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Have you checked your calculations against David MacKay's? His conclusion was that "International shipping is a surprisingly efficient user of fossil fuels; so

Have you checked your calculations against David MacKay's? His conclusion was that "International shipping is a surprisingly efficient user of fossil fuels; so getting road transport off fossil fuels is a higher priority than getting ships off fossil fuels." http://www.inference.phy.cam.ac.uk/withouthotair/c15/page_95.shtml http://www.inference.phy.cam.ac.uk/withouthotair/c15/page_95... http://www.inference.phy.cam.ac.uk/withouthotair/c20/page_133.shtml http://www.inference.phy.cam.ac.uk/withouthotair/c20/page_13...

robomartin 14y ago
I think it's simple physics. Moving anything on water at any speed is far more expensive than moving the equivalent thing on land. It is, at the simplest level, a comparison of hydrodynamic drag vs aerodynamic drag. It can't possibly be more efficient to displace water for days and days rather than push air out of the way, even at high speed.
- graeham 14y ago
  Comparing hydrodynamics and aerodynamics here is not quite comparing apples to apples: I expect much less surface area is exposed to water on a ship than exposed to air on a train, and speed are lower. Drag scales with velocity squared. A calculation is required, and would also have to account for the weight of cargo each is carrying.
  - robomartin 14y ago
    Sure it is. Without air or water the cost of shipping would be almost nil. POWER to overcome drag is proportional to the CUBE of the velocity. This is the main reason container ships have been slowing down from about 30 miles per hour to 20 in direct response to the cost of fuel. The power to overcome drag is also directly proportional to the density of the fluid. Air density: 1.2041 kg/m^3 Water density: 1,000.00 kg/m^3 (pure water) Sea water is roughly 830 times denser than air. Therefore, you need 830 times more POWER to move the same object through water at the same speed when compared with air. Here's a practical example: Let's move a Toyota Camry through air and water at 20 miles per hour and compare. We'll ignore friction. http://www.toyota.com/camry/specs.html http://www.toyota.com/camry/specs.html Frontal area: 57.9in x 71.7in = 2.68 m^2 Coefficient of drag: 0.28 Power = 1/2 * density * velocity ^ 3 * area * coefficient of drag Power in air = 1/2 * 1.2041 Kg/m^3 * (8.9 m/s ^ 3) * 2.68 m^2 * 0.28 = 0.43 horsepower Power in water = 1/2 * 1,000 Kg/m^3 * (8.9 m/s ^ 3) * 2.68 m^2 * 0.28 = 353.02 horsepower In other words, you need 830 times more power. How about now moving up to 40 miles per hour? Power in air = 3.4 HP Power in water = 2,824.14 The same 830 to 1 power ratio. However, moving the same object through water at double the speed just became EIGHT TIMES more expensive. If we moved the Toyota Camry through air at 188 miles per hour we would need nearly exactly the same power required to move the same car through water at 20 miles per hour. Bottom line, moving anything on water is very expensive if you have to burn fuel to do it. Unless I am missing something very fundamental there simply is no comparison.
