APPLIED SECOND LAW OF THERMODYNAMICS ON THE WIND ENERGY OVER IRAQ

Although Iraq is an oil country, but it’s have very large sources of renewable energy. This study was discussed the results of the wind energy and exergy for six regions in Iraq at three different turbine heights. The highest exergy efficiency was in Basrah then Anbar, Tikrit, Najaf, Baghdad, and smallest in Mosul. The exergy efficiency was increase by 60 % at height 50 m, while it’s increasing by 70 % at height 100 m. The highest exergy destruction was in Mosul, Najaf, Tikrit, Baghdad, and smallest in Anbar and Basra. The exergy destruction decreasing by 33 % at height 50 m, while its decreasing by 68 % at height 100 m. The high energy efficiency was in Basra, then Anbar, Tikrit, Najaf, Baghdad, and the smallest in Mosul, the energy efficiency of a turbine increase by 52 % at height 50 m, while it’s increasing by 66 % at height 100 m. And the highest output useful energy was in Basra, then Anbar, Tikrit, Baghdad, Najaf, and it’s very small in Mosul, it is found that the output energy from turbine increase by 85 % at height 50 m, while its increase by 94 % at height 100 m


Introduction
The renewable energy resources have been significantly important in later years because the increasing environmental pollution, large request of energy required and exhausting fossil fuel resources. Many sources of renewable energy include wind, solar, geothermal, hydro, biomass and ocean energy have pulled in increasing attention due to their almost boundless and non-polluting characteristics. Among these resources wind energy has proved to be a cheaper elective energy resource and hence broad research efforts have been put to improve the technology of electricity generation through wind [1].
ISSN 2520-0917 Tuz and Tikrit stations. In Tuz the range (2.5-3.0 m/s) taken about 45% from the total wind, In Tikrit the high ranges of wind (3.5-4.0 m/s) taken about 40.9% of wind speed, but the low wind speed is found at Biji, Kirkuk and Mosul. This is affected on the maximum energy output (13.5 kW/h) at Tikrit station. O. T. Al-taai et al. [11] studied the analysis of winds to produce electricity in Iraq for fifteen regions at three heights (12,50,100 m) and the results shows that the maximum values of wind power and the wind power density and Weibull parameters at Basra, the medium values at Baghdad and the lowest values in Mosul.. E. Asgari and M.A. Ehyaei [12] investigated mathematical modeling of wind energy, results proved that genetic algorithm is a more productive method than searching method. The genetic algorithm shows the output power, first and second law efficiencies, increased by 61%, 56.5%, and 62.2%, respectively, at cut-in, rated, and furling speeds (u c = 1.27, u r = 12.19, u f = 15.73) m/s. And the searching shows the output power, first and second law efficiencies, increased 8.4%, 8.5%, and 8.4%, respectively, at cut-in, rated, and furling speeds (u c = 2.99, u r = 13.31, u f = 15.05) m/s. K. S. Heni et al. [13] compute wind power density for the horizontal and vertical wind turbine in Karbala City, and the results shows that the total power density, wind speed, Weibull parameters (c) and (k) at 10 m height are (102 W/m2), (4.1 m/s), (4.6 m/s), and (1.64) respectively, at 30 m height are (167 w/m2), (4.9 m/s), (5.5 m/s), and (1.69) respectively, and at 80 m height are (279 W/m2), (5.89 m/s), (6.6 m/s), and (1.74) respectively.
This paper was discuss the results of the exergy and energy analysis of the wind turbine in different regions over Iraq, studies the effect of differences heights on the performance of the wind turbine and selected the suitable zone to builds this system.

Case Study
The data of annular wind speed at height 12 m that used in this work was obtained from the Iraqi Meteorological Organization and Seismology and from reference [5] for six locations distributed of different regions in Iraq show in Fig. 1, the regions are (Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra) as shown in Table 1 [11].  The Weibull distribution parameters k-Shape parameter and c (m/sec) scale parameter in three high (12,50, 100 m) for six regions was obtained from [11] as shown in Table 2. And the characteristics of wind turbine (3 kW) that using in this study as shows in Table (3) [11].

