Biggest growth markets are medium- and heavy-duty trucks because of fuel savings, with Class 8 leading the way
Mar 1, 2010 12:00 PM, By Rick Weber
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:
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.
Reduced environmental impact: significant opportunity for full electric (zero emissions) mode; lower drive-cycle emissions; and noise reduction.
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?
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.
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.”
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