By David A. Kolman
Since joining the Pepco's Rockville, Maryland fleet some three years ago, the utility's first hybrid bucket truck has seen plenty of action. On-duty 24 hours every day, the truck is dedicated to electrical troubleshooting, emergency and first responder type situations by the electric service provider to customers in Washington, DC, and Montgomery and Prince George's counties in Maryland.
The International DuraStar truck with an Altec Versalift utility body and a 42-foot-reach overcenter aerial bucket is a real standout from Pepco's 34 T&S bucket trucks. It is painted and decaled to promote its environmental friendliness. It is considerably quieter than the conventional diesel-powered bucket trucks due to its Eaton parallel electric hybrid drive system.
And there is one other distinction. The truck is one of a small group of industry pioneers.
Pepco was one of the 14 original utility participants, along with Eaton, International Trucks, the Army National Automotive Center and others, in the Hybrid Truck Users Forum (HTUF). WestStart-CALSTART established HTUF is 2006 to drive development of hybrid truck technology.
WestStart-CALSTART is a non-profit organization that works to develop advanced transportation technologies and foster companies that will help clean the air, lessen the nation's dependence on foreign oil and reduce global warming.
The 14 utility participants each placed prototype hybrid bucket trucks in service throughout North America. The trucks ranged in size from roughly 24,000 to 33,000 pounds gross vehicle weight. The objective was to assess the performance, reliability and business benefits of the vehicles, and to offer suggestions for improvements.
The results of the initial testing revealed that hybrid bucket trucks substantially increase fuel economy while considerably reducing the smog-forming emissions and global warming gases compared to the diesel-powered trucks they replaced. Another advantage of the hybrids is that their aerial devices can be operated in an electric-only mode with the engine off, eliminating engine noise and further decreasing emissions of carbon dioxide, nitrous oxide and particulate matter while workers go about their jobs.
Pepco's pilot hybrid bucket truck—number 18 of the original HTUF 24—was joined in early May at the Rockville service center by a second hybrid. It, too, is an International DuraStar 4300, rated at 33,000 pounds gross vehicle rate. It has an Altec Model L42P body with a 42-foot-reach overcenter aerial single-man bucket.
Both trucks are outfitted with Eaton's electric hybrid drive system. The system, which uses an Eaton Fuller automated transmission, maintains conventional drivetrain architecture, while adding the ability to augment engine torque with electrical torque with a parallel hybrid system.
The main components of that system are the diesel engine, hybrid drive unit, power electronics carrier (battery box), motor inverter controller, hybrid cooling system, DC/DC converter for the electric power take-off (ePTO) and to sustain the 12-volt battery charge, and optional auxiliary power generator.
The hybrid drive system recovers energy normally lost during braking and stores the energy in batteries, after which the power can be added back into the driveline during start and acceleration, explained Dennis Nero, Eaton's northeast regional manager. This capability makes the truck more efficient in standard driving by improving fuel economy and vehicle performance for a given speed, particularly in city and stop-and-go driving, where utility trucks typically spend the most time.
The stored energy is also used to provide energy for use during engine-off worksite operations for such things as aerial devices, power booms and other tools, he said.
Essentially, this is accomplished by placing a motor/generator between the output of an automated clutch and input of the transmission (flywheel), or elsewhere in the drivetrain. When the vehicle's brakes are applied, the device acts as an electric brake, generating electric current as it slows the vehicle. This current is used to recharge the high voltage batteries.
I had a chance to operate Pepco's original hybrid bucket truck. The new hybrid had just come out of the paint shop. However, I was assured by Frank Cottone, Pepco's manager of vehicle resource management, that the two trucks drive alike.
Not having driven a hybrid truck before, I wasn't sure what to expect performance-wise. I figured the truck would have to be driven differently and would be sluggish. Such was not the case.
The hybrid truck is operated in the same way as a conventional truck. The only real difference is when operating the aerial device.
To start the truck, you place the key in the ignition switch, turn it to "On" and push the "D" (for Drive) on the transmission shift console (selector pad). You then release the parking brakes, push on the accelerator and off you go. I must say, I was taken aback when the truck took off with plenty of power.
Starting the vehicle from a complete stop, the current is drawn from the batteries, turning the device into an electric motor to launch the truck, Eaton territory manager David Cunningham told me later. Once underway, the diesel engine takes over.
Overcoming inertia to start a vehicle from a stop requires more energy than that required to keep the vehicle moving once underway, he noted. By using the "free" electric energy created and stored in the hybrid's batteries, fuel consumption can be reduced.
