Brown Going Green

United Parcel Service, with 91,000 of its well-known brown package-delivery trucks operating every day worldwide, could derive huge fuel savings from a new fleet of advanced hydraulic hybrid trucks it has started testing in certain regions.

Fuel savings could be in the 60% to 70% range on stop-and-go urban routes.

UPS is testing an International Truck and Engine Corp.-built delivery truck powered by a 6L V-8 turbodiesel — but without a conventional transmission and propshaft to drive the wheels.

Instead, the truck is equipped with a hydraulic hybrid vehicle (HHV) system patented by the U.S. Environmental Protection Agency and developed in a partnership that includes UPS, Eaton Corp., International and the U.S. Army National Automotive Center.

The hydraulic hybrid includes four major components: A high-pressure accumulator that stores energy using hydraulic fluid to compress nitrogen gas; a pump motor that uses pressure from the hydraulic fluid to provide rotating power to the rear wheels; a low-pressure reservoir that stores the fluid after it has been used by the pump motor; and an engine-driven pump motor that pressurizes and transfers hydraulic fluid either to the rear pump motor or high-pressure accumulator.

Most of the HHV's efficiency is derived in stop-and-go driving. As the vehicle slows or stops, the rear-wheel pump motor uses that braking force to pressurize the hydraulic fluid in the accumulator. When the truck accelerates again, the pressurized nitrogen gas acts on the fluid, via the pump motor, to turn the wheels.

The UPS demonstration vehicle boasts a 40% reduction in carbon dioxide (greenhouse) emissions. Also, regenerative braking recovers and reuses 70% of the energy wasted during stopping, reducing brake wear. An engine shutoff system turns off the engine when it's not needed.

So far, only one UPS HHV has been built. It is being tested in everyday operation in Cleveland (where Eaton has its headquarters) and, soon, in the Detroit area.

When HHVs will move into series production is not yet known. “What's needed now is production technology, and that's where Eaton excels,” says Christopher Grundler, deputy office director in the EPA's Office of Transportation and Air Quality, based in Ann Arbor, MI.

Grundler says the HHV technology has captured interest from short-haul trucking operators such as refuse haulers and also the U.S. Postal Service and the Department of Defense.

“Current trends in transportation are not sustainable,” he says. “We've got to find new ways to transport people and products.”

Based on EPA estimates, an HHV truck such as the latest demonstrator could save 1,000 gallons (3,785 L) of fuel annually and $50,000 over a 20-year vehicle lifespan, based on current fuel prices.

Although HHV might add 15% to the base vehicle price, says the EPA, it could pay for itself in two to three years in fuel and maintenance savings.

Frank Whalley, vice president of UPS' North Ohio District, says UPS already has 1,500 alternative-fuel trucks in operation with 100 million miles (162 million km) accumulated.

Whalley says results of the UPS HHV tests, which began in June, “have been very positive so far. We see a lot of opportunities. We think it works best in non-freeway, urban areas where you get the most benefits at low speeds.”

Craig Arnold, Eaton senior vice president-Fluid Power Group, says the HHV setup “is based on proven technology; no invention has been required.” Eaton has worked with the EPA on the development since 2001, co-locating its team with the EPA in Ann Arbor, he adds.

Alexander M. (Sandy) Cutler, Eaton chairman and CEO, says HHVs “still need another two years of testing.”

Asked when the development might reach major application, he replies: “That will depend upon the UPS and FedEx” and others.

Eaton's Fluid Power segment, with $3.2 billion in annual sales, is the company's lead group in HHV development.