Thermal Management for Electric Vehicles 2021-2031

The electric vehicle (EV) market is growing rapidly and has even proved resilient to COVID-19 related shutdowns, seeing year on year growth throughout 2020. Within the EV market, we are seeing increases in battery capacity, range, charging rates, wide bandgap semiconductors and high-performance traction motors. Additionally, EV fires and related recalls have brought the concept of thermal runaway detection, prevention and protection to the fore. All of these trends demand more effective thermal management systems, solutions and materials.

The latest report from IDTechEx on Thermal Management for Electric Vehicles details the OEM strategies, trends and emerging alternatives around the thermal management of Li-ion batteries, electric traction motors and power electronics. This information is gathered from primary and secondary sources in combination with an extensive model database of over 250 EV models sold between 2015 and 2020, giving a comprehensive overview of the topic.

The technologies and strategies currently in use are described, analysed and forecast. Emerging alternatives like immersion cooling are also addressed and discussed for their suitability in future applications along with adoption forecasts. All forecasts are given through to 2031 and include quantities such as EV battery demand, battery thermal management strategy, thermal interface materials, electric motor demand and Si IGBT or SiC MOSFET inverters. charging is a key trend in the EV market. Range anxiety becomes less of an issue if a vehicle can be charged in less than 30 minutes. Several vehicles have entered the market with this capability. More examples are emerging for 800 V systems too with the likes of the Porsche Taycan/ Audi e-tron GT platform as well as the new Hyundai E-GMP architecture. These higher voltages also help enable faster charging. However, thermal management is a key consideration for fast charging, keeping the batteries cool during this process helps increase the longevity of the cells but is also a major safety feature to prevent thermal runaway. For this reason, we have also seen interest in more novel technologies like immersion cooling.

In 2020, there was a great emphasis on EV fires and manufacturers like Hyundai and GM had to recall nearly 100,000 vehicles each. The estimated cost of these recalls was $900 million for Hyundai and $1.2 billion for GM, not to mention the harm to the reputation of their EVs and EVs in general. Whilst it is generally agreed that EV fires are less common than combustion vehicle fires, the EV fires tend to be much more severe and as more of an unknown quantity, gain more attention from the media.

Detection and prevention of thermal runaway are extremely important, especially as regulations around EV safety start to be enforced. This also gives opportunities for fire-retardant or fire insulation materials to prevent or limit the progress of fire outside of the battery pack. Given there is no consensus on the design of an EV battery cell or pack, this makes the EV market an interesting landscape of potential for thermal management and fire protection component and material manufacturers.

Much like the batteries, there are several designs for cooling electric motors. The majority of the market is using permanent magnet-based traction motors with magnets that risk denaturing or becoming brittle at high temperatures. Even for motors without permanent magnets, the stator windings will increase in resistance at higher temperatures leading to decreased performance and lifetime as well as the potential to damage surrounding components.

As manufacturers strive for higher efficiencies and power density, there are many developments and innovative designs such as the Audi e-tron’s internal rotor water-glycol cooling system. The IDTechEx report covers thermal management of electric motors with EV use-cases, emerging technologies and a forecast of demand for EV traction motors.

Power electronics are often overlooked, but the main inverter is often the hottest component in an EV under normal operating conditions. Most of the market is using Si IGBTs which certainly generate significant heat and require effective thermal management which is often integrated into the motors coolant system. In recent years, we have seen significant adoption of SiC MOSFETs in the main traction inverter.

This leads to higher switching frequencies and hence higher efficiency. The use of SiC also decreases the footprint of the package leading to higher power density and in turn a greater challenge in heat dissipation. In addition to the liquid cooling of these components, we see trends around the wire bonding, die-attach and substrate technology within the inverter packages themselves. Each OEM has its own strategy for power electronics and their implementation of options such as thermal interface materials. IDTechEx’s latest report includes trends in power electronics design as well as several EV use-cases and forecasts the demand of Si IGBT and SiC MOSFET units.