    - graeham 14y ago
      My "apples to apples" point is that density is not the only parameter to change when comparing ships to trains. 1. Assuming the same speeds. Ships go slower than trains (say 40kmph compared to 80kmph). 2. The frontal area is not the same as only part of the ship is underwater. Further, for a long train, the frontal area drag is likely less than the skin friction drag. 3. The coefficient of drag is not the same as the CD of a train is different than for a boat. 4. The amount of cargo on each is not the same, and would need to be normalized for a fair comparison. I'd be happy to take a quick look at your materials off-line, please send to jd2planks at hotmail
      - robomartin 14y ago
        I really don't see it as even close. Moving anything through air requires far less power than moving the same thing through water. With regards to the rest of your comments, I've done some of those calculations. Again, there is no comparison. I need to repeat that the idea here is NOT to in ANY WAY use existing truck or cargo rail systems. They just don't perform. Here in the US you are lucky if you can get cargo trains moving on average at 20 to 30 miles per hour. In other words, the move just as slowly as cargo ships, except that they can't pull the same number of containers. The idea is that a new purpose-built system is the solution. Also, please keep in mind that the idea here isn't necessarily to search for the most efficient mode of cargo transportation in complete isolation of the realities of where they derive their energy from. Here's a very interesting paper on the aerodynamics of high-speed trains: http://ompldr.org/vMXlsOA/Aerodynamics_HSR02.pdf http://ompldr.org/vMXlsOA/Aerodynamics_HSR02.pdf Anyhow, I sent you all my files via a shared Dropbox folder. I'd be interested in what you have to say once you have a chance to look at it all. To be sure, there are huge issues with the idea that have absolutely nothing whatsoever to do with science and technology. I could not imagine the problems one might encounter in terms of the various special-interest groups that would get in the way of building such a thing, even if it was so good that it would save the world. I think the phrase "can't get out of our own way to save our lives" rings true in more than one way, at least in the US.
        leoedin 14y ago
- jackpirate 14y ago
  But container ships move so much stuff at a time that they're vastly more efficient than, say, big rig trucks. I'll bet they even give rail a run for its money.
  - robomartin 14y ago
    Big rig trucks isn't any part of my proposal. Conventional rail in the US is horribly crippled. Shoot me an email and you can look at my data. Then we can have a discussion. I am very interested in having a discussion from a common frame of reference.
    - tripzilch 14y ago
      Then why not write a blog article about it or something. I don't see why such discussion should happen "off list", because it would in fact restrict the discussion to one-on-one's between you and whoever emails you, without anyone benefiting from the extra eyes.
      - swalsh 14y ago
        I can understand his position. I would guess he wants to refine the idea privately a bit before presenting it to a larger more public audience.
- xxgreg 14y ago
  You can pull a 10 tonne yacht with one hand on a rope. Try pulling a 10 tonne truck... Also according to the US Transportation Energy Book, waterbourne transport more than a order of magnitude more efficient than road freight, and about 50% more efficient than rail. http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportation#US_Freight_transportation http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportati...
  - robomartin 14y ago
    On your first point, I refer you to Google and Wikipedia for excellent articles on basic physics. In particular look to understand the relationship of power as it relates to speed. On the second point. Our cargo rail system is crap. Nowhere in my write-up am I proposing that we unload 100,000 cargo ships per year and load these containers onto diesel trucks or the current train system. That would be incredibly dumb, inefficient, more harmful to the environment and, well, actually impossible. No, the idea is that a new highly-efficient, all-electric, highly-automated and cargo-only transportation system be built with the express purpose of moving container-based cargo from coast to coast (and port to port) at the highest possible speed and lowest possible power consumption. The idea further suggests that the required energy can come from nuclear, wind and solar power. The complete elimination of the burning of the most harmful form of fossil fuel from the transportation system is one of the stated goals of the idea. Furthermore, the idea is also to look 50, 100 or even 200 years into the future. Pollution aside, fossil fuel cost is absolutely, positively guaranteed to increase over the next 200 years. The current system of burning millions of tons of bunker-c fuel per year to bring widgets to Walmart isn't a viable and scalable long-term solution. Not to mention the fact that it is royally fucking up the environment at many levels. I am not a crazy environmentalist by any measure, but this is stupid.
