MIT Says We're Overlooking a Near-Term Solution To Diesel Trucking Emissions (arstechnica.com)

An anonymous reader shares a report: Trucking in the US is still driven by diesel-fueled, compression-ignition (CI), internal combustion engines. Daniel Cohn and Leslie Bromberg, a pair of researchers from the Massachusetts Institute of Technology (MIT), published a paper with the Society of Automotive Engineers, suggesting that the best way forward is not to wait for all-electric or hydrogen-powered semis, but to build a plug-in hybrid electric (PHEV) truck with an internal combustion engine/generator that can burn either gasoline or renewable ethanol or methanol. Such a setup preserves the range and affordability that's expected of diesel long-haul trucks while significantly reducing the emissions associated with diesel. To boot, it's a near-term solution; no waiting for battery weight to fall or hydrogen refueling stations to be installed.

A hybrid heavy-duty system isn't a completely novel idea, though a PHEV system has yet to be widely applied and tested in long-haul heavy-duty trucking. A company called Hyliion introduced a hybrid electric-diesel truck in 2017, and San Diego uses a hybrid electric-compressed natural gas bus on its transit system, though the former still grapples with diesel emissions and the latter is not for long-haul use. But there are some distinct problems with all-electric and all-diesel trucks that a hybrid flex-fuel truck could solve. First, freight companies are looking for the cheapest way to transport goods from point A to point B, so expensive electric vehicles don't make short-term economic sense, especially if you're competing with other freight companies using cheaper diesel engines.

Comments

Well it works and it's not new

[Rosco P. Coltrane]

There's another kind of heavy diesel-electric vehicle that's been around for decades: diesel locomotives.

I keep wondering how light passenger cars got the hybrid treatment first and long-haul trucks still haven't, when the first successful experience in the field clearly pointed to the latter being the ideal candidate.

Re:Well it works and it's not new

[rv6502]

They're not hybrid in the same sense as hybrid cars.

In fact, IMHO wouldn't call them a hybrid at all: The diesel never turns the wheel directly, the electrics motors never work without the diesel engine generating electricity, there are no batteries involved in the powertrain. Power always comes from the diesel engine.

It's a diesel engine with an electric transmission.

The electric part of a diesel-electric locomotive just replaces what would be the gear box & clutch / torque converter in a car/truck.

The diesel engines generates electricity which is fed directly to electric motors that drive the wheels because no clutch or torque converter as found on trucks and cars could survive launching an entire cargo train, they'd almost instantly disintegrate/melt/explode, and the gearbox would be impractically enormous to not wear down in seconds under the torque required.

They vary the "gear ratio" (if you will) by increasing or reducing the magnetic field on the electric generator to keep the diesel engine at the same ideal RPM range while changing the effective torque/power output.

And when diesel-electric locomotive brake using the electric motors they send all that energy to huge resistor banks, not batteries, just spewing out the energy as heat.

They don't stock and reuse the braking energy like an hybrid car because no batteries could handle the amount power being dumped when braking a freight train to be even worth trying to recuperate that energy.

From TFA:

[argStyopa]

"...However, the private sector does seem to have dipped its toes in hybrid long-haul truck powertrains. In 2017, truck engine maker Cummins announced that it would be developing a 100-mile-range electric semi with a diesel generator on board that could extend the battery range to 300 miles. Last September, the company debuted a hybrid electric and diesel or natural gas powertrain called the PowerDrive. ..." ...and they haven't sold ANY because no serious freight company is willing to a) spend more than they have to on boutique technologies; b) sacrifice both weight capacity and RANGE (these have ranges of 100 miles, or 300 miles with a larger weight sacrifice). A typical truck 7mpg with 300gal tanks has a range of TWO THOUSAND miles and can be filled/turned in about 30 mins. These electric vehicles require 8 hours for full charge.

Sure perhaps some city buses or school buses will use the tech because (apparently) they don't have a bottom line to meet. But real trucking co's are already bled white by new rest hours, requirements to buy new eco-trucks (making the used sale value of their old units plummet), idling units, and a lack of drivers. It's not like there's a surplus of wealth in the business.

And trust me, you don't want to see the cumulative impact of even a 15% increase on transport costs across the supply chain.

Re:Do it for trains

[b0s0z0ku]

Unfortunately, most freight lines in the US aren't electrified. BTW, some locomotives can run both on electric systems and diesel -- i.e. any longer-distance train out of Grand Central in NYC. They run on 750VDC third-rail from Grand Central through upper Manhattan, then start the dlesel when they stop at 125th St/Harlem.

The solution should be massive electrification of freight rail in the US. Regardless of opinions about passenger rail, rail freeight is extremely efficient. Friction from steel wheels on steel rails is much lower than rubber on road, and it can be powered using electricity without lugging fuel, batteries, and/or an engine around.

Re: No one overlooked this

[LynnwoodRooster]

Better to use a turbine (like the AGT1500 that can burn diesel, gas, jet A, etc) to generate electricity then use electric motors. You get all the torque you want from the electric motors, and great efficiency from the turbine.