Hydraulic hybrids could be powerful alternative

The electric hybrid isn’t the only fuel efficient transportation option around. University of Minnesota researchers are working on a different approach — one that, unlike the Toyota Prius , lends itself to hot-rod style acceleration.

Hybrid hydraulic vehicles already have an advantage over electric hybrids in some applications, such as large vehicles that start and stop frequently, and mechanical engineering professor Kim Stelson ’s lab is working on developing hydraulic technology for small passenger cars.

Instead of using electricity stored in a battery, hydraulic hybrids store energy in the form of compressed gas.

Electric hybrids store energy more efficiently, but hydraulic hybrids are more powerful.

Hydraulic hybrids can use more braking energy than electric hybrids, which is one reason they’re ideal for vehicles like garbage trucks and delivery vans, which make frequent stops.

And Stelson wants to see the technology used in a Metro Transit bus. To that end, he said he’s working with the state to get funding to build such a vehicle.

Stelson said he’s hopeful that, if funded, the bus could get 10 miles per gallon, while traditional buses get about three.

Stelson said a preliminary estimate puts the cost of a prototype bus at $2 million. It would take about two years to build, he said.

Half the cost would be covered by industry donations, Sophia Ginis , outreach manager at the Humphrey Institute’s Center for Science, Technology and Public Policy , said.

State Sen. Ellen Anderson , who has toured Stelson’s lab, said she thinks it’s an exciting technology that offers “great promise for another kind of green technology for transportation.”

She said business is booming at a St. Cloud facility that produces hybrid electric buses, and Anderson expects demand for low-emission technologies will be “huge” in the coming decade.

Commercializing hydraulic hybrid technology in Minnesota, she said, could address energy problems and help the economy by providing green jobs.

As for possible state funding for a bus project, Anderson said she’s interested in supporting projects like this, but she noted this year’s state budget deficit will make it very difficult to get funding for anything.

Meanwhile, researchers have been periodically driving a test vehicle on campus since they finished rebuilding a donated Polaris off-road vehicle as a hydraulic hybrid in August.

They use the vehicle to test different components as researchers improve them, and to find out how different computer settings affect fuel efficiency, Justin Lapp , mechanical engineering graduate student, said.

They’re aiming to eventually get between 70 and 100 miles per gallon out of the vehicle, he added.

If researchers can improve the energy storage capacity and downsize bulky hydraulics, it could mean a fuel efficient passenger car with acceleration ability that would appeal to BMW , which has expressed interest in the technology.

Electric hybrid motors have comparatively lower power than hydraulic.

For this reason, Stelson said the Prius is a nice car, “but nobody is going to say it’s a hot rod. The hydraulic equivalent could be.”

Though the general technology used in the vehicle has been around for some time — Stelson said an early hydraulic hybrid was built at the University in the late 1970s — hydraulic hybrid vehicles are just coming on the market now in the U.S.

UPS has purchased seven hydraulic hybrids, and will roll out the first two in early 2009 in Minneapolis, Elizabeth Rasberry , UPS spokeswoman, said.

They expect a 40 to 45 percent improvement in fuel economy and a 30 percent reduction in carbon dioxide emission over a conventional diesel delivery vehicle, she added.

Still, companies in America aren’t as “interested as we’d like,” Lapp said.

He added politics sometimes become a problem, when companies feel like they have to choose either electric or hydraulic technology.

But, Stelson said, it’s not the case that one technology will win and the other will lose. Instead, both technologies should be developed, and each will work well for different applications.

“It is a competition,” he said, “but it’s not really competition to the death.”

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