Environment Analysis of the Wind Resources in Saharan Atlas of Algeria: Adrar Region as a Case Study

An objective analysis of the wind atlas map of the region of Adrar (Algeria) at a height of 10 meters above ground is essential, in order to classify these velocities according to the Pacific Northwest Laboratory (PNL) classification, and then to develop the separation velocity map. The present work is conducted in the region of Adrar to determine the monthly, seasonal, and annual energy generated by the Whisper200 wind turbine by using the Rayleigh distribution and the wind data recorded every three hours from January 1st, 1961 to December 31st, 2018. From the obtained findings, the northeast region of Adrar is a suitable region for wind applications. The surface of this area is equal to 16587 km², where two sites are located (Kaberten and Aougroute). However, the second PNL class is divided into seven zones. The wind speed in this region (2nd PNL class) is favourable for the setup of isolated wind turbines or hybrid systems. The following cities are located in this region (2nd PNL class): Adrar, Aoulef, Bordj Baji Mokthar, Timaiaouine, Regagne, and Timimoune.


A B S T R A C T
An objective analysis of the wind atlas map of the region of Adrar (Algeria) at a height of 10 meters above ground is essential, in order to classify these velocities according to the Pacific Northwest Laboratory (PNL) classification, and then to develop the separation velocity map. The present work is conducted in the region of Adrar to determine the monthly, seasonal, and annual energy generated by the Whisper200 wind turbine by using the Rayleigh distribution and the wind data recorded every three hours from January 1st, 1961 to December 31st, 2018. From the obtained findings, the northeast region of Adrar is a suitable region for wind applications. The surface of this area is equal to 16587 km², where two sites are located (Kaberten and Aougroute). However, the second PNL class is divided into seven zones. The wind speed in this region (2nd PNL class) is favourable for the setup of isolated wind turbines or hybrid systems. The following cities are located in this region (2nd PNL class): Adrar, Aoulef, Bordj Baji Mokthar, Timaiaouine, Regagne, and Timimoune. doi: 10 The characteristic of the wind at a particular location leads to the ideal use of wind energy and the most important aspect of the assessment of wind resources is the distribution of wind speed. In 1980s Algeria, Ibrahim *Corresponding Author Email: benmedjahed_78@yahoo.fr (M. Benmedjahed) [1] was the first one to start studying the measurements of the available wind parameters that have been summarized in the ONM meteorological reports, which identify the average wind speeds and frequencies for various meteorological stations. Bensaid [2] proposed a classification of wind speeds according to the topography of the country. However, these results are based on measurements made over short periods. Benmemdejah ed and Mouhadjer [3] performed a statistical investigation of 37 stations with the help of the Wasp software that is used for the wind mapping of Europe. The obtained findin gs were employed to achieve the first wind map of Algeria by Merzouk [4]. Chellali et al. [5] updated the wind data by proposing a new wind map that included the Hassi Raml site as a strong wind site, which was neglected by the maps. Boudia [6] improved the temporal evaluation of wind deposits and thus contributed to updating the wind map in Algeria (update of the wind atlas for 10 meters above the ground and development of the wind potentials in the eastern zone of the desert and the western zone of the highlands. Nedjari et al. [7] updated the wind map with the addition of 74 new locations in Algeria eligible for wind projects. Although different wind maps did not take into account the topography of Algeria, they agreed that the Adrar region has good wind potentials, which makes it suitable for the installation of wind farms or isolated wind turbines. This region is very large and has a low population density. It is remote difficult to connect with the national network; therefore, the use of isolated wind turbines is the solution. Indeed, Adrar region is chosen as the first region of Africa to install wind turbines in 1953. This region was also chosen to install the first Algerian wind farm (Kbarten wind farm) in 2014 [3].
In this article, the wind atlas map of the Adrar region at a height of 10 m above the ground is analysed. The analysis allows to make a classification based on the Pacific Northwest Laboratory (PNL) orientation, and then to establish a map of speed classes for the studied region. The monthly, seasonal, and annual energy generated by the Whisper200 wind turbine is determined by using the Rayleigh distribution and the wind data recorded every three hours from January 1 st , 1961 to December 31 st , 2018.

