1. MAXIMUM POWER GENERATION USING WIND POWER PLANTS
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MAXIMUM POWER GENERATION USING WIND POWER PLANTS
Prepared by: Nur Bekiroglu
Zehra Yumurtacı
Bedri Kekezoğlu
IGEC-198

2. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Today, due to increasing population and industrialization, in developing countries, energy demand can not be met with existing limited sources; therefore the great difference between energy production and consumption becomes even larger.
In that situation, it becomes very important for the country to utilize its own resources with higher efficiency.
On the other hand, when the disadvantages of conventional energy production methods are taken into consideration, the importance of renewable energy sources is significant.
Among the renewable energy sources, wind has a significant importance as it is clean, environment-friendly, and continuous and has relatively lower costs.
IGEC-198

3. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
A lot of regions in the world have wind powered electricity generation potential.
It is considered that the wind energy potential of the area in between the 50° North and South latitudes is TWh/year and due to economical and other reasons, 9000 TWh/year capacities is utilizable.
According to the studies conducted, it is concluded that 27% of the terrestrial area of the earth encounters 5,1 m/s of annual average wind speed.
It is calculated that if this potential is employed, 8 MW/km2 production capacities and a GW installed power will be achieved.
IGEC-198

4. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Fig.1. Increase of the installed power values of the wind power plants in the world. (American Wind Energy Association and European Wind Energy Association)
IGEC-198

5. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Figure 1 shows the increase of the installed power values of the wind power plants in the world and Table 1 shows distribution of installed power over the countries.
It also shows that world’s wind power potential is high and there are countries that use almost all their potential, as well as there are countries that can not use their potential.
Figure 2 shows the distribution of the installed power over the continents. Table 2 shows the distribution of technical potential in European countries
IGEC-198

6. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Fig.2. Distribution of the installed power over the continents (European Wind Energy Association
IGEC-198

7. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Table 1. Shares of installed wind power in the world.
(World Wind Energy Association)
Total Capacity MW %
Germany
18,428
31,0
Spain
10,027
16,9
USA
9,149
15,4
India
4,430
7,5
Denmark
3,122
5,3
Italy
1,717
2,9
U.K.
1,353
2,3
China
1,260
2,1
Japan
1,231
N.L.
1,219
Total(Top 10)
51,936
87,5
Rest of the world
7,368
12,5
World total
59,322
100
IGEC-198

8. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Table 2.Technical potential for wind power in Europe countries. (
Technical potential
Total area
1000 km2
Region potential
Power
(GW)
Energy
(TWh/year)
Denmark 43
1720 14 29
Germany
357
1400 12 24
U.K.
244
6840 57
114
Italy
301
4160 35 69
N.L. 41
400 3 7
Spain
505
5160 86
Turkey
781
9960 83
166
IGEC-198

9. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
In order to compete within the electricity market, wind power plants must be able to produce electricity with costs that can be compared to fossil fuel production method costs.
Since wind has no cost itself, all the investment costs in such systems consist of the mechanical and electrical parts.
Parallel to technological development in the area, turbine costs have decreased and produced total energy has increased.
Table 3 shows the estimated variations of costs for years.
IGEC-198

10. INTRODUCTION YILDIZ TECHNICAL UNIVERSITY IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Table 3. Wind power technology, past, present and future
(American Wind Energy Association)
Technological position
1980
1990
After 2000
Unit energy cost($/kWh)
0.35 $-0.4 $
0.05 $-0.07 $
<0.04 $
Unit plant cost ($/kW)
2000 $-3000 $
500 $-800 $
<500 $
Plant lifetime
5-7 year
20 year
30 year
Load factor
50 %-65 %
95 %
>95 %
Power range kW kW kW
IGEC-198

11. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
All the factors that affect wind power turbine design, construction and operation, are in balance with cost component.
All the studies consulted nowadays are in order to decrease the wind power costs to 0,024$ levels by the year 2010.
Therefore wind power will be competitive with conventional energy sources. The unit cost of the energy produced by the wind power plants vary according to the wind speed.
It is known that as the wind speed increases, the unit cost of the energy produced decreases. As the applications in the USA are analyzed, the change of unit energy cost with wind speed is as in Fig.3.
In EU countries, these values are calculated as 9,6 cent/kWh for 5 m/s wind speed and 3,4 cent/kWh for 10 m/s (European Wind Energy Association ).
IGEC-198

12. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
INTRODUCTION
Fig.3. Change of unit energy cost with wind speed (
IGEC-198

13. Wind speed data used in this study
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
Wind speed data used in this study
In this study, the wind speed data of point marked with X in Figure 4, which is Çeşme-Kocadağ, on the Aegean Sea coast of İzmir-Turkey. The data is also given in Table 4.
Fig.4. Location of Kocadağ point (
IGEC-198

