For the 2008 M3 European model, BMW installed a regenerative braking system.  While the M3 certainly would not be considered a “green car” by today’s standards, it did implement this technology indicative of green cars.

From the 2008 BMW M3 press release:

Intelligent energy management featuring Brake Energy Regeneration likewise serves to further enhance the efficiency of the V8 power unit in the new BMW M3. In this case the power required for the on-board network is generated specifically during overrun and during application of the brakes, serving to charge the car’s battery at exactly the right time

without taking up any of the energy contained in the car’s fuel. As long as the engine is “pulling” the car, therefore, the alternator generally remains disengaged. Apart from particularly efficient generation of electric power, this also serves to provide more drive power and traction for supreme acceleration at all times.

So regenerative brakes are clearly a fuel-saving aspect to vehicles.  However, no BMW in the U.S. has featured the technology yet.  That may be about to change.  According to Autospies, they’ve seen this system on a U.S.-model 550i GT.  Seeing one of these brake-regeneration on a BMW 5 Series Chicago would be great.

The system controls when the alternator charges the battery, thus saving fuel.  Usually, an alternator constantly sends charge to a car’s battery, but in the 550i GT, the alternator charges the battery only when the car decelerates or brakes.  The rest of the time, it freewheels and draws no power from the engine, reducing fuel consumption.  In order to compensate for less charging time, the system uses a more powerful battery that uses technology which lessens the battery’s conversion of charging energy to heat, meaning more energy is reserved for a longer time in order to provide for the car’s electrical needs.  Below is an animated video depicting the regeneration system in action.

[youtube=http://www.youtube.com/watch?v=wF8CkwYxt_Y&hl=en&fs=1]

I’m hoping to see this technology in the BMW 5 Series Chicago dealer soon.  I’ve driven other cars with regeneration systems, but I’m happy luxury cars are implementing more eco-friendly technology, even if it is just a small component.