Wind generators are an effective source of renewable power in many areas across the world. To make sure a small wind system is right for you, there are things to consider:
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Once you have determined you have the right conditions for a wind power system, you will need to consider the best place on your property. Proper siting is critical to the performance and longevity of your investment. It can make the difference between years of trouble free operation or continuous frustration.
This guide is a precursor to investing in a small residential scale wind power generator. Whether your reason for investing is because of your concern for the environment, helping reduce foreign fuel imports or pure economics, we at Energy Matters want to make sure you get the most from your wind generator. Before making any investment in small wind, be sure to review this guide carefully, ask lots of questions and once you feel confident, call Energy Matters!
"Do I have enough wind?" is often the first and most asked question. Generally, if you feel like you have a very windy site, you most likely have a good place for a wind power system. It is always a good idea to do your homework just to make sure. Wind resources can vary from placed to place. There are several places you can go to assist you.
The Bureau of Meteorology has recorded a series wind data for much of Australia that will give you a good idea what your wind resource is at your location.
Please note that winds decrease the closer they are to the ground.
You may also obtain wind data from your local weather station, university or even television station. Airport data is not recommended. Airports are generally located in lower wind areas (valleys) and their measurement techniques do not produce good data.
If wind maps or local data doesn't work, another method is looking around and observing of the deformation of vegetation and trees on and around your property. The Griggs-Puttnam Index was a scientific study that looked at how wind deformed vegetation to determine the wind resource at a particular site. Compare the drawing above with your own property to determine your wind resource.
Another strategy is conducting an actual wind resource assessment. This is by far the most accurate way of doing a site assessment but it is also the most expensive and time consuming if you hire someone else to perform the work. A more economical solution is the new Power Predictor; a tool that measures solar and wind energy at your site that you can install yourself.
Up until recently, the answer would have been no as the cost of an accurate data logging system was almost as much as a small wind power system. However, the new Power Predictor is a very economical solution for gaining an accurate measurement over a period of time.
Avoid hand-held anemometers as they only measure the reading at arm's length and certain times of the day. The do not give an accurate overall wind speed for your site at the height that you would install.
Once you have determined you have a good wind resource, you will want to site your wind generator in the most optimum place.
The ideal position for a wind power generator is a flat open space with good wind from at least one direction (known as the prevailing wind direction), a coastline, or a smooth hill top with an open area in the prevailing wind. The wind speeds up significantly near the top of the hill and the air flow should be reasonably smooth and free from excessive turbulence.
Excessive turbulence or "bad wind" causes fatigue damage and shortens a generator's working life. When siting, keep away from local obstructions such as large trees and houses, or use a taller tower to ensure that the generator is well above the obstructions. Wind speed also increases with height so it is best to have the generator as high as your zoning laws and investment payback will allow. It is recommended to site you generator at least 6 m (20 feet) above any surrounding obstacles such as trees or buildings in a 76 m (250 foot) radius (see general siting image above).
Wind resource is not the only consideration when siting. Components such as taller towers and running large amounts of wire more than 152 m (500 feet) from your site can add significant costs to your wind system. You will need to balance power achieved in the best wind site over the cost of installation to determine the best overall placement of your system.
3 typical siting Considerations
Coastal or Lakeside
Very strong prevailing winds typically blow from the ocean. If this is the case, it is very important to install your wind generator as close to the coastline as possible. Trees and taller structures can be down-wind from the wind generator.
Wind compresses as it blows over the top of a hill, increasing the wind speed. With proper placement, you may be able to use a shorter tower. We never recommend anything shorter than 10 m (33 feet). It is important to follow the general rule; that is the tower must be at least 6 m (20 feet) above any surrounding object.
Winds may be very turbulent running off a cliff causing wind shears. It is important to site the generator far enough from the cliff to avoid turbulent wind.
Because wind speeds increase with height, a residential wind generator is mounted on a tower. The tower also raises the generator above the air turbulence that can exist close to the ground because of obstructions such as hills, buildings, and trees.
Your wind resource will be cleaner and stronger the higher you go. The taller your tower, the better your power output. However, taller towers will increase the cost your installation and may not be allowed in some areas. While you should install your system in the tallest tower allowed, it is best to evaluate your overall energy and cost payback before investing in taller towers (see diagram at right, top).
Types of Towers
The two most common types of towers are guyed and monopole. Both are available in various designs. Some can be tilted-down for easy access while others require a crane for installation and service (see diagram below).
Guyed towers are less expensive than monopole towers. However, because the guy radius must be one-half to three-quarters of the tower height, guyed towers require enough space to accommodate them.
Monopole towers are more expensive but they offer the consumer an easy way to perform maintenance. Monopole towers can be lowered to the ground during hazardous weather such as hurricanes (see diagram on next page). Aluminium towers are prone to cracking and should be avoided.
A general rule of thumb is to install a small wind power generator on a tower with the bottom of the rotor blades at least 6 m (20 feet) above any obstacle that is within 76 m (250 feet) of the tower, 7.6 m (25 feet) to the hub.
Mounting small wind generators over 500 watts on rooftops is not recommended. Larger residential home wind generators vibrate and transmit noise to the structure on which they are mounted. This vibration can lead to noise and structural problems with the building. Mounting on the rooftop can also expose the generator to excessive turbulence that shortens its life.
Questions? Please contact our friendly team for more information.