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2010-10-31

Wind Turbines For Electricity

Wind Turbines For Electricity



Producing electricity by harnessing the power of the wind is one of the most efficient and fastest growing methods available today. Wind is free and available everywhere although it is most cost effective in areas where the wind is constant and the average speed is around 12 miles per hour or more. It is becoming competitive with gas and coal generated electricity and at prime sites even exceeds them. It really harnesses the power of the sun since that is what heats the planet and causes the wind. Temperature variations occur when some sun is blocked or reflected by clouds which make the earth under them become cooler than where the sun is striking the earth. This causes the warmer air to rise which then causes the cooler air to flow towards that area to replace the risen warm air. Similar air flow can be experienced near the shore lines of large bodies of water.
The land heats and cools faster than the water and this variation causes air flow back and forth along the shore line. Unbroken plains make good sites as do mountain passes where the flow tends to funnel through. This is important because as the wind speed doubles, the amount of energy available increases eightfold. Also, wind speeds increase as altitude increases so it is sometimes advantageous to position wind turbines at as high an altitude as possible.
Another advantage is that turbines require little maintenance. Since a lot of turbines can be positioned relatively close to each other in what is called a wind farm, you can get a lot of electricity with a minor amount of upkeep.
The fact that wind turbines can be placed just about anywhere there is wind means they can be distributed throughout the country. This means wind power can usually be generated locally. The other side of that coin is that as the national power grid improves, it almost doesn't even matter where they are located since the electricity can be transmitted just about anywhere.
Most turbines have the appearance of an airplane propeller and are constructed with a vane that keeps the blades that are attached to the rotor facing into the wind. This increases the efficiency. There are also turbines referred to as vertical axis wind turbines. These are different in that three or four blades are mounted on a rotating pole. Each blade is attached to the pole at the top and extends straight down but with a curve (or buckle) and then back in again to be attached near the base of the pole. Turbines of this type are able to capture the wind regardless of which direction it is blowing. The rotating pole is attached to a rotor that then generates the electricity.
Some turbines are built on towers that are 30 stories high and each blade may be 300 feet long. These are immense and require a very stable platform to keep from falling over in a high wind. Often times support wires are used for stabilization.
Wind energy has great promise but mostly in areas where the wind is a reliable source. Otherwise the downtime or reduced efficiency makes it less competitive than alternative methods such as solar, geothermal, etc.