Wind Turbines A Journey into an Understanding of the A Journey into an Understanding of the

Technology used to Harness the power of WindTechnology used to Harness the power of Wind

                                               

Policy Perspective On October 20On October 20thth, 1956 Israeli forces swept into , 1956 Israeli forces swept into

Egypt and overcame local opposition as they raced Egypt and overcame local opposition as they raced for the Suez Canalfor the Suez Canal

British and French forces intervened as part of a British and French forces intervened as part of a “peace initiative” allowed the European powers to “peace initiative” allowed the European powers to occupy and control the Suez Canal again.occupy and control the Suez Canal again.

The conflict cost over 1,000 Egyptians their livesThe conflict cost over 1,000 Egyptians their lives

Denmark In 2001, the Danish Wind industry produced 4.3 In 2001, the Danish Wind industry produced 4.3

Terawatt Hours (TWh) of electricityTerawatt Hours (TWh) of electricity 1 TWh (Terawatt Hour) = 1 trillion Watt Hours 1 TWh (Terawatt Hour) = 1 trillion Watt Hours

(1,000,000,000,000)(1,000,000,000,000) 1 million barrels of oil produce can produce 73 1 million barrels of oil produce can produce 73

Gigawatt Hours (GWh) of electricityGigawatt Hours (GWh) of electricity 1 GHw = 1 billion Watt Hours (1,000,000,000) 1 GHw = 1 billion Watt Hours (1,000,000,000) Denmark used wind energy to create the Denmark used wind energy to create the

equivalent of 59,000,000 barrels of oil in 2001 equivalent of 59,000,000 barrels of oil in 2001

Introduction to Wind

Wind is caused by the energy radiated to the Earth by Wind is caused by the energy radiated to the Earth by the Sunthe Sun

Nuclear reactions take place inside the sun’s core, Nuclear reactions take place inside the sun’s core, where the temperature is 1 x 10where the temperature is 1 x 107 7 KK

This produces 4 x 10This produces 4 x 102626 joules of electromagnetic joules of electromagnetic radiation every second that is radiated into spaceradiation every second that is radiated into space

Some of it reaches the earth:Some of it reaches the earth: strikes the equator directly (giving it the most radiation)strikes the equator directly (giving it the most radiation) diffuses along the Northern and Southern Hemispherediffuses along the Northern and Southern Hemisphere the poles receive the lowest amount of radiationthe poles receive the lowest amount of radiation

Creation of Seasons

Wind con’t The radiation from the sun heats the Earth's The radiation from the sun heats the Earth's

surfacesurface Heating process creates temperature differences Heating process creates temperature differences

between the: between the: Land,Water, AirLand,Water, Air

due to their different physical propertiesdue to their different physical properties• I.e. densityI.e. density• AAffects their respective abilities to absorb ffects their respective abilities to absorb

heatheat

Process of Wind Creation Wind “current of air (air Wind “current of air (air

moving from an A of high P to moving from an A of high P to an A of low Pan A of low P

hot air rises, it expands, hot air rises, it expands, becomes less dense, and is then becomes less dense, and is then replaced by denser, cooler airreplaced by denser, cooler air

Heated air rises from equatorHeated air rises from equator moves north and south in the moves north and south in the

upper levels of the atmosphereupper levels of the atmosphere circulates above cooler aircirculates above cooler air At roughly 30° latitude Coriolis At roughly 30° latitude Coriolis

Effect stops air. Effect stops air.

high pressure areahigh pressure area The Coriolis Effect “ the The Coriolis Effect “ the

tendency for any moving tendency for any moving body on or above the body on or above the earth's surface to drift earth's surface to drift sideways from its course sideways from its course because of the earth's because of the earth's rotationrotation

