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Wind Energy Harvesting 2.1 Introduction Wind is a renewable energy source used to generate electricity through wind turbines, which convert its kinetic energy into electrical power.VAWTs: Vertical axis, no yaw mechanism, less efficient."The best sites for wind turbines are areas with calm, steady winds, such as water surfaces or seas. Betz's law defines the maximum energy that can be extracted from the wind, and it depends on the difference in wind speed before and after passing through the turbine."The "cut-in" speed is the minimum wind speed required to start the turbine, while the "cut-out" speed is the speed at which the turbine stops to avoid damage. The curve also shows that the output power decreases when the wind speed exceeds 20 m/s. After the nominal speed (the speed for which the turbine is designed), the turbine's power remains constant to avoid damage. The "power coefficient" indicates the turbine's efficiency and is the ratio of the electrical output power to the total wind power.Although wind energy currently contributes only 1% globally, its growth is rapid, with countries like Denmark and Germany relying heavily on wind power.Later developments focused on improving turbines, creating wind farms, and establishing offshore sites to increase efficiency.A wind turbine consists of three main parts: the blades that capture wind energy, the rotor that connects the generator to the turbine, and the tower that supports other components.The turbine also includes a pitch system to maintain a constant speed, brakes to reduce speed, and a generator that converts mechanical energy into electricity.Roughness Classes: Terrain is classified from 0 (water surface) to 4 (dense cities or forests), impacting wind speed.It reaches its maximum value at the optimal wind speeds, where the turbine operates at high efficiency.Tower Height:

• Offshore towers are shorter than onshore ones, but taller towers are better for wind energy harvesting.Nacelle:
• Contains the gearbox, generator, and electronics to adjust the turbine based on wind speed and direction.Terrain Roughness: Affects wind speed and turbine efficiency, with rough terrain reducing performance.Wind Speed Reduction: Affected by terrain height and friction, calculable by specific formulas.Offshore turbines have a higher power coefficient than onshore turbines due to different optimal speeds.Yaw Mechanism:
• It aligns the turbine with the wind and monitors cable twisting.Winds are influenced by Earth's rotation and the Coriolis force, which causes winds to shift direction in each hemisphere.1.2.3.4.

Wind Energy Harvesting
2.1 Introduction
Wind is a renewable energy source used to generate electricity through wind turbines, which convert its kinetic energy into electrical power.

Wind speed is measured with a cup anemometer, and patterns are displayed on a Wind Rose map to identify directions and speeds.

Although wind energy currently contributes only 1% globally, its growth is rapid, with countries like Denmark and Germany relying heavily on wind power.
Winds are influenced by Earth's rotation and the Coriolis force, which causes winds to shift direction in each hemisphere.

Local factors like terrain affect wind speed and direction, so it’s important to study the area for optimal wind turbine placement.

Key factors for wind energy include air density, blade area, and wind speed. Energy increases with higher air density and wind speed, and larger blades capture more energy.
Wind speed is measured using a cup anemometer, which tracks revolutions per minute, and data is stored for long periods.

A Wind Rose shows wind speed and direction distribution. Winds from the north are typically stronger than those from the southwest.

Important data from the wind rose include wind frequency, average speed, and the mean cube of the wind speed.
History: Wind turbines have been used since ancient times for grinding grain. The first electric wind turbine was built in 1887 in Scotland.

In the 1970s and 1980s, interest in wind energy grew after the oil crisis, with the use of power electronics for wind power control.

Later developments focused on improving turbines, creating wind farms, and establishing offshore sites to increase efficiency.
Siting Wind Turbines: Best sites have high wind speed and low turbulence, indicated by wind roses.

Wind Power Classes: Wind is classified into 7 levels based on speed and power density.

Terrain Roughness: Affects wind speed and turbine efficiency, with rough terrain reducing performance.
Friction Coefficients: Vary by terrain, e.g., smooth ground (0.10) or large cities (0.40).

Wind Speed Reduction: Affected by terrain height and friction, calculable by specific formulas.

Roughness Classes: Terrain is classified from 0 (water surface) to 4 (dense cities or forests), impacting wind speed.
"The best sites for wind turbines are areas with calm, steady winds, such as water surfaces or seas.
Betz's law defines the maximum energy that can be extracted from the wind, and it depends on the difference in wind speed before and after passing through the turbine."
The maximum energy that can be extracted from the wind is 59.3% of the total available power. The wind speed ratio before and after the turbine should be 1/3 for optimal energy extraction. It is impossible to extract 100% of wind energy.
The power curve shows the output power of the turbine at different wind speeds. The "cut-in" speed is the minimum wind speed required to start the turbine, while the "cut-out" speed is the speed at which the turbine stops to avoid damage. The curve also shows that the output power decreases when the wind speed exceeds 20 m/s.
After the nominal speed (the speed for which the turbine is designed), the turbine's power remains constant to avoid damage. The "power coefficient" indicates the turbine's efficiency and is the ratio of the electrical output power to the total wind power. It reaches its maximum value at the optimal wind speeds, where the turbine operates at high efficiency.
The power coefficient (Cp) depends on the turbine design, especially the aerodynamic structure of the blades. It also depends on the tip speed ratio (λ) and the pitch angle between the blade and the rotor plane. Offshore turbines have a higher power coefficient than onshore turbines due to different optimal speeds.
A wind turbine consists of three main parts: the blades that capture wind energy, the rotor that connects the generator to the turbine, and the tower that supports other components. The turbine also includes a pitch system to maintain a constant speed, brakes to reduce speed, and a generator that converts mechanical energy into electricity.

1. 
   

   Tower Height:

   
   
   
   
   • Offshore towers are shorter than onshore ones, but taller towers are better for wind energy harvesting.
   
   
   
   


2. 
   

   Yaw Mechanism:

   
   
   
   
   • It aligns the turbine with the wind and monitors cable twisting.
   
   
   
   


3. 
   

   Nacelle:

   
   
   
   
   • Contains the gearbox, generator, and electronics to adjust the turbine based on wind speed and direction.
   
   
   
   


4. 
   

   Turbine:

   
   
   
   
   • Typically has 3 blades to convert wind energy into electricity.
     Energy Harvesting Systems:
     Wind Turbine Blade Design:
   
   
   
   

Two-blade turbines need higher wind speeds to start.
Blade radius increases captured energy.
Blades are lightweight and use lift and drag forces.
Wind Turbine Classification:

By Axis:
HAWTs: Horizontal axis, more common.
VAWTs: Vertical axis, no yaw mechanism, less efficient.
By Power Capacity:
Classified as small, medium, or large based on power capacity.