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Optimization of CNG Station Locations in Intercity Networks
Mansour Hadji Hosseinlou1, Barmak Ebrahimzadeh2 1Assistant professor, K.N.Toosi University of technology, Tehran, Iran, E-mail:mansour@kntu.ac.ir 2Graduated Student, K.N.Toosi University of technology, Tehran, Iran. E-mail:mansour@kntu.ac.ir Abstract Nowadays with regard to decreasing known energy sources, societies are following strategies to exit from energy crisis. In Iran, changing the consumed fuel to the Compact Natural Gas (CNG) is the priority enforcement. This change needs some substructures. One of the most important substructures is the Compact Natural Gas (CNG) stations that regarding to excessive construction’s costs. They need suitable distribution in the transportation networks. In this paper, it is tried to locate stations with introducing effective parameters in locating these stations and contemplating the safety, traffic, land use and road demand by using fuzzy logics and ArcGIS software. Therefore Tehran – Semnan freeway was selected as a case study. Amount of fuel demands at 2021 was estimated and 22 CNG station was projected for supplying demands. Existing 3 CNG stations in this Freeway, 19 remainder CNG stations was located with using fuzzy systems and modeling member functions and sub criterions weight in ArcGIS. For preventing queue and delay time for users, it was recommended using 2 more dispensers in consumption pick hour. Optimization of CNG station locations in this network will cause the saving in energy and expenses, decreasing delay time and increasing road safety. 1. Introduction Transportation system as a largest section of gasoline and petrol consumer respectively with more than 94% and 55% of total country consumption, are the major user sections in Iran.[1,2] In recent years, growth of the energy consumption in this section had accelerating process and flourished. If the recent consumption of gasoline continues, our country will excluded of its gasoline export and even in near future will become change in to the importer of such product. According to the above, the policy of alternation the fuel in to the condensed natural gas in this section is essential. Policy of replacing fuel in transportation section is in need of infrastructures that constructing the natural gas fueling station is one of these policies.[3,4] Necessity of making a systematic process for locating of CNG stations is vital. Suitable locating of such stations has advantages such as fuel saving, reducing the delay time and increasing the roads security. Till now, locating of CNG stations had been an experimental process. In this paper, new system of CNG station locating is developed based on suitable parameters and modeling them in the fuzzy system and ArcGis software [5,6,7]. Tehran-Semnan road is studied as case study and required CNG stations will be estimated for 2021. 2. Case study location For practical definition of station locating, the need of using case-study is obligated. So the road of Tehran-Semnan is chosen as a case study. The reasons for choosing this road are described as follows: a. The road strategic situation: Tehran-Semnan freeway is a part of eastern-western corridor of the country which connected to the Tehran- Zanjan freeway from the west and Semnan-Mashhad from the east is forming an expanded transportation network. Also this road is a part of southern corridor of Asian land transportation infrastructure development b. Petrol consumption in two provinces of Tehran & Semnan: The Tehran-Semnan road is the most important connecting road of Tehran and Semnan provinces. These two provinces have the most per capita consumption of country petrol. Semnan province with annually consuming 292 million liter petrol and having population more than 589512 individuals and per capita consumption equal to 495 liter is the first rank of petrol consumption in the country. Also Tehran province with annually consuming 5641 million liter and population more than 12150742 individuals and per capita consumption of 464 liter has the second rank.[3,4] 3. Estimating fuel demand For determining the number of CNG stations in this road, the demand of fuel amount should be estimated. The basis year is supposed to be 2021 for forecasting CNG stations.[8] For estimating the fuel demand in the studied road, there should be use of machines measurement kilometer and fuel consumption average of different vehicles in the road network according to the following equation: 
4. Determining amount of required CNG stations According to the capacity of a standard fuelling station, the amount of required natural gas stations in this case study would be calculated as the equation 2. On the basis of the studies, the fuel capacity of a CNG natural gas station is equal to 21000 cubic meters in a day. 
