By Paul Abelson
senior technical editor
Back in the day, no one cared about idle reduction. There weren’t any regulations prohibiting it, fuel was cheap, rates were regulated, and engines were rebuilt every three years or so.
A few forward thinkers realized that the eight to 10 gallons of fuel burned each night did nothing to get the truck down the road, but contributed to pollution and engine wear.
Back in the day, there weren’t many alternatives to idling.
There were gasoline-fueled engine heaters called the Hot Box, but many drivers feared cab fires from the gasoline. A couple of German manufacturers, Espar and Webasto, sold heaters in Canada, but U.S. distribution was as weak as demand.
Generators and auxiliary power units had their start when some innovative truckers mounted engines from Chevy Vegas and Ford Pintos behind their cabs. The gasoline wasn’t as much of a threat because there was no continuous flame. If the engine broke, replacements were available at junkyards for under $100.
The truck’s main engine was kept warm by having it serve as the cooling system for the “pony engine,” as the small engines were called. Their alternators kept batteries charged, and car air conditioner systems provided cooling.
Entrepreneurs took that concept and created self-contained generators and APUs.
It’s a good thing they did. Today, everyone is concerned about idling. Regulations prohibit it, fuel isn’t cheap, rates aren’t regulated, and engine rebuilds cost an arm and leg.
Today, APUs range from 3.5 to 9 kilowatts; costs start at $6,000. Depending on their features and the functions they are expected to perform, high-end units may cost $11,000 to $12,000 before installation.
Electronic controls have been a boon in many truck devices, but may be the bane of APUs. Unless circuits and grounds are well-protected and waterproof, components may not function properly, according to APU pioneer Rex Greer of APUs by Rex LLC. Twelve-volt systems are more rugged, so his approach is to go back to the electro-mechanical basics.
Many suppliers today are driving air conditioning with battery power. Deep cycle absorbed glass mat batteries have proven reliable. Four can provide adequate 12-volt DC power for up to 10 hours of air conditioning. They’re not made to cool down a truck that’s been heat-soaked in the Arizona sun over a 34-hour restart. However, battery powered units can maintain temperatures in a cab that has been cooled down by the truck’s OEM air conditioner in most conditions.
The development of low-cost inverters, devices that change direct current from the battery into alternating current similar to household current, made the use of more capable 115-volt AC air conditioners practical on trucks. Dometic, for example, offers a unit with 14,000 Btu/hour cooling capacity. It can run on “shore power” or battery power through an inverter.
Shore power gets its name from the boating industry. Yachts are wired to use plug-in appliances like those found at home. When at the dock, an extension cord runs to a power outlet on the shore, giving the source its name.
Heat can be provided several ways. An air conditioner can be turned into a heater if designed to work as a heat pump, a device that takes thermal energy from one place and pumps it to another. As an air conditioner, it absorbs heat from inside the cab and removes it to the outside. As a heat pump, heat is drawn from outside the cab and released inside.
A more efficient way of heating cabs is through the use of fuel-burning heaters. Most are made by Espar, Teleflex and Webasto. These heaters burn as little as 1 gallon of diesel in 10 to 20 hours and heat the cab with up to 14,000 Btu.
Coolant heaters with cab fans can warm the entire truck. The problem with coolant heaters is the high current draw of the OEM fans, as much as 15 amps/hour per fan. Fuel-burning air heater fans draw less than 2 amps/hour. That electrical efficiency led to the development of hybrid units.
In automotive language, hybrid refers to the combining of two power sources, usually gasoline or diesel coupled with electricity. For idle reduction, the combinations are usually electric air conditioners and fuel-burning heaters.
The NITE System from Bergstrom has a 7,200 Btu air conditioner packaged with Espar’s AirTronic D2 or optional D4 heaters. Virtually all battery-powered APUs will serve you well over an eight to 10 hour span, but not during a 34-hour restart.
That’s where shore power helps. Bergstrom developed the NITE Plus for longer use. It runs off four 12-volt AGM batteries. When the batteries run down, a small Kohler generator kicks in solely to recharge the batteries.
Refrigeration manufacturers offer hybrid heating and air conditioning systems. Thermo King’s TriPac APU uses a diesel engine to power a 13,000 Btu air conditioner. Heat is provided by an Espar air heater. Carrier Transicold’s air conditioner cools at 10,000 Btu/hour, while its Teleflex ProHeat heaters yield 5,000 or an optional 10,000 Btu/hour. Both use alternators to keep the truck’s batteries fully charged to provide power for the hotel loads.
Back in the day, truckers started their engines Oct.1 for heat and didn’t shut them off until Sept. 30, after air conditioning season. Today, many use their APUs every minute their trucks are off.
That is causing unnecessary wear and tear on mild days when a roof vent with a 12-volt fan will often keep the cab ventilated, saving fuel. An electric blanket is a passive fuel saver. Just be sure to use a low-voltage battery disconnect.
The latest idle-reduction technology is thermal storage. Webasto’s BlueCool is a cold storage system. It produces cool air using thermal energy stored in a frozen graphite and water matrix. A pump circulates coolant through the storage core while four fans draw in warm bunk air and pass it across the exchanger.
The air gives up its heat to the chilled mixture circulating through the exchanger and returns to the bunk through adjustable openings on the air handler.
Webasto added a shore power option to BlueCool this year. When plugged in, the system can run continually. On its own, the system can cool for about 10 hours.
The Autotherm T-2500 uses heat stored in the engine and pumps coolant through your truck’s heaters. When coolant temperature drops below 95 degrees, it briefly runs the engine.
Delphi has announced an APU powered by a hydrogen fuel cell. The 5 kw unit can run on diesel or natural gas, releasing hydrogen from the fuel. It will be on the market in 2012.
With diesel hovering around the $3 mark, the U.S. Department of Energy projects payback for most idle-reduction devices to be under 18 months. Even the most expansive full-featured APUs pay for themselves in less than three years.
The mushrooming of anti-idling regulations around the country has yet to slow. More and more states, counties and cities are making key-off living a mandatory existence for truckers.
Manufacturers took the concepts developed by those early forward thinkers and stepped up to the plate, giving truckers a wide range of options. It remains to be seen if within that existing technology there lies the ultimate answer to key-off living or if the next generation will be the one to take anti-idling technology to the next level. LL