Types of wind turbines
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See also the Wind power category. for subtopics, how-tos, project pages, designs, organization pages and more. |
A wind turbine, wind energy harvester or wind energy conversion system is a machine that, powered by the energy of the wind, generates mechanical energy that is directly converted to electricity. The term wind energy harvester however can refer to both windmills, windpumps as well as wind turbines.
Several types of wind energy harvesters exist, each type being better in a specific situation (ie lower or higher altitudes, variable wind speeds, ...)
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[edit] VAWT wind energy harvesters
On lower altitudes above the soil, VAWT's (vertical axis wind turbines) are more efficient than HAWTs. Several types exist including Panemone, Savonius, Darrieus and Variable geometry HAWT's. Their efficiency can be read at following articles:
At AT CAD Team/AT wind turbine, there is also a link to very high efficiency Savonius wind turbines (design is still untested at present).
[edit] HAWT wind energy harvesters
On higher altitudes above the soil, HAWT's (horizontal axis wind turbines) are more efficient than VAWTs.
A basic HAWT wind harvester is composed of the following components [1]:
- tower
- bladed rotor
- mechanical-electricity generator (eg dynamo)
- transformer (and inverter; if needed)
A regular HAWT wind turbine comes with a tower at least 30 feet above obstructions. There are two basic types of towers useful for residential wind power systems (free standing and guyed). Free standing towers are self supporting and are usually heavier which means they take special equipment (cranes) to place them. Guyed towers are supported on a concrete base and anchored by wires for support. They typically are not as heavy and most manufacturer's produce tilt down models which may be easily raised and lowered for maintenance.
The kinetic (moving energy) from the winds is harnessed by a device known as the turbine. This turbine contains airfoils (blades) that capture the energy of the wind and use it to turn the shaft of an alternator (like you have on a car only bigger).
There are 2 basic kinds of blades (drag style and lifting style). We all have seen pictures of groundsailor windmills and these are a good example of the drag style of airfoil. Lifting style blades are twisted instead of flat and resemble the propellor of a small airplane.
A turbine is classified as to whether it is made to be installed with the rotor in a vertical or horizontal position and whether the wind strikes the blades or the tower first. A vertical turbine typically requires less land for it's installation and is a better option for the more urban areas on the planet. An upwind turbine is created for the wind to impact the airfoils before it does the tower.
These units normally have a tail on the turbine which is required to maintain the unit pointed into the wind. A downwind turbine doesn't need a tail as the wind acting on the blades tends to keep it oriented properly.
These turbine systems would be damaged if they were to be allowed to turn at excessive speeds. Therefore, units should have automatic over-speed governing systems. Some systems use electrical braking systems although some use mechanical type brakes.
The output electricity from the alternator is sent to a controller which conditions it for use in the home. The usage of residential wind power systems requires the home to either remain linked with the utility grid or store electricity in a battery for use when the wind doesn't blow sufficiently.
When the home is tied to the grid, the excess electricity that is created by the residential wind power system can be sold to the utility company to reduce and sometimes even eliminate your electric bill. During times with not enough wind, the home is supplied power from the utility company.
Photo: http://www.residentialwindturbines.org/wind-scheme-grid-tied.gif
[edit] High altitude wind energy harvesters
See AT CAD Team/AT wind turbine
[edit] External links
[edit] References
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