The climate of the coastal areas of Sindh is predominated by monsoon winds most of the time during the year. The word monsoon is derived from an Arabic word meaning 'season'.
The intense cooling which occurs in Siberia during winter has the effect of producing high pressure in Mongolia, in winter, causing winds to blow from the North East.
These winds travel over the huge land mass of Asia before arriving in the coastal areas of Sindh.
They enter as a gentle breeze with an average speed of seventeen kilometres per hour during the months of December, January and February.
During March, these winds start weakening and finally are dominated by the local weather.
These north-easterly winds, occasionally, exceed the speed of seventeen kilometres per hour during winter gales.
Because of the extreme heat experienced on South Asia's land mass during the summer season, an intense low pressure develops in this region.
The south easterly trade winds from the South Indian Ocean, to fill the gap, start blowing towards this region.
When these winds pass the equator, the Coriolis forces these winds to bend to their right side at a 90 degrees angle.
They start to blow from the South West direction. Before arriving on the coasts of south Asia, these winds have acquired sufficient energy after travelling for more than a thousand miles on the smooth surface of the Indian ocean.
They blow violently at a speed of more than thirty kilometres per hour during the months of June, July, August.
During the second week of September they start slowing down, diminishing and are finally taken over by the finally taken over by the local weather.
There is therefore abundant wind energy available at our coasts and it can be utilised for power generation and other purposes.
A windmill can be defined as a machine that can convert kinetic form of energy into other useful forms of energy such as electrical energy etc.
Wind energy is derived from the force of the wind moving oblique blades or sails, radiating from a shaft.
The turning shaft is connected to machinery that carries out work such as milling grain, pumping water, or generating electricity.
When the shaft of the wind mill is connected to a load, such as a pump, this is typically called a windmill. And when it is used to generate electricity, it is known as a wind turbine generator.
The ancient origin of wind-driven mills is as early as the 7th century AD. The earliest European windmills started in the 12th century. They rapidly spread throughout Europe.
These early wooden structures, called post mills, were rotated by hand around a central post to bring its sails into the wind.
The tower type mill was developed in France during the 14th century. Besides milling grain and irrigating farmland, windmills, developed from the 15th century to the 19th century, were adapted to a variety of tasks, including the pumping of seawater from land below sea level, sawing wood, making paper, pressing oil from seeds, and grinding different materials.
A major improvement on the windmill was the fantail, a mechanism invented in 1745 that automatically rotated the sails into the wind.
During 1772, the spring sail was developed. This type of sail consisted of wooden shutters, the openings of which could be controlled either manually or automatically to maintain a constant sail speed in winds of varying speeds.
Other improvements included air brakes to stop the sails from rotating and the use of propeller like airfoils in place of sails, which increases the usefulness of the mills in light winds. By the 19th century the Dutch had built more than 8000 windmills.
Windmills were widely employed for pumping water during the settlement of westerners in the United States of America.
The use of wind turbines for generating electricity was pioneered in Denmark during the 1890s.
Small wind turbine generators supplied electricity to many rural communities in the United States until the 1930s, when power lines were extended across the nation.
Large wind turbines were built during this time. The largest turbine was the Smith-Putnam generator, installed in 1941 at Grandpa's Knob near Rutland.
Modern wind turbines are propelled by one of two effects: drag, by which the wind pushes the blades; and lift, by which the blades are moved in the same way as an airplane's wing rises on an air current.
Turbines operated by lift turn more rapidly and are inherently more efficient. Wind turbines can be classified as horizontal-axis machines, with their main shafts parallel to the ground, or vertical-axis machines, with shafts perpendicular to the ground.
Horizontal-axis turbines used to generate electricity have one to three blades in number.
Those used for pumping may have many more. The most common vertical-axis machines, named after their designers, are the Savonius, used primarily for pumping, and the Darrieus, a higher-speed machine resembling an eggbeater.
Water pumper is a high-torque, low-speed windmill. Water pumpers are used, mainly, to draw water from underground.
These machines use a rotor, usually from 2 to 5 m (from 6 to 16 ft) in diameter, with a number of oblique blades radiating from a horizontal shaft.
The rotor is mounted on a tower, high enough to catch the wind. A large, rudder-like vane directs the wheel into the wind.
The wheel turns gears that operate a piston pump. When wind velocities become excessive, safety devices automatically turn the rotor out of the wind to prevent damage to the mechanism.
Wind turbine generators consist of a variety of components. The rotor converts the power of the wind to the rotating power of the shaft; a gearbox increases speed; and a generator converts the shaft power into electrical power (Electric Motors and Generators).
In some horizontal-axis machines, the pitch of the blades can be adjusted to regulate the speed during normal operation and, also, to shut down the machine when wind speeds are excessive.
Others use stall, an aerodynamic phenomenon that naturally limits the power at high wind speeds.
The modern machines start operating at, as low as, wind speeds of about 10 km/h. They achieve their rated power at about 40 to 48 km/h and shut down in wind speeds of about 100 km/h (about 60 mph).
The best sites for turbine generators have an annual average wind speed of at least 20 km/h.
