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Battery cooling technologies

There are currently available a few battery cooling technologies available, which depend mostly on the battery type and architecture:

  • Li-ion: prismatic, cylindric, pouch, Z-type 
  • Semisolid state: prismatic, cylindric; etc

Air cooling

Air cooling is a form of heat dissipation that uses low temperature air as a medium to reduce the temperature of a battery by heat convection. This is an older technology and still widely used mostly in electric buses and electric logistics vehicles. Similarly to air cooling in data centers, the ambient temperatures influence the cooling process and energy efficiency is rather low.

Direct cooling

Direct cooling involves the use of refrigerants to evaporate latent heat, creating an air conditioning system in the vehicle or battery system and installing the evaporator of the air conditioning system in the battery system. This type of system is used mostly in passenger cars.

Two phase evaporative cooling

Classical cooling solution using a refrigerant and a secondary loop of glycol, connected with the vehicle’s air conditioning system. It can use either a fluorinated refrigerant or transcritical CO2 cycles (at very high pressure).

Liquid cooling

Liquid cooling is used to reduce the battery temperature by indirectly exchanging heat with the battery through the cooling fluid and carrying away the heat generated by the battery. The functioning principle is indirect or direct contact with the cooling liquid: either cooling channels or cold plate using ethylene/propylene glycol or full immersion in dielectric liquids. The indirect cooling (with the glycol loop) is currently the mainstream technology used in many passengers’ electric vehicles, including Tesla, BMW-i3 and Chevrolet Volt.

Immersion cooling

However, electric vehicles will trend toward batteries that have a greater autonomy, thus, will generate higher levels of heat, and therefore the industry shifts to more effective cooling technologies, like immersion cooling[1]. Immersion cooling for batteries in electric vehicles functions on the same principle as similar techniques being developed for data centers: the battery pack is fully immersed in a dielectric liquid that is highly effective at removing heat and ensuring temperature uniformity.

Figures suggest promising results with faster peak charge rates, longer battery lifetime, lifespan and safety.[2][3]. The solution addresses not only passenger car, but also logistics and commercial vehicles, heavy duty, industrial vehicles, aerospace and maritime transport.

HFOs and HCFOs are key components of dielectric fluids used in immersion cooling technologies, due to their technical properties. Emissions during use are expected to be very low (virtually zero) due to the systems’ design. End-of-life of vehicles and batteries it is also fully addressed in the European legislation[4],[5].

The EU Fit for 55 estimates that transport is responsible for 25% GHG emissions in the EU, with road transport holding the biggest share[6]. Wider adoption of electric transport will be enabled by development of new technologies that can ensure faster charging, extended battery life, safer operation and smaller, lighter weight, lower cost batteries in EV and hybrid vehicles.

According to IDTechEx’s report[7], “Thermal Management for Electric Vehicles 2023-2033”, liquid cooling gained dominance at the expense of air cooling between 2015 and 2022, the projected demand for EV cooling fluids will increase 8-fold between 2022 and 2027 and the emergence of fast charging will make immersion cooling the option of choice in EVs.