energy in the wind - · pdf file123456 78910 wind distribution frequency(%)

Harnessing Wind Energy – What & How 2/27/2016

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By: Larry A. Villasmil Urdaneta

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An Introductory Course

into Wind Energy

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Energy in the WindThe Wind Resource

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Energy in the Wind

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SECTION 01MAIN TOPICS:

- One: Origin of the Wind…

- Two: Mean Wind Speeds:Maps & AtlasAverage vs. Mean values

- Three: Wind Frequency Distribution…

Fundamental Concepts Review & Evaluation

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Figure 13.1. Global wind flows (Erich Hau)

Energy in the Wind

Global Wind Flows…

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Wind is Solar Energy

Uneven Heating

High/Low Pressure

Coriolis Effect

Inertial Forces

Frictional Forces:‐ Topography ‐ Surface characteristics

Generalizations about regions:‐ Hurricanes/Monsoons/Cyclones‐ Land/Sea breeze.‐ Valley/Mountain winds.‐ Thunderstorms/Tornadoes.

Recirculation “CELLS”

Warmrises

Cooldescends

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Figure 13.2. Global distribution of the mean annual wind speeds @ 10 m (Erich Hau)

Energy in the Wind

Global Annual Mean Wind Speed…

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Source: NREL, http://rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2‐01m.html

Energy in the WindU.S. Atlas

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UNITED STATES ANNUAL AVERAGE WIND POWER


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Source:NREL http://www.nrel.gov/gis/data_wind.html

Energy in the WindN.Y. State Wind Power Class / High Resolution Wind Data Map

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New York annual average Wind Power http://rredc.nrel.gov/wind/pubs/atlas/maps/chap3/3-25m.html

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Mean annual wind speed = “invariable” long‐term mean value at a specific location based on measurements taken over decades.

Mean annual wind speed is not enough for a precise energy calculation.It requires information on how frequent the individual speed can be expected.

The frequency distribution of the annual wind speeds is derived from data measuredat a given elevation.

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CUMULATIVE

RELATIVE

Wind Speed, m/s

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Wind DistributionFrequency (%) vs. Speed (m/s)

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Energy in the WindWind Speed Characterization – Mean vs. Distribution

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0

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Wind DistributionFrequency (%) vs. Speed (m/s)

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‘Weighted Average’ Wind Speed

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‘Average’ Wind Speed


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Mean (Weighted) Wind Speed

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Φi, frequency distribution %.

Given a wind frequency distribution, calculate the mean speed…

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39.5

2.20

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40

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8 16 24Wind Speed, m/s

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Energy in the Wind

What is the mathematical function that best describes the wind resource, and how the mean wind speed is calculated?

FUNDAMENTAL CONCEPTS REVIEW & EVALUATION 01

Did you learn something new? If so, What was it?

What is the origin of the wind? Name three of the main causes.

Energy in the Wind

On a GLOBAL scale what are the zones with best wind resources?

On a NATIONAL scale what are the zones with best wind resources?

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Energy in the Wind

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- Four: Wind Speed Variations:Steadiness…Turbulence…

- Five: Local Wind Flow & TopographyUrban, Obstacles & Remote Locations

- Six: Measuring Wind Speed…



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Energy in the WindWind Resource – Wind Steadiness

Figure 13.10 Diurnal Variations (Erich Hau)

Figure 13.11 Monthly Variations (Erich Hau)

List/Sylt Islands, Greece @ 12 m (1971-80)

Mean Annual Wind Speed = 7.1 m/s

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Energy in the WindWind Resource – Wind Turbulence

Figure 13.13. Measured time history of wind speed (Erich Hau)

Energy SpectrumFigure 13.14 (Erich Hau)

)()( tvVtV TW 0

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14

0 240 480 720 960 1200 1440

Wind Speed, m

/s

Time, min.