    - deleted 14y ago
      [deleted]
    - jasonwatkinspdx 14y ago
      "On the second point. Our cargo rail system is crap. Nowhere in my write-up am I proposing that we unload 100,000 cargo ships per year and load these containers onto diesel trucks or the current train system. That would be incredibly dumb, inefficient, more harmful to the environment and, well, actually impossible." The US freight rail system is the best in the world.[1] We move 10x more than Europe most years on a tons times distance basis. The running gear may look antiquated, but the fundamental numbers are staggering. "No, the idea is that a new highly-efficient, all-electric, highly-automated and cargo-only transportation system be built with the express purpose of moving container-based cargo from coast to coast (and port to port) at the highest possible speed and lowest possible power consumption." There is very little demand for raising the speed of freight rail in the US. Speed generally compounds inefficiencies. Freight handling is by and large already automated and container based in the US rail network. Existing electric designs preclude the use of double stacked container flat cars, one of the keys of US freight efficiency. Perhaps you have an innovation here? Building an entirely new high speed electric rail network for freight is an absurd idea. I don't think you've even begun to model the economic realities, particularly the capex of building a new rail network radius'd and graded for high speed, with all above grade crossings. [1]: http://www.economist.com/node/16636101 http://www.economist.com/node/16636101
- MaysonL 14y ago
  If we had trains or planes as large as the tankers and container ships, you would probably be right. The thing is that drag is areal, freight is volumetric. Drag goes up as the square of the dimension, freight capacity as the cube. This allows large ships to be much more efficient than trucks or trains.
  - robomartin 14y ago
    Power to overcome form drag goes up with the cube of the velocity and linearly with fluid density. Moving something through water requires over 800 times more power than in air. The only thing that could make land-based transport less efficient (other than fuel and power-plant issues) is rolling and drivetrain losses. I doubt that those make-up for the over 800-to-1 power discrepancy. The greater point here isn't a pissing match between individual efficiencies but rather to look at the problem with a long (50 to 200 years) perspective in terms of pollution, fossil fuel consumption, geo-political and economic concerns and more.
    - ET3 14y ago
      The drag of ships moving at less than hull speed (non planing) is a function of: skin friction (shearing of the boundary layer), wave making, and Reynolds number (related to the length of the ship, and the viscosity of the fluid). One interesting article says that one of the mega container ships pollutes more than 50 million cars see: http://www.guardian.co.uk/environment/2009/apr/09/shipping-pollution http://www.guardian.co.uk/environment/2009/apr/09/shipping-p... The claim is that just 15 of the worlds biggest ships pollute more than all cars in the world combined.
      - robomartin 14y ago
        Yup. This is exactly what I was driving at when I said that everyone is ignoring the elephant in the room. You can clean-up automobile emissions all you want. You can even stop flying all the jetliners in the world. Still, by far, the largest source of pollution in transportation are container ships. What they are doing to our planet both above and in water (species pollution) is horrible.

robomartin 14y ago

I think it's simple physics. Moving anything on water at any speed is far more expensive than moving the equivalent thing on land. It is, at the simplest level, a comparison of hydrodynamic drag vs aerodynamic drag. It can't possibly be more efficient to displace water for days and days rather than push air out of the way, even at high speed.

graeham 14y ago
Comparing hydrodynamics and aerodynamics here is not quite comparing apples to apples: I expect much less surface area is exposed to water on a ship than exposed to air on a train, and speed are lower. Drag scales with velocity squared. A calculation is required, and would also have to account for the weight of cargo each is carrying.
- robomartin 14y ago
  Sure it is. Without air or water the cost of shipping would be almost nil. POWER to overcome drag is proportional to the CUBE of the velocity. This is the main reason container ships have been slowing down from about 30 miles per hour to 20 in direct response to the cost of fuel. The power to overcome drag is also directly proportional to the density of the fluid. Air density: 1.2041 kg/m^3 Water density: 1,000.00 kg/m^3 (pure water) Sea water is roughly 830 times denser than air. Therefore, you need 830 times more POWER to move the same object through water at the same speed when compared with air. Here's a practical example: Let's move a Toyota Camry through air and water at 20 miles per hour and compare. We'll ignore friction. http://www.toyota.com/camry/specs.html http://www.toyota.com/camry/specs.html Frontal area: 57.9in x 71.7in = 2.68 m^2 Coefficient of drag: 0.28 Power = 1/2 * density * velocity ^ 3 * area * coefficient of drag Power in air = 1/2 * 1.2041 Kg/m^3 * (8.9 m/s ^ 3) * 2.68 m^2 * 0.28 = 0.43 horsepower Power in water = 1/2 * 1,000 Kg/m^3 * (8.9 m/s ^ 3) * 2.68 m^2 * 0.28 = 353.02 horsepower In other words, you need 830 times more power. How about now moving up to 40 miles per hour? Power in air = 3.4 HP Power in water = 2,824.14 The same 830 to 1 power ratio. However, moving the same object through water at double the speed just became EIGHT TIMES more expensive. If we moved the Toyota Camry through air at 188 miles per hour we would need nearly exactly the same power required to move the same car through water at 20 miles per hour. Bottom line, moving anything on water is very expensive if you have to burn fuel to do it. Unless I am missing something very fundamental there simply is no comparison.
