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Academic Year2012-2013

Dr Ben MehenniUoG-

11/6/2012

Fundamentals of

Wind Energy Technology

EM3S29: Sustainable Energy Technology

We know the science. We have predicted the threats.

Its time for action.

California Governors- Arnold Shwarzeneger

The Best in Life are Free !Sunshine Sun Solar

Air

Wind

Rain Watersea,riverWave, Tide

Earth Undergr

ound

Geo-thermal

Recycles Rubbish Bio-mass

Love, Friendship, Freedom etc.

http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34http://www.google.co.uk/imgres?q=sailing+ships&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvnsb&tbnid=Sj5WZ77KpS8GvM:&imgrefurl=http://karenswhimsy.com/sailing-ships.shtm&docid=vWT85DBTe6cLdM&imgurl=http://karenswhimsy.com/public-domain-images/sailing-ships/images/sailing-ships-4.jpg&w=500&h=357&ei=6K2uTrqBKMT_8QPUkYSPDg&zoom=1http://www.google.co.uk/imgres?q=blowing+wind+pictures&start=351&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=whPc97_7gRAhDM:&imgrefurl=http://www.featurepics.com/selections/blowing-in-the-wind-1018.htm&docid=-2fL1kGcyBK4PM&imgurl=http://www.featurepics.com/FI/Thumb/20080103/Blowing-Wind-562934.jpg&w=130&h=86&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=172&sig=108438892324911077429&page=41&tbnh=68&tbnw=104&ndsp=8&ved=1t:429,r:0,s:351&tx=52&ty=34

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An occluded mesocyclone tornado

Wind distribution

Introduction

Wind is theflowofgaseson a large scale. OnEarth, wind consists of the bulk movement of air.

Inmeteorology, winds are often referred to according to their strength, and the direction from

which the wind is blowing.

The two main causes of large scale atmospheric circulation are the differential heating

between the equator and the poles, and the rotation of the planet(Coriolis effect).

Within the tropics,thermal lowcirculations over terrain and high plateaus can drivemonsoon

circulations. In coastal areas the sea breeze/land

breeze cycle can define local winds; in areas that have

variable terrain, mountain and valley breezes can

dominate local winds.Wind is caused by differences in pressure. When a

difference in pressure exists, the air is acceleratedfrom 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 (theatmospheric circulation) are:

The differential heating between the equatorand the poles (difference in absorption of

solar energyleading tobuoyancy forces) and Therotation of the planet.

Thus, indirectly Wind Energy is Solar Energy!

Outside the tropics and aloft from frictional effects of

the earth surface, the large-scale winds tend to approach geostrophic balance. Near the

Earth's surface, friction causes the wind to be slower

than it would be otherwise. Surface friction also causes

winds to blow more inward into low pressure areas.

Winds defined by an equilibrium of physical forces are

used in the decomposition and analysis of wind profiles

as shown in sections below. They are useful for

simplifying the

atmosphericequations of

motion and for making

qualitative arguments

about the horizontal and

vertical distribution of

winds.

P V = n RT

http://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Thermal_lowhttp://en.wikipedia.org/wiki/Thermal_lowhttp://en.wikipedia.org/wiki/Thermal_lowhttp://en.wikipedia.org/wiki/Monsoonhttp://en.wikipedia.org/wiki/Monsoonhttp://en.wikipedia.org/wiki/Monsoonhttp://en.wikipedia.org/wiki/Sea_breezehttp://en.wikipedia.org/wiki/Pressure_gradient_forcehttp://en.wikipedia.org/wiki/Pressure_gradient_forcehttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Buoyancy_forcehttp://en.wikipedia.org/wiki/Buoyancy_forcehttp://en.wikipedia.org/wiki/Buoyancy_forcehttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Geostrophic_balancehttp://en.wikipedia.org/wiki/Geostrophic_balancehttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Equations_of_motionhttp://en.wikipedia.org/wiki/Equations_of_motionhttp://en.wikipedia.org/wiki/Equations_of_motionhttp://en.wikipedia.org/wiki/Equations_of_motionhttp://en.wikipedia.org/wiki/Equations_of_motionhttp://en.wikipedia.org/wiki/Equations_of_motionhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Geostrophic_balancehttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Buoyancy_forcehttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Pressure_gradient_forcehttp://en.wikipedia.org/wiki/Sea_breezehttp://en.wikipedia.org/wiki/Monsoonhttp://en.wikipedia.org/wiki/Thermal_lowhttp://en.wikipedia.org/wiki/Coriolis_effecthttp://en.wikipedia.org/wiki/Atmospheric_circulationhttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Flux

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A windmill style of anemometer

Measurement

Wind direction is reported by the direction from which it originates. For

example, a northerly wind blows from the north to the south. Weather vanes

pivot to indicate the direction of the wind.

Wind speed is measured by anemometers, most commonly

using rotating cups or propellers. When a high measurement

frequency is needed (such as in research applications), wind

can be measured by the propagation speed of ultrasound

signals or by the effect of ventilation on the resistance of a

heated wire. Another type of anemometer usespitot tubesthat

take advantage of the pressure differential between an inner

tube and an outer tube that is exposed to the wind to

determine the dynamic pressure, which is then used to

compute the wind speed.

Sustained wind speeds are reported globally at a 10 meters

height and are averaged over a 10 minute time frame.

Remote sensingtechniques for wind includeSODAR,DopplerLIDARsandRADARs, which can

measure the Doppler shiftofelectromagnetic radiationscattered or reflected off suspended

aerosols or molecules, and radiometers and radars can be used to measure the surface

roughness of the ocean from space or airplanes. Ocean roughness can be used to estimate

wind velocity close to the sea surface over oceans. Geostationary satellite imagery can be used

to estimate the winds throughout the atmosphere based upon how far clouds move from one

image to the next.

Beaufort wind force scale provides an empirical

description of wind speed based on observed sea

conditions. The scale has 17 levels. There are

general terms that differentiate winds of different

average speeds as shown in the table below used

by Regional Specialized Meteorological Centers

worldwide:

