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Thermal Power Plant Site Selection using GIS M. J. Valadan Zoej 1 , M. S. Mesgari 1 , S. Beheshtifar 1 , M. Karimi 1 , R. Samadi 2 , H. Yousefi 2 , T.Sohrab 2 Email: valadanzouj@kntu.ac.ir, smesgari@kntu.ac.ir, Sara_beheshtifar@yahoo.com (1): K. N. Toosi University of Technology (2): Iran Energy Efficiency Organization Abstract Concerning the population growth and development of industrial and agricultural sections, the electric power demand is increasing continuously. Therefore, it is necessary to forecast the load of the electric network and expand the power system for supplying reliable electrical energy. A power plant as a power generating station is one of the essential infrastructures of the electric network. The construction of new power plants is an important part of the electric network expansion. The suitability of selected site for power plant affects the amount of generated energy, power plant's productivity, cost of power generation and transmission (loss of energy), economical development and environment. Therefore, in site selection process for a power plant it is necessary to carefully consider not only the technical issues, but also it's impact on natural environment, economy and near local communities. Since most of the related data to site selection of power plants are geospatial, Geographical Information Systems (GIS) allows for the consideration and combination of various data about geology, topography, water resources, roads, available electric network, fuel supply, land use, etc. In this paper, the required conditions for the establishment of thermal power plants are comprehensively studied and conceptual model of power plant sitting is designed. Later, conventional models for integrating factor maps have been investigated. For experimental test, the factor maps of studied area have been prepared and integrated. Finally the suitable locations for the construction of power plant are selected using GIS. 1. Introduction Electrical energy is an important factor in all aspects of development, including industry, agriculture, environment, and socio-economy in general. In Iran, as a result of population growth, agricultural and industrial development, urbanization and changes in the life-style of people, etc. the demand for electrical energy has been increasing continuously. To respond to this increase in the demand for electrical energy effectively, it is necessary to predict the electricity consumption for the coming years and to plan for the necessary development in the electricity production and transmission network. Power plants as the sources of electricity supply are the most important part of the network. As the first step of network development, existing power plants should be improved and new plants should be established. The construction of a power plant is usually very expensive and time-consuming and has intensive effects on the environment and on all aspects of both people life and socio-economic area. Therefore, comprehensive studies are required before the construction of a power plant. The most important parameters that should be first defined are the type of the power plant, its capacity and the most suitable location for it. In Iran large volumes of natural gas resources has been found. Therefore the policy of the government is to concentrate on the construction of natural-gas thermal power plants in the development of electricity generation. The location of a power plant has significant effects on the efficiency of electricity generation, the price of electricity production and transmission, its environmental impact etc. therefore the selection of the location for a new power plant should be done very carefully and based on the analysis of many different factors. Many of these factors are essentially spatial, and the data about them are from different sources and in different scales. Therefore GIS along with appropriate models and spatial analysis method should be used to define the suitability of different locations for the construction of power plants. 2. Important factors in site selection for power plants In general, both the construction and operation of a power plant requires the existence of some conditions such as water resources and stable soil type. Still there are other criteria that although not required for the power plant, yet should be considered because they will be affected by either the construction or operation of the plants such as population centers and protected areas. The following list corers most of the factors that should be studied and considered in selection of proper sites for power plant construction:
The study area is Fars province, in the southern part of the country with the area of 122780 Km˛. Considering the study area size and the diversity of parameters, it was decided that the study should be done two stages and using data of two different scales. On the basis of available spatial data in the country, using the data of 1:250,000 scale a generally suitable area were selected. Then using 1:25,000 maps more detailed site selection was carried out in the previously selected locations. The Landsat satellite images of year 2002 were used to update the 1:250,000 maps. To be brief, in this paper only site selection based on 1:250,000 maps is discussed. After comprehensive study of selection parameters, all required spatial features are defined and categorized into three main classes of physical, environmental and socio economic features. The three main classes have 13 smaller classes. The classification is presented in table 1. 
4. Spatial data analysis The above mentioned features were represented in different layers from these layers two different types of maps were generated, according to the essence of the related factor and its effect on the suitability of the site: 4.1 Limitation maps Such a map defines the area that cannot be used for the power plant because of a limiting factor. Such a map is binary map, in which the areas with limiting condition (not suitable) are given the value of zero and the allowed (suitable) areas are given the value of one. For example, the area with slope bigger than 10% is represented with zero value (not-suitable) and the areas with less slope are represented as suitable (value one), (Figure 1). The list and criteria for generation of such maps is presented in table2. 
4.2 Factor maps Some of the parameters do not affect the suitability of a location in absolute manner (e.g. making it absolutely unsuitable), yet has a positive or negative effect on the suitability. The effect of such parameters can be modeled by giving them appropriate weights. For example, areas can be given different weights according to their distances from existing gas pipe lines (Figure 2).  Figure 1. Limitation map of slope  Figure 2. Factor map of Gas pipe line These parameters and their given weights are listed in table 3. The weights are the result of discussions with experts in the subject. 
5. Data integration and selection of suitable locations The integration of the data (resulted maps) was carried out in two stages: 1) Limitation maps are overlaid using the Boolean Operation where input maps can be integrated by using logical operators such as AND, OR, XOR and NOT (Bonham Carter and G.F., 1991). In this research logical 'AND' operator was used, which resulted in the selection of areas that have 'one' value in all limitation maps. 2) Factor maps are integrated with the index overlay method using following Equation: Where: Wi= The weight of ith factor map Sij= The ith spatial class weight of jth factor map S= The spatial unit value in output map It is resulted in a map with values for every location showing different suitability of locations for power plant construction. It should be mentioned that the result of index overlay is multiplied by the result of limitation maps overlay. The final integrated map is presented in figure 3.  Figure 3. Final integrated map for power plant construction 6. Conclusion and discussion Although such methods have been used in many GIS projects, the finalization of this work has shown the following results:
The authors would like to thank Iran Power Development Company for its financial support on this project. References
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