Before you folks start your flame wars - I think 100kW for size and 5 years 95% uptime is a successful mill. Please post pictures in a JPG format and give location and ownership of mill if possible.

My own motto is "many problems must be identified before they can be solved". It takes good analysis along the lengths of wind turbine blades inch by inch to understand how they are driven by the wind. The haste wind energy has often shown to get some current flowing into the batteries with something easy and cheap, being that the wind is free, is just so much of "placing another point on the graph", or, in other words, the "TTTT" approach, i.e. "try this, try that".

The verticals are subject to an effectively reduced blade swept area since the rotor is not as efficient at its outermost fringes to the right and left as it is in the center dead on and everyone has always wondered why they cannot perform as well as the horizontals on a swept area basis. Ordinary calculus math finds a factor, 2/3, which must be applied to adjust for this. Verticals rotors must be one and a half times as large in their areas seen by the wind, therefore, as the horizontals rotors are just to start with.

They also have the serious handicap of requiring that the blades travel straight upwind right into the teeth of the wind during a portion of their rotation. Not only does the laminar flow see a high parasitic drag there but the slightest amount of flow separation and turbulence produced is directed straight back and acts as a brake, unlike the horizontals, wherein turbulence and stalling directs itself at right angles to the blade motion, keeping it from being as great a factor in inhibiting performance.

As one can see from the images of these Dermond turbines, the bent blades allow the stresses to be managed with blades that are super thin, something of an answer to the drag problem. Thinness doesn't work without blade chord width and so they have good blade chord width also.

Everyone on this discussion list who has followed my own comments knows that I am doing some work with small rotators, both of the horizontals type and verticals. I can mention here that recently the verticals rotator, whose rotor arms were purposely reduced in length to 9 inches long (rotor diameter 18 inches) ran at a high speed in 10 mph winds, fast enough to light the LED lights placed on the 3.5 inch diameter axial flux 3 phase PM alternator (purchased from Ed Lenz of WindStuffNow). It gave everyone here confidence that this effort is going in the right direction. It was really interesting to see these 22 inch long thin, doubled verticals blades, relying on only the lift principle turning at about 300 - 400 rpm. Photos taken with the digital camera, which has progressive scan (the image part above is at an earlier time than the image part below), show "twisted" blades due to this photo effect on their motion.

This particular test was done as a result of the confidence obtained from the previous test on a horizontals rotator with similar thin and doubled blades, which likewise ran at a high speed, higher than expected. It goes like that, one test providing support for the next.

These are just small rotators and only intended to light some diode lights or, later on, charge small Ni-Cad batteries for outdoor use and not for powering a home. We go where the electrical utilities are not able in these small usages. More "power" to McKenzie Bay and Dermond, though.