Analysis of wind power characteristics and the influence of topography, with a renewable energy generation approach (a case study of Mazandaran Province)

Energy sources, which supply 70% of the world's needs as fuel and uranium fission models, will run out by the end of this century and could clearly cause numerous concerns for humans. The depletion of fossil and nuclear energy sources has long stimulated the scientists and authors’ interest. As a result, extensive researches are being carried out all over the world to replace new and cleanly-sources of energy. The behavior of meteorological phenomena under environmental constraints leading to complicated mechanisms has received less attention in the research of Iranian meteorologists and meteorologists, especially in mountainous regions. Environmental characteristics such as altitude, slope, and hillslope aspect have an important influence on the behavior and atmospheric elements. Wind, as the most influential meteorological phenomenon, has an impact on topographic landscapes. This is evident in the different behavior of winds in mountainous and topographic systems, and in the effect of mountain topography on the generation of different types of winds. The annual average of net energy achieved and the capacity factor, which have significant variations in the distribution of wind speed, are indicator parameters for indicating wind energy potential in specific geographical locations.

Notwithstanding the economic development of the country and the improvement of public welfare in Iran, the way energy resources are exploited has raised concerns about the level of energy consumption and greenhouse gas emissions. Therefore, it is desirable to promote the use of renewable energy sources for the development process of Iran. Due to wind resources and topographical conditions, wind energy occupies a special place as a form of renewable energy in Iran. Therefore, this study investigated the spatial capacity of wind power in Mazandaran Province as a case study. In this contribution, the aim of the research is to assess the energy and evaluate the wind potential as well as to create zone maps with indicators of speed and energy production in order to find a suitable place for building power plants in the windy regions of Mazandaran Province.

Mazandaran Province has a high potential for extractable energy and spatial capacity of wind flow. This province is characterized by a particular topography (from -26 to over 2500 m altitude), a northern hillslope aspects and prevailing winds from west to northwest to north, all of which provide the conditions for wind energy evaluation and spatial capacity. The increase of population in Mazandaran Province as well as its development as the first tourism hub in Iran have drastically reduced the capacity of the province in terms of environmental resources utilization. Therefore, it is necessary to zone different regions of the province, focus on topographical conditions and identify areas suitable for wind turbine construction in order to exploit the wind power potential and meet the replacement demand for cheap renewable energy instead of expensive fossil fuels.

There has been a growing demand for energy in the province of Mazandaran in recent years. Considering the capabilities of the province to generate new energy, recognizing and consuming wind energy as a source of renewable energy should be a planning priority. In this study, a statistical analysis of daily wind speed and direction at a height of 10 m in 15 synoptic meteorological stations of Mazandaran Province over a 12-year period (2006 to 2017) was conducted to provide a preliminary estimate of the extractable energy and spatial capacity of wind flow. In addition, the characteristics of wind speed and direction, Weibull probability distribution parameters and wind power potential and density of the stations were also determined. ArcGIS interpolation method (IDW) was used to prepare the calculated layers of the average speed, speed continuity, and power density of the wind at 10, 30, and 50 m heights. Furthermore, to examine the influence of topography on the wind variables, the Pearson correlation coefficient was used to evaluate the relationship between altitude, hillslope aspect, and slope indicators with each of the wind variables.

