Researchers at MIT have conceived of a new way of powering heavy-duty trucks that is both eco-friendly and efficient. The method would use a plug-in hybrid engine system and a spark ignition engine instead of a diesel one.
A spark ignition
“We’ve been working for a number of years on ways to make engines for cars and trucks cleaner and more efficient, and we’ve been particularly interested in what you can do with spark ignition [as opposed to the compression ignition used in diesels], because it’s intrinsically much cleaner,” said MIT Energy Initiative and Plasma Fusion and Science Center research scientist Daniel Cohn.
A gasoline-powered vehicle produces only a tenth as much nitrogen oxide (NOx) pollution than a diesel engine vehicle. Furthermore, if pure methanol or ethanol from renewable sources are used the net greenhouse gas emissions could even account for zero.
“It’s a way of making use of a low-greenhouse-gas fuel” when it’s available, “but always having the option of running it with gasoline” to ensure maximum flexibility, Cohn explained.
Cohn believes his hybrid truck concept is a practical alternative to Tesla's plans for an all-electric heavy-duty truck. “We think that’s going to be very challenging, because of the cost and weight of the batteries” needed to provide sufficient range.
Cohn and principal research engineer Leslie Bromberg estimate it would take between 10 and 15 tons of batteries to meet the expected driving range of diesel trucks. Instead, the researchers propose what they call "a plug-in hybrid.”
In terms of pricing, Bromberg argues that gasoline engines are now cost-competitive with diesel ones as the price of diesel has gone up. “Over time, gas engines have become more and more efficient, and they have an inherent advantage in producing less air pollution,” he said.
Bromberg also points out that California has plans for new regulations on truck emissions that are very difficult to meet with diesel engine vehicles. “We think there’s a significant rationale for trucking companies to go to gasoline or flexible fuel,” Cohn said.
“The engines are cheaper, exhaust treatment systems are cheaper, and it’s a way to ensure that they can meet the expected regulations. And combining that with electric propulsion in a hybrid system, given an ever-cleaner electric grid, can further reduce emissions and pollution from the trucking sector.”
Of course, Cohn states that all-electric vehicles are the optimum goal. However, he argues that today's batteries cannot realistically provide that yet.
Instead, the hybrid they suggest can work efficiently and address many of the concerns surrounding heavy-duty trucks.
"We don’t know which is going to be stronger, the desire to reduce greenhouse gases, or the desire to reduce air pollution.” Luckily, argues Cohn, their solution tackles both.