  - graeham 14y ago
    My "apples to apples" point is that density is not the only parameter to change when comparing ships to trains. 1. Assuming the same speeds. Ships go slower than trains (say 40kmph compared to 80kmph). 2. The frontal area is not the same as only part of the ship is underwater. Further, for a long train, the frontal area drag is likely less than the skin friction drag. 3. The coefficient of drag is not the same as the CD of a train is different than for a boat. 4. The amount of cargo on each is not the same, and would need to be normalized for a fair comparison. I'd be happy to take a quick look at your materials off-line, please send to jd2planks at hotmail
    - robomartin 14y ago
      I really don't see it as even close. Moving anything through air requires far less power than moving the same thing through water. With regards to the rest of your comments, I've done some of those calculations. Again, there is no comparison. I need to repeat that the idea here is NOT to in ANY WAY use existing truck or cargo rail systems. They just don't perform. Here in the US you are lucky if you can get cargo trains moving on average at 20 to 30 miles per hour. In other words, the move just as slowly as cargo ships, except that they can't pull the same number of containers. The idea is that a new purpose-built system is the solution. Also, please keep in mind that the idea here isn't necessarily to search for the most efficient mode of cargo transportation in complete isolation of the realities of where they derive their energy from. Here's a very interesting paper on the aerodynamics of high-speed trains: http://ompldr.org/vMXlsOA/Aerodynamics_HSR02.pdf http://ompldr.org/vMXlsOA/Aerodynamics_HSR02.pdf Anyhow, I sent you all my files via a shared Dropbox folder. I'd be interested in what you have to say once you have a chance to look at it all. To be sure, there are huge issues with the idea that have absolutely nothing whatsoever to do with science and technology. I could not imagine the problems one might encounter in terms of the various special-interest groups that would get in the way of building such a thing, even if it was so good that it would save the world. I think the phrase "can't get out of our own way to save our lives" rings true in more than one way, at least in the US.
      - leoedin 14y ago
jackpirate 14y ago
But container ships move so much stuff at a time that they're vastly more efficient than, say, big rig trucks. I'll bet they even give rail a run for its money.
- robomartin 14y ago
  Big rig trucks isn't any part of my proposal. Conventional rail in the US is horribly crippled. Shoot me an email and you can look at my data. Then we can have a discussion. I am very interested in having a discussion from a common frame of reference.
  - tripzilch 14y ago
    Then why not write a blog article about it or something. I don't see why such discussion should happen "off list", because it would in fact restrict the discussion to one-on-one's between you and whoever emails you, without anyone benefiting from the extra eyes.
    - swalsh 14y ago
      I can understand his position. I would guess he wants to refine the idea privately a bit before presenting it to a larger more public audience.
xxgreg 14y ago
You can pull a 10 tonne yacht with one hand on a rope. Try pulling a 10 tonne truck... Also according to the US Transportation Energy Book, waterbourne transport more than a order of magnitude more efficient than road freight, and about 50% more efficient than rail. http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportation#US_Freight_transportation http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportati...
