5 ms·

> Transportation is expensive, both from a relative cost perspective, and also from a resource(-wastefulness) perspective. It really isn't. That locomotive run

> Transportation is expensive, both from a relative cost perspective, and also from a resource(-wastefulness) perspective. It really isn't. That locomotive running flat out may use a lot of energy. But it's also moving an enormous amount of freight, making the energy used per unit mass fairly small. For instance, CSX estimates it can move about 1 ton of freight 492 miles per gallon of diesel: https://www.csx.com/index.cfm/about-us/the-csx-advantage/fuel-efficiency/ https://www.csx.com/index.cfm/about-us/the-csx-advantage/fue... Your trip to the store and back will probably use more energy.

dredmorbius 6y ago
Running rail relatively slowly and on the level is low-power. Put hills or other load factors (start/stop, speed up / slow down, even wind) into the mix and it can go up. Elevation most especially --- railroads will go up to a thousand kilometers out of a straight-line route to avoid elevation gains. A passenger car should get 20-30 miles (30-50 km) per gallon, so unless your store run is several towns over (or you're in the sticks), probably less energy moving a ton 500 miles by rail. Though yes, personal autos are, relative to size and cargo capacity, profligate energy users.
- sudosysgen 6y ago
  What goes up must go down. Every joule you have to put in to climb, you get back in the downhill. So in the end it mostly works out.
  - greenshackle2 6y ago
    I think you are forgetting brakes. There is absolutely no way a train is free-rolling it down a hill. They will be on brakes the entire time - dynos and air brakes - so you are "getting back" a lot of those joules in the form of electricity and heat, not momentum.
    - sudosysgen 6y ago
      Certainly. If this is a significant cost, then regenerative braking is installed. But it is mostly négligeable.
      - dredmorbius 6y ago
        How large a battery are you planning on carrying?
        sudosysgen 6y ago
        None at all. Simply supply it to the grid. It would be perfectly predictable amounts of energy at predictable times, too. Some high speed passenger trains do actually do this, FYI.
        Ichthypresbyter 6y ago
        Although you can only supply the energy to the grid if your locomotive is connected to the grid while running, which diesels aren't.
        sudosysgen 6y ago
        Indeed, they aren't, because it's not economically worth it, because the energy is mostly too small to bother. Which is my entire point.
        LargoLasskhyfv 6y ago
        Not only them. Almost all newer EMU's for regional/commuting here do it, too. And I don't like it because I can hear the fucking chirping of the electronics when they do that. Which is *very annoying' when I have to ride them. Started around 20 years ago.
        dredmorbius 6y ago
        Look into why the US hasn't electrified its long-haul freight. There's a hell of a chicken-egg and scale issue involved.
  - dredmorbius 6y ago
    1. Diesel-electric engines are not regenerative. 2. If you can't get it up, you won't be going down. A 110 car unit coal train grosses 143 tons per car for a 15,750 ton gross trainset weight, excluding locos. Metric is nearly the same, I'll round to 15,000 tonne. Lifting that 1,000 metres (3,300 feet) requires about 150 gigajoules of energy, or the energy equivalent of over 3.5 tonnes of oil. You're not going to recover that fuel going downhill. (Rough numbers for an approximate answer, but it's a lot of energy.) The highest elevation mainline crossing in the US was on the Union Pacific Railroad, Tennessee Pass (10,240 feet, 3,121 m), built in 1882 and retired in 1997. Today it's the San Luis & Rio Grande Railroad, La Veta Pass (9,242 feet, 2,816 metres). https://www.railserve.com/stats_records/highest_steepest_railroads.html https://www.railserve.com/stats_records/highest_steepest_rai...
    - sudosysgen 6y ago
      Diesel electric locomotives don't use regeneration because it doesn't make much sense, not because it's not feasible. Locomotives that have regenerative braking actually do exist. 3.5 tons of fuel for 15 000 tons is 230g of fuel per ton, or around a tenth of a gallon per ton. So even on the highest climb, assuming none of the energy is used on the downhill, that's 3 tenths of a gallon per fuel per ton for the climb. For context, a car's engine could move the average car 5.4 miles on flat ground with the energy required for a locomotive to lift the same car up 3km. As you can see, it's really not that much energy. Which is why regenerative braking isn't used.
      - LargoLasskhyfv 6y ago
        Need to have somewhere to put that regenerated energy. Either overhead wire/third rail, or some sort of 'tender' with storage like the old steamers had for coal and some water.
        sudosysgen 6y ago
        Certainly, in general it's done via overhead wire or third rail and feeds energy back into the grid. It's not worth it in general when those aren't already present.

