Auxiliary Power Units Making Inroads on Fire Apparatus

Alan M. Petrillo

Auxiliary power units (APUs)-small diesel engine and generator combinations that have been used for years on airliners, locomotives, and over-the-road trucks to handle electrical, heating, and air-conditioning while the vehicle is stationary-are making more frequent appearances in fire apparatus.

Manufacturers using APUs on fire vehicles say they are responding to requests from fire departments for ways to cut down on main engine idling time, saving fuel and reducing regeneration time.

Green Edge

Scott Oyen, vice president of sales for Rosenbauer, says his company introduced its Green Star idle reduction technology nearly three years ago, which can be incorporated into any vehicle Rosenbauer makes.

“The basis of the Green Star is in the electronics, where we take a diesel-driven generator and add the intelligence of electronics to turn the unit into a fuel saver,” Oyen says. “Our diesel APU is designed to provide heating, air-conditioning, and 12- and 120-volt electrical while the vehicle’s main chassis engine is shut off.”

Donley Frederickson, Rosenbauer’s national sales manager, points out, “Today’s fire service is a constantly changing community organization where we’ve seen the role of fire departments take on more responsibilities for medical calls, rescues, and hazmat incidents, for example. Eighty percent of calls fire departments respond to result in fire apparatus needlessly idling for between 10 and 40 minutes per call.”

auxiliary power unit (APU) on its apparatus, controlled by its Green Star electronic technology and powered by a Kubota diesel engine
(1) Rosenbauer offers an auxiliary power unit (APU) on its apparatus, controlled by its Green Star electronic technology and powered by a Kubota diesel engine. (Photo courtesy of Rosenbauer.)

Frederickson notes that engine manufacturers say a big block diesel engine uses a minimum of one gallon of fuel per hour of idling. An eight-kW diesel generator APU, he says, uses approximately one quart of fuel per hour while operating under a full load. He adds that an idling main engine puts more unspent diesel soot that occurs while the engine operates at cooler temperatures into the vehicle’s diesel particulate filter (DPF). “While the APU doesn’t alter the chemical makeup of diesel emissions,” he says, “it does reduce the amount of nitrogen oxides (NOx) that are released overall.”

Oyen notes that an APU can run off of many different fuels, but Rosenbauer chose diesel so its Green Star APU would run off the vehicle’s chassis fuel tank. Besides the diesel-driven APU, Rosenbauer also makes two battery versions, called Smart Batteries-one sized to provide 12-volt power on a scene for warning and compartment lighting through lithium-ion batteries and another using Smart Technology lithium-polymer batteries that can power all lighting, including scene lighting, and some 120-volt usage on a vehicle.

“An APU can replace a vehicle’s generator,” Oyen says. “For instance, the Tacoma (WA) Fire Department doesn’t put generators on its apparatus but rather uses Smart Batteries to run all their lighting needs,” he says.

Green Star features fully integrated automatic engine controls, Oyen says, where an apparatus operator can have a hands-free system activation that automatically starts the APU and shuts down the main engine. If needed, he notes, the controls will restart the main chassis engine to prevent a low-voltage situation. Green Star can be operated in either automatic or manual modes.

The Smeal Fire Apparatus APU is designated the SG-09, which is a nine-kW generating unit
(2) The Smeal Fire Apparatus APU is designated the SG-09, which is a nine-kW generating unit. (Photo courtesy of Smeal Fire Apparatus.)

Software Control

Joel Konecky, regional sales director for Smeal Fire Apparatus, says that Smeal “has seen a huge explosion in interest in our SG-09 APU, which is a nine-kW unit. We started installing them on pumpers and 105-foot aerials we built for the Charlotte (NC) Fire Department, and we’re doing more for them. Also, the Toronto (Canada) Fire Department has six 105-foot Smeal aerials with SG-09 APUs on them.”