5. Effective factors on CNG station locations As a result of existing differences on locating of fuelling stations there can be no distinguished method for determining and using parameters; so with library studies, general and complete data would collected about the nature of desired activity. On the basis of these data and also take consult with other experts in this field, the effective parameters are defined. The effective factors are divided to three categories of infrastructures facilities: land using, safety and infrastructure facilities.[ 9,10,11,12] 5.1. Infrastructures facilities The infrastructures facilities factor is including accessibility sub-criteria to the natural gas pip lines, electricity and telephone transmitting lines. The sub-criteria are surveyed as follows. a. Preparing natural gas: the most important factor for constructing CNG stations is accessibility of the gas pipelines. b. The telecommunication and electricity transmitting lines Most of the CNG station necessaries including compressors which work with electricity power and preparing electricity for such stations is one of the primitive necessaries. 5.2. Road safety The safety factor is one of the most important factors of station location in case that in non-secure situation and positions the constructing of stations is restrained. The subcriteria of such parameters are surveyed as follows. a. Distance from intersection, road arcs, and technical structures: the distance depend on length of queue which made in fuel stations and braking distance since drivers can stop when they see station. [12] b. Distance from big cities: the great cities of this road are: Tehran, Seman, Ivanaki and Garmsar which respectively are located in longitude of the road. CNG stations should be located in appropriate distances from the great cities. c. Distance from townships, residential and industrial region: these places can be seen in the longitude of the road. According to the fuel consumption demand of such places the CNG stations should be located near of these positions. 5-3. Land using For determination the suitable site, there is need of data from type of land application. According to this point of view about 4 types of application is determined which are as follows: a. Industrial using: which is included factories and Industrial Township and producing unites. b. Residential using: This sub-criterion is included villages, small towns, big cities, residential townships and suburbs. c. Agricultural using: which is included farms, gardens and land under cultivations. d. Pasture and plain: which is included lands with state ownership and arid. 6. Weighting the criteria and sub-criteria In this section, it’s endeavored that with suitable weighting for each sub-criterion; distinguish the role of parameters in station locating. Road safety and reducing the road accidents are the most important policies of road management system. In this case, the appropriate distances of predicted fuel stations from existing tolls including: intersections, technical buildings and appropriate distances from cities and population center are the important safety factors which can not be negligent because of high importance of safety in intercity traffics. Thus the weighting of road safety factors was not done, because of similar importance of all sub-criteria. But after weighting to other criteria in the basis of the expert’s knowledge and combination of related data, the suitable locations presented in the secure places as the final outcome way which is pointed in the future sections.[5] 7. Required data collection In this phase according to the effective factor which is defined in previous parts, the required information layers in the studied limit are collected from country topography organization. The scale of such topographies is 1:25000 and its format is *dwg. In the phase of data preparation, the capability of model analysis implementation of the proper uses would be done on these layers. Also the maps of total gas lines achieved from the Iran national gas Corporation and measured as a data layer. Each of them scaled as the same. 8. Location of CNG stations by applying ArcGIS software and Fuzzy logic The targets of locating process as a common analysis in GIS are preventing from wasting expenses and ensuring the maximum efficacy. The needed entrances of this process is prepared data layers from the studies area and a series of digit data for weighting of such layers and proper locating for making special activities which is outcome of entrance data combination.[6,7] In this paper, the CNG station locating is based on the mathematic and Fuzzy systems, thus with allocation the Fuzzy function to each effective factor in locating would be reached the optimum locating from combination such collections. [5] Existing parameters in locating mostly have fuzzy nature. The well-informed example of this issue is factors that are related to the suitable distances from some of existing complication. For these factors, the fuzzy series would be defined that any of pixels would have different membership degree according to its distance. If all issues parameters would define as a fuzzy series with correct membership digits, for parameter combination can use the right fuzzy operators. The type of used operators is also depending to the effectiveness of factors from each other or final affect of operator on the parameter series. The fuzzy model implementation in two phases of determining the membership function and combination the membership digits of this function would be done with use of fuzzy functions which are defined in follows. 