The demand for electric vehicles (EVs) is increasing in tandem with the worldwide push toward greener solutions independent of fossil fuels.
However, one of the prevailing challenges to roll out new EV technology is thermal management. The thermal management systems (TMS) of EVs, in particular, face tougher challenges than those in contemporary internal combustion engine (ICE) vehicles, especially when considering all the various parts that require thermal management.
Different areas in which thermal management is necessary for EVs. Image used courtesy of ATOMS Laboratory and the University of Toronto
The problem of TMS has not eluded engineers, and there are several ways companies are looking to solve design-level challenges associated with heat.
Challenges of a Thermal Management System in EVs
Managing the heat of a vehicle optimizes the engine’s performance; improves the overall safety of the vehicle; and maximizes battery charging speed, longevity, and overall lifetime.
On this last point, a recent report from IDTechEx mapping EVs’ thermal management from 2020 through 2030 emphasizes how batteries face unprecedented challenges when operating in cold conditions. This challenge can reduce capacity in the short term while accelerating cell degradation and decreasing cell efficiency in the long term.
Thermal runaway is a real fear for batteries. This effect occurs when a single cell within a battery pack becomes too hot, which can cause neighboring cells to ignite in a fire, or in more severe cases, an explosion.
Thermal runaway in Li-ion batteries. Image used courtesy of Elmelin
Though automotive manufacturers currently implement a number of TMS solutions in EVs, there are still many research fields in battery and power electronic development that can be explored.
Current Solutions for TMS: Tesla, BMW, and Toyota
IDTechEx points out a number of thermal management solutions companies currently employ:
- Tesla: Cylindrical cells in battery packs, including an interweaved water-glycol coolant circuit
- BMW: Prismatic cells with a large plate cooled by refrigerants underneath it
- Nissan and Toyota: Older air-cooling technology
While water-glycol, air, and oil are the common fluids used in these systems, new technologies and refrigerants are being explored. Active cooling via fluids must be intricately designed to aid in the practical and equitable flow of heat throughout and away from the engine. Maldesigned liquid cooling systems can actually cause more thermal issues—for instance, creating hot spots.
Outlook on the popularity of liquid or refrigerant cooling vs. air cooling over the next 10 years. Image used courtesy of IDTechEx
These cooling design challenges have inspired many engineers to focus on component materials to assist in thermal management.
Material Research to Combat Thermals
Beyond the cooling agents in the engine, power electronics play a role in managing EV thermals because they can effectively distribute heat throughout the engine. For this to occur, the parts must have thermal interfaces with minimal thermal resistance.
Because EV engines are exposed to more coolants and higher temperatures than ICE vehicles, manufacturers have heavily investigated heat-resistant materials for TMS. One example comes from DSM, where the company uses its Xytron G4080HR technology to enhance a popular EV TMS material, polyphenylene sulfide (PPS) resin.
A chart depicting exposure temperatures vs. exposure times of different materials used in TMS. Image used courtesy of DSM
When using this Xytron solution, PPS was able to withstand the harsh environments of an EV, providing good material characteristics in an engine and maximizing its thermal efficiency.
Thermal Management for EV Motors
Another manufacturer investigating thermal management solutions in power systems is TDK, which recently released the HVC 4222F and HVC 4422F Arm M3-based motor drivers with 32k and 64k flash memories, respectively.
Some of the characteristics that keep these chips cool include:
- High-temperature resistance rated to operate in applications around 150°C
- Six half-bridge drivers that can pump out 500 mA of current
- ADC for internal and external measurements via GPIO that pairs with a myriad of sensors
- DAC capable of setting a programmable current limit between 2 mA and 500 mA
- The capability to communicate via the LIN 2.1 and LIN 2.2A protocol
TDK envisions these motor drivers appearing in radiator grille shutters, smart valves/pumps, and LIN bus-connected actuators—all of which can create heat in an EV power system.
Keeping EVs Cool for Faster Adoption
The challenge that EVs present on a thermal level is much more complex and significant than an ICE vehicle. Still, as designers continue to assess cooling systems for battery cells, invest in materials science research for power electronics, and optimize thermal management in EV motors, in particular, it’s possible that EV adoption may accelerate at an even faster rate.
What’s Hot in EV Design?
Catch up on more EV advancements that pertain to TMS challenges.