From APUs to Hybrids

When John Duffy, Kenworth's manager of advanced technology, looks at auxiliary power units (APUs) being built into trucks at the factory, he sees more than an idling solution. Duffy also sees the first step in establishing a platform for a hybrid Class 8 tractor.

"We deliberately developed our Clean Power System to run on batteries to totally eliminate any issues with emissions," he told FleetOwner at a Kenworth media event held at the Paccar Technical Center in Mount Vernon, WA, which is operated by KW's parent firm, Paccar Inc.

"The first stage of that challenge is to improve the efficiency and life cycle of a battery-powered system operating in the harsh environment of trucking," said Duffy. "The bar we have to meet as an OEM is much higher in terms of reliability and durability, since we are the ones putting this into the vehicle. The actual concept of integrating an all battery-powered APU into a Class 8 tractor took just six months; the other 18 months were spent hardening it."

Duffy said the system's deep-cycle marine batteries offer 10 hours of power for moderate hotel loads, such as an onboard refrigerator, DVD player, laptop, and microwave a few times a night, plus the truck's air conditioning system. The system recharges while the truck is on the road during the day, but it can also be plugged in to shore power to run the A/C and re-charge the batteries at the same time.

According to Duffy, Clean Power makes a useful platform for exploring the possibilities of hybrid Class 8s. This is because the battery powers the truck's basic electrical system, taking over the job of running the A/C system and onboard equipment, and then being recharged by the truck's diesel engine.

"How you integrate this system is the key," Duffy explained. "Rarely have I taken a system like this from concept to production, but working so closely with this is giving us the opportunity to look more closely at its future potential in hybrid set up."

Duffy feels that the battery-powered APU not only allows the vehicle to burn less fuel but also to stay ahead of state or local diesel emission restrictions. He said the system uses roughly a gallon's worth of fuel to be fully recharged by the truck's engine over the course of the day and consumes energy at about 1/10th of a gallon per hour, compared to 3/10th to 5/10th of a gallon per hour of a traditional diesel-fired APU.

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