Wind Energy B.Tech Electrical and Mechanical Engineering

contains concepts of wind energy system for engineering department Electrical and Mechanical

1. Varun Kumar
EEED, NCE, Chandi

2. Recent developments
In 2006, total installed capacity 73904 MW
Mostly two-three blades propeller types turbines
In India, wind installation of 7000 MW
Size of machines 1.2-1.6 MW
Locations, TN,MH,GJ,KA and RJ
Average installation cost 50000Rs/kW (2007) and
pay back period 4-5 years (Solar PV cost ???)
Standalone 0.5-50 kW and wind-diesel hybrid
system

3. Types of wind turbines
Multi-blade type (horizontal axis)
Savonious type (vertical axis)
Propeller type (horizontal) widely used
Darrieus type (vertical type)
Darrieus
Wind turbine
At Qubeque

4. Propeller type rotor
5 MW turbine
in Belgium offshore
Wind machine in India
• Rated capacity 2.1 MW
• Cut-in wind speed 3-4 m/s
• Cut-out speed 25 m/s
• Number of blades 3
• Rotor diameter 88 m
• Hub height 80 m
• Power control active blade pitching
• Generator type asynchronous

5. Rotor assembly-1

6. Rotor assembly-2
Gear box, rotor shaft and brake assembly

7. Hub size

8. Blades passing through Eden field UK

9. Wind data
Wind velocity- measured with an anemometer
At any location, wind speed very irregular in
period and amplitude
Typical variation of wind speed with time

10. Speed-frequency distribution plot
No. of hours in a month/year in which the wind
speed is in a certain range.
In table form, mean % frequency distribution of
hourly wind speed in 2 kmph intervals.
As an e.g. for Kandla, 0.012 x 744 = 8.9 h zero
speed in January and 0.032 x 8760 = 280.3 h zero
speed in whole year.
 As an e.g. for Indore, 0.087 x 744 = 64.7 h 18-20
kmph speed in January and 0.081 x 8760 = 709.6
h 18-20 kmph speed in whole year.

11. Maximum wind speed distribution 18-20 kmph
for 710 h in a year
280 h calm period (point A on the plot)
Speed-frequency distribution plot
for Kandla

12. Speed-duration plot for Kandla
Specified wind-speed against no. of hours in a month or a year
Speed-frequency distribution or speed-duration plots are
important for assessing suitability of a location for installing
wind machines.

13. Energy from wind for a location
Wind power density is the K.E. flowing per unit
area,
Wind power density integrated over a time
period gives an energy density,
Annual wind energy density,

14. Wind speed with height from
ground
Energy content varies with wind-speed at height
as per power law,
Wind speed at another height is given by,
α is in the range 0.1 to 0.4, 0.1 for flat land, 0.1-0.2
for land with grass-crops, 0.25 to 0.4 for very
rough urban

15. Example on wind energy in Indore
Calculate the energy content of the wind per
square meter at Indore in May at height level of
10.9 m. the air density ρ may be taken as 1.20
kg/m
3
. (J K Nayak, pg. 343)
% frequency distribution of hourly wind-speed
for May at Indore,
Interval
(kmph)
00 00-02 02-04 04-06 06-08 08-10 10-12 12-14 14-16 16-18
% Freq. 3.2 1.6 0.9 1.3 2.0 1.3 3.9 4.0 6.3 6.2
18-20 20-2222-24 24-26 26-28 28-30 30-32 32-34 34-36 36-38 38-40
6.5 10.3 7.4 8.0 4.3 5.1 7.5 4.5 5.7 4.1 1.7
40-42 42-4444-46 46-48
2.2 0.8 0.7 0.1

16. Example continued…..
Energy content (E
m/A) = 0.5 x 1.20 x (744/100) (1.6
x 1
3
+ 0.9 x 3
3
+ 1.3 x 5
3
+ 2.0 x 7
3
+ 1.3 x 9
3
+ 3.9 x
11
3
+ 4.0 x 13
3
+ 6.3 x 15
3
+ 6.2 x 17
3
+ 6.5 x 19
3
+
10.3 x 21
3
+ 7.4 x 23
3
+ 8.0 x 25
3
+ 4.3 x 27
3
+ 5.1 x
29
3
+ 7.5 x 31
3
+ 4.5 x 33
3
+ 5.7 x 35
3
+ 4.1 x 37
3
+ 1.7
x 39
3
+ 2.2 x 41
3
+ 0.8 x 43
3
+ 0.7 x 45
3
+ 0.1 x 47
3
)
= 8298622 [kg/m x h x km
3
/h
3
]
To convert in kWh/m
2
, divided by 3.6
3
x 1000,
thus, it is 177.9 kWh/m
2

17. Power-density duration curve
Wind-speed duration curve (V-hours), if modified
to (V
3
-hours) with proper constant, then curve is
known as power-density duration curve as (P/A α
V
3
).
• Cut-in speed – wind speed below which machine
produces no power (point A)
• Designed speed – wind speed at which machine
develops rated output power, and machine develops
rated output even at speed above design speed
(point B)
• Cut-out speed – wind speed at which machine is
advisable to shut down in order to avoid mechanical
damages (point C)

Actual power available (hatched area)
less than the total power.

