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Transportation

MIT Says We're Overlooking a Near-Term Solution To Diesel Trucking Emissions (arstechnica.com) 123

Posted by msmash from the marching-ahead dept.
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.
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MIT Says We're Overlooking a Near-Term Solution To Diesel Trucking Emissions More

MIT Says We're Overlooking a Near-Term Solution To Diesel Trucking Emissions

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  • Well it works and it's not new (Score:5, Interesting)

    by Rosco P. Coltrane ( 209368 ) on Thursday April 11, 2019 @02:44PM (#58423164)

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

    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 (Score:1)

      by Anonymous Coward

      Nobody's overlooking it anymore because side effects will soon go away

    • 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.

      • 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

    • Re: (Score:3, Informative)

      by rv6502 ( 5793142 )

      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

      • The latest development in diesel locomotives is true hybrids. They can throttle the diesel engine or turn it off completely, though it's slow changes to address overall load rather than immediate power demands, and they feature battery power storage and regenerative braking. They have been in development for over fifteen years and small numbers have been used by railroads; widespread adoption has not yet happened but is likely in the near future as decreasing battery prices make them more appealing. They ar

    • Re: (Score:1)

      by Lupu ( 815408 )

      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.

      Trucks typically have a longer life expectancy than passenger cars with significantly more miles being driven annually, yet we can see trucks spewing black smog into the atmosphere all the while a fairly recent passenger car will fail an inspection if any of the rigorous emission thresholds is reached.

      Seems a bit more attention on other forms of transportation would be warranted, including trucks receiving the hybrid treatment. There's also been interesting development in using gas turbines as the generator

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

      Cost/Benefit. It's easier to electrify / hybridify (not a real word :) ) a passenger car, and the effect of doing it is greater (light duty passenger cars make up the majority of transport related emissions). Additionally there is higher turnover in passenger vehicles.

      • Partly it's because there were individuals who were willing to pay a premium to be green, and were willing to buy early hybrid cars before they made economic sense. A first generation Prius saved fuel, but most drivers would not get back the extra cost of buying it over the lifetime of the car. Since then the price of gasoline has increased and the price premium for hybrids has dropped, but even now the payback for hybrid cars in pure economic terms is marginal for non-urban drivers. (The hybrid is a big wi

    • Re: (Score:2)

      by havana9 ( 101033 )
      In the '60 electric freight trains were used a lot. like this rail in Turin, used only by FIAT freight trains, and still used in the '80s [polito.it] (note the Fiat Ritmo that were carried).
      In the '50 in Italy were used electric lorries using overhead wires powered by an hydroelectric central [progettodighe.it] that was an hack made because the road was steep for the engines of the time and for the electric company, electricity was cheap.
      For public transportation the problem of electric vehicles was solved more than 100 years ago wit
    • Not entirely true. It's true that the first adoption of hybrid drivetrains in the US was for small passenger cars, but hybrids are rapidly taking over other areas as well. Vehicles that start and stop a lot are prime candidates to be converted to hybrid. Hybrid cars achieve DOUBLE the fuel economy of non-hybrids in congested city driving. Urban taxis have been switching over to hybrids rapidly, and many Uber and Lyft drivers use them as well. Urban bus systems have been converting their fleets to hybrids.

  • No one overlooked this (Score:3)

    by dilvish_the_damned ( 167205 ) on Thursday April 11, 2019 @02:50PM (#58423194) Journal

    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.

    • 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: (Score:2)

        by dfghjk ( 711126 )

        You say this only because you fail to understand what the purpose of hybrid in this application is. It is not for energy recovery made possible by "stop start driving in cities".

        • Go on a thermodynamics course then get back to us.

        • I think the researchers fail to understand a few things as well. GP is correct— the ways hybrids improve include regenerative braking, increased starting torque, potentially simplified transmissions... and that is about it. From an energy perspective, a long-haul truck isn’t going to benefit much from a hybrid design, but there are minor gains (~1-2%?). From an emissions perspective, I’m sure it helps in several areas (especially around the depots where it can charge from the grid).

          But,

          • Re: (Score:2)

            by Shotgun ( 30919 )

            I think the researchers fail to understand a few things as well. GP is correct— the ways hybrids improve include regenerative braking, increased starting torque, potentially simplified transmissions... and that is about it. From an energy perspective, a long-haul truck isn’t going to benefit much from a hybrid design, but there are minor gains (~1-2%?).

