Assessing the Construction ofCharging Stations for Electric Buses:A Case Study for Stockholm InnerCity
Abstract: Electro-mobility has gained momentum within public transport in an effort to improve its sustainability. Sweden is one of the leaders in the field, with several ongoing electric bus demonstration projects and many research projects analyzing efficient infrastructure placement. This thesis aims at taking placement analysis a step further, by analyzing at micro-scale two areas that could potentially be used for bus charging in central Stockholm, namely Odenplan and Slussen. These are two of the busiest transport hubs in the city and offer the possibility to analyze different charging environments. On the one hand, Odenplan is an open square where buses stop along their route, while Slussen combines along-the-route stops with a bus terminal, which operates as starting/ending point for several routes. This thesis is built around two base-cases. In the first case, several routes are electrified according to results from Xylia et al. (2017). The second case analyses the electrification of all routes operating at the selected locations. Maps, orthophotos, drawings and technical literature have been used to create solutions based on the position of current bus stops. Simultaneously, the timetables of bus routes passing through Odenplan and Slussen have been analyzed in order to find an efficient stop allocation to reduce the number of simultaneous bus arrivals at each stop. Consequently reducing the frequency of queues at each charger. The analysis shows that partial and full electrification of bus services at Odenplan and Slussen are possible. A maximum of 5 chargers would ensure electrifying all routes operating at Odenplan, while 3 chargers would be enough in a partial electrification scenario. Neither conductive, nor inductive technologies present major problems of installation at this location. The area of Slussen has been divided into two separate cases: Södermalmstorg and the new Slussen bus terminal. All routes operating at both locations could be electrified with 3 and 15 chargers respectively. Conductive chargers are the only possibility for the terminal due to the characteristics of inductive chargers and current schedules. Partial electrification could be achieved with 1 and 3 chargers respectively. For the case of the terminal it has been assumed that a 7 minute charge will be required prior to each departure and that the chargers will be operated by the principle of charger sharing, allowing several routes to use the same charger. Installing 15 chargers at the terminal in Slussen is a costly solution, therefore its feasibility is doubtful. However, fewer chargers may be needed if a blend of fuels is used to operate those routes. For example, biofuels could be used for longer distance routes, while electricity is used for shorter ones. Several changes would have to be implemented in order to make bus electrification in central Stockholm a reality. Connecting the chargers to the grid has been identified as the main issue halting the construction of the charging infrastructure. Due to the lack of available substation capacity, new substations and expensive long-distance connections to the closest grid connection points are required. Consequently, alternatives to reduce the connection cost such as connecting the chargers to closer substations used by the subway or commuter trains should be explored for all locations. Operators would have to optimize timetables to avoid having simultaneously several buses waiting to charge at the same charger in locations like Odenplan or Södermalmstorg. The current body of legislation will also have to be improved to regulate electric bus operations and their infrastructure, as these are not properly addressed. For instance, nowadays buses must be empty while charging, making along-the-route charging and the possibility of using Odenplan and Södermalmstorg for charging unviable. Similarly, agreements between stakeholders regarding ownership and cost sharing should be in place, in order to set the ground rules for the expansion of electric bus operations in Stockholm. An efficient infrastructure placement is key for the expansion of electric buses and to foster it a location analysis framework has been created based on the findings arising from the analysis of Odenplan and Slussen. This framework will facilitate decision-making during the location assessment stage of electrification feasibility studies by providing step-by-step guidance through the spatial and operational analysis. This framework could be used for other locations in Stockholm or other cities, provided that the necessary adaptations are made in order to address local characteristics.
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