Enviro-Fleet's roof-mounted heating and cooling units are available in two sizes, with 13,500 or 15,000 Btu of cooling. Both have 5,600-Btu heaters. Photo: Enviro-Fleet
Enviro-Fleet's roof-mounted heating and cooling units are available in two sizes, with 13,500 or 15,000 Btu of cooling. Both have 5,600-Btu heaters. Photo: Enviro-Fleet

By Paul Abelson

"When in the course of public endeavors, it becomes necessary to idle engines in order to accomplish assigned tasks … ”

Maybe it's not in our Declaration of Independence, but until now, work truck operators have had no alternative to idling. To operate a power take-off, the engine must be running while the truck is stationary. Plus, an idling truck's climate-controlled cab often provides refuge for work crews during cold winters and hot summers.

As air quality standards evolve, idle reduction technologies have gotten a lot of attention. In the early 2000s, the Department of Energy began promoting idle reduction primarily as a fuel-saving strategy. Now U.S. EPA, the California Air Resources Board, and other entities have enacted anti-idling laws aimed at reducing pollution.

There are several good reasons public works fleets should be on board:

High fuel prices, the first and most obvious. Even if you have an advantageous purchasing contract, today's prices will eventually catch up.

Public image is always a factor for high-profile municipal fleets. People equate idling with air pollution, and frown upon fleets that idle excessively.

Avoiding fines. In some jurisdictions, especially in California, public works fleets have been fined for violating pollution requirements and idling restrictions. When enforcement is the responsibility of a pollution abatement organization, no fleet is immune.

Fleet managers now have access to alternatives, including the following options, which can keep drivers and crews comfortable without idling.

Generating heat (and cold)

The most common idle reduction technology is the auxiliary power unit. With small diesel engines, the units generate electric power or mechanical energy to run air conditioners and heaters.

The units power inverters that change 12-V direct current (DC) to 120-V alternating current (AC), providing household current in trucks. AC provides more options for heat and air conditioning. Many inverters also have battery chargers.

Fuel-fired heaters were developed because air-cooled engines didn't provide enough heat. Unlike engines, which create multiple controlled explosions, fuel-fired heaters have a continuous flame that creates virtually no pollution.

Heat pumps can also warm truck cabs by drawing in and heating outside air. They can be driven electrically, by generators or battery power, or mechanically by an auxiliary power unit.

Alternatively, the Autotherm Energy Recovery System captures heat from the engine block after it shuts down, and blows it into the cab. This system is well-suited for light- to medium-duty truck cabs, but the heat is limited to “about four hours on a winter day,” according to the manufacturer, Enthal Systems Inc.

Battery-powered options

Batteries can also power hydraulics and other devices that once required an idling engine and a power takeoff. Some hydraulic boom operations can run almost a full shift on battery power alone.

Many manufacturers offer systems that run on absorbed glass mat (AGM) batteries, with greater power density (electricity available per unit of weight) than traditional lead-acid batteries. They offer racks to hold multiple batteries and an optional inverter.

Ultra capacitors, about the size of a Group 31 battery typically used in diesel trucks, can start a large truck. A battery box can hold one ultra capacitor and several AGM batteries with no significant increase in weight.

Bergstrom's NITE hybrid system- has an electric air conditioner and an Espar fuel-fired heater. An optional, small (1.4 kilowatt), single-cylinder Kohler generator keeps AGM batteries charged.

Several manufacturers offer 12-V DC air conditioners that require enclosures for work truck cabs. Typically, electric air conditioners provide about 10 hours of cooling, while fuel-fired systems work as long as fuel is available. (Keep in mind that many smaller units are designed to maintain temperature in an already cool cab. Don't expect them to rapidly chill a cab that has been sitting for hours in the desert heat.)

Enviro-Fleet's self-contained, roof-mounted heating and air conditioning units are ideally suited to public works vehicles. No plumbing for refrigerant is needed; only a source of 120-V AC current.

What the trade calls “truck stop electrification” or “shore power” is the most effective and economical power source. It can be used anywhere trucks are stored, and only requires outlets for 110/120-V DC current. Operators can connect trucks to the outlets to top off batteries or run climate-control systems while in a yard or garage.

The needs of hybrid vehicles are spurring battery technology, including lightweight lithium and nickel chemistry. These batteries will have power density greater than the best we have now.

The biggest hurdle for adopting the new technologies is cost. A fuel-fired heater alone can run from about $1,000, while a fully featured auxiliary power unit can top $10,000. Enviro-Fleet's heating and air conditioning combination units start below $3,000, not including the source of AC electricity. Fuel savings and delayed maintenance will offset these costs, and prices will drop as demand grows. Consequently, we'll see more use of electricity for idle reduction.

— Paul Abelson (truckwriter@wowaccess.net) is a former director of the Technology and Maintenance Council (TMC) of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.