http://en.wikipedia.org/wiki/Wind_directionhttp://en.wikipedia.org/wiki/Weather_vanehttp://en.wikipedia.org/wiki/Anemometerhttp://en.wikipedia.org/wiki/Anemometerhttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Pitot_tubehttp://en.wikipedia.org/wiki/Pitot_tubehttp://en.wikipedia.org/wiki/Pitot_tubehttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/SODARhttp://en.wikipedia.org/wiki/SODARhttp://en.wikipedia.org/wiki/SODARhttp://en.wikipedia.org/wiki/Doppler_effecthttp://en.wikipedia.org/wiki/Doppler_effecthttp://en.wikipedia.org/wiki/LIDARhttp://en.wikipedia.org/wiki/LIDARhttp://en.wikipedia.org/wiki/LIDARhttp://en.wikipedia.org/wiki/RADARhttp://en.wikipedia.org/wiki/RADARhttp://en.wikipedia.org/wiki/RADARhttp://en.wikipedia.org/wiki/Doppler_shifthttp://en.wikipedia.org/wiki/Doppler_shifthttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Aerosolhttp://en.wikipedia.org/wiki/Aerosolhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Radiometerhttp://en.wikipedia.org/wiki/Radiometerhttp://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/Regional_Specialized_Meteorological_Centrehttp://en.wikipedia.org/wiki/Regional_Specialized_Meteorological_Centrehttp://en.wikipedia.org/wiki/Regional_Specialized_Meteorological_Centrehttp://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/Radiometerhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Aerosolhttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Doppler_shifthttp://en.wikipedia.org/wiki/RADARhttp://en.wikipedia.org/wiki/LIDARhttp://en.wikipedia.org/wiki/Doppler_effecthttp://en.wikipedia.org/wiki/SODARhttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Pitot_tubehttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Anemometerhttp://en.wikipedia.org/wiki/Weather_vanehttp://en.wikipedia.org/wiki/Wind_directionhttp://www.google.co.uk/imgres?q=blowing+wind+images&start=243&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=oxS4xFbsxe2J0M:&imgrefurl=http://www.proprofs.com/flashcards/cardshowall.php?title=scientific-tools&docid=SyhGcbE_7-9SiM&imgurl=http://www.proprofs.com/flashcards/upload/q4380592.jpg&w=141&h=138&ei=V7KuTovELYOi8QPD2rTACw&zoom=1&chk=sbghttp://www.google.co.uk/imgres?q=blowing+wind+pictures&start=504&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=LmkCr6Y7BoiNdM:&imgrefurl=http://diyhomemadeenergy-akd545.blogspot.com/2011/10/wind-energy-conversion-systems.html&docid=OQEC0HK0BXJNFM&imgurl=http://upload.wikimedia.org/wikipedia/commons/c/c0/Cretan_bladed_rotor_wind_energy_harvester.JPG&w=1892&h=2584&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=562&sig=108438892324911077429&page=58&tbnh=114&tbnw=92&ndsp=10&ved=1t:429,r:2,s:504&tx=55&ty=59http://en.wikipedia.org/wiki/File:Young_wind_monitor.jpghttp://www.google.co.uk/imgres?q=blowing+wind+images&start=243&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=oxS4xFbsxe2J0M:&imgrefurl=http://www.proprofs.com/flashcards/cardshowall.php?title=scientific-tools&docid=SyhGcbE_7-9SiM&imgurl=http://www.proprofs.com/flashcards/upload/q4380592.jpg&w=141&h=138&ei=V7KuTovELYOi8QPD2rTACw&zoom=1&chk=sbghttp://www.google.co.uk/imgres?q=blowing+wind+pictures&start=504&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=LmkCr6Y7BoiNdM:&imgrefurl=http://diyhomemadeenergy-akd545.blogspot.com/2011/10/wind-energy-conversion-systems.html&docid=OQEC0HK0BXJNFM&imgurl=http://upload.wikimedia.org/wikipedia/commons/c/c0/Cretan_bladed_rotor_wind_energy_harvester.JPG&w=1892&h=2584&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=562&sig=108438892324911077429&page=58&tbnh=114&tbnw=92&ndsp=10&ved=1t:429,r:2,s:504&tx=55&ty=59http://en.wikipedia.org/wiki/File:Young_wind_monitor.jpghttp://www.google.co.uk/imgres?q=blowing+wind+images&start=243&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=oxS4xFbsxe2J0M:&imgrefurl=http://www.proprofs.com/flashcards/cardshowall.php?title=scientific-tools&docid=SyhGcbE_7-9SiM&imgurl=http://www.proprofs.com/flashcards/upload/q4380592.jpg&w=141&h=138&ei=V7KuTovELYOi8QPD2rTACw&zoom=1&chk=sbghttp://www.google.co.uk/imgres?q=blowing+wind+pictures&start=504&hl=en&sa=X&biw=819&bih=457&tbm=isch&prmd=imvns&tbnid=LmkCr6Y7BoiNdM:&imgrefurl=http://diyhomemadeenergy-akd545.blogspot.com/2011/10/wind-energy-conversion-systems.html&docid=OQEC0HK0BXJNFM&imgurl=http://upload.wikimedia.org/wikipedia/commons/c/c0/Cretan_bladed_rotor_wind_energy_harvester.JPG&w=1892&h=2584&ei=BquuTv76NdHC8QO09cyPCw&zoom=1&chk=sbg&iact=rc&dur=562&sig=108438892324911077429&page=58&tbnh=114&tbnw=92&ndsp=10&ved=1t:429,r:2,s:504&tx=55&ty=59http://en.wikipedia.org/wiki/File:Young_wind_monitor.jpg

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Wind lottin within a station model

General wind classifications Tropical cyclone classifications (all winds are 10-minute averages)

Beaufortscale[16]

10-minutesustained winds(knots)

Generalterm

N IndianOceanIMD

SW IndianOceanMF

AustraliaBOM

SW PacificFMS

NWPacificJMA

NWPacificJTWC

NE Pacific & NAtlanticNHC&CPHC

0 120Super cyclonic

stormMajor hurricane (5)

The station model plotted on surface weather maps uses a wind barb to show both wind

direction and speed. The wind barb shows the

speed using "flags" on the end.

Each half of a flag depicts 5 knots (9.3 km/h) ofwind.

Each full flag depicts 10 knots (19 km/h) ofwind.

Each pennant (filled triangle) depicts 50 knots(93 km/h) of wind.

Winds are depicted as blowing from the direction

the barb is facing. Therefore, a northeast wind willbe depicted with a line extending from the cloud

circle to the northeast, with flags indicating wind

speed on the northeast end of this line. Once

plotted on a map, an analysis of isotachs (lines of

equal wind speeds) can be accomplished. Isotachs

are particularly useful in diagnosing the location of

the jet stream on upper level constant pressure

charts.

10 knots = 5 m/s

http://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/Wind#cite_note-Beaufort-15http://en.wikipedia.org/wiki/Wind#cite_note-Beaufort-15http://en.wikipedia.org/wiki/Wind#cite_note-Beaufort-15http://en.wikipedia.org/wiki/Knot_(speed)http://en.wikipedia.org/wiki/Knot_(speed)http://en.wikipedia.org/wiki/Knot_(speed)http://en.wikipedia.org/wiki/Indian_Meteorological_Departmenthttp://en.wikipedia.org/wiki/Indian_Meteorological_Departmenthttp://en.wikipedia.org/wiki/M%C3%A9t%C3%A9o-Francehttp://en.wikipedia.org/wiki/M%C3%A9t%C3%A9o-Francehttp://en.wikipedia.org/wiki/Bureau_of_Meteorology_(Australia)http://en.wikipedia.org/wiki/Bureau_of_Meteorology_(Australia)http://en.wikipedia.org/wiki/Fiji_Meteorological_Servicehttp://en.wikipedia.org/wiki/Fiji_Meteorological_Servicehttp://en.wikipedia.org/wiki/Japan_Meteorological_Agencyhttp://en.wikipedia.org/wiki/Japan_Meteorological_Agencyhttp://en.wikipedia.org/wiki/Joint_Typhoon_Warning_Centerhttp://en.wikipedia.org/wiki/Joint_Typhoon_Warning_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/Central_Pacific_Hurricane_Centerhttp://en.wikipedia.org/wiki/Central_Pacific_Hurricane_Centerhttp://en.wikipedia.org/wiki/Central_Pacific_Hurricane_Centerhttp://en.wikipedia.org/wiki/Station_modelhttp://en.wikipedia.org/wiki/Station_modelhttp://en.wikipedia.org/wiki/Weather_maphttp://en.wikipedia.org/wiki/Weather_maphttp://en.wikipedia.org/wiki/Pennant_(commissioning)http://en.wikipedia.org/wiki/Pennant_(commissioning)http://en.wikipedia.org/wiki/Isotachhttp://en.wikipedia.org/wiki/Isotachhttp://en.wikipedia.org/wiki/File:Wind_barbs.gifhttp://en.wikipedia.org/wiki/Isotachhttp://en.wikipedia.org/wiki/Pennant_(commissioning)http://en.wikipedia.org/wiki/Weather_maphttp://en.wikipedia.org/wiki/Station_modelhttp://en.wikipedia.org/wiki/Central_Pacific_Hurricane_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/Joint_Typhoon_Warning_Centerhttp://en.wikipedia.org/wiki/Japan_Meteorological_Agencyhttp://en.wikipedia.org/wiki/Fiji_Meteorological_Servicehttp://en.wikipedia.org/wiki/Bureau_of_Meteorology_(Australia)http://en.wikipedia.org/wiki/M%C3%A9t%C3%A9o-Francehttp://en.wikipedia.org/wiki/Indian_Meteorological_Departmenthttp://en.wikipedia.org/wiki/Knot_(speed)http://en.wikipedia.org/wiki/Wind#cite_note-Beaufort-15http://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/Beaufort_scalehttp://en.wikipedia.org/wiki/File:Wind_barbs.gif

