The elements of bright green home design are rapidly coming together, and it's looking increasingly clear that high-efficiency consumption and home microgeneration are an ideal combination. We've looked at residential efficiency quite a bit recently, so let's turn again to the home power generation side. Of the three main sources of clean renewable power -- solar, wind and ocean (tide/wave) -- two are reasonable options for the individual buildings (sadly, home ocean power appears to have limited application). For solar, we can go with building-integrated photovoltaic shingles or wall/window units; for wind, we have "rooftop" (but often wall-mounted) turbines.
While most small wind turbine developers have focused on small towers for rural users, two UK-based manufacturers -- Windsave and Renewable Devices -- have been working on micro-turbines for the urban environment, and have been working with utilities and developers to get wind power into buildings. These efforts are starting to pay off, and in more than just number-of-roofs. Last week, the "Swift" micro-turbine from Renewable Devices won the "Ashden Award for Sustainable Energy" in the energy generation category.
What makes the Swift novel is that it's specifically designed to reduce the noise and potentially building-damaging vibrations that come from older small wind turbine designs.
The patented key to their big idea was the diffuser (the circle around the rotor) which prevents air being thrown at high speed off the ends of the blades. This is the source of the ethereal din and inefficiency common to all previous wind turbines.Also, at high speed, the sculpted rim acts like the inlet of a jet engine, speeding the flow of air through the rotor plane, boosting its overall efficiency and allowing it to generate up to 1.5kW of electricity at one time (around 4500kWh annually). Meanwhile, the twin fins at the back hold the turbine into the wind like a weather vane.
The product information sheet (PDF) goes so far as to call it "silent" -- and comments from test users seem to back up that claim. The price -- £1500, or about $2900 -- is recovered in about five years of use, at the typical rate of around £300 worth of generation per year, assuming the 4,500 kWh production level.
For a typical home, this is enough to offset a good portion of electricity use. But the real win is when a micro-turbine is combined with building-integrated solar and high-efficiency consumption: relatively inexpensive additions to a home could turn it into a net producer of power. Best of all, these can be retrofits to existing buildings. Combine these with a gas-optional hybrid -- recharged for free overnight by home renewable power -- and you might even have the makings of the sustainable single-family home.