            Driving up through Florida from Miami to Jacksonville, I'd agree with you. But, as soon as you approach Atlanta, that battery is going to pay for itself in dollars and health benefits. The hills on I-85 around Atlanta are steep, and the road is packed. Car drivers won't speed up on the downhill so that you can get a running start at the next incline, so you end up burning your brakes on the downhill and dropping down to 35mph with the hammer down on the uphill. A battery pack replacing a dead axle (the

      • 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......

        • Is that what the trip computer told you? Id take it with a pinch and then some.

          • Re: (Score:2)

            by rv6502 ( 5793142 )

            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 i

            • Kind of imitating what the hybrid firmware does to the engine but way more annoying :)

              Hey, that is how I drive...

        • Re: (Score:1)

          by Anonymous Coward

          That's because at long haul driving most modern passenger car engines can get into the upper 30's/40mpg. My 2012 VW Golf non hybrid with a 5 cylinder engine can manage 38/39mpg as indicated on the dash for long term highway driving. I'm talking 1hr+ going at highway speeds.

          The problem ICE engines have is city driving that is stop and go where you have to dump a ton of fuel into the engine to accelerate the car. Hybrids help with this by using electrical energy that was recovered during braking to accelerate

      • Except not all semi-trucks are operating in "on the interstate 99.9% of the time" mode - they're used in semi-local transport. For example, local grocery stores aren't directly stocked from thousands of miles away... their stock is trucked from a local distribution center that's probably 10-50 miles away. In this case, while the semi is certainly still doing a fair bit of highway driving, it's also spending a significant amount of low speed, stop and go driving.

        It's also true that many countries other than

        • Don't forget slowing down for traffic, getting cut off, keeping speed on down hills ... and then the reverse of those. Batteries sized right to store that energy can be useful; they can also just be straight up charge on the long straight while the motor/generator is operating at peak efficiency.

          • Re: (Score:2)

            by rv6502 ( 5793142 )

            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 get

      • Re: (Score:3)

        by lazarus ( 2879 )

        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: (Score:2)

        by tomhath ( 637240 )

        For stop start driving in cities hybrids make sense

        Maybe, if the hybrid can carry enough charge to get through most of the day without depending on the ICE. But carrying several tons of battery means carrying several tons less cargo, so maybe not.

      • Re: No one overlooked this (Score:5, Interesting)

        by LynnwoodRooster ( 966895 ) on Thursday April 11, 2019 @05:09PM (#58424064) Journal
        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.
        • +1 to turbines.

        • 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.

      • Re: (Score:1)

        by rv6502 ( 5793142 )

        Diesel-steam hybrids would make more sense for long-haul highway trucks and there's research being done into it right now.

        New materials mean less boiler maintenance downtime which is part of what killed steam locomotives, along with the time it took to refill the water tank but that'd be less of an issue for a diesel-steam hybrid that can keep going without water, just less efficiently.

    • If you've ever had your car rumble sitting next to a semi idling at a light, you know the answer to that question. There's a ton of wasted energy there for urban areas.

      Freeway long haul? Well, there are efficiencies at 65mph too.....my prius goes into electric silent mode every time I go downhill no matter how fast I'm going.

      And of course, as the first post pointed out, hybrid diesel-electric locomotives have been the norm on rails for the past 60 years, since the mid 1950s.

      • 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: (Score:1)

          by Anonymous Coward

          Well, there is *some* energy saving advantage. As you alluded to in another post, if the diesel is running at the optimum load/speed, it's hard to beat. With hybrid systems that charge a battery that powers the electric engines, they can run the ICE at optimum speed 100% of the time (or turn it off if the battery is at capacity), regardless of vehicle speed. So a hybrid semi could cruise down the highway at 40, or 55, or 65, or 70, whatever, depending on conditions and such, and still run the ICE at optimum

          • Re: (Score:2)

            by Viol8 ( 599362 )

            " As you alluded to in another post, if the diesel is running at the optimum load/speed, it's hard to beat."

            True, but there's some serious conversion losses in the generator and some more in the motor controller system.

            • Re: (Score:1)

              by rv6502 ( 5793142 )

              Just adding: Rule of thumb is optimistically about 10% loss (90% efficiency) in the electric generator, another 10% loss in the electric motors (they're the same thing but used "backward"), those stay pretty consistent through their life (replace the bearings, brushes, and off you go).
              The motor controller system efficiency varies greatly.