14. Wind speed data used in this study
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
Wind speed data used in this study
Table 4. Annual and monthly wind speeds at Kocadağ Point
Location
Year
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sep.
Oct.
Nov.
Dec
Kocadağ
1994
9,5
7,3
6,7
11,1
8,5
1995
10,1
9,4
9,8
6,4
4,9
10,7
8,0
9,2
8,3
1996
9,1
10,0
7,2
6,2
9,9
1997
8,8
10,3
7,8
6,8
6,5
7,5
8,6
9,6
1998
7,4
7,9
9,3
7,6
8,1
1999
8,9
10,5
2000
9,7
6,3
6,9
2001
N/A
9,0
2002
7,7
7,0
5,3
7,1
2003
2004
2005
11,5
19,9
6,1
8,2
Ave. speed per month
8,4
IGEC-198
(N/A: Not Available) (

15. Wind speed data used in this study
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
Wind speed data used in this study
These values are the data given by Electrical Power Resources Survey and Development Administration-Turkey. The average of these speed values are given in Figure 5.
When the data given in Table 4 is analyzed, the monthly wind speed variation given in Figure 5 is obtained. Then the average speed value is calculated to be 8,4 m/s.
IGEC-198

16. Wind speed data used in this study
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
Wind speed data used in this study
Fig.5. Monthly wind speed variation of Kocadağ Point
IGEC-198

17. MATHEMATICAL MODEL OF WIND TURBINES
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF WIND TURBINES
The power that can be generated by the turbine is expressed as follows;
(W) (1)
 : Specific weight of the air (kg/m3)
R : Turbine radius (m)
v : Wind speed (m/s)
Cp : Power coefficient
Cp is related to the limit speed indicated by , and is maximum at a specific turbine speed under different wind speeds. Therefore, the point that Cp is maximum (Cpmax=0,3-0,5) is the point that the present wind gives maximum power (Muljadi et al., 1999).
IGEC-198

18. MATHEMATICAL MODEL OF WIND TURBINES
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF WIND TURBINES
Tip speed ratio is given as;
(2)
Here ; is the angular speed of the shaft. Torque of the wind turbine is given as:
(Nm) (3)
Here, Ct is torque coefficient and is defined as;
(4)
Cp =  Ct
IGEC-198

19. MATHEMATICAL MODEL OF WIND TURBINES
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF WIND TURBINES
For constant pitch angle the variation of power coefficient Cp versus tip speed ratio is given in Fig. 6.
Fig.6. Variation of Cp with .
(Duru, T., et al., 2003)
IGEC-198

20. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
In wind turbines where the wind speed is constant and under high power, synchronous generators are preferred. However, since wind characteristics are usually variable, the component to generate electrical energy needs to have similar characteristics.
Since the induction generators are capable of generation electricity both under constant and variable speeds, squirrel cage induction machines are widely used as generators (Orabi et al., 2004).
As the induction machine works as a generator, magnetizing current and the reactive power needed are supplied by the source and convert the mechanical power of the shaft into electrical power to feed the source.
Under constant frequency, working as a generator takes place only over synchronous speed. In order to obtain constant amplitude and frequency, generator output is supported with converter, inverter, filter and rectifier.
IGEC-198

21. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
Using a frequency controller the asynchronous machine can be used as a generator under every speed.
Induction generators are preferred due to their low costs, simple structures, high efficiency values, and for being safe, without electromagnetic oscillations.
In the case that an induction machine is employed as a generator, efficiency can be obtained at levels up to 82% under full load.
A three phase, squirrel cage induction motor, can be used as a self-excited generator with the capacitor group connected to the stator coil ends. Initial speed of the excitation by the capacity depends on the residual magnetism values of the rotor.
IGEC-198

22. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
The residual magnetism of an induction motor previously worked connected to the network induces an EMF to the stator coils depending on the speed, and current passes through the capacitors (Seyoum et al., 2003).
If the capacitors are empty and without any load, voltage increases in relation with the speed and time, capacity and saturation value of the stator metal core.
Initial speed is now dependant to residual magnetism but the excitation velocity can be reduced by increasing the capacitor values.
Even if the values of the excitation capacitors are increased, after a specific frequency, the voltage starts decreasing. This shows that the iron core has reached saturation. After that value, excitation capacitors behave as a load.
IGEC-198

23. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
In this study, self-excited, three phases, squirrel cage induction machine is used as a generator driven by the wind turbine shaft. Equivalent circuit of the self-excited induction generators reduced to one phase is given in Figure 7.
Fig.7. Equivalent circuit of the induction generators
IGEC-198

24. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
RS ; Stator resistance (ohm)
RR; Rotor resistance
jXS; stator reactance (ohm)
jXR; rotor reactance (ohm)
Rm ; magnetization resistance (ohm)
jXm ; magnetization reactance
jXc ; excitation capacitance
s ; slip, and is defined as:
(5)
IGEC-198

25. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
S; synchronous angular velocity
R; rotor angular velocity
and since
while the generator is working, slip is negative. Stator voltage expression of a squirrel cage induction machine, is as follows:
(V) (6)
VS ; stator voltage
IS ; stator current
LS ; stator inductance
MS,R ; mutual inductance
S ; stator flux
IGEC-198

26. MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MATHEMATICAL MODEL OF THE INDUCTION GENERATOR
The rotor voltage is defined as
(V) (7)
IR ; rotor current
LR ; rotor inductance
MS,R ; mutual inductance
S ; stator flux
Motion equation of the mechanical part is described in equation (8)
J; being inertia coefficient
 ; being viscous friction coefficient
(Nm) (8)
IGEC-198

27. CALCULATING MAXIMUM TURBINE POWER UNDER DIFFERENT WIND SPEEDS
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
CALCULATING MAXIMUM TURBINE POWER UNDER DIFFERENT WIND SPEEDS
The value that makes the power expression in Equation (1) maximum is the point that Cp is maximum. This value is calculated to be 0,495 for =7 by using Figure 6.
The air density is 1,2 kg/m3. The turbine radius in this study is selected as 15 m. Using the average wind speeds for Kocadağ given in Table 4, maximum power values are calculated using Eq.1.
In this study, bound to shaft speed and under various wind speeds, the variations of the turbine power are obtained.
Under different speeds, maximum power points are determined and Pmax= f () is obtained. That variation shown in Fig. 8, ensures Pt = a 2 where “a” is a constant (Muljadi et al., 2001).
IGEC-198

28. CALCULATING MAXIMUM TURBINE POWER UNDER DIFFERENT WIND SPEEDS
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
CALCULATING MAXIMUM TURBINE POWER UNDER DIFFERENT WIND SPEEDS
Fig. 8. Turbine power variation bound to the shaft speed under different wind speed values.
IGEC-198

29. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
The block diagram of the system used for simulation is given in Fig.9.
Fig.9. Block diagram used.
Induction Generator
Turbine
Load
Excited capacity
Rotor Speed
Wind
IGEC-198

30. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
As a result of the simulation conducted using the block diagram given in Figure 9, power curves shown in Figure 10 are obtained. Power variations for each wind speed value are given.
Fig.10. Power variations for different wind speeds
Wind speed: 6,9 m/s
IGEC-198

31. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
Wind speed: 7,8 m/s
Wind speed: 8,4 m/s
IGEC-198

32. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
Wind speed: 8,6 m/s
Wind speed: 9,8 m/s
IGEC-198

33. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
In this study, calculations are conducted according to the monthly wind speed values given by EIE (Electrical Power Resources Survey and Development Administration, Turkey) for İzmir Cesme Kocadağ wind observation station.
These speed values are used in a turbine-asynchronous generator simulation prepared on MATLAB software and power values are calculated. Wind turbine radius is assumed to be 15 m.
It is known that the power coefficient is maximum at the point that maximum power is obtained.
Therefore, in this study, using Figure 6, maximum power coefficient of 0,495 that corresponds to limit speed value 7, is used.
Theoretical and simulation results show that the selected system is capable of obtaining maximum power under different wind speed values.
IGEC-198

34. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
Using the software prepared with MATLAB, maximum power for each wind speed value is determined and illustrated with graphics.
Under minimum wind speed of 6,9 m/s, the calculated power is 69 kW, simulation results give 70,5 kW power.
Under annual average wind speed of 8,4 m/s
Calculated power is ,5 kW
Simulation results give approximately kW
Under maximum wind speed of 9,8 m/s
Calculated power is ,7 kW
Simulation results give ,4 kW.
IGEC-198

35. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
MODELING THE WIND TURBINE-INDUCTION GENERATOR GROUP OF THE DESIGNED SYSTEM
It is obvious that the calculation and simulation results are close. Therefore, the simulation shows the feasibility of a real turbine-asynchronous generator system. It is possible to use MATLAB simulation data to perform the design of the wind turbine plant.
IGEC-198

36. INTERNATIONAL GREEN ENERGY CONFERENCE
IGEC-2
INTERNATIONAL GREEN ENERGY CONFERENCE
YILDIZ TECHNICAL UNIVERSITY
THANK YOU
Prepared by : Nur Bekiroglu
Zehra Yumurtacı
Bedri Kekezoğlu
IGEC-198