A B S T R A C T
The 120-day winds of Sistan are among the most effective local winds in Iran. In recent years, droughts caused by climate change have accelerated the speed of these winds. in this study, the feasibility of using wind energy in zabol station which has good potential for wind energy development was investigated. For this purpose, wind speed data were used with three-hour intervals in a period of twenty years. The two-parameter Weibull distribution was used to describe the wind speed distribution. The results showed that the average wind speed in warm seasons is more than twice the average wind speed in cold seasons. The Wind Rose showed that the most probable winds blow in the northwest direction at the investigated station. The results of trend analysis showed that wind speed has a significant positive trend on an annual scale. The annual average wind power density at the height of 10 meters and 40 meters was calculated as 386.129 and 699.452 W/m2, respectively. Also, the possibility of winds blowing with a speed between 3 and 25 m/s at 40 m is more than 80% of the total hours of wind existence (equivalent to 5987 hours per year), which shows that the mentioned station is a suitable place for installing and developing wind turbines. In order to choose the best wind turbine among different models, it is necessary to calculate the energy cost index. Therefore, due to the continuous wind speed of more than 8 meters per second in 6 hot months of the year, Type II wind turbines are recommended for the study area.
Extended Abstract
Introduction
Energy is one of the most important demands in the development of human societies. As the world population continues to grow and the limited and non-renewable resources of fossil fuels diminish, countries must take action to facilitate greater use of renewable energy resources, such as geothermal and wind energy. Wind power is one of the clean, inexhaustible, and free energy sources, preventing environmental pollution caused by burning fossil fuels. In estimating wind energy production through wind turbine design, the probability distribution of wind speed is absolutely important. There are different distribution functions for studying the wind characteristics of any site. However, the 2-parameter Weibull distribution is the most commonly used function due to its simplicity and accuracy. Iran is in a low-pressure location and has a high wind energy potential in the summer and winter in some regions. Nevertheless, except in a few specific locations such as Binalud and Manjil, the use and exploitation of such clean, renewable sources is still not addressed enough.
 
Methodology
Zabol, with an area of 8117 square kilometers, is the capital of Sistan County and is located in northeastern Sistan and Baluchestan province, Iran. The 120-day wind of Sistan is the strongest wind in Iran, with a speed of up to 120 kilometers per hour, which blows almost from late May to late September (about four months). This work is based on the hourly mean wind speed data for Zabol recorded over twenty years (2001-2020The most widely used model to describe the wind speed distribution is the two-parameter Weibull distribution.). This work determined k and c through the maximum likelihood (ML) technique. Wind power density and wind energy density were calculated using Weibull distribution analysis. This study used the non-parametric Mann-Kendall (MK) test (Kendall, 1975; Mann, 1945) to detect mean wind speed value trends at Zabol station. The number of changes in wind speed values per unit of time (trend slope) was obtained through Sen’s slope. Knowledge of wind direction is important for orienting wind turbines properly. So, a wind rose diagram at an altitude of 10 m is drawn using WRPLOT software.
 
Results and discussion
This study uses hourly wind speed data for Zabol (Sistan) over twenty years for further analysis. The lowest and highest monthly mean wind speed values occurred in December 2009 (2.03 m/s) and July 2001 (13.84 m/s), respectively. The highest and the lowest mean wind speeds appear in 2020 (8.11 m/s) and 2011 (5.33 m/s), respectively. The twenty-year overall mean wind speed for the cold and warm seasons is 4.294 m/s and 9.220 m/s, respectively. This means the mean wind speed in summer is almost twice that in winter.
For a height of 10 meters, the yearly values of k range between 1.64 and 1.98, with an average value of 1.77. The lowest value of the scale parameter c is 5.09 m/s, which was found in 2014, while the highest value is 7.94, which occurred in 2020. The annual values of Vmp vary between 3.00 m/s and 5.20 m/s. The lowest value of the Vop is 7.49, while the highest value is 12.35 m/s. The lowest value of wind power density is 115 and was found in 2014, while the highest value is 485 W/m2 and was found in 2020. Its average value is 386 W/m2 for the same period. The energy values range between 1010- and 4247-kW h/m2/year. The average annual amount of energy for the Zabol station was 3382 kWh/m2/year. According to the results presented, the wind speed increases from May to August, which results in an increasing trend of wind power density. The probability of wind blowing at 3 to 25 m/s is about 74 percent in Zabol at 10 m height. So, the mean wind speed between 3-25 m/s is 5537 hours per year, almost the same as the mean wind speed exceeding 3 m/s. For a height of 40 meters, the wind speed exceeds 3 m/s in 7484 hrs/year (more than 80%). The economic operation of wind turbines requires at least 4000 hours. However, the economic performance of wind turbines in Zabol station is equal to 5987 hours per year. According to different classifications, Zabol seems to be a suitable place for harvesting wind. The long-term monthly and annual mean wind speed trend was estimated using the nonparametric Mann-Kendall test. On an annual scale, wind speed has a significant positive trend at 5%. The significant results of the trend obtained from the Man-Kendall method are consistent with the Theil–Sen Slope results. Knowledge of wind direction is important for orienting wind turbines properly. So, a wind rose diagram at an altitude of 10 m is drawn using WRPLOT software. The wind speed and direction records used to generate the wind rose diagrams belong to the five recent years (2011-2015). The wind rose diagrams at 10 m altitude were also generated for all investigated years (not shown), which resulted in similar findings. The most probable wind blows toward the northwest direction.
 
Conclusion
The main focus of this study was to determine the key factors in wind energy resources assessment in a potentially suitable area for installing wind turbines. Most wind turbines are designed according to cut-in and cut-out speeds, defined as 3 and 25 m/s, respectively. The probability of wind blowing at a speed of between 3 to 25 m/s is about 74 percent in Zabol at 10 m height. So, the mean wind speed between 3-25 m/s is 5537 hours per year. The wind speed rises from May (6.277 m/s) to August (10.519 m/s), resulting in an increasing trend of wind power density from May (217.653 W/m2) to August (611.802 W/m2) at a height of 10 m. According to the results, yearly wind power density in the studied area is 386 and 700 W/m2, respectively, at 10 and 40 m. Therefore, regarding different classification measures, Zabol station is suitable for installing wind turbines. The warm and cold seasons in Zabol are confronted with higher demands for cooling and heating, respectively. As there is still no gas supplier in this area, wind energy could be applied as a potential and cheap supplier for electricity heating and cooling.
 
Funding
There is no funding support.
 
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
 We are grateful to all the scientific consultants of this paper.