Wind energy means the kinetic energy carried by the wind. It has been used as a source of energy on earth since long back. It is being used by humans for many mechanical works. Such as milling grains, water pumping, and power generation. The electric power is generated through the use of kinetic energy of wind to rotate the turbine similar to water-driven turbines.
Although technology is growing after 1980, it took a good position after 2000. It happens because the cost of manufacturing and installation of wind turbine unit was dropped to a reasonable value. And the efficiency to generate the electric power from kinetic energy of wind was increased to an optimum level. The wind speed is generally high at seashores. Therefore the installation of the wind-based turbines at these places is very demanding. About 196GW energy is being exploited until the end of 2010.
If we look back in history around 5000 B.C. the people were using the wind to sail the boat along the Nile river and after which around 200 B.C. Chinese were used to pump water using windmills and Persian were used to grind the grain. American were using windmills to grind wheat and corn. To pump water and to cut the wood at saw mills, through 20th century. Small wind plants suitable for farms and residences and larger utility scale wind farms that used to generate electricity were developed.
A 1.25Mw turbine that was established on Vermont Hilltop and known as Gradpa knob. Feb electric power to local area network, during Second World War( around 1940’s).
The oil storage of the 1970’s changedthe energy picture for the U.S. and world. This could find the path to use the kinetic energy of wind to generate electricity. From 1974 to 1980 U.S. government worked with industry to advance the technology and enable development of large commercial wind turbines. Which are developed under a program by National Aeronautics and Space Administration. The wind energy in U.S.slowed to late 1980’s because in the decrease in the price of oil. But it continued to grow in rest of Europe.
Wind energy resources
Earth surface on equator (or its neighborhoods) receives more solar radiation per unit area per year than the other places at different latitude on earth (visible to solar radiation). Also when latitude increases the surface of the earth become more oblique to solar radiations.
The solar radiation travels large distance to reach at the earth surface. So more energy of radiation gets attenuated as compared to at equator. That is why tropics are higher at the higher at higher temperature than regions with high latitude.
The heating of earth surface causes change in atmospheric pressure. Which causes the movement of air mas, reason to flow the wind.
Atmospheric pressure is measured in bar, it measured by Barometer. The S.I. unit of pressure is pascal (Pa) 1 Pascal = 1Nm2, and 1 bar= 100ka.
Another unit for measuring pressure is Psi. 1 Psi may be defined as 1 pound of force per square inch. It is primary pressure unit in United stare. 1 Psi = 6894.75729 Pascal.
When equator of earth is got heated because of solar radiations then low pressure region is created. Because the warm air is lighter and it rises above the equator. when this warm humid air reaches the troposphere, air in northern hemisphere moves toward northwards. Air in southern hemisphere air gets cool, when it reaches up to latitude of 30 degree. Because of accumulation air at this high pressure region is created (dry weather) at around these latitude world most deserts are found.
If any kind of air get reached at this latitude is bounces back to low pressure region. The wind blowing in this pattern is called trade winds. When these trade winds reach the equator. These causes circulatory motion like close loops these loops are called Hadley cells. If air further moves towards pole it forms Ferrel cell and polar cell.
After pole when it interact with the cold air it bounced back and moves toward 30 latitude. The wind motion of earth is also disturbed by phenomenon called Coriolis force. This cause the bending of wind/fluid in northern hemisphere to right and southern hemisphere to left.
Source of energy in wind
The energy in wind is in the form of its kinetic energy. Since Kinetic Energy = 1/2 mv2 , where m is mass of air in kg and v is velocity of wind in m/s. Mass (m) of air moving per second = (air density * area * lenght of cylindrical column M = pav
Kinetic energy = 0.5 pav3 Joule (J), Power= Kinetic energy of wind per second = 0.5pav3 watt.
Wind energy density (Pd)
It is the term used to express the wind power available per unit area swept by blades. Pd = Power/Area=0.5 Pav3 w/m2
Advantages of wind energy
- Wind turbine occupy less space than a limited sized power station.
- Wind mills occupies a few square meter for the base. So the land around the turbine can to be used for agriculture.
- With the development of advanced technologies. The efficiency of exploitation of wind energy is increased to considerable amount.
- Since the wind is available free of cost. Wind energy can be extracted as free source of energy.
- Wind turbine are a great resource to generate energy in remote areas, such as mountain communication and deserts. where the installation of wind turbine is easy.
- The Wind turbine can be developed in different sizes and capcity, in order to meet out the need of various population.
- Wind energy is environment friendly to surrounding. Since no fossil fuels (no liberation of green house gases) are brunt to generate electricity from wind energy.
- If wind energy developed in combination with solar energy then this energy source is great for developed. Developing countries to provide a steady, reliable supply of electricity.
Disadvantages of Wind Energy
- Wind turbine are generally less efficient than average coal/gas power station. Requiring multiple wind turbine to be built in order to make reasonable power.
- Wind power may be decreased with certain winds unreliability factors (viz. wind speed, duration).
- If the wind strength is too low to support a wind turbine or wind farm at any place. Then the solar power or geothermal power (whichever is possible) could be great alternatives.
- The noise pollution from commercial wind turbine is sometimes very high.
- Wind turbine construction can affect the surrounding wildlife badly during the build process.