I just registered so I could add some information to this thread.
Hydraulic hybrids are a real alternative to other hybrid configurations.
Many different groups are working on HH designs for cars as we view this thread
http://www.innas.com/Assets/files/Hydrid%20brochure.pdf
This is one of the best efforts to date but there are others that are significant. The HH option provides two separate efficiency increases that will make HH vehicles a potential solution to future transportation.
1. High capacity regeneration efficiency.
Currently wheel to wheel is 78%. Compare that to electric regeneration at less than 50%. Future designs have the promise to equal the power train efficiency of a conventional power train. One of those design is my own. It should see the patent process completed in a few months.
2. Constant vehicle speed Pulse&Glide.
With high capacity storage via accumulators or flywheels, you can use the P&G tactic without variable speed. An Infinitely Variable drive with short term high capacity storage allows this to be possible while vehicle speed remains constant. This will not be possible with electric propulsion, due to the various steps and the cumulative effects of the separate losses through each step.
Most here recognize the effectiveness of the P&G strategy. Think of the potential of P&G without the necessity of using the mass of the vehicle as your short term storage.
Weight:
Charles Gray head of the EPA program said. " I can hold a 500 HP hydraulic motor in my hand."
Accumulator storage capacities are in the neighborhood of 50 KW per kilogram of weight. Much higher capacities are possible with exotic materials.
Hydraulic launch assist can be added to existing FWD vehicles for a weight penalty that is neutral when you consider the reduction in fuel tank capacity and removal of other components that would no longer be necessary. In fact if you build a dedicated HH vehicle you could eliminate close to 24% of the existing parts in the most basic car and build a HH car for less than the cheapest car you can buy today.
regards
Mech