Understanding your commercial vehicle footprint — Optimizing energy use

George Survant
Senior Director of Fleet Relations

Chris Lyon
Director of Fleet Relations

This article was published in the March 2020 edition of NTEA News.

Fleet professionals may tend to think of vehicles as transportation devices, mobile tools and — in our connected world — data sources. There is, however, a need to evolve this view — visualizing vehicles as energy users. Energy Information Administration (EIA) states: “Only about 12–30% of the energy from the fuel you put in a conventional vehicle is used to move it down the road, depending on the drive cycle. The rest of the energy is lost to engine and driveline inefficiencies or used to power accessories. Therefore, the potential to improve fuel efficiency with advanced technologies is enormous.” (See fueleconomy.gov/feg/atv.shtml for details).

A large part of many fleet operating budgets is focused on fuel (and energy consumption). Large vocational trucks, by nature, can consume tremendous amounts of energy — both in transit and on the worksite. As with any commodity, energy comes with a price tag, and to lower this expense, there are two available options — use less energy and/or reduce cost of energy consumed.

Consuming less energy
Decreasing energy consumption can be both direct and indirect. In the commercial vehicle world, direct energy savings come from the main powerplant, and indirect stem from working more efficiently (in some cases, independent from the main vehicle powerplant). Types of direct energy reduction include shifting workloads from the main powerplant (i.e., PTO-driven operations from the engine) to stored energy or more efficient sources.

Shifting from the main powerplant can be done with devices like auxiliary power units. These are commonly seen on refrigerated loads to ensure cargo stays preserved even when the truck engine is not running. Also, stored energy systems are devices that allow the truck to work on-site without the engine running. Examples include aerial lift trucks where the aerial platform and tools are operating on stored electricity without an engine running.

In other applications, launch assist devices can help reduce the need for bigger engines for peak power demand created from overcoming a truck’s standing inertia. These are often stored energy devices from batteries and, occasionally, hydraulic reservoirs.

Idle management systems are also an important solution to lowering energy demand. These systems create savings by shortening engine run time. This has become an increasingly common solution in passenger cars and light trucks as the engine stops when the vehicle is not underway. With engine start response times in the milliseconds, an idle management system is a viable way to stop burning unneeded fuel, such as in congested traffic situations. In NTEA’s 2020 Fleet Purchasing Outlook (ntea.com/fpo), fleets shared how they view opportunities to decrease fuel intake. Latest survey results show idle management technology taking top priority (see Figure 1).

Driving lighter vehicles is another way to consume less energy. While payload may not be directly actionable due to mission and consumer location restrictions, vehicle weight can be (1–3% fuel economy improvement per 5% weight reduction; fuel cost savings are estimated assuming an average vehicle lifetime of 166,000 miles).

All too often, the immediate reaction is to think lighter weight vehicles are more costly and less durable. But today’s products are significantly improved: fiberglass products (a composite material) are backed by advanced support materials rather than the plywood common in previous years. They’re designed to ensure the body remains light and, at the same time, durable and affordable to repair. The same is true for aluminum. Products used in new generation bodies are significantly stronger, while not relinquishing aluminum’s weight advantage over steel bodies. Repair techniques for aluminum are more sophisticated, and the number of competent repair centers has grown exponentially.

Virtually all OEMs are using combinations of composite (fiberglass, for example) and aluminum to reduce final vehicle weight with the result of improved vehicle fuel efficiency. To the greatest extent possible, buyers in the fleet community using state-of-the-art upfitters and vehicle modifiers should consider incorporating these leading techniques to diminish energy used in fulfilling their respective missions, while providing superior value.