Northern Hemisphere Northern Hemisphere deflection rightdeflection right

Southern Hemisphere it is Southern Hemisphere it is to the leftto the left

Coriolis Effect: 3 Cell Effect

Harnessing the Wind

Wind Turbines ““rotary engine in which the kinetic energy of a rotary engine in which the kinetic energy of a

moving fluid is converted into mechanical energy by moving fluid is converted into mechanical energy by causing a bladed rotor to rotate”causing a bladed rotor to rotate”

opposite of a fanopposite of a fan turbine blades spin from the wind and make turbine blades spin from the wind and make

energy, instead of using energy to make windenergy, instead of using energy to make wind Wind rotates the turbine bladesWind rotates the turbine blades

spins a shaft connected to a generator spins a shaft connected to a generator The spinning of the shaft in the generator makes The spinning of the shaft in the generator makes

electricityelectricity

Construction: Wind Sheer Wind turbines, like windmills, are mounted on a tower Wind turbines, like windmills, are mounted on a tower

to capture the most wind energyto capture the most wind energy wind speed varies by heightwind speed varies by height wind current 100m above the ground dropped in speed wind current 100m above the ground dropped in speed

by 10% when its height declined to 50mby 10% when its height declined to 50m property is known as property is known as wind sheerwind sheer

wind speed increases in speed with height,wind speed increases in speed with height, due to friction at the Earth’s surfacedue to friction at the Earth’s surface

The Hub heights of modern wind turbines, which produce 600 to The Hub heights of modern wind turbines, which produce 600 to 1,500 kW of electricity, are usually 40 to 80 meters above ground1,500 kW of electricity, are usually 40 to 80 meters above ground

Internal Parts: The “Hub”

Turbines: Two Types

Horizontal Axis Wind TurbinesHorizontal Axis Wind Turbines Vertical Axis Wind TurbinesVertical Axis Wind Turbines

Two Types

Vertical Axis AdvantagesVertical Axis Advantages Can place generator on Can place generator on

ground ground You don’t need a yaw You don’t need a yaw

mechanism for wind anglemechanism for wind angle

DisadvantagesDisadvantages Lower wind speeds at Lower wind speeds at

ground level ground level Less efficiency Less efficiency Requires a “push” Requires a “push”

Horizontal axis AdvantagesHorizontal axis Advantages Higher wind speedsHigher wind speeds Great efficiencyGreat efficiency

DisadvantagesDisadvantages Angle of turbine is relevantAngle of turbine is relevant Difficult access to Difficult access to

generator for repairsgenerator for repairs

Energy: Kinetic to Electric Wind has kinetic energy: Energy of motionWind has kinetic energy: Energy of motion

KE = ½ M * UKE = ½ M * U22

The Mass (M) of Air per second is The Mass (M) of Air per second is volume (V) multiplied by its density (D)volume (V) multiplied by its density (D)

• M = VDM = VD• density of air = 1.2929 kilograms/mdensity of air = 1.2929 kilograms/m

The mass of air per second (M)The mass of air per second (M) traveling though a hoop is the area of the hoop (A)traveling though a hoop is the area of the hoop (A) multiplied by speed of the wind per second (u) multiplied by speed of the wind per second (u) multiplied the density of air (D)multiplied the density of air (D)

• M = AuDM = AuD area of the hoop (A) is radius (r) squaredarea of the hoop (A) is radius (r) squared

• A = A = ПП r r22

Catching the Wind! Turbines catch the wind's energy with their propeller-like bladesTurbines catch the wind's energy with their propeller-like blades Usually, two or three blades are mounted on a shaft to form a Usually, two or three blades are mounted on a shaft to form a

rotorrotor The wind turbine blade acts an airplane wingThe wind turbine blade acts an airplane wing When the wind blows a pocket of low-pressure air forms on the When the wind blows a pocket of low-pressure air forms on the

downwind side of the bladedownwind side of the blade Air pressure = force exerted on an object by the weight of Air pressure = force exerted on an object by the weight of

particles in airparticles in air measured in:measured in:

Inches of Mercury Inches of Mercury (“(“Hg),AHg),A Amospheres (Atm) Amospheres (Atm) Millibars (mb)Millibars (mb)

1013.25 mb = 29.92 1013.25 mb = 29.92 ““Hg = 1.0 atm.Hg = 1.0 atm.[2] At standard or normal At standard or normal atmospheric pressure, and at 15° C, air usually weighs about 1.225 atmospheric pressure, and at 15° C, air usually weighs about 1.225 kilograms per cubic meterkilograms per cubic meter [

Catching the Wind! Continued….

