Wind Power from a Whole House Fan?

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Illustration by Fotolia/kelttt
Don't bother trying to capture wind energy from a whole house fan. It doesn't generate enough.

I have a whole-house ventilating fan mounted in a hallway ceiling in our 1,200-square-foot house. If possible, I’d like to install a small propeller-driven wind generator to take advantage of the output air from the ceiling fan. I’d hope the unit could produce two amps of 12-volt DC electricity to charge a battery bank.

Could you recommend a propeller, generator, and configuration to maximize the benefit of the fan’s exhaust air?

You can’t use the output from an attic fan or a whole-house fan, for a couple of reasons. First, the output, while seemingly significant, is very low-power wind. Second, and more important, the operation of a whole-house unit depends on unrestricted air flow through the building (in the windows and doors, and up and out the attic vents). Any blades would block the flow and set up back-pressure interference. Sorry, but it just won’t work! 

Alternative-technology consultant Joel Davidson puts out the PV Network News (subscriptions are $10 a year).