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Sea breeze (occurs at daytime

Land breeze (occurs at night)

Mountain wave schematic. The wind flows towardsa mountain and produces a first oscillation (A). A

second wave occurs further away and higher. The

lenticular clouds form at the peak of the waves (B).

Sea and land breezes

In coastal regions, sea breezes and land breezes can be important factors in a location's

prevailing winds. The sea is warmed by the sun

more slowly because of water's greater specific

heatcompared to land. As the temperature of the

surface of the land rises, the land heats the air

above it by conduction. The warm air is less dense

than the surrounding environment and so it rises.

This causes a pressure gradient of about

2 millibars from the ocean to the land. The cooler

air above the sea, now with higher sea level

pressure, flows inland into the lower pressure,

creating a cooler breeze near the coast. When

large-scale winds are calm, the strength of the sea

breeze is directly proportional to the temperature

difference between the land mass and the sea. If an

offshore wind of 8 knots (4m/s) exists, the sea

breeze is not likely to develop.

At night, the land cools off more quickly than the ocean because of differences in their specific

heat values. When the temperature onshore cools below the temperature offshore, the

pressure over the water will be lower than that of the land. Thus establishing a land breeze as

long as an onshore wind is not strong enough to oppose it.

Near mountains

Over elevated surfaces, heating of the ground exceeds the

heating of the surrounding air at the same altitude,

creating an associated thermal low over the terrain and

changing the wind circulation of the region. In areas

where there is rugged topography that significantly

interrupts the environmental wind flow, the wind

circulation between mountains and valleys is the most

important contributor to the prevailing winds. Hills and

valleys substantially distort the airflow by increasingfriction between the atmosphere and landmass by acting

as a physical block to the flow, deflecting the wind

parallel to the range just upstream of the topography,

which is known as a barrier jet. This barrier jet can

increase the low level wind by 45 percent. Wind direction

also changes because of the contour of the land.

Jagged terrain combines to produce unpredictable flow

patterns and turbulence. Strongupdrafts, downdrafts and

eddies develop as the air flows over hills and downvalleys.

http://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Landformhttp://en.wikipedia.org/wiki/Landformhttp://en.wikipedia.org/wiki/Sea_level_pressurehttp://en.wikipedia.org/wiki/Sea_level_pressurehttp://en.wikipedia.org/wiki/Sea_level_pressurehttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Topographyhttp://en.wikipedia.org/wiki/Topographyhttp://en.wikipedia.org/wiki/Barrier_jethttp://en.wikipedia.org/wiki/Barrier_jethttp://en.wikipedia.org/wiki/Updrafthttp://en.wikipedia.org/wiki/Updrafthttp://en.wikipedia.org/wiki/Updrafthttp://en.wikipedia.org/wiki/Eddieshttp://en.wikipedia.org/wiki/Eddieshttp://en.wikipedia.org/wiki/Eddieshttp://en.wikipedia.org/wiki/Updrafthttp://en.wikipedia.org/wiki/Barrier_jethttp://en.wikipedia.org/wiki/Topographyhttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Sea_level_pressurehttp://en.wikipedia.org/wiki/Sea_level_pressurehttp://en.wikipedia.org/wiki/Landformhttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/File:Vol_d'onde.svghttp://en.wikipedia.org/wiki/File:Vol_d'onde.svg

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The kinetic energy increases at the expense of the

fluid pressure, as shown by the difference in height

of the two columnsof water

Hodographplot of wind vectors at various

heights in the troposphere, which is used

to diagnose verticalwind shear

The total amount of economically extractable power available from the wind is considerably more than present human power usefrom all sources. An estimated72 TeraWatt (TW) of wind power on the Earth potentially can be commercially viable, comparedto about15 TW average global power consumptionfrom all sources in 2005. Not all the energy of the wind flowing past a givenoint can be recovered seeBetz' law .

If there is apassin the mountain range, winds will rush

through the pass with considerable speed because of the

Bernoulli principle that describes an inverse

relationship between speed and pressure.

In fluid dynamics,Bernoulli's principle states that for an

inviscid (no viscosity) flow, an increase in the speed of thefluid occurs simultaneously with a decrease inpressureor a

decrease in the fluid's potential energy. The airflow can

remain turbulent and erratic for some distance

downwind into the flatter countryside. Cool winds

accelerating through mountain gaps have been given

regional names.

Wind power density

A yardstick used to determine the best locations for wind energy

development is referred to as Wind Power Density (WPD). It is a

calculation relating to the effective force of the wind at a particular

location, frequently expressed in terms of the elevation above

ground level over a period of time. It takes into account wind

velocity and mass. Color coded maps are prepared for a particular

area are described as, for example, "mean annual power density at

50 meters.

One study indicates that an entirely renewable energy supply

based on 70 percent wind is attainable at today's power prices by

linking wind farms with an HVDC supergrid. At the end of 2008, worldwide nameplatecapacityof wind-powered generators was 120.8 Gigawatts.

Wind shear

Wind shear orwind gradient, is a difference in wind speed

and direction over a relatively short distance in the Earth's

atmosphere. Wind shear can be broken down into vertical

and horizontal components, with horizontal wind shear

seen acrossweather frontsand near the coast, and vertical

shear typically near the surface. It is a phenomenon

occurring over a very small distance caused by

thunderstorms, weather fronts, areas of locally higher low

level winds referred to as low level jets, near mountains,

radiation inversions that occur because of clear skies and

calm winds, buildings,wind turbines, andsailboats.

