Basics of Wind Technology

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Basics of Wind Energy Technology

Animesh Dutta

Energy, Asian Institute of Technology

July 06, 2006


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2Driving to the future

Efficiency

Emission EconomicsDriving Forces

Dete

rmine


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Mass-produced widely distributed PV arrays and wind turbines mayeventually generate 10-30 TW emission-free


4/49Basics of Wind Energy Technology

4Ancient Resource Meets 21st CenturyTechnology

The power of the wind has been used throughout human history, topower sailboats, to mill grain, and to pump water. Inventors first usedwind power to create electricity late in the nineteenth century. Todayswind turbines are sophisticated machines that use state-of-the-art

technology to convert raw power from the wind into electricity that canbe contribute to the countrys power needs.



5OBJECTIVE OF THIS PRESENTATION

This presentation discusses the following:

(a) Fundamentals of Wind Power

(b) Type of Turbines

(c) Wind Energy Applications

(d) Economics

(e) Advantages and disadvantages



6

Fundamentals of Wind PowerFundamentals of Wind Power Wind is stochastic in nature

Speed and direction of wind ata location vary randomly withtime

Apart from the seasonal anddaily variations, the wind

pattern may change from yearto year-even to the extent of10 to 30 per cent

Hence, the behavior of thewind at a prospective siteshould be properly analyzed.



7Global Wind

At equator, a low pressure beltis created because of strongsolar radiation. At the surface,this region is called doldrums.

At the tropopause, the air coolsuntil it reaches latitudes ofabout 30degrees where it sinksback to the surface, creating a

high pressure belt.

Some are forced back towardslow pressure zone (trade

winds). The rest movestowards pole until it reaches 60degree latitudes and forms asimilar kinds of loop both with

the poles and with the 30degree latitudes.


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Global wind

Also when earth is rotating, the winds are subjected to a phenomenon

known as the Coriolis Effect.

Force due to

pressure gradientResulting path

Coriolis force

High pressure region

Low pressure region

The earth receives around 1.71014 kW of power

from the sun in the form of solar radiation


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9Fundamental of wind power

The wind, for example the shoreline breeze, is theresult of uneven heating of the earth by the sun.


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10Fundamental of wind power

Similarly, mountain-valley winds are also created.


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11Wind speed Classification of the Beaufort WindScale


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12FUNDAMENTALS OF WIND POWER

Single obstacles are no problem if the totalrotor area is over three times higher than theobstacle or if there is sufficient distance(could be up to 35 times the height) available.

The wind speed is increases with the heightfrom the ground because of the roughness ofthe ground.

The wind speed v(h2) at height Z0 can be

calculated directly using the followingequation

0

2

4

6

8

10

12

0 20 40 60 80

Distance from the ground, m

Windvelocity,m/s

=1

0

2

12

ln

ln

).()(dh

z

dh

hvhv

0z

Here, Z0 is the height at which the wind is slowed to zero and d is theparameter for displacement boundary layer for obstacles


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13Effect of Z0 and d on the wind speed at h2=10 m[v(h1)=10 m/s at h1=50 m]


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14Energy and power in the wind

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2 E m V =

31

2P A V=

V

V

Power available fromwind energy

The power in the wind is proportional to:

The density of air. It is lower at highermountainous regions; but avg. density in coldclimates may be up to 10% higher than intropical regions.

The area through which the wind is passing;and

The cube of wind velocity. Power increase a

factor of 8 if wind velocity increases to doubleof its original.


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15Power Coefficient and utilization efficiency

The power coefficient of the rotor can be defined as the ratio of actual

power developed by the rotor to the theoretical power available in the wind.

For utilization of wind power, wind turbineshould take as much power from the windas possible. The turbine slows the speedfrom v1 to v2 and uses the correspondingpower differences.

