Winglets on turbine blades - worth the trouble?

[Matrix1000]

I'm doing some googling and found a cool wind turbine design and it uses some neat winglets..

www.windkraftusa.com/WindLS.htm

I was thinking that it might be easy to cast winglets out of resin and glue them to the blades with some epoxy or something.. Would it be worth the time/hassle?

[RatOmeter]

Not sure at all in the context of a windmill. My sister (an aerospace engineer at Boeing since 1984) says windlets add a surprising amount of lift for an aircraft. In my (not-so-learned) opinion they might just add drag to a prop. From  what I've learned here and elsewhere and by rumination, you want to [1] maximize the lift [2] minimize the drag and [3] maximize the balance (other factors apply as well).

I don't know.  I'd better ask my sister.

[Oso]

Worth the trouble is a subjective question. The winglets should add to the performance, particularly in marginal wind conditions. Properly designed, they will also reduce the blade noise. The down side is that it may be a little tricky to "glue them on" while maintaining balance. They not only need to be identical in weight to maintain mechanical balance, but also installed at the exact same angle to maintain areodynamic balance.

Done right, it should be well worth it. Done wrong, it may screw up a perfectly good set of blades. Is it worth it, to you ?

[Ungrounded Lightning Rod]

Rather than bent-over winglets like that I'd try putting a little piece of airfoil on the end of the prop - serving as a winglet in both the upwind and downwind directions.  Maybe centered on the fin and as wide up-downwind as the width of the prop at that point.

Cutting the end of the blade flat, and routing a flat cutout the shape of your blade-tip in the winglet, should ease your mounting problems.  (Or use an asymmetric airfoil with a flat side toward the axis.)

The purpose of the winglet is to keep air from slacking off on the job, bypassing the outer part of the wing/fin/blade by running around the end (where is does nothing useful but still creates drag) rather than running around the side (where it does its job, pushing and pulling the prop like the air closer to the hub).  The last blade-width or more of the end of a fin is pretty much useless as a result - and in a prop this is where the most work COULD be done per unit of blade length, because it has the most swept area (so you'd get even more improvement than you do on an aircraft wing or control surface).  Putting the winglet on the end prevents this runaround and lets the whole blade get maximum aerodynamic effect - approximating a ducted-fan.

The gain is far more than the extra drag from the winglet.  So if it's not to hard to do it should be worth the trouble.  Then again, it might only give you as much gain as extending the blade by the length of the winglet, and it does put weight, and a joint, at the end of the blade.  So it should be somewhere between a wash and a gain.

One guaranteed upside:  It DOES solve the "What shape should I make the end of the blade?" issue.  B-)

[finnsawyer]

Putting winglets on the end of an airplane wing reduces or eliminates the vortices off the end resulting in greater lift.  A similar effect is seen for a plane flying close to the ground.  These are established effects.  So yes it will improve performance and can reduce noise, but is it worth it?  You can also place the winglets in the plane of the rotor.  This has been done with a helicopter resulting in a considerable reduction of noise (a stealth helicopter).

The problem with the vortices is that they create a larger wake that affects the following blades reducing lift.  Another way to reduce it is to make the end of the wing (blade) oval shaped.