Auxiliary Power Units

January 1, 2006 By    

Propane industry engineers are not sitting idle as truckers face pressure to cut pollution from tractor-trailer engines left running once the rigs complete a long day’s haul.

Auxiliary power units are portable, truck-mounted systems that can provide climate control and power for trucks without idling.
Auxiliary power units are portable, truck-mounted systems that can provide climate control and power for trucks without idling.

Government regulators at the state, local and federal levels are mandating that idling time be drastically reduced, if not eliminated altogether. Truckers themselves are onboard as well, ever-mindful of the costly diesel fuel being wasted while the wheels aren’t turning.

You’ve seen – and heard – them at truck stops and parking lots everywhere; the main need for idling is to generate what’s known as “hotel load power.” In addition to heating and air conditioning systems, big rigs nowadays have coffeemakers, microwave ovens, refrigerators, televisions, computers and all manner of creature-comfort appliances. Under extremely cold conditions, idling ensures that engine oil and fuel reservoirs are kept warm enough to prevent starting and operating problems.

At idle, a modern big rig burns nearly a gallon of diesel fuel per hour just to drive an air conditioner.

A key technology for putting the brakes on idling is the auxiliary power unit. APUs – truck-mounted electrical generators – have been around since the 1950s. In more recent years, pollution, fuel-waste and noise issues have pushed the development of better efficiency of this technology.

The Propane Education & Research Council recently awarded a $25,000 grant to New West Technologies of Landover, Md. to study the feasibility of truck-mounted, propane-powered APUs. PERC also has a $350,000 grant application pending before the U.S. Environmental Protection Agency for additional research on the technology.

“We feel there is a marketing opportunity, and we’d like to see government support to help us get there,” says Brian Feehan, PERC’s managing director of engine fuel programs. “The majority of truck stops already have propane at them. Now is the time for us to be doing this work to get propane positioned as the market takes off.”

Overnight truck idling consumes an estimated 5 percent of the diesel fuel burned by the nation’s fleets. Propane may be the perfect clean and efficient remedy.

“We believe that we can be cost-competitive,” says Feehan. “The work now is integrating it into the truck. It’s going to be a small modification to existing technology.”

The idea is to install an electrical generator somewhere on the rig; small enough to be practical, but powerful enough (about 5 kilowatts) to meet drivers’ requirements. Finding a spot to mount the propane tank and run the lines is another engineering challenge.

A decision also will have to be made over whether the tank will be permanently affixed or exchangeable. The APU is expected to burn about 0.8 gallons of propane per operating hour with far fewer pollutants.

Anti-idle worship

“There’s certainly an interest” among fleet owners for a cost-effective means of generating an APU-based power alternative, says Robert Braswell, technical director of the American Trucking Association. He says the units could be sold at the local level, as most carriers are fleets with less than five rigs.

With some 460,000 long-haul trucks currently rolling across the nation, the Argonne National Laboratory estimates that idle reduction technologies could reduce diesel use by 838 million gallons per year. That translates to $1.4 billion in wasted fuel.

Studies show that drivers can also reduce engine wear by lowering their idle times, an average of 1,830 hours per year for each sleeper-cab. Over an eight-hour period, the fuel savings could provide a trucker with 24 to 40 more miles of travel before stopping to refuel. Routine maintenance can be performed less often and trucks can travel farther before needing an engine overhaul.

According to the EPA, a nationwide acceleration of anti-idling strategies over time could result in:

  • 15 million gallons of diesel savings
  • $45 million in reduced fuel costs
  • 3,000 tons of nitrogen oxide emission reductions
  • 70 tons of particulate matter emission reductions
  • 125,000 tons of carbon dioxide emission reductions

Propane, however, does face competition in its drive to the APU market.

Research is charging ahead on truck-stop electrical hookups, called “shore power.” It’s considerably more complex than running an extension cord through the window. Shore power can cost $10,000 per space, and there’s usually a required minimum of 50 hookups. Each vehicle also needs onboard equipment such as an inverter/charger at an estimated $1,500, plus another $1,500 for electric heating, ventilation and air conditioning capability.

“These are not that widespread,” says Braswell, citing the cost involved. And, a trucker needs to know that compatible shore power systems are available all along the route to be traveled.

Among the other challenges is the presence of diesel-powered APUs, including devices that run on clean diesel and biodiesel. Manufacturers have various models on the market, touting the convenience of tying into the truck’s existing fuel lines. They also pitch a sleek appearance, with units that blend in with the cab’s steps or come with snazzy chrome finishes.

Fuel cell-based APUs are yet another development being examined via private-sector research with assistance from government grants. Feehan contends that a commercially viable fuel cell APU is about 20 years away.

Delphi is striving toward a demonstration model natural gas fuel cell APU by 2009, according to Bruce Moor, the company’s business development manager for fuel cells. Delphi is also looking at diesel for this application – and propane will have a role, too.

“It’s definitely in our future to run off propane. The technology that we’re working on right now can be used with propane,” Moor says.

Feehan sees the entire field as a fascinating opportunity.

“We’re excited about it,” he says. “Anti-idling is a fairly new market segment for everybody.”

Comments are currently closed.