Few people would argue that having a rooftop wind turbine could help offset your power bills. Your neighbors, however, might not appreciate the sight of a windmill on your roof, nor would they like the sound of its blades whistling through the air. Don’t give up on the idea yet, though, because British inventor Rupert Sweet-Escott has come up with a product that he claims addresses those problems. His Secret Energy Turbine (SET) looks like an ordinary chimney stack and is boasts almost completely silent operation.

The SET has vertically-mounted blades, and two opposing magnets to help keep it spinning. As the blades catch the wind and start to spin, they form an airfoil by means of boundary layers. These boundary layers are the same as the layer of air that moves over an airplane’s wings, and the result is a faster-turning turbine. The uneven current it generates gets organized by an electronic load controller, then fed into one or more battery packs for storage. From there, a sine wave inverter converts it to a regular household voltage, and you can use it for whatever you want.

So, just how much energy does the thing produce? It depends on how windy your area is, and the size of your turbine. The SET website has a chart showing approximate energy-generation for the three sizes, which is shown below.

It's claimed that a 400mm SET will generate enough power for the entire lighting circuit of an average household using low-energy bulbs. What isn’t clear is how long it could keep those bulbs lit, but hey, every little bit counts. The turbine requires a wind of at least 8 mph before it starts to produce any current, and has reportedly withstood winds of up to 90 mph.

The SET is available online, and it ain’t cheap. Prices range from the equivalent of $US1,145 for the 300mm model, to $1,716 for the 500mm. You will also need a load controller, one or more batteries, and the services of an electrician. Of course with something like this, it isn’t just about saving money. If the figures are to be believed, a SET could definitely lower your carbon footprint.