Basic, well-executed fleet operation fundamentals represent another element for consideration. Examples include

  • Ensuring properly inflated tires
  • Reducing rolling resistance on components such as tires (4–7% improvement in miles per gallon; see fueleconomy.gov/feg/atv.shtml for details)
  • Scheduling thorough and timely vehicle maintenance

In addition, mapping powertrain curves to transmission shift points (reflecting use of an optimized match of engine power to mission requirements) is an excellent way to reduce energy used. Getting the correct match can net impressive energy reductions with reasonable additional cost. This technique is so effective, some suppliers in the space guarantee savings from this option (examples of 8–9% fuel economy improvement is not unusual).

You can’t afford to overlook driver behavior, which can change through coaching, for reduced energy use (10–40% improvement in miles per gallon; see fueleconomy.gov/feg/atv.shtml for details). Aggressive acceleration and harsh braking not only harm fuel economy and increase unnecessary wear but also elevate risk for a crash event. Providing drivers with real-time performance feedback and positive reinforcement can significantly influence behavior.

Paying less for energy
Petroleum fuel costs are notoriously volatile and, sometimes, not weighted carefully against the potential effect on world supply. Beyond representing a significant portion of fleet budgets, the volatility alone can create problems in companies that would see internal cash and profitability effects from unanticipated fuel price increases.

One advantage of shifting to nontraditional fuel sources is the significant boost in cost stability.  

According to EIA, in addition to cost stability, cost per GGE of propane, CNG and electricity is significantly lower than gasoline or diesel. Issues with these cheaper alternatives are twofold. First, vehicles are more expensive to acquire and can bring less in the resale market, depending on regional refueling infrastructure and mandatory compliance issues. An even greater challenge is refueling infrastructure. Currently, selecting one of these alternatives is highly dependent on mission and availability of refueling options.

When there’s a selection of alternative fuels, fixed, predictable-route fleets dispatched from a central location are an ideal choice. As with any vehicle decision, a thorough life cycle cost analysis (considering all costs with an accurate forecasted resale value) can validate alternative fuel sources as a good investment for a fleet.

Where does the energy go?
Looking at actual energy put into vehicles as compared to what’s coming out can be an important factor. Conventional gasoline combustion energy only utilizes 12–30% of energy from the fuel to power wheels on the road. Where does the energy go? Much of it is transformed into heat, mechanical loss and sound — essentially not used to propel the vehicle.

Hybrid vehicles, as compared to internal gasoline vehicles, capture 21–40% of the energy from fuel consumed.

Finally, electric cars can run at about a 72–94% efficiency level. Currently, only electric, electric hybrids and certain hydraulic systems reclaim kinetic energy during braking, returning a portion of energy used in the process.

Finding the right technology
Start with a deliberate discussion of work mission with the fleet user. Beginning with the main powerplant, evaluate all options to determine any savings opportunities with an alternative fuel choice. You may want to perform a formal drive and duty cycle analysis to map potential cost reduction opportunities.

Drive cycle defines how vehicles operate based on

  • Average speed
  • Amount of incidental idling time
  • Power export time (PTO operation, etc.)
  • Number of starts and stops per cycle
  • Longest average continuous running time per cycle

Duty cycle defines how much a vehicle is used and looks at

  • Length of average operating cycle
  • Number of operating cycles per period
  • Total miles driven per measurement period
  • Percentage of loaded versus empty operation
  • Percentage of on-road versus off-road operation

Next, evaluate if there’s a technique for lessening dependence on the main powerplant that can be effectively deployed in the fleet.

These initial steps refer to additions to a fleet and replacement of existing equipment. There are some applications where a retrofit may be a practical choice, but it can be challenging to justify such costs given remaining life of the vehicle in question.

Properly managing idling
Evaluating high-idle vehicles is an important consideration. Begin by defining why and where the vehicle is idling. In vocational settings, idling can be defined in two categories: during the work event and not directly supporting the work event. Examples of supporting work cycle events include PTO activities (where mechanical energy is drawn from the main powerplant). Unnecessary idling occurs when no work is being performed, which can be considered wasted energy. Driver behavior or advanced idle shutdown technology can be utilized to limit unnecessary idling. Mitigating unnecessary idling and managing essential idling can be an avenue for cost savings. Usage data can make the case for no engine-on activity (work from stored energy) or partial engine support (using a combination of stored and mechanical energy).

