BOSTON, Dec. 1, 2023 / —
Thermal management of EVs: Batteries take focus but motors and power electronics followÂ
The battery deservedly takes the major focus when it comes to technology development in EVs. But an EV’s powertrain has to act holistically to operate with optimal performance and interact with the passenger cabin’s conditioning system. This means that the thermal management of the motors, power electronics, and how this all interacts is just as important as the battery.
The early EV market trend was away from passively cooled or forced air cooled batteries towards liquid cooling through cold plates and coolant channels. This transition is all but complete with IDTechEx finding that 95% of the electric car market has adopted cold plate cooling (water or refrigerant) in the first half of 2023. The next stage of evolution is around battery integration, with cell-to-pack and cell-to-body type designs becoming increasingly common. This typically involves larger form factor cells and somewhat reduces the complexity of the cold plate design. For example, BYD’s Blade battery requires one large cold plate for the entire pack. Tesla’s 4680 pack requires fewer coolant channels for side wall cooling its cells thanks to fewer individual cells being used in the pack.
This also profoundly impacts the thermal interface material (TIM) use. Firstly there is a lower quantity per vehicle, but as cells can be bonded directly to the cold plate, the TIM has to provide greater adhesion properties. IDTechEx’s research finds that despite the reduction in TIM quantity, the price of the thermal conductive adhesive is higher than that of a typical gap filler, meaning similar revenues per vehicle can be obtained for TIM suppliers. Combining this with the growing EV market, IDTechEx predicts a 5.6-fold increase in yearly revenue for TIM by 2033 compared to 2022.
Cell-to-pack/body deployment is still at an early stage, with IDTechEx estimating that approximately 15% of the electric car market utilized a cell-to-pack or cell-to-body design in 2022. The market is somewhat split on development, with large Chinese players and Tesla in the US focusing heavily on cell-to-pack and greater integration, whilst some players have taken a module-based approach, like GM with its Ultium platform, that can potentially aid in servicing.
Electric motors present a different thermal management challenge; while water jackets around the motor have been common, the trend is towards motors that use oil within them. This allows for more direct contact between coolant and motor windings but also a smaller overall motor if the jacket is eliminated. Oil-cooled motors overtook water jacket-cooled motors in 2022, with the growth continuing into 2023, with estimates for H1 2023 approaching 65% of the market. IDTechEx expects both approaches to remain but with oil cooling taking the majority for the future of the market, especially for higher cost/performance models.
With motors moving to direct oil cooling, is it possible that the same could be seen for power electronics? The adoption of silicon carbide power electronics results in a larger heat flux at the MOSFETs (over silicon IGBTs) thanks to the higher power density. Typically, the inverter and motor are housed together in the drive unit, with the same water loop cooling both components. There has been some interest in directly cooling the inverter chips with oil too, to provide better thermal contact, but this could also eliminate the water circuit from the drive unit. A single water/oil heat exchanger could therefore be used to contact the thermal system of the vehicle with the drive unit. The SingleOilCnL project between Dana, Diabatix, Lubrizol, Siemens, and Flanders Make explores this idea. IDTechEx believes this is a promising approach but is unlikely to become a dominant solution in the near future. However, with greater adoption of SiC power electronics and more highly integrated drivetrains, we could start to see some examples later in the decade.
What can be done to mitigate EV fires?
The concerns around EV fires are still at the forefront of both the EV industry and, now more than ever, the public eye. The automotive market experienced significant recalls relating to battery fire risks from automakers such as GM, Hyundai, VW, and several others. More and more data has been published suggesting that EVs are at significantly less risk of a fire than a combustion engine vehicle, although it should be noted the data at this stage does not account for factors like the age of the vehicles. The market has made several moves overall to combat the likelihood of EV fires, such as more stable chemistries, greater quality control of batteries, and improved software management.
Regardless of the occurrence rate, EV fires can be very destructive and quite different from their combustion engine counterparts. The combination of volatile chemicals and the mechanism of thermal runaway can make fires explosive and difficult to extinguish. This is one of the major drivers behind IDTechEx’s prediction that demand for fire protection materials in EVs will grow by 13 times by 2033 compared with 2022.
Despite the focus, regulations have evolved fairly slowly. China was the first (01/01/2021) to mandate a 5-minute warning between a thermal event occurring and fire or smoke exiting the pack, allowing occupants to exit the vehicle. Other regions have had draft regulations in progress for several years, but these often struggle to keep up with the rate of technology development in this field. The UN GTR 20 regulation looks to include similar escape times but also add features like testing gas release risks while the vehicle is turned on or off. However the regulation specifics play out, it will surely put more pressure on OEMs to provide propagation mitigation and detection approaches along with overall fire protection.
