30-11-2012, 01:31 PM
A Project Report on Design and Analysis of Vertical Axis Wind Turbine
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ABSTRACT
INDIA shines. This is possible only if it is self-reliant in the field of technology. Technological development can be achieved by solving energy crisis. For this alternate sources of energy are explored. Wind energy is one of the alternate non-conventional energy sources.
Wind turbines play a major role in harnessing wind energy. The main component of wind turbine, which helps in harnessing wind energy, is its blade. The flow of wind on the turbine blade causes it to rotate; the rotation of turbine blades causes the rotation of the rotor shaft. This shaft is connected to a generator, which in turn generates Electrical Power. The wind turbine blade is an integration of different airfoils along the blade axis.
The merging of rapidly rising costs, decreasing of supply and demand, and growing concern of global climate change is inciting efforts to find viable energy alternatives. Some of the proposed alternatives such as large scale use of bio-fuels may not be achievable or sustainable. Other exotic possibilities such as geothermal energy may be viable but are local and limited. Solar cell technology is still miniscule, expensive and inefficient. It therefore seems that the World is stuck with oil, coal, natural gas, and wind.
An Introduction to Wind Energy
Ever since the rapid spread of industrial Development, the world has witnessed a need for Gasoline and other petroleum products that can never be saturated. We are now in a global crisis regarding fuel consumption, the need for the rapid development of renewable energy systems is of prime importance especially in industrially developing countries such as India.
One of the expeditious and profitable solutions to this worldwide situation is Wind Power.
Wind, an energy resource
All renewable energy sources (except tidal and geothermal power) and even the energy in fossil fuels, ultimately come from the sun. The sun radiates 1014 kWh of energy to the earth per hour. About 1-2% of the energy coming from the sun is converted into wind energy. Wind is caused by differences in pressure. When a difference in pressure exists, the air is accelerated from higher to lower pressure. On a rotating planet, the air will be deflected by the Coriolis effect, except exactly on the equator. Globally, the two major driving factors of large-scale winds (the atmospheric circulation) are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces) and the rotation of the planet. The regions around equator, at 0° latitude, are heated more by the sun than the rest of the globe. These hot areas are indicated in the warm colours, red, orange and yellow in this infrared picture of sea surface temperatures.
Horizontal Axis Wind Turbine (HAWT)
Today the HAWT is the most cost-effective means of capturing wind energy. They are positioned on land or at sea in a proven windy area. Most horizontal axis turbines are built with two or three blades.
HAWTs have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. It most have a gearbox, which turns the low rotation of the blades into a quicker rotation that is more suitable to drive a generator, this can be seen in figure 2.
There are a number of sizes and power ratings of different HAWTs. The largest turbine that was created to generate electricity has blades that are the length of a High School football field. The wind turbine stands an amazing twenty floors high and the rotors are up to twenty-five feet in diameter. A wind turbine of this size is able to supply the electrical needs of a small business or home. A single small turbine can be used to generate electricity for a water pump, home or telecommunication devices. A small turbine is capable of producing fifty kilowatts of power.
The ideal braking of Wind
The more kinetic energy a wind turbine pulls out of the wind, the more the wind will be slowed down as it leaves the left side of the turbine in the picture. If all the energy from the wind would be extracted, the air would move away with the speed zero, i.e. the air could not leave the turbine. In that case no energy would be extracted at all, since all of the air would obviously also be prevented from entering the rotor of the turbine. In the other extreme case, the wind could pass though the tube above without being hindered at all. In this case it would not extracted any energy from the wind.
Therefore it can be assumed that there must be some way of braking the wind which is in between these two extremes and is more efficient in converting the energy in the wind to useful mechanical energy. It turns out that there is a surprisingly simple answer to this: An ideal wind turbine would slow down the wind by 2/3 of its original speed. To understand why, the fundamental physical law for the aerodynamics of wind turbines should be used: the Betz law.
Wind energy worldwide
Worldwide there are now many thousands of wind turbines operating, with a total nameplate capacity of 238,351 MW as of end 2011. World wind generation capacity more than quadrupled between 2000 and 2006, doubling about every three years. At the end of 2011, worldwide nameplate capacity of wind-powered generators was 238 gig watts (GW), growing by 41 GW over the preceding year. 2010 data from the World Wind Energy Association, an industry organization states that wind power now has the capacity to generate 430 TWh annually, which is about 2.5% of worldwide electricity usage. Between 2005 and 2010 the average annual growth in new installations was 27.6 percent. Wind power market penetration is expected to reach 3.35% by 2013 and 8 percent by 2018. The development of wind power in India began in the 1990s, and has significantly increased in the last few years. Although a relative newcomer to the wind industry compared with Denmark or the United States, India has the fifth largest installed wind power capacity in the world. In 2009-10 India's growth rate was highest among the other top four countries.