Big rigs are big polluters. With 21 million operating globally, heavy-duty trucks account for about a third of all carbon emissions from the transportation sector. If left unchecked, emissions from semi-trucks could more than double by 2050. But while manufacturers of passenger cars and light-duty delivery trucks are trading internal combustion engines for electric ones, it’s not as easy to make that change to long-haul trucks. The biggest challenge? Range.
The problem: Getting electric trucks to go farther
Electric 18-wheelers can’t go the distance. California-based Tesla has two models that get 300 and 600 miles to a charge. Germany-based Daimler has one that goes 250 miles. But nearly a fifth of all freight in the United States travels 500 miles or more, and almost half of that travels 1,000 miles, according to the U.S. Department of Transportation. What trucker has time to sit and wait hours for the batteries to recharge? More batteries would supply more range, but would take up a lot of space, says Andreas Thon, vice president of rail electrification at Siemens Mobility in Portland, Oregon. “You would have so much battery on your truck, you wouldn’t have space for your freight,” Thon says.
Electric semi-trucks would also need a network of chargers. If they existed, charging the batteries would take several hours, increasing labor costs. Siemens Mobility has been testing out a more radical solution. Borrowing a decades-old technology from the train industry and adapting it for roads, they say, could pay huge dividends — and alter highway driving as we know it.
The solution: catenary lines
Why not electrify trucks the same way as trains, with wires strung above the road? These systems have proven to be far more efficient than diesel trains, have lower emissions and operating costs, and are quieter and more powerful. “It’s a copy and paste from rail technology,” says Thon.
The system is familiar to anyone who has seen a trolley on a city street. A network of poles and overhead wires, called catenary lines, occupies the right lane of a highway.
Siemens Mobility, which built the first electric rail in 1879, began making electrified trucks in the early 2010s. Today the company has two six-mile (10-km) electrified highways — which it calls “eHighways” — in Germany, with another five six-mile (10-km) stretches coming online later this year.
The system is familiar to anyone who has seen a trolley on a city street. A network of poles and overhead wires, called catenary lines, occupies the right lane of a highway. A truck — fully electric, a diesel-hybrid, or a natural-gas-hybrid — taps into the wires with a movable rooftop contraption called a pantograph. Shaped like a T, the pantograph automatically raises to contact the wires and lowers when the driver changes lanes. A guard rail protects the poles and wires from toppling in the event of a crash. Not only do the wires run the truck, they charge its onboard battery, which powers its engine when it’s not connected to the wires.
Thon, who drove an electric test rig on a demonstration track in Germany, says long-haul drivers of electric trucks need no additional training and will experience a smooth, quiet ride. “You’ll hear the wind more than the engine,” he says. Preliminary surveys from drivers of passenger cars that have shared the highway with electrified trucks show no surprises. Once introduced to the system, drivers have adapted quickly, says Thon.
The challenge: cost and commitment
Upfront costs to build the electrified highway infrastructure could be as high as building out an electrified rail system — about a few million dollars per mile. That could turn away members of the trucking industry as well as lawmakers. But the savings over the long haul would be significant. One 40-ton truck could save about $17,500 a year on fuel alone. If 10 percent of the world’s heavy-duty truck freight ran on an electric highway with power generated by low-carbon electricity, the sector could save 100 million tons of CO2 per year.
If complaints about the aesthetics of wind turbines and solar panels are any indication of America’s reaction to renewal energy solutions, interstate highways strung with wires may not garner wide appeal. But there are efforts in the electric train sector to streamline catenary networks. The Royal Institute of British Architects ran a competition in 2014 to promote innovations in catenary design, with beautiful results. And some cities with light rail lines are replacing overhead electric wires with ground-level power supplies that energize only when the train passes over. Those innovations could end up translating to electrified trucking.
The big picture
In an ideal climate-friendly economy, semi-trucks would have all-electric engines, powered by electricity that’s generated by renewable energy. Those days are decades away. In the short term, turning a portion of the world’s roads into electrified highways could offer a feasible, partial solution. “It would provide an important energy backbone for future, zero-emission big rigs,” says Thon.