Nanotube film could heat electric cars without draining their batteries

A sample of the film, as seen by a thermal imaging camera(Credit: Fraunhofer)

While some electric cars may have a decent range in places like California, they're not so impressive in locations with frigid winters. That's because their battery is powering not only the motor, but also the cabin heating system. Now, however, engineers at Germany's Fraunhofer Institute for Manufacturing Engineering and Automation are developing new technology that could keep EV drivers warm, without leaving them stranded.

In regular internal combustion vehicles, much of the heat needed to warm the interior is generated by the engine. Because EVs' motors don't get nearly as hot, the cars' cabins generally incorporate things like silicone heating mats with integrated conductive copper wiring. These can be bulky and heavy, however, plus they stop working if any of the wires are damaged, and they still draw a lot of power from the battery.

Instead, the Fraunhofer team has created thin films covered with carbon nanotubes. These films are glued to surfaces such as the interior door panel arm rests, and have an electrical current run through them. As that current moves through the film, it generates heat as it encounters resistance between the individual nanotubes.

Because the film itself doesn't store much heat, the warmth that's generated is quickly and efficiently released into the cabin. The material also cools quickly once the current is switched off. As a result, the nanotube film reportedly uses much less power than copper wire-based systems, it's considerably thinner and lighter (it's just a few micrometers thick), plus localized damage to the film won't negatively affect the function of a whole sheet.

Additionally, as with existing heating systems, users can control how much heat the Fraunhofer system puts out.

In its present form, the film must be applied to curved surfaces in individual pieces to keep it from crinkling. Down the road, however, the researchers hope to be able to spray the nanotubes directly onto such surfaces – this would make the technology both easier and cheaper to integrate into vehicles.

The company will be presenting the system later this month, at the International Motor Show in Frankfurt.

Source: Fraunhofer

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