The benefits of high-efficiency, flexible-fuel engines for heavy-duty trucking

The California Air Resources Board has adopted a regularisation that requires motortruck and motor manufacturers to trim the nitrogen oxide (NO_x) emissions from caller heavy-duty trucks by 90 percent starting successful 2027. NO_x from heavy-duty trucks is 1 of the main sources of aerial pollution, creating smog and threatening respiratory health. This regularisation requires the largest aerial contamination cuts successful California successful much than a decade. How tin manufacturers execute this assertive extremity efficiently and affordably?

Daniel Cohn, a probe idiosyncratic astatine the MIT Energy Initiative, and Leslie Bromberg, a main probe idiosyncratic astatine the MIT Plasma Science and Fusion Center, person been moving connected a high-efficiency, gasoline-ethanol motor that is cleaner and much cost-effective than existing diesel motor technologies. Here, Cohn explains the flexible-fuel motor attack and wherefore it whitethorn beryllium the astir realistic solution—in the adjacent term—to assistance California conscionable its stringent conveyance emanation simplification goals. The probe was sponsored by the Arthur Samberg MIT Energy Innovation fund.

Q. How does your high-efficiency, flexible-fuel gasoline motor exertion work?

A. Our extremity is to supply an affordable solution for heavy-duty conveyance (HDV) engines to emit debased levels of nitrogen oxide (NO_x) emissions that would conscionable California's NO_x regulations, portion besides quick-starting gasoline-consumption reductions successful a important fraction of the HDV fleet.

Presently, ample trucks and different HDVs mostly usage diesel engines. The main crushed for this is due to the fact that of their precocious efficiency, which reduces substance cost—a cardinal origin for commercialized trucks (especially long-haul trucks) due to the fact that of the ample fig of miles that are driven. However, the NO_x emissions from these diesel-powered vehicles are astir 10 times greater than those from spark-ignition engines powered by gasoline oregon ethanol.

Spark-ignition gasoline engines are chiefly utilized successful cars and airy trucks (light-duty vehicles), which employment a three-way catalyst exhaust attraction strategy (generally referred to arsenic a catalytic converter) that reduces conveyance NO_x emissions by astatine slightest 98 percent and astatine a humble cost. The usage of this highly effectual exhaust attraction strategy is enabled by the capableness of spark-ignition engines to beryllium operated astatine a stoichiometric air/fuel ratio (where the magnitude of aerial matches what is needed for implicit combustion of the fuel).

Diesel engines bash not run with stoichiometric air/fuel ratios, making it overmuch much hard to trim NO_x emissions. Their state-of-the-art exhaust attraction strategy is overmuch much analyzable and costly than catalytic converters, and adjacent with it, vehicles nutrient NO_x emissions astir 10 times higher than spark-ignition motor vehicles. Consequently, it is precise challenging for diesel engines to further trim their NO_x emissions to conscionable the caller California regulations.

Our attack uses spark-ignition engines that tin beryllium powered by gasoline, ethanol, oregon mixtures of gasoline and ethanol arsenic a substitute for diesel engines successful HDVs. Gasoline has the charismatic diagnostic of being wide disposable and having a comparable oregon little outgo than diesel fuel. In addition, presently disposable ethanol successful the U.S. produces up to 40 percent little greenhouse state (GHG) emissions than diesel substance oregon gasoline and has a wide disposable organisation system.

To marque gasoline- and/or ethanol-powered spark-ignition motor HDVs charismatic for wide HDV applications, we developed ways to marque spark-ignition engines much efficient, truthful their substance costs are much palatable to owners of heavy-duty trucks. Our attack provides diesel-like precocious ratio and high power successful gasoline-powered engines by utilizing assorted methods to forestall motor sound (unwanted self-ignition that tin harm the engine) successful spark-ignition gasoline engines. This enables greater levels of turbocharging and usage of higher motor compression ratios. These features supply precocious efficiency, comparable to that provided by diesel engines. Plus, erstwhile the motor is powered by ethanol, the required sound absorption is provided by the intrinsic precocious sound absorption of the substance itself.

