Why thermal management is vital for electric vehicles

Heating and cooling of the battery and its associated power electronics must be front of mind for electric vehicle development teams, learns Freddie Holmes

The importance of thermal management in a battery electric vehicle (BEV) cannot be overstated. The performance of the vehicle can fluctuate greatly depending on how warm or cool it is, and cases of serious overheating can also be a severe safety concern. Much like a smartphone, keeping an EV battery at an optimum temperature can help to preserve its capacity, optimise its length of charge and retain the health of its cells.

Driving range is also a real point of interest for both industry and consumer: the greater the vehicle’s range on a single charge, the more likely the car is to sell. Thermal management is vital to ensuring new vehicles meet those expectations. However, it is not just the battery pack that needs to be considered. Other electrical components including inverters and e-motors, for example, must also be kept in check. As with many areas of the vehicle, simulation can play a useful role here.

Much like a smartphone, keeping an EV battery at an optimum temperature can help to preserve its capacity, optimise its length of charge and retain the health of its cells

“We can model the heat losses and calculate the temperature of the power electronics,” said Dr. Armin Traußnig, Lead Engineer Thermal and HVAC System Simulation at AVL during a recent Automotive World webinar. “Depending on the temperatures, we can then activate power de-rating, for example.”

Technology within the cabin also comes into play. With any modern vehicle, air conditioning is now a must-have, and not an optional extra. Those who have bought a new EV will expect a high level of comfort and in the case of more expensive models, a degree of luxury. Ensuring that drivers are able to cool or heat the ambient temperature of the cabin without impacting driving range is vital, but this can pose a challenge for thermal management.

“Regulating how much heating or cooling power is required to keep the cabin cool in summer and warm in winter is quite a challenging task,” explained Traußnig. Developers need to address a wide range of heat sources, such as solar radiation from the sun, the heat that is emitted from passengers, as well as the thermal insulation in the roof and underbody. “All of this needs to be taken into account in a simulation model to achieve an energy balance,” advised Traußnig.

Cost is an important consideration. We have developed an efficient methodology that can integrate our simulation models with the test bed

Charging the vehicle also complicates matters; fast charging at power ratings greater than 100kW can lead to huge heat rejections, which need to be efficiently extracted from the thermal system. “We definitely see growing interest in the effect of fast charging on thermal management,” said Traußnig. “In particular, there is interest in immersion cooling that allows you to reduce the thermal resistance of the battery and achieve even higher fast charging rates and better cooling performance.”

Simulation can also help to keep development time and cost to a minimum.

“Cost is an important consideration,” said Dr. Christian Mayr, Project Manager Integrated and Open Development Platform at AVL. “We do not want to take a lot of time to commission our systems, so we have developed an efficient methodology that can integrate our simulation models with the test bed.”

To see a replay of the full webinar, please follow this link.

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