Technology

HAWT or VAWT: Which Type of Windmill Has Better Performance?

Windmill

Our world is full of natural providers of energy – wind, water, coal, etc. And, there are several ways in which we obtain this energy from them; one such is windmills.   

What are windmills and how do they work?

Windmills are technological structures that convert wind power into rotational energy by means of vanes called sails or blades. The best places to install them are coastal areas, the top of rounded hills, open plains, or gaps in mountains.  

The rotational power of the wind gets converted into kinetic energy which is further used for various purposes like producing electricity, operating grind mills, etc.

Types of windmills:

In broader category, there are two types of wind mills:

1. Horizontal Axis Wind Turbine (HAWT)

This is the common style windmill which has blades that look like a propeller that spin on the horizontal axis.

2. Vertical Axis Wind Turbines (VAWT)

In this type of windmills, the blades are vertically placed on a vertical axis.

HAWT vs. VAWT
Source: www.energy.gov

Which type of windmill has better performance?

Often, people are confused as to which type of windmill has better performance? So, let’s explore the advantages and disadvantages of both categories:

1. Horizontal Axis Wind Turbine

Advantages:

  • The tallness of the tower allows access to stronger winds. In some wind shear areas, every ten meters up the wind, the speed increases by 20% and the power output by 34%.
  • The efficiency of horizontal axis wind turbines is high, as the movement of blades is perpendicular to the direction of the wind resulting in greater production of energy.

Disadvantages:

  • The placement of the rotor shaft and the electrical generator should be such that it must point towards the wind.
  • Large turbines need wind sensors to turn the blades in the direction of the wind.
  • To support the heavy blades, gearbox, and generator, the construction of a massive tower is required.
  • The cyclic twisting of the turbine can crack the blade roots, hub, and axle of the turbines.

2. Vertical Axis Wind Turbine

Advantages:

  • The wind turbine doesn’t need to be pointed into the wind because of the rotor shaft’s vertical arrangement which proves advantageous in places where the wind’s direction is highly variable or has turbulent winds.
  • With the vertical axis, the generator and other components can be placed near the ground, so, there’s no need of constructing high towers.
  • Easy installation and transportation.
  • Suitable for urban areas and areas with extreme weather conditions.
  • Lesser perilous for birds and other organisms, as the blades move comparatively slow.

Disadvantages:

  • It tends to create drag when rotating in the wind.
  • Since they are installed nearer to the base and the wind speed is slower at lower altitudes, they work at lower rotational power of the wind.
  • Airflow near objects can create turbulent winds leading to issues of vibration, noise, and bearing wear which tend to shorten its service life.
  • Efficiency is comparatively very low, as only one blade works at a time.
  • An initial push to start is needed via a small motor.
  • VAWTs may need guy wires to hold them up.

Advantages & Disadvantages: At a Glance

HWAT

VWAT

Advantages

Good-stability

Easy Maintenance & Low Noise.

Can start on its own.

Low contruction cost & Easy to transport.

High reliability & efficiency.

No need to adjuct according to wind direction.

High speed & high electricity generation.

Can operate at low wind speed.

Disadvantages

Difficult to install because of its complexity.

Low Efficiency.

High Noise level.

Very low starting torque & needs a motor to start.

Unidirectional & Dependent on direction of wind.

Lower wind speeds due to shorter heights.

Final Word

Now, after comparing the two, we can conclude that the Horizontal Axis Wind Turbines are best in terms of performance, as they generate maximum energy.  However, Vertical Axis Wind Turbines are more versatile and can adopt to varied conditions. Read the difference between the two in detail here.

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