Wind energy is a logical choice for cheap, clean fuel. However, the devices cost money.

If you have ever visited the countryside, you would have seen ‘giant fans'. Tall towers topped by blades which rotate with the wind. The higher the wind speed, the faster these ‘fans' go round. It is hard to miss these enormous structures even from long distances. They generate a lot of noise and vibrations and a very few are also equipped with flashing lights to increase their visibility so birds don't fly into them.

These are windmills or wind turbines. They provide energy which is used in homes, farms and industries. Their numbers are gradually growing in India country as wind energy is a clean, non-polluting source of energy. Moreover, it is inexhaustible, since winds blow everyday and can never be used up!

Also, this energy is free––the fuel is provided free of cost by nature! Of course, the devices cost money. Like the sun's solar energy, it is naturally blowing winds that give us this energy. However, the sun's energy is generally available in a steady stream through the day but winds are not so steady. They are intermittent and their speeds vary at different times of the day. The energy produced by wind turbines depends on wind speed, location, air-temperature and the season. These devices have been in use since at least 200 BC.

Wind turbines and windmills are devices which convert kinetic energy from the wind into mechanical power and electricity. They are generally called windmills when they power machinery used for pumping water or grinding grains. They are termed wind turbines when they generate electricity.

Dr S. Gomathinayagam, Executive Director, Centre for Wind Energy Technology (CWET), Chennai, explains: “Air in motion is wind and it has a mass assicated with velocity and hence has kinetic energy. This is called Wind Energy which is proportional to square of velocity, and power is proportional to cube of velocity. We have more than 17,000 MW installed capacity which is close to 17,000 wind mills in eight states of India."

In India, wind energy policies are looked after by the Union Ministry for New and Renewable Energy. The states with highest wind-power concentration are Tamil Nadu, Maharashtra, Gujarat, Rajasthan, Karnataka, Madhya Pradesh and Andhra Pradesh according to the Global Wind Energy Council.

The smallest ones are windmills atop a home. You are likely to see a few of these in states like Goa, Maharasthtra, Kerala and West Bengal. Says Kochi-based K. S. Venkatachalam, who has one at home: “The equipment is expensive. But the fuel is free and clean!”

The big ones used in industries reach almost 400 feet into the sky! They have very high towers and extra-long blades to help them move well in conditions which may not be perfect. Their steel tower is anchored––which means firmly held in place––by a platform made of nearly thousand tonnes of concrete and steel rebar! In India, about 90-m tall towers use about 100-m diameter of the rotor (50-m long blades), CWET tells us.

However, before deciding to install these structures, you have to do some homework. You must check on the impact of turbines on (1) the community in that area––it should not hamper people's buildings or lifestyle in any way. So, crowded areas are out of question. Secondly, consider the impact on wildlife. Animals are easily scared by loud noises. Therefore, wind turbines are best installed, in remote rural areas.

There is no specific ideal condition. It is not that places with plenty of sea-breeze and land breeze will be perfect. “The appropriate consideration is the wind-speed distribution over the entire year,” reveals Dr Gomathinayagam.

Wind turbines have many advantages. They are fascinating to watch especially for children. You can understand how wind energy is making machines move by observing them. Very young kids find windmills very exciting as they look like enormous fans. Wind turbines provide clean, non-polluting, renewable energy. Dr Gomathinayagam adds: "It is abundantly available free fuel, not needing to be mined, stored, or transported (with or without fuel burning) and is completely renewable. But the disadvantage is that it is infirm or seasonal.