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Comparing the Climate Impacts of Mobile Air Conditioners

Past efforts to compare alternative mobile air conditioning systems have been thwarted by the lack of a single, globally accepted method to calculate their greenhouse gas emissions. Different researchers used different assumptions and methodologies, resulting in wide variation in greenhouse gas emission calculations. In order to enable an "apples-to-apples" comparison, General Motors, the Japanese Automobile Manufacturers Association, the Society of Automotive Engineers, and the U.S. Environmental Protection Agency teamed up and developed a common methodology to calculate the lifecycle climate performance of mobile air conditioners with different refrigerants. The Global Refrigerants Energy & Environmental Mobile Air Conditioning Lifecycle Climate Change Performance (GREEN-MAC-LCCP)© model is now available. This tool lets stakeholders compare the choices in a clear, transparent manner. It is globally peer reviewed and is now globally accepted as the most credible method of comparing the climate performance of mobile air conditioning.

Download the GREEN MAC LCCP model. (MS Excel, 7.89 MB)

How Lifecycle Climate Change Performance is calculated for Mobile Air Conditioners

Lifecycle Climate Change Performance provides a holistic approach in estimating all greenhouse gas contributions emitted during the lifetime of an alternative refrigerant and a MAC operating system. The direct and indirect components of the model are explained as follows:

Direct emissions result from the direct leaks of the refrigerant into the atmosphere and are evaluated based on the global warming potential of each chemical and its mass emitted into the atmosphere. The direct emissions are expressed in terms of CO2-equivalent (CO2-eq.) emissions and are calculated based on the global warming potential of the refrigerant.

Indirect emissions result from the energy consumption due to manufacturing, operation, and disposal at the end of a vehicles life, and are also reported in terms of CO2-equivalent emissions. Indirect emissions calculations also account for the carbon content of the fuel utilized in each process and during vehicle operation. The box below explains direct and indirect mobile air conditioning emissions in further detail:

Direct and indirect mobile air conditioning greenhouse gas emissions

Direct Emissions result from the direct leaks of the refrigerant into the atmosphere and are an aggregate of the following leakage categories:

  • Regular emissions, which refer to the refrigerant leaks or permeation from the A/C system during operation,
  • Irregular emissions due to accidents, stone hits, product defects etc,
  • Service emissions from garages during maintenance and repair. These items are newly estimated based on the SAE Improved Mobile Air Conditioning (SAE I-MAC) Study recently completed. The results are still somewhat dependent on the skills and practices of the service technicians.
  • End-of-Life emissions from the recovery of refrigerant at the end-of-life of the vehicle,
  • Leakage during refrigerant production and transportation, and
  • Atmospheric reaction products associated with the atmospheric breakdown of the refrigerants.

Indirect Emissions result from the energy consumption due to MAC manufacturing, and operation, and end-of-life and is an aggregate of the following CO2 emissions categories:

  • Manufacturing and end-of-life recycling processes of various alternative refrigerants,
  • Manufacturing and end-of-life recycling processes of each component of the A/C system,
  • Fuel use emissions associated with the A/C operation (such as those associated with the operation of the compressor, and engine cooling fan) during the lifetime of the vehicle, and
  • Emissions associated with the additional fuel consumption due to the A/C mass transportation onboard the vehicle throughout the lifetime of the vehicle

How to Use the Model

GREEN-MAC-LCCP© consists of many interlinked spreadsheets of data required to run the model. Most of the input data are fixed based on the harmonization process. This prevents tampering with the model and makes sure that comparisons are genuine. Only a small amount of input data is required to run the model. For each global alternative refrigerant, the following information is required:

The model output provides the LCCP (in terms of CO2-eq emissions) of any global alternative refrigerant.

Download the GREEN MAC LCCP model. (MS Excel, 6.89 MB)

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