Regenerative braking systems have become a common term in today's automotive communities. As we move to electric power, vehicles will need to make use of every available method to conserve energy to go farther on every charge. BMW has decided to take that idea to another level by using the wasted exhaust energy to produce electricity.
The Seebeck Effect
Together with NASA, BMW has been designing what will eventually be known as a regenerative exhaust system. By using the same technology that NASA uses on satellites, BMW is hoping to use the heat that radiates from you exhaust components to generate a small amount of electricity, which is estimated to be about 200 watts.
The force responsible is called the Seebeck effect. When two different metals are joined at two separate places and then a change in temperature is created, a voltage is generated along the places where the metals are joined. By putting one metal close to the exhaust components and the other farther away, the system would recapture lost heat energy.
Of course, 200 watts is hardly enough to run the entire vehicle off of, but BMW thinks it will be enough to power the auxiliary systems, such as the climate control, most of the time. They have also released an increase in efficiency of about 5%. Not the most impressive number, but it's still a start.