8-1. Definition of parameters membership function The target of explanation the membership function for a factor, is continues and gradual weighting on that factor. In this case weight of each pixel would be reach according to the amount of membership function of that pixel in a suitable fuzzy series of desired factor. But according to the nature of each factor, the way of alternation the existing weights in the studied area and experts opinions is defined for each factor of Fuzzy membership function. For showing the membership function of each factor, it is used raster data Toolbar “Spatial Analyst” and the functions are brought in “Raster Calculation”. With entering the fellowship factors of each parameter in the program and exercising them, the program will show the series of points in the page with color spectrum that the value of each of its pixel shows the amount of that pixel fellowship in the parameter fellowship function. 8-2. Data layers weighting As mentioned later, some of the primitive data layers like the land application layers are in need of weighting that the calculated weight for each of these criteria would exercise on them. 8-3. Data layer combination with use of fuzzy functions In this stage the achieved layers from the previous parts would be combine according to the suitable fuzzy functions with each layer features in order to achieve the suitable final map as an output. For combination the safety sub-criteria and achieving the safety final fuzzy map, association function (Fuzzy And) is used; because in which cases that not including the sub-criteria and safety points, in the final Fuzzy map, would also not included those parts. The related layers to the infrastructures facilities sub-criteria are combined according to the table 1 weights; so the infrastructure facilities fuzzy map would be achieve. In the other stage, the land application layers and infrastructure facilities are combined according to the table 3 weights. Then the fuzzy map of land using and infrastructure facilities combination would be achieve. In the final stage, for achieving the suitable places of the stations, the fuzzy multiplication (Fuzzy Product) would be used. In that case, with multiplication the pixel weights of fuzzy map, the combination of land using and infrastructure facilities with corresponding pixels weight in safe places Fuzzy map, the final locating map would be achieve. Use of multiplication operator (Fuzzy Product) would be caused that the weights of secure places is zero or little would be zero or made less. Therefore the secure places would have more value to build. 8.4. Recommended CNG station sites According to the mentioned analysis, finally, recommended stations are presented in the table 1. In this table, 22 sites are recommended for constructing the CNG station and the positions of placing each of them are defined. In the last column of this table, the locating index of each site that is the output of combination of effective parameters with different weights and different operations can be observed. It’s clear that this index like the fuzzy function is varied from zero to one and whatever its value to be closed to the one shows that constructing this site is economical. If we want to construct the CNG stations according to the 5 years periods for 2011-2016 and with computing that natural gas will be replaced by 30% and 50% of transportation fuel, the amount of stations will be 6 and 13 stations respectively.  Table 1 : Characteristic of Fuzzy Model suggested site 9. Conclusions From this study, the following results can be drawn: 1. The consuming fuel of transportation system was studied and the amount of the fuel was estimated for the basis year. 2. The amount of required CNG fuelling stations of Tehran-Semnan road was determined according to the estimated fuel of 2021. 3. The effective factors on station locating studied. 4. The effective factors in station locating weights and depended suitable functions were allocated to each of sub-criteria according to the technical and economical studies and using fuzzy mathematics. 5. It has been used of ArcGIS software for locating CNG stations. 6. Finally the optimum station locations which had the locating index more than 85% explored as the suitable output for locating and 19 approximately station distinguished on the map. 7. Suitable locating of fuelling station would be result in saving resources and expenses, reduction of delay time and increasing of the security. References 1. BP Statistical Review of world Energy 2006, available at http://www.iangv.org/jaytech. 2. Statistic of energy & oil product consumption, oil products refining national Corporation of Iran, 2004. 3. Series of papers of the first CNG conference and gas burner vehicles- library of optimizing the fuel consumption organization, 2004. 4. Evaluation of CNG Fueling System, Energy commission of California, October 1999. 5. Mohammad teshneh, “Lab- fuzzy systems and fuzzy control”, 2001. 6. Mohammad Sadi Mesgari, “Learn GIS experimentally with use of Arc GIS software”, 1384. 7. Omid T T dejh, “ArcGIS self-though and basis concepts of GIS”,2006. 8. Zahra Aghakhani, “the estimating models of fuel demand in transportation section”, budgeting and programming magazine, No. 38, pages 101-128, 1999. 9. Daily and hour traffic reports of country roads, transportation and toll-house organization reports, 2006. 10. Highway Research Board, “ Highway Capacity Manual HCM”, 2000. 11. P.Roess William, R.Mc sllane, “Traffic Engineering”, 3rd edition, 2004. 12. C.Jotin Khesty, “Transportation Engineering an introduction”, 3rd edition, 2002
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