6 Egypt Silk Mill 2pi wind turbine ; revisions 2 ; 14 April 2011 .

These figures revise and extend the posts of 22 March and 4 April .

The changes are : an effective tripling of the height of the arch,

with an accompanying addition of seven turbine cores ;

and the redesign of the arch's feet, with accompanying revision to its base .

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Rotated views of the turbine-system are shown around the margin .

With the exception of scale, the number of cores, and the feet, the arch is the same .

The inner margin's set of images is a rotation of either of the feet ;

as are the upper two of the images flanking center .

Geometrically, the feet are built by expanding the arch's cross section,

while at the same time leveling its cant to the horizontal .

Such three dimensional filleting is, i believe, essential to the durability of the arch ;

(and may offer slightly better aerodynamics as well) .

However, it uses a larger turntable than i had modeled previously ;

as is shown from above and below in the lower images flanking center .

It now seems likely that this turbine-system will always have a larger footprint for its height and wing area than a standard one .

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This can be mitigated, to some extent, by centering the arch on a smaller, unskirted turntable ;

to be turned by motors to face the wind .

However, a large footprint may be of considerable value .

Many farmers, who draw irrigation water from an aquifer, face declining water tables and the salination of their soil .

At the same time, climate models indicate that rainfall patterns will increasingly include floods, drought or both .

If, below the turntable and skirt of these systems, were cisterns,

they could be used to hold some of the water which would otherwise run off during floods .

Purified or desalinated using the turbines' surplus power, it could be held ready for irrigation during drought .

Increment by increment, such preparations could reduce the severity .