Distribution of wind speed

http://en.wikipedia.org/wiki/Fluid_pressurehttp://en.wikipedia.org/wiki/Fluid_pressurehttp://en.wikipedia.org/wiki/Hodographhttp://en.wikipedia.org/wiki/Hodographhttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Wind_shearhttp://c/Users/HOME/Desktop/11http://c/Users/HOME/Desktop/11http://c/Users/HOME/Desktop/11http://en.wikipedia.org/wiki/World_energy_resources_and_consumptionhttp://en.wikipedia.org/wiki/World_energy_resources_and_consumptionhttp://en.wikipedia.org/wiki/World_energy_resources_and_consumptionhttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/Mountain_passhttp://en.wikipedia.org/wiki/Mountain_passhttp://en.wikipedia.org/wiki/Mountain_passhttp://en.wikipedia.org/wiki/Bernoulli_principlehttp://en.wikipedia.org/wiki/Bernoulli_principlehttp://en.wikipedia.org/wiki/Fluid_dynamicshttp://en.wikipedia.org/wiki/Inviscid_flowhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/High-voltage_direct_currenthttp://en.wikipedia.org/wiki/High-voltage_direct_currenthttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Wind_gradienthttp://en.wikipedia.org/wiki/Wind_gradienthttp://en.wikipedia.org/wiki/Wind_gradienthttp://en.wikipedia.org/wiki/Weather_frontshttp://en.wikipedia.org/wiki/Weather_frontshttp://en.wikipedia.org/wiki/Weather_frontshttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Mountainhttp://en.wikipedia.org/wiki/Mountainhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Sailboathttp://en.wikipedia.org/wiki/Sailboathttp://en.wikipedia.org/wiki/Sailboathttp://en.wikipedia.org/wiki/Sailboathttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Mountainhttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Weather_frontshttp://en.wikipedia.org/wiki/Wind_gradienthttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/High-voltage_direct_currenthttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Inviscid_flowhttp://en.wikipedia.org/wiki/Fluid_dynamicshttp://en.wikipedia.org/wiki/Bernoulli_principlehttp://en.wikipedia.org/wiki/Mountain_passhttp://en.wikipedia.org/wiki/File:Hodographe_NOAA.PNGhttp://en.wikipedia.org/wiki/File:Hodographe_NOAA.PNGhttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/World_energy_resources_and_consumptionhttp://c/Users/HOME/Desktop/11http://en.wikipedia.org/wiki/File:Hodographe_NOAA.PNGhttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Hodographhttp://en.wikipedia.org/wiki/File:Hodographe_NOAA.PNGhttp://en.wikipedia.org/wiki/Fluid_pressurehttp://en.wikipedia.org/wiki/Fluid_pressure

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Wind Rose

The strength of wind varies, and an average value for a given location does not alone indicate

the amount of energy a wind turbine could produce

there. To assess the frequency of wind speeds at a

particular location, a probability distribution

function is often fit to the observed data. Different

locations will have different wind speed

distributions. The Weibull model closely mirrorsthe actual distribution of hourly wind speeds at

many locations. If the Weibull factor (k=2) then

distribution becomes the Rayleigh distribution

often used as a less accurate, but simpler model (as

will be shown in the following sections).

Capacity factor

The netcapacity factor of apower plantis the ratio of the actual output of a power plant over

a period of time and its output if it had operated at fullnameplate capacitythe entire time. Tocalculate the capacity factor, total energy the plant produced during a period of time and

divide by the energy the plant would have produced at full capacity. Capacity factors vary

greatly depending on the type of fuel that is used and the design of the plant. The capacity

factor should not be confused with theavailability factoror withefficiency.

Sample calculations

Baseload power plant

Abase load power plantwith a capacity of 1,000 MW might produce 648,000 megawatt-hours

in a 30-day month. The number of megawatt-hours that would have been produced had theplant been operating at full capacity can be determined by multiplying the plant's maximum

capacity by the number of hours in the time period. 1,000 MW X 30 days X 24 hours/day is

720,000 megawatt-hours. The capacity factor is determined by dividing the actual output with

the maximum possible output. In this case, the capacity factor is: 0.9 (90%).

Hydroelectric dam

As of 2010, Three Gorges Dam is the largest power generating station in the world bynameplate capacity. In 2009, not yet fully complete, it had 26 main generator units @ 700 MW

and two auxiliary generator units @ 50 MW for a total installed capacity of 18,300 MW. Total

generation in 2009 was 79.47 TWh, for a capacity factor of: just under 50%:

Hoover Damhas a nameplate capacity of 2080 MW and an annual generation averaging 4.2

TWh. (The annual generation has varied between a high of 10.348 TWh in 1984, and a low of

2.648 TWh in 1956.) Taking the average figure for annual generation gives a capacity factor

of:

Wind farm

http://en.wikipedia.org/wiki/Weibull_distributionhttp://en.wikipedia.org/wiki/Weibull_distributionhttp://en.wikipedia.org/wiki/Rayleigh_distributionhttp://en.wikipedia.org/wiki/Rayleigh_distributionhttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Intermittent_power_source#Terminologyhttp://en.wikipedia.org/wiki/Intermittent_power_source#Terminologyhttp://en.wikipedia.org/wiki/Intermittent_power_source#Terminologyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Fuelhttp://en.wikipedia.org/wiki/Fuelhttp://en.wikipedia.org/wiki/Availability_factorhttp://en.wikipedia.org/wiki/Availability_factorhttp://en.wikipedia.org/wiki/Availability_factorhttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/Base_load_power_planthttp://en.wikipedia.org/wiki/Base_load_power_planthttp://en.wikipedia.org/wiki/Base_load_power_planthttp://en.wikipedia.org/wiki/Three_Gorges_Damhttp://en.wikipedia.org/wiki/Three_Gorges_Damhttp://en.wikipedia.org/wiki/Hoover_Damhttp://en.wikipedia.org/wiki/Hoover_Damhttp://en.wikipedia.org/wiki/Hoover_Damhttp://en.wikipedia.org/wiki/Three_Gorges_Damhttp://en.wikipedia.org/wiki/Base_load_power_planthttp://en.wikipedia.org/wiki/Betz%27_lawhttp://en.wikipedia.org/wiki/Availability_factorhttp://en.wikipedia.org/wiki/Fuelhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Intermittent_power_source#Terminologyhttp://en.wikipedia.org/wiki/Power_planthttp://en.wikipedia.org/wiki/Rayleigh_distributionhttp://en.wikipedia.org/wiki/Weibull_distribution

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For wind:

Betz limit:

Betz's law is a theory about the maximum possible energy to be derived from a "hydraulic wind engine", or a wind

turbine well before the advent of the modern 3-blade wind turbine that generates electricity

TheBurton Wold Wind Farmconsists of tenEnerconE70-E4wind turbines@ 2MW

nameplate capacityfor a total installed capacity of 20 MW. In 2008 the wind farm generated

43,416Megawatt-hoursof electricity. Note 2008 was a leap year. The capacity factor for this

wind farm is:

under 25%:

Reasons for reduced capacity factor

There are several reasons why a plant would have a capacity factor lower than 100%:

The first reason is that it might be out of service or operating at reduced output for part of the timedue to equipment failures or routine maintenance. This accounts for most of the unused capacity of baseload power plants. Base load plants have the lowest costs per unit of electricity because they aredesigned for maximum efficiency and are operated continuously at high output. Geothermal plants,nuclear plants,coal plantsandbioenergy plantsthat burn solid material are almost always operated asbase load plants.

