For anyone without a spreadsheet program,

If you need to see spreadsheets that have been done in excel, quattro pro etc. you can download the excellent OpenOffice suite (free) which will work on Linux or Windows boxes:

http://www.openoffice.org/

Thank you so much for posting the pic rather than telling me where i can get more software I don't need so I can look at one chart.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

  The taper is because the lift of an airfoil is proportional  to it's relative velocity squared a high speed rotor can have very narrow blades or low solidity. The inner portion of the same rotor looks the same as a low speed rotor of smaller diameter and thefore requires (mathamatically) a higher solidity.

or

 Since a turbine blade at half span has a relative speed close to half of the tip (not exactly half, do to the change in relative wind angle) and lift is proportional to speed squared the planform very nearly follows the 1/r relationship that you noticed.

 This is all based on finaite analisis and Betz theory for each "ring" of air swept by the blade section in question, and assumes that the turbine runs at a constant TSR

 "Further, I note that the big commercial mills don't do that".

 Really! I have never seen a large wind turbine that did not have tapered blades. The root is normally very compromised for economic and structural reasons. (Take a look at Enercon's new turbines to see wide and twisted roots, and read their claims to higher efficiencies). Also many of the older utility scale turbines drive induction generators and run at near constant RPMs and therefore variable tip speed ratios which would effect the design planform. The current trend, however is toward variable speed, ei constant TSR.

Make the wind fun!

Victor Creazzi
Aerofire Windpower
www.aerofirewind.com

With small high speed props, the loss due to bearing friction and also iron loss in this case is more than it can produce in low winds so the low wind performance is poor. Results in high winds can be good and you get nice big power figures for sales literature. This can be quite useful for boats at sea or in high wind areas to supplement solar, but as a general power source even in good wind areas it will be poor.

For good results in low winds with a small prop you need a lower tsr so that bearing friction is not a major issue and you can't afford the iron loss of a slotted iron core, that is why the dual rotor designs do so much better. It is very difficult to have the best of both worlds so a dual rotor matched to low winds will not be as impressive at 30mph.  The shape of the power curve above 15 mph is much easier to match than the shape from 5 mph to 30. If you use star delta or similar you can do better but if you optimise for one condition it is usually wrong for the other and it spends a lot of time in the wrong mode.

If you want steady power often then dual rotor is the way to go. If you only want the higher power and want as much as possible when it is there, then matching to high winds is better.

Find the open circuit voltage of the generator and the short circuit current at three points on an RPM curve.

Find the maximum torque at RPM produced by the turbine at the average wind speed.

Beyond that, the characteristics are complicated. A good test would be driving that vehicle mount setup at the average wind speed and measuring ampere hours per hour into a fairly large battery that is discharged (10.5V) at the start of the test.  That would a good general approximation of performance and might be a good comparison method. One has, after all, the greatest need for energy and recovery when the battery is discharged and the time to recharge would be a key installation parameter.