A map of wind speed zones at 50 m height reveals that Baladeh station has a maximum wind speed in July. The correlation coefficient between wind speed and altitude above sea level was 0.677, indicating a 95 percent positive correlation (P-value 0.05). Accordingly, as the altitude of the meteorological stations in the province above sea level increases, the wind speed increases at a height of 10 meters above the ground. To investigate the influence of topography on wind variables such as wind speed, continuity, and wind power density, the relationship between height and slope indicators was evaluated with each of the aforementioned factors. The correlation coefficient between wind speed and altitude above sea level was 0.677, indicating a 95 percent positive correlation (P-value 0.05). Accordingly, as the altitude of the meteorological stations in the province above sea level increases, the wind speed increases at a height of 10 meters above the ground. Examination of the spatial distribution of wind speed at different altitudes shows that as the altitude increases, the average wind speed also increases. This increase results in the average wind speed increasing from 2.05 m/s at altitudes less than 200 m to 2.52 m/s at altitude 2500 m. The correlation coefficient between wind power density and altitude is 0.647, indicating 95% positive correlation (P-value 0.05). Thus, like wind speed, wind power density also increases with by increasing the altitude. However, due to a P-value greater than 0.05, the correlation between wind hour continuity with a speed 3 m/s and more was not significant at 95% level. Therefore, changes in altitude have no significance effect on the continuity of wind hours. According to P-values greater than 0.05, none of the wind variables is correlated with the slope index. Therefore, changes in the slope values have no noticeable effect on the wind variables and the correlation between them cannot be investigated. After P-values greater than 0.05, among the wind variables, only the number of hours of wind with speeds greater than 3 m/s shows a strong positive correlation with the hillslope aspect. Thus, changes in the aspect of hillslopes have a discernible effect on the continuity of wind hours with speeds greater than 3 m/s at the 95% confidence level (P-value = 0.039), indicating that the hillslope aspect variable affects the number of wind hours with high-speeds in the region. This effect results in the maximum number of wind hours with speeds greater than 3 m/s occurring in the southwestern hillslopes with 2950 hours. The southern and southeastern hillslopes, with 2897 and 2740 hours, respectively, are in the next categories with the highest number of wind hours with the minimum suitable speed threshold for wind turbine operation and installation. Hillslopes with no direction (flat) and those with northwestern direction, with 2336 and 2628 hours, respectively, have the least wind speeds greater than 3 m/s. The correlation between the wind speed and density variables with the hillslope aspect index cannot be investigated because there is no meaningful correlation between them.

Among renewable energy sources, the use of solar and wind energy seems to be more economical and cost-benefit in Iran. Due to the high cost of converting solar rays into electrical energy, several countries around the world, including Iran, have turned their attention to wind energy. Given the enormous resources needed to generate one kilowatt of electricity, the question is what should be done to reduce consumption and provide cheaper energy. Wind energy is one of the most cost-benefit renewable energy sources for power generation, which is not only polluting the environment and being abundant and permanent, but also has the lowest price fluctuations. The objective of the study was to determine the spatial capability of wind power in Mazandaran Province, with emphasis on topography. With the increase of altitude of meteorological stations of the province, the wind speed and power density of the station increases at a height of 10 meters above the ground. Although there is no significant correlation between the number of wind speed hours equal to or more than 3 m/s and it cannot be assumed that variations in altitude affect wind hour continuity values. Examination of the spatial distribution of wind speed with increasing the altitude showed that the average wind speed increases from 2.05 m/s in the altitude less than 200 m to 2.52 m/s in the altitude 2500 m. The effect of the hillslope aspect on the changes in the number of the continuity wind hours with a speed greater than 3 m/s in Mazandaran Province, is such that its maximum value occurs in southwestern hillslope with 2950 hours. This may be influenced by the general pattern of air current in the region, where west and southwest winds are considered to be the prevailing winds at all seasons of the year and during most months of the year. The western, coastal strip, as well as the plain areas of Mazandaran Province have poor wind continuity conditions, which are a minimum threshold for wind turbine installation. The foothills and highlands, on the other hand, are in a relatively favorable position in terms of the persistence of winds with speeds of 3 m/s or more. The mountainous and highland areas in Noor Township are generally considered the best locations for wind turbine installation. The maximum wind speed occurs at different heights above the ground, in the southern and high parts of Noor, Amol, Nowshahr, Savadkooh and to some extent in Chaloos, with the highest wind speed in the southern parts of Noor. The plains and coastal areas of Mazandaran Province, particularly the townships of Jooybar, Babolsar, Mahmoudabad, Sari, Ghaemshahr, the north of Savadkooh, Babol, Amol and the western parts of Ramsar and Tonekabon, and the eastern parts of Behshahr and Neka, have the lowest average annual wind speed.