Huh? A Hummer hybrid? Yes, the picture you see is of a Hummer H1 Hydraulic Hybrid. Hybra Drive Systems and Gates Corporation built this Hummer H1 with a fully hydraulic power train. Cheap? No. 100% Free. Trade stocks for free on Zecco.com. The Free Trading Community. www.zecco.com
So, what is an hydraulic hybrid and what should anybody think about them? Much like any other hybrid, there is an gas/diesel engine that is mated with another motor powered by some other source. Most passenger car hybrids are gasoline engines with battery-powered, electric motors, while hydraulic hybrids don't use batteries, but rather hydraulic accumulators to store energy. Hybrid batteries are store approximately 1.3 Kw/hr, while hydraulic accumulators "...have power densities of roughly 500 kW/kg, according to Jim O’Brien, founder and chief technology officer for Hybra Drive Systems, a start-up focusing on the development of hydraulic power trains." (found at DesignNews.com)
They work this way, from Design News:
Design concepts for hydraulic hybrids vary, but the car’s engine powers a hydraulic pump motor, which charges a high-pressure accumulator. The accumulator, in turn, drives one or more additional pump motors connected to the wheels. A second lower pressure accumulator completes the hydraulic circuit. Depending on the design, there may be one pump motor to drive a pair of wheels through a differential or one pump motor per wheel for an all-wheel-drive version with independent torque control. During braking, the pump motors on the wheels reverse themselves, re-charging the accumulator and capturing energy that would otherwise be lost to heat.OK, so why is this better than an electric hybrid and why isn't it available today? For one reason, it will be easier to dispose of hydraulic fluid than it is to recycle hybrid batteries. Secondly, because they are just so efficient over battery hybrids. Would you feel better if you had more energy? Try FRS® Healthy Energy™ Free*!
"Kargul (Technology Transfer Director at National Vehicle and Fuel Emissions Lab) says the gains came from three sources — running the engine at its sweet spot, operating the vehicle with the engine off and capturing braking energy. The regenerative braking capabilities of these systems... can far outshine the electric hybrids... made possible by the high power density of accumulators. Kargul says the EPA’s hydraulic hybrids typically capture at least 70 percent of the braking energy otherwise be lost to heat. He estimates electric hybrids capture more like 20 to 25 percent, because their batteries... have comparatively poor power density. “You would have to triple the size of the batteries to come close to 70 percent,” he says.
Although hydraulic hybrids are now being used in pilot programs on mainly commercial trucks, there are passenger cars being tested also. The current delay to mass acceptance is that the hydraulic pumps are big and expensive. Additionally, the most efficient system will have to do away with the typical, mechanical transmission.
While these challenges aren't insurmountable, they do allow for battery hybrids to rule the roost, so to speak. Fortunately, the free market is learning about this concept, and have begun to catch on. Parker Hannifin, Siemens and Eaton Corporation are the leaders in providing the hydraulic components, not to mention successful companies in their own right.