Record fuel prices and a greening of the trucking industry’s collective consciousness are pushing hybrid commercial vehicles closer to the mainstream.
In a period where truck sales are down across the board, hybrid orders of unprecedented volumes are making headlines. In February, Coca-Cola placed what Eaton dubbed its largest ever single order of hybrid commercial vehicles – 120 trucks of various makes equipped with Eaton’s hybrid-electric drive system. UPS raised the ante in May with an order of 200 hybrid-electric delivery vehicles, also equipped with the Eaton system.
It’s not surprising that hybrid vehicles are receiving a lot of attention. In the right application, trucks equipped with a hybrid-electric drive system are proving their worth in the real world. Eaton touts its hybrid-electric system can offer fuel savings of 30% or more in stop-and-go, medium-duty applications. For utility fleets and other applications that can run an auxiliary device off the electric motor, that savings can be augmented with an 87% reduction in idle-time at job sites, according to David Bryant, vocational sales manager, hybrids with Freightliner. Top it off with maintenance savings, including a two-fold increase in brake life, and it’s little wonder that interest in hybrids is increasing. However, while federal government incentives of up to US$12,000 per vehicle have accelerated the uptake in the US, the adoption rate here in Canada lags in the absence of any such rebates. The Achilles heel of the hybrid truck world remains price; OEMs at the Work Truck Show in Atlanta earlier this year indicated the Eaton hybrid-electric system adds about US$40,000-$45,000 to the cost of a chassis, and you can add another US$15,000 if you require an electric-PTO.
“Cost is not a show stopper, they’re still ordering our trucks,” said Judy McTigue, medium-duty marketing manager with Kenworth at the show.
Chris Wehrwein, senior design engineer with Peterbilt, said a payback is still possible even without government incentives -in the right application. With that in mind, here’s a look at which applications are best suited for hybrid vehicles as well as the types of hybrid systems that are proving to be the most popular.
Most of the hybrid trucks sold today are equipped with Eaton’s hybrid-electric drive system. The system pairs a traditional diesel engine with an electric motor and an automated transmission. Energy normally lost during braking is captured and stored in a battery pack, through a process called ‘regenerative braking.’ That energy is then used to help propel the vehicle-via the electric motor -during acceleration.
It’s a parallel system, meaning the truck can be operated solely on the diesel engine if the electric motor or other hybrid components should fail. Because the system produces its power through regenerative braking, the hybrid-electric drive option is most effective in stop-and- go applications. Since the electric motor can be used to power auxiliary equipment, such as an aerial lift, the best results have been realized in utility and other specialty applications. The system has the added benefit of operating such devices soundlessly, which has made it especially popular in urban environments. When the batteries become depleted, the truck’s diesel engine starts up automatically and recharges the batteries without interrupting worker productivity.
It takes about four minutes to recharge the batteries, according to Jeff Mudget, senior technical engineer with Eaton.
I’ve had the opportunity to drive several trucks equipped with Eaton’s hybrid-electric system, namely: a Freightliner M2e beverage truck, an International 4300 utility truck, and a Peterbilt 335 utility truck. There are subtle differences in how the system is integrated into each of the vehicles, but they all drive pretty much the same.
Immediately noticeable is the instantaneous torque provided by the electric motor. Think of it as a light switch: when the switch is turned on, you get light instantly. Similarly, when you press the accelerator, you get instant power and torque out of the little electric motor.
This instantaneous responsiveness can improve driver productivity, especially when frequent starts and stops are necessary. Trucks equipped with the Eaton hybrid-electric system drive much like any other vehicle, until you let off the throttle, that is. Releasing the gas is like throwing a giant parachute behind the truck, as the electric motor slows the vehicle to a near standstill.
I only had to step on the brake to bring the truck to a complete stop, which lends credence to claims of dramatically extended brake life.
The diesel engine idles at low speeds and lets the more efficient electric motor do the work. The transition between electric motor and the diesel engine is smooth and seamless, and it takes very little time to get used to driving the vehicle.
While hybrid-electric vehicles receive most of the attention due to their more widespread use than other electric alternatives, there are also commercial vehicles in use that run exclusively on electricity.
Purolator Courier’s Quicksider is among the most famous of these vehicles, and is regularly showcased at industry events.
Purolator is a pioneer of sorts when it comes to adopting hybrid vehicles here in Canada. Its fully-electric Quicksider incorporates a Unicell body and ArvinMeritor drivetrain components.
“Our hybrid-electric vehicles are 37%- 40% more fuel efficient (than traditional delivery trucks), but they use the same body type as our gas-powered vans,” Serge Viola, national fleet manager with Purolator said in a white paper published by ArvinMeritor. “They do nothing to improve ergonomics, maintenance or cargo capacity.”
The Quicksider has an operating range of about 65 km between charges, making it ideal for low-mileage, high-density routes, complimenting the company’s fleet of hybrid-electric trucks which will continue to be used in extended routes.
The Quicksider does not require traditional drivetrain components, allowing the body to be lowered closer to the ground, which makes loading and unloading easier for the driver.
“Because the (electric) motors are at each wheel, there is no driveline, transmission or rear axle differential,” explained Dennis Kramer, hybrid program manager for ArvinMeritor. Of course, a fully-electric delivery vehicle also produces even fewer emissions than a hybrid-electric alternative -none, to be exact.
While the Quicksider has proven to be effective in the real world, Viola pointed out, “You still have to pay for the battery and for the electricity to charge it at night.” ArvinMeritor’s Kramer adds that “further returns will come from improvements in hybrid vehicle technology -high-voltage, high-output motors, improved battery chemistries and solid state controls.”
