The one thing people always want to know about micro wind turbines is just how small they are really. Wind power scientists say they must be as small as possible to bring down the cost and be practical but they must be large enough to catch enough wind and to generate enough electricity to be viable. Certainly technologists and businessmen involved in the development of small turbines would very much like them to be small enough to mount on the roof of the most modest shack, apartment or other third world dwelling.
Just to give some idea of scale, the towers of the very largest wind turbines used on wind farms and offshore are about 500 feet high and their generating capacity is in the 700-kW to 2.5-MW range. By contrast the tower of an average home or business turbine is currently in the order of 30 ft to 50 ft high with generating capacity in the order of 10 kW. Obviously such a tower is still too large to be roof-mounted for domestic or small office wind power generation, but anything smaller than that which can be roof-mounted can be classed as micro wind turbines.
Although the utilization of wind power by individual households and businesses the world over is where the future potential of wind generated electricity lie, the sight of a small windmill mounted on a roof is still a rarity. The factors which are prohibiting their widespread use can be summarized as technological development and affordability.
On the technological side of micro wind turbines, the trick is to make roof units cheap and long-lasting enough to make them attractive to consumers and for them to be constructed so that they can scoop sufficient wind to produce a viable amount of electricity. On the technical side they need to be able to make the most of the available wind. The challenge arises from the fact that roof mounted units are relatively near the ground where there is less wind.
At the moment there cannot be said to be a huge micro wind turbines industry
But there are wind power inventors, businessmen and technologists who are trying to come up with the optimum product. They are using cheaper materials and finding different ways of reaping the wind. For instance, a Hong Kong company has replaced the tower and rotor design with a string of 25cm wheels that spin to generate power. Some micro turbines are capable of working in wind speeds of only 2m/second. They have low impact on the environment in terms of noise and aesthetics. But still the cost of these roof mounted units is preventing widespread use. Example: a 0.6kW domestic roof-mounted unit that costs around $6000, generates about 1315 kW (about a tenth the amount use annually by the average US household, and will take 23.3 years to recoup its cost.
At this stage of developments there is a lot of excitement and talk when it comes to the potential of the domestic roof-mounted micro wind turbine but until the installed costs start to approach the target prices at which they will be available to even the poorest people, the micro turbines potential will go unrealized. However research in commercial companies and at universities and technical institutions is ongoing. Very soon the sight of micro wind turbines could be commonplace. More info