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BMW Experimenting With Infrared Heating For Electric Cars

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BMW i3 Concept MkII

BMW i3 Concept MkII

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Just how do you keep occupants of an electric car warm? 

That’s the question that automakers have been tackling for many years, as they bring mass-produced plug-in cars to market.

Now BMW thinks it has the solution to keeping occupants warm in the middle of winter: infrared heating.

The use of infrared heating was recently discussed by BMW engineers at a recent BMW innovation day event.

Using targeted infrared radiation, BMW believes it can develop a system for electric cars that heat passengers directly, keeping them warm without wasting heat heating the rest of the car.

In order to explain why this might be useful in an electric car, however, it’s worth taking a few moments to explain how traditional gasoline cars are heated.

In traditional gasoline cars, the inefficient engine produces a lot of waste heat and noise. 

BMW i3 and i8 preview, New York City, November 2011, photo by Tom Moloughney

BMW i3 and i8 preview, New York City, November 2011, photo by Tom Moloughney

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In order to keep the engine cool, liquid coolant is circulated through pipes in the engine block, transferring some of that excess heat to the coolant. The coolant is then sent to the car’s radiator, where heat is transferred to the outside air via convection. 

In the winter, hot coolant from the engine is first circulated to the heater matrix. A little like a small radiator, it too transfers heat from the coolant to the air passing over it using convection. But unlike the radiator, the heater matrix then pumps that warm air into the car’s cabin, warming the interior and passengers. 

Because electric motors are very efficient, they produce very little excess heat, meaning there is no waste heat to warm the car in winter. 

That means automakers have had to build heating systems to keep the cabin and occupants warm. 

So far, these generally either heat the air in the cabin with a resistive heating element, or use a liquid heating element to heat an enclosed heating system, which can then be passed through a conventional heater matrix as is done in a gasoline car. 

A more efficient solution, as used by Renault in its upcoming 2013 Zoe, is to use a sophisticated heat pump. 

Even then, heat energy is being transferred through air, meaning it is still relatively inefficient. 

In contrast, infrared heaters use electromagnetic radiation to transfer heat energy, meaning heat energy is transferred only when the electromagnetic wave hits an object.

Because it doesn’t heat the air it passes through, and can be highly directed like any electromagnetic radiation, infrared heating is far more energy efficient than conductive or convective heating.

What’s more, the system can be used to heat parts of a car selectively, meaning it only warms the part of the car being used, not empty passenger seats. 

Ultimately, the less energy spent on heating the car and its occupants, the further it will be able to travel in winter.

While BMW is investigating the use of infrared heating in future electric cars however, it believes using a heat pump is a more likely next step, reducing the energy consumption of in-car heating so much that it could improve range by up to 30 percent against an air-heated electric car. 

For now, it views infrared heating as a supplemental heating system, offered as an optional extra in the same way that heated seats are. 

BMW currently has no plans to offer infrared heating in any of its plug-in cars, but even as a theoretical possibility, it hints at a future where electric cars do not waste huge amounts of battery energy keeping occupants warm in cold winters. 

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Comments (9)
  1. While reading this article, I couldn't help but to think of a turkey cooking in the oven :)
     
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  2. "infrared heaters use electromagnetic radiation to transfer heat energy, meaning heat energy is transferred only when the electromagnetic wave hits an object."

    I hope it is more like the Halogen Warming lamp installed around showers instead of the Microwave Oven...
     
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  3. Sure, in California you may not need it, but here in Michigan, we may need the microwave version for the winter...

    Actually a common sense idea that isn't as far out there as some may initially assume. Not quite there yet, but actually a good step in being more efficient and not wasting energy/heat. Let's see where this leads in the next 4-6 years or so...
     
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  4. Hey, if you go to Lake Tahoe during the winter, you will need the heat too (-7 deg)...

    The halogen lamp version of the IR heating should be sufficient.

    Anyway, on a side topic, Electric motors are very efficient. But it is still only 90% efficient. The power electronic modules are only anywhere in the 85-95% efficiency rate.

    Even at 50KW, a 10% loss is about 5KW heater. Why don't any of the manufacturer using this wasted heat is beyond me.
     
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  5. Hey, I've been to Lake Tahoe... Now you made me miss it! Although I'm from Michigan, I moved to Michigan from the Bay Area in 2004, so I know the area...

    I don't claim to know much about the halogen lamp version of IR heating but there is a lot of useful research going on right now about wasted energy, especially utilizing wasted exhaust gas/heat.

    I think the movement to be more efficient is still relatively new. Some heat is used, of course, but this wasn't a big priority, any more than mileage as for most people years ago. It will be interesting to see where this all goes.
     
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  6. Lake Tahoe is indeed nice...

    In general, I think auto companies have been "leveraging" existing technology too much. I am curious on why Tesla didn't use the "waste" heat for its heating of the cabin...
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  7. "Anyway, on a side topic, Electric motors are very efficient. But it is still only 90% efficient. The power electronic modules are only anywhere in the 85-95% efficiency rate.

    Even at 50KW, a 10% loss is about 5KW heater. Why don't any of the manufacturer using this wasted heat is beyond me."

    Tesla uses the waste heat from the motor/inverter to keep the battery pack warm.
     
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  8. That is great, but there are still plenty of that heat left. Even the battery itself will generate a lot of heat during high load usage such as accerlation and highway cruising...

    I wish more Electric car makers can think outside the box sometimes...
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  9. BMW is really doing a great job finding new energy smart solutions. I'm lucky enough to live in a climate where I only have to use my heated seats in the dead of winter and I use the heater very very rarely. I do like the idea of being warmed without having dry warm air hitting me, so I would like to see this new innovation evolve into production vehicles.
     
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