BY 2012, most truck makers in North America will be commercially manufacturing and selling hybrid trucks, and the medium- and heavy-duty markets represent the biggest growth area because of fuel savings, according to a Frost & Sullivan study.
In “Hybrids Today & Tomorrow,” Vern Caron, director of hybrid vehicle technology at ArvinMeritor, said that while there are fewer Class 8 units, they consume four times the amount of fuel used by medium-duty vehicles.
While the pickup and delivery segment could experience a 40% improvement, it would amount to 833 gallons of fuel a year for a vehicle traveling 25,000 miles a year (12 mpg), compared to 2727 gallons for a Class 8 vehicle traveling 120,000 miles a year (6.6 mpg), for a 15% improvement. He said the typical idling loss is 0.7 gallons per hour for six hours.
Regenerative braking accounts for 10% of fuel consumed, and it's assumed half is recoverable. The potential energy for an 80,000-lb GVW vehicle descending from 5000 ft to sea level is approximately 153kW-hr.
“We can't possibly begin to recover that amount of energy in regenerative braking, so we need to get rid of that energy somewhere,” Caron said. “Engine brakes are wonderful for doing that. They take all that energy stored in the vehicle and dump it out the exhaust. So there's going to be a need for a long time for engine brakes in those applications where they're in a lot of grade issues.”
Caron said there's a goal to cut in half the 15kw of constant power consumption needed to run accessories on a vehicle, and it can be done by electrifying accessories. He said Eaton is doing it in its hybrid programs by replacing the alternator with an IGBT power inverter, an electrically driven HVAC (eliminating the freon compressor), and an electrically controlled air compressor.
“If I can operate on continuous speed on an air compressor, I don't necessarily need as large a compressor as I do today,” he said. “I can run continuously or as a heavier duty cycle.”
He said that with the Series mode (less than 50 mph), the engine speed and load are decoupled from the driveline speed, and the engine may or may not be operating depending on the battery SOC. With the Parallel mode (more than 50 mph), the engine speed is driven based on driveline speed and gear ratios in the hybrid drive unit.
Depending on the drive cycle, fuel consumption improvements as high as 20% are achievable with a targeted payback of at least three years.
The benefits:
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Improved fuel economy: no overnight engine idling; no engine idle during stops; regenerative braking and energy recovery; accessory loss reductions; and narrow range engine operation.
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Reduced environmental impact: significant opportunity for full electric (zero emissions) mode; lower drive-cycle emissions; and noise reduction.
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Enhanced safety and function: improved braking performance; improved acceleration; fully automatic, smooth operation, less driver distraction; and technology accommodates future innovations and needs, including plug-in capability, high efficiency engine concepts, etc.
“These vehicles are very nice to drive,” Caron said. “People like to drive them.”
What's different about them?
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Components removed: conventional transmission; clutch; retarder/engine brake; 80% of lead acid battery capacity; engine-driven air compressor, AC compressor, and power steering; starter; alternator; and flywheel.
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New content: hybrid drive; hybrid controller; li-ion battery packs; power electronics; electric hvac; electric power steering; electric air compressor; and dual loop cooling system.
Things that remain the same: engine and engine controller; air-brake system; accelerator, brake, and PRNDL control inputs; and chassis and body controls.
“If you want to go on a diet, it's not going to work if you eat a lot of low-calorie food along with regular stuff,” he said. “You're probably not going to lose a lot of weight. If you want to hybridize a vehicle, it's probably not going to work if you have a lot of hybrid components along with regular components. You're going to get this overloaded, huge, bloated vehicle on your hands. We're very motivated to take some things off.”
Next Page: Eaton and fleets
He said high-voltage safety means that a center-of-pack mechanical disconnect is preferred for batteries (rather than contactors), the lockout/tagout must be adhered to, and an absence of high voltage must be verified.
“Once you've done that, these systems are extremely safe to work on,” he said.
He said diagnostics will be J1939-compatible, but there will be new messages for batteries, for motors and generators. With electric machines, bearings, rotors, and stators can be serviced.
