Comments on: WindLift Harnesses Kites for Off-Grid Power

By: chris reid

chris reid — Mon, 23 Feb 2009 16:03:37 +0000

so what's the formulae for the relationship between, wind speed and the surface area of a kite (supposing the kite is,say flat). is it the same as for a turbine ?

By: RogalloFan

RogalloFan — Mon, 12 Jan 2009 03:02:40 +0000

Burt, a power kite takes advantage of its relative velocity to the wind and these highly efficient kites (they are more like flexible wings) move quite rapidly, just like the blade tips of a large wind turbine move 8-10 times faster than the wind speed. In a 10 kph wind these kites move 40-50 kph as they sweep back and forth across their power zone which allows them to extract energy from large swaths of oncoming air. So the maximum 800 watts/sq meter is correct, it is just that these kites sweep through tens of square meters every second. Also, the 40% Betz factor that you mention really only applies to turbines. Free flying wings can theoretically be more efficient.

By: Katie Fehrenbacher

Katie Fehrenbacher — Thu, 23 Oct 2008 02:53:39 +0000

Burt, The founders said everything in the post was correct, but I'll circle back with them on that number and see if they have any clarifications. - KF

By: Burt Hamner

Burt Hamner — Thu, 23 Oct 2008 02:36:31 +0000

This article has incorrect information. It says "The kite provides a significant amount of energy — about a kilowatt per meter for a 5- to 20-meter kite"

This is nonsense. The maximum wind power density is 800 watts/sq meter in Class 7 winds - US Dept of Energy standard info. Turbines cannot in reality be more than 40% efficient. That's 320 watts per meter, not 1 kW. That's basic physics.

Either the post author is in error or the developers are un credible.

I am developing micro hydrokinetic turbines for in stream flows, and have spent 2 years working on power estimates for various fluid power technologies. While I am not the world expert, I know enough basic physics to call out egregious errors when I see them.

By: CNCMike

CNCMike — Wed, 22 Oct 2008 17:18:07 +0000

I've seen number of this type of article but I have not been able to find a good explaination of how it generates electricity. Is there a good reference anywhere so I can learn more about this?

By: Deep Patel

Deep Patel — Wed, 22 Oct 2008 15:32:06 +0000

this is a similar Magenn Power high altitude wind turbine, which is much further in their development process. These types of "flying" turbines sound great for rural areas, I am not sure about urban settings. The only problem with high altitude wind turbines is you need a special permit from the FAA if you are planning to fly one, which depends on how far you fly it up. reguardless this is great innovation in the wind turbine sector. 10kW is a lot of juice and for $5,000 the cost per watt is much lower then solar power.