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Wind Power.

Extracts from this document...


Wind Power

The wind turbine, also called a windmill, is a means of harnessing the

kinetic energy of the wind and converting it into electrical energy. This

is accomplished by turning blades called aerofoils, which drive a shaft,

which drive a motor (turbine) and ar e connected to a generator. "It is

estimated that the total power capacity of winds surrounding the earth is

1 x 1011 Gigawatts" (Cheremisinoff 6). The total energy of the winds

fluctuates from year to year. Windmill expert Richard Hills said that the

wind really is a fickle source of power, with wind speeds to low or

inconsistent for the windmill to be of practical use. However, that

hasn't stopped windmill engineers from trying. Today, there are many

kinds of windmills, some of which serve differen t functions. They are a

complex alternative energy source.

What to consider when building a windmill In choosing where to build a

windmill, there are many important factors to consider. First is the

location: 1) Available wind energy is usually higher near the seacoast or

coasts of very large lakes and offshore islands. 2) Available wind energy

is gene rally high in the central plains region of the U.S. because of the

wide expanses of level (low surface roughness) terrain. 3) Available wind

energy is generally low throughout the Southeastern U.S. except for

certain hills in the Appalachian and Blue Rid ge Mountains, the North

Carolina coast, and the Southern tip of Florida. This is because of the

influence of the "Bermuda high" pressure system, which is a factor

especially during the summer. Also important to consider is the wind

where you are going to build: 1) the mean wind speed (calculated my

cubing the averages and taking the mean of the cubes) and its seasonal

variations. 2) The probability distribution of wind speed and of extreme

wi nds. The mean wind speed must be high enough, and the distribution must

...read more.


point of the lowest blade, H1 is the height of the highest point, and H2

is the height of the lowest point. n is the index location of the site, a

va lue that measures the roughness of the terrain.

The structures, aerofoils (see also vector diagrams, attached)

The support of the windmill is generally made out of steel. The

windshaft is the shaft which carries the windwheel or aerofoils. It is

turned as the aerofoils turn. It is made of steel or wood.

Aerofoils are the blades on a windmill. They can be made out of

any material. They were first made of wood or wood composites. Steel was

used after that. Aluminum is used in the Darrieus windmills because it is

much stronger. Unfortunately, Aluminum fatigues quicker. Some windmills

use fiberglass blades. New materials such as strong alloys are being used

in today's windmills experimentally. It is important that the blades have

a large lift force and a small drag force. The lift force is the force

needed to bend the flow of the (fluid) air. It is the force perpendicular

to the stream of the air. The drag force is the force parallel to the

stream. The aerofoil must be able to develop a lift force at least 50

times greater than the drag. Torque acts on the aerofoil with a vector

from the center of rotation away. Other forces that act on the blades of

windmills are wind shears, wind gusts, which push on the aerofoils,

gravity, a pull towards the earth, and shifts in the direction of the

wind. Shifts in the direction of the wind are often accounted for by

having a

small blade, called a tailvane, on the backside of a windmill. The wind

blows on a flat side of the tail, which is oriented differently from the

aerofoils. Then, the aerofoils can be rotated to face into the wind. If

...read more.


a r ubber tire on the spinning shaft of the motor and adjusted it so that

this rubber tire would be rotated by the spinning black box upon which the

blades spun. Next, I attached two large wires to the motor. I then made

a circuit. This circuit was a littl e difficult to make. It had a place

for the wires from the motor, ran through resistors and a variable

resistor, and then an Ammeter and then the place where I was to plug in

the light. In parallel was a place for a battery and/or a voltmeter.

After a few minor adjustments, I was ready to test my product. At first,

when the circuit was completed, the current flow was very low. There were

a number of adjustments I had to make in order to make the windmill work

better. First, I moved the fan that was blowing air on the blades,

farther away. I added a seco nd fan and adjusted the angle of these two

so that they were blowing at the center of the windmill. I turned the

windmill around so that it faced away from the fans. I loosened the

screws that held the blades on. I inserted a piece of cardboard 1/3" th

ick into this space. This was to adjust the pitch angle of the blades so

that they would "cut through" the air better. The adjustments I made were

excellent. They worked. When I connected everything, I began to notice

an immediate change in the Ammete r. I was seeing as much as 20 milliamps

and 6.1Volts. Before, there were 5 milliamps and 3.5 Volts. I began to

experiment more with the angles of the fans, distances, and stuff like

that. For my light source, I used a green light. It had an internal

resistance of 450 ohms. This bulb was 1/2 W. It lit up easily and was

bright. The Future

The Future will likely bring bigger and better things for the wind

turbine. Many new wind turbine models are being built. The wind turbine

holds much promise for energy production in the years to come.

...read more.

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