Design and Sizing of Electric Bus Flash Charger Based on a Flywheel Energy Storage System: A Case Study

Abstract

At present, the trend of all sectors and industries, especially the oil and gas industry, is towards reducing carbon dioxide emissions. Along with the modernization of technological processes, special attention has been paid to the reduction in greenhouse gas emissions from vehicles that run on gasoline and diesel. An effective solution in this field is the transition from vehicles with combustion engines to electric vehicles, similar to the use of the electric bus in public transportation. How to charge these electric buses is a challenge for researchers. By proposing a flash charging method for electric buses, the feasibility of using these buses is obtained. Due to the pulsating nature of the power demand in this charging method, the prevention of negative effects on the network by this type of load should be considered. These negative effects can include power quality problems, voltage drop, frequency instability, and overload of transmission lines and transformers. This paper presents a flywheel energy storage system (FESS)-based flash charging station for electric buses. The specifications of the components of this charging station are designed and sized for a case study for line 1 of Tehran Bus Rapid Transit (BRT). A charging strategy based on the proposed charging cycle is presented to minimize the high-power short-duration demand from the grid. The energy consumption of the electric bus based on the electricity consumption model is calculated. Based on theoretical calculations, for the case study, there is a need for installing 12 flash charging stations based on FESS in line 1 Tehran BRT. In this line, an electric bus with a battery capacity of 80 kWh is proposed. The power and energy capacity of these charging stations are sized to 600 kW and 3.334 kWh, respectively. Additionally, an economic comparison regarding the proposed charging station is conducted. The theoretical results of the design and sizing of the proposed charging station are validated based on simulation and experimental results for a small-scale laboratory setup.