Emissions Savings from Efficient Mobile Air-Conditioning (MAC) Systems in Passenger Vehicles

Mobile Air-Conditioning (MAC) systems are a substantial source of energy consumption and CO₂ emissions in passenger vehicles, particularly for electrified vehicles under real-world operating conditions. Enhancing the efficiency of such systems is imperative to achieving greater energy efficiency and maintaining occupants’ comfort. In recognition of their significance, MAC systems can be classified as eco-innovative technologies under EU Regulation 2019/631, effective from 2025. This study lays the groundwork for a methodology to calculate CO₂ savings from eco-innovative MAC systems in passenger cars. The approach compares CO₂ emissions between baseline and eco-innovative vehicles under active and inactive MAC systems. Literature-derived indicative ambient conditions are applied to reflect realistic MAC usage scenarios in Europe. The testing protocol follows the WLTP procedure under controlled ambient conditions, including temperature, humidity, and solar irradiation, which can either be physically simulated or omitted by adopting an equivalent testing option. Vehicles are grouped into MAC Test Groups based on uniform characteristics such as powertrain architecture, MAC compressor type, and bodywork to ease the testing burden. Preconditioning and soaking requirements are detailed for consistency. CO₂ savings are calculated using established equations that measure the difference between the tail-pipe emissions with and without MAC activation, both for a baseline and an eco-innovative vehicle. The proposed methodology also offers flexibility for testing various powertrain configurations, from conventional to electrified vehicles thanks to an internally developed vehicle model that estimates the baseline vehicle CO2 emissions. A case study based on a Plug-in Hybrid Electric Vehicle (PHEV) is presented, and it shows a MAC impact of around 7% of CO2 emissions. This framework ultimately provides a robust tool for validating eco-innovative MAC technologies, while promoting the reduction of vehicle CO₂ emissions and advancing the development of energy-efficient automotive systems.