Some time back, a press release from the Diesel Technology Forum touted the latest figures on “clean diesel” trucks being put into operation. And the news was good, indeed: according to the report, “clean diesel” engines are in 30 percent of commercial vehicles on the road today, up from 25.7 percent last year. The numbers used class 3-8 vehicles, or those with a gross vehicle weight rating 10,001 — 80,000 pounds. That’s quite a range, certainly, and includes trucks at the lower end that might be considered personal vehicles in some cases.
What does “clean diesel” mean? This term, as the Forum defines it, starts with those engines that support ultra-low sulfur fuels, which have been mandated for a decade now. The fuel changeover was a catalyst for further technologies to improve emissions. Essentially, “clean diesel” trucks are those that meet or exceed the U.S. government standards mandated in 2011, or more simply put, vehicles that are model year 2011 or newer. As the Forum states,
With the introduction of lower-sulfur diesel fuel, came the ability to use a number of exhaust after-treatment options, such as diesel particulate filters (DPF), exhaustgas recirculation (EGR), diesel oxidation catalysts (DOC), and selective catalystreduction (SCR) with the use of diesel exhaust fluid (DEF) that can be sensitive to the sulfur levels in the fuel.
These advancements have led to great reductions in NOx and particulate emissions, and are likely to increase quality of life in urban areas in particular.
Despite this news coverage, growth in clean diesel trucks is a natural outcome of the already established change in fuels, regulatory mandates, and the slow churn of shippers all over the country updating to newer commercial trucks as current trucks outlive their useful lifespan. It’s a good thing, but hardly the most exciting development in truck technology.
What is far more interesting are the current and upcoming combinations of factors which stand poised to create real breakthroughs in efficiency for commercial fleets. These include improved aerodynamics and vehicle add-ons, further engine improvements, the promise of alternative fuels, and finally, the advancement of automated driving technologies.
Streamlined Trucks: Improved Aerodynamics
At speed, aerodynamic drag accounts for much of fuel consumption by commercial trucks. Moving thousands of pounds of goods is hard work for an engine. Accordingly, each small improvement in truck and trailer aerodynamics stands to make a large difference over the 125,000+ miles driven annually by many commercial vehicles. It may be years before regulations in the U.S. allow replacement of side mirrors on commercial trucks with cameras to reduce drag, but other improvements may be a near-term reality.
In particular, the addition of trailer skirts and boat tail fairings can together reduce aerodynamic drag 25 percent, according to research from Lawrence Livermore National Laboratory. The trailer tails by themselves can increase fuel savings by more than 5 percent, and trailer skirts by up to 4 percent, individually. Other aerodynamic kits, such as cab wheel skirts and nose cones, offer savings as well. A change to wider tires from two-tire configurations can create another 10 percent gain, with additional efficiencies from tire pressure monitoring and auto-inflation systems. Of course, vehicle speed is also a major factor, as speeds above 60 miles per hour generally reduce fuel efficiency. In the end, every 2 percent reduction in drag can improve fuel efficiency by 1 percent or more.
Efforts, such as the Run on Less project, sponsored by the North American Council for Freight Efficiency, prove that even with today’s technology and changes in driver behavior, it is possible to achieve average fuel efficiency of 9 miles per gallon or more.
Driving Efficiency Into the Next Decade
Today, diesel trucks are 16 percent more efficient than they were just five years ago, and the industry continues to improve at a rate of about 3 percent per year. With the start date of EPA’s phase two greenhouse gas emissions regulations rapidly approaching, manufacturers are keen to continue improvements in fuel efficiency and, in conjunction, emissions. As they head for the 25 percent in total gains that need to be achieved by 2027 — EPA sets targets for tractor, trailer, and engine manufacturers separately — many are introducing new technologies one to two model years ahead of schedule. This is a promising development for fuel efficiency, but it will come with near-term cost increases as the up-front costs are estimated to total thousands of dollars per new truck purchased. These improvements are meant to “lower CO2 emissions by approximately 1 billion metric tons, cut fuel costs by about $170 billion, and reduce oil consumption by up to 1.8 billion barrels over the lifetime of the vehicles sold.” It is possible that the current administration in Washington may slow the adoption of these regulations, but the corresponding improvements will likely occur regardless.
