Sorry if this has been discussed before, I'm not a regular of the site and I have not found anything in a first quick search, if so just direct me to the relevant threads. Many millions of cars are driving every day with their alternators turning. Unless I'm wrong, once the battery is fully charged the alternator keeps turning but any electricity produced is simply wasted. If this is correct, I can guess that considering all the internal combustion engine vehicles driving around each day in the whole world, the amount of wasted energy may be very significant. Has there been any calculation of how much energy is being produced but wasted by this fact? Is there any project by which that wasted energy could be harnessed and used? Thanks!