Six Steps for Managing a Fleet's Energy Budget
Because a typical vocational fleet spends a large portion of its total operating budget on energy or fuel, fleet managers are always looking for ways to reduce energy costs.
By Christopher Lyon
Because a typical vocational fleet spends a large portion of its total operating budget on energy or fuel, fleet managers are always looking for ways to reduce energy costs. There are only two methods for doing this: consuming less of the energy currently being used or switching to a lower-cost energy source. While this sounds cut and dried, the actual implementation can be complex because of the nearly limitless configurations and designed mission capabilities of work trucks.
First, most fleets have to maintain service during any conversion process. They also may have to figure out how to relocate vehicles on an emergency, short-term or permanent basis. Funding is another important consideration. Depending on how a fleet approaches energy cost reduction, it could require significant capital expenditures, one-time expense payouts, and/or ongoing supplemental maintenance and operating costs. Assuming required funding is available, the fleet manager might need to prove an acceptable return on investment (ROI) within a reasonable payback period.
This article outlines six steps fleet managers can take to determine the best ways to maximize their fleets’ energy budgets.
1. Analyze Drive and Duty Cycles
Most of the processes and technologies for reducing fleet energy costs are sensitive to drive and duty cycles. While these terms are often used interchangeably, they are separate measurements of how a fleet operates.
A drive cycle defines how vehicles operate based on factors such as:
- Average speed;
- Amount of incidental idling time;
- Power export time (PTO operation, etc.);
- Number of starts and stops per cycle; and
- Longest average continuous running time per cycle.
A duty cycle defines how much a vehicle is used and looks at factors such as:
- Length of average operating cycle,
- Number of operating cycles per period,
- Total miles driven per measurement period,
- Percentage of loaded vs. empty operation, and
- Percentage of on-road vs. off-road operation.
Because the effectiveness of energy reduction technologies is generally closely related to a fleet’s drive cycles, fleet managers can use drive cycle data to identify technologies that could reduce their energy budgets. They can then use duty cycle data to determine if the projected savings associated with an alternative are adequate to cover the investment and provide the desired ROI. Remember, a single fleet can have multiple drive and duty cycles, so one approach to energy cost reduction might not work across the board. In addition, drive and duty cycles are frequently seasonally dependent, especially in areas with harsh winter weather.
A fleet, for example, may have an inner-city drive cycle with low average speeds, multiple stop/start cycles, and extended periods of incidental idle time. All of these factors are compatible with use of an electric hybrid powertrain. A duty cycle analysis, however, could show annual miles driven are so low that even doubling the current average fuel economy will not produce enough savings to cover the cost of buying the hybrid system. Because the drive cycle also documents an excessive amount of incidental idle time, a lower-cost approach for this fleet may be to implement an idle management strategy.
2. Remember the Basics
In many cases, the simplest and most economical approach to reducing energy costs is to simply consume less energy. There are several tried-and-true steps fleets can take. The simplest techniques have been recognized for so long they are often downplayed-but, when implemented properly, they can be effective. A short list of these approaches includes:
- Maintain proper tire inflation;
- Reduce vehicle weight;
- Reduce rolling resistance;
- Passive idle reduction (driver coaching, reminder signs, etc.); and
- Maintain vehicles properly.
Going beyond these somewhat passive approaches, fleet managers can take action to make new or existing vehicles more efficient. Because the powertrains of newer vehicles are computer-controlled, fleets can often re-map the engine performance curves and transmission shift points of their trucks to improve overall powertrain efficiency. When ordering new trucks, carefully choosing and matching components to specific drive and duty cycles can produce energy reductions.
3. Implement Telematics and Driver Behavior Modification
There are a number of ways to improve vehicle operational efficiency. Two approaches that provide potential are telematics and driver behavior modification. The most familiar application of telematics in the vocational fleet environment is global positioning system (GPS) functionality. This technology can have a direct impact on fleet operating costs by reducing miles driven. Going beyond this aspect of telematics, the ability to track vehicle condition in real time offers multiple possibilities for energy management. By mapping the power-train control module (PCM) to the telematics system, fleet managers can read system fault codes, tire pressures and other information. By using an exception reporting system, vehicles with defects are flagged so repairs can be made at the earliest opportunity. The data collected also can be used to develop drive cycle profiles and identify issues such as hard acceleration and braking, sudden radial maneuvers and engine idle time.
The driver can impact overall fuel economy by as much as 30 percent. The most effective behavior programs provide the driver with real-time performance feedback. Something as simple as instantaneous fuel economy feedback on the vehicle’s dash can be effective.