The second reason that a plant would have a capacity factor lower than 100% is that output is curtailedbecause the electricity is not needed or because the price of electricity is too low to make productioneconomical. This accounts for most of the unused capacity ofpeaking power plants. Peaking plants mayoperate for only a few hours per year or up to several hours per day. Their electricity is relativelyexpensive. It is uneconomical, even wasteful, to make a peaking power plant as efficient as a base loadplant because they do not operate enough to pay for the extra equipment cost, and perhaps not enoughto offset theembodied energyof the additional components.

A third reason is a variation on the second: the operators of a hydroelectric dam may uprate itsnameplate capacity by adding more generator units. Since the supply of fuel (i.e. water) remainsunchanged, the up-rated dam obtains a higher peak output in exchange for a lower capacity factor.Because hydro plants are highly dispatchable, they are able to act as load following power plants.Having a higher peak capacity allows a dam's operators to sell more of the annual output of electricityduring the hours of highest electricity demand (and thus the highestspot price). In practical terms, up-rating a dam allows it tobalancea larger amount of intermittent energy sourceson the grid such aswind farmsandsolar power plants, and to compensate for unscheduled shutdowns of baseload powerplants, or brief surges in demand for electricity.

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http://en.wikipedia.org/wiki/Burton_Wold_Wind_Farmhttp://en.wikipedia.org/wiki/Burton_Wold_Wind_Farmhttp://en.wikipedia.org/wiki/Burton_Wold_Wind_Farmhttp://en.wikipedia.org/wiki/Enerconhttp://en.wikipedia.org/wiki/Enerconhttp://en.wikipedia.org/wiki/Enerconhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Megawatt-hourhttp://en.wikipedia.org/wiki/Megawatt-hourhttp://en.wikipedia.org/wiki/Megawatt-hourhttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Fossil_fuel_power_planthttp://en.wikipedia.org/wiki/Fossil_fuel_power_planthttp://en.wikipedia.org/wiki/Fossil_fuel_power_planthttp://en.wikipedia.org/wiki/Bioenergyhttp://en.wikipedia.org/wiki/Bioenergyhttp://en.wikipedia.org/wiki/Bioenergyhttp://en.wikipedia.org/wiki/Peaking_power_planthttp://en.wikipedia.org/wiki/Peaking_power_planthttp://en.wikipedia.org/wiki/Peaking_power_planthttp://en.wikipedia.org/wiki/Embodied_energyhttp://en.wikipedia.org/wiki/Embodied_energyhttp://en.wikipedia.org/wiki/Embodied_energyhttp://en.wikipedia.org/wiki/Grid_energy_storage#Hydroelectric_dam_upratinghttp://en.wikipedia.org/wiki/Grid_energy_storage#Hydroelectric_dam_upratinghttp://en.wikipedia.org/wiki/Grid_energy_storage#Hydroelectric_dam_upratinghttp://en.wikipedia.org/wiki/Load_following_power_planthttp://en.wikipedia.org/wiki/Load_following_power_planthttp://en.wikipedia.org/wiki/Spot_pricehttp://en.wikipedia.org/wiki/Spot_pricehttp://en.wikipedia.org/wiki/Spot_pricehttp://en.wikipedia.org/wiki/Load_balancing_(electrical_power)http://en.wikipedia.org/wiki/Load_balancing_(electrical_power)http://en.wikipedia.org/wiki/Load_balancing_(electrical_power)http://en.wikipedia.org/wiki/Intermittent_energy_sourcehttp://en.wikipedia.org/wiki/Intermittent_energy_sourcehttp://en.wikipedia.org/wiki/Intermittent_energy_sourcehttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Solar_power_planthttp://en.wikipedia.org/wiki/Solar_power_planthttp://en.wikipedia.org/wiki/Solar_power_planthttp://en.wikipedia.org/wiki/Solar_power_planthttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Intermittent_energy_sourcehttp://en.wikipedia.org/wiki/Load_balancing_(electrical_power)http://en.wikipedia.org/wiki/Spot_pricehttp://en.wikipedia.org/wiki/Load_following_power_planthttp://en.wikipedia.org/wiki/Grid_energy_storage#Hydroelectric_dam_upratinghttp://en.wikipedia.org/wiki/Grid_energy_storage#Hydroelectric_dam_upratinghttp://en.wikipedia.org/wiki/Embodied_energyhttp://en.wikipedia.org/wiki/Peaking_power_planthttp://en.wikipedia.org/wiki/Bioenergyhttp://en.wikipedia.org/wiki/Fossil_fuel_power_planthttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Megawatt-hourhttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Enerconhttp://en.wikipedia.org/wiki/Burton_Wold_Wind_Farm

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Distribution of wind speed (red) and energy (blue). The histogram

shows measured data, while the curve is the Rayleigh model

distribution for the same average wind speed. Energy is the Betz limit

throu h a 100 m diameter circle facin directl into the wind.

Wind Energy

Because so much power is generated by higher wind speed, much of the energy comes in

short bursts. The example sample implies that half of the energy available arrived in just 15%

of the operating time. The consequence is that wind energy is not as consistent as fuel-fired

power plants. Thus, wind power is seen primarily as a fuel saver rather for base load plant

than a capacity saver.

Making wind power more consistentrequires that

various existing technologies and methods be

extended, in particular the use of stronger inter-

regional transmission lines to link widely

distributed wind farms. Problems of variability are

addressed by grid energy storage, batteries,

pumped-storage hydroelectricity and energy

demand management.

Wind regimes are usually represented by Weibull

Probability Distribution (like Poissons Law instatistics)

This is the probability that a particular wind speed (v) will occur over a given time period. k = Shape Parameter C = Scale Parameter (m/s)If we rearrange the previous equation we can find expressions for the probability that the

wind speed (V) will be less than a particular wind speed (Vw)

and an expression for the probability that the wind speed (V) will be greater than a particular

wind speed (Vw)

Energy yield from a wind turbine:

When used with the power curve of a wind turbine, the Weibull distribution allows us to

calculate the energy yield of that wind turbine. First we use the Weibull distribution to

calculate the amount of time that particular wind speeds are likely to occur for over thecourse of the year using the following formula(1) above. By evaluating the formula at different

wind speeds the length of time in hours that each wind speed occurs for over the year can be

estimated (see tutorial).

Electricity generation

In awind farm, individual turbines are interconnected with a medium voltage (often 34.5 kV),

power collection system and a transmission/distribution network. At a substation, this

medium-voltage electric current is increased in voltage with a transformerfor connection to

the high voltageelectric power transmissionsystem.

Note: Any surplus power produced by small (wind farm) micro-generators can, in some jurisdictions, befed into the network grid and sold to the utility companies, producing a retail credit for the micro-

enerators' owners to offset their ener costs.

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Components of a horizontal axis wind turbine

(gearbox, rotor shaft and brake assembly) being lifted

into osition

Wind turbine Technologies

A wind turbine is a rotary device

that extracts energy from the wind.

When the mechanical energy is

converted to electricity, the machine

is called a wind generator, windturbine, wind turbine generator

(WTG), wind power unit (WPU),

wind energy converter (WEC), or

aero-generator.

Wind turbines can rotate about

either a horizontal or a vertical axis.

Horizontal axis

Horizontal-axis wind turbines (HAWT) have the mainrotorshaft andelectrical generatorat

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. Most

have agearbox, which turns the slow rotation of

the blades into a quicker rotation that is more

suitable to drive anelectrical generator.

Since a tower producesturbulencebehind it, the

turbine is usually pointed upwind of the tower.

