1

Wind Energy Resource and Technologies

Dr. Ram ChandraAssistant Professor

Centre for Rural Development and Technology

Indian Institute of Technology Delhi

Hauz Khas, New Delhi – 110 016

2

Renewable Energy Scenario (18.8% share)

Wind– 32.8 GW (58.8%)Small hydro– 4.2 GW (7.2%)Solar PV– 17.0 GW (22.3%)Biomass– 8.4 GW (13.7%)Waste to energy – 0.10 (0.2%)

62.8

0 G

W

Wind EnergyWind possesses energy by virtue of its motion. Windspeed increases with height. The measurement ofwind speed is done at a standard height of 10 m.

The wind speed at surface is nearly 20–25 % lowerthan that at standard height. At a height of 60 m windspeed may be 30 – 60 % higher due to reduction in thedrag effect of the earth’s surface.

4

Three factors determine the power output from awind energy converter:

1) Wind speed

2) Cross sectional area of wind swept rotor

3) Overall conversion efficiency of the rotor,transmission system and generator or pump

Horizontal Axis Wind Turbine

7

Verticle Axis Wind Turbine

The Energy Extracting Stream‐tube of a Wind Turbine

Continued…The power in wind can be computed by using the concept ofkinetics. Wind mill works on the principles of converting kineticenergy of the wind into mechanical energy.

Power = Work done/time (J/sec = Watt)

Kinetic Energy = ½ (mV2) ……………1

The amount of air passing in unit time, through an area, A with avelocity

= AV

Then, m = ρAV ………………………….2

(ρair = 1.225 kg/m3)

Continued…Thus, K. E. = ½ (ρAV3) …………………………….3

Then, Power Available in wind,

Pa = ½ [ρ(π/4)D2V3)………………………………...4

Pa = 1/8[ρπD2V3]………………………………........4a

The fraction of the free flow wind power that can be extracted bythe rotor is called POWER COEFFICIENT.

Power Coefficient = [Power of Wind Rotor/Power Available in theWind)

Continued…The maximum theoretical coefficient is equal to16/27 or 0.593. For the best practical rotor, thepower coefficient is about 0.4 – 0.45.

The factor 0.593 is known as the BITZ LIMIT (afterthe name of the engineer who first derived thisrelationship)

WIND FARM

GRID Line feeder

33KV/690V

Wind generator

132KV/33KV

WIND DATASurface wind data on a national or regional basis isusually presented in the form of:

1: Isovents: are contours of average wind velocity(m/s or km/h). The average period varies widely butmonthly, quarterly, and yearly averages arecommon.

2: Isodynes: are contours of constant wind power(W/m2 of area perpendicular to the wind flow).

Wind Survey: Typical wind measurements at potential sites forwind machines usually requires the following:

(1)Instrumentation: 3 cup anemometer and wind directionsensors, height of instruments, 10 m for preliminary data, 15 –45 m for long time data.

(2) Data Recording System: Strip chart, magnetic tape.

(3) Type of Data: Wind speed and hourly direction.

(4) Data Reporting: Wind frequency curves‐‐‐‐‐‐ daily, weekly,monthly, energy estimation – are basic wind data.

Annual hours or duration of various wind speed associated withdesign of wind mill.

1.Cut in speed: The speed below which the wind mill does notwork.

2. Design Speed: The speed for which rotor is designed.

3. Furling Speed: The speed at which the rotor is turned awayfrom facing the wind or stopped otherwise, with a view toprotect the wind mill.

4. Rated Velocity: At which the plant output is maximum.

The area of the wind streamsswept by the wind turbine ismaximum, when blade face intothe wind. This is achieved bycontrol arrangement, in whichwhen the wind directionchanges, a motor rotates theturbine slowly about the vertical(or yaw) axis so as to face theblades into the wind.

YAW CONTROL

• Cut‐in speed (Vin)• Rated speed (Vfull)• Cut‐out speed (Vout)

Advantages of Wind Power

18

1. The wind is free and with modern technology it can be captured efficiently.2. Once the wind turbine is built the energy it produces does not cause green house gases or other pollutants.3. Although wind turbines can be very tall each takes up only a small plot of land. This means that the land below can still be used. This is especially the case in agricultural areas as farming can still continue.4.Many people find wind farms an interesting feature of the landscape.5. Remote areas that are not connected to the electricity power grid can use wind turbines to produce their own supply.6.Wind turbines have a role to play in both the developed and third world.7.Wind turbines are available in a range of sizes which means a vast range of people and businesses can use them. Single households to small towns and villages can make good use of range of wind turbines available today.

Disadvantages of Wind Power

19

1. The strength of the wind is not constant and it varies from zero to storm force. This means that wind turbines do not produce the same amount of electricity all the time. There will be times when they produce no electricity at all.2.Many people feel that the countryside should be left untouched, without these large structures being built. The landscape should left in its natural form for everyone to enjoy.3.Wind turbines are noisy. Each one can generate the same level of noise as a family car travelling at 70 mph.4.Many people see large wind turbines as unsightly structures and not pleasant or interesting to look at. They disfigure the countryside and are generally ugly.5.When wind turbines are being manufactured some pollution is produced. Therefore wind power does produce some pollution.

Thank You