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Old 01-20-2011, 02:40 PM   #5 (permalink)
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500 KW seconds versus 300 W hours.
3600 seconds per hour.

Batteries can only accept energy at a fractional rate of what they can discharge energy.

How much do you need and how long do you need to store, energy wise.

Hydraulics can recover energy at the limit of the tires adhesion, and reapply the energy at the same rate.

Lets assume you have an 80% efficient hydraulic recovery system. The last I heard was 78% (2006). That's wheel to wheel in regenerative braking. Now lets think about the drive as being in the 80-82 % efficiency range. Not what a manual transmission would be efficiency wise, but with capabilities no manual can duplicate.

An accumulator allows you to limit engine operation to only best bsfc, no matter what the acceleration or regenerative state of the vehicle.

Every technique the hypermiler utilizes can be incorporated into the vehicle itself. No matter how fast you stop or start off from a light, the energy used for acceleration is basically the same.

The hydraulic system would allow acceleration to be accomplished with no fuel consumed. The engine and engine driven pump are either on, charging the accumulator or off when accumulator storage is at designed maximum.

Vastly more fuel is used in initial acceleration, and vast amounts of fuel are wasted in braking. This is exactly where the hydraulic system would allow no fuel to be used.
We hypermilers understand that and try to avoid both situations with significant results.

A purposely designed hydraulic hybrid does it itself, a self hypermiling car.

This is what most people do not understand. The hydraulic hybrid is capable of pulse and glide, while maintaining a constant speed. The new Hundai Sonata Hybrid does this same thing cycling between engine and battery power at cruising speeds. It accomplishes this by using the higher load of an engine driving the vehicle and charging the lithium battery. Then the engine shuts off and speed is maintained by the electric motor and battery for about 40 seconds at 60 MPH.

That is exactly what the hydraulic hybrid can do, and it has been proven in the Artemis design as well as the INNAS design. Automatic constant speed engine off P&G, without the speed variations necessary with a typical manual transmission vehicle. While the hydraulic drives may not be quite as efficient as a manual transmission, the difference could be so close that the constant speed versus the high peak speed in the pulse phase is a wash since total aero drag is lower at average speeds versus variable speeds when using pulse and glide, to say nothing about the effect of speed variations on other drivers around you.

In wheel drives eliminate the rest of the typical power train components, which would easily cover the weight of the accumulator. The mileage increase in both the INNAS and Artemis systems is 100 % combined cycle.

You can argue that the increase is not that great at higher speeds, but that holds true for any hybrid system. Sustained high speeds allow high bsfc levels with proper gearing in conventional vehicles with the Civic VX as an excellent example.

Better aero, rolling resistance, and light weight all contribute to better mileage. In the future hydraulic hybrid those improvements automatically mean better mileage.

regards
Mech
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