Thermal Cloak Protects EVs in Various Temperatures
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Researchers have developed an overgarment for electric vehicles (EVs) called the Janus thermal cloak in an effort to preserve batteries. Made mainly of aluminum and silica, the cloak can heat an electric vehicle during a cold night and cool it on a hot day. The cloak can also operate without external energy input or modification between cold and hot weather.
The Janus cloak's inner layer entraps heat, and its outer layer reflects sunlight. It also emits any heat absorbed by the outer layer in a way that it can be easily dispersed to outer space.
The cloak’s outer layer contains thin fibers of silica that were covered in flakes of hexagonal boron nitride, woven into a fabric, and adhered to the inner layer made of aluminum alloy. The researchers purposely used these materials to make the cloak because of their low cost, light weight, durability, and fire retardancy.
Senior author and materials scientist Kehang Cui described the thermal cloak as “clothes for vehicles” and likened it to the Earth’s atmosphere, which covers the planet and is transparent to a specific range of electromagnetic energy. According to Cui, this process only works for cooling, which meant the researchers had to develop a way for the cloak to heat an EV in the winter. Their solution came in the form of an effect called “photon recycling,” which takes trapped energy under the cloak and bounces it between the cloak and the vehicle.
The team tested the thermal cloak’s effect with electric vehicles parked outside. By mid-day, the cabin temperature of the car with the cloak measured 22.8 to 22.7 degrees Celsius lower than the exposed car and 7.8 degrees Celsius cooler than the outside temperature. The cloak-covered EV also measured 6.8 degrees Celsius warmer than the outside temperature at midnight.
