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

[drinkypoo]

I keep wondering how light passenger cars got the hybrid treatment first and long-haul trucks still haven't

Trains didn't have batteries until recently. Instead of regenerative braking, diesel-electric locomotives used a carbon pile beneath the engine to dissipate the motor braking energy. Cars went hybrid first because it was easier to build them, because they didn't have such large power-handling requirements.

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.

Re:Well it works and it's not new

[taiwanjohn]

Even most PHEV automobiles have very little all-electric range. The car that comes closest to the description in TFS is the Chevy Volt, with 55 mi EV range plus unlimited gas-powered range at ~38 mpg, which is pretty good mileage for a car that weighs 3700 lbs. It's the only PHEV I'm aware of that can truly function as 100% EV or 100% ICE -- If you never plug it in, it functions just like an ICE car; if you never fuel it, if functions just like a pure EV. Most (if not all) of the other PHEVs have such short all-electric range that they're essentially useless as a pure EV. (There may be some new ones coming out that I'm not aware of.)

Having just bought a used Volt myself recently, the more I learn about it, the more impressed I am with the engineering. (It's a shame they're about to stop making them, but I chalk that up to GM's inept marketing.) Seems to me they could just up-scale the Volt's drive train to semi-tractor size, and they'd have a pretty compelling product.

No one overlooked this

[dilvish_the_damned]

Hybrids really shine when they are compared against gasoline engines that do not run full duty. I donâ(TM)t think they compare so well against either diesel or full duty situations. That is, a battery bank isnâ(TM)t going to help much when the truck is spending itâ(TM)s life already at full throttle.

Re: No one overlooked this

[Viol8]

Yup. For stop start driving in cities hybrids make sense. For long distance driving the battery is just a deadweight being dragged around by the ICE thats doing all the work. Also diesel is much less flammable than petrol or methanol and doesnt require a spark, so diesel vehicles are allowed in some industrial places that spark ignition cannot go. Eg fuel depots.

Re: No one overlooked this

[Marxist Hacker 42]

When I first bought my prius, I thought that was true too. It wasn't. I had a long trip- Beaverton to Prineville in Oregon planned. Going I got a very respectable 40 miles to the gallon. No great shakes, I thought, many similar small gas engines got similar, in the 25-35 MPG range. Then I drove home- and got 65 MPG.

Reminded me of my underpowered Honda Spree scooter I drove in college, which could hit 45- downhill and with a tailwind......

Re: No one overlooked this

[Viol8]

Diesel electric locos have nothing to do with energy saving and everything to do with not having to have a very complex and fragil emechanical transmission system going to 12 wheels on 2 pivoting bogies. Before electric there was diesel hydraulic which solved the same problem albeit less reliably.

Re: No one overlooked this

[Viol8]

However you say it in whatever fucked up dialect of English you speak, here in England where real English is spoken we say go on a course. And the only advantage of a hybrid setup is for energy recovery plus to prevent engine labour at low rpm. So go get youself a fucking clue.

Re: No one overlooked this

[lazarus]

Yep, you at the the parent are spot-on. This is a solution looking for a problem. Diesel is still the best for long-haul (range, durability and cost-effectiveness), and short-haul is going to be handled by electric Semis.

A viable alternative for long-haul would be electric freight trains. We probably could have had that by now if we had put the right incentives and regulations in place years ago.

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.

Re:No one overlooked this

[rv6502]

Trucks do operate very close to or even at full throttle at highway speed (the laws of aerodynamics are a bitch for what is effectively a 12' high wall going 70mph) and he was first talking about gasoline engines which are very inefficient at anything but full throttle.

Diesel engines don't suffer from this issue owning to not having the throttle valve in the intake that gasoline engines have. Gasoline engines effectively have a brake put on the engine when they're not being floored to keep the air-fuel ratio correct for spark ignition. They're literally being choked to reduce the power, making them less efficient at anything but full duty.

Diesel engines don't have that problem they always get as much air as can flow in through the air filter and are controlled entirely by the amount of fuel injected.

That's why smaller gasoline engines are much more fuel efficient than a larger one (being always closer to full throttle than the larger engine) while engine size does not matter anywhere as much for diesel engines for efficiency.

Re: No one overlooked this

[rv6502]

No improbable.
My 1.2L 3cyl non-hybrid gasoline ICE gets about 50mpg avg on my commute in the summer. Roughly confirmed by gas tank fillup and some math.

The more recent hybrids firmware cycles the ICE when cruising between struggle-to-charge-the-batteries and completely off, the very first hybrids didn't.

I've been able to push my non-hybrid to 58mpg by driving "stupidly" efficient on the highway when no one was around: floor it in 5th (no downshift) to 75mph, let go and cruise down to 45mph, repeat.
Kind of imitating what the hybrid firmware does to the engine but way more annoying :)

That said there's no point in doing that with a diesel engine. They don't have the intake throttle valve that cripples gasoline engine efficiency at low loads and diesels tend to run more efficient when quite a bit below maximum load for more complete combustion (less fuel, more air).