Konecky says Smeal uses a software-based control system for its SG-09. “The system monitors the J1939’s transmission and engine data,” he says, “and after a given period of time where the parking brake is set, the transmission is in neutral, and there’s no need for the PTO or fire pump, it automatically starts the SG-09 system and shuts the chassis engine off. The operator doesn’t have to push any buttons for this to happen, but he can override the system at any given time if necessary and reset the system with a single button.”

While the SG-09 APU is running, it continues to monitor the main chassis engine temperature and will restart the chassis engine if needed to keep it out of a cold temperature situation, Konecky says, a design feature aimed at fire departments operating in colder climates.

electronic display that shows all phases of its operation

(3) Smeal’s APU features an electronic display that shows all phases of its operation but allows an operator to run the system manually. (Photo courtesy of Smeal Fire Apparatus.)

Smeal also makes a SG-09CR APU version that integrates the chassis heating, ventilation and air-conditioning (HVAC) system with the HVAC system on the SG-09 to free up about 35 to 45 horsepower (hp) off the chassis engine. “This allows a customer to use a less expensive engine or different chassis model,” Konecky says, “and the customer can see savings right away on the apparatus yet still get the same performance as it would with a larger engine.”

Konecky notes that Smeal’s research shows that 55 to 65 percent of the time that a chassis engine runs is idling time, which means that half of its running time it is sooting up the DPF. “Using an APU can cut engine regeneration by at least a third and maybe up to half,” he says. “And, there’s also the environmental aspects of having to change the main engine oil less frequently.”

As far as cost, Konecky says that if a department already will be placing a generator on a new apparatus, it will already have incurred that cost. “If you deduct that cost, adding an APU to a fire apparatus will run between $10,000 and $17,000, depending on the options offered for cold weather areas, such as wet pumps where a small electric pump is used to circulate water through the fire pump.”

Spartan ERV currently offers an APU powered by a Kubota diesel engine
(4) Spartan ERV currently offers an APU powered by a Kubota diesel engine that provides power for all warning and compartment lights. Models in eight- and 16-kW sizes will be available later in the year. (Photo courtesy of Spartan ERV.)

Locating the APU

Dave Van Steeg, director of engineering for Spartan ERV, says his company has just stepped into the APU arena, offering three units: a base unit, an eight-kW unit, and a 16-kW unit. “Each of the models uses a Kubota diesel engine that pulls fuel directly from the chassis fuel system,” Van Steeg says. “They are small, compact units, designed with a nesting and belt-driving system that keeps the unit nearly square.”

The base unit is about a 26-inch cube, Van Steeg notes, while the 16-kW APU is about a three-foot cube. Spartan ERV’s base unit provides power for all warning and compartment lights, he says, while the eight- and 16-kW units can handle a vehicle’s 120-volt systems and plug-in cord reels.

“We often put the APU in the dunnage area of the pump house or the hosebed near the fill towers,” Van Steeg says. “On a 48-inch pump module with crosslays, the basic unit fits neatly on top.” The APUs will be available on all of Spartan ERV’s chassis models and are retrofittable on any Spartan chassis. The base unit is available now, Van Steeg notes, while the eight- and 16-kW units are being third-party tested and will be available in the third quarter of this year.

Great Expectations

Oyen sums up the advantages of adding an APU to an emergency vehicle. “When teamed with Green Star, an APU will significantly reduce idle time of the main chassis engine, which saves the problems that come with idling, such as plugging of the DPF. Plus it increases the lifespan of the main engine and its components, reduces the frequency of maintenance and repair, and saves at least half a gallon of fuel per hour of operation.”

Konecky adds, “As far as emerging technology for fire apparatus, I think APUs will be around for quite a while.”

ALAN M. PETRILLO is a Tucson, Arizona-based freelance writer and is a member of the Fire Apparatus & Emergency Equipment editorial advisory board. He served 22 years with the Verdoy (NY) Fire Department, including in the position of chief.

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