WIND TURBINES
For centuries, humans have harnessed the wind to power a variety of machines, from flour milling equipment to water pumps. With increasing concern for environmental issues, fluctuating oil and gas prices and improved technology, wind-driven electric generators, called wind turbines, are becoming common throughout the world. Most US installations are found in California, but utilities in many Midwestern and Eastern states are now building or operating wind turbines.
Cheaper to construct than conventional power plants, wind power has huge potential. By late 1999, the work capacity of wind-generated electricity was already 9,600 megawatts-enough to power 3.5 million typical suburban American homes! Some experts feel many states have sufficient wind resources to provide electrical power far above current usage levels; some feel it could someday provide electricity for the entire country.
While various designs exist, the horizontal axis style is increasingly common. These units consist of a large diameter rotor, a drive shaft connected to a gear box, and a generator. Except for the rotor, all of this equipment is housed in a streamlined nacelle. While it looks fragile, the entire unit weighs in at about 45,000 pounds in working order. The nacelle assembly rests on a 360 degree pivot, mounted at the top of a tall steel tower. This insures it is always exposed to the prevailing winds. Various support equipment cables and interconnections to the electrical distribution system are found at ground level.
Finding the proper site greatly enhances turbine performance, but there are many factors that impact the design. An evaluation of the available wind resources, measured in watts per square meter, indicates how much wind power is available (test towers). Wind speeds seldom remain steady and are affected by terrain, presence of large natural or man-made obstructions (trees or tall buildings for example) time of day and season. Speeds also vary at different heights above ground level. In general an average annual wind speed of 11mph (5 m/s) is required for a turbine to be effective, while speeds of 13mph (6 m/s) are needed for larger “wind farms”.
Since the turbine depends on wind speed for energy, its electrical output changes as the speed of the wind through the rotor increases or decreases. At moderate speeds, power output is greatly determined by the shape and geometry of the rotor blades. Each blade is airfoil shaped so air passes faster over the longer (upper) side, creating a lower air pressure area above the blade. This difference in pressure on the surface creates aerodynamic lift, the same force that causes airplanes to take off. But since the rotor is fixed to a hub, the lifting force causes rotation. At the same time, an opposite reaction creates drag force impeding the movement of the rotor. Designers must create a rotor blade with a high lift-to-drag ratio (adjustable along the blade’s length) so the generator always runs efficiently despite changes in wind speed. Rotor diameter, also called “sweep” or “capture,” is also critical for efficient operation. Designers must find the correct length to produce peak energy levels consistently from the wind at the site. The turbine is built to start producing electricity when the winds reach a certain level, known as the cut-in speed. To protect the turbine, a cut-out speed is also determined, which stops the rotor if wind speeds are too high. Many systems now incorporate adjustable pitch blades which improve performance, limit peak electrical output more efficiently and reduce the load on the drive train. The blades themselves are lightweight and are typically constructed of glass fiber reinforced epoxy. Since the blades rise above the tower and the turbine is often the tallest structure for miles, it makes an easy target for lightning. The rotors are equipped with receptors and conductors to discharge the bolt safely, along with lightning arrestors, deep earth grounding and shielding on the entire unit. Once in place, blades require minimal maintenance, with service lives of 20 years or more.
The support tower is also a critical part of the completed turbine. It must clear any ground obstacles and reach the desired elevation where efficient wind speeds are available. Built tough to support the weight of the unit above, they are made of tubular steel and assembled in sections. An internal safety ladder allows easy access to the nacelles in any kind of weather.
A microprocessor controls all of the turbine functions and interfaces with a remote panel, allowing for remote control, access and troubleshooting if problems arise.
Great improvements have been made in all areas of wind turbine design, including better gearboxes, drive trains and generators, that eliminate many earlier problems while increasing efficiency and lowering costs. These technological advances have also expanded the number of sits in the US where wind power can be put to work producing electricity. Modern wind turbines are extremely reliable and many systems often have an on-line availability of 99% and more.
