January 2008, Work Truck - Feature
How to Maximize Fuel Efficiency
By Joe Bohn
Switching to Alternative Fuels
Fleet operators have accelerated the switch into alt-fuel vehicles and new hybrid designs.
CenterPoint Energy didn’t have much success with compressed natural gas (CNG)-powered vehicles and is in the process of phasing them out. It has been looking at a hybrid bucket truck instead.
The CNG vehicles proved disappointing because there were not enough fueling stations. "It was taking too long for a refill and a lot of people went to gasoline," says Sparks.
But the City of Kansas City, Mo., which is "diversifying as much as we can away from petroleum — gasoline and diesel," according to Sam Swearngin, CAFM fleet superintendent, is a big proponent of CNG vehicles.
The city solved the fueling problem by setting up four natural gas fueling stations for its own use. A fifth station is currently being constructed, and a sixth is in the design stage.
Swearngin refers to CNG as the "Rodney Dangerfield" of alternative fuels because of its lack of media and public respect. "We’ve got more of it than any other alt-fuel. You can buy it and run it now, and it’s the cheapest and cleanest of all the fuels," he adds.
He notes, for example, that 97 percent of natural gas is sourced in North America, and its price is only $1.41 compared to a gasoline gallon equivalent.
Kansas City has been operating CNG-powered vehicles for the past 11 years. Its fleet includes 190 light-duty vehicles and 35 buses at Kansas City International Airport. It is also in the process of adding its first CNG-powered Class 8 trucks.
The 35 CNG-powered buses alone save $500,000 a year in fuel costs, according to a city study. Maintenance costs are "pretty much a wash" with those of a regular gasoline engine truck, Swearngin adds.
Government grants and CNG fuel credit tax write-offs help defray much of the fleet’s CNG operation.
According to Swearngin, his fleet had obtained more than $3 million in federal Congestion Mitigation Air Quality (CMAQ) grants to help pay for the CNG-powered trucks and fueling stations.
CMAQ grants are available in cities with air quality problems. They vary with the vehicle weight class, ranging from $4,000 for a light-duty vehicle, $20,000 for certain medium-duty classes, and $32,000 at the upper end.
Reducing an average hour of idling time a day can provide significant savings across an entire fleet.
Hybrids Grab Momentum
At a meeting of the Hybrid Truck Users’ Forum (HTUF) in September, 19 different models were displayed, covering a range of weight classes and applications.
The wide range, coupled with the introduction of medium-duty models, such as those from International Truck and Engine Corp., in Warrenville, Ill., and Freightliner LLC, in Portland, Ore., clearly illustrate hybrids’ growing momentum.
Both International and Freightliner use Eaton Corp.’s Cleveland hybrid-electric system (HES) in their medium-duty trucks.
Eaton’s system underwent seven years of development and was deployed in preproduction field units by fleets such as FedEx and UPS before going into regular production in 2006.
Eaton is primarily targeting the pickup and delivery (P&D) market and utility vehicle markets with its HES.
In the P&D market, the system provides a 30 to 50-percent improvement in fuel economy. In the utility market, it delivers a 40 to 60-percent reduction in fuel consumption, including the fuel that would otherwise be burned to support power generation at the job site.
The hybrid system uses a parallel, pre-transmission design. Primary components are the Hybrid Drive Unit (HDU), which combines a clutch, a motor/generator, and automatically controlled manual transmission; the motor inverter/controller; the DC/DC converter; and a 2 KWh ion battery pack.
The basic core of the system (HDU, inverter, and battery pack) is the same for both target markets. However, for utility applications, Eaton provides two additional features: auxiliary power generation and the ability to drive PTO (power take operations) with the electric motor.
Features of the system include:
- Electric motor vehicle launch and acceleration assist.
- Regenerative braking.
- Charge-sustaining battery system.
- For utility applications, on-board generation capability.
- Fallback to engine-only operation in case of hybrid system failure.
A clutch is the interface between the engine and the motor, which is directly connected to the input shaft of the transmission, according to Matthew Johnson, a member of the Eaton hybrid team, who explained the system at the SAE Hybrid Vehicle Technolo eaton.com gy Symposium 2007.
After startup, the clutch disengages and the truck is propelled by the motor. When the battery depletes to a specified state of charge, or when the power demand by the driver exceeds the specified limit, the hybrid control module engages the clutch and begins to blend engine power with motor power for operation. The blending is extremely precise, and clutch slippage is not an issue.
With the Eaton system, the engine is always on during driving operation. That’s due to the lack of electric accessories. The engine stays at low idle even in EV-drive mode to support the belt loads.
For the utility application, when the driver requests PTO, the engine switches off and the motor powers the tools and hydraulic lift. When the battery is depleted, the hybrid control module restarts the engine, closes the clutch, and recharges the battery.
Recharge time is about five minutes. Under constant operation, the battery will support 45 minutes of auxiliary power operation. Since most PTO applications are not constant, actual time between charging can take as long as two hours, according to a PG&E user of the hybrid.
Fuel savings in the utility truck vary with the type of mission, which Eaton reduces to two primary forms: more driving with less time on the job site and less driving with more time on the job site.
Separately, FedEx, headquartered in Memphis, Tenn., has begun preproduction testing of Azure Dynamics Corp.’s parallel hybrid-electric powertrain in Ford’s E-450 hybrid commercial delivery van.
Once the development phase is completed, FedEx has committed to purchase a minimum of 20 preproduction parallel hybrid-electric Ford E-450 delivery vans to be delivered by May, according to John Formisano, vice president, Global Vehicles, FedEx.
FedEx began introducing hybrid-electric vehicles (HEVs) into service in North America in 2004. It has 93 HEVs that have logged more than 1 million miles and has 75 more on order, including gas and diesel models, according to Victoria Mills, projects manager for Environmental Defense Corporate Partnerships program.
Among other activities, Environmental Defense, a Boston-based, nonprofit environmental group, has formed partnerships with companies such as FedEx to look for business-driven solutions to environmental problems. It began partnering with FedEx to develop commercially available hybrid trucks in 2000.
Similarly, United Parcel Service (UPS), Atlanta, runs 50 hybrid-electrical delivery trucks, along with 20,000 low-emissions and alternative-fuel vehicles operating in cities such as Atlanta, Dallas, and Houston.