Can hydraulic systems fuel the next generation of hybrid cars?

New electric hybrid minivans may come with a hydraulic system that does away with batteries altogether.
Written by Tuan Nguyen, Contributing Editor on

It's a little known fact that when it comes to fuel efficiency, some garbage trucks can put hybrid cars to shame -- thanks to a hydraulic hybrid system that does away with batteries altogether.

Now, Chrysler Group has partnered with the U.S. Environmental Protection Agency to adapt the same technology for minivans. They have invested $2 million dollars each to make it happen, with road testing planned for as early as next year.

The system offers considerable key advantages over battery-operated electric hybrids, as Technology Review magazine points out:

Hydraulic systems are bulky and loud, which has limited their use to large vehicles such as garbage trucks. But they're attractive because pumps and air storage tanks are cheap compared to batteries. Also, hydraulic hybrids have the potential for larger fuel economy improvements than battery hybrids because hydraulic systems can store energy very quickly, allowing them to capture more energy from braking.  While conventional battery hybrid systems for minivans might improve fuel economy by 25 percent compared to gas-powered cars, hydraulic systems could improve fuel economy by 30 percent to 35 percent under most conditions, says David Haugen, manager of the technology development group at EPA's National Vehicle and Fuel Emissions Laboratory. In city driving, the improvement could be as much as 60 percent. Chris Cowland, Chrysler's director responsible for advanced powertrains, says the 60 percent improvement is "way more significant than any other technology that we know of today."

Hydraulic systems are similar to conventional hybrid electric vehicles in that they improve fuel economy by harnessing the energy generated each time a driver slams on the brakes, a process known as regenerative braking. But instead of using the energy to recharge an onboard battery, it's used to move fluids from a reservoir into the accumulator. As the fluid is pumped into the chamber, pressure builds up and becomes a form of compressed energy that can be tapped into to help power the motor.

UPS recently integrated the technology into a fleet of delivery trucks, which improved fuel economy by 50 to 70 percent compared to their gas-powered delivery models. INGOCAR, another concept car powered by a hydraulic hybrid system, can reportedly stretch efficiency to about 170 MPG.

But adapting hydraulic systems for commuter cars will undoubtedly be a hefty challenge. The vehicles don't have nearly as much space to accommodate the kinds of massive air storage tanks found in larger vehicles. And since cars are often driven on city streets and freeways, they also don't experience stop-and-go traffic to the same degree as delivery and garbage trucks. So engineers will also need to figure out a way to supply power to headlights, windshield wipers and other electrical systems without relying on a battery.

The bottom line is that although saving on fuel costs and reducing carbon footprints will always remain strong selling points, it's unlikely very many people would want to drive a minivan without a car radio -- no matter how fuel efficient.

Photo: National Science Foundation

This post was originally published on Smartplanet.com


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