“There's a lot of value and opportunities in battery packs,” he said. “From our viewpoint, we want to see standardization within the industry: voltage (eg 350V), vehicle mechanical interface, vehicle electric interface, and standardized messages.
“We expect to achieve a seven-year-or-better life. Full charge/discharge ratings have moved from 500 towards 2500 cycles within the past several years. That's a huge improvement. To minimize service impact, the goal is to minimize non-required content within battery packs by eliminating contactors, eliminating pre-charge circuitry, and having packs that can be safely disconnected and serviced as a unit.”
He said Gen I truck testing with Wal-Mart began in January 2009, Gen II design completion came in the fourth quarter of 2009, and Gen II vehicle build is set for the third quarter of this year. Design validation prototypes come this year and 2011, with fleet trials in 2011 and 2012, and potential start of production in 2012-2013.
“It's largely dependent on the cost of fuel,” he said. “If it's $7 a gallon, it will move faster. If it's $2.50 or $3, then this technology is not as attractive.”
Eaton and fleets
Robert Golin, market planning & business development manager for Eaton's Hybrid Power Systems Division, said FedEx Express, UPS, Coca Cola, and a number of utilities have incorporated the Eaton HEV into their fleets, with over 30 million miles logged. On the hydraulic hybrids side, the Eaton parallel hybrid hydraulic system is the only hybrid system available for the refuse industry.
“The value proposition for any hybrid is dependent on the vehicle's duty cycle,” he said. “If you have a duty cycle that needs high storage capacity and has auxiliary demands like HVAC, booms, and PTOs, then electric is a good idea. If you have a power density requirement because there's a lot of stop-and-go and the truck is heavy, what you're harvesting is kinetic energy. That's where a hydraulic system would do better.”
He said with diesel-electric hybrid for motive power, the parallel direct diesel-electric power system provides a blend of diesel and electric power as demanded by application and system design. With diesel-electric hybrid for motive and auxiliary power, the parallel direct diesel-electric power system provides motive power plus auxiliary power for non-motive work.
With the Hydraulic Launch Assist HLA, the parallel hydraulic power supplements the conventional powertrain for high-intensity stop-and-go applications.
“This does just a regenerative function,” he said. “It's a parallel system. Because this is designed for refuse, for example, if you are over 24 mph, it's off. Why? Because that means the truck is going back to the yard and garage. It's on the highway, not doing a stop-and-go garbage collection cycle.”
With the Series Hydraulic Hybrid, the direct series hydraulic power system replaces the conventional drivetrain with diesel power converted to hydraulic motive power.
“You're getting rid of everything behind the engine,” he said. “So the only function that engine fills is powering the pump. All controls are on the hydraulic side.”
He said on the HLA side, Eaton has 50 production units, mainly on chassis by Peterbilt, the 2007 launch partner. He said it's the only hybrid available in heavy-duty refuse.
The HLA system has a three-year payback based on fuel savings of 1000 gallons per year per truck from recovered brake energy; increased service intervals, with a brake-service interval demonstrated in fleets to increase by four times, saving $6000 a year on brakes alone; productivity improvement due to 20% increase in acceleration.
Golin said the movement for renewable energy only figures to provide more opportunities for hybrids.
“There are some people working on charging pods,” he said. “There are some people working on smart grids. Those are the ones that are very excited because everything you're working on is coming their way. They're going into the electric grid. Those guys are IBM, Cisco, GE. They are investing a lot of money right now to come in and grab some of that business.
“That's an opportunity for you, if you are allocating resources. Train some people to bring those electrical engineers and technicians, because your vehicles are going to interact with them and they need to know how that works. Why not go and get certified to do maintenance repair and install those pods, because those guys don't have the network to do that? I know it seems outside the vehicle world, but think about that.
“Hundreds of millions are being invested right now by those companies, and they're very interested in taking a lot of business away from the current players in that world. Paris and London right now are working out plans for smart grids and for sustainability, moving people around the city and doing away with anything that has emissions. I think you guys can play in that world.”