A group of electric utility companies has ordered a batch of trucks with hybrid powertrains capable of running on-board equipment and generating power, while saving 40% to 60% on diesel fuel, according the Hybrid Truck Users Forum (HTUF), a movement of civilian and military executives and engineers intent on getting the special technology to market.
Progress with hybrid-drive refuse, beverage and package delivery trucks, as well as various types of military vehicles, was also reported at two HTUF meetings in recent months.
Savings on fuel and brake wear provide direct paybacks, and cutting exhaust emissions and noise are also benefits.
More than 50 large fleets representing a million trucks are participating in HTUF activities, said Bill Van Amburg, WestStart-Calstart’s senior vice president. WestStart-Calstart, based in Pasadena, Calif., operates HTUF in partnership with the U.S. Army’s National Automotive Center in Warren, Mich.
Trucks that continually stop and start are prime candidates for hybrid application because braking energy can be captured and reused as “launch” power. But trucks that stand still much of the time can also benefit.
Thirteen utility fleets will take 20 diesel-electric trucks later this year and put them into regular service to test their performance, reliability and operating costs, said George Survant of Florida Power & Light, who heads the utility fleets’ effort. International Truck & Engine will assemble the model 4300 Class 7 trucks in its plant in Springfield, Ohio, using a 225-hp DT466 diesel, Eaton UltraShift transmission and an electronically controlled hybrid system built by Eaton Corp.’s Electric Group.
Eaton’s electric hybrid system includes an automatic clutch, a motor-generator, a bank of batteries, an inverter and power panel, and an electronic control module. The engine-spun motor-generator charges the batteries or – taking electricity from batteries – powers the truck through its driveline. The automated mechanical transmission sends power from the motor-generator or the diesel engine to the rear wheels.
Tests of a prototype showed the utility “trouble truck” can work at a line repair site with its diesel engine off much of the time. The hydraulic boom with its man bucket can operate with the engine off or on because the motor-generator – not a transmission-mounted PTO – runs the hydraulic pump.
An engine-driven generator charges batteries, which supply about 3 kilowatts of energy to the pump and other accessories. The generator can also produce up to 20 kW of electricity for work tools and lights, or to power a building temporarily deprived of grid power.
Part-time engine use not only saves fuel but also cuts on-site noise and fumes, keeping peace with the neighbors. Cutting engine use should also extend the engine’s life and reduce maintenance intervals by 20% to 30%, Survant said.
The hybrid trucks are “transparent” to drivers, meaning they’ll operate the vehicles the same as regular diesel-powered trouble trucks, Survant said. Hybrids are expected to perform as well or better than a regular truck on the road at speeds up to 65 mph, and to deliver equal to or better reliability. Exhaust emissions levels should be within federal limits set for 2010.
A complete Class 7 trouble truck usually costs $160,000 to $170,000; a hybrid version adds 30%, or close to $50,000. That premium should come down when these trucks are built in volume. Regular commercial production should begin in 2006, International executives said.
Participating utility fleets make up a “utility users group” within HTUF, and it’s that group that is coordinating fleet orders for the diesel-electric hybrid trucks. International and Eaton, who won the contract over bids from other suppliers, have also built a beverage delivery truck for Coca-Cola using a similar hybrid powertrain. Regenerative braking is a bigger factor in such a truck.
Electric hybrid programs
Eaton is also involved in electric hybrid programs for FedEx Express and United Parcel Service. The FedEx walk-in vans were built by Freightliner Custom Chassis using a 170-hp Mercedes-Benz four-cylinder diesel with Eaton electrical and electronic components. The system uses four lithium-ion batteries and operates at 340 volts.
FedEx Express is running a group of pre-production “e700” vans (for electric, 700 cubic feet of cargo capacity) in everyday service and comparing their performance to that of regular diesel-powered W700 vans. Sid Gooch, a FedEx maintenance executive who manages this project, reported substantial reductions in emissions and fuel consumption thus far.