Energy and Exergy Analysis
This section deals with the first and second law of thermodynamics, the energy efficiency ( ) is defined as the ratio of useful output work to the kinetic energy of wind stream [1] (1) While the exergy efficiency ( ) refers to the ratio of useful output work to the exergy flow of the wind [1] (2) The electrical energy that generated from the wind turbines is considered as the useful work output of the wind turbine. The useful output work of the wind turbine depends on. The model that used for useful work output of the wind turbine ( ) is given by Abdel Hamid (2009) [15] this model is depended on cut-in speed (u c ), rated wind speeds (u r ), furling speed (u f ) and on specific site, such as the Weibull distribution parameters k-Shape parameter and c (m/sec) scale parameter: Where is output energy and can be calculated from [15] (4) Where is the mechanical energy is the power coefficient of a wind turbine are the mechanical and alternator efficiency, that's equal to 0.98 and 0.97 respectively [4] The mechanical energy can be calculated from [8] (5) Where A is the swept area of the turbine is the density of air V 1 is the upwind velocity of turbine V 2 is the final velocity of turbine The density of air depended on temperature and pressure of air and was calculated using the ideal gas law Equation [15] (6) Where P is the pressure of air T is the temperature of air The final wind velocity (V 2 ) is equal to one third of the upwind velocity (V 1 ) [16] (7) The power coefficient of a wind turbine ( ), was determined as a function of the tip speed ratio (λ), number of blades (Nb) [15] ( ) [ The power coefficient of turbine will be decreased if the number of blades was reduced at the same tip speed ratio. The wind turbines that have two blades must operate at a higher tip speed ratio than three bladed turbines to maintain the same power coefficient. While the tip speed ratio can be expressed in terms of tip speed and free stream wind velocity [15] (9) Where is the angular velocity (rad/s) is the radius e of the turbine is the stream wind velocity The Energy of the wind stream ( ) describes the total kinetic power of a wind stream and can be found [1] (10) Where is the density of air, can be estimated from equation (6) A is the swept area of the turbine is the wind velocity The exergy of flow Ex f , is the maximum achievable work gained as the air flows through the turbine. This term includes physical exergy (Ex Ph ) and kinetic exergy (Ex Ke ) [8] (11) Physical exergy incorporates the enthalpy and entropy changes related to the turbine operation as [8] ̇ * ( ( ) ( ) )+ (12) Where ̇ is the mass flow rate of the air through the turbine is the specific heat of air and are the wind chilled temperature of outlet and inlet to turbine respectively is the ambient temperature is the general gas constant and are the air pressure of outlet and inlet to turbine respectively is the average temperature of the outlet and inlet to the turbine The mass flow rate of the air through the turbine is represent as Where is the density of air, can be estimated from equation (6) A is the swept area of the turbine is the upwind velocity of the air The outlet and inlet wind chilled temperature can be found as [17] [ ] [ ] Where and are the wind chilled temperature of outlet and inlet to turbine respectively V 1 is the upwind velocity of turbine V 2 is the final velocity of turbine is the ambient temperature The air pressure of outlet and inlet to turbine can be found as [8] (16) (17) Where and are the air pressure of outlet and inlet to turbine respectively is the atmospheric pressure V 1 is the upwind velocity of turbine V 2 is the final velocity of turbine Kinetic exergy represent the maximum net velocity of the flow stream that converted into power that drives the turbine [1] The exergy destruction ( ) is a representative measure of the irreversibility of the process. It offers a helpful elective measure of turbine efficiency that incorporates the irreversibility, which were not included in the first law analysis. The specific exergy destruction can be defined as [8] ̇* ( ( ) ( ) )+ Where ̇ is the mass flow rate of the air through the turbine is the ambient temperature is the specific heat of air and are the wind chilled temperature of outlet and inlet to turbine respectively is the general gas constant and are the air pressure of outlet and inlet to turbine respectively is the average temperature of the outlet and inlet to the turbine Since the values of velocity at a height of 12 m, so can be use the following equation to calculate the wind velocity at other heights (50 and 100) m [12]:

(21)
Where z 1 is the reference height (m), z 2 he turbine height (m), and is the wind velocity at heights z 1 and z 2 , respectively, a and b are coefficients, typical values of (a) and (b) is 0.11 and 0.061 in the daytime and 0.38 and 0.209 at night are recommended [12].