Diesels don't gain nearly as much from electric hybridisation.
Diesel-steam however looks promising for long hauls. A potential 60%-70% fuel efficiency which may be worth the time spent to refill the water tank. Recuperates a good chunk of wasted energy from the exhaust heat.

Re: No one overlooked this

[rv6502]

The problem is the amount of energy we'd be throwing at the batteries and the required size.
Cars already struggle with the regenerative braking without catching on fire or prematurely wearing down the batteries making it practically a joke, it's a negligible amount of energy that is recuperated (supercaps would be great for this but we're not there yet).

They've experimented with air-oil compressors on city delivery trucks since that can handle a very quick "recharge", it's effectively an air spring that gets wound up when the truck stops and unwound to launch it again. Very efficient.

But that's for a "small" delivery truck, the tank would need to be huge to stock the energy of a long downhill drive on a double-trailer big rig hauling tree logs.

Batteries would also need to be ridiculously large, which would add their own weight, greatly reducing the amount of (profitable) freight a truck would be allowed to transport.

Re: No one overlooked this

[serviscope_minor]

and great efficiency from the turbine.

Turbines are much less efficient than diesel engines, topping out at about 30% for shaft power. Automotive diesel engines hit over 40% for cars and 45% for bigger vehicles. Marine diesels get into the low 50s.

Pretty much the only thermal plants which beat diesel are large combined cycle gas turbine/Rankine hybids, which are heading towards about 65%. And you need huge low pressure turbines and a good sub atmospheric condenser to get there.

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:From TFA:

[Thelasko]

Weight is a HUGE deal. Trucks are limited to 80,000lb on US roads. Every pound for batteries, is a pound less in money making cargo. While you can buy a truck with 300 gallon fuel tanks, not many are sold that way, because that's just more weight that isn't making money.

Burning Food.

[Zorro]

Never a good idea to burn food.

Re:Burning Food.

[PPH]

spent cooking oil

Not nearly enough. Particularly if you health nuts don't keep up your end of the deal by eating more fried food. To make an appreciable dent in the fuel market, you are going to have to grow something like palm oil. On a huge scale. Here comes the deforestation and the end of the orangutans.

Re:Burning Food.

[DigiShaman]

The pure hydrogen economy was always stupid idea. Major logistical problems involve storage and safe handling. Also the pressure vessels to contain the gas has to be really strong to withstand an automotive accident via impact.

We have the oil pipeline infrastructure in place already. Wouldn't it make more sense to simple convert energy (solar, wind, geothermal, hydroelectric, nuclear) to a process of combining hydrogen and carbon for synthetic hydrocarbons?

Re:Begs the question...

[MrVictor]

AC really meant "most energy dense fuel".

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.

We have 10.5 years

[WillAffleckUW]

This will still increase actual emissions.

Sure, if you're driving a 12 mpg truck, getting a new hybrid with 40 mpg will be better, but it had to be made first.

Replace more trucks and cars with trains, and convert those to electric/hydrogen hybrids instead. High speed passenger/freight trains and medium-speed efficient trains.

And stop ordering Same Day Service or Amazon Prime, you're killing the planet.

Actually, the planet will survive, you won't.

Elephants in the room?

[rv6502]

I'm concerned this focus (not the Ford kind) on cars and trucks ICE regarding pollution sounds more and more like an ideological crusade and/or some kind of misdirection/distraction.

It's like optimising code, you find and go for the hot spot but at some point it's not the hot spot anymore.

Between the lobbyists (farming, container ships, etc), ecological zealots (not the informed reasonable kind), and a bit of a sunny-California tech world somewhat disconnected from the rest of the world (FYI: Solar panels don't work when covered in snow or on cloudy coasts, guys. Neither are electric cars that get garbage range under -30'C practical.)
I fear we're being manipulated/distracted into overlooking some lower hanging fruits for political convenience.

Even even looking at cars we need to take into account that electric cars are actually MORE polluting than traditional ICE cars in regions using coal-fired electric power plants.

That's not counting that they're more polluting to produce and recycle. It generates 8.8 tonnes of CO2 to make an electric car vs 5.6 tonnes for an ICE car, should we take the fight first over making cars last much longer? Keep in mind that's just the CO2 environmental cost for production, nothing said about all the other solvents and the recycling costs.

How can we make sure we're not taken for a ride (pun intended again, sue me :) ) by lobby groups who don't want us to look more closely at the pollution their industry is generating?

Re:Do it for trains

[havana9]

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.

By the way electric rail for passengers could be a viable alternative to private transportation. This need planning and investments. Operations research is less cool than AI for self driving cars but making public transportation more efficient could be a better investment. Unfortunately the urban sprawl that was made viable by the automobile makes difficult for big suburban areas to have good public transport.