Data Integration Using Fuzzy Logic Model Application in: Power-Plant Sitting


M. Sadi Mesgari
M. Sadi Mesgari
No 1364, Mirdamad Cross
Valiasr St, Tehran, Iran
Post Code: 19967-15433
Tel: +98 21 8878 6212, 8877 0218
Fax: +98 21 8878 6213
mesgari@kntu.ac.ir

M. Javad Valadan Zoej
M. Javad Valadan Zoej

Valiasr St, Tehran, Iran
Post Code: 19967-15433
Tel: +98 21 8878 6212, 8877 0218
Fax: +98 21 8878 6213
valadanzouj@kntu.ac.ir

Mohammad Karimi

Valiasr St, Tehran, Iran
Post Code: 19967-15433
Tel: +98 21 8878 6212, 8877 0218
Fax: +98 21 8878 6213
mkarimi@kntu.ac.ir

Sara Beheshtifar
Sara Beheshtifar

Valiasr St, Tehran, Iran
Post Code: 19967-15433
Tel: +98 21 8878 6212, 8877 0218
Fax: +98 21 8878 6213
sara_beheshtifar@yahoo.com

Abstract
Because of the population growth, urbanization and development of industrial and agricultural sections, the electric power demand is increasing continuously. Therefore, it is necessary to expand the power system for supplying reliable electrical energy. 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, cost of power generation and transmission (loss of energy). It also affects the whole environment and socio-economical development of an area.

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 local communities.

GIS along with appropriate models and spatial analysis method can be used to define the suitability of different locations for the construction of power plants.

In this paper, the required conditions for the establishment of thermal power plants are comprehensively studied. Then, important parameters in power plant sitting have been identified. Later data sets are integrated using different fuzzy operators.

Finally the suitable locations for the construction of the power plant using GIS spatial analysis capabilities are selected.

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.

In this study, important factors in power plant sitting have been identified and data sets related to these factors have been collected from different sources. Then according to the essence and characteristics of factors and their effect on power plant sitting, two different types of maps were generated: binary and fuzzy maps. These maps are integrated using Boolean and fuzzy operators, respectively.

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 includes most of the factors that should be studied and considered in selection of proper sites for power plant construction:
  • Transportation network: Easy and enough access to transportation network is required in both power plant construction and operation periods.
  • Gas pipe network: Vicinity to the gas pipes reduces the required expenses.
  • Power transmission network: To transfer the generated electricity to the consumers, the plant should be connected to electrical transmission system. Therefore the nearness to the electric network can play a roll.
  • Geology and soil type: The power plant should be built in an area with soil and rock layers that could stand the weight and vibrations of the power plant.
  • Earthquake and geological faults: Even weak and small earthquakes can damage many parts of a power plant intensively. Therefore the site should be away enough from the faults and previous earthquake areas.
  • Topography: It is proved that high elevation has a negative effect on production efficiency of gas turbines. In addition, changing of a sloping area into a flat site for the construction of the power plant needs extra budget. Therefore, the parameters of elevation and slope should be considered.
  • Rivers and floodways: obviously, the power plant should have a reasonable distance from permanent and seasonal rivers and floodways.
  • Water resources: For the construction and operating of power plant different volumes of water are required. This could be supplied from either rivers or underground water resources. Therefore having enough water supplies in defined vicinity can be a factor in the selection of the site.
  • Environmental resources: Operation of a power plant has important impacts on environment. Therefore, priority will be given to the locations that are far enough from national parks, wildlife, protected areas, etc.
  • Population centers: For the same reasons as above, the site should have an enough distance from population centers.
  • Need for power: In general, the site should be near the areas that there is more need for generation capacity, to decrease the amount of power loss and transmission expenses.
  • Land cover: Some land cover types such as forests, orchard, agricultural land, pasture are sensitive to the pollutions caused by a power plant. The effect of the power plant on such land cover types surrounding it should be counted for.
  • Distance from airports: Usually, a power plant has high towers and chimneys and large volumes of gas. Consequently for security reasons, they should be away from airports.
  • Archeological and historical sites: Usually historical building … are fragile and at same time very valuable. Therefore the vibration caused by power plant can damage them, and a defined distance should be considered.
  • Area size: Before any other consideration, the minimum area size required for the construction of power plant should be defined.
3. Study area and data sets
The study area is Fars province, in the southern part of Iran with an area of 122780 Kmē. Considering the available spatial data in the country, the data layers of scale 1:250,000 were used in this project. Table 1 illustrates several data layers which have been used in this study.