( )22212

1vvmPT = &

( )2121 vvAm +=

&3

102

1 vAP =

Turbine power

Wind power

0P

PC Tp =

Maximum Cp is about 0.6 when the ideal speed ratio (v2/v1=1/3)

However, for a good system Cp lies between 0.4~0.5

Power utilization efficiency is defined as PTactual/PTideal = Cp/Cpmax


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17Airfoil Lift and dragAirfoil Lift and drag

Flow

L

D

F

21

2L L C A V =

21

2D D C A V =


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18

TYPE OF TURBINES


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19TYPE OF TURBINES

Lift machines and Drag machinesLift machines and Drag machines


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20Examples of wind energy conversion

Examples of wind energy conversion


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21Examples of wind energy conversion


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22Wind Turbine Classification

Horizontal axis

Single-bladed

Head-on Double-bladedTriple-bladed

Multi-bladed

Darrieus

Vertical axis Savonius

H rotor


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SavoniusSavonius rotorrotorUse drag principle. It has two semi-cylindrical blades open on oppositesides. Near the axis blades overlapto redirect wind from one blade tothe other

It also utilizes lift to have a betterefficiency than simple drag devices

However, efficiency is much worse than that of good lift devices (max Cp

=0.25)

Star at very low speed and used for ventilation purpose, but requires highermaterial

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24Vertical Axis:Vertical Axis: DarrieusDarrieus

Consists of two or three rotor bladesthat have the shape of parabola.

The profile of the rotor blades

designed such a way that it uses liftprinciple. Because of vertical axisangle of attack changes continuously.

Efficiency is much higher compared toSavonius rotor however only 75% ofmodern rotor with horizontal axis.

It cannot start on its own; always

needs an auxiliary starting system.

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25H rotor

H rotor is the further development ofDarrieus rotor and uses the concept oflift device.

A permanent-magnet generator isdirectly integrated into the rotorstructure and needs no gearbox.

The three rotor blades are attachedvertically.

Supports to vertical axis helps rotormaintain its shape.

Used for extreme weather conditionssuch as in the high mountains or inAntartica.

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26Wind turbines with horizontal rotor axis

A horizontal axis wind turbine generally consists of the followingcomponents

Rotor blades, rotor hub, rotor brake and a pitch mechanism if needed

Electrical generator and a gearbox if needed

Wind measurement system and yaw drive (azimuth tracking)

Nacelle, tower and foundation

Control substation and main connection

Number of rotor blades: Can have one, two or three rotor blades, Lower the number of blades

less the material is.

Single-bladed rotor must have a counter weight.

Three-bladed rotors have optically smoother operation and henceintegrated better with the landscape.

Higher optimal power coefficient above two-bladed rotorscompensate the disadvantages of higher material demand.

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27Classification of wind turbines by number ofblades

Tip speed ratio: 7-8 Tip speed ratio: 10 Tip speed ratio: 15

Wind speed ranges:

Cut-in speed = 2.5-4.5 m/s; design wind speed = 6-10 m/s;nominal wind speed = 10-16 m/s; cut-out wind speed = 20-30 m/s;

and survival wind speed = 50-70 m/s

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TYPE OF TURBINES


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28TYPE OF TURBINES

Upwind and Downwind machinesUpwind and Downwind machines

Upwind Downwind

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29Wind Turbine Layout

Hinged-rotor blades

2-bladeddownwind

FMRS

Off-the-shelf

generator

30Wi d I d G h T d


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30Wind Industry Growth Trends

0.15 MW

10 m,

26 ft

Altamont

Region

Larger multi-MW turbines Demand for new innovative technologies

Led by Europeans

Offshore & low wind regime focus in U.S.

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WIND ENERGY APPLICATIONS


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Wind Energy Applications

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Si d A li tiSi d A li ti


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Sizes and ApplicationsSizes and Applications

Small (10 kW) Homes

Farms Remote Application

Intermediate

(10-250 kW) Village Power

Hybrid Systems

Distributed Power

Large (660 kW - 2+MW)

Central Station Wind Farms

Distributed Power

Community Wind

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Out o f t he Shadow :Out o f t he Shadow :The Br ight Fut ure for Sm al l Wind Syst em s

34Modern Small Wind Turbines:Modern Small Wind Turbines:


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Modern Small Wind Turbines:Modern Small Wind Turbines:High Tech, High Reliability, Low Maintenance

Products from 400 WProducts from 400 W 5050

kWkW Technically AdvancedTechnically Advanced

Only 2Only 2--3 Moving Parts3 Moving Parts

Very Low MaintenanceVery Low MaintenanceRequirements

10 kW

50 kW

400 W

900 W

Requirements

(Not to scale)

