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Old 17th Apr 2011, 00:31
  #59 (permalink)  
Join Date: Jan 2003
Location: BC Canada
Posts: 413
I would think that if the present preoccupation with saving gas continues it is very likely we will see energy reservoirs in road cars before long. In Formula 1 the KERS systems have already shown it is very possible. They are good enough that, while it is only a very small portion of the energy put out by a Formula 1 car, they are limited by rule to 80hp.

That they would work to mitigate the energy required from the engine is obvious. If you slowed a car from, say 70mph to stop and put the energy into a reservoir and then accelerated to say 60mph before that energy was expended, (allowing for losses) you would only need to use the engine from 60mph back to 70mph and then a little power to maintain cruise. All the gas usually used from zero to 60mph would be saved.

Interesting as you would be doing with kinetic/potential/kinetic energy the opposite of what a zooming plane does with potential/kinetic/potential energy.

In the OP's question, given other things are equal, the gas saved is that not used by removing the foot from the accelerator in cruise a little earlier, not hugely significant but it does exist. Less energy put into the system saves the energy taken out by heating the brakes. (As the energy states of the car in the two examples, cruise and stopped, have to the same!)
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