SET2011, 10 th International Conference on Sustainable Energy Technologies, İstanbul, TÜRKİYE, 4-7 Sep. 2011 1 A COMPARISON OF METROBUS SYSTEM AND TROLLEYBUS SYSTEM CONSIDERING ENERGY COSTS AND CO 2 EMISSION: A CASE STUDY FOR ISTANBUL R. Ayaz 1 *, İ. Nakir, A. Durusu, H. Akca, M. Tanrioven 1 Yildiz Technical University, Electrical & Electronic Faculty, İstanbul Abstract Recently, alternative energy based vehicles have drawn the attention of engineers specifically on the production of fully electric powered vehicles due to increased environmental awareness and fuel cost. As a result of difficulties in commercializing the vehicles, electric powered cars find an application area in public transportation. One of the solutions for public transportation is to use trolleybus system. This paper gives a comparison of Trolleybus system and existing Metrobus system in Istanbul, Turkey in terms of energy costs and CO 2 emissions. The simulation results show that using Trolleybus system instead of Metrobus is much more economical based on the current prices. As for the emissions, the amount of CO 2 for city centers and overall environment is evaluated. Keywords: Metrobus, Trolleybus, Energy cost, CO 2 Emission 1. Introduction CO 2 emissions, which are harmful to human health and the environment, are released out of fossil fuel based internal combustion engines (ICE). Most of the public transportation system which also uses ICE is a major contributor to urban traffic. The use of fossil fuels as an energy source in public transportation increases CO 2 emissions significantly. The demand for electric vehicles (EV) is increasing every day because of these harmful emissions and decreasing fossil fuels. Using the applications of electric vehicle systems in the urban traffic is an effective way to minimize the CO 2 emissions in city centers. Therefore, it is a good thing to have the electrically powered public transportation system. In the literature, the emissions from ICE based vehicles and electric vehicles are discussed in many studies. These studies have shown that electric vehicles produce less CO 2 emissions. For example, a study by National Defense Council reported that 49-66% CO 2 emissions decreased in case of electric vehicles use in Southern California, where the majority of electrical generation are obtained from natural gas and 21% of the electricity from coal only [1]. The Electric Power Research Institute has performed a study for U.S. Department of Energy. This study has shown that 22-87% CO 2 emissions decreased depending on EV efficiency, geographical location and source of the electric power [1]. The other study have indicated that according to the 3D simulation, 4400 ton/day CO 2 emissions are decreased in case of super energy-efficient electric vehicle use instead of diesel vehicle in Tokyo [2]. This paper gives a comparison of Trolleybus system and existing Metrobus system in Istanbul, Turkey in terms of energy costs and CO 2 emissions. 2. Background and Notations Environmentally-conscious vehicle technology has developed because of increasing oil prices and harmful components of fossil energy sources. Current vehicle technologies can be listed as ICE, hybrid and fully electric vehicle. Nowadays, one of the usage areas of fully electric vehicles is public transportation systems. One of the fully electric vehicles that are used in public transportation is Trolleybus. Trolleybuses are vehicles that works just like electric trams with rubber wheel, drawing its power from overhead cables along its way. The difference of this system from electric tram is the use of rubber wheels rather than rail system; so feeding by two cables instead one [3]. *E-mail: ayaz@yildiz.edu.tr