18. Example on wind energy in
Indore with cut-in, cut-out speed
Calculate the wind machine available energy with cut-in
speed 14 kmph, designed speed 36 kmph and cut-out
speed 90 kmph. (J K Nayak, pg.344)
(E
m/A) = 0.5 x 1.20 x (744/100) (6.3 x 15
3
+ 6.2 x 17
3
+ 6.5 x
19
3
+ 10.3 x 21
3
+ 7.4 x 23
3
+ 8.0 x 25
3
+ 4.3 x 27
3
+ 5.1 x 29
3
+
7.5 x 31
3
+ 4.5 x 33
3
+ 5.7 x 35
3
+ (4.1 + 1.7 + 2.2 + 0.8

+ 0.7+
0.1) x 36
3
)
= 7606803[kg/m x h x km
3
/h
3
] = 163.0 kWh/m
2
Location with annual energy contents in excess of 1000
kWh/m
2
is suitable for the wind machine installation.
In India, east-west coasts and Deccan plateau has potential of
15000 MW from wind energy.

19. Aerodynamics of wind-rotor
In wind rotor, air moves faster on the front
curved side of the blade, making lower pressure
on that side than the flat side of the blade.
With higher pressure on flat side of the blade,
the lift is created and the blade is pulled towards
the area of low pressure.

20. Performance parameters for
Wind turbine
Power co-efficient: ratio of power extracted by the
rotor to the power available in the wind stream
Lift co-efficient: ratio of the lift force on the blade to
the force of the free stream wind
Drag co-efficient: ratio of the drag force on the
blade to the force of the free stream wind
3
2
1
/

 AVPC
eP

2
2
1
/

 VAFC
bLL

2
2
1
/

 VAFC
bDD


21. continued….
Tip speed ratio: ratio of the speed of the blade tip to the
free stream wind speed
Where = angular velocity of the rotor and = tip
radius of blade
Variation of power co-efficient with tip speed ratio is
given by an empirical relation,
Upper limit, Betz limit, (16/27) = 0.593
The same relation for propeller or multi-blade type
rotor considering drag into account
 &
For propeller rotor


V
R

 R
 
2946.1
3538.0exp
27
16







 
p
C
 ]3538.0[exp
27
16
2946.1
 







p
C LDCC/
02.0008.0

22. Power co-efficient Vs tip-speed
ratio for different wind rotors
• In all cases, power co-efficient
has a maximum for a particular
tip-speed ratio.
• Except propeller type, rise and
fall of the power co-efficient around
the maximum value is quite rapid.
• Highest C
p is for propeller type.
• Multi-blade and Savonius have low
Value of λ, while propeller and
Darrieus have high λ in the range
2-4.

23. Example-power from propeller
type wind rotor
Rotor dia. = 60 m, location with wind speed = 35
kmph, wind machine speed = 20 RPM, find power
output from the machine when effects of drag
are not considered and when the effects of drag
are considered. Assume ε =0.012 (J K Nayak, pg.
348)
ω = 2π*20/60 = 2.094 rad/sec
Tip-speed ratio λ = (2.094*30)/(35*1000/3600) =
6.463
Power without drag into consideration,
 5742.0463.63538.0exp
27
16
2946.1








p
C
MWP
e
895.0
3600
100035
302.1
2
1
5742.0
3
2






 

24. Continued…..
Power with drag into consideration,
  5282.0]463.6012.0463.63538.0[exp
27
16
2946.1








p
C
MWP
e 823.0
3600
100035
302.1
2
1
5282.0
3
2






 

25. Example on output from wind
machine with diff wind speeds
Three blade propeller wind machine runs at 20
RPM. Cut-in, designed and cut-out speeds are 14,
36 and 90 kmph, respectively. Wind machine eff.
0.93 and generator eff. 0.97. Tower height 60 m
and rotor dia. 62 m. ε=0.011 and air density ρ =
1.2 kg/m
3
. Plot electrical out put with diff. wind
speeds. (J K Nayak, pg. 350)
Angular velocity of rotor = 20 rpm = 2.094 r/sec
For cut-in speed, tip-speed ratio λ =
(2.094*31)/(14*1000/3600) = 16.7

26. Continued…
  478.0]7.16011.07.163538.0[exp
27
16
2946.1








pC
WP
e
50925
3600
100014
312.1
2
1
478.0
3
2






 
Thus, power at diff. wind-speeds is calculated and plotted.
V
(kmph)
18 24 30 36
λ 13.0 9.7 7.8 6.5
C
p
0.5 0.518 o.527 0.532
P
e
(kW) 102.1 250.8 498.4 869.3