Working of a windmill

One of the few renewable energy sources found in nature is wind energy. Wind as a source of energy has been used by man since he used to sail boats. A windmill was invented as a machine which could convert the wind energy into rotational energy by use of vanes called blades or sails. Originally windmills were developed for the process of milling grain for food production. Since then, man has foundways to adapt a windmill for various industrial uses. A critical application was to pump water. Windmills are also commonly used for generating electricity and are known as wind turbines.

 History

The first working wind-wheel can be traced back to the in the 1st century AD. The Greek engineer Heron of Alexandria was believed to have used a wind-driven wheel to power a machine. Another early example dating back to the 4rth century in ancient Tibet and China is of a wind-driven wheel used as a prayer wheel. Certain historians also claim that the 17th century BC Emperor Hammurabi from Babylon also planned to use wind energy for his grand irrigation project.

 

Working

Windmills may either be the Horizontal Axis Turbines or the Vertical Axis Turbines, though these are rare. The Horizontal Axis Turbines are what we are familiar with, and have blades resembling an aeroplane propeller, and function in a similar manner.

When wind blows into the windmill, it gets slowed down by the blades of the windmill, and gets ‘caught’ or harnessed by them. The wind, as it blows over the blades creates a lift that turns the blades.

Electricity is produced inside the windmill. A drive shaft is connected to the rotating blades that runs down to a generator located within the base structure of the windmill. As the blades turn in the wind, the drive shaft simultaneously turns causing the generator to produce electricity. This electricity is then led through wires directly to where the electricity is needed and used.

Windmills may have different sizes, and generate electricity accordingly. They may also be used in groups where the need for electricity is large. Around 100 kilowatts of energy may be produced by smaller windmills that will be sufficient to power farms. Larger turbines may generate many megawatts of energy. The only factor is that wind needs be present for a windmill to be able to operate.

Parameters involved in a Windmill

• A windmill should be constructed near sources of wind energy which include seacoasts, coasts near large bodies of water or offshore islands
• Mean wind speed and its seasonal variations should be considered while constructing a windmill
• Strong drafts are harmful as they adversely affect the power output of windmills
• The wind should ideally blow in a same general direction since unexpected huge shifts in direction could be harmful
• The seasonal density of the air should be considered since high density will affect the windmill
• Dangerous conditions such as high humidity, sandstorms, and salt-spray are considered harmful for windmills
• Windmills benefit from channelled wind passing through mountains and sub-tropic trade winds

Overall efficiency of the windmill depends on the amount of electricity that can be produced over time on a cost basis. The factors that are important in determining the overall efficiency of a windmill one is its conversion ability and the ability to use low velocity winds.

Windmill technology is used most widely in Holland. The biggest wind energy producing country in the world is Germany followed by Spain. In the United States,, the biggest user of wind energy is California, which produces more than double energy compared to the other states of America.

The popularity of windmills arises from the fact that they produce energy without having any harmful consequences to the environment.