Turbine blades are made stiff to prevent the

blades from being pushed into the tower by high

winds. Additionally, the blades are placed a

considerable distance in front of the tower and

are sometimes tilted forward into the wind a

small amount.

Downwind machines have been built, despite the problem of turbulence (mast wake), because

they don't need an additional mechanism for keeping them in line with the wind, and because

in high winds the blades can be allowed to bend which reduces their swept area and thus

their wind resistance. Since cyclic (that is repetitive) turbulence may lead to fatiguefailuresmost HAWTs are upwind machines.

They typically had many blades, operated at tip speed ratios, to

match their rated output and usually have good starting torque for

the generators used, charging storage batteries, to provide power.

Such devices are still used in locations where it is too costly to bring in commercial power.

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Three bladed wind turbine

Modern wind turbines

Turbines used in wind farms for commercial

production of electric power are usually three-bladed

and pointed into the wind by computer-controlled

motors. These have high tip speeds, high efficiency,

and low torque ripple, which contribute to good

reliability. The blades are usually colored light gray

to blend in with the clouds and range in length from

20-40m or more. The tubular steel towers range from

60-90m tall. The blades rotate at 10-22 rpm. At 22

rpm, the tip speed exceeds 91 m/s. A gear box is

commonly used for stepping up the speed of the

generator (1500 3000 rpm), although designs may

also use direct drive of an annular generator. Some models operate at constant speed, but

more energy can be collected by variable-speed turbines which use a solid-state power

converter to interface to the transmission system. All turbines are equipped with protective

features to avoid damage at high wind speeds, by featheringthe blades into the wind which

ceases their rotation, supplemented bybrakes.

Advantages Disadvantages

Variable blade pitch, which gives the turbineblades the optimum angle of attack. Allowingthe angle of attack to be remotely adjustedgives greater control, so the turbine collectsthe maximum amount of wind energy for thetime of day and season.The tall tower base allows access to strongerwind in sites with wind shear. In some windshear sites, thewind speed can increaseby 20%and the power output by 34% for every 10meters in elevation.High efficiency, since the blades always moveperpendicular to the wind, receiving powerthrough the whole rotation.The face of a horizontal axis blade is struck bythe wind at a consistent angle regardless of theposition in its rotation. This results in aconsistent lateral wind loading over the courseof a rotation, reducing vibration and audiblenoise coupled to the tower or mount.

The tall towers and blades up to 45m long aredifficult to transport. Transportation can nowamount to 20% of equipment costs.Tall HAWTs are difficult to install, needing verytall and expensive cranes and skilled operators.Massive tower construction is required to supportthe heavy blades, gearbox, and generator.Reflections from tall HAWTs may affect side lobesof radar installations creating signal clutter,although filtering can suppress it.Their height makes them obtrusively visible acrosslarge areas, disrupting the appearance of thelandscape and sometimes creating local opposition.Downwind variants suffer from fatigue andstructural failure caused by turbulence when ablade passes through the tower's wind shadow (forthis reason, the majority of HAWTs use anupwind design, with the rotor facing the wind infront of the tower).HAWTs require an additional yaw controlmechanism to turn the blades and nacelle towardthe wind.In order to minimize fatigue loads due to waketurbulence*, wind turbines are usually sited adistance of 5 rotor diameters away from eachother, but the spacing depends on themanufacturer and the turbine model.

Suffer cyclic stresses and vibration

*Wake turbulence is turbulence that forms behind the turbine body (as in an aircraft as it passes through the air).

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Darrieus Eggbeater"wind turbineVAWT

A helical twisted VAWT-Giromill

Windmill with rotating sails-Savonius

Vertical axis design

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. Key

advantages of this arrangement are that the turbine does not need to be pointed into the wind

to be effective. This is an advantage on sites where the wind direction is highly variable.

With a vertical axis, the generator and gearbox can be placed near the ground, so the towerdoesn't need to support it, and it is more accessible for maintenance. Drawbacks are that

some designs produce pulsatingtorque.

It is difficult to mount vertical-axis turbines on towers, meaning they are often installed

nearer to the base on which they rest, such as the ground or a building rooftop. The wind

speed is slower at a lower altitude, so less wind energy is available for a given size turbine. Air

flow near the ground and other objects can create turbulent flow, which can introduce issues

of vibration, including noise and bearing wear which may increase the maintenance or

shorten the service life. However, when a turbine is mounted on a rooftop, the building

generally redirects wind over the roof with a doubling of the wind speed at the turbine.

Subtypes

Darrieus wind turbineEggbeater" turbines, were named after the

French inventor, Georges Darrieus. They have good efficiency, but

produce large torque ripple and cyclical stress on the tower, which

contributes to poor reliability. They also generally require some

external power source, or an additional Savonius rotor to start

turning, because the starting torque is very low. The torque ripple is

reduced by using three or more blades which results in a higher

solidity for the rotor. Solidity is measured by blade area divided bythe rotor area. Newer turbines are not held up byguy-wiresbut have

an external superstructure connected to the top bearing.

Giromill

A subtype of Darrieus turbine with straight, as opposed to curved,

blades is shown. The cycloturbine variety has variable pitch to

reduce the torque pulsation and is self-starting. The advantages of

variable pitch are: high starting torque; a wide, relatively flat

torque curve; a lower blade speed ratio; a higher coefficient of

performance; more efficient operation in turbulent winds; and a

lower blade speed ratio which lowers blade bending stresses.

Straight, V, or curved blades may be used.

Savonius wind turbine

These are drag-type devices with two (or more) scoops that are

used in anemometers, Flettner vents (commonly seen on bus and

van roofs), and in some high-reliability low-efficiency power

turbines. They are always self-starting if there are at least three

scoops. They sometimes have long helical scoops to give a smooth

torque.

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The Musgrove Wind Turbine-Carmarthen Bay

The Musgrove wind turbine

The blades are vertical for normal power generation but tip or

turn about a horizontal point for control or shut down (i.e.

furled or unfurled-reefed).

Musgrove Vertical-Axis Turbines The VAWT-450 (130 kW)

machine (blades shown as reefed; in operation these become

vertical). The gear-box and generator were at ground level.

Advantages Disadvantages

A massive tower structure is lessfrequently used, as VAWTs are morefrequently mounted with the lower

bearing mounted near the ground.Designs without yaw mechanismsare possible with fixed pitch rotordesigns.The generator of a VAWT can belocated nearer the ground, making iteasier to maintain the moving parts.VAWTs have lower wind startupspeeds than HAWTs. Typically, theystart creating electricity at 10 km/h.VAWTs may be built at locationswhere taller structures are

prohibited.VAWTs situated close to the groundcan take advantage of locationswhere plateaus-flat highlands,hilltops, ridgelines, and passes funnelthe wind and increase its velocity.VAWTs may have a lower noisesignature.

A VAWT that usesguy-wires*to hold it in place puts stresson the bottom bearing as all the weight of the rotor is on thebearing. Guy wires attached to the top bearing increase

downward thrust in wind gusts. Solving this problemrequires a superstructure to hold a top bearing in place toeliminate the downward thrusts of gust events in guy wiredmodels.The stress in each blade due to wind loading changes signtwice during each revolution as the apparent wind directionmoves through 360 degrees. This reversal of the stressincreases the likelihood of blade failure byfatigue.While VAWTs' components are located on the ground, theyare also located under the weight of the structure above it,which can make changing out parts very difficult if thestructure is not designed properly.

