Posted on 09/19/2005 2:00:34 PM PDT by USFRIENDINVICTORIA
Giant kites that act like sails could bring wind propulsion back to ocean-going ships, reducing emissions and saving on fuel costs
IN THE first half of the 19th century, ships began to adopt steam engines, first alongside and then instead of sails.
{snip} ... the high price of oil and stricter pollution regulations are strong forces working to turn back the clock. Wind propulsion is coming back in a new form: kites, not sails. Next year, SkySails, a German firm based in Hamburg, will begin outfitting cargo ships with massive kites designed to tug vessels and reduce their diesel consumption. The firm estimates that these kites will reduce fuel consumption by about one-third—a big saving, given that fuel accounts for about 60% of shipping costs. {Snip}
But the SkySails approach does away with masts and is much cheaper. The firm says it can outfit a ship with a kite system for between €400,000 and €2.5m, depending on the vessel's size. Stephan Wrage, the boss of SkySails, says fuel savings will recoup these costs in just four or five years, assuming oil prices of $50 a barrel.
SkySails' kites are made of a type of nylon similar to that used in the sails of modern windjammers, but they fly between 100 and 300 metres above sea level, where winds are less turbulent and, on average, more than 50% stronger than the winds that sails capture. An autopilot computer adjusts the height and angle of the kite, the surface area of which can range from 760 to 5,000 square metres. When the wind blows too strongly, one end of the rectangular kite is released so that the kite flaps like a flag. A powerful winch retrieves the kite when necessary.
(Excerpt) Read more at economist.com ...
"Looks cool, but I don't understand how could you go up wind?"
I would think you'd have to tack, which to me would be difficult with this device (I can't see angle controls in the picture).
There are a number of freighters with what are effectively horizontal airplane wings (metal sails, really) on them currently in use to suppliment wind.
er, suppliment "engines."
What is old is new.
These kites, just like their sporting counterparts, can't tack through the eye of the wind without collapsing, just like a regular sail. Since there is no supporting structure, i.e. masts, they would just fall into the sea.
The kite or kites would not be efficient upwind because the ship would have to jibe to tack and the upwind VMG (velocity made good)of sailing at a 45° or more angle to the wind would add too much distance to the route.
Better to haul in the kite, crank up the RPM's and straightline the uphill stuff.
I think the idea is simply when the wind is with you, put up the kite and use less fuel, when it's against you, haul it in.
You can't tack with a 'sail' like that, sailboats and sailing ships which
tack need a keel and a sail which functions as an airfoil. A kite is only good for running before the wind.
Think of the children.
It's ok with me as long as I'm not the guy who has to hold it up and run with it to get it started!
"A kite is only good for running before the wind."
That's my assumption also, but without a detailed picture, I can't tell if they have figured out some clever way of internally changing the angle of airfoils inside the kite or something.
(That said, I am wondering what they would do with the slack in the rope as the kite began to luff. I suppose if they were quick about it, they could tact before the kite hit the water.)
Don't forgot the whole Sun adding energy thing.
It kind of looks like the controls are in the barrel shaped thingy where the main line splits into the multiple control lines. If there's a winch in there, it could change the angle of the kite. Given the projected size of the kites, I'd be surprised if they had trouble lifting a small winch system.
This sounds like a good idea, though I wonder how often the kite has to be fished out of the ocean. So long as the kite panels are going to be filled with a gas, why not helium instead of compressed air?
I did the modeling for global warming, too.
It looks like they are running before the wind. How do you sail into the wind?
It almost looks as if they, by using the variable tracting point, could tack.
Pretty much the same way an airplane flies, except sideways.
Seriously.
A sail is just an airfoil. You can literally make a good boat (albeit one that tips quite a bit) by putting a wing of an airplane in place of the mast.
Your photo makes some things clearer -- thanks for posting it.
Filling with helium sounds like a good idea. I sure wouldn't relish fishing 5,000 square meters of nylon out of the water!
Here is how it works:
http://www.boatsafe.com/kids/033199kidsques.htm
Very cool
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