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Computer-Controlled Cargo Sailing Vessels Go Slow, Frugal
An anonymous reader writes "Big container ships are taking it very slow these days, cruising at 10 knots instead of their usual 26 knots, to save fuel. This is actually slower than sailing freighters traveled a hundred years ago. The 1902 German Preussen, the largest sailing ship ever built, traveled between Hamburg (Germany) and Iquique (Chile): the best average speed over a one way trip was 13.7 knots. Sailing boats need a large and costly crew, but they can also be controlled by computers. Automated sail handling was introduced already one century ago. In 2006 it was taken to the extreme by the Maltese Falcon, which can be operated by one man at the touch of a button. We have computer-controlled windmills, why not computer-controlled sailing cargo vessels?"
The other story of the 20th Century was "Just-In-Time", which meant reserves and stockpiles have been kept as low as feasible. That would be another factor limiting acceptance of sail - we'd need larger stockpiles to ride out any delays. Honestly though, with satellite imaging, and computer control - there's no real reason sail travel should be any less controllable and predictable than using fossil fuels. And at the speeds involved, there wouldn't even need to be any major code to do image processing and interpretation on the ship itself (though with the computer needed to handle the rigging, and the need to monitor against potential collisions, should be enough to actually do the planning on ship... but coordination would be better from a central site and general directions relayed via satellite.)
Neither computers nor crews pilot vessels into harbours. Harbour pilots do.
UNIX/Linux Consulting
Its not just about fixed scheduling, its about weight and economies of scale. Sails are no longer viable with the size of the ships transporting cargo. The smallest ship I've dealth with holds 300 20ft containers with an avg weight of ~30,000 lbs. Some can be loaded with over 200 million pounds of cargo. I don't even think we have the materials developed to make sails for those physically possible.
The only practical application of sails for cargo ships is augmenting the engine, which we've seen before here on slashdot (too lazy to find the link).
"Dear mister pirate. This ship is equipped with 'ROMG'. This stands for remote operatable machine guns.
Way too messy. If the computer had the ability to control the ventilation system and hatch locks, the computer could lock them inside. That is when the nerve agent would be released. Post the video of those bastard's slow, agonizing death on YouTube. That would make them think twice about jacking ships.
Dependable schedules are one reason, the other big reason is that sails interfere with loading and unloading the boat.
Modern shipping extensively uses cargo containers that are rapidly loaded and unloaded using cranes. This advance has drastically lowered the per-unit costs of shipping freight in the last half-century (check out the book "The Box" for more details).
If adding sails makes it difficult to use a crane to unload containers from the deck of a boat (likely, imo), then it would make the per-unit cost of shipping skyrocket.
You can not move forward by capturing energy being used to push you backwards. To move forward would require more than 100% of the energy that you're capturing. It doesn't work.
Those numbers only work when your personal interest rate is 0, which is rarely the case.
Realistically, you need to adjust for the time value of money. ($100 now is worth more than $100 27 years from now, as I could make interest off of it)
So, if we assume that the savings are every month, with a 3% interest rate compounded monthly, we'd have (12x27) payments of about $49,617 each with 0.25% interest per period:
PV(A) = (49_617 / 0.0025) * ( 1 - (1 / 1.0025**(12*27) ) )
Which works out to just over $11 million. The install cost would have to be less than this, to deal with the reoccurring costs of maintenance of the new system.
Oh ... and if the interest rate were 6%? That $11mil estimate would be cut to under $8mil, or about 1/2 of your estimate. In a good market where we might be able to make 18% return, over 27 years, it's worth less than $3.3M.
Now, I don't know how much container ships cost, but if I can add another ship and move more containers, that may give me a better benefit for the same cost.
(and, I know you later said that the actual savings were higher -- but the point is, you should _never_ just multiply reoccurring costs or savings by the number of periods to get the equivalent present value, especially for periods of years.)
Build it, and they will come^Hplain.