Adrar region
The Adrar region is located in the southwest of Algeria, more than 1200 km from Algiers. It is located between the meridians: 2 ° E and 6 ° W, and the parallels: 20 ° N and 32° N °. Its total area is 427.948 km², or about 18% of the total area of Algeria. It is bounded from the North by the Grand Erg West, from the South by the Tinzoft tray, from the East by the Tademaït tray, and from the West by Erg Chech [8].
The climate of this region is desert. According to the Classification of Köppen BWh [9], the desert climate is characterized by an extreme dryness with rare and weak precipitations, very hot heats with excessively high temperatures during a long period, a very strong solar irradiation with a record duration of sunshine in a large part, as well as a very low humidity.
The hydrographic grid of Adrar is part of the western basin of the northern desert, and it testifies to the internal surface flows during the humid wet periods. In the studied region, there are two main rivers, namely Oued Messaoud and Oued Tilia [3].
The nature of the plant tissue of the Adrar region is typically Saharan. The vegetation is found mainly in Orchards, Ksour, and in Oases. An abundant flora in places, for example in Bordj Badji Mokhtar, where species like the Acacia, Aristide and others thrive are encountered. This region also has a significant number of birds, about 83 species, where more than 50% of which are migratory [3].
The studied region has 399.712 inhabitants, with a population density equal to 0.9 inhabitants per km². Adrar, Timimoun, and Aoulef are the largest cities in the region among the 28 cities that make it up, while the cultivated agricultural area increased to more than 70,000 hectares in the region for the agricultural season (2017-2018) [3].

Wind atlas analysis
Using the carat global wind atlas, the wind speed atlas at 10 m above the ground in the region under study was established (Figure 1). From Figure 1, it can be said that the average wind speed is related to the graphical character, the windiest zone is located at Tademaït tray in the northeast. The wind speed in this zone ranges from 6 to 7 m/s, while the second windiest zones are located in Northwest and West. The wind speed in this zone ranges from 5 to 6 m/s. However, the wind speed is weak in the central and southern zones, except for some locations as Bordj Baji Mokthar and Timaiaouine.

PNL classification
The PNL Classification, which was used by Boudia et al. [10], is a form of classification of wind resources proposed in 1987 by Elliott et al. [11]. Each class (from 1 Figure 1. Adrar wind atlas at 10 m from ground to 7) presents a range of wind power density in (W/m²) and an equivalent average speed range in (m/s) at different heights. From class 4, where the average wind speed ̅ ≥ 5.6 m/s, the site is considered suitable for wind applications. Class 3 or 5.2≤ ̅ ≤5.6 m/s are considered to be an area conducive to the development of wind energy using very high pylons. Class 2 with 4.4≤ ̅ ≤5.2 m/s is considered a marginal area for the development of wind energy. As for class 1, it is considered as an area not suitable for such energy installations.
Adrar classification according to PNL is illustrated in Figure 2. From this figure, it can be noticed that the northeast zone belongs to the 4 th classes of PNL classification. This means that is a region suitable for isolated wind turbine or wind farms. The surface of this zone is equal to 16587 km 2 , where two sites are located, namely Kaberten and Aougroute.
It is also noticed that four zones belong to the third class, with a total surface of these zones of approximately 41777 km 2 . In these zones, where two sites are found (Zaouiet Debagh and Tinerkouk), a wind park composed of wind turbines characterized by a high hub is installed.
The second PNL class is divided into seven zones; this wind speed class is favourable for the setup of hybrid systems or isolated wind turbines. The following cities are located in this region: Adrar, Aoulef, Bordj Baji Mokthar, Timaiaouine, Regagne, and Timimoune.

