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Edited on Thu Nov-09-06 05:38 PM by NNadir
There is a doppler shift of about 1.6 parts per 100,000 if your tip blades are moving with respect to the light source are moving at 50 m/s.
OK, that's a joke and not a very good one.
Two practical problems I see is that ultimately the solar cells would be scratched by small particles moving in the wind, reducing the efficiency with which the light is transmitted. One might also have to worry about the mass of the cell flowing under the forces involved in windmills with very large vanes. I don't know all that much about the technical details of solar cells, but it would seem that thickness of materials is a factor in their performance. Soft metals and glasses would tend to flow over time when subjected to the forces involved in very large vanes moving at a fair angular clip. In addition, one would have brushes or other transmission devices that would suffer wear in transmitting the current from the moving blade. The blades have a relatively small surface area, and depending on the angle of the sun, the upper part of the blade would shade the lower part of the blade.
It would seem to me, given that the world production capacity of solar cells is far smaller by vast order of magnitudes relative to the amount of attention paid to to the subject of solar energy by the general public. Once all of the world's roofs have been filled with solar cells - as will surely happen in California in the next few weeks now that Governor Hydrogen Hummer has been returned to office - we can start worrying about where else to put them. In fact though, the world's production capacity is insufficient to fill even a tiny fraction of the world's energy demand, and thus a tiny fraction of the world's roofs. In fact the solar industry is not likely to be challenged by running out of space. It cannot fill the space already available to it. Typically the solar cell manufacturing industry can produce, in a given year, a few thousand megawatts of "peak" power on the entire planet. It will be a long time therefore before we have to start worrying about the space in which to put these cells.
Let us assume that the world's solar power production is 10,000 MWe (peak) per year. It isn't, but let's pretend it is. If we say that the world's PV cells have 30% efficiency overall and that the solar flux is 1300 MW/m2 we see that the total area that could be covered in a single year is a square about 5 km on a side each year. We still have plenty of room to fill before we need the space on the blades of windmills.
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