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_transportati...
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.
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.
What I meant is that it could be much, much better. The article you point out hints at some of the issues: The inter-mingling of passenger and cargo trains ends-up seriously affecting the potential performance of cargo trains.
With regards to it being an absurd idea. Well, of course it is! And so is the case for nearly every idea that sparked a revolution in technology and thinking. The earth NOT at the center of the universe? Absurd! The earth not flat? Absurd? Everyone needs a computer on their desk? Absurd!
Not that I am comparing this to any of those shifts in technology. What I am trying to point out is that being open minded enough to even consider the seemingly absurd is an important part of discovering new ideas and developing new technologies. I always consider the absurd. I have hundreds of ideas catalog that are probably absurd. The alternative is to discount everything as ridiculous without even giving it an honest look. I just don't do that.
For example: Could this high speed train take the form of an underground tunnel connecting both coasts? This is absolutely ridiculous and probably even insane to consider. However, I take the approach of at least doing the research to try to get a sense of proportion in terms of cost and technical feasibility. For example, would there be an important mining element to the project that could offset the costs? I don't know and I am not trying to argue for a 3,000 mile tunnel. All I am saying is that I believe that it is very important to give seemingly ridiculous ideas a chance to be explored and, if need be, discarded based on data and not knee-jerk reaction.
This probably deserves a little more attention.
Having done a lot of sailing as well as ocean-fishing on different size vessels I know exactly what you are talking about. What you might be confusing is that at zero speed there's a huge difference between something floating on water and a truck resting on the ground.
In the case of a large boat floating on water, so long as you are not after making it move quickly you are almost just fighting inertia. So, yes, a fifteen year old kid pulling on a rope could make a large boat move.
When it comes to a truck sitting on the ground you have to contend with rolling friction as well as the static friction (because nothing is moving) and the viscous drag of all the mechanical elements, oil and grease in the drivetrain. It could take hundreds of pounds of force to get it to budge. Once your break through static friction then you have a much reduced dynamic friction and viscous drag (oil and grease in the drivetrain) --again, so long as speed is very, very low-- as well as the rolling friction of the tires.
If, on the other hand, that truck was resting on a frozen lake bed and if the tires are not frozen-glued into the ice, and, if the ice is not deformed under the tires, the same fifteen year old kid could move it just as well as he moved the boat. In fact, it might even be easier because there isn't a significant v^3 component to the power required to make it move.
Once you start to add speed to the problem it is easy to see that moving the same object through water will require at least 830 times more water.
At speed the power required to counter drag comes into play.
Power = 1/2 * fluid density * velocity ^3 * coefficient of drag * area
If it takes one horsepower to move something in air at a given speed you'll need over 800 horsepower to achieve the same speed in water. It's the difference between a model airplane engine and a Formula 1 race car engine.
There's a good article in Wikepedia on drag:
http://en.wikipedia.org/wiki/Drag_(physics)
Get down to the "Power" heading. That's the formula you want to look at.
To get back to your yacht vs. truck example. What you would really have to experience is pulling each of them at 20 or 30 miles per hour with a rope (chain?). Of course, it would take super-human strength and endurance to be able to do that.
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)
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
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
How about now moving up to 40 miles per hour?
Power in air = 3.4 HP
Power in water = 2,824.14
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.
Unless it's a submarine, a ship doesn't move through water, it floats on top of it. The wetted surface is going to be a tiny fraction of the total frontal area. 90% or more of the hydrodynamic drag of a ship (by area) is in the air, not in the water.
For example, here is a nice little 21-foot 1200-lb motor boat that can reach 16 knots with a 25 hp motor, while carrying four people: http://www.southportislandmarine.com/ordereze/1011/page.aspx
The nice little boat you are linking to can do what it does largely because at a certain speed it will start to plane. These are very, very different conditions.
Two of the components of drag on a boat are form and parasitic or frictional drag. The first can be thought of as simply the drag created to push water out of the way. Here the shape of the boat is important. The second is the drag created by water "rubbing" against the portion of the hull in contact with it. Think of sandpaper against wood. More wood and more sandpaper means more resistance to motion.
As speed increases both friction and form drag increase with the square of the speed.
On a planing hull --one that can generate lift and get the boat up and partially out of the water-- form drag decreases significantly once you are "on a plane" (off the water) and friction drag increases. As it turns out, each boat has a sweet spot where it operates best. And, of course, as you get on a plane the power required in order to reach or sustain a given speed decreases significantly when compared to a displacement (non-planing) hull.
A Panamax ship carrying 4,400 TEU does not plane. It is, as far as a know, a pure displacement vessel. So, yeah, you need a tremendous amount of power to counteract significant components of both form and parasitic drag.
A Panamax container ship can have up to nearly 400 square meters of cross-sectional area under water. That's about 4,000 square feet. So, while it isn't exactly the same thing, only for the purpose of visualization, imagine a 100 foot long x 40 foot rigid piece of plywood fully submerged in water. Not try to push it forward at 20 miles per hour. Right. That's why they have to burn nearly a million and a half dollars of bunker-C fuel to get from Los Angeles to NYC.
Physics can be really inconvenient sometimes.
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
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
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.
I'd be happy to look at your calculations. My knowledge of hydrodynamics is somewhat limited, but I do have a fairly good understanding of aerodynamics and a lot of that stuff is transferable. I can't decipher your email riddle though - is [4:5] saying the 4th and 5th characters? Mine is leorampen (at) gmail.
The camry example was just an illustration of the power relationship of something moving through water. Nothing more than that.
The comparison of a container ship with 5,000 TEU (2,500 40 foot containers) vs. a train is, of course, different. And, of course, it isn't as simple as looking at cross-sectional area. That would be a gross oversimplification. Sometimes you have to assume that a cow is a uniform sphere of milk just to start to have some numbers to talk about.
Imagine a train design to carry containers at 200 miles per hour. Single file. So, now, the cross sectional area is that of a single container, which is very small. If the train is designed to minimize parasitic drag and all of the frictional components of the rolling system it could be incredibly efficient when compared to a ship pushing some 4000 square feet (400 square meters) of cross sectional area of water at 20 miles per hour.
And, as I have said multiple times, this isn't really solely about pure energy efficiency as much as a forward looking idea to that hopes to deal with the grotesque level of environmental pollution these ships produce as well as what might happen over the next 100 or 200 years with fossil fuels. One really has to start looking in at least a 50 to 100 year time scale to understand that what we are doing today is not sustainable in any way at all. To some extent, arguing the finer points of how much one displaces vs. the other and whether one solution is a few percent more efficient than the other is to miss the point.
I'll go ahead and send you a link to the data.
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.
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-p...
The claim is that just 15 of the worlds biggest ships pollute more than all cars in the world combined.