Fedex Ground is teaming up with hydraulic component manufacturer Parker Hannifin to develop and field test a hydraulic hybrid delivery van. The van will use a series hybrid layout similar to one developed by FEV that is being tested by UPS. The internal combustion engine will drive a hydraulic pump which will generate pressurized fluid to drive a hydraulic motor-pump. The second motor-pump will drive the rear axle. Under braking, the rear axle will drive the motor-pump to charge a high pressure hydraulic accumulator, capturing kinetic energy. During acceleration, the high pressure accumulator can provide driving force to the motor-pump to move the truck. The hydraulic hybrid setup has the advantage of being able to absorb energy more quickly than a battery, recapturing up to seventy percent of the kinetic energy compared to thirty percent for a typical battery. Unfortunately the capacity is limited. However it works well for this type of application that has a lot of stopping and starting and low speeds. The prototype is expected to be ready for testing by Fedex sometime in 2008.
[Source: Parker-Hannifin, via Green Car Congress]