That depends on the journey: <Most of the energy a car uses, is in the acceleration to speed>. On a trip to another city, the acceleration energy is trivial = get up to 100 kph then sit with the engine racing along at 4000 rpm until getting there when wind resistance and rolling resistance is sufficient to stop the car in a few hundred metres. I could do trips like that without having brakes at all. Even around town, brakes aren't really necessary with a manual gearbox.
In the good old days, my challenge was to drive my 1951 Hillman without starter motor, brakes, or clutch other than to get going = park on a downward slope to get moving and clutch start the motor, then double-declutch for gear changes [matching engine speed to the next gear], using the engine to slow and stop.
Even around town, rolling friction, drag and idling are the greatest part of energy and the amount which can be recovered is small, though as you say, it might as well be collected since it's cheap to collect it and the braking energy has to be dumped somewhere.
I was surprised and disappointed when I worked out how little energy would be collected from braking and put back into acceleration.
Mqurice |
