Freightliner LLC introduced a concept heavy-duty truck that uses fuel cells to generate electrical power for on-board vehicle appliances. The demonstration truck-a Class 8 Freightliner Century Class S/T-shows an alternative for powering auxiliary devices on a parked heavy-duty truck in lieu of idling the engine. The truck was displayed at the Department of Transportation’s National Intelligent Vehicle Initiative Meeting.

“By using fuel cells to power the comfort and convenience accessories on a parked heavy-duty truck, we cut the need to idle the engine, thus reducing fuel consumption, emissions and noise,” Government Technical Affairs for Freightliner LLC. “This technology has great potential for increasing the efficiency and comfort of commercial trucks, while reducing their environmental impact.”

Heavy duty trucks are equipped with a large number of appliances that require electrical power-everything from cab heaters and air conditioners to onboard computers, televisions, stereos, refrigerators, microwave ovens and coffee pots.

To power these devices while the truck is parked, drivers often must idle the engine. The Department of Energy has estimated the annual fuel and maintenance costs of idling a heavy-duty truck at over $1,800. Idling also produces emissions, as well as increases noise levels inside the cab and sleeper.

The Freightliner truck diminishes the need for idling by using a fuel cell auxiliary power unit to deliver electrical power.

The system was developed by XCELLSIS, a joint venture company whose ownership includes Freightliner’s parent, DaimlerChrysler AG. It includes two Ballard fuel cell “stacks” operating in series as an auxiliary power unit (APU). The stacks are housed on the left side of the truck along the frame rails.

The Freightliner demonstration truck uses proton exchange membrane (PEM) fuel cells. The fuel cells are fed with hydrogen from a 52-gal. liquid tank on the left side of the truck. Within the fuel cell, hydrogen is split into positively charged protons and negatively charged electrons. The protons can pass through the membrane, but the electrons cannot, so a voltage builds up in the fuel cell. The only by-product of this process is pure liquid water.

The fuel cell APU produces over 1.4 kw 120 volts AC or 12 volts DC power. The APU is connected to the vehicle’s electrical system through an 1800-watt inverter, which takes electricity from the fuel cells, batteries and alternator, and provides power to vehicle accessories/batteries in the required form (12v do or 120v ac). The system is thus able to support a variety of power-consuming products up to the total system wattage limits. The Freightliner demonstration truck is outfitted with an 8000 btu/hr, air conditioning unit to show the system’s capability to cool the cab without idling the engine.