Football Field-Sized Kite Powers Latest Freighter

coondoggie writes to tell us that a new freighter set to launch in December will be receiving a hefty dose of power from a kite the size of a football field. The 460-foot ship, owned by the Beluga shipping company, hopes to see as much as a 50% drop in fuel consumption during optimal conditions. "The SkySails system consists of a towing kite with rope, a launch and recovery system and a control system for the whole operation. The control system acts like the autopitot systems on an aircraft, the company says. Autopilot software sends and receives data about the sail etc to make sure the sail is set at its optimal position. The company also says it provides an optional weather routing system so that ships can sail into optimal wind conditions.The kites typically fly at about 1,000 feet above sea level, thereby tapping winds that can be almost 50% stronger than at the surface. "

Comments

30-50% is more like it

[Quadraginta]

All they need is to have a moderately strong, steady wind that is abaft the beam. Plus good enough weather that they don't risk the kite and its hardware. If you sail the traditional sail-era trade routes the wind is abaft the beam quite a bit more than 50% of the time, the wind is steady at 1000' in the open ocean pretty much always as long as the weather is good, and you can supply your own finagle factor for how often the weather is good.

Frankly, I think the major limitation on any kind of sail power has been crew cost. Big freighters run with tiny crews these days, and often not very well trained and not especially reliable, except for the top few officers. Getting a crew that can handle a big sail competently, without endangering the cost of the apparatus, sounds expensive. But maybe they've got a robotic, computerized control system that can eliminate that problem.

This is an "update" from a July, 2006 article

[puppetman]

The original article is here:

http://hardware.slashdot.org/article.pl?sid=06/07/08/1735227

The original article claimed a 33% savings in fuel costs. This new article claims a 50% savings under optimal conditions. Interestingly, the greenhouse gas savings are only 10-20%. Where is the logic in that?

Or better yet why?

[LWATCDR]

Why put them on the sail. What are the odds that the sail will be pointing at the sun... Why put them on the sail/kite at all instead of the ship? Why risk them getting lost if the sail goes into the water or the cable fails? Why try to make the as flexable as the sail so it is easy to store in case of storm or headwinds? The electrical load of a freighter is actually pretty small compaired to the propulsion load. So are you going to carry a big honking electric motor to use make in to an hybrid? If so why care the extra weight and drag on the screw shaft for something you could only use for a few hours each day?

Why not? Because it wouldn't really help in any way and would cost a lot of money.

Re:Reinventing the wheel, and getting $$$ for it

[DerekLyons]

Furthermore, the kite has upward lift, which helps pull the bow out of the water. This makes it feel less of the effects of waves, smoothing out the ride a bit.

Unless they put a lot of [heavy] steel stiffening in, the ship will flex at the attachment point rather than lift the bow. Ships aren't rigid.
 
On top of which, even if the kite were attached at the eyes - you don't want upward force. Upward force doesn't contribute as much to propulsion as lateral force.

Re:Getting $$$ for vaporware

[necro81]

Thus this 50% efficiency figure seems to me to only apply to one direction of travel. Overall, if one uses the same amount of energy in both direction then that's only a 25% savings. Not bad perhaps.

I don't know about you, but a 25% gain in efficiency seems pretty good to me. I wouldn't mind being able to get by on 25% less electricity or natural gas at home.

The real question isn't necessarily the efficiency gain in percentage terms, but whether the fuel savings can offset the cost the kite system. No. 6 fuel (which most ships use) is relatively cheap, because it is one refining step above tar. Seriously, it is really nasty stuff, and doesn't burn cleanly at all. A big cargo ship will go through thousands of gallons of it a day, maybe in just hours. If you can use 25% less fuel in a year, that starts to look like hundreds of thousands of gallons of fuel saved per year, which in turn could mean hundreds of thousands of dollars a year in savings.

Related development

[XNormal]

Makani power are planning to generate electricity using high altitude kites - at a cost competitive with coal power.

There's very little information about them for now but they did get a $10M investment from Google. Here is what Cringely dug up about them from old Usenet posts of one of the team members.