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Good Prospects for Greener Heavy Trucks

Trucks handle more than two-thirds of all freight in the United States. And “heavy” trucks—those designated as Class 8—consume 28 billion gallons of fuel per year. Trucks in Class 8A average about 6 miles/gallon, a number that has hardly changed in decades. The first-ever mpg standards for medium and heavy trucks were introduced in 2011, effective with the 2014 model year, requiring a 20% reduction in fuel consumption. Since fuel is the second-largest expense for trucking companies, the industry has supported the new standards—and truck sales surged last year to gain the savings from the new, more fuel-efficient vehicles.

In June 2015, the EPA and DOT announced Phase 2 truck fuel economy standards, which will apply to trucks built between 2021 and 2027. They will require another 24% reduction in fuel consumption compared to 2018 levels. You may be surprised to learn that the leading trucking organization—the American Trucking Associations—generally supports the phase 2 standards. ATA’s news release in response to the Phase 2 announcement noted that ATA has adopted 15 “guiding principles” for Phase 2, and that the new proposal “appears to meet 14 of those.” ATA also pointed out that the industry spent $150 billion on diesel fuel last year. EPA estimates that over the useful life of the trucks affected by the new rules, their total fuel savings will be $170 billion, accompanied by a reduction in greenhouse gases of one billion metric tons.

The big question is whether the technology will exist to achieve the Phase 2 goals at an affordable cost. And the good news is that many engineers and trucking experts think this will be do-able. The low-hanging fruit is further reductions in aerodynamic drag from additional streamlining—such as replacing huge side mirrors with rear-facing video cameras. Michelin and other tire companies argue that replacing narrow twin tires with single wide tires can reduce rolling resistance (and weight), gaining up to 10% fuel savings.

But the bigger (and possibly more costly) gains could come from propulsion system changes. Thanks in part to the fracking boom, there is a small but rapid movement toward propane use for delivery trucks, such as those of UPS. Propane these days costs less than half as much as diesel and is cleaner-burning than gasoline or diesel. But like liquefied and condensed natural gas (LNG and CNG), propane lacks nationwide refueling infrastructure, so is limited to local fleets that can be refueled from a central depot.

For Class 8 big-rigs, an intriguing possibility is hybrid diesel-electric propulsion. A Kentucky-based start-up called ePower Engine Systems has developed a power train that can be retrofitted into existing Class 8 tractors. Basically, it adopts the model long used by diesel locomotives (which are actually diesel-electrics). The diesel engine drives a generator that powers electric motors, in what is called a “series hybrid” configuration. The company uses a much smaller diesel engine than a conventional Class 8—a 6.7 liter diesel mated to a 150 KW generator. That delivers normal performance on level terrain. For climbing grades—which requires hugely more power for a 55,000 lb. Class 8A rig—this is supplemented by a battery pack that adds another 120 KW, only when needed to accelerate or climb grades. The batteries recharge from surplus generator power, downhill grades, and braking. Testing done by ePowershows that its overall system is 40-60% more efficient than a conventional diesel that meets current Phase I standards. The company also claims that their drivetrain will repay its price premium in 30 months and return a $90K profit over five years. I am in no position to verify their figures, but am presenting this information as an illustration of what may well be possible via improved propulsion technology.

In short, very real progress may be in store for large trucks, reducing their fuel use and greenhouse gas emissions, at what is likely to be an affordable cost. This looks to me like a win-win situation in the making.

(This article first ran in September’s issue of Surface Transportation Innovations)

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