Two UPS trucks have been equipped with a hydraulic hybrid system that is expected to produce as much as a 60 percent improvment in fuel economy.
In the early morning hours across America, five days a week, an army of garbage trucks set out to pick up the trash. They pull up, stop, idle, load and take off for the next stop, often only a 100 feet or less away. This happens 300 to 1,200 times per day, per vehicle.
On a good day, a diesel garbage hauler will eke out 4 to 5 mpg. Then there's all those icky, nasty pollutants pouring out of the exhaust pipe.
But thanks to the United States Environmental Protection Agency (EPA), yes, those government folks who monitor environmental laws and fuel mileage testing, a novel system called "hydraulic hybrid" is being tested in a Peterbilt garbage truck that increases the fuel economy an estimated 30 percent and reduces carbon dioxide emissions by 40 percent or more.
Developed at EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL) in Ann Arbor, Michigan, the Hydraulic Launch Assist (HLA) system essentially operates in the same manner as a gasoline-electric hybrid.
Like gas-electric versions, HLA works by recovering a portion of the energy normally lost as heat by the vehicle's brakes. But instead of a battery pack, a hydraulic system uses pistons to capture the wasted energy by compressing nitrogen gas stored in a tank. When the nitrogen is allowed to expand, it pushes a piston in a cylinder filled with hydraulic fluid that helps the diesel engine turn the rear wheels.
An aggressive variation of the HLA design is being tested in two UPS parcel delivery trucks. Using a series-type hybrid design, the V6 diesel engines do not power the vehicles, but serve solely to actuate the hydraulic systems' pumps. It's estimated that these vehicles could see fuel economy improvements of as much as 60 percent and a reduction of greenhouse emissions of 40 percent.
Using hydraulic technology to increase fuel economy and lower emission isn't an exclusive for the United States. Hydraulic hybrid buses are being tested on the streets of Beijing, China, with the hope of introducing them to other parts of the country.
The hydraulic hybrid appears to offer huge benefits when applied to heavy vehicles that operate in stop-and-go driving conditions, but what about passenger cars and trucks?
The engineers at the EPA's Michigan laboratory have built and tested many prototypes over the years, including a diesel-hydraulic passenger car that delivered more than 80 miles per gallon. In 2004 the EPA displayed a hydraulic hybrid Ford Expedition SUV with a small diesel engine replacing the large displacement gasoline V8. Ford was a partner with the EPA in developing the system, but later dropped out.
A rumor that's been floating around the Web for a couple of years is that Ford would introduce a hydraulic hybrid F-150 pickup in 2008 with an acclaimed 60 mpg. Bear in mind this is only a rumor, but stay tuned.