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Small Turbines Require Less WindSmall Turbines Require Less Wind

Large Turbines Require ~ Class

3-4 Wind Regime

Prefer Class 5

Small Turbines Require ~ Class

2 Wind Regime

Class 1

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Clean Distributed GenerationClean Distributed Generation

Renewables for Homes, Farms, and Businesses

Photovoltaics Solar Thermal Small Wind

Installed Cost $ 9 / Watt $ 10 / Watt $ 4 / WattStatus Commercial Demo Commercial

Payback Period 30 Years 30+ Years 15 Years

Cost Potential $ 3 in 2010 ? $ 1.50 in 2010

Typical Site Suburban Southwest Rural

Available Resources Poor - Good Poor - Good Poor - Great

StatusStatus

of theof theTechnologiesTechnologies

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Rural Residential WindRural Residential Wind

10 kW (6 m Rotor Diameter)

Rural Site, 1 Acre or More Connected to House Wiring

Produces ~ 13,000 kWh perYear

Offsets ~ 7 Tons of CO2 perYear

Excess Power Sold to Utility

Cost: ~ $32,000 - $40,000

10 kW Wind Turbine

24 m (80 ft)GuyedTower

SafetySwitch

PowerProcessing

Unit (Inverter)

CummulativeProduction

Meter

AC LoadCenter

TYPICAL HOME SYSTEMTYPICAL HOME SYSTEM

38Micro Wind TurbinesMicro Wind Turbines


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Micro Wind TurbinesMicro Wind Turbines

Below 400 W for Battery Charging, Tourism Industry

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Small Wind TurbinesSmall Wind Turbines


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0.4 to 100 kW

Off-grid applications

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Large Wind TurbinesLarge Wind Turbines


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100 kW and above

Provide bulk power, grid or off grid

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Economics of Wind Energy


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Wind Energy Cost Competitiveness

Source: BTM Consult

44.24.3 5.2

8.2 8.7

12.8

02

6810

1214

Gas

Wind

Energy

Coal

Hydro

Geoth

ermal

Nucle

ar

/kWh

42Renewable Energy Cost Trends


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Levelized cents/kWh in constant $20001

PV

1980 1990 2000 2010 2020

100

80

60

40

20

0

Wind

1980 1990 2000 2010 2020

COEcents/kWh

40

30

20

10

0

BiomassGeothermal Solar thermal

1980 1990 2000 2010 2020 1980 1990 2000 2010 2020 1980 1990 2000 2010 2020

COEcents/kWh

10

8

6

4

2

0

70

6050

40

30

20

10

0

15

12

9

6

3

0

Source: NREL Energy Analysis Office (www.nrel.gov/analysis/docs/cost_curves_2002.ppt)1These graphs are reflections of historical cost trends NOT precise annual historical data.Updated: October 2002

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Construction Cost Elements


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Construction Cost Elements

Turbines,

49%

Construction

22%

Towers(tubular s teel)

10%

Interest During

Construction

4%

Interconnect/

Subsation

4%

Land

Transportation2%

DevelopmentActivity

4%

Design &

Engineering

2%

Financing &

Legal Fees

3%

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Cost of Wind Energy

Source:American Wind Energy Association

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M E i b t Al MMore Ex pensive but Also More


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More Ex pensive, but A lso MoreMore Ex pensive, but A lso More

ValuableValuable

Large Turbines ~ $1,000 / kW

High Voltage Delivery Value of Power:

2-5Small Turbines ~ $2 3,000 / kW Low Voltage Delivery

Value of Power:

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46Advantages of Wind Power


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Environmental No air pollution

No greenhouse gasses

Does not pollute water with mercury No water needed for operations

Resource Diversity & Conservation

Domestic energy source

Inexhaustible supply Small, dispersed design reduces supply risk

Cost Stability

Economic Development Expanding Wind Power development brings jobs to rural communities

Increased tax revenue

Purchase of goods & services

47Noise pattern of a Typical Wind Turbine


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48Wind Turbines:Power for a House or City


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Power for a House or City

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Thank You for Your

Attention

Basics of Wind Technology

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