Investigación y proyectos

El refrigerante CO2

Effective climate protection with the refrigerant CO2

Chemical refrigerants: drivers of the greenhouse effect

Chemical refrigerants are still the standard in many industries today. At the same time, they contribute significantly to climate change.

The problem: air conditioning agents permanently escape through leaks, maintenance or accidents.

Hazardous release of refrigerants:

The average leakage rate of R-134a in new buses is 13.3% refrigerant per year for overland buses and 13.7% for city buses (Schwarz, Establishment of Leakage Rates of Mobile Air Conditioners in Heavy Duty Vehicles, 2007). According to publications of “Deutsche Umwelthilfe e.V.”, buses across Germany emitted nearly 100 tons of R-134a refrigerant in 2008.

The amount of refrigerant released by buses corresponds to 140,000 tons of CO2 equivalents per year. That corresponds to the annual CO2 emissions of 90,000 fuel efficient compact cars with an average manner of driving.

Climate change

Climate change is causing numerous regions in Africa and south-east Asia to turn into steppe and deserts. As a result, the population already suffering from hunger in these areas will find it even more difficult to grow their food in the parched soil in the future.
Climate change is increasingly leading to severe storms and flooding as well, which will also affect harvests.

Europe is being flooded with refugees as a consequence of climate change.
The poorest from rural regions in Africa and south-east Asia will leave their homes and flee to the world’s wealthier regions as a result of climate change.

Current studies confirm that the consequences of climate change are causing high costs for us in Germany as well. The costs of storm and flood damage as well as harvest losses will have to be paid by our farmers and ultimately by us as consumers. Investments for higher dikes against rising sea levels as a result of climate change caused by us will have to be covered by us as taxpayers.

EU climate targets
New regulations such as the ban on refrigerants with a particularly severe climate impact are intended to help stop climate change. Europe is thereby setting new global standards for climate change.
With the climate and energy strategy, the “20-20-20 Targets”, the EU has passed a package of directives intended among other things to achieve a 20% reduction in greenhouse gas emissions by the year 2020. 
The European targets for the year 2020 are as follows:

  • 20% reduction in greenhouse gas emissions compared to 2005
  • 20% share of renewable energy
  • 20% improvement in energy efficiency

All member states contribute to the reduction in greenhouse gas emissions with differentiated national targets determined in the course of a “burden sharing” process.
This is an ambitious project encompassing various concrete measures. One of them relates to the use of partly fluorinated hydrocarbons – also known as F-gases.
In order to minimise their influence on global warming, the EU Council in April of 2014 passed Regulation (EU) No. 517/2014 on fluorinated greenhouse gases (F-Gas Regulation).

F-gases contribute approximately 1.4% to the greenhouse effect worldwide (2011).
The demand for F-gases or products involving F-gases is skyrocketing as the quality of life in industrialised nations and emerging markets improves. The global installed cooling capacity and therefore the demand for refrigerants is increasing in direct correlation with the improving quality of life. Discontinuing the use of HCFCs is leading to a massive increase in HFC and PFC emissions. F-gases are extremely persistent, breaking down very slowly and therefore steadily accumulating in the atmosphere. They also have a major impact on our climate, meaning that small increases have a pronounced and long-lasting negative effect. Substituting natural substances for F-gases has become technically possible in many fields so that ambitious targets can be set.
F-gases are not only emitted as refrigerants but also due to numerous other applications.

Examining the refrigerants that are available in the foreseeable future shows that, from today’s perspective, only natural refrigerants can be considered as an alternative to the climate-damaging refrigerants currently in widespread use. Environmental acceptability, nearly unlimited availability and low prices are typical for these substances.

The Global Warming Potential is the potential contribution of a substance to warming atmospheric layers close to the ground, meaning what is known as the greenhouse effect. The contribution of the substance is stated as a GWP value relative to the greenhouse potential of the substance carbon dioxide (CO2).
GWP100 values – meaning the contribution of a substance to the greenhouse effect averaged over a period of 100 years – are used for the classification.
The lower the value of the CO2 equivalent, the lower the potential effect on global warming and the related environmental impact.
(Source: BNB UN 1.1.1)

Time to act - climate protection

Since the World Conference on Environment and Development in Rio in 1992, there has been international agreement that climate change must be stopped.

