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Braking for energy recovery

After 100 years or so of automotive braking that simply turnspotential energy into wasted “heat,” via friction-based systems, we’restarting to move to more intelligent systems, that re-capture someenergy. 

When I was a kid I loved watching the Flintstones. But I didn’t like the Flintstone-mobile. Fred “braked” by sticking out his legs out through the floorboards and scrubbing off speed with his bare feet. This always made me cringe.


And I still cringe whenever I relive my own Flintstone moment. On this occasion my Jaguar E-type suddenly and silently found itself coasting down the mild slope of our driveway, with me standing beside it.


I grabbed the front bumper and stood my ground, but the car pushed me slowly backwards. We stopped together in the middle of the street, unscathed, save for the leather soles of my moccasins, which were smoking. I can still feel the feet heat.


Which brings me to the point of this column — after 100 years or so of automotive braking that simply turns potential energy into wasted “heat,” via friction-based systems, we’re starting to move to more intelligent systems, that re-capture some energy.


This has come about due to the re-birth of the electric vehicle. If you have an electric motor hooked up to the drive wheels, you can use it to “brake” the vehicle, by simply reversing the flow of power.


Now, instead of having the motor turning the drive wheels, you have the drive wheels turning the electric motor. The resistance works like a brake, and when you spin an electric motor it makes electricity.


In a hybrid or EV this “free” juice is fed to the big battery pack, which powers the electric drive motor. But now we’re seeing this concept being applied to “conventional” vehicles.


BMW introduced its Brake Energy Regeneration system on the 2010 5 Series Gran Turismo. The new-generation 2011 X3 will also feature the system. At the upcoming Paris Motor Show, Ferrari, of all people, is expected to debut a similar “brake re-gen” system on its updated California model.

 
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