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Posted by Energetic
Turbines should be mounted on a suitable tower to raise them above any nearby obstacles. A good rule of thumb is that turbines should be at least 30 feet (9 m) higher than anything within 500 feet (152 m). In general, an effort should be made to make sure that a small wind turbine is as far away as possible from large upwind obstacles. Measurements made in a boundary layer wind tunnel have indicated that significant detrimental effects associated with nearby obstacles can extend up to 80 times the obstacle's height downwind. However, this is an extreme case. Another approach to siting a small turbine is to use a shelter model to predict how nearby obstacles will affect local wind conditions. Models of this type are general and can be applied to any site. They are often developed based on actual wind measurements, and can estimate flow properties such as mean wind speed and turbulence levels at a potential turbine location, taking into account the size, shape, and distance to any nearby obstacles.
A small wind turbine can be installed on a roof. Installation issues then include the strength of the roof, vibration, and the turbulence caused by the roof ledge. Small-scale rooftop turbines suffer from turbulence and rarely generate significant amounts of power, especially in towns and cities.
Smaller scale turbines for residential scale use are available, they are usually approximately 7 to 25 feet (2.1–7.6 m) in diameter and produce electricity at a rate of 300 to 10,000 watts at their tested wind speed. Some units have been designed to be very lightweight in their construction, e.g. 16 kilograms (35 lb), allowing sensitivity to minor wind movements and a rapid response to wind gusts typically found in urban settings and easy mounting much like a television antenna. It is claimed, and a few are certified, as being inaudible even a few feet (about a metre) under the turbine.
The majority of small wind turbines are traditional horizontal axis wind turbines, but Vertical axis wind turbines are a growing type of wind turbine in the small-wind market. These turbines, by being able to take wind from multiple dimensions, are more applicable for use at low heights, on rooftops, and in generally urbanized areas. Their ability to function well at low heights is particularly important when considering the cost of a high tower necessary for traditional turbines. All big companies in this industry, such as WePower, Urban Green Energy, Mariah Power, and Helix Wind, have reported sharply increasing sales over the previous years.
Dynamic braking regulates the speed by dumping excess energy, so that the turbine continues to produce electricity even in high winds. The dynamic braking resistor may be installed inside the building to provide heat (during high winds when more heat is lost by the building, while more heat is also produced by the braking resistor). The location makes low voltage (around 12 volt) distribution practical.