Nanotube film could heat electric cars without draining their batteries

Nanotube film could heat electric cars without draining their batteries
A sample of the film, as seen by a thermal imaging camera
A sample of the film, as seen by a thermal imaging camera
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A sample of the film, as seen by a thermal imaging camera
A sample of the film, as seen by a thermal imaging camera

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

It may be an improvement over copper wire elements. But most of these electric cars have air conditioning. They can simply be run in either direction for heating or cooling with no additional weight. A heating element has a coefficient of performance of 1, whereas a heat pump is 4 to 5, hence far more power efficient. I can only see this technology as useful where you have a simplistic electric car that has no air conditioning.
The reason that EVs don't work very well in places with cold weather has nothing to do with "their battery is powering not only the motor, but also the cabin heating system." The real reason is one of simple science, and the same reason ICE car batteries don't work as well in cold weather. When batteries are cold, the chemical reaction necessary for it to generate power is slowed, and so they don't charge or discharge as well. That makes ICE cars slower to start in very cold temps, but after they get started it doesn't matter too much, because their power is coming from the engine, not the battery. On the other hand, EVs rely on batteries for 100% of their power, so if they are chilled to a very cold temperature, they won't produce nearly as much power to drive the vehicle and operate its accessories. In addition, since they may be getting charged in similarly cold temperatures, they also will not be able to charge as effectively, and won't have the power expected when the operator tries to use the vehicle. Running the heater during the winter not only doesn't shorten the range by running down the battery, it extends the range by warming the battery pack. That is why Teslas have a battery heater that runs when it gets cold.
If you want to see proof of this in action, on a very cold week, put an EV in a heated garage and charge it overnight. Then check the range in the morning and drive it to work. Park in an outdoor unheated area, and check the remaining range. When you come out 9 hours later, you will find that your range has dropped off dramatically from what it was when you went inside, even though the car was turned off.
This always has been one of the big disadvantages of EVs in cold areas.
While not disputing the science either way I would dispute the point of placing the heating surfaces in the cabin of the car. The added complexity of shaping the material to those surfaces seems inefficient compared to creating a densely packed area to heat air before it enters the cabin or to pass the cabin air through. Recycled air quickly becomes stale when recycled in that way and preheating fresh air in its way in is often much preferred.
Tom Lee Mullins
I think this is great for electric vehicles and fuel cell vehicles.
Don Duncan
The most efficient solution to temp control is foam/foil/insulation (poly-iso). Add glass that can let in IR or block it, as needed. PV imbedded on as much surface as practical is helpful.
It would be cheaper to install a small ICE and generator to supplement the electrical charge of the EV's battery pack and extend its' range. - Utilize the ICE's waste heat to keep the batteries and passenger compartment nice and toasty. - Warm batteries will increase the EV's range. - Use propane or butane to run the ICE to minimize exhaust pollution and engine maintenance. - Make the whole system easily removable so during warm weather you can lighten the vehicles weight and increasing range; unless of course somebody comes up with a feasible way to utilize the ICE's waste heat to cool the cabin and batteries.