In applications where an electronic-PTO is not required, hydraulic hybrids may be the answer. Eaton’s hydraulic launch assist (HLA) system was on display in a Peterbilt 320 refuse truck in Canada for the first time this summer at the City of Toronto’s Green Fleet Expo.
While it has not yet been made available for a test drive, it reportedly performs much the same way as the hybrid- electric vehicles. Hydraulic hybrids also use regenerative braking to produce energy which is used in tandem with the diesel engine to power the truck during acceleration. However, instead of using costly batteries with a finite life span and an electric motor, it utilizes hydraulic components, such as a: transfer case, accumulator, hybrid control unit, pump/ motor, and reservoir.
“As it’s slowing down, the pump is engaged,” explained Vincent Duray, chief engineer, hydraulic hybrids with Eaton. “It’s pressurizing the accumulator and through that increasing pressure you’re actually slowing the vehicle down. When you step back on the gas, that energy is re-applied back to the drivetrain.”
Eaton claims its HLA system is proving to reduce fuel consumption by 20%-30% in refuse applications, which seems to be the best fit for the system at this time. It also provides better power transfer at starts, Duray said, allowing trash collectors to pick up more bins per shift.
In refuse applications, Duray said a payback period of three to five years is expected, even without government incentives. Duray admitted hydraulic hybrids are not the best answer for every application.
“We are going to let the application decide which is best for that particular service and application so we don’t have to force one solution that may not be the best,” he said. “Our viewpoint is, let the market decide (which technology is best).”
Eaton’s HLA system is available in two modes: Performance and Economy. Performance mode is intended for applications where the vehicle can take advantage of the extra power during frequent starts. In this mode, acceleration is improved by 25%, Duray said. In Economy mode, engine torque is limited to provide even greater fuel savings. This is best for smaller trucks or those working in tight spaces with fewer starts and stops.
Eaton’s HLA system is designed to last 10 years -the typical life-cycle of a refuse truck.
With medium-duty hybrid trucks edging towards the mainstream, designers of hybrid components have turned their attention to bigger things -such as Class 8 hybrids. Kenworth has already started work on a heavy-duty hybrid built upon the T660 platform. Kenworth’s McTigue said the company hopes to achieve fuel savings of 10-15% in long-haul applications. However, not everyone is as optimistic about the potential of hybrids in heavy-duty long-haul service.
“It’s not that there is no fuel efficiency to gain in heavy-duty applications, but if you look at the overall business case for the customer, you make them pay quite a bit up front which they will recuperate very quickly in a medium-duty, stop-and-go application,” Christoph Hofmann, director of product strategy with Freightliner told Motortruck Fleet Executive in an exclusive interview this spring. “But in heavy-duty long-haul applications where you rarely stop, there’s not a whole lot of recuperation of energy and the fuel economy gains are much lower and usually the payback is not there to justify the up-front cost. So for the time being, we’re somewhat cautious on that front.”
Those challenges were also acknowledged during a hearing held before the US House of Representatives’ Science and Technology Energy and Environment Subcommittee in June.
“While several truck companies are testing hybrid models, significant technical hurdles remain, and there is no one-size-fits-all hybrid solution for the entire sector,” the committee admitted in a report. “Long-haul tractor-trailer rigs (Class 8) may prove even more challenging (than medium-duty trucks) since they seldom brake during a drive cycle, providing little opportunities for battery systems to recharge.”
However, that hasn’t deterred several truck makers and component suppliers from forging ahead with heavy-duty hybrids. Volvo Group has been active on this front, and claims the heavy-duty hybrid system it is developing in partnership with the US Air Force will deliver 5-8% fuel savings in long-haul applications. Its proprietary system uses an electric turbo-compound to generate electricity which can be used to power devices such as pumps, fans, air compressors and even power steering and air conditioning, says Anthony Greszler, vice-president of advanced engineering with Volvo Powertrain North America. This takes strain off the diesel engine, improving fuel economy.
“This is not just something we’re pushing on the marketplace, there’s definitely more pulling than pushing,” former Mack president and CEO Paul Vikner said at an alternative fuel conference in Washington this spring.
Also aggressively pursuing heavy-duty long-haul hybrid development has been ArvinMeritor.
“Technologies that were deemed too expensive when fuel was $1.20/gallon now have greater appeal to highway fleets that are grappling with volatile energy costs and increasingly stringent emissions regulations,” Tammy Packard, manager, product strategy commercial vehicle systems with ArvinMeritor wrote in a white paper on the subject.
ArvinMeritor, along with Cummins and International Truck and Engine, has developed a long-haul heavy-duty hybrid system for Wal-Mart. The hybrid-electric system is designed to save fuel in three ways: by using the electric motor to power the vehicle whenever possible, producing zero emissions in the process; by eliminating engine idling; and by electrifying the power steering, air compressors and other components that are traditionally belt-driven.
Wal-Mart is hopeful that hybrid-electric drivetrains will be 50% more efficient than current linehaul vehicles, according to Packard’s white paper. The company also hopes to enjoy reduced maintenance costs without suffering payload or performance penalties. Another heavy-duty option in the works is Peterbilt’s Model 386 Hybrid Electric (HE), which uses Eaton’s hybrid components to provide engine-off cab comfort and to assist the diesel engine with acceleration. Expected to be commercially available in 2010, Peterbilt officials say third-party testing has shown fuel savings in the 5-7% range.
Vikner pointed out fuel has climbed from just 9% of the total cost of operating a truck in 2002, to 35% today. With well over two million long-haul Class 8 trucks on North American highways, the potential savings possible in this segment will undoubtedly drive further efforts to develop a feasible, cost-effective hybrid solution for long-haul trucks.