As I see it, we have three variables:

• Inclination (the straighter the sun hits the athmosphere, the more penetrates - thus more radiation hitting your skin closer to the equator)
  
• Clouds (more sunny days gives more output)
  
• Transmission

I think the main factor would be that of placing it in a desert, that is a place with little or no clouds. The difference in inclination is not that great and HDVC is very good. Then again I do not know how much cloud you would have to put up with at the best sites in Greece, Spain and Portugal (abbreviation GSP?).

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