Charging infrastructure forelectric city buses : An analysis of grid impact and costs

Sammanfattning: An increased demand for fossil free transport have led to developments in the area of electric vehicles. Many companies and organizations are carrying out projects where electric city buses are tested in normal operation, and the result suggests that this can be an option with big potential. This thesis is carried out at Scania CV AB. The aim is to investigate the total investment cost for society when electrifying a complete bus system. It focuses on grid connections for the chargers, but battery costs and charger costs are also included. To achieve this, a case study of Stockholm is carried out. In the case study, the bus system of Stockholm is investigated, and from this three different scenarios are created with three different charging strategies. The first scenario includes only charging at the depots, when the bus is parked over the night. The second scenario uses end station charging combined with depot charging during the night. From these strategies, requirements for the batteries and the charging powers are set. The third scenario, on the other hand, starts from a battery available today. From these specifications, a charging strategy that includes end stations charging, depot charging as well as charging at selected bus stations is chosen in order to cover the demands of the bus system. For the three strategies, the possibilities to connect the chargers to the electric grid are investigated using data from the distribution grid owner in Stockholm, Ellevio AB. From this, conclusions regarding the available capacity and required extensions are made, and the costs is investigated. Also, a comparison case study for the small city Mora in Sweden is carried out, and a short discussion regarding possibilities in a larger European city is included. The result shows that is probably most profitable to charge during the day, at end stations and selected bus stations, combined with depot charging. The grid connection cost is a significant part of the total costs, and should not be neglected. On the other hand, the total cost is relatively small, and electrification is considered possible within a short future.  Except for the costs included in this thesis, costs related to projecting of the system as well as permitting for the new substations should be included. A deeper analysis of the possibilities to build new substations within the city region need to be carried out, as well as an analysis of the total cost of operation for the electrified system. This should then include the time parameter and the lifetime of the components.