The excel spreadsheet wind power design.xls contains graphs which answer the question, ‘how much energy can I hope to generate with wind turbines of different sizes.
Useful Links
American Wind Energy Association website
http://www.awea.org/
Danish Wind Industry Association’s website
http://www.windpower.org/en/core.htm
The vertical axis wind turbine
http://www.awea.org/faq/wwt_basics.html#What%20is%20wind%20energy