Pipe sizes? It is made from Beer Cans... so Beer Can size I guess... is that your question?
CFM?? No idea, I Cann'd a small fan from a shop heater.
My shop is 13' x 26' and VERY VERY drafty.
All in all it ended up costing about $80... as I have it now... if you don't figure in the attic fan I bought. I did have it running on battery power, but the money you save is not worth the poor reliability On very cold days the battery tended to run a bit sluggishly, since the heat in the shop comes from the air flow, it was a sort of a death spiral. I had one of those "Polar Bear" solar attic fans running the air, but I paid upwards of $150 for it, and decided that it really is not worth the extra effort, for the attic, I think it is a great idea, but for winter it is designed wrong.
I ended up cannibalizing a fan from a cheap heater, I think I got it for $10 on sale at Lowes. What really makes this work is a small snap disk thermostat that kicks the motor on at 135 degrees, and off below 95, this way, when it is cloudy the whole unit will wait and charge up, then dump all the heat in the shop at once, instead of running the fan constantly. I put a "Kill-A-Watt" unit on it that measures energy consumption and came up with 25-35 kilowatts a month... but I shut the thing off during the week when I am not in the shop. At 11 Cents a kilowatt hour I didn't think I was breaking the bank.
It sounded like it would be GREAT to me, but the cloudy days produce very little. The trees on my border also don't help. I would say if you are going to mount this on a pitched roof facing south, it would be worth it, on a flat shop roof, it is worthless, and on the side of the shop where shadows fall it is ok, but hit and miss sometimes.
Does anybody know how to measure or calculate BTU's? That would make it a whole lot easier to compare.