4. Consider Hybrid and Electrification Technology
For vocational trucks, hybrid and electrification technology can be an effective choice. It can reduce energy costs in several ways:
- Allowing the engine to operate in an optimum efficiency range,
- Recapturing kinetic energy normally lost during braking,
- Capturing surplus engine energy for use at a later time (driveline or power export),
- Facilitating engine idle management, and
- Allowing for the primary vehicle power source to be downsized.
When using hybrid vehicles, the selected technology should be matched to the drive and duty cycles. Many vocational trucks are driven a limited number of miles per day, so the efficiencies associated with full hybrid drivetrains might not justify the cost and complexity of such a system. This has resulted in the development of work-site hybrids. These vehicles use surplus engine power, stored as electric energy-sometimes supplemented by plug-in battery charging-to operate truck-mounted equipment without having to run the primary engine. This technology is much simpler than full hybrid powertrains but still provides substantial idle time reductions during stationary work-site operations. Idle management can be further enhanced by using the system to maintain cab heating and cooling (hotel loads).
5. Evaluate Lower-cost Energy Options
Fleet managers have several lower-cost energy options such as biodiesel, electricity, natural gas (CNG or LNG) and propane (autogas).
Biodiesel is generally more expensive than conventional diesel fuel; in some regulatory environments, however, it offers significant tax advantages that may result in lower total cost. In these areas, biodiesel represents a significant opportunity for fleet managers because it is basically a drop-in replacement for conventional diesel. The primary expense associated with conversion to biodiesel is cleaning fuel storage tanks before taking delivery and changing fuel filters frequently until the biodiesel has cleaned all residue out of the vehicle tanks.
Electricity is typically the lowest-cost alternative fuel available to fleets, and when the capabilities of an available vehicle fit the associated drive and duty cycles, operating cost savings are attractive. But electric trucks are limited in availability and range/speed capabilities. Upfront costs can be high because they require a large capital investment and, in some cases, significant infrastructure investments for charging systems and grid tie charges.
An alternative to pure electric trucks is the extended-range electric truck. These units use an all-electric drivetrain with a small onboard motor generator set that can provide a portion of the electric demand. This combination can offer operating ranges in excess of 250 to 300 miles before a full battery charge is required. There is a fine line between extended-range electric vehicles and series electric hybrids. If the onboard motor generator set is large enough to provide all of the truck’s power demands, it crosses over to being a hybrid.
Natural gas has the lowest cost of all the alternative internal combustion engine fuels and generates the smallest carbon footprint. These advantages are offset in some drive/duty cycle applications by both high conversion and infrastructure costs. If a fleet has access to public natural gas fueling infrastructure, or if the quantity of fuel consumed at a given location is enough to justify the infrastructure investment required for a captive facility, natural gas has the potential to generate major energy cost savings. Compressed natural gas (CNG), currently the most commonly used natural gas variant, imposes weight and space penalties on trucks, so in many cases, it may not be feasible to convert existing trucks to use CNG. Most of these weight and space issues, however, can be addressed when designing new vehicles.
Propane, also known as autogas, has the second-lowest carbon footprint of currently viable alternative fuels and is priced between natural gas and gasoline. It has the advantage of requiring the lowest infrastructure costs of any of the alternative fuels-other than electricity if major infrastructure investments are not required. It also has a much higher energy density than CNG and is stored at a lower pressure, so the tanks are lighter and cheaper. This makes it easier to convert existing vehicles and more attractive for fleets with lower volumes per fueling facility.
6. Learn More at The Work Truck Show 2016 and Green Truck Summit
All of the technologies discussed in this article will be addressed in detail during The Work Truck Show 2016 and concurrent Green Truck Summit educational sessions, and will be displayed on the show floor. The Work Truck Show, North America’s largest work truck event, is produced annually by NTEA-The Association for the Work Truck Industry. It will be held March 14, 2016, at the Indiana Convention Center in Indianapolis, Indiana. Educational programming and the Green Truck Summit begin March 1, and exhibits open March 2. For more information, visit worktruckshow.com.
About the author: Christopher Lyon is a former fleet manager and currently serves as director of fleet relations for NTEA-The Association for the Work Truck Industry.
How Do You Measure Fuel Economy?
The most common method of measuring fuel economy is in terms of miles per gallon or gallon equivalent fuel consumption. While this traditional approach works well for some drive and duty cycles, it can present a misleading picture for applications that experience extended periods of engine idle time and/or power export by means of a power takeoff. A utility construction truck, for example, may drive 20 miles or 30 miles a day, but spend six or more hours a day exporting power to operate equipment. In such a case, a 35 percent or 30 percent reduction in total fuel consumed might only generate a small increase in overall vehicle MPG rating. In applications of this nature, a fleet manager could be better served to measure fuel consumption in terms of fuel used per unit of work accomplished. This approach will help the fleet manager focus on those portions of their drive cycles where they can reduce fuel consumption.