Large fluctuations in outdoor temperatures can shorten the lifespan of the batteries used in electric cars – if those cars are parked outside, that is. An experimental new car-cloak could help minimize such damage, by damping changes in temperature.
The Janus thermal cloak, which is used like a regular car cover, is being developed by a team at Shanghai Jiao Tong University.
It takes its name from the ancient Roman two-faced god Janus. The cloak's two "faces" consist of an outer layer that reflects solar heat back out into the atmosphere, along with an inner layer that reflects residual car-heat back into the vehicle.
The outer layer incorporates thin silica fibers coated in flakes of hexagonal boron nitride, which is a graphite-related ceramic that boosts solar reflectivity. Those fibers are braided and woven into a base fabric, which is bonded to the aluminum-alloy inner layer.
In outdoor tests conducted in Shanghai, a cloak-covered electric car stayed a total of 7.8 °C (14 ºF) cooler than the outdoor daytime temperature. At midnight, after the ambient temperature had dropped considerably, the covered car stayed 6.8 °C (12.2 ºF) warmer than the outdoor temperature.
The cloak was designed with commercial-scale production in mind, as all of the materials are claimed to be inexpensive, lightweight, durable and – as an added bonus – fire-retardant.
A paper on the research, which is being led by Prof. Kehang Cui, was recently published in the journal Device.
Source: Cell Press via EurekAlert