| SkySails 5X More Efficient Traditional Sails |
| Written by Hank Green | ||
| Monday, 18 August 2008 | ||
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Wind powered maritime travel isn't exactly a new idea. Actually it's a really freakin' old idea. So it's easy to make fun of the "breakthrough innovation" of SkySails. SkySails has been adding giant kites to the front of barges in order to reduce their fuel consumption by as much as 20%. The systems pay for themselves quickly, and could potentially save massive amounts of fuel...but are they better than regular sails? Turns out they are. Per square meter of sail, they produce five times more energy than traditional sails. Depending on wind conditions the 160 square meter kite can generate about as much force as an Airbus A318 jet engine. That's pretty awesome. Of course, the more sail you use, the more energy you get, but getting the sail up and away from the turbulence caused by the body of the ship is certainly worth the effort. Of course, now we're just waiting for them to get the systems installed on a significant percentage of shipping vessels. And, well, we might be waiting a while. Via SkySails and TreeHugger.
Comments
(27)
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written by Michelle , August 18, 2008
Going by the photograph, it would appear that the sail would also lift the front of the ship a bit. Is that a good thing or a bad thing?
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written by Chris , August 19, 2008
I would think having the nose come up is a good thing. In aviation (air and water are both fluids with the same characteristics) have a downward force on the tail and upward force on the nose causes the aircraft to use less fuel.
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written by Carl , August 19, 2008
Yeah, you want as much of the bow out of the water as you can get. That's why hydrofoils are so fast and efficent.
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written by Fred , August 19, 2008
Fluid dynamics is a bit different, but think of it like trimming out in a speed boat. The faster the boat goes, the higher the front-end raises, essentially skimming the surface of the water. This reduces the drag normally imposed by pushing against the water, now you aren't pushing against anything.
So even if it does lift, however little it might, it does help in the picture overall.
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written by Tony , August 19, 2008
I've been a professional kite flier for over 20 years. With the kite directly above would cause lift but not increased pull. The power zone in the wind window would be at roughly 45 degrees up from the horizon line. This would cause the most pull and not lift.
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written by Stefan , August 19, 2008
What exactly does a professional kite flier do?
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written by matt , August 19, 2008
I'm going to go out on a limb here and suggest a professional kite flier might fly kites.
Wind sails
written by Jim McDish , August 19, 2008
Pretty awesome idea as long as you are on a down wind run. Kind of like a spinnaker on a sailboat, very effective.
RD www.decrypt.net.tc
haha
written by Max , August 19, 2008
They fly kites, professionally.
Dumbass.
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written by eric schmidt , August 19, 2008
I don't believe this claim at all. Regardless of how efficient the sail is, look at the angle of the line towing the boat. That is the only thing that matters. It is nearly vertical (I exaggerate a bit, but you see). How can that be at all effective in providing forward force?
Reply to Eric Schmidt
written by Jonathan Prevost , August 19, 2008
Eric, even if the sail is in fact pulling the boat up vertically, that will still help, even if just marginally. Density of water vs air is the reason. Pulling the boat out of the water reduces it's drag through the denser material. Sure it doesn't help much but it does help. If you want an analogy; think of a swimmer doing the breast stroke where their hands and body are almost always submerged vs any of the other strokes that have the swimmers arms out of the water.
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written by Future Prokiteflyer , August 19, 2008
Wait..you fly a kite, and get a paycheck? No phone calls, no cubicle, no annoying coffee drinking habits from over the wall cube mate? Where do I sign?
The sail in the photo
written by Jim Land , August 19, 2008
Don't make too much of the sail in the photo (which isn't doing much to propel the ship). For best propulsion it's farther out and higher, giving an angle of the tether for much less lift and more forward force. See the other photos on SkySail's site, http://skysails.info/index.php?L=1
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written by a person , August 19, 2008
erm, this is obviously the "docked" position. in use, they fly these things hundreds of metres in the air
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written by vasa , August 19, 2008
You're forgetting a key thing from way back in physics. Remember the question of whether its better to pull a sled at an upward angle or a downward one? By pulling upwards, you reduce the normal force which reduces frictional force, or in this case drag. If you're getting an opposing force of a jet engine, you're significantly reducing weight, thereby reducing the amount of fuel required to push the boat.