Actual Wind Speed Measurement4240 Ontario Center Rd

February 10, 2012

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Energy in the WindSite Selection – Local Wind Flow & Topography

Turbine Relative Size Overview. Gipe, Paul

TransmissionTower

HouseForest

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Ground EffectWizelius, Tore

vH = vref ∙ (H/Href)α

Figure 17.4 Offshore wind farm near Vindeby, off the cost Lolland (Denmark), 1991. (Erich Hau)


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Figure 13.17.Wind turbines installed in aSpanish mountain region, complex terrain.

(Erich Hau)

Figure 4.11 Hill impact

(Tore Wizelius)

Figure 4.10 ‘smooth’ Hill vs. ‘sharp’ Hill


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Energy in the WindSite Selection – Topography & Local Wind Flow

‘Flat’ Terrain for a Large Turbine

Figure 13.15. Definition of “flat countryside” in the environment of a wind turbine(Erich Hau)


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Energy in the WindSite Selection – Topography & Local Wind Flow

Figure 13.16 Flow wake behind an obstacle

(Erich Hau)

OBSTACLES

Figure 4.2Turbulence and Tower Height(Paul Gipe)

2 H

20 H

H

DISTURBEDFLOW

PREVAILINGWIND

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Energy in the WindWind Resource – Determining the wind speed

Figure 13.18. Wind-flagged trees as qualitative indicators of the local wind resources.(Erich Hau)

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Figure 13.20.Wind measuring mast with sensors(Erich Hau)

Figure 13.19. Ultrasonic Anemometer (Erich Hau)

Cup Anemometers

Turbulence Characterization PNLManwell, J.F.

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Energy in the Wind

Describe the operating principle of one wind speed measurement device/method.


Did you learn something new? If so, What is it?

Which are the best sites for wind farms?

Energy in the Wind

What would define a flat terrain in contrast to a hilly terrain?

In an urban setting, how far/above obstacles/buildings should a wind turbine be installed?

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Harvesting Wind EnergyPower in the Wind

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Harvesting Wind Energy

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- Seven: Power in the Wind:‘Mean’ Power vs ‘True’ PowerEnergy Pattern Factor & Power Density

- Eight: Wind Turbine Performance:Power CurveWind Turbine to Wind Resource Power RatioOverall EfficiencyEnergy Yield / Matching Resources


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Energy in the Wind Power in the Wind

Observations

2

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1VmE

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1VAPo

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11Vm

tt

EPo

AVmt

m

2

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1V

t

mPo

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1VAVPo

The power in the wind is directly proportional to the swept area and the CUBE of the wind speed!

The energy in the wind is KINETIC…

Harvesting Wind EnergyPower in the Wind ‐ Energy vs. Power

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Mean Wind Speed

Power in the Wind: Distributed Speed

Observation:

3

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1VAPo

“The ‘mean’ of the cubes is greater that the cube of the ‘mean’….”

Harvesting Wind EnergyPower in the wind ‐ Mean Speed/ E.P.F./ Power Density

Power in the Wind

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Φi, frequency distribution %.

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Power in the Wind: Mean Speed

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Power in the Wind: Distributed Speed

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Power in the Wind: Mean Speed

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E.P.F.

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Power Density

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Harvesting Wind EnergyPower in the wind ‐ Mean Speed/ E.P.F./ Power Density

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SWT-2.3-82 VS

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Harvesting Wind EnergyTurbine Performance – Power Curve

CUT-IN

CUT-OUT

Rated Power

[1] http://www.energy.siemens.com/hq/en/power-generation/renewables/wind-power/?stc=usccc021709[2] Current Design is on Rev. 4. Personal Communication Siemens, Energy Inc.

