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:
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:
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:
- Component mass
- Refrigerant mass & global warming potential
- Leakage rate
- Coefficient of performance (COP) and Qe data obtained from bench or vehicle tests
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)