Precise refrigerant charge essential to maximise EV range: Study

There is no doubt that refrigerant-based thermal management of electrified drive systems and batteries will place those with strong knowledge and skills in mobile air-conditioning and auto-electrical systems at the forefront of the sector in years to come.

The accelerating adoption of this thermal control method for critical systems in vehicles also highlights the importance of transitioning to competence-based licensing for existing and emerging automotive trades that necessitate the handling of refrigerants, especially as thermal management and air-conditioning systems are increasingly using low-GWP products such as R1234yf and R744 that fall outside Australia’s existing environmental-based licensing.

Further validation of VASA’s position on this  comes in the form of a scientific report released this year, which concludes that the battery range of electrified vehicles with the air-conditioning heat pump (ACHP) method of cabin climate control and propulsion system thermal management relies heavily on careful and precise selection of refrigerant charge at the engineering stage.

It follows that maintaining this precise level of refrigerant charge is also critical to the lifetime energy efficiency and therefore battery range for the vehicle.

A Study of Optimal Refrigerant Charge Amount Determination for Air-Conditioning Heat Pump System in Electric Vehicles, published by the MDPI platform for peer-reviewed scientific journals, describes multiple methods of refrigerant charge validation in a complex triple-evaporator automotive ACHP system, such as used in electrified vehicles.

It shows that the wrong refrigerant charge in ACHP-equipped electric vehicles causes a marked reduction in coefficient of performance (COP).

As VASA members know, for several years car manufacturers have been seeking greater efficiencies and smaller refrigerant charges on their internal combustion engine vehicles, increasing the importance of accurate refrigerant charge weights.

But an air-conditioning system with a compressor driven by the internal combustion engine has less work to do than one that is relied on to provide year-round cabin comfort and battery/drivetrain thermal management.

Further, the energy density of petrol or diesel compared with even the best EV batteries means any additional load on the engine to provide cabin comfort from an air-conditioning system that is working inefficiently due to incorrect refrigerant charge is likely to be less noticeable to performance and fuel-efficiency than if the same condition presented in an EV.

Keeping EV batteries and drivetrains at optimum operating temperatures, including different requirements while driving to those when charging, is essential for maximising range and energy efficiency.

The scientific report further demonstrates the importance of well-trained, highly skilled technicians in ensuring that EVs maximise and maintain their energy efficiency and environmental benefits.

Licensing and training will be important elements in producing and maintaining the required high quality of technicians and recognising their continued vital role in helping Australasia reach local and global emissions targets, including commitments to the Paris Agreement.

While the report focuses on initial engineering, automotive technicians will need appropriate training and qualifications to ensure ACHP system efficiency is maintained for the life of a vehicle, not just when it leaves the production line.

VASA president Ian Stangroome said: “It is imperative that all technicians receive the appropriate education to accommodate both further reductions in refrigerant charge quantities and increased system complexity, such as highlighted in this study, in meeting the requirements for passenger comfort and battery temperature management in electric vehicles.”