              So ignoring the controller system and wiring losses we're down to 81% (0.9 * 0.9) transmission efficiency, or 19% losses.

              The were attempts at direct-drive diesels to increa

              • Re: (Score:2)

                by Viol8 ( 599362 )

                You're joking about steam engines. Their efficiency hovers around 10%. The vast majority of the energy in coal is wasted either simply to keep the water boiling and exhuasted out of the stack while the engine is standing still, or used in warming it all up for a few hours in the first place.

        • Isn’t it more for starting torque?

          • Re: (Score:1)

            by rv6502 ( 5793142 )

            It's because a mechanical clutch pack on a freight train would melt, wear down, and/or explode under the required torque and a shifting gear box would have a similar issue.

            And even when they got that to somehow hold up and work, it made maintenance too difficult.
            Example: https://en.wikipedia.org/wiki/... [wikipedia.org]

            They had 4 diesel engines, with 4 torque converters, 4x 1-way ratchet clutches, 3 differential gear boxes to drive the wheels, AND 2 more diesel engines just acting as superchargers for the 4 other diesel en

      • Re: (Score:1)

        by Anonymous Coward

        I would not call diesel freight trains hybrids. They do not have any electrical energy storage on board. They are purely an electrical generator on wheels and that generator drives the electric traction motors. This is for no other reason than the mechanical complexities of mechanically linking the diesel engine down to the traction wheels and for fuel efficiency. Most engines have a small RPM band where they are most efficient. The diesel locomotives run their engines in this RPM range and vary the energy

      • my prius goes into electric silent mode every time I go downhill no matter how fast I'm going.

        And most diesel trucks activate their Jake Brake [wikipedia.org], which makes them extremely loud but they're not burning fuel.

        hybrid diesel-electric locomotives

        Diesel-electric locomotives are not hybrids. They are electric locomotives with on-board diesel generators. The diesel engines never drive the wheels.

        And only recently have some railroads started experimenting with adding battery packs to recover energy while braking.

      • If you've ever had your car rumble sitting next to a semi idling at a light, you know the answer to that question. There's a ton of wasted energy there for urban areas.

        Auto start-stop doesn't require a PHEV, though. A mild hybrid will do just fine.

        Freeway long haul? Well, there are efficiencies at 65mph too.....my prius goes into electric silent mode every time I go downhill no matter how fast I'm going.

        Diesels are very good about not wasting fuel. But there's regen...

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      Sure, that's why locomotives are all pure diesel....

      There are more reasons to go with a hybrid drive than just duty cycle and regenerative braking.

  • From TFA: (Score:5, Insightful)

    by argStyopa ( 232550 ) on Thursday April 11, 2019 @03:08PM (#58423304) Journal

    "...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.

    • 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.

    • If you're able to dial back on the "herp derp gubbmint *drool*" attitude, you might actually be able to engage your brain. Warning: it might hurt.

      London already has loads of diesel-electric hybrid busses. Heavy urban traffic is almost the perfect use case for hybrid vehicles and also greatly reduces the most polluting phase of diesel engines in high population areas.

      • ...it's almost like I already said: venues where apparently bottom line profit isn't the main motivator, they might work.

        L2Read, dipshit.

  • for this nonsense. Facts and logic? Too complex - we are busy humping with Greta T. here. Get lost!

  • I didn't find any in TFA. I might as well try to read what our two intrepid professors actually wrote.

    What am I saying, this is Slashdot...

  • We have 10.5 years (Score:3)

    by WillAffleckUW ( 858324 ) on Thursday April 11, 2019 @04:25PM (#58423790) Homepage Journal

    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.

    • Comment removed based on user account deletion

    • 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.

      Hybrid systems don't have good trip mileage, they have good in-town mileage. At low speeds drag doesn't play a sizable part in energy consumption, but regenerative braking does. Hybrids only make sense for making mostly short trips. For making only short trips, EVs make more sense. For making only long trips, diesels are best. Gasoline is useful for motorsport, and string trimmers, but we could use ethanol for that stuff.

  • 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 d

  • Solutions must be *VIABLE* or they are not solutions. It is unfortunate, but their cost makes them not an adoptable solution...

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