Potential of esters as coolants in electric vehicles adapted from use in transformers

Authors: HUANG, CINDY - Stony Brook University; SHAH, RAJ - Koehler Instrument Company, Inc; Erhan, Sevim; Sarker, Majher; KARMAKAR, GOBINDA - University Of North Bengal; Sharma, Brajendra

Submitted to: Energies
Publication Type: Review Article
Publication Acceptance Date: 7/31/2025
Publication Date: 8/5/2025
Citation: Huang, C., Shah, R., Erhan, S.Z., Sarker, M.I., Karmakar, G., Sharma, B.K. 2025. Potential of esters as coolants in electric vehicles adapted from use in transformers. Energies. 18(15). https://doi.org/10.3390/en18154145.
DOI: https://doi.org/10.3390/en18154145

Interpretive Summary: With the increasing popularity of electric vehicles, the need for effective and efficient lubricants and coolants has become crucial. This review highlights the current challenges of coolants performing dual functions, cooling as well as lubricating, necessary for electric vehicles. The adoption of vegetable oils in direct immersion cooling systems presents a viable solution for the thermal management of electric vehicles. The benefits of natural esters, including fire safety, cost, and environmental friendliness, make them highly attractive compared to traditional coolants. However, they still have some pitfalls like poor oxidative stability and cold flow behaviors, which can be overcome through proper chemical modification and blending with suitable fluids and additives.

Technical Abstract: With the increasing popularity of electric vehicles, the need for effective and efficient driveline lubricants and dielectric coolants has become crucial. This review primarily highlights the current challenges of coolants performing dual functions, cooling as well as lubricating, necessary for "wet" e-motors of electric vehicles. The adoption of natural fatty esters of vegetable oils in direct immersion cooling systems presents a viable solution for the thermal management of electric vehicles. The benefits of natural esters, including high dielectric strength, fire safety, cost, and environmental friendliness, make them highly attractive compared to traditional coolants. But they still have some pitfalls like poor oxidative stability, poor fluidity at lower temperatures (pour point), which can be overcome through proper chemical modification. Continued research and development are necessary to overcome the challenges and optimize esters for widespread use in the rapidly expanding electric vehicle market.