Tom, I mis-spoke, if you have an e-fan and a mechanical fan that both move the same amount of air, the e-fan is going to require less "Power" (not air flow). So, sorry about the confusion.
As for the mechanical fan efficiency, it was mentioned in the article that was linked that the mechanical fan doesn't have to convert from mechanical to electrical, back to mechanical, therefore it is more efficient. Like I mentioned, that is not quite the case. Power out over power in is an accurate measure of efficiency. It doesn't matter how you get it from beginning to end, but how much in the end you can get out. The blades of a mechanical fan are very inefficient, making the overall operation of the mechanical fan inefficient. I liken that to having a pallet of bricks that you need to move from 1 point to another. You can move it brick by brick (the e-fan) or you can try pushing the whole pallet (mechanical fan). Both ways can work, but some ways are better than others.
Mindgame, enjoying your adventures out at Kaena Point? Looking at your pics, I have some very similar to yours when I had Nukie out there, playing in the mud. OH those were the days.
