I think that your too rigid in your thinking. With a 6" x 4" paddle wheel design fan blade 50% of which is inside the tunnel, the resistance would be negligable vs. the potential power production. We all understand the prior concept noted but this is an existing exhaust fan with a harnessable...
Say I have a commercial building that has a 24 inch diam. exhaust fan that is blowing approx 40 mph wind out of the building. I wonrder if I can make good use of this wind by mounting a 24-26 inch pipe that may be 6 to 10 ft long on the outside of the building. I imagine cutting out sections in...