CO2 as refrigerant (R744)
The climate friendly alternative
CO2 as a natural refrigerant, also known as R744, is the climate-friendly alternative to today's common chemical refrigerants. It is environmentally friendly, has a high cooling capacity, is not flammable and does not form any decomposition products. Furthermore, it is inexpensive and permanently available.
CO2 is a natural component of air and has a global warming potential of only factor 1 - chemical refrigerants are 1000 times higher (R134a GWP 1340) or they are combustible and the decomposition products are dangerous for the environment.
CO2 can be used not only in air conditioning systems but also to operate heat pumps. These can cool as well as heat efficiently.
Economic benefits of R744/CO2
CO2 heat pumps: zero emissions, highest energy efficiency
With natural CO2 as a refrigerant, considerable energy savings can be achieved in cooling and heating operation. Because CO2 has an up to 20% higher efficiency than chemical refrigerants, accordingly, the target temperature is reached 20% faster.
CO2 is particularly suitable for use in heat pumps.
Environmental Benefits
- sustainable and approved refrigerant
- non-flammable and non-toxic
- no ozone depletion potential
- very low global warming potential compared to conventional synthetic refrigerants
- no toxic degradation or decomposition products
- no fossil fuels required
Carbon Dioxide (R-744) - the “Safe” Alternative (Measurement result by BG Verkehr)
Measurement result by BG Verkehr
Carbon dioxide (R-744) is neither toxic nor flammable, according to the safety data sheet. A measurement carried out by BG Verkehr confirmed that the use of R-744 in buses is safe under the tested conditions (measurement report no. mg 11 1031). For R-744, the maximum workplace concentration is 5,000 ppm. This value was not exceeded during the tests. Due to its high-pressure characteristics, an air-conditioning system operated with carbon dioxide is also suitable for reversing the cooling process. This means that the air-conditioning system can also be used as a heat pump for heating buses.
By contrast, a heat pump using R-134a would not provide sufficient performance at temperatures below 0 °C due to pressures being too low.
Field reports from public transit companies
BVG made itself available for a long-term test of this technology back in 2008 as one of the first transport companies. A standard city bus was equipped with a CO2 air conditioning system for this purpose.
To date this bus has covered more than 500,000 km. Thanks to positive experience with the first bus, 6 additional city buses with this technology have been operated daily by BVG since May of 2010. Burkhard Eberwein, Fleet Manager at BVG and member of the VDV Technical Committee, finds the innovative air conditioning technology convincing and speaks of a concept for the future.
Satisfaction at BVG: 122 buses have been delivered to the transport company by the end of 2020, with more to follow.