Wind Turbine SWT-2.3-82 VS [1]

RotorDiameter 82.4 mSwept area 5,300 m2Rotor speed 6–18 rpmPower regulation Pitch regulation

Sales Power Curve Rev.0 [2]Operational dataCut-in wind speed 3–5 m/sNominal power at 13–14 m/sCut-out wind speed 25 m/sMaximum 3 s gust:

55 m/s (standard version)70 m/s (IEC version)

SIEMENS

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*Enercon E-70 E4 Wind Turbine.Measured power curve…..according to IEC 61400-12 (1998) &

MEASNET (2000). Figure 14.14 (Erich Hau)

AVCP iPii 3

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AV

PC

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iPi

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Certified Power Curve*

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Harvesting Wind EnergyTurbine Performance – Overall efficiency

0.40

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‐MW

Power , Pi

CPi**

Wind Speed, m/s

Therefore CPi is:

**CPi = Power Coefficient as in:

Section 14.1, Hau Eric.

Section 14.1, Hau Eric.

If Pi is the net power output (effective, IEC 61400-12) then Cpi is the overall efficiency!


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Harvesting Wind EnergyTurbine Performance – Overall efficiency – Net

wind

netCPi

Energy flow through the mechanical-electrical energy conversion chain, nominal operating point.WKA-60 Wind Turbine.

Figure 14.2, (Erich Hau )

net power to the grid

3046

341176PiC

375.0PiC

Overall Efficiency:

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Harvesting Wind EnergyTurbine Performance – Energy YieldCalculation of the Annual Energy YieldCalculation of the annual energy yield of a wind turbine at a given site requires the power curve of the turbine and the frequency distribution of the wind speeds at hub height at the site.

Power curve of the wind turbineFigure 14.16. (Erich Hau)

Subdividing the frequency distribution of the wind speeds into wind speed intervals (method of bins)

Figure 14.15. (Erich Hau)

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Harvesting Wind EnergyTurbine Performance – Energy YieldCalculation of the Annual Energy YieldThe annual energy yield can be calculated as follows:

where the power output P is given in kW and the wind frequency distribution Φ in %.The annual energy yield is then obtained by summing all individual’ wind speed bin contributions.

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8760)(

Note: Adapted from Section 14.3, Hau, Eric. ( N.is the number of wind speed bins.)

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Harvesting Wind Power



The power is proportional to the wind speed in what power? Why?


What is the E.P.F. or wind Energy Pattern Factor?

What is the impact of the wind regime on site in the energy yielded by a wind power system?

Briefly describe the power curve of a typical large wind turbine

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- Nine: Control Systems:Hierarchy & Basic TasksAerodynamic Control – Power Control

– Power Limiter Blade Pitching, Passive Stall & Yaw Control


Hands-On Demonstration & Activity:How Blade Pitching works – Power Control, Rotor Speed, and Wind Velocity.

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Harvesting Wind EnergyControl Systems‐ The Basics…Power Plant Analogy…

Figure 10.6. Hau, Erich.Comparison of the control task in a thermal power station and in a wind turbine

Wind Turbine

Steam Power Station


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RIT Harvesting Wind EnergyControl Systems‐ Aerodynamic Power control…Why blade pitching… Enlarged Figure 5.12. Hau, Erich.

Power input of the WKA-60 rotor for variousfixed blade pitch angles and at a fixed rotor speed

LARGE WIND SPEED VARIATIONS REQUIRE SIGNIFICANT PITCH

ADJUSTMENT5°↔30°

Rotor Power, MW

Wind Speed, m/s

WindPower 5° 20° 30°

40°

10°

Blade Pitch Angle

Pitch Angle Variation before reaching rated power?

_________

Blade Pitch Angle Variation in the operating range?

__________

~ 0°

~ 25° ‐ 30°

Figure 14.10. Calculated Power Curve. Hau, Erich

Rated Power

Operating Range

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Relative Wind Velocity

Cruising Velocity THRUST

1. http://www.aerospaceweb.org/aircraft/jetliner/b787/b787_schem_01.jpg2. http://www.flightglobal.com/blogs/flightblogger/wingflex‐diagram‐thumb‐476x237.jpg

Boeing 7871

Boeing 747 Wing2

VPlane = - VCruising

OBSERVERV = VPLANE

VrWind = VCruising

Harvesting Wind EnergyControl Systems‐ Aerodynamic Power control…Why blade pitching…ABSOLUTE VS. RELATIVE VELOCITY.

