Lube-Tech
will heighten the importance of the phenomenon of local heating, especially given the thermal losses associated with these conditions. The probability of electronic components suffering damage at higher temperatures makes enhancing thermal management and efficient heat extraction from these components essential for the longevity of the whole.
Today, these components are frequently cooled by specific water-cooling plates. This system risks reaching its limits very quickly, however, so it is possible to combine it with direct cooling of those components that generate the most heat [9], although this raises the same problems described above in relation to electric motors. Here again, performance is a function of the fluid’s thermal properties, the aforementioned optimisation of which and the attention that has been paid to them in recent years are in this case quite significant. Some manufacturers tend to incorporate their power electronics in the motor-reducer unit which is a solution that calls for a specific fluid that covers several components. This pooling of different functions is a further pointer to the value of the research that has been undertaken in recent years.
Given that power electronics were previously of limited interest to the lubricants industry, new tools needed to be invented in order to make progress and guarantee the pertinence and sustainability of the different solutions proposed. The same observations apply to battery thermal management fluids which are a potential source of innovation for the automobile industry.
Battery thermal management fluids All the techno-economic analyses conducted with regard to electric vehicles emphasise the essential role played by their batteries. Figure 3 (below) draws its inspiration from the data contained in a paper by Kampfer et al [10] to show relative costs of the different elements that make up battery electric vehicles.
28 LUBE MAGAZINE NO.168 APRIL 2022
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.139 page 3
Figure 3: Proportion of the costs represented by each family of assemblies, according to Kampfer et al [10].
Any innovation that extends battery life plays a part in lowering TCO (Total Cost of Ownership), but the duration of a battery’s life is directly influenced by its temperature history. Batteries that heat excessively or frequently reach very high temperatures can suffer damaged or have their working life shortened. It is for this reason that charging rates are capped, especially in the case of high-power charging stations. Battery thermal management is consequently of the utmost importance for automobile manufacturers who, on the one hand, want to extend battery life, but are looking to shorten charging times on the other. This was one of the main topics raised at events like Tesla’s Battery Day and Volkswagen’s Energy Day.
Working actively on this issue, the first step was to undertake a detailed review of existing solutions. Table 1 below indicates the different existing battery thermal management systems and solutions currently being developed (for further information about these technologies, please refer to reference [11]). A brief analysis makes it clear that these systems are unable to handle very high loads.
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