Advantages and Disadvantages of Horizontal Axis Wind Turbines (HAWT)

Darrieus Wind Turbine

• Shaping blades into a helix reduces torque ripple effect by spreading torque evenly over the revolution.

Revolving Wing Wind Turbine

• Uses 1 vertically standing, non-helical airfoil to generate 360-degree rotation around a vertical shaft.
• Revolves around a vertical shaft that runs through the center of the airfoil.

Advantages of VAWT

• Omni-directional, no need to track wind direction.
• No complex mechanism and motors required to yaw the rotor and pitch the blades.
• Gearbox replacement and maintenance are simpler and more efficient.
• Can use screw pile foundations, reducing road transport of concrete and environmental impact.
• Can be installed on HAWT wind farms below existing HAWTs, supplementing power output.
• Reduced noise compared to HAWTs.
• Reduced danger for birds.

Disadvantages of VAWT

• Power decreases to zero at high wind turbine velocity.
• Disc brakes can overheat, causing the turbine to catch fire.
• Dynamic stall of blades can occur due to varying angle of attack.
• Rotational speed is high, but inconsistent.

Advantages of HAWT

• Tall tower captures more wind with varying wind shear.
• High reliability.
• Blades can be bent using a gearbox to optimize wind attack angle.
• Rotor can be tilted by blades during storms.

Disadvantages of HAWT

• Only available in large sizes, challenging for distributed generation.
• Difficult to transport due to large size and weight.
• Requires a stronger structure to support heavy generator and gearbox.
• Installation and maintenance are difficult due to tall tower and heavy turbines.
• Noise from HAWT is high compared to other wind turbines.
• Heavy machinery is required for design and manufacturing.

Vertical-Axis Wind Turbine

• Main rotor shaft is set transverse to the wind, with components located at the base.
• Allows for easy service and repair due to generator and gearbox location.
• No need for wind-sensing and orientation mechanisms.
• Bernoulli's relation describes the aerodynamic lift generated by air pressure difference.

HAWT Requirements

• Installation site should not be too close to residents, but have sufficient power and transport infrastructure.
• Site should experience high wind speeds (often found in upland areas).
• Minimum wind speed of 12-14 km/h to start rotating and generating electricity.
• Strong winds (50-60 km/h) to generate at full capacity.
• Average commercial wind turbine requires approximately 1.5 acres of land for the turbine itself.
• Construction and installation require 25-40 acres of land.
• Turbine blade length is approximately 40 meters, and the tower length is approximately 80 meters.