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THRUST

VPlane = - VCruising

Harvesting Wind EnergyControl Systems‐ Aerodynamic Power control…Why blade pitching…ABSOLUTE VS. RELATIVE VELOCITY.

OBSERVERV = VBLADE

OBSERVERV = VPLANE

Wind Speed

Rotation

Relative Wind Velocity

Cruising Velocity

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Direction of rotation

operationalposition

featheredposition

featheredposition(stall)

2/27/2016 40Figure 5.13. Hau, Erich.Controlling the rotor input power by pitching the blade towards feather or towards stall…

operationalposition

Harvesting Wind…Control Systems‐ Power Control

Blade PitchingFigure 5.39. Hau, Erich.Influence of airfoil L/D ratio and blade # on CPRWind Speed

Too large angle of attack…high drag / no lift (separation)

Too small angle of attack…low drag…but too little lift….

AIRFOIL TESTVIDEOLINK

ReduceAOA Increase

AOA

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Harvesting Wind EnergyControl Systems‐ Aerodynamic Power control…Why blade pitching…How it is done…Hydraulic drive…

Figure 8.16. Hau, Erich.Blade pitch system of the WKA‐60 with hydraulic driveand direct‐acting actuators in the rotor hub

Figure 8.15. Hau, Erich.Single‐row four‐point ball‐bearing in the rotor blades

of the earlier WKA‐60

HYDRAULIC PITCH CONTROLSource:Drive & Control Technology for Wind Turbines,Bosch Rexroth AG,www.boschrexroth.com/windenergy

OLD DESIGN

CURRENT DESIGN

OUT OF BLADE/HUBSUPPLY SYSTEM

RIT Harvesting Wind EnergyControl Systems‐ Aerodynamic Power control…Why blade pitching…How it is done…Electric drive…

Figure 8.19. Hau, Erich.Individual electric pitch systems for each rotor blade in the Enercon E‐40

Figure 8.20. Electrical blade pitch system of the Dutch Lagerwey LW‐72 inside the rotor hub

IN BLADE/HUBSYSTEM


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Harvesting Wind EnergyControl Systems‐ Aerodynamic Power control…Yaw control…a dual purpose…load control…

Figure 5.26. Hau, Erich. Decrease in the powerCoefficient of the rotor with increasing yaw angle

HYDRAULIC YAW CONTROL SYSTEMSource: Drive & Control Technology for Wind Turbines,Bosch Rexroth AG, www.boschrexroth.com/windenergy

Maximum Power Coefficient Difference?

(0° versus 60° yaw angles) ______

What is the expected power difference of the 60°

yaw angle relative to the 0° yaw angle? ______

∆ ≤ ‐0.34 (‐75%)

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Figure 10.5. Hau, Erich.Measured azimuth angle of the nacelle and wind

direction during operation of the WKA‐60

Harvesting Wind…Control SystemsAerodynamic Power control…Yaw control…as dual purpose…wind tracking…

Figure 8.56. Hau, Erich.Yaw system with assembly, WTG‐0600, 1985

Figure 10.4. Hau, Erich.Operating diagram of the WKA‐60 yaw system

LARGE YAW ANGLES, α

SMALL YAW ANGLES, α

α

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Harvesting Wind Energy - How Blade Pitching works

HANDS-ON DEMONSTRATION


Objective:Demonstrate the operation of a wind turbine and get insight into wind power load control by blade pitchingevaluating the performance of a three-bladed mini-wind turbine with the blades set at various angles of attack.

Summary:We will operate the mini wind turbine at each fan speed: high, medium and low with the three-bladed rotorhaving the blades set at two different blade pitch angles, ex. 10° and 30°.

