Since the ancient times, people have harnessed the kinetic energy created by the flow of wind to generate heat, mechanical energy and electricity.
 Wind Energy in History
The earliest known windmills were in Iran (then Persia) where people constructed what looked like large paddle wheels that rotated with the wind to grind food grain. Similar designs of windmills became popular along the coast of the Mediterranean as well. Many years later, the Dutch improved this basic windmill to make it more efficient. They made its fins with sail cloth, which being light, caught even the slightest movement of wind. Holland is still famous for its picturesque windmills.
Later, American colonists used windmills extensively. They ground wheat and corn, pumped water, and sawed logs -- all with the aid of windmills. Rural areas far from power lines used windmills to generate electricity as late as the 1920s. But soon, power generated by fossil fuel combustion became so cheap and widespread that windmills were reduced to being merely picturesque additions to the American landscape.
This changed in the 1980s, when rising oil prices led to a renewed interest in wind energy. State subsidies and favourable policies caused wind energy to lift off in a big way in California. Other states followed suit, but still California generates twice as much energy from wind, than any other American state.
 How Wind Energy Machines work
Traditional windmills consist of blades that rotate when the wind blows. These are connected to a shaft, which can either power a pump or turn an electric generator. The amount of energy produced by a wind machine depends upon the wind speed and the size of the blades in the machine. In general, when the wind speed doubles, the power produced increases eight times. Larger blades capture more wind. As the diameter of the circle formed by the blades doubles, the power increases four times.
The actual process of converting the wind’s kinetic energy into more usable forms is as follows –
- The wind blows on the blades, making them rotate.
- The rotation of the blades turns a shaft inside the nacelle (the box at the top of the turbine).
- The shaft is connected to a gearbox which shifts gears to increase the rotation speed enough to crank up the generator.
- The generator, similar to ones found in conventional power stations, works on principles of electromagnetism, converting rotational energy into electrical energy.
- The electrical output enters a transformer, which adjusts the voltage to one that is suitable for the distribution system.
 Types of Wind Energy Machines
Wind machines are of two types, depending on whether the shaft is horizontal or vertical. Ones with horizontal shafts, which are very tall and wide to gather the maximum wind, are more popular. This shaft transmits power through a series of gears, which provide power to a water pump or electric generator. Their blades are like airplane propellers, and typically stand tall. In fact a horizontal axis wind turbine could even be as tall as a 20-storey building. The largest wind machine in the world has blades longer than a football field!
The vertical axis machines have up to four long curved blades on a vertical shaft. Their blades go from top to bottom and look like giant eggbeaters in shape. These are typically about 100 feet tall and 50 feet wide, and make up only a small percentage of wind machines presently in use.
The latest wind energy system, the Wind Amplified Rotor Platform (WARP) uses lesser land and is more efficient than the other wind machines in use today. Instead of blades, this system has what looks like a stack of wheel rims, each outfitted with a pair of small, high capacity turbines. Its manufacturers, Eneco plan to market WARP to power offshore oil platforms and wireless telecommunications systems. (for more on WARP, see )
 Basic Requirements for a Wind Farm
An area where a number of wind electric generators are installed is called a wind farm. Here is a list of considerations to keep in mind in order to develop a Wind Farm –
- Selecting the right location for a wind farm is very important. Look for open areas that are high above the ground, for as a rule, wind speed increases with altitude and over open land with no windbreaks. Good sites for wind plants are the tops of smooth, rounded hills, open plains or shorelines, and mountain gaps that produce wind funneling.
- There should be enough land available, for existing windmill technologies require a lot of space.
- Look out for a power grid nearby to explore the possibilities of connecting the wind energy output to it.
- If the Wind Machine is a small one, ensure it is close to the place where the power is to be consumes, to minimize transmission and distribution costs.
The biggest advantage of using wind as an energy source is that it is completely renewable, free and causes no harmful emissions. Also, global wind mapping has revealed that Wind Energy is only second to Solar Energy in its potential for addressing the world’s energy requirements.
It is also relatively cheap. Looking at leveled costs over twenty years, wind energy is the cheapest source of electricity. Unlike in conventional power projects, the cost per kilo watt hour reduces over a period of time as against rising cost for conventional power projects.
Wind energy projects require little or no investment in manpower.
In recognition of its immense potential, many players from the conventional fossil fuel and power sectors have entered the global wind energy market. Some of these include Shell, General Electric, ABB, Siemens, AES and Florida Power and Light.
Wind power, has long been considered to be as fickle as wind itself. Since the wind does not blow strongly enough to produce power all the time, energy from wind machines is considered "intermittent," that is, it comes and goes. Therefore, electricity from wind machines must have a back-up supply from another source. Further, this means that utility companies can use it for only part of their total energy needs.
Electricity produced by wind power often fluctuates in voltage and wattage, which makes it difficult to link it to a conventional utility grid.
Windmills and their blades are easily damaged by lightening and high winds. Their parts are difficult to replace and expensive to repair.
The rotating blades of Wind Energy Machines are often noisy and a nuisance for people living nearby. There have also been many cases of bird mortality because of the rotor blades of wind machines.
Many critics of the larger Wind Energy Machines feel that they have little aesthetic appeal and detract from the landscape’s natural beauty.
 New Applications
Smaller wind turbines are now being developed for generating electricity, heating, and pumping water in remote sites. Thanks to them, thousands of Mongolian nomads use modern micro turbines to boil water for tea. Central Americans use them to power refrigerators to store fish for delivery to nearby markets. Antarctic explorers use them to power their isolated base camps.
Recently, students at the Department of Industrial Design at Indian Institute of Technology, Delhi designed an even smaller wind turbine which can charge mobile phones. The pocket-size turbine generates three to four watts of electricity, enough to charge mobile phones, and costs merely Rs 200.
New research on Wind Energy machines by scientists at Stanford University has revealed ways in which wind farms can supply regular, not intermittent power. By running the power generated through powerful transformers to control voltage, and interconnecting wind farms with a transmission grid – wind energy can become as consistent a power source as coal power plants.
- World Wind Energy Association
- Connecting Wind Farms Can Make A More Reliable And Cheaper Power Source
- WIND: A GLOBAL POWER SOURCE
To view Global and local wind maps, go to http://www.windenergy.com/global_frame.htm and http://www.ocean.udel.edu/windpower/ResourceMap/index-world.html
For a comprehensive list of Wind Machine Suppliers, go to http://www.eco-web.com/index/category/7.6.html