h (12,5-75 Hz)

Cooling capacity

4,3 – 34,9 kW @ to/toh/tga_out(pv2)/f: +10°C/10K/40°C(100 bar)/12,5-75Hz

Discharge gas temp

Depends on operating conditions – on request

Power consumption

Depends on operating conditions – on request




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