Wind data
Values of the temperature and wind speeds are recorded in every 3 h from 01/01/1961 to 31/12/2018. The Rayleigh distribution, which is a special case of the Weibull distribution, was used to find out the wind distribution. It is expressed as follows [12][13][14][15][16][17][18]: The Rayleigh distribution was used at the same height of the wind turbine. To calculate the energy produced, the values of the wind speed v were extrapolated to the height of the wind turbine model introduced by Justus et al. [19] (the exponent of power law) to determine the wind speed v2 at the height hub h2, expressed by the followin g equation: where the exponent of power law α is given by [19]: The annual, seasonal, and monthly distributions at 10 m and 25 m from the ground are presented in Table 1   At the 2 nd height (i.e., 25 m), the esteemed scale parameter C varies from 5.7 m/s (February) to 8.1 m/s (April), while the average wind speed ranges from 5.1 m/s (February) to 7.1 m/s (April). This makes the seasonal scale parameter ranging from 6.4 m/s (Winter) to 7.5 m/s (Spring), while the average wind speed is varying between 5.6 m/s (Winter) and 6.6 m/s (Spring). The annual scale parameter and average wind speed were found to be equal to 6.8 and 6.1 m/s, respectively.

Wind turbine
The monthly distributions of wind were used to estimate the energy that can be obtained using a small wind turbine (Whisper200) [20]. The characteristics of the wind turbine of the classical model are summarized in Table 2.

Wind energy
The wind power is related to the average wind velocity (v) by a section S with an air density ρ as follows [21][22][23][24][25]: The density of air (ρ) vs. the temperature T and the altitude Z is given by [26][27][28][29][30][31][32]: Based on the above hypothesis, the electrical energy E (kWh) that can be generated by a wind turbine during a period t, is given by : The trapezoidal rule is employed to determine the electrical energy E induced by the wind turbines. This rule, that is provided by Newton and Kutz, is more accurate than the primary method, called rectangles, which corresponds to the Riemann amounts consis ting of replacing the initial function by stepped approximatio n [33][34][35][36][37]: A procedure has been developed to evaluate the energy efficiency of the different turbines. The monthly assessment of wind energy produced by Whisper200 with a rated power equal to 1 kW is shown in Figure 3. It can be observed that the wind turbines (Whisper200) are more efficient in March than the other months. The monthly electric power ranges from 241.92 kWh (February) to 327.36 kWh (March).  The seasonal and annual assessments of the wind energy produced by Whisper200 are summarized in Table 3. From Table 3, it can be observed that the wind turbines (Whisper200) are more efficient in Springer than the other seasons. The monthly electric power ranges from 792.48 kWh (Winter) to 911.76 kWh (Spring). As a result, the annual electric wind energy produced by Whisper200 in Adrar location was found to be equal to 6.8 m/s and the annual average wind speed equal to 3343.20 kWh.

CONCLUSIONS
This paper aimed to evaluate wind resources in the southern region of Algeria, Adrar as a case study. The results obtained are:  The average velocity of wind is related to the geographical position of the studied region, where the windiest zone is located at Tademaït tray in the northeast;  The northeast zone of the investigated case is suitable for isolated wind turbines (IWT) or wind farm, since it belongs to the 4 th classes of the PNL classification.  Four zones with a total surface of approximat ely 41777 km 2 belong to the third class. The wind park that is composed of wind turbines characterized by a high hub may be installed in these zones, where two sites are found, namely Zaouiet Debagh and Tinerkouk;  The following cities: Adrar, Timimoune, Regagne, Aoulef, Timaiaouine, and Bordj Baji Mokthar, belong to the 2 nd PNL class. These cities are suitable for the setup of IWT or hybrid systems.  The wind turbines (Whisper200) are more efficient in March than the other months. The monthly electric power ranges from 241.92 kWh (February) to 327.36 kWh (March), while the monthly electric power ranges fro m 792.48 kWh (Winter) to 911.76 kWh (Spring). The annual electric wind energy produced by Whisper200 in Adrar location was found to be equal to 3343.20 kWh and the annual average wind velocity was equal to 6.8 m/s.