Suitability Assessment of Lands to Establish Photovoltaic Fields by Combining Fuzzy Inference Systems and Simple Additive Weighting in Iran

Introduction
Energy is one of the necessary factors for industrial activities and a requirement for today life. Hence, demand and supply of energy in human society is increasing continuously. Population growth and its distribution, along with the increasing need of human being to newer and more efficient energy resources have changed the human approaches to natural renewable energy forms. Since the fossil fuels as the primary fuels of are going to exhaust rapidly and cannot be a reliable energy source as well as due to the global warming issue, the use of fossil fuels should be limited as soon as possible. Henceforth, renewable energy resources were proposed to solve these challenges.
Solar energy is one of the best and most economical renewable energy in Iran. This energy not only can resolve many human concerns such as environmental pollutions, newborn diseases, energy finitude, and energy transformation, but can also be well developed in climate of Iran.
As the photovoltaic systems are one of the most efficient systems in producing solar electricity and can be employed in a vast area of Iran, a significant proportion of energy consumption of Iran can be supplied by developing these systems. Photovoltaic cells transform solar energy into electricity directly. In this process, semiconductor materials such as Silicon, Gallium Arsenide, or Cadmium Telluride are used. Today, about 95 percent of the world solar cells are made of Silicon.
Since the prime cost for establishing photovoltaic field is relatively high, optimizing the establishment sites of these systems can play a key role in increasing the efficiency of the system. The aim of this study is to introduce a new method for spatial optimization of the sites of photovoltaic fields in Iran.
Materials and Methods
In this research the DELPHI technique was employed to identify the effective factors. The DELPHI is a systematic process for collecting and classifying the knowledge of experts through distributing questionnaire between the experts and studying the feedbacks. After the DELPHI technique carried out, 14 criteria were extracted and then classified into three main groups. In order to weight the criteria, the Analytical Network Process was employed. To do so, the pairwise comparison questionnaire was produced and distributed to the experts. According to the results derived from the questionnaire, the pairwise comparisons were done in Super Decision software and the weight of each criterion was calculated. An initiated model is introduced to combine Simple Additive Weighting method and Fuzzy Inference System. In the mentioned technique, the main entrance of the final layer is a result of Simple Additive Weighting. Primarily, the concluded layer from the Simple Additive Weighting was classified into six classes of very poor, poor, moderate, good, very good, and excellent using the trapezoidal membership functions and then the fuzzy laws were defined based on the requirement of the research. After the output distribution map was concluded for each law, all outputs were added together and the whole study area was divided into seven areas of inappropriate, very poor, poor, moderate, good, very good, and excellent. Finally, the experts' viewpoints were used to estimate the accuracy of the results and according to the average of the results, the accuracy of the estimated sites is approximately 84 percent.
Results and discussion
The results indicated that the most effective factors on feasibility of lands in Iran to establish photovoltaic fields are 14 criteria in which the criteria of direct radiation, distance from the power lines, and temperature are of the most importance. However, except for the inappropriate class (mainly because of high slope and improper land use), most of the regions (more than 31 percent of lands of Iran) are in classes of excellent, very good and good. Furthermore, only one percent of the lands are in class 1 (the class poor).
According to the results, Provinces of Yazd, Kerman, South Khorasan, Sistan and Balouchestan, Isfahan, Fars, and Khorasan e Razavi, in order, have the most area in the class excellent, and Provinces of Guilan, and Mazandaran have the most area in the class very poor.
 
Conclusion
Proper use of solar energy requires the identification of highly potential regions. Besides the benefits of using the photovoltaic technology, one of the difficulties of these technologies is the high cost of establishing such power plants. Therefore, recognizing the best regions for installing the photovoltaic equipments could be the main step in the establishment of photovoltaic power plants. In this article, authors have tried to introduce an applied method for optimizing the sites of photovoltaic equipment installation to have the most efficiency and lifetime. The results showed that Iran has very high potential to utilize the photovoltaic technology.