"BMW is looking to electricity generated by exhaust gas heat and solar power to take the electrical load off the engine and thereby improve efficiency and reduce emissions.
In fact, BMW has found that reusing the otherwise wasted exhaust heat to power a thermoelectric generator could reduce fuel consumption by as much as 5%. The benefit comes from storing the electricity and using it to pre-heat the engine or power the air-conditioning systems. BMW is also working on employing solar panels on the roofs of its cars. Prototypes have achieved 200W output levels, enough to improve fuel efficiency by about 1%, and more advanced solar panel designs could easily improve on this figure. " http://www.motorauthority.com/blog/1024 ... technology
Unfortunately not everything green, is really green...
" Hailed as a miracle by Detroit automakers even today, catalytic converters have been reducing smog for 20 years. The converters break down compounds of nitrogen and oxygen from car exhaust that can combine with hydrocarbons, also from cars, and be cooked by sunlight into smog.
But researchers have suspected for years that the converters sometimes rearrange the nitrogen-oxygen compounds to form nitrous oxide, known as laughing gas. And nitrous oxide is a potent greenhouse gas, more than 300 times more potent than carbon dioxide, the most common of the gases, that is warming the atmosphere, according to experts. "