E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

Peter Donaldson canvasses industry experts on the EV-specific issues surrounding HVAC systems Taking the temperature W hile most drivers of IC-engined vehicles are vaguely aware that running the air conditioning increases fuel consumption, such is the energy density of petrol and diesel that it has rarely been a major concern, although with fuel prices at record highs that is changing rapidly. Similarly, IC engines produce so much waste heat that drawing upon it to warm up the cabin on a cold day has a negligible effect on fuel burn. It is a different story with EVs, however, so attention has turned in earnest to the energy efficiency of HVAC systems because they can have a major effect on range, particularly in extreme ambient temperatures or demanding driving conditions. A wide range of innovations is being applied to the problem of efficiently maintaining pleasant temperatures for EV occupants. These include increasing integration with overall vehicle thermal management by moving heat between the battery pack, powertrain and the cabin, along with contact and radiative cabin heating that relies less on warming air. Further, variable-flow AC compressors driven by high- voltage motors, new refrigerants, electric coolant heaters, heat pumps, advanced phase-change materials and high-fidelity engineering simulations are also in the mix. Energy consumption Putting some numbers to the problem, in very high ambient temperatures – say 40 C – around 5-6 kW might be needed to cool the cabin and key components, which might reduce a typical EV’s range by 26- 30%, according to an expert at an engineering simulation company. At very low temperatures (below -10 C or so) the effect can be even greater, as warming the cabin with a modern resistive heater using a positive temperature coefficient (PTC) material, but without a heat pump, can reduce the vehicle’s range by up to 50%, the expert says. As only a few vehicles take these effects into account in the range calculation algorithms that keep the driver informed, the software’s predictions can be thrown off. “This is one of the main reasons why there is often such a big difference between the initial prediction and the range that the car actually achieves,” the expert adds. The power consumption of the HVAC and thermal management systems depends greatly on both the ambient temperature and how the vehicle is being driven, experts from an automotive electrification specialist emphasise, as well as on the system’s key componentry – whether it includes an electric coolant heater and/or a heat pump, for example. At moderate ambient temperatures (about 15-20 C) and the modest cruising speeds typical of urban traffic, demand for cooling or heating is very low HVAC and climate control in EVs are increasingly integrated with battery and powertrain thermal management (Courtesy of AVL) 64 Autumn 2022 | E-Mobility Engineering