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Unformatted text preview: 3-1 Part II Wind Energy Systems Wind energy has recently become an economically viable (albeit site specific) alternative to conventional sources of energy. The harnessing of wind to meet the human energy needs, however, is a concept several thousand years old. It is believed that seven thousand years ago the ancient Egyptians used wind for their trading vessels. Vertical axis wind mills were used to grind grain in Persia as early as 200 B.C. In the 12th century A.D., horizontal-axis wind mills were in use in Europe for meeting some mechanical energy needs. During the early stages of the industrial revolution many innovative designs of wind mills came out in Europe, especially in the Netherlands. During the 15th and 16th centuries, these wind mills were used to drain many of the major polders there. By 1892, electricity producing windmills, ranging in size from 5 to 25 kilowatts (kW), were developed in Denmark. Many such early wind turbine generators (WTG) played a significant role in providing electricity to the rural America up to the 1930's. In the 19th and early 20th centuries water pumping windmills were a part of the landscape in many parts of the United States. Since the 1930's many countries in Europe, and America have experimented with larger scale (100 + kW) wind turbine generators. The first large scale modern WTG was built in Vermont, USA in 1941. It had a diameter of 55 meter and produced 1250 kW of electricity at a wind speed of 13.5 meters/sec. After the second world war, through the 50's and 60's, many innovative wind turbine generators were designed and built in Europe.In the late 70's several multimegawatt WTG's were developed and installed under the sponsorship of the Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA) in the United States. New developments in the WTG design came to a standstill in the United States in the 80's, while design refinements continued in Europe. In the 90s and onwards, the R&D on multi-MW wind turbine generators picked up again in the US where large land-based WTGs are now a common sight. By the end of 2010 over 40,000 MW of wind turbine generators were installed in the United States. This part of the book deals with the use of wind energy for producing electricity, both in stand-alone and grid-connected modes. We shall study the wind turbine generator as a single unit, and as a part of a windfarm where hundreds of WTG's run in unison to supply electricity to the grid. There are four chapters that deal with wind energy in this part of the book. 3. Wind Resource 4. Power from the Wind 5. Wind Energy Conversion System 6. Large Scale Applications 3-2 Chapter three is devoted to the study of wind as a resource, its temporal and spatial variations, the source of wind data, and how to identify wind power sites. The next chapter deals with the computation of power available from the wind, variations in wind power, coefficient of performance and the capacity factor of a wind turbine generator. power, coefficient of performance and the capacity factor of a wind turbine generator....
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- Spring '12