Table1: data layers used in this study


4. Maps Generation and Data integration
Considering the mentioned layers, according to the characteristics of factors and their effect on power plant sitting, two different types of maps were generated: binary and fuzzy maps. These maps are integrated using Boolean and fuzzy operators, respectively.

4.1 Binary maps
Such a map defines the area that cannot be used for the power plant because of a limiting factor. In a binary map, 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 areas with slope bigger than 10% are represented with zero value (not-suitable) and the areas with slope less than 10% are represented with value one (suitable). The list and criteria for generation of such maps is presented in Table2.

Table 2: Limitation maps and their criteria


These binary 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 binary maps.

4.2 Fuzzy Factor maps
Some of the parameters do not affect the suitability of a location in an 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 represented by giving them appropriate fuzzy membership values. Fuzzy membership values should be between zero and one. However, in this range, there is no limitation on the selection of the values. They are selected to represent the degree of membership in a set on the basis of subjective judgment.

In this study, factor weights are defined to describe their significance in the selection of proper location for gas power plants. These factors and their impotency are listed in Table 3.

Table3: Factors of fuzzy maps and their relative importance


Membership values in a fuzzy map represent both the relative importance of the factors and the relative values corresponding to different locations on the map area. For example, in gas pipe line factor map, membership values are decreasing when the distance from existing gas pipe lines is increased. In fact, each membership value represents the suitability of the pixel area for the power station regarding to the related criteria. In this research, all fuzzy membership values are between 0.1 and 0.9.

For factor maps integration, some fuzzy operators, such as the fuzzy AND, the fuzzy OR, fuzzy algebraic product, fuzzy algebraic sum and fuzzy gamma operator can be used. These operators are as follows:


Usually one sole fuzzy operator can not be used to integrate all data layers. Different fuzzy operators provide a high level of flexibility in data integration. The selection of operator is on the basis of the characteristics of the data layers and their role in the application. Therefore, before the integration of data layers, they are classified on the basis of their role in power plant sitting (See Table 4).

Table4: Classification of data layers for integration


When using 'fuzzy AND' and 'fuzzy OR' operator, only one of the parameters (factor layers) is used to define the output value, which is contrary to our intention of using all factors. Except for water resources, in other cases the operator of 'SUM' and '?' are used. In this study, assuming that just one water resource is enough for water supply, the maps of lake, river and water discharge were combined using OR operator.

Using of 'SUM' and '?>0.7' has an increasing effect on the results such that the resulted value is larger or equal to maximum value of the input values. Here for integrating of elevation, slope, geology and land use maps fuzzy gamma operator was applied (?=0.88). Also the maps of pipeline and road were integrated using gamma operator (?=0.7). At last fuzzy Algebraic Sum operator was used for final combination of fuzzy data layers. The selection of 'SUM' and '?' operators are such that a defined ratio is resulted among the factors of Consumption Center, Water Resources, Geophysical & land use and Infrastructure, on the basis of their characteristics and role in site selection.

5. Selection of suitable locations
Finally, the resulted maps of Boolean and fuzzy approaches were integrated. Then the resulted map was reclassified and 0.17% of the Fars province was selected as suitable area which covers about 208 Kmē (fig.1). The majority of suitable area was located in Fasa district, where electrical energy demand is more than other places.


Fig1. Suitable locations for power plant construction


6. Conclusion
The purpose of this study was to use fuzzy integration operators to integrate the data layers in GIS for power plant sitting. Binary maps and Boolean operators were utilized to identify limited areas for power plant construction and 71% of the county fell in this limited area. Factor maps and fuzzy operators were applied to determine suitable locations for power plant building in the remaining area. In general 0.17% of the study area was selected as suitable. Flexibility of the fuzzy method allows the user to apply a variety of data integration methods based on the characteristics of the data parts and the way they effect (support or decline) each other regarding the application. The major limitation of this study was the shortage of proper data layers relevant to power plant sitting.

References