One new challenge for fleet operators is created by the need to clean the exhaust system, eliminating unwanted and harmful emissions. Reducing emissions via diesel particulate filter (DPF) and selective catalytic reduction systems requires a maintenance cycle commonly referred to as the regen cycle that flushes the exhaust stream of accumulated ash and soot. Fleets in the high-idle category should consider this. As the regen cycle is automatically initiated by the engine control system at a specific temperature and runtime, an engine at idle often does not produce high enough exhaust gas temperature to trigger the automated regen cycle.

Vehicles driven on the highway often achieve proper conditions to trigger an automatic passive regeneration of the DPF. In circumstances where urban and high-idle vehicle activities do not achieve suitable trigger conditions, these engines require manual regeneration. Failure to properly maintain the DPF can result in reduced performance and automatic engine power derating. Manual regeneration can be time consuming, causing lost productivity. Lessening fuel burned will decrease frequency of required regenerations. Understanding idling implications is an important factor in the process of making an alternative fuel decision.

Beyond the battery
Many arguments can be made for and against vehicle electrification. One of the most visible is vehicle battery end of life. In June 2018, Bloomberg News reported the first cycle of electric batteries was reaching retirement. Some think, much like an end-of-life vehicle, they are scrapped, with parts being recycled and going to a landfill. However, there can be a secondary market for lithium ion vehicle batteries. While no longer optimal for the vehicle segment, they continue to have a viable use in the marketplace. The secondary life can extend another seven to 10 years, providing grid management or even electric vehicle charging.

Telematics improvement opportunities
There are three significant impacts of telematics in fleet management. It can help optimize route management and dispatching; track and provide fleet operators with information used to improve maintenance programs; and offer insight into safe driving behavior. When integrated with a fleet management system, captured data can improve decision-making regarding vehicle life cycles, reliability and serviceability. Optimizing these last elements will improve operator productivity and, ultimately, the entire fleet’s value proposition.

Telematics data is valuable but can be overwhelming — despite having the support and resources of suppliers. Integrating data with intelligence gathered from experience and user input can be challenging for those without an analytics background. Green Truck Association’s data logger drive and duty cycle analysis program collects operating metrics and provides fleet and industry information on how vehicles operate in varying environments. The analysis program allows for benchmarking against other options and technologies available in today’s market. It can help you integrate data into your reference experience and operating conditions and develop optimal operating solutions to fit your needs. This opportunity is available at no cost to all GTA fleet members (except for return shipping of the dataloggers). Learn more at greentruckassociation.com/datalogger.

Putting it all together
Effective fleet operation in this generation of sophisticated operating elements (i.e., engaged drivers; technologically advanced fleet products; and ability to make near real-time, data-driven decisions) has become significantly more complex. Reducing impact and adjusting energy choices require multiple levels of investment (based on which fuel source is right for a fleet); ability to perform an in-depth examination of what’s available in the market and how relevant those choices are to a fleet; careful analysis and weighting of relevant data sources to reveal critical decision junctures; and strong fundamental fleet operations.

The good news is many of these options can be applied concurrently: improving driver behavior will enhance any design choices made in constructing fleet vehicles, for example. Some choices are evolutionary — great candidates for an existing fleet (optimizing engine power to shift points and idle revolutions per minute), while some are only available in the replacement/growth cycle. Built-in safety features like lane departure and anti-collision devices are becoming readily available to vocational fleets. Driver comfort and ease of operation are now the standard. It’s exciting to see where we’ve come in recent decades, and there’s no doubt the fleet community will continue to focus on being good stewards of available resources.

NTEA regularly publishes articles as part of our efforts to provide industry professionals with information on multi-stage commercial vehicle regulations, safety and efficiency. For more information, visit ntea.com/whitepapers.