Yes! Wind Power for Cohocton
For centuries, humans have harnessed the wind to power a variety of machines, from flour milling equipment to water pumps. With increasing concern for environmental issues, fluctuating oil and gas prices and improved technology, wind-driven electric generators, called wind turbines, are becoming common throughout the world. Most US installations are found in California, but utilities in many Midwestern and Eastern states are now building or operating wind turbines.
Cheaper to construct than conventional power plants, wind power has huge potential. By late 1999, the work capacity of wind-generated electricity was already 9,600 megawatts-enough to power 3.5 million typical suburban American homes! Some experts feel many states have sufficient wind resources to provide electrical power far above current usage levels; some feel it could someday provide electricity for the entire country.
While various designs exist, the horizontal axis style is increasingly common. These units consist of a large diameter rotor, a drive shaft connected to a gear box, and a generator. Except for the rotor, all of this equipment is housed in a streamlined nacelle. While it looks fragile, the entire unit weighs in at about 45,000 pounds in working order. The nacelle assembly rests on a 360 degree pivot, mounted at the top of a tall steel tower. This insures it is always exposed to the prevailing winds. Various support equipment cables and interconnections to the electrical distribution system are found at ground level.
Finding the proper site greatly enhances turbine performance, but there are many factors that impact the design. An evaluation of the available wind resources, measured in watts per square meter, indicates how much wind power is available (test towers). Wind speeds seldom remain steady and are affected by terrain, presence of large natural or man-made obstructions (trees or tall buildings for example) time of day and season. Speeds also vary at different heights above ground level. In general an average annual wind speed of 11mph (5 m/s) is required for a turbine to be effective, while speeds of 13mph (6 m/s) are needed for larger “wind farms”.
Since the turbine depends on wind speed for energy, its electrical output changes as the speed of the wind through the rotor increases or decreases. At moderate speeds, power output is greatly determined by the shape and geometry of the rotor blades. Each blade is airfoil shaped so air passes faster over the longer (upper) side, creating a lower air pressure area above the blade. This difference in pressure on the surface creates aerodynamic lift, the same force that causes airplanes to take off. But since the rotor is fixed to a hub, the lifting force causes rotation. At the same time, an opposite reaction creates drag force impeding the movement of the rotor. Designers must create a rotor blade with a high lift-to-drag ratio (adjustable along the blade’s length) so the generator always runs efficiently despite changes in wind speed. Rotor diameter, also called “sweep” or “capture,” is also critical for efficient operation. Designers must find the correct length to produce peak energy levels consistently from the wind at the site. The turbine is built to start producing electricity when the winds reach a certain level, known as the cut-in speed. To protect the turbine, a cut-out speed is also determined, which stops the rotor if wind speeds are too high. Many systems now incorporate adjustable pitch blades which improve performance, limit peak electrical output more efficiently and reduce the load on the drive train. The blades themselves are lightweight and are typically constructed of glass fiber reinforced epoxy. Since the blades rise above the tower and the turbine is often the tallest structure for miles, it makes an easy target for lightning. The rotors are equipped with receptors and conductors to discharge the bolt safely, along with lightning arrestors, deep earth grounding and shielding on the entire unit. Once in place, blades require minimal maintenance, with service lives of 20 years or more.
The support tower is also a critical part of the completed turbine. It must clear any ground obstacles and reach the desired elevation where efficient wind speeds are available. Built tough to support the weight of the unit above, they are made of tubular steel and assembled in sections. An internal safety ladder allows easy access to the nacelles in any kind of weather.
A microprocessor controls all of the turbine functions and interfaces with a remote panel, allowing for remote control, access and troubleshooting if problems arise.
Great improvements have been made in all areas of wind turbine design, including better gearboxes, drive trains and generators, that eliminate many earlier problems while increasing efficiency and lowering costs. These technological advances have also expanded the number of sits in the US where wind power can be put to work producing electricity. Modern wind turbines are extremely reliable and many systems often have an on-line availability of 99% and more.
Yes! Wind Power for Cohocton
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