20-12-2012, 06:54 PM
Wind Turbines
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A Journey into an Understanding of the Technology used to Harness the power of Wind
Your hosts: Sir James Kelley III and Dr. David N Rahni
Policy Perspective
On October 20th, 1956 Israeli forces swept into Egypt and overcame local opposition as they raced for the Suez Canal
British and French forces intervened as part of a “peace initiative” allowed the European powers to occupy and control the Suez Canal again.
The conflict cost over 1,000 Egyptians their lives
Denmark
In 2001, the Danish Wind industry produced 4.3 Terawatt Hours (TWh) of electricity
1 TWh (Terawatt Hour) = 1 trillion Watt Hours (1,000,000,000,000)
1 million barrels of oil produce can produce 73 Gigawatt Hours (GWh) of electricity
1 GHw = 1 billion Watt Hours (1,000,000,000)
Denmark used wind energy to create the equivalent of 59,000,000 barrels of oil in 2001
Introduction to Wind
Wind is caused by the energy radiated to the Earth by the Sun
Nuclear reactions take place inside the sun’s core, where the temperature is 1 x 107 K
This produces 4 x 1026 joules of electromagnetic radiation every second that is radiated into space
Some of it reaches the earth:
strikes the equator directly (giving it the most radiation)
diffuses along the Northern and Southern Hemisphere
the poles receive the lowest amount of radiation
Wind Turbines
“rotary engine in which the kinetic energy of a moving fluid is converted into mechanical energy by causing a bladed rotor to rotate”
opposite of a fan
turbine blades spin from the wind and make energy, instead of using energy to make wind
Wind rotates the turbine blades
spins a shaft connected to a generator
The spinning of the shaft in the generator makes electricity
Construction: Wind Sheer
Wind turbines, like windmills, are mounted on a tower to capture the most wind energy
wind speed varies by height
wind current 100m above the ground dropped in speed by 10% when its height declined to 50m
property is known as wind sheer
wind speed increases in speed with height,
due to friction at the Earth’s surface
The Hub heights of modern wind turbines, which produce 600 to 1,500 kW of electricity, are usually 40 to 80 meters above ground
Catching the Wind!
Turbines catch the wind's energy with their propeller-like blades
Usually, two or three blades are mounted on a shaft to form a rotor
The wind turbine blade acts an airplane wing
When the wind blows a pocket of low-pressure air forms on the downwind side of the blade
Air pressure = force exerted on an object by the weight of particles in air
measured in:
Inches of Mercury (“Hg),A
Amospheres (Atm)
Millibars (mb)
1013.25 mb = 29.92 “Hg = 1.0 atm.[2] At standard or normal atmospheric pressure, and at 15° C, air usually weighs about 1.225 kilograms per cubic meter
Limitations
limit to the amount of energy that can be harnessed by an individual wind turbine
The more kinetic energy that a wind turbine pulls out of the wind, the more the wind will be slowed down as it leaves
If a designer tried to extract all the energy from the wind
air would move away with the speed zero
air prevented from entering the rotor of the turbine
If the designer did the exact opposite and allowed the wind to pass through the wind turbine without being hindered at all, again,
energy will not be cultivated,
since the rotor blades would not be spun, the
shaft wouldn’t spin
kinetic energy would not be converted into electricity