When air pressure is low in one locality, such as the downwind side When air pressure is low in one locality, such as the downwind side of a wind turbine blade, air from another area will rush in to equal of a wind turbine blade, air from another area will rush in to equal out the air pressureout the air pressure

The low-pressure air pocket created by the wind turbine blade then The low-pressure air pocket created by the wind turbine blade then pulls the blade toward it, causing the rotor to turnpulls the blade toward it, causing the rotor to turn

This process is referred to as lift.This process is referred to as lift. The force of the lift is actually The force of the lift is actually much stronger than the wind's force against the front side of the much stronger than the wind's force against the front side of the blade, which is called dragblade, which is called drag

The combination of lift and drag causes the rotor to spin like a The combination of lift and drag causes the rotor to spin like a propellerpropeller causes the spinning of the turbine’s shaft.causes the spinning of the turbine’s shaft. When shaft spins KE of movement is converted by generator into When shaft spins KE of movement is converted by generator into

usable electricity usable electricity

KE to Usable Energy

Bernoulli’s Principle Bernoulli’s PrincipleBernoulli’s Principle EnergyEnergyKineticKinetic + Energy + EnergyPressurePressure = Energy = EnergyPressurePressure + +

EnergyEnergy Kinetic Kinetic

Example: Example: If Energy KineticIf Energy Kinetic1 1 = (5), and Energy = (5), and Energy

PressurePressure11 = (11) = (11) and Energy Pressureand Energy Pressure22 drops to (1) drops to (1)

then Kinetic Energythen Kinetic Energy22 Increases to (15) Increases to (15)

Setup Types stand-alone stand-alone

not connected to a power gridnot connected to a power grid power created is directly channeled into powered power created is directly channeled into powered

sitesite utility power grid utility power grid

Stores energyStores energy connection must be available connection must be available

Combined w/ a photovoltaic (solar cell) systemCombined w/ a photovoltaic (solar cell) system has solar cells mounted on it. has solar cells mounted on it. Solar cells - thin wafers of silicon which, when Solar cells - thin wafers of silicon which, when

exposed to sunlight, produce…electric currentexposed to sunlight, produce…electric current

Efficiency large number of wind turbines are usually built large number of wind turbines are usually built

close together to form what is referred to as a wind close together to form what is referred to as a wind plantplant

The world’s largest wind plant located off the The world’s largest wind plant located off the coast of Oregon has 450 wind turbinescoast of Oregon has 450 wind turbines generates 300 MWh of energygenerates 300 MWh of energy meets the needs of 70,000 homesmeets the needs of 70,000 homes

This practice utilizes an area suited for wind This practice utilizes an area suited for wind energy by deploying multiple unitsenergy by deploying multiple units

Limitations limit to the amount of energy that can be harnessed by an individual limit to the amount of energy that can be harnessed by an individual

wind turbinewind turbine The more kinetic energy that a wind turbine pulls out of the wind, The more kinetic energy that a wind turbine pulls out of the wind,

the more the wind will be slowed down as it leavesthe more the wind will be slowed down as it leaves If a designer tried to extract all the energy from the windIf a designer tried to extract all the energy from the wind

air would move away with the speed zeroair would move away with the speed zero air prevented from entering the rotor of the turbine air prevented from entering the rotor of the turbine

If the designer did the exact opposite and allowed the wind to pass If the designer did the exact opposite and allowed the wind to pass through the wind turbine without being hindered at all, again, through the wind turbine without being hindered at all, again, energy will not be cultivated, energy will not be cultivated,

since the rotor blades would not be spun, the since the rotor blades would not be spun, the shaft wouldn’t spinshaft wouldn’t spin kinetic energy would not be converted into electricitykinetic energy would not be converted into electricity

Betz Law designer of a wind turbine must find an ideal designer of a wind turbine must find an ideal

balance between these two extremesbalance between these two extremes Fortunately for wind energy advocates and Fortunately for wind energy advocates and

enthusiasts there is a simple answer to this enthusiasts there is a simple answer to this dilemmadilemma

Under Betz Law an ideal wind turbine would slow Under Betz Law an ideal wind turbine would slow down the wind by 2/3 of its original speed (the down the wind by 2/3 of its original speed (the capture of 59.6% of the wind’s speed). capture of 59.6% of the wind’s speed).

Site Limitations The direction that wind travels in The direction that wind travels in angel of the turbine’s rotors are angel of the turbine’s rotors are

important limitations and considerationsimportant limitations and considerations Wind at a site is being slowed down by each Wind at a site is being slowed down by each

turbineturbine limit to the amount of individual units a site can limit to the amount of individual units a site can

supportsupport NIMBY NIMBY BirdsBirds

by by M.V.V.AJAYM.V.V.AJAY