Having rotors located close to the ground where wind speedsare lower due to the ground'ssurface drag, VAWTs may notproduce as much energy at a given site as a HAWT with thesame footprint or height.In contrast, all vertical axis wind turbines, and mostproposed airborne wind turbine designs, involve varioustypes of reciprocating actions, requiring airfoil surfaces tobacktrack against the wind for part of the cycle. Backtrackingagainst the wind leads to inherently lower efficiency.

*A guy-wire or guy-rope, or simply a guy, is a tensioned cable designed to add stability to structures

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Turbine design and construction

Wind turbines convert wind energy to electricity for distribution. Conventional horizontal

axis turbines can be divided into three components.

Wind turbines are designed to exploit the wind energy that exists at a location. Aerodynamic

modelingis used to determine the optimum tower height, number of blades, blade shape and

control systems (pitch, stall).

Wind turbine blades are shaped to generate the maximum power from the wind at the

minimum cost. Primarily the design is driven by the aerodynamic requirements, but

economics mean that the blade shape is a compromise to keep the cost of construction

reasonable. In particular, the blade tends to be thicker than the aerodynamic optimum close

to the root, where the stresses due to bending are greatest.

The power available from the wind varies as the cube of the wind speed ( P= V3), so twice

the wind speed means eight times the power. This is why sites have to be selected carefully:

below about 5m/s (10mph) wind speed there is not sufficient power in the wind to be useful.

Conversely, strong gusts provide extremely high levels of power, but it is not economically

viable to build machines to be able to make the most of the power peaks as their capacity

would be wasted most of the time. So the ideal is a site with steady winds and a machine that

is able to make the most of the lighter winds whilst surviving the strongest gusts.

All these effects lead to varying loads on the blades of a turbine as they rotate, and mean that

the aerodynamic and structural design needs to cope with conditions that are rarely optimal.By extracting power, the turbine itself has an effect on the wind: downwind of the turbine the

air moves more slowly than upwind. The wind starts to slow down even before it reaches the

blades, reducing the wind speed through the disc (the imaginary circle formed by the blade

tips, also called the swept area) and hence reducing the available power. So there is an

optimum amount of power to extract from a given disc diameter: try to take too much and the

wind will slow down too much, reducing the available power. In fact the ideal is to reduce the

wind speed by about two thirds downwind of the turbine, though even then the wind just

before the turbine will have lost about a third of its speed. This allows a theoretical maximum

of 59% of the winds power to be captured (this is called Betzs limit). In practice only 40-50%

is achieved by current designs.

Therotorcomponent, which is approximately 20% of the wind turbine cost, includes the blades forconverting wind energy to low speed rotational energy.

The generator component, which is approximately 34% of the wind turbine cost, includes the

electrical generator, the control electronics, and most likely agearboxcomponent for converting the

low speed incoming rotation to high speed rotation suitable for generating electricity.

Thestructural supportcomponent, which is approximately 15% of the wind turbine cost, includes

the tower and rotor yaw mechanism.

Conceptually, wind turbines may also be used in conjunction with a large verticalsolar updraft towerto extract the energy due to air heated by the sun.

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Blade at low, medium & high angles of attack

The total blade area as a fraction of the total swept disc area is called the solidity, and

aerodynamically there is an optimum solidity for a given tip speed; the higher the number of

blades, the narrower each one must be. In practice the optimum solidity is low (only a few

percent) which means that even with only three blades, each one must be very narrow. To slip

through the air easily the blades must be thin relative to their width, so the limited solidity

also limits the thickness of the blades. Furthermore, it becomes difficult to build the blades

strong enough if they are too thin, or the cost per blade increases significantly as moreexpensive materials are required.

For this reason, most large machines do not have more than three blades. The other factor

influencing the number of blades is aesthetics: it is generally accepted that three-bladed

turbines are less visually disturbing than one- or two-bladed designs.

How blades capture wind power

Wind turbine blades work by generating lift

due to their shape. The more curved side

generates low air pressures while high

pressure air pushes on the other side of the

aerofoil. The net result is a lift force

perpendicular to the direction of flow of the

air.

The lift force increases as the blade is turned to present itself at a greater angle to the wind.

This is called the angle of attack. At very large angles of attack the blade stalls and the liftdecreases again. So there is an optimum angle of attack to generate the maximum lift.

There is, unfortunately, also a retarding force on the blade: the drag. This is the force parallelto the wind flow, and also increases with

angle of attack. If the aerofoil shape is good,

the lift force is much bigger than the drag,

but at very high angles of attack, especially

when the blade stalls, the drag increases

dramatically. So at an angle slightly less than

the maximum lift angle, the blade reaches its

maximum lift/drag ratio. The best operating

point will be between these two angles.

Since the drag is in the downwind direction,it may seem that it wouldnt matter for a

wind turbine as the drag would be parallel

to the turbine axis, so wouldnt slow the

rotor down. It would just create thrust, theforce that acts parallel to the turbine axis

hence has no tendency to speed up or slow

down the rotor. When the rotor is stationary

(e.g. just before start-up), this is indeed the

case. However the blades own movement

through the air means that, as far as theblade is concerned, the wind is blowing from

a different angle. This is called apparent

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wind. The apparent wind is stronger than the true wind but its angle is less favourable: it

rotates the angles of the lift and drag to reduce the effect of lift force pulling the blade round

and increase the effect of drag slowing it down. It also means that the lift force contributes to

the thrust on the rotor.

Twist

The closer to the tip of the blade you get,

the faster the blade is moving through the

air and so the greater the apparent wind

angle is. Thus the blade needs to be

turned further at the tips than at the root,

in other words it must be built with a

twist along its length. Typically the twist

is around 10-20 from root to tip. The

requirement to twist the blade has implications on the ease of manufacture.

Because the tip of the blade is moving

faster than the root, it passes through more

volume of air, hence must generate a

greater lift force to slow that air down

enough. In reality the blade can be

narrower close to the tip than near the root

and still generate enough lift.

The optimum tapering of the blade

planform as it goes outboard can be

calculated; roughly speaking the chordshould be inverse to the radius. This

relationship breaks down close to the root

and tip, where the optimum shape changes

to account for tip losses.

We can define a speed ratio such thatrelates the tip speed of the rotor (the

tangential velocity of the rotor tip) to the

undisturbed wind speed.

r = the radius of the blade (m)

=angular velocity (r.p.m)

Tip speed ratio (TSR) is a dimensionless

Variable

We can see that for a certain value of TSR

Cp is a maximum.

This means that to achieve maximum

power extraction from the wind the

rotational speed of the turbine should be

allowed to vary with the incoming wind

speed

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Rotational speed

The speed at which the turbine rotates is a

fundamental choice in the design, and is

defined in terms of the speed of the blade

tips relative to the free wind speed (i.e.

before the wind is slowed down by theturbine). This is called the Tip Speed

Ratio(TSR).

High tip speed ratio means the

aerodynamic force on the blades (due to lift

and drag) is almost parallel to the rotor

axis, so relies on a good lift/drag ratio. The

lift/drag ratio can be affected severely by dirt or roughness on the blades.

Blade Planform

Because the lift force on the blades

generates torque, it has an equal but

opposite effect on the wind, tending to push

it around tangentially in the other direction.

