The primary motivation for developing the tool was to provide a simplified user interface. The previous GREEN-MAC-LCCP tool used Excel spreadsheets for all inputs, while the new model allows users to enter values via a WinForms interface, or upload from pre-established Excel templates.

The new tool dramatically reduces the calculation runtime. Users have results in less than five minutes, versus the 1- to 2-hour runtime of the prior GREEN-MAC-LCCP.

Pre-set weather data for numerous worldwide locations, reflecting recent increases in temperatures resulting from global warming, are included in the tool.

User input options have been expanded such that calculations include the type of refrigerant, leakage rate, vehicle type, vehicle lifespan and climate conditions selected by city. Defaults for total driving distance per year, driving time per year, and vehicle lifetime can be changed based on user data for each city and/or system in the user interface.

The capability to address the use of electric compressors and water-based systems in MAC systems has been added in the IMAC-GHG-LCCP. This gives auto manufactures a stronger start in the transition to electric cars on a mass scale. With this new tool, capacity and power consumption inputs for a vehicle using an electric compressor can be entered for each combination of ambient temperature and vehicle speed, instead of ambient and compressor RPM as for a belt-driven compressor. This encourages the evolution of existing technologies and enables the testing of new MAC technologies. Also incorporated is support for systems with multiple evaporators, multiple chillers, and additional sources of power consumption beyond the compressor.

OTS developed the IMAC-GHG-LCCP tool under the direction and guidance of the Society of Automotive Engineers (SAE) Interior Climate Control Steering Committee. The tool meets the requirements of the following standards:

• SAE Standard J2765^TM
  Procedure for Measuring System COP (Coefficient of Performance) of a Mobile Air Conditioning System on a Test Bench was written to describe how energy consumption input data should be collected and used into a life cycle model for MAC systems. Input data has been revised in the IMAC-GHG-LCCP tool to include compressor energy consumption and the COP is calculated internally in the model.
  
  
• SAE Standard J2766^TM
  Life Cycle Analysis to Estimate the CO₂-Equivalent Emissions from MAC Operation describes the recommended inputs and calculations suggested for use in a typical LCCP model for MAC systems. The IMAC-GHG-LCCP tool adheres to the calculation methods prescribed in this standard.
  
  
• SAE Standard J2727^TM
  Mobile Air Conditioning System Refrigerant Emission Charts for R-134a and R-1234yf is used as the source for user inputs of leakage rate for each system. This leakage rate is then corrected for the average ambient temperature in each city based on a correlation developed by Clodic¹.

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¹Clodic, D. “Research study on the definition of the implementation of a method of measurement of annual leak flow rates (LFRs) of MAC systems,” January 2006.