Thermal Management for EVs: Cooling Systems Down

Water-glycol, oil, and refrigerants are the three main fluid types necessary to maintain electric vehicle (EV) thermal management systems. IDTechEx's report, "Thermal Management for Electric Vehicles 2025-2035: Materials, Markets, and Technologies", focuses on the main benefits and challenges of these varying coolant options, alongside market players, forecasts, and predictions over the next ten years.

 

Thermal management systems in an EV are all linked and consist of a lower-temperature cooling loop for the car's battery, a high-temperature cooling loop for the drive unit, electric motor, and power electronics, and the AC refrigerant loop which keeps the cabin temperature suitable for passengers.

 

 

In immersion cooling, all of the battery cells are immersed in dielectric fluid, which ensures good thermal contact between the cells and the coolant; this method is known for improving the battery's longevity through good thermal performance capabilities.

 

Two major categories of immersion fluids include hydrofluoroethers, and ester, hydrocarbons, and oils. While hydrofluoroethers are not flammable, they have lower thermal conductivity and can be heavy and expensive, with concerns around PFAS also acting as a barrier to their use. the second category, incorporating hydrocarbons, includes more promising materials for immersion, as they are lighter, cheaper, and have higher thermal conductivity, although may have a lower flash point.

 

However, immersion faces key challenges - the lower thermal conductivity and specific heat of immersion fluids means that a greater fluid flow rate with higher pressure pumps is required. There is also a need for a sufficient gap between cells for the fluid flow. Pumping components, sealing, and chemical compatibility are other barriers to overcome for immersion, though it will still remain a small market with opportunities within specific vehicle segments, some of which are outlined in IDTechEx's report.

 

 

Water-glycol cooling was one of the earliest methods, where the fluid was passed through a water jacket that sits around the stator of the motor. However, this method doesn't achieve good contact with the components within the motor. Despite methods moving away from this, water-glycol is still a dominant fluid within EVs, used in battery cooling and connecting the entire thermal management system.

 

As of 2022, oil cooling became a main strategy for motor cooling and is currently seen to be used in the majority of EVs, including models from Tesla, Hyundai, BYD, and more. IDTechEx states in its report that future markets are expected to remain focused on oil cooling systems.

 

 

Air cooling dominated the battery cooling market a few years ago but was overtaken by active cooling (using indirect liquid cooling methods) due to its ability to keep the cells at a more optimal temperature range, enabling greater battery longevity and faster charging. According to IDTechEx, this method is expected to be just as popular over the next decade, with trends predicted to be similar except for a small increase in immersion for niche applications. The use of refrigerant in battery cooling systems has also grown largely due to BYD's uses in China. Despite it being necessary for cabin thermal management, there are concerns around PFAS in current solutions, so new alternatives are on the rise with carbon dioxide heat pumps in use already and propane heat pump systems moving towards commercialization, these are more environmentally friendly options.

 

 

In their report on the topic, IDTechEx reports that 880 million Liters of fluid will be required for BEV and PHEV cars in 2035 and predicts that the EV market may shift its interest towards lower conductivity fluids. The use of oils may look slightly different going forward, as dropping viscosity could become popular to increase thermal performance through higher conductivity and specific heat capacity.

 

To find out more about IDTechEx's "Thermal Management for Electric Vehicles 2025-2035: Materials, Markets, and Technologies" report, including downloadable sample pages, please visit www.IDTechEx.com/TMEV.

 

For the full portfolio of thermal management market research available from IDTechEx, please see www.IDTechEx.com/Research/Thermal, and for the full portfolio of electric vehicles market research available, please see www.IDTechEx.com/Research/EV.

IDTechEx provides trusted independent research on emerging technologies and their markets. Since 1999, we have been helping our clients to understand new technologies, their supply chains, market requirements, opportunities and forecasts. For more information, contact research@IDTechEx.com or visit www.IDTechEx.com.