Scientists have estimated that as much as 10 percent of the world's electricity could be provided by wind generators by the middle of the 21st century.
The most successful wind turbine generators for large-scale power generation have been of medium size (from 50 to 100 ft in diameter, with power ratings of 100 to 400 kw).
These are sometimes installed in groups, and are known as wind farms. The world's largest wind farms are in California where wind turbines can generate power up to about 1120 mw. A typical nuclear plant has a rating of a out 1100 mw.
The cost to produce wind power in such applications is competitive with that of many other forms of power generation.
Denmark now obtains more than 2 percent of all its electricity from wind turbines.
Wind turbines are also being used to increase the power supply to communities on islands or in other remote locations.
Wind energy, which contributes negligible pollution and very few greenhouse gases to the environment, is a valuable alternative to non-renewable fuel, such as oil.
In the United States, the cost of energy from larger electrical output wind turbines used in utility-interconnected or wind farm applications dropped from more than $1.00 per kilowatt-hour (kWh) in 1978 to under $0.05 perk kWh in 1998.
It further came down to $0.025 per kWh when new large wind plants came on line in 2001 and 2002.
The hardware costs of these wind turbines has further dropped in the past five years, under pricing the capital costs of almost every other type of power plant.
It's difficult to accurately compare the costs of wind plants and fossil fuel plants because the cost factors are so different.
Low installed-cost-per-kilowatt figures for wind turbines are somewhat misleading because of the low capacity factor of wind turbines relative to coal and other fossil-fuelled power plants.
(Note: "capacity factor" is simply the ratio of actual energy produced by a power plant to the energy that would be produced if it operated at rated capacity for an entire year).
Capacity factors of successful wind farm operations range from 0.20 to 0.35. These can be compared with factors of more than 0.50 for fossil-fuel power plants and over 0.60 for some of the new gas turbines.
Because of the predominant winds from south west and from the north east during the monsoon, the coastal belt of Pakistan is ideal for power generation by wind mills.
The ideal site for a wind mills farm must be on, or near, the coast, at an elevation of approximately 6 to 10 meters.
For a pilot project, instead of the old version of windmills of lesser power generating capacity (these windmills are going to be obsolete), a system of approximately 250 kw generating capacity wind mills may be installed.
The total number of windmills in a farm are subject to the availability of funds. A new windmill of 250 kw capacity costs approximately $75000 and a second hand windmill generator of such capacity costs approximately $50,000.
Another $20,000 are required for transport, logistics and for erecting it. For a farm of ten windmills, five acres of land, with an infrastructure, and twelve personnel for operating and maintenance in eight hourly shifts, are required.
For a pilot project of a medium sized windmill farm we need to import this technology into our country.
During the next couple of years sufficient people must be trained. Our government should consider a mega project for utilising wind energy to generate electric power in our coastal areas.
Most of our coastal area is of a rocky or hilly nature. In this area, numerous medium to large sized, uninhibited barren valleys exist, very close to the sea. One of these valleys may be selected for such a project, to generate electric power by wind energy.
The mouth of the valley, close to the sea, may be closed by building a dam to create a water reservoir for a steady waterfall, at a rate of approximately fifteen thousand cubic meter per hour.
Once this dam is constructed, if there is no drought, it would fill with rain water within a year but, to maintain a sufficient water level in the dam to run power turbines throughout the year, wind turbines erected on the coast could pump sea water into the dam.
Moreover, this brackish (mixed salt water) would provide the ideal source of sea food. A dam of such a size, filled with brackish water (mixture of rain and sea water), is ideal for good quality sea food.
It can provide approximately five hundred tonnes of shrimp and red snapper fish annually.
As the underground water in the coastal areas is salty, there would be no ecological threat or danger of soil erosion.
There are numerous rainfall drains in this area and the outgoing water, from the power turbines, would flow into these drains and fall into sea.
This project can be precisely described as follows;
-- Using wind energy to run wind turbines to pump Arabian Sea water to a dam (reservoir).
-- Using water energy to run hydro turbines to generate electricity.
ADVANTAGES:
-- Power generation by wind energy is environment friendly. There is no emission of water gases in the air and there is no solid or liquid waster discharged from the windmills.
-- The generation of hydro electricity from rivers has, world-wide, been badly affected by the meteorological phenomena of El-Nino and La-Nina during the last two decades.
-- Nuclear electricity is cheaper but leakage of nuclear material from reactors may cause severe environmental hazards. It could pose a threat to the life and health of all living organisations in the vicinity.
-- Emission of waste gases from thermal power plants consists of toxic and hazardous gases, which not only pollute the natural air but also cause global warming.
-- Whereas power generation from wind energy results in the negligible emission of gases into the atmosphere.
-- The argument, that it has a slightly higher cost, could easily be traded by the fact that it is environment-friendly, and is still in its developing stages. It is anticipated that its production costs would come down by approximately one-third during the next few years.
Hence, although the production cost of power generation by windmills is slightly expensive, yet, when compared to the severe adverse environmental effects of other power generation technologies, windmill technology remains "the best choice."
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