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Originally Posted by curtis73
In a hybrid vehicle, there are two state changes. The energy from the fuel is converted to electricity, then the electricity converted to motion. Each time it changes, it loses energy.
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I agree with all the comments in this thread. However, I think the above comment does not apply to the Honda systems. To the best of my knowledge, by far the principle source for electricity in the Honda hybrid is regenerative braking, and such times when the engine has excess kinetic energy which is being wasted, such as when slowing down or backing off the revs. All other times, the engine does not spin the generator, because, as curtis suggests, the engines power is much more efficinetly used in actually moving the car down the road.
I would agree that the notion of using a gas engine to spin a generator becuase the gas engine is too feeble on its own (Prius) is inefficient.
These hybrids usually get better fuel mileage in the city than on the highway, because a substantial amount of the braking energy is reclaimed, in the city, but the aerodynamic losses from highway driving cannot be reclaimed.
I think this is an interesting indicator of how inefficient city driving is for the traditional car.
Also curtis quite correctly discusses the energy loss in using kinetic energy (the spinning crankshaft) to create electricity.
To the best of my knowledge, this is called induction loss. About 75% of the kinetic energy is lost due to induction, that is, a hybrid can only reclaim about 25% of the braking energy, store it and deliver it through an electric motor.
Now, there are other ways of storing kinetic energy, over the short term, that are more efficient. GM has considered using compressed gas and fluid to store and re-deliver the energy. Their systems and more efficient than a hybrid and can be adapted to older vehicles and to existing designs. They tend to be a bit bulky so are most useful on trucks.
Finally, different layouts of hybrid technology can provide other benefits than just better economy.
I believe there is a hybrid of the Lexus RX 300 suv (Car&Driver) where the electric motors/generators work on the rear wheels only, combined with a standard FWD gas engine. In this case the electric motors provide a full 4wd capability and faster acceleration (when charged) that a standard RX330, without actually consuming more fuel.