efficiency and economics

Hey EVMers,

I be interested on people thoughts on the efficiency and economics - BTW the economicson the website sound fantastic
I'm just curious why the tower need to be concrete given that the purpose is just to funnel the air (I thought a very lightweight material would make sense) but just my uneducated though.

With regards efficency I understand the principles but not sure how efficient the transfer of radiant sunlight into air motion then to electricity is - I guess the cost of covering the trapped area per metre squared is very low so the effiency may not need to be that high - also how does tower height increase effiency ?

I'm just posing these questions for discussion.
Maybe no one knows but you would think think there would be some modelling to anwser these questions by now ? maybe not..

Cheers,
Peteai