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I have given this some thought.
Kers system with a flywheel and CVT would not be as efficient as a pure hydraulic IVT system.
2 or 4 wheel regeneration down to 0 speed is the key to the difference.
Since the CVT range is limited there is no way that system could totally replace the brake system on a vehicle.
The IVT hydraulic system could replace the brake system. It would need to have an emergency brake like all cars need today, but all the braking done by conventional brakes would be done by the accumulator and IVT.
In the case where the regeneration capacity was reached, braking would be down by restricting the flow of fluid between the high and low pressure sections of the pump without the accumulator involved when it was fully charged. Larger accumulators would be used in regions with significant elevation changes if the total accumulator capacity was found to be insufficient.
Either system Kers or hydraulic would easily exceed the regeneration energy return if done electrically.
Photos are attached showing flow charts from EPA and U of Michigan research comparing electric and hydraulic energy return percentages.
These are a few years old but show the significance of the differences in wheel to wheel energy recovery.
Another thing to consider about the Kers system compared to an in wheel IVT hydraulic drive is Kers still has to apply and recover power through other drive train components which would affect overall efficiency due to additional losses not existing in a pump to accumulator to pump energy pathway.
Every step of energy transfer and conversion has individual losses. The greater number of steps the cumulatively greater losses even when individual losses are small.
Example 4 steps at 90% per step, will produce less than 66% return of the original energy value.
Due to conversion steps and total energy losses it will probably never be possible to build an electric hybrid that can effectively utilize the P&G strategy
regards
Mech
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