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Large wind turbines typically have adjustable blades to allow variation of the blade pitch angle.At any given operating condition, what is the effect on power and rotor speed of increasing the pitch angle?


In the context of a wind turbine rotating blade, define the term ‘relative wind velocity’.

Can the wind turbine yaw angle be used as power and speed control? Explain.

From an aerodynamic perspective, why does blade pitching work and use?

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Fundamental ConceptsReview & EvaluationTypical Answers

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Energy in the Wind

What is the mathematical function that best describes the wind resource, and how the mean wind speed is calculated?


Did you learn something new? If so, What was it?

What is the origin of the wind? Name three of the main causes.

Energy in the Wind

On a GLOBAL scale what are the zones with best wind resources?

On a NATIONAL scale what are the zones with best wind resources?

The Weibull distribution. For a given wind distribution ΦI , the mean wind speed is given by:

On a global scale, solar energy in the form of uneven heating and the Coriolis effect.

There are also local effects associated with topography and surface characteristics.

Offshore, near the coast, islands, etc.

East and west coast, and the Midwest states. The Great Lakes are good areas too!

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Energy in the Wind

Describe the operating principle of one wind speed measurement device/method.



Which are the best sites for wind farms?

Energy in the Wind

What would define a flat terrain in contrast to a hilly terrain?

In an urban setting, how far/above obstacles/buildings should a wind turbine be installed?

The cup anemometer is a drag device….

The ultrasonic anemometer works by measuring the changes in the speed of sound caused by the passing wind…

Offshore, lake shores, on hills (on top)

Hills in front or behind the turbine are shorter that 1/3 of the height of the wind turbine measured up to rotor diameter ( tip of the rotor blades ).

The turbine rotor must be above the obstacle by 3 times the height of the obstacle (from the tip of the blades);

and as far as 20 times that distance.

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The power is proportional to the wind speed in what power? Why?


What is the E.P.F. or wind Energy Pattern Factor?

What is the impact of the wind regime on site in the energy yielded by a wind power system?

Briefly describe the power curve of a typical large wind turbine

The mean wind speed has the larger effect of energy yielded in a particular site. The larger the mean speed the larger the energy yielded. Nevertheless, the wind distribution has also an effect on the energy yielded although such effect is most typical places where the wind distribution resembles the Rayleigh function (Weibull distribution with k=2).

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The power is proportional to the cube power of the wind speed…

Because wind ids the product of the kinetic energy in the wind (square power) of the speed and the wind flow (or speed)…

The ratio of wind power calculated with the wind distribution and power calculated with the mean wind speed.

It has a cut-in speed (the wind speed that the turbine start to rotate); it increases exponentially until it reaches the rated power where stays flat until it reaches the cut-out speed (the wind speed that the turbine is shut down to avoid damage). The turbine cannot operate above the cut-out speed..

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Large wind turbines typically have adjustable blades to allow variation of the blade pitch angle. At any given operating condition, what is the effect on power and rotor speed of increasing the pitch angle?




From an aerodynamic perspective, why does blade pitching work and is used?

Yes, facing the rotor away from the wind direction reduces both the rotor effective swept area and the normal wind velocity.

The ‘relative wind velocity’ is the wind velocity measured by an observer traveling with the blade of a spinning wind turbine.

The ‘relative wind velocity’ is equivalent to the addition of the actual wind velocity and the rotor blade velocity.

At any given operating condition, increasing the pitch angle leads to stalling the turbine blades.

When the turbines blades stall both power and speed reduce.

Blade pitching induces aerodynamic stall and the lift generated by each blade is significantly reduced.

The wind velocity cannot be controlled. Blade pitching is the only practical way to reduce the amount of energy converted.

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Large wind turbines typically have adjustable blades to allow variation of the blade pitch angle.At any given operating condition, what is the effect on power and rotor speed of increasing the pitch angle?




From an aerodynamic perspective, why does blade pitching work and use?

energy in the wind - · pdf file123456 78910 wind distribution frequency(%)

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