Imagining the Vertical farm

One of my favorite blogs is the BLDG BLOG. They've got a post this week that makes me scratch my head though. Check out the "Vertical Farm" write up here - it describes the necessary components to build an urban-scale, self contained structure for living and agriculture.

Yet, they ruin it for me with those silly turbines on the top...Any fan of Wind-Sail or vertical axis turbines will immediately see the folly in spending all that precious rooftop real-estate to get such measely swept area from those horizontal turbines. are those fixed in wind-direction too? so you only get 1/4 of the turbines working at any one time? clearly, a well designed, much large, single omni-directional vertical turbine could get 4x-10x more power from the same footprint.