Machines Theory

Understanding windmill energy

Learning how wind energy is converted to other forms of energy, you must be familiar with the term windmill. Wind energy is known as one the cleanest form of producing electricity. The windmill is a device for tapping the energy of wind by means of sails mounted on its rotating shaft. These sails are also called vanes or blades. Today you’ll get to know the definition, applications, components, diagram, types, and working of windmill energy. You’ll also get to know the advantages and disadvantages of windmills.

windmill energy

Read more: Understanding wind turbine


What is a windmill?

A windmill is a structure that converts wind power into rotational energy through its sails, use specifically for grain milling, pumping (windpumps), and power generation (wind turbines). Many other applications can be design to use wind energy. The windmill has its sails mounted at an angle or is given a slight twist so that the force of the wind against them is divided into the plane of the sails, and the imparts rotation. So,

A windmill can be defined as a machine that converts the kinetic energy of the wind into mechanical energy as all the blades of the windmill always rotate in a clockwise direction. wind power was first harnessed by sailors, who were able to know the lift and harness wind’s power through sails. This knowledge led to the development of the vertical axis sail-type windmill. It is used by the ancient Persians and Chinese for pumping water and grinding grain.

Read more: Types of wind turbine


Just as earlier stated, the applications of the windmill are used for milling grains, water pumping, and oil extraction from its seeds. The main purpose of windmills today is to convert wind energy into electrical energy and this electrical energy is further used to power end applications.

Components of windmill

The components of a windmill include blades, rotor, anemometer, and tower.

  • The blades are one of the essential components of the windmill, they control the functioning of rotor speed.
  • The rotor – it approximately took 20% of the device cost, including the blades that convert the wind energy to low-speed rotational energy.
  • Generator – it took about 34% of the wind turbine cost, including the electrical generator, control electronics, and most likely gearbox (e.g., planetary gearbox), adjustable-speed drive, or continuously variable transmission. These wind turbine components are responsible for converting the low-speed incoming rotation to high speed rotation suitable for generating electricity.
  • Surrounding structure – it is approximately 15% of the windmill cost, includes the tower and rotor yaw mechanism.
  • Anemometer – is used for measuring the wind speed.

Read more: Understanding Non-renewable energy resources

Diagram of a windmill:

diagram of windmill

Types of windmills

The various types of windmills are vertical axis windmills and horizontal axis windmills.

The panemone windmill is the first practical windmill using sails that rotates in a horizontal plane. A similar type of horizontal windmill with rectangular blades is used for irrigation. The horizontal-axis or vertical windmill is due to the plane of the movement of its sails. Below are the four types of horizontal axis windmill:

  • Post mill
  • Smock mill
  • Tower mill
  • Fan mill

Read more: Understanding renewable energy

Working principle

The working of windmills is less complex and can be easily understood. Conventionally, windmills are designed with three blades after various research of the best-suited amount of blade. The blades come in contact with the wind, which causes the blades to move along with the shaft. This is what produces the energy through the generator. This generator converts mechanical energy into electrical energy.

Watch the video below to learn more on the working of windmill:

Advantages and disadvantages of windmills


Below are the benefits of windmills in their various applications:

  • For horizontal axis windmills with a tall tower, the base gives access to the stronger wind in sites with wind shear.
  • High efficiency, because the blades move perpendicularly to the wind, receiving power through the whole rotation in HAWT.

Read more: Understanding energy sources

For vertical axis windmills

  • They produce electricity in any wind direction
  • Low production cost when compared to horizontal axis wind turbines.
  • A strong supporting tower is not required
  • Easy to transport from one place to another
  • Low maintenance cost.
  • Can be installed in urban areas.


Despite the good advantages of these types of windmills, some limitations still occur. Below are the disadvantages of windmills.

For horizontal axis windmills:

  • Massive tower construction is required.
  • Components like gearbox, rotor shaft, and brake assembly are being lifted into position.
  • Downwind variants suffer from fatigue and structural failure.

For vertical axis windmills:

  • Efficiency is very low compare to HAWT.
  • High vibration is experienced.
  • Noise pollution is created.
  • Due to vibration, bearing wear increases, resulting in high maintenance costs.
  • The initial push to start is required.

Read more: Forms of energy: kinetic and potential energy


Windmills are the purest and cleanest way of generating electrical power. it is a structure that converts wind power into rotational energy through its sails, use specifically for grain milling, pumping (windpumps), and power generation (wind turbines). That is all for this article, where the definition, applications, components, diagram, types, and working of a windmill. You also learned the advantages and disadvantages of windmills.

I hope you get a lot from the reading, if so, kindly share with other students. Thanks for reading, see you next time!

Write A Comment