Types of Wind Turbines
A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy.
Wind turbines can be separated into two basic types determined by which way the turbine spins. The size of wind turbines varies widely. The length of the blades helps determine the amount of electricity a wind turbine can generate. Small wind turbines used to power a single home or business may have a capacity of less than 100 kilowatts (100,000 watts).
We know that there is enough wind globally to satisfy much, or even most, of humanity’s energy requirements – if it could be harvested effectively and on a large enough scale. so that the largest turbines have capacities of five to eight million watts. Larger turbines are often grouped together to create wind power plants,that power provide to electricity grids.
There are Two types of wind turbines
Horizontal-axis wind turbines(HAWT)
A horizontal Axis Wind Turbine is the most common wind turbine design. Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and may be pointed into or out of the wind.
Most of the wind turbines currently in use are horizontal-axis turbines. Horizontal-axis turbines have blades like airplane propellers. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor.
The horizontal-axis turbines used on wind farms. HAWT blades have more than 100 feet long. Taller turbines with longer blades generate more electricity. Horizontal-axis turbines commonly have three blades.
- The tall tower base allows access to stronger wind in sites with wind shear. In some wind shear sites, every ten meters up the wind speed can increase by 20% and the power output by 34%.
- Variable blade pitch, which gives the turbine blades the optimum angle of attack. Allowing the angle of attack to be remotely adjusted gives greater control, so the turbine collects the maximum amount of wind energy for the time of day and season.
- High efficiency, since the blades always move perpendicularly to the wind, receiving power through the whole rotation. In contrast, all vertical axis wind turbines, and most proposed airborne wind turbine designs, involve various types of reciprocating actions, requiring airfoil surfaces to backtrack against the wind for part of the cycle. Backtracking against the wind leads to inherently lower efficiency.
- Massive tower construction is required to support the heavy blades, gearbox, and generator.
- Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators.
- HAWTs require an additional yaw control mechanism to turn the blades toward the wind.
- HAWTs generally require a braking or yawing device in high winds to stop the turbine from spinning and destroying or damaging itself.
- Their height makes them obtrusively visible across large areas, disrupting the appearance of the landscape and sometimes creating local opposition.
Vertical axis wind turbines (VAWT)
Vertical-axis wind turbines have blades that are attached to the top and the bottom of a vertical rotor. VAWTs is efficient as current horizontal axis systems, might be practical , simpler and significantly cheaper to build and maintain than horizontal axis wind turbines.
Although vertical axis wind turbines have existed for centuries, they are not as common as their horizontal counterparts. The main reason for this is that they do not take advantage of the higher wind speeds at higher elevations above the ground as well as horizontal axis turbines.
With a vertical axis, the generator and other primary components can be placed near the ground, so the tower does not need to support it, also makes maintenance easier. The main drawback of a VAWT generally create drag when rotating into the wind.
It is difficult to mount vertical-axis turbines on towers, meaning they are often installed nearer to the base on which they rest, such as the ground or a building rooftop. Some versions of the vertical-axis turbine are 100 feet tall and 50 feet wide. Very few vertical-axis wind turbines are in use today because they do not perform as well as horizontal-axis turbines.
- VAWTs have lower wind startup speeds than the typical the HAWTs.
- VAWTs may be built at locations where taller structures are prohibited.
- They can produce electricity in any wind direction.
- Low maintenance cost.
- They can be install in urban area.
- They are particularly suitable for areas with extreme weather conditions, like in the mountains where they can supply electricity to mountain huts.
- compared to HAWTs they are very less efficient with respect to them. This is because they have an additional drag when their blades rotates.
- Because of vibration bearing wear increase which result in the increase of maintenance cost.
- They create noise pollution.
- Low starting torque and may require energy to start turning.
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