The result is that the air downwind of the

turbine has swirl, i.e. it spins in theopposite direction to the blades. That swirl

represents lost power so reduces the

available power that can be extracted from

the wind.

Power and pitch control

For an economical design, the

maximum performance of the

generator and gearbox need to be

limited to an appropriate level for

the turbines operating environment.

The ideal situation is for the turbine

to be able to extract as much power

as possible from the wind up to the

rated power of the generator, then

limit the power extraction at that

level as the wind increases further.

Stall control

If the blades angle is kept constant, the turbine is unable to respond to changes in wind

speed. Not only does this make it impossible to maintain an optimum angle of attack to

generate the maximum power at varying wind speeds, the only way to depower the machine

in high wind speeds is by relying on the blades to stall (known as passive stall control). Thisdoesnt give the perfectly flat power curve above the rated wind speed shown in the graph

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above, so to limit the maximum power, a passive stall-controlled turbine will usually be

operating somewhat below its maximum potential.

Pitch Control

If instead the blades are attached via a bearing that allows the angle of attack to be varied

(active pitch control), the blades can be angled to maintain optimum efficiency right up to thedesign wind speed (at which the generator is producing its rated output). Above that wind

speed they can be feathered, i.e. rotated in pitch to decrease their angle o f attack and hence

their lift, so controlling the power. In survival conditions, the turbine can be stopped

altogether and the blades feathered to produce no turning force at all.

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A wind farm

A wind farm is a group ofwind turbinesin the same location used for production of electric

power. Individual turbines are interconnected with a medium voltage (usually 34.5 kV) power

collection system and communications network. At a substation, this medium-voltage

electrical current is increased in voltage with atransformerfor connection to the high voltage

transmission system.

A large wind farm may consist of a few dozen to several hundred individual wind turbines,

and cover an extended area of hundreds of square miles, but the land between the turbines

may be used for agricultural or other purposes. A wind farm may be located off-shore to take

advantage of strong winds blowing over the surface of an ocean or lake.

Location planning

As mentioned above, a quantity called the Wind Power Density (WPD) is used to select

locations for wind energy development. The WPD is a calculation relating to theeffective forceof the wind at a particular location, frequently expressed in term of the elevation above

ground level over a period of time. It takes into accountvelocity and mass. Colour-coded maps

are prepared for a particular area describing, for example, "Mean Annual Power Density, at 50

Meters." The results of the above calculation are used in an index developed by the National

Renewable Energy Lab and referred to as "NREL CLASS." The larger the WPD calculation the

higher it is rated by class.

Wind farm sighting can be highly controversial, particularly when sites are picturesque or

environmentally sensitive. Related factors may include having substantial bird life, or

requiring roads to be built through pristine areas. The areas where wind farms are built are

generally non-residential, due to noise concerns and setback requirements.

Access to the power grid is also a factor. The further from the power grid, the more

transmission lines will be needed to span from the farm directly to the power grid.

Alternatively, transformers will have to be built on the premises, depending upon the types of

turbines being used

Usually sites are preselected on basis of awind atlas, and

validated with wind measurements. Meteorological wind

data alone is usually not sufficient for accuratesitingof a

large wind power project. Collection of site specific datafor wind speed and direction is crucial to determining site

potential. Local winds are often monitored for a year or

more, and detailed wind maps constructed before wind

generators are installed.

To collect wind data, a meteorological tower is installed with instruments at various heights

along the tower. All towers include anemometers to determine the wind speed and wind

vanes to determine the direction. The towers generally vary in height from 30 to 60 meters.

The towers primarily are guyed steel-pipe structures which are used for one to two years to

collect data and then are disassembled and removed. Data is collected by a data-logging

device, which stores and transmits data for analysis. The siting of turbines during installation

(a process known as micro-siting) because a difference of 30 m can nearly double energy

production.

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Onshore turbine

For smaller installations where such data collection is too expensive or time consuming, the

normal way that developersprospect for wind-power sites is to look for trees or vegetation

that are permanently "cast" or deformed by the prevailing winds. Another way is to use a

wind-speed survey map, or historical data from a nearby meteorological station, although

these methods are less reliable.

Altitude

The wind blows faster at higher altitudes because of the reduced influence of drag at the

surface or nearer ground. The increase in velocity with altitude is most dramatic away from

the surface and is affected by topography, surface roughness, and upwind obstacles such as

trees or buildings. Typically, the increase of wind speeds with increasing height follows a

wind profile power law, which predicts that wind speed rises proportionally to the seventh

root of altitude.

Wind park effect

The "wind park effect" refers to the loss of output due to mutual interference among turbines.

Wind farms have many turbines, and each extracts some of the energy of the wind. Where

land area is sufficient, turbines are spaced three to five rotor diameters apart perpendicular to

the prevailing wind, and five to ten rotor diameters apart in the direction of the prevailing

wind, to minimize efficiency loss. The loss can be as low as 2% of the combined "nameplate"

rating of the turbines.

Utility-scale wind farms must have access to transmission lines to transport energy. The wind

farm developer may be obligated to install extra equipment or control systems in the wind

farm to meet the technical standards set by the operator of a transmission line. The company

or person that develops the wind farm can then sell the power on the grid through thetransmission lines.

Types

Onshore

Onshoreturbine installations in hilly or

mountainous regions tend to be on

ridgelines generally three kilometers or

more inland from the nearest shoreline.

This is done to exploit the so-calledtopographic acceleration as the wind

accelerates over a ridge. The additional

wind speeds gained in this way make a

significant difference to the amount of

energy that is produced. Great attention

must be paid to the exact positions of

the turbines (a process known as micro-

siting) because a difference of 30 m can

sometimes mean a doubling in output.

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Offshore turbine

Nearshore turbine

Nearshore

Nearshore turbine installations are on land

within three kilometres of a shoreline or, on

water within ten kilometres of land. These

areas are good sites for turbine installation,

because of wind produced by convection dueto differential heating of land and sea each

day. Wind speeds in these zones share the

characteristics of both onshore and offshore

wind, depending on the prevailing wind

direction.

Offshore

Offshore wind development zones are

generally considered to be ten kilometers or

more from land. Offshore wind turbines are

less obtrusive than turbines on land, as

their apparent size and noise is mitigated by

distance. Because water has less surface

roughness than land (especially deeper

water), the average wind speed is usually

considerably higher over open water.

Capacity factors (utilisation rates) are

considerably higher than for onshore and

nearshore locations.

Transporting large wind turbine components (tower sections, nacelles, and blades) is much

easier over water than on land, because ships and barges can handle large loads more easily

than trucks/lorries or trains. On land,large goods vehiclesmust negotiate bends on roadways,

which fixes the maximum length of a wind turbine blade that can move from point to point on

the road network; no such limitation exists for transport on open water.

Offshore wind turbines will probably continue to be the largest turbines in operation, since

the highfixed costsof the installation are spread over more energy production, reducing the

average cost.Turbine components (rotor blades, tower sections) can be transported bybarge,making large parts easier to transport offshore than on land, where turn clearances and

underpass clearances of available roads limit the size of turbine components that can be

moved by truck. Similarly, large construction cranes are difficult to move to remote wind

farms on land, butcrane vesselseasily move over water. Offshore wind farms tend to be quite

large, often involving over 100 turbines.

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