Skip to content Have you ever looked out across the rooftops of a city and idly gazed at the infrastructure that remains unseen from the street? It seems [varunsontakke80] has, because here’s their project, harvesting energy from the rotation of a rooftop ventilator . The build is a relatively straightforward one, with a pair of disks with magnets attached being mounted on the ventilator shaft inside its dome. A third disk sits between them and is stationary, with a set of coils in which the magnets induce current as they move. A rectifier and charge circuit completes the picture. This appears to be part of a college project, but despite searching, we can’t find any measure of how much power this thing generates. We’d be concerned that it might reduce the efficiency of the ventilator somewhat. There will be an inevitable tradeoff as power is harvested. Still, it’s a neat use of a ubiquitous piece of hardware, and we like it for that. This hack is part of our 2026 Green Powered Challenge .…