dredmorbius 6y ago

Running rail relatively slowly and on the level is low-power. Put hills or other load factors (start/stop, speed up / slow down, even wind) into the mix and it can go up. Elevation most especially --- railroads will go up to a thousand kilometers out of a straight-line route to avoid elevation gains. A passenger car should get 20-30 miles (30-50 km) per gallon, so unless your store run is several towns over (or you're in the sticks), probably less energy moving a ton 500 miles by rail. Though yes, personal autos are, relative to size and cargo capacity, profligate energy users.

sudosysgen 6y ago
What goes up must go down. Every joule you have to put in to climb, you get back in the downhill. So in the end it mostly works out.
- greenshackle2 6y ago
  I think you are forgetting brakes. There is absolutely no way a train is free-rolling it down a hill. They will be on brakes the entire time - dynos and air brakes - so you are "getting back" a lot of those joules in the form of electricity and heat, not momentum.
  - sudosysgen 6y ago
    Certainly. If this is a significant cost, then regenerative braking is installed. But it is mostly négligeable.
    - dredmorbius 6y ago
      How large a battery are you planning on carrying?
      - sudosysgen 6y ago
        None at all. Simply supply it to the grid. It would be perfectly predictable amounts of energy at predictable times, too. Some high speed passenger trains do actually do this, FYI.
        Ichthypresbyter 6y ago
        Although you can only supply the energy to the grid if your locomotive is connected to the grid while running, which diesels aren't.
        sudosysgen 6y ago
        Indeed, they aren't, because it's not economically worth it, because the energy is mostly too small to bother. Which is my entire point.
        LargoLasskhyfv 6y ago
        Not only them. Almost all newer EMU's for regional/commuting here do it, too. And I don't like it because I can hear the fucking chirping of the electronics when they do that. Which is *very annoying' when I have to ride them. Started around 20 years ago.
        dredmorbius 6y ago
        Look into why the US hasn't electrified its long-haul freight. There's a hell of a chicken-egg and scale issue involved.
- dredmorbius 6y ago
  1. Diesel-electric engines are not regenerative. 2. If you can't get it up, you won't be going down. A 110 car unit coal train grosses 143 tons per car for a 15,750 ton gross trainset weight, excluding locos. Metric is nearly the same, I'll round to 15,000 tonne. Lifting that 1,000 metres (3,300 feet) requires about 150 gigajoules of energy, or the energy equivalent of over 3.5 tonnes of oil. You're not going to recover that fuel going downhill. (Rough numbers for an approximate answer, but it's a lot of energy.) The highest elevation mainline crossing in the US was on the Union Pacific Railroad, Tennessee Pass (10,240 feet, 3,121 m), built in 1882 and retired in 1997. Today it's the San Luis & Rio Grande Railroad, La Veta Pass (9,242 feet, 2,816 metres). https://www.railserve.com/stats_records/highest_steepest_railroads.html https://www.railserve.com/stats_records/highest_steepest_rai...
  - sudosysgen 6y ago
    Diesel electric locomotives don't use regeneration because it doesn't make much sense, not because it's not feasible. Locomotives that have regenerative braking actually do exist. 3.5 tons of fuel for 15 000 tons is 230g of fuel per ton, or around a tenth of a gallon per ton. So even on the highest climb, assuming none of the energy is used on the downhill, that's 3 tenths of a gallon per fuel per ton for the climb. For context, a car's engine could move the average car 5.4 miles on flat ground with the energy required for a locomotive to lift the same car up 3km. As you can see, it's really not that much energy. Which is why regenerative braking isn't used.
    - LargoLasskhyfv 6y ago
      Need to have somewhere to put that regenerated energy. Either overhead wire/third rail, or some sort of 'tender' with storage like the old steamers had for coal and some water.
      - sudosysgen 6y ago
        Certainly, in general it's done via overhead wire or third rail and feeds energy back into the grid. It's not worth it in general when those aren't already present.