Q. What are the large challenges to implementing your exertion successful California?

A. California has ever been the pioneer successful aerial pollutant control, with states specified arsenic Washington, Oregon, and New York often pursuing suit. As the astir populous state, California has a batch of sway—it's a trendsetter. What happens successful California has an interaction connected the remainder of the United States.

The main situation to implementation of our exertion is the statement that a amended interior combustion motor exertion is not needed due to the fact that battery-powered HDVs—particularly long-haul trucks—can play the required relation successful reducing NO_x and GHG emissions by 2035. We deliberation that important marketplace penetration of artillery electrical vehicles (BEV) successful this conveyance assemblage volition instrumentality a considerably longer time. In opposition to light-duty vehicles, determination has been precise small penetration of artillery powerfulness into the HDV fleet, particularly successful long-haul trucks, which are the largest users of diesel fuel. One crushed for this is that long-haul trucks utilizing artillery powerfulness look the situation of reduced cargo capableness owed to important artillery weight. Another situation is the substantially longer charging clip for BEVs compared to that of astir contiguous HDVs.

Hydrogen-powered trucks utilizing substance cells person besides been projected arsenic an alternate to BEV trucks, which mightiness bounds involvement successful adopting improved interior combustion engines. However, hydrogen-powered trucks look the formidable challenges of producing zero GHG hydrogen astatine affordable cost, arsenic good arsenic the outgo of retention and proscription of hydrogen. At contiguous the precocious purity hydrogen needed for substance cells is mostly precise expensive.

Q. How does your thought comparison wide to battery-powered and hydrogen-powered HDVs? And however volition you transportation radical that it is an charismatic pathway to follow?

A. Our plan uses existing propulsion systems and tin run connected existing liquid fuels, and for these reasons, successful the adjacent term, it volition beryllium economically charismatic to the operators of long-haul trucks. In fact, it tin adjacent beryllium a lower-cost enactment than diesel powerfulness due to the fact that of the importantly less-expensive exhaust attraction and smaller-size engines for the aforesaid powerfulness and torque. This economical attractiveness could alteration the large-scale marketplace penetration that is needed to person a important interaction connected reducing aerial pollution. Alternatively, we deliberation it could instrumentality astatine slightest 20 years longer for BEVs oregon hydrogen-powered vehicles to get the aforesaid level of marketplace penetration.

Our attack besides uses existing corn-based ethanol, which tin supply a greater near-term GHG simplification payment than battery- oregon hydrogen-powered long-haul trucks. While the GHG simplification from utilizing existing ethanol would initially beryllium successful the 20 percent to 40 percent range, the standard astatine which the marketplace is penetrated successful the near-term could beryllium overmuch greater than for BEV oregon hydrogen-powered conveyance technology. The wide interaction successful reducing GHGs could beryllium considerably greater.

Moreover, we spot a migration way beyond 2030 wherever further reductions successful GHG emissions from maize ethanol tin beryllium imaginable done c seizure and sequestration of the c dioxide (CO₂) that is produced during ethanol production. In this case, wide CO₂ reductions could perchance beryllium 80 percent oregon more. Technologies for producing ethanol (and methanol, different intoxicant fuel) from discarded astatine charismatic costs are emerging, and tin supply substance with zero oregon antagonistic GHG emissions. One pathway for providing a antagonistic GHG interaction is done uncovering alternatives to landfilling for discarded disposal, arsenic this method leads to potent methane GHG emissions. A antagonistic GHG interaction could besides beryllium obtained by converting biomass discarded into cleanable fuel, since the biomass discarded tin beryllium c neutral and CO₂ from the accumulation of the cleanable substance tin beryllium captured and sequestered.

In addition, our flex-fuel engine exertion whitethorn beryllium synergistically utilized arsenic scope extenders successful plug-in hybrid HDVs, which usage constricted artillery capableness and obviates the cargo capableness simplification and fueling disadvantages of long-haul trucks powered by artillery alone.

With the increasing threats from aerial contamination and planetary warming, our HDV solution is an progressively important enactment for near-term simplification of aerial contamination and offers a faster commencement successful reducing heavy-duty fleet GHG emissions. It besides provides an charismatic migration way for longer-term, larger GHG reductions from the HDV sector.

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