What I found especially interesting about the hybrid utility truck was the electric power take-off (ePTO) functionality. Talk about quiet. With it, the stored energy is used for electric-only operation of the aerial device. The diesel engine shuts off and the electric motor powers the hydraulic pump that operates the aerial device without the engine running, further reducing noise, emissions, idle time and fuel costs.
To operate in the ePTO mode, the truck must be parked, with the parking brake set. The key is turned to the "On" position, but the engine is not started. The "ePTO" button on the shift console is then depressed. This done, the hydraulic controls are operated in the normal manner.
When raising, lowering or rotating the aerial device in the ePTO mode, the only noise comes from the hydraulic system itself, which is amazingly quiet when compared to a conventional diesel-powered bucket truck where the engine must keep running in order to operate the PTO to work the aerial device.
This is a bonus, as noise tends to hinder worker productivity. Among other things, with a conventional diesel-powered bucket truck when the engine and PTO running, it can be difficult for a lineman in the bucket and others on the ground to hear one another, said Gary Keeler, manager of overhead lines for Pepco's Rockville service center. That's not the case with the hybrids, because the aerial device is operated in an electric-only mode with the engine off.
Additionally, he pointed out that the reduction in engine idle time further helps promote clean air because there are no emissions while in the electric mode.
Both Keeler and Cottone said Pepco customers in the prestigious upscale Rockville area, on the outskirts of Washington, DC, are pleased with the hybrid truck's quiet operation and cleanliness. Often times, routine maintenance on power lines must be done in the early morning or late at night in residential neighborhoods, hospital zones and other noise-sensitive areas.
As the hybrid battery gets depleted while the aerial device is operating, the diesel engine will automatically start up and recharge the system, usually in just a few minutes.
When the aerial device is shutdown and returned and locked into the storage position, the "ePTO" button on the selector pad is depressed once again to shut down the electric power take-off and the key is turned to the "Off" position.
Returning to the service center, I asked Eaton's Cunningham what happens if the hybrid system malfunctions. He told me that Eatons include an additional safety feature by preventing continued operation of the hybrid components during a system malfunction while eliminating the need for towing. In effect, the truck would revert back to operating as a traditional diesel-powered truck.
The two hybrid bucket trucks are part of Pepco's environmental management program, intended to help meet the nation's energy and environmental challenges by implementing technology solutions that will reduce emissions, said Cottone. Plus, there is enhanced customer image by going "green".
Pepco is a subsidiary of PHI (Pepco Holdings Inc.), which includes Delmarva Power & Light and Atlantic City Electric. All three utilities are investing in hybrid vehicles and systems, as well as biodiesel fuel for diesel engines. Biodiesel is a clean burning alternative fuel produced from domestic, renewable resources—such as natural vegetable oils and animal fats, and contains no petroleum.
PHI is also evaluating other new technologies, Cottone said, including the use of biodegradable hydraulic oil and plug-in hybrid electric vehicle (PHEV) bucket trucks.
Company-wide, PHI has some 1,800 vehicles, from passenger cars to heavy-duty trucks. There are 68 medium- and heavy-duty utility trucks. Pepco has 34 of these.
There are nine hybrid bucket trucks across PHI's three utility brands. Five are in Pepco, with three based at the Rockville service center.
In general, Pepco's diesel-powered bucket trucks have a service life of 10 years.
Cottone figures the Pepco hybrid bucket trucks are getting a 40 to 45 percent improvement in fuel economy compared to similarly spec'd diesel-powered bucket trucks. Much of the fuel savings are resulting from the engine not having to be on at work sites for powering the PTO. The improved fuel economy has a direct impact on emissions, which is estimated to result in 40 to 45 percent reduction in CO2, VOCs and other pollutants. Furthermore, the hybrid bucket trucks use biodiesel fuel (B-10), which results in approximately 7.5 percent fewer CO2 emissions than regular diesel fuel.
No special training is necessary to operate or maintain the hybrids, noted Cottone. Preventative maintenance schedules remain the same, with all service and repair work done by Pepco at its three service facilities.
Pepco is also finding that the hybrid trucks require less maintenance, Cottone said. Because the diesel engine doesn't have to run as much, engine life is extended. Since the regenerative braking feature enhances stopping power for shorter braking distances, the truck brakes are used less often, helping to reduce brake wear.
Cottone said Pepco plans to continue to replace its T&S bucket trucks with hybrid vehicles.
In the meantime, Pepco's hybrid trucks continue to operate quietly, improve energy efficiency and reduce their impact to the environment.
About the Author:
David A. Kolman has been an award-winning trucking journalist since 1984 and has extensive hands-on experience as a truck owner and operator, and fleet and warehouse manager. He has had his Commercial Driver's License (CDL) since 1973.