With the climate and energy strategy - the "20-20-20 goals", the EU has adopted a pact of directives which, among other things, aims to reduce greenhouse gas emissions by 20% by 2020. New provisions, such as the ban on particularly climate-impacting refrigerants, are intended to help achieve the EU climate targets. Europe is thus setting new global standards for the reduction of CO2 emissions.

In vehicle air conditioning systems, the fluorinated greenhouse gas tetrafluoroethane (R134a) has so far been used as a refrigerant. Directive 2006/40/EC on emissions from air conditioning systems in motor vehicles bans the use of refrigerants with a global warming potential higher than 150 in new passenger cars and car-like commercial vehicles from 1 January 2017. In the first step this only affects the automotive industry, but in the long term a general ban of R-134a is expected.

The key points of the EU F-gas regulation

Phase Down:

  • Step-by-step reduction of F-Gases
  • Reduction of the quantity to 21% by 2030 in six stages Use restriction
  • Step-by-step ban on particularly climate-damaging F-gases
  • Quotas - F-gas quotas are allocated to manufacturers and importers
  • Stricter requirements for leakage checks of refrigeration and air-conditioning systems
  • Extended operator obligations: Installation, maintenance, servicing, repair, etc. may only be carried out by certified staff

Fluorinated greenhouse gases and CFCs

While the classic greenhouse gases are mostly released as undesirable by-products, for example during the combustion of fossil fuels, fluorinated greenhouse gases are for the most part produced and used in a targeted manner. They are used today in a similar way to chlorofluorocarbons (CFCs) and halons, which are responsible for the destruction of the stratospheric ozone layer.

The global contribution of F-gases to the greenhouse effect today is about 1.3 percent (2004). A 2010 study by the Federal Environment Agency predicted that by 2050 F-gas emissions would increase to 7.9 percent (excluding HFC phase down) of global direct CO2 emissions.

In direct connection with the increasing quality of life, the installed cooling capacity and thus the demand for refrigerants is increasing globally. The phasing out of the use of ozone-depleting HCFCs leads to a massive increase in HFC and PFC emissions. F-gases are extremely long-lived, are only broken down very slowly and therefore accumulate constantly in the atmosphere. Furthermore, they have an extremely high climatic impact, i.e. small increases have strong and long-lasting negative effects. Substitution of F-gases by natural substances has become technically possible in many areas, so that ambitious goals can be set.

The Global Warming Potential is the potential contribution of a substance to the warming of the air layers near the ground, i.e. to the so-called greenhouse effect. The contribution of a substance is expressed as a GWP value relative to the global warming potential of carbon dioxide (CO2).
The GWP100 values are used for the assessment, i.e. the contribution of a substance to the greenhouse effect averaged over a period of 100 years.
The lower the value of the CO2 equivalent, the lower is the potential effect on
global warming and the associated environmental impacts. (Source NBB UN 1.1.1)




R-744 (CO2)


atmospheric residence time




GWP (100 years)


1 (0)


lower explosion limit




Ignition temperature




Vapor pressure at 60°C




Vapor pressure at 30°C




Vapor pressure at 0°C




Evaporation enthalpy at 0°C




Gas density at 0°C




volumetric cooling capacity at 0°C




The consequences: These commercially available refrigerants are currently becoming very expensive and will no longer be available in the future.

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.

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.

Raimund Loogen, Workshop Manager at NIAG, sums it up: “The R744 refrigerant not only pays off for the environment. Aside from the cost of the refrigerant, maintenance costs are significantly reduced as well since it can simply be discharged and a filter dryer is no longer needed either. It is also safe and easy to handle. We as a public transit company are visible to the public and a figurehead for the region. Due to this responsibility, we decided to equip the first buses with air conditioning systems using R744 five years ago. We are very proud of these R744 buses. They run flawlessly and only incur about one-fifth of the maintenance costs compared to a vehicle with a conventional R134a system.”

60 years of innovation: For the environment of tomorrow

Konvekta stands for environmental protection and sustainability. Therefore we have been taking our own paths in the development of efficient and climate-friendly cooling and heating technology for more than 20 years.

With natural CO2 as a refrigerant, we make a major contribution to active climate protection. Our "Made in Germany" technologies are used in the vehicle industry.

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