There are many materials that can provide protection from thermal runaway in a battery pack. In general, especially with more energy-dense battery designs, these materials should provide multiple functions, including thermal insulation, fire protection, electrical isolation, and cell mechanical support. The market so far has largely employed materials like mica sheets or ceramic blankets at a module/pack level to provide electrical isolation and fire protection; this was often the case even before regulations and greater awareness of EV fires progressed. When Tesla first released the Model 3, it shifted towards using encapsulating agents around its cells to eliminate oxygen within the pack and add fire protection. The variety in battery designs and the need to keep weight and cost low is seeing manufacturers consider several options.
One material that has seen rapid market growth is aerogels. Aerogels provide excellent thermal insulation with minimal weight, but their maximum temperature protection and higher cost has historically limited their uptake. IDTechEx’s “Aerogels 2024-2034” report found that the total aerogel market in 2020 was under US$300 million, with less than 10% of this accounted for by the EV market. In 2022, aerogel application within EV battery packs became a US$150 million market by itself. IDTechEx expects aerogels to become one of the standard options in this application, alongside several other material options.
Thermal management for data centers
Over the last 17 years, GPU thermal design power (TDP) has surged fourfold. The growing demand for cloud computing, crypto mining, and AI suggests TDP of chips will continue to rise. In 2023, chips with TDP near 1000W already exist. This trend presents significant challenges for data center thermal management. Traditional air-cooled setups using fan walls and air conditioning struggle when TDP exceeds 500W. As a solution, liquid cooling has emerged, encompassing direct-to-chip and immersion cooling. Direct-to-chip cooling notably boosts cooling capacity and can be relatively easily integrated into existing air-cooled data centers, facilitating a gradual transition for end-users.
IDTechEx has observed industrial collaborations between liquid cooling solution providers and critical supply chain components, including chip manufacturers (Intel, AMD, Nvidia, Broadcom), server manufacturers (Dell, Gigabyte, Lenovo, Inspur, Hewlett Packard Enterprise), system/infrastructure integrators (Vertiv, Schneider Electric), and data center end-users like Meta, Microsoft, and Verizon. Driven by tech giants, IDTechEx projects the data center liquid cooling market to surpass US$900 million by 2033.
Immersion cooling opportunities: EVs and data centers
Currently, immersion cooling for data centers is in its early stages due to limited demand, successful cases, and industrial expertise. However, IDTechEx has observed notable pilot projects led by major companies. In 2021, Microsoft introduced pilot projects using two-phase immersion cooling for its Azure cloud services. Being the first cloud provider to employ two-phase immersion cooling in a production environment, Microsoft intends to continue its use in the long term. Similar trends are happening with other players; for example, Meta partnered with Iceotope to transition a standard high-density storage from air cooling to single-phase immersion cooling in 2022. Additionally, Minerbase, a leading cryptocurrency mining solution provider, launched an immersion cooled data center in May 2023.
While debates persist regarding liquid costs and PFAS regulations, IDTechEx believes that applications requiring high-performance computing are likely to adopt immersion cooling more rapidly, opening substantial market opportunities for coolant suppliers, hardware manufacturers, end-users, and other entities within the supply chain. IDTechEx’s report “Thermal Management for Data Centers 2023-2033: Technologies, Markets and Opportunities” finds that the annual revenue of the data center immersion cooling industry will triple between 2022 and 2033.
Immersion cooling is also gaining much attention for electric vehicle batteries. Whilst immersion can provide greater thermal homogeneity for the cells and eliminate cold plates and TIMs, it has some major challenges to greater adoption. First is the greater fluid pumping pressure needed due to the lower thermal conductivity of the fluid. Second is the extra spacing required between the cells for fluid flow. There is also the challenge in effectively sealing the batteries to avoid leaks.
There are several examples of high-performance or high-cost EVs using or planning to use immersion cooling, such as Mercedes-AMG and McLaren. There are also partnerships between technology developers and coolant suppliers, but for the reasons outlined above, IDTechEx predicts that immersion cooling will be largely limited to applications that require power-dense but not very energy-dense battery packs. Despite this, a small portion of the growing EV market is still significant, with IDTechEx’s “Thermal Management for Electric Vehicles 2023-2033” report predicting an 8-fold increase in fluid demand between 2022 and 2027 across EV segments.
IDTechEx offers a number of in-depth research reports on thermal management, and all the expert-led data and analysis on this topic is available as part of a market intelligence subscription. For more information please visit www.IDTechEx.com.
This article is from “Technology Innovations Outlook 2024-2034”, a complimentary magazine of analyst-written articles by IDTechEx providing insights into a number of areas of technology innovation, assessing the landscape now and giving you the outlook for the next decade. You can read the magazine in full at www.IDTechEx.com/Magazine.
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