- robomartin 14y ago
  On your first point, I refer you to Google and Wikipedia for excellent articles on basic physics. In particular look to understand the relationship of power as it relates to speed. On the second point. Our cargo rail system is crap. Nowhere in my write-up am I proposing that we unload 100,000 cargo ships per year and load these containers onto diesel trucks or the current train system. That would be incredibly dumb, inefficient, more harmful to the environment and, well, actually impossible. No, the idea is that a new highly-efficient, all-electric, highly-automated and cargo-only transportation system be built with the express purpose of moving container-based cargo from coast to coast (and port to port) at the highest possible speed and lowest possible power consumption. The idea further suggests that the required energy can come from nuclear, wind and solar power. The complete elimination of the burning of the most harmful form of fossil fuel from the transportation system is one of the stated goals of the idea. Furthermore, the idea is also to look 50, 100 or even 200 years into the future. Pollution aside, fossil fuel cost is absolutely, positively guaranteed to increase over the next 200 years. The current system of burning millions of tons of bunker-c fuel per year to bring widgets to Walmart isn't a viable and scalable long-term solution. Not to mention the fact that it is royally fucking up the environment at many levels. I am not a crazy environmentalist by any measure, but this is stupid.
  - deleted 14y ago
    [deleted]
  - jasonwatkinspdx 14y ago
    "On the second point. Our cargo rail system is crap. Nowhere in my write-up am I proposing that we unload 100,000 cargo ships per year and load these containers onto diesel trucks or the current train system. That would be incredibly dumb, inefficient, more harmful to the environment and, well, actually impossible." The US freight rail system is the best in the world.[1] We move 10x more than Europe most years on a tons times distance basis. The running gear may look antiquated, but the fundamental numbers are staggering. "No, the idea is that a new highly-efficient, all-electric, highly-automated and cargo-only transportation system be built with the express purpose of moving container-based cargo from coast to coast (and port to port) at the highest possible speed and lowest possible power consumption." There is very little demand for raising the speed of freight rail in the US. Speed generally compounds inefficiencies. Freight handling is by and large already automated and container based in the US rail network. Existing electric designs preclude the use of double stacked container flat cars, one of the keys of US freight efficiency. Perhaps you have an innovation here? Building an entirely new high speed electric rail network for freight is an absurd idea. I don't think you've even begun to model the economic realities, particularly the capex of building a new rail network radius'd and graded for high speed, with all above grade crossings. [1]: http://www.economist.com/node/16636101 http://www.economist.com/node/16636101
MaysonL 14y ago
If we had trains or planes as large as the tankers and container ships, you would probably be right. The thing is that drag is areal, freight is volumetric. Drag goes up as the square of the dimension, freight capacity as the cube. This allows large ships to be much more efficient than trucks or trains.
- robomartin 14y ago
  Power to overcome form drag goes up with the cube of the velocity and linearly with fluid density. Moving something through water requires over 800 times more power than in air. The only thing that could make land-based transport less efficient (other than fuel and power-plant issues) is rolling and drivetrain losses. I doubt that those make-up for the over 800-to-1 power discrepancy. The greater point here isn't a pissing match between individual efficiencies but rather to look at the problem with a long (50 to 200 years) perspective in terms of pollution, fossil fuel consumption, geo-political and economic concerns and more.
  - ET3 14y ago
    The drag of ships moving at less than hull speed (non planing) is a function of: skin friction (shearing of the boundary layer), wave making, and Reynolds number (related to the length of the ship, and the viscosity of the fluid). One interesting article says that one of the mega container ships pollutes more than 50 million cars see: http://www.guardian.co.uk/environment/2009/apr/09/shipping-pollution http://www.guardian.co.uk/environment/2009/apr/09/shipping-p... The claim is that just 15 of the worlds biggest ships pollute more than all cars in the world combined.
    - robomartin 14y ago
      Yup. This is exactly what I was driving at when I said that everyone is ignoring the elephant in the room. You can clean-up automobile emissions all you want. You can even stop flying all the jetliners in the world. Still, by far, the largest source of pollution in transportation are container ships. What they are doing to our planet both above and in water (species pollution) is horrible.