An Electric Car Heater Can't Be Too Thin or Too Economical

Just about every electrical device seems to want to slim down to a thin film—if possible, one that includes carbon nanotubes. Now Fraunhofer has accomplished both feats, and with the most basic device imaginable: a heating element.

It is very thin and very economical with power.

Its first application will likely be as a heater in an electric car, which, unlike conventional vehicles, can’t exploit the warmth of air that’s been passed over an internal combustion engine. But standard car heaters, which use a matrix with embedded copper wire (often in seats or in the steering wheel), are power-hungry. That’s why today’s drivers of e-cars must either shiver or drain their car’s already stressed-out batteries.

“In the most unfavorable case, you can only drive half the usual distance with the car” when using the heater, says Serhat Sahakalkan, who’s managing the project for Fraunhofer’s lab in Stuttgart.  

The idea is to mix nanotubes into a fluid to create a slurry, lay down a film just a few micrometers thick on a suitable substrate, and run a current through it. The heat-generating resistance comes mainly from the passage of current through gaps between the nanotubes.

Because the tubes conduct heat so well, they store very little of it, and thus can begin to radiate comforting infrared rays right away. That feature would be particularly welcome during short trips. And, because the tubes form a vast network, a local defect wouldn’t shut down operation the way it would in a heater that used copper wire. 

Right now, Fraunhofer is putting the film on small panels that can be glued to the inside of a car’s door, but eventually it expects to be able to spray it directly onto such surfaces. The company will show off the system next week at the International Motor Show in Frankfurt.