Lift not always good
written by Matt , August 19, 2008
I just want to clarify to the person talking about the speedboat bow lifting the faster it goes being beneficial. This is actually false. When the bow lifts higher the boat becomes less efficient because the stern settles lower to displace the water the bow is no longer displacing. This acts as a wedge pushing water. Once a certain speed is reached however the boat again levels out "planes" and skims across the water at a level speed. When a boat is level it is most efficient. This only applies to small boats however, the dynamics of a ship are entirely different.
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written by kitetricks , August 19, 2008
I'm not so concerned about the nose up drag problem. I would just attach one kite at the tail end and one on the nose end.
If the boat lifts clear out of the water .... it's a bonus.
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written by wayne , August 19, 2008
why not have an automatic system that deploys and runs the sail.
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written by kc , August 20, 2008
But wont this work only if there is wind blowing from the back of the ship to the front (tail wind?).
I wont work if the wind is blowing the other way from the head of the ship to the tail (head wind?).
Idiots
written by james , August 20, 2008
If being green makes me an idiot count me out because it seems that 99% of these comments are made by complete and utter retards.
1. The photo above is not an action shot. Obviously the sail is not providing power at that angle. 2. Yes a sail like this can provide lift but considering that the sail has to be proportioned to the size of the boat I can safely say that it wont be lifting the boat by any appreciable amount. 3. The system is full automated by computers that control the sail and ensure it's running at maximum efficiency.
Don't judge by the picture
written by Craig , August 20, 2008
You can't judge by the picture. When in use the kite is at very high altitude and that doens't make a good picture. The picture was taken either during a launch or take down. Yes, wind direction is a consideration. But at 500 ft, the winds are much stronger and can be from a very different direction than the surface. Thus you can gain a benifit when you wounldn't expect one.
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written by Al Boosh , August 20, 2008
To re-iterate someone else's post stop guessing and go the manufacturer's website: http://skysails.info/index.php?L=1 What was that saying about a vid was worth a thousand Euro? Or, something like that?
Click on the two videos and you'll see how the ingenious system works. Those Germans sure know how to be green!
Effective angle of the wind.
written by Mr. Tn. , August 21, 2008
Hey Tony, pro kite guy.
Maybe you can answer this question. With a traditional sail boat rig, you can sail at about 45 degrees off the wind. That is, if the wind comes from 0', you can sail up to either '45 or -'45. What is the range of a kite? I'm guessing you can't sail as close hauled, but maybe you can.
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written by Mumia , August 29, 2008
If we say we can use this system in only 180 degrees (wind comming from the back of the boat and up to 90 degrees to each side) I would still say that its brilliant, we just have to find the old seamaps and plot a course following the tradewinds, it might take a day or two longer to get to where we want, but if we save 50 tons of fuel along the way, I would think the cost saving is obvious, after all shipping is about making money. Now for the power of the kite, even if it produces the same as a jetengine its still ships with 1000-100000 displacement tons we are talking about here, so I do not think they will be many milimetres higher in the water, now if we could build ships that where lighter in the water and had less drag, we could even get there faster than with the old ships with fossile fuel engines that goes deep in the water and have extensive drag ( designed when fuel was cheap and not really a concern in the overall cost ).
If we could add a few windmills to produce electricity to drive the boat forward also, we could be looking at even more savings, these would of course have to be computercontrolled so they dont try and get power out of wind working against the forward movement of the boat.
Great Idea
written by Chris , September 27, 2008
I appreciate the idea, it really makes sense. The kite flyer who left a comment has a point though. The lift would work against the pull power. But if the bow is lifted out of the water that's a good thing.
Chris from http://www.boatpride.com
All points of sail
written by Richard Mercer , November 15, 2008
The Skysail is more than a spinnaker. It is not for just down wind sailing. It can sail on all points of sail just like a sailboat.
They say a ship can be retrofitted with it for about $250,000 which is peanuts when you consider that spot prices for leasing large dry bulk cargo ships was up to $125,000 per day, last year. There is another company, Kiteship, that's U.S. based doing the same thing.
points of sail 2
written by Richard Mercer , November 15, 2008
If you've seen pictures of or seen the huge sailing yacht, Maltese Falcon, it has a rig originally designed for cargo ships in the 70s.
It's called a Dynarig. It's a modern version of a three masted square rigger. Keep in mind that they won't be sailing the ship with a skysail, they will be motor sailing, with the engine running slow. | ||
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