The United Parcel Service project uses an International 1000-series chassis with the builder’s VT365 6-liter V-8 diesel. The Eaton electric hybrid system – including a motor-generator and an UltraShift transmission – is similar to those used on the FedEx and utility trouble trucks. This $7.7 million project includes a $3.8 million grant from the federal Department of Energy. Eaton and International together are investing $3.9 million, according to Scott Davis of Eaton.
Hydraulic hybrids are also advancing. Peterbilt Motors has built a diesel-hydraulic refuse truck using Eaton’s Hydraulic Launch Assist (HLA) system, said Steve Nash of Eaton’s Fluid Power Group.
The 65,000-pound-GVW model 320 chassis uses a 315-hp Caterpillar C-10 running through an Allison 4000 automatic transmission. Four hydraulic accumulators store fluid that’s pressurized by a driveline-mounted pump as the driver applies the brakes. When the driver steps on the accelerator, the high-pressure fluid moves back to the pump, turning it into a motor to help launch the truck.
The engine always runs to power accessories like the air and power steering pumps, but spends more time at slow or fast idle than in a conventional trash-collection truck. The engine also continues to propel the truck after the hydraulic energy is expended, which happens in 10 to 15 seconds in normal launches. The engine would also run the trash-compaction apparatus in the packer body. The body now on the chassis is a dummy weighted with concrete blocks, said Peterbilt engineers Glen Marshall and Bill Kahn.
Testing shows that the launch assist saves 17% to 27% in fuel – depending on whether the controls are set for performance or economy – while regenerative braking cuts brake wear by 51%. Marshall and Kahn said those savings would pay back the extra cost of the Hydraulic Launch Assist in two to three years and probably sooner, because an Eaton HLA produced in some volume would cost far less than an electric hybrid system.
A hydraulic hybrid system designed by Permo-Drive of Australia is being fitted to a half-dozen of the U.S. Army’s medium-duty cargo trucks, said Paul Chandler, vice president of the company’s U.S. operation, which has partnered with Dana Corp. on the project. Like Eaton’s HLA, Permo-Drive’s RDS (for regenerative drive system) is pressurized during braking by a driveline-mounted motor-pump, which helps launch the truck as fluid is sent back to it.
Nitrogen gas for safety
The Eaton and Permo-Drive systems both use nitrogen gas for operation and safety. Hydraulic fluid in tank-like accumulators is enveloped in bladders filled with nitrogen. The compressed nitrogen aids in pressuring the fluid to as high as 5,000 pounds per square inch, and acts as a spring by pushing the fluid toward the driveline motor during launch.
Nitrogen also acts as a safety jacket should a tank be punctured, Chandler explained. But in a breach, gas rather than hot high-pressure fluid would be released, quickly lowering pressure and rendering the system harmless to anyone around. Unless it were disabled by a crash or other damage, the truck could continue to operate on conventional diesel power alone.
Six of the Army’s 2.5- and 5-ton trucks are being fitted with dual-accumulator systems for tests beginning in April, Chandler said. The so-called FMTVs, for Family of Medium Tactical Vehicles, are cab-over-engine chassis built by Stewart & Stevenson with Caterpillar 7.2-liter diesels and Allison automatics. Other Army programs involve other types of military cargo and utility trucks whose sizes and weights are similar to commercial trucks.
Fuel costs $40 to $400 per gallon to ship and deliver to trucks and fighting vehicles in areas like Iraq and Afghanistan, Army officers have said. Donald Szkubiel, manager of the FMTV program, said the eventual goal is to cut fuel use by 75% through the use of hydraulic and electric hybrids. He and his colleagues are sharing what they’re learning about hybrids through HTUF because wide adoption of hybrid technology by civilian users will lower its cost for everyone.
While enthusiasm for hybrid trucks shown by HTUF participants is high, it has not been matched by most members of the Technology & Maintenance Council of the American Trucking Assns.
TMC has set up a task force on hybrid trucks, but the membership in general hasn’t shown much interest, said Guy Rini of Mack Trucks, chairman of the task force.
That might be because most members run over-the-road tractor-trailers, which spend long hours cruising and comparatively little time stopping and starting. And, at least for today, starting and stopping is where the hybrid systems shine.
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