In terms of performance and energy density, there still isn’t much competition for diesel fuel. That said, fleet owners would be wise to take a close look at current and future options for alternative fuel deployment. Compressed natural gas, or CNG, has garnered particular interest, with some companies spending millions to switch. CNG is generally available at a lower commercial cost per gallon than diesel, but comes at a 10 to 15 percent degradation of fuel efficiency. Other considerations of greenhouse gas emissions regulations, supply availability, and economics can vary by state or region, so a targeted CNG strategy is the best approach. Nevertheless, this alternative fuel plays an important role in many supply chain strategies, and renewable natural gas (RNG) has a promising future ahead of it as well, in terms of both cost and emissions.
A more cost-effective alternative fuel option may be a renewable like biodiesel, which can often be procured at or below diesel pricing, and comes with little or no requirement to convert trucks over to use. Furthermore, biodiesel is likely used in your supply chain already, as multiple states mandate its use in low level blends with conventional diesel.
None of these alternative fuels is considered in the expected gains above, but they will contribute to a more sustainable future.
Electric and hybrid-electric heavy trucks are also on the horizon, with a battle now heating up between Cummins and market disruptors such as Tesla and others. Cummins in particular announced a 100-mile range electric-powered class 7 heavy tractor in late August in an effort to pre-empt Tesla’s slated release of its own model. Tesla’s heavily touted all-electric heavy duty truck is said to have double or triple the range of the Cummins demonstration model. Mercedes-Benz, Toyota, Volvo, and other manufacturers are also investing in research for electric heavy trucks, mainly for shorter route fleets.
An article in a truck industry publication earlier this year quoted IHS Markit saying, “Heavy batteries and limited range at this point make some trucking applications more suited to electric power than others. Expect to see electric trucks first in urban areas on routes where they make regular deliveries or for vehicles with a similar drive cycle profile such as garbage trucks and street sweepers.”
It remains to be seen how quickly full-electric commercial trucks in heavier class ranges will move from concept to on-the-road reality. Yet, as of today, most manufacturers are readying models for purchase in the next five years.
Nearly all conversions or wholesale changeovers to an alternative fuel or electric power, with the possible exception of biodiesel, will come with major investment costs and should be weighed carefully against fuel efficiency, fuel costs, range limitations, and other factors.
Automated Driving and Platooning
Driving technique is a major factor in truck fuel efficiency. An American Trucking Associations study found up to a 35 percent difference in fuel economy between drivers depending on their skill level and attention to driving efficiently. In fact, gains from driving with fuel savings in mind can lead to as large or larger savings than the aerodynamic add-ons mentioned earlier. The American Transportation Research Institute reported:
Studies from other countries have demonstrated that driver training can benefit carriers by increasing fuel efficiency and reducing costs. For example, a study conducted by the European Commission found that a one-day driver training course could result in a fuel efficiency increase of five percent. In addition, Canadian researchers found that for combination truck drivers, training and driver monitoring could result in a 10 percent fuel efficiency increase.
While in the near term, an emphasis on driver training programs, measurement, and reminders to “drive green” can improve overall fleet efficiency, the future of commercial truck operation is likely to be a combination of automated and semi-automated systems. A myriad of companies are working to develop systems that will someday “drive” both commercial and personal vehicles autonomously or with minimal human intervention. Full automation of commercial trucks could take decades, but recent steps taken by manufacturers to test automation indicate that there will be many incremental advances as the industry progresses across the spectrum of autonomy.
In the near term, semi-automated and connected vehicle technologies hold promise. Advancements such as Peloton’s platooning technology, which joins two trucks together in a pre-planned or ad hoc fashion to draft, increasing fuel economy for both, can increase fuel efficiency by 7 percent or more. Because they react more quickly to changing road conditions, computer-aided assists like these can enable drafting much more safely than human operators.
As a principle, the least expensive and lowest-emission gallon of fuel is the one that doesn’t get used. With that in mind, it is important for fleet owners and operators to take an active role in fuel management. Whether that means optimizing the purchase of fuel at the lowest cost possible over each freight movement or maximizing use of intermodal, data is key. It is no longer adequate to simply rely on the DOE Index and an inherited MPG benchmark to estimate fuel costs. Instead, logistics organizations and shippers should take advantage of methods that harness data to determine their actual costs, and transition to these from simple surcharges.
A Bright Future for Trucking
Together, the technological advancements mentioned above are a huge story. Each incremental improvement we are seeing adds up to meaningful gains in fuel economy and corresponding drops in emissions output by commercial trucks. It is vitally important for both carriers and shippers to see the benefits of moving to these more efficient fleets. With the critical step of shippers and carriers working together to invest in new fleet technologies, both will be able to maximize profitability while meeting or surpassing their sustainability goals. And, with the rise of even more promising advancements in the next decade, we are headed towards a bright future for trucking and logistics.
Enjoy curated articles directly to your inbox.