DIY: Roof Vent Wind Generator

Factor in elements that will reduce the efficiency of your installation. Friction and weight are critical considerations. The pin bearings on which roof vents rotate -- those vents that do nothing other than extract air from the roof void -- typically cause very little friction. However, driving a spindle to deliver motion to a generator hikes this factor considerably; turning that generator increases resistance still further. For this reason, preexisting roof vents are unlikely candidates for conversion; new, larger vents should be installed according to the manufacturer’s instructions.

Use a vertical-axis wind turbine -- abbreviated as VAWT in industry-speak -- so that there is no need to build complex right-angled drive mechanisms with multiple, interrelated shafts. The electricity generated is directly proportionate to the rotor sweep, along with wind speed; larger rotors with larger vanes spin further, faster than smaller rotors with small vanes, and can therefore turn the generator faster, and with more force. This equates directly to the production of more electricity.

Site the vent as close to the ridge of a peaked roof if possible, near a gable end, exposing it to wind from any quarter. Use vanes that are omni-directional, meaning that they will rotate the spindle no matter which way the wind is blowing. Avoid vents with angled vanes that only catch the wind in one direction; these falsely limit the amount of electricity the installation can produce.

Connect a spindle to the roof vent that will transfer the wind’s kinetic energy, as harnessed by the rotor, down to a generator located away from precipitation below the roof. Connect the generator to a battery or bank of batteries that can store the electricity until it builds up to a useable level.

Install a group of vents and generators, just like the multiple wind turbines of industrial wind farms, to increase productivity without creating an unsustainable weight loading on a focused part of the roof. A proprietary diode-controlled collection system is required for multiple-source installations, itself then connected to a transformer that makes the electricity into a form that can be stored and discharged by the battery.