On June 21, 2006 the Environmental Protection Agency unveiled the world's first hydraulic hybrid delivery truck in Washington D.C. The EPA hybrid features a hydraulic drivetrain that replaces a conventional drivetrain and eliminates the need for a conventional transmission. 
By achieving 70 percent better fuel efficiency in urban driving and 40 percent lower CO2 greenhouse gas emissions, this vehicle demonstrates the highest-efficiency powertrain known. A fleet owner operating one of these high efficiency hydraulic vehicles would save up to 1,000 gallons of fuel each year. EPA estimates that over the lifespan of the vehicle the net savings based on lowered fuel consumption and lowered brake maintenance cost to be over $50,000.
Ford is planning a similar system for their large trucks. See my previous post for more on ford's hydraulic hybrid and how this system works.http://www.yorkblog.com/archives/2006/06/the_f150_hydrau.html
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The technology Of The Hydraulic Hybrid has been out since 1920 but in 1975 it was presented to the EPA in 1975 by a man named Vincent Carman from Oregon. His story was presented in the article in "Mother Earth News" issue # 50 March/April 1978. The hydraulic storage energy is not new, it has just been brought forward now that we need a new energy source.
R. Linder
Harrisonville MO
Found an interesting description of how a hydraulic hybrid system works in the UPS truck
http://www.nashuatelegraph.com/apps/pbcs.dll/article?AID=/20060707/NEWS01/107070113/-1/neighbors
Hydraulics, which use the pressure of liquid squeezed through tubes to move things, have been part of cars from the beginning. They are best known in hydraulic brakes, in which the force of the driver’s foot on a pedal pushes liquid through tubes until it presses against brake pads.
The hydraulic hybrid uses pumps called accumulators to compress hydraulic fluid to 5,000 pounds per square inch – future models will go twice as high, said Gray – and move it where needed, such as the real drive pump motor, which converts the pressure into rotating power for the wheels.
Much of the benefit of the technology comes from the fact that it recovers energy used in braking and releases it for more power. The Prius does the same thing, but hydraulics do it more efficiently, Gray said.
Another major advantage is that the hydraulic hybrid is a so-called series hybrid, rather than the parallel hybrid design of the Prius. This means there is no mechanical connection between the engine and the drive wheels – basically, hydraulic fluid replaces the drive shaft – which allows much more efficient control of the motor.
Hydraulic hybrids are no panacea, of course. While hydraulics can store and release energy much more quickly than electric batteries – if a cell phone was powered by hydraulics, it could be recharged in just a few seconds – the total amount of energy they can store in a given volume is much less.
That’s why hydraulic hybrids can travel only a few hundred yards without the motor on, compared to many miles for a Prius.
There are also design questions about storing that much fluid in a vehicle smaller than a big truck.
For a big, heavy vehicle that makes lots of stops and starts and frequently idles, however, it could be ideal. So, while it may be a long time before a hydraulic hybrid car can be parked in your driveway, the technology might show up inside school buses or garbage trucks.
Why are there so many cell phones to choose from? Its really gotten just way to complicated. I did enjoy your perspective. Thanks!!!
Great post! And as always… I really liked reading through all the insightful comments. Thanks all!
Great job mate! Im a big tech geek... I like your work. Thanks for sharing.
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