By Paul Abelson
senior technical editor
Six short years ago, the Department of Energy held a workshop titled “Idle Reduction Technologies for Heavy Duty Trucks.” The purpose of the workshop was to obtain input to help create demonstration projects that would show the value of idle reduction devices.
Participants included truck manufacturers, idle-reduction equipment suppliers, over-the-road (only) fleets, and the Owner-Operator Independent Drivers Association. According to an OOIDA survey at that time, only 16 percent of members sampled used any idle-reduction devices.
Devices available through OEMs were limited to Detroit Diesel’s Optimized Idle, which stopped and restarted the engine to maintain temperature and battery strength, integrated wiring for shore power and diesel-fueled heaters for warmth. Generators and auxiliary power units were strictly aftermarket items in 2003, often dealer-installed.
The demonstration projects were developed to address the perceived barriers to idle-reduction device acceptance: cost, reliability and weight. Additional concerns involved payback, effects on engine wear, impact on emissions, impact on resale value and user satisfaction. The California Air Resources Board was just starting to become involved in reducing idling.
How things have changed in just six years.
The Environmental Protection Agency is now the lead agency on idle-reduction of heavy-duty trucks. And the technology has moved forward at warp speed.
Initially, idle reduction was promoted primarily as a fuel-saving strategy. Now CARB, the EPA and the many states that have enacted anti-idling laws are out to reduce pollution. The Department of Energy wanted to reduce idling through a voluntary, cooperative effort to convince stakeholders that it was an economically sound decision. CARB and EPA just say, “Do it.”
Today’s technologies are almost as different from those of 2003 as the CARB approach is from DOE’s.
Devices like cold storage were more theoretical than practical. Evaporative cooling was limited to homes in dry climates, and battery technology couldn’t run air conditioning and hotel loads – refrigerators, televisions and video players, microwaves and other amenities – all night and still start a truck in the morning.
The primary technology was, and still is, APUs or generators. Generators do one thing. They use a small diesel engine to generate electric power. Once you have electricity, you can use it to power an electric air conditioner or any of the devices you use for comfort and convenience. APUs are multifunctional devices. Besides driving either a generator, an alternator or both, they may power an air conditioner or an air compressor mechanically.
APUs can also power an inverter, a device that changes 12-volt direct current to 120-volt alternating current, to provide 120-volt household current. Using household current gives you more options for heat and air conditioning. Many inverters also have circuitry to charge batteries without overcharging or damaging them.
Fuel-fired heaters have been around longer than APUs. They are limited to providing heat, making them suitable for northern climates only if they’re paired with another device. Unlike diesel engines that burn fuel in a series of controlled explosions, fuel-fired heaters have a continuous, clean flame much like an oil-burning home furnace. They create virtually no pollution, and many have been certified by CARB for use in California.
Cabs can also be warmed by heat pumps. Like air conditioners that absorb heat from one location, inside a cab or home, and transfer it to the atmosphere, heat pumps can also draw heat from air and release it into a cab. Heat pumps can be driven electrically, by generators or battery power, or mechanically by the APU’s engine.
After engine shutdown, a great deal of heat remains in engine blocks and in the coolant inside hoses and cab heaters. The Autotherm Energy Recovery System – distributed by Bergstrom – is a device that captures the heat and blows it into the cab. The unit is best suited to day cabs, since total available heat is limited to “about four hours on a winter day.”
While APUs currently provide electric or mechanical power for most air conditioning used for engine-off cooling, many manufacturers are turning to improved batteries. Absorbed glass mat batteries have far greater power density (available electricity per unit of weight) than traditional lead-acid batteries. Several manufacturers have racks or containers that house multiple absorbed glass mat batteries, an inverter and an air conditioner. Coupled with a fuel-fired heater, they provide about 10 hours of cooling or heating for as long as fuel is available.
Ultracapacitors accumulate large charges of electricity and can quickly discharge the current to start engines. They are about the size of just one Group 31 size battery, so one in a battery box leaves room for two or three additional absorbed glass mat batteries with no significant increase in weight.
Most four-battery absorbed glass mat packs will drive air conditioners up to 10 hours. That’s not a problem until you are on a 34-hour restart. That’s why Bergstrom added a small (1.4 kw) single-cylinder Kohler generator to its NITE System. Its sole purpose is to keep the batteries topped off. Other than the Espar heater, everything runs on electricity.
Evaporative cooling is an old technology recently adapted to cooling truck cabs. It consists of a highly absorbent filter, a pump to deliver water from a tank, a perforated tube manifold to transfer the water onto and into the filter and a fan to blow air through the filter. The water in the filter draws heat from the air as it turns to vapor. That cools the air, although it does raise the relative humidity somewhat. Evaporative cooling works best in hot, dry climates where a little extra moisture in the air would be welcome. It is far less effective in hot, humid climates because it relies on dryness to vaporize the water.
Webasto is a major proponent of cold storage, a technology that diverts some of the air conditioner output to a chamber, which holds material that undergoes phase change. That’s the same process that changes water from liquid to solid, to ice. Phase change releases heat when freezing occurs, and absorbs heat when ice liquefies. Air is blown over Webasto’s BlueCool Truck material by four fans. The 17,000-Btu cold storage cell is said to maintain a cab at 70 degrees for nine hours, with ambient temperatures above 90 degrees. The fans are the only moving parts during operation.
Keep in mind that many smaller air conditioners and cooling devices like evaporative coolers and BlueCool Truck are designed to maintain temperature in an already cool cab. They are not designed to rapidly chill a cab that has been hot-soaked for a weekend in Arizona.
With many idle-reduction devices driven electrically, truck stop electrification is the most effective and economical power source. It is not just for truck stops, but for anywhere trucks might stop, including shippers’ and receivers’ yards and public rest areas. For a nominal fee, you get to plug into a post near your truck. Once your extension cord is connected between the post and your internal wiring, you have the power to provide all your hotel loads and keep your starting batteries topped up.
Battery development is being spurred on by the needs of hybrid vehicles. New battery technologies are building on our knowledge of lightweight lithium and nickel chemistry. They will have power density greater than the best we have now. The problems aren’t with the technologies, but with their costs. As demand grows, prices will drop, and we’ll see more use of electricity for idle reduction.
As far as the industry has come in six short years in terms of available equipment to foster compliance with anti-idling regulations – it will be interesting to see where the warp speed of technology will have the industry in another six.
Paul Abelson can be reached at firstname.lastname@example.org.