Cover Story
American Idle
Decisions, decisions,: Avoid making impulse purchases

By Paul Abelson
senior technical editor

When it comes to finding the right idle-reduction technology, you’d be well served to heed the advice offered by Smokey Robinson and the Miracles – you’d better shop around.

Today, there’s widespread concern that CARB restrictions will spread to other states and to pre-2007 APUs. Those who bought before ’07 now have to worry that their equipment may become obsolete and they’ll be back in the market for a compliant idle-reduction system.

Recent advancements may give the industry a glimpse into the future as to what may pass the test with the stricter regs that are popping up everywhere.

For example, both Carrier and ThermoKing developed DPFs – diesel particulate filters – that work with their APUs. Independent manufacturers are developing DPFs that can retrofit to APUs.

Although altering engine exhaust systems certified by the Environmental Protection Agency is against the law, there is nothing to stop truckers from adding DPFs to non-regulated engines. In fact, California and other states may eventually require it.

Cummins’ Comfort Guard offers two alternatives. The APU has its own DPF, or it can route its exhaust through the main Cummins engine’s DPF.

With diesel prices ranging from $4.50 per gallon to more than $5 in some areas as of press time in mid-July, idle reduction is just as necessary for economic survival as driver comfort these days.

At the 2007 Society of Automotive Engineers Commercial Vehicle Meeting, Linda Gaines, Ph.D., from Argonne National Labs presented a study on idle reduction. Using the price of $3 per gallon, the study projected that payback on APUs was three years or less. At $4.50 it dipped below two years. Other idle-reduction devices had payback as low as a year or less.

Although payback for an APU is rapid, APUs still require substantial upfront investment. Smart vendors are developing lease-purchase plans. One has a $170-per-month payment for a device that will save $500 monthly. Such savings claims are realistic, according to the Argonne study. It showed that idling over a five-year span will cost $30,000 – or more – based on $3 diesel.

Unfortunately, even with help from the EPA’s SmartWay Finance Center, not every owner may qualify to finance an APU. And some drivers would rather not have any engine running while they sleep.

No matter what system you decide to use, insulate first. Idle-reduction is all about managing heat, either containing or excluding it. (See how to insulate your cab on Page 74)

You can get heat from an APU, a fuel burner, or a ceramic heater that uses household current through an inverter or shore power.

The most efficient way to heat a cab is with a fuel-fired heater. It keeps you comfortable in winter for as little as 0.05 gallons per hour. (That’s not a typo. It’s five one-hundredths of a gallon per hour – less with good insulation.)

As of press time, Espar and Webasto had been certified for California use, and Teleflex’ Proheat Air should be soon. The efficiency of these systems is why hybrid units from Carrier and ThermoKing and the Bergstrom NITE system use fuel-fired heaters.

Electricity is an efficient and convenient source of power, but it has limitations. Inverters change direct current to alternating current for use by household appliances.

In recent years, absorbed glass mat battery technology has improved. Energy density, the measure of how much current is available per pound of battery, is higher with this type of battery than with any others using lead-acid technology. If a set of conventional batteries gives eight hours of service, absorbed glass mat technology may give 10 to 12.

Batteries are a limiting factor. A driver may have to reduce air conditioning in extreme temperatures, giving up cooling power, cooling time or both. Batteries can, of course, be recharged. But, according to the Argonne study, recharging takes a little more than one-third of a gallon of fuel per hour that the air conditioning is used.   

Truck stop electrification is a good source of electricity for air conditioners, refrigerators and heaters. Truck wiring kits are inexpensive and easy to install and use. But electrification is not generally available, especially near shippers and receivers. Estimates are it is still a decade away. Other than IdleAire, which is in bankruptcy with an uncertain future, electrification growth has been slow in truck stops.

Cooling with cold storage is still in its infancy. It uses the output of the truck’s air conditioner to chill substances in the cold storage unit. When the engine air conditioning is off and the fan reverses, the storage units absorb heat from cab air, cooling it. Like batteries, cold storage capacity is limited, and the systems are marginally effective in extreme climates.

As alternatives to APUs, high-capacity batteries seem to hold great promise for the future. Most OEMs offer hybrid idle-reduction systems combining absorbed glass mat batteries to drive air conditioning with fuel-fired heaters.

Developments in hybrid trucks show that lithium-ion battery packs may be better in the not-to-distant future. The greater the energy density of the battery pack, the longer and harder the air conditioner will run.

Ultimately, the only end-all solution to meeting the demands of idle-reduction is a source that can run indefinitely at full power providing all the power a driver needs. That is what the hydrogen fuel cell offers. It combines hydrogen with oxygen and releases electricity, exhausting water vapor. Fuel cells have been developing at an accelerating pace and may be the ultimate solution to the challenges of idle reduction. LL

Paul Abelson can be reached at