Results and Discussion
This section was presented the results of the first and second law analysis, the results of two Weibull parameters, wind velocity, wind chill temperature, air pressure, wind energy, output energy of the turbine, energy efficiency, exergy destruction, and exergy efficiency were discussed at different height (12, 50, 100 m) for six regions in Iraq (Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra). The results obtained from this study can be summarized as follows. Fig. 2 and 3 shows the two Weibull parameters the scale parameter (c) and shape parameter (k) for six regions in Iraq at different height. The values of k and c are drawing according to table (2) [11] to show the behavior of two parameter (c and k) at different height for all selected six regions, the higher value of parameter (c) lead to higher output energy. It is obvious that the average value of the parameter k has a much smaller than the average value of the parameter c. The smallest value of c was 1.993 (m/s) in Mosul at (12) m and the highest value was 6.5 (m/s) in Basra at (100) m, also can be noted that the c value of Mosul and Najaf was same at (100) m. While the smaller value of k was 1.875 in Najaf at (12 and 50) m and the highest value was 3 in Baghdad and Tikrit at (50) m, also can be noted that k value of Baghdad and Tikrit was same at (12 and 50) m.   (20). The output energy of the wind turbine was increase as the velocity increase so that the second and first efficiency will be increase. It is can be seen that the smaller value was 1.3, 1.94, and 2.35 (m/s) in Mosul at (12,50, and 100) m height respectively, while the highest value was 3.8, 5.76, and 6.88 (m/s) in Basra at (12,50, and 100) m height respectively, also the wind velocity value of Basra and Anbar was close together. The wind velocity increasing by 33% when the turbine height become 50 m for all regions, while its increasing by 45% when the turbine height become 100 m for all regions.   (14) and (15), as the different between inlet and outlet wind chill temperature was increase due to increase in exergy flow and causing to decreases in exergy efficiency according to equation (2). It is can be seen that the smaller value was 27.07, 26.51, and 26.24 (°C) in Basra at (12,50, and 100) m height respectively while the highest value was 28.33, 27.91, and 27.68 (°C) in Mosul at (12,50, and 100) m height respectively, this result represent the equation (14) where at wind velocity increase led to decrease in wind chill temperature, also can be notes that wind chill temperature value of Basra and Anbar was close together.  Figure 6 shows the relationship of air pressure for six regions at different height. The value of average air pressure can be calculated by using equations (16) and (17), as the ratio of (P 2 /P 1 ) was increase due to converted to useful energy and lead to reduce the exergy flow and causing of increase in exergy efficiency. It is obvious that the smaller value was 92.57, 81.97, and 72.83 (kPa) in Basra at (12,50, and 100) m height respectively while the highest value was 100.22, 98.98, and 97.91 (kPa) in Mosul at (12,50, and 100) m height respectively, this result represent the Bernoulli equation where at velocity increase the pressure should be decrease, and the pressure for same regions was decrease as the height increase , also can be notes that air pressure value of Basra and Anbar was close together.  Figure 7 shows the relationship of wind energy for six regions at different height. The value of wind energy was calculated from equation (10), as the wind energy increase lead to converted more energy to turbine and due to increase the energy and exergy efficiency. It is obvious that the smaller value was 20.95, 69.46, and 124.33 (W) in Mosul at (12,50, and 100) m height respectively, while the highest value was 523. 15, 1734.8, and 3105.37 (W) in Basra at (12,50, and 100) m height respectively, wind energy generation can be higher in the south region as the wind speed are strongest for all heights.
The maximum values in Basra , the medium values in Najaf, Tikrit, Baghdad, Anbar and the lowest values in the northern region Mosul because of this region locates between mountain while in the south is an opening lands area. The wind energy is increasing by 69% at when the turbine height become 50 m for all regions, while its increasing by 83% when the turbine height become 100 m for all regions.  Figure 8 shows the relationship of output energy for six regions at different height. The output energy of the turbine was estimated by equation (3), the output energy of the wind turbine was increasing as the velocity of the air and the c-parameter was increase, the energy efficiency of the turbine was increase as the output energy increase. It is can be seen that the smaller value was 0.05, 0.47, and 1.07 (W) in Mosul at (12,50, and 100) m height respectively, while the highest value was 29.59,182, and 427.47 (W) in Basra at (12,50, and 100) m height respectively, this result represents the equation (3) where it is mainly depended on the Weibull distribution parameters k-Shape parameter and c (m/sec) scale parameter.
The exergy destruction of turbine decreasing by (32, 38, 41, 52, 33, and 50) % in (Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra) respectively, when the turbine height become 50 m, while its decreasing by (51, 60, 70, 83, 56, and 86) % in (Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra) respectively when the turbine height become 100 m.  Figure 11 shows the relationship of exergy efficiency for six regions at different height. The exergy efficiency can give a better understanding of the losses in energy that happening in the wind turbine due to irreversibility. Targeted efforts can then be made to overcome these losses. It is can be seen that the smaller value was 0.57, 2.1, and 3 (%) in Mosul at (12,50, and 100) m height respectively, while the highest value was 24.36, 49.63, and 66.98 (%) in Basra at (12,50, and 100) m height respectively, this result represents the equation (2).

Conclusions
The wind energy in Iraq is very limited. The main aims of this study were to recognize the wind characteristics such as (Weibull parameters c and k, wind velocity, wind chill temperature, air pressure, wind energy, output energy of the turbine, energy efficiency, exergy destruction, and exergy efficiency) for six regions in Iraq. This regions located at Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra) at three different turbine heights (12,  % at height 50 m, while its increasing by (70, 69, 78, 60, 56, and 58) % at height 100 m, for (Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra) respectively 7-The highest output energy was in Basra, then Anbar, Tikrit, Baghdad, Najaf, and it's very smaller in Mosul 8-The output energy from the turbine, increasing by (88,84,84,87,86, and 83) % at height 50 m, while its increasing by (94,94,96,93,93, and 93) % at height 100 m for (Mosul, Tikrit, Baghdad, Anbar, Najaf, and Basra) respectively 9-As the results that obtain from applied first and second law of thermodynamics on the wind turbine, it is note that the suitable location to installation the wind turbine system in south regions of Iraq.