Sustainable mixed urban transit system with electric and conventional buses

With the increase of renewable energy sources, the battery-electric bus seems like a well-suited technology for sustainable urban transit system because it has high energy efficiency. The successful deployment of battery electric vehicles could reduce oil dependence, improve urban air quality, and reduce greenhouse gas emissions. Therefore, conventional buses are likely to be continuously replaced by electric buses. However, the limitations of electric buses, such as range limitations, battery capacity loss, and required charging times of battery, are critical issues for the service quality of the urban transit system. Therefore, it is more realistic to develop a sustainable urban transit system mixed with conventional and electric buses. The goal of this project is to provide a system-level solution for the transition process from conventional to electric bus system considering the service quality, economy, and environmental benefit. This will minimize the side effect caused by bus electrification. At the same time, by optimizing the market penetration and usage of electric buses in the public transit system, this project will try to optimize the economic and environmental benefits. Based on data collected from real-world buses operated in China and Norway, a battery-electric bus energy consumption model is developed for strategic purposes considering limited input requirements, such as route information, bus characteristic, outside temperature, and estimated passenger flow. In terms of auxiliary use, we see that the HVAC energy consumption can be a significant share of the total energy consumption. This demonstrates potential in energy savings through reducing the amount of air exchange through fewer and shorter door openings, or investing in technology for reducing heat transfer when doors open. Moreover, by investigating the impact of battery degradation mechanism, we find out that battery lifespan can be extended by up to 3 years and the lifecycle cost of electric bus fleet can reduce 24.7% through keeping the state of battery charge within a low and narrow range. Additionally, we develop a collaborative optimization model for the lifecycle cost of BEB system, considering both overnight and opportunity charging methods. This model aims to jointly optimize the initial capital cost and use-phase operating cost by synchronously planning the infrastructure procurement and fleet scheduling. The results indicate that the proposed optimization model can help to reduce the lifecycle cost by 7.77% and 6.64% for overnight and opportunity charging systems, respectively, compared to the conventional management strategy. Considering local weather and operation characteristics, the lifecycle environmental and economical performance of electric buses are evaluated. The result shows that the public transportation system with both hybrid and electric buses can be good compensation between financial and environmental needs instead of using electric buses to replace all the conventional buses.

First of all, the project has been conducted in three countries. The energy consumption data was collected from several different places and help electric vehicle manufacturers and operators to provide better service and suitable technologies according to the local condition. Second, the energy consumption has been applied by global researchers to better estimate the real world situation of the public transit system. Third, the solution provided by this project helps the government to develop a proper policy to improve the electrification process of the public transit system. Fourth, this project provides a system-level solution for public transit system operation companies to maximize economic benefits in terms of purchase strategy, electric bus usage, and charging infrastructure usage. Fifth, taking the long-term view, this project also maximizes the environmental benefits considering the service quality. Moreover, this project has involved a number of master's students, PhD students, and Postdoc fellows. This project has contributed to different educational programs. It significantly increased the virtual mobility between Chinese, Norwegian and Swedish partners.

Battery electric buses are seen as a well-suited technology for sustainable urban transit system because it has high energy efficiency and generates zero tailpipe emissions. Therefore, conventional buses are likely to be continuously replaced by electric buses. However, the limitations of electric buses, such as range limitations, battery capacity loss and required charging times of battery, are critical issues for the service quality of the urban transit system. Therefore, it is more realistic to develop a sustainable urban transit system mixed with conventional and electric buses in a transitional period until the limitations of electric buses are overcome. The goal of this project is to provide a system-level solution for the transition process from conventional to electric bus system considering the service quality, circular economy, and environmental benefit. Based on observed data, energy consumption and charging behavior models of electric buses will be developed considering different traffic state, weather and travel demand. Moreover, a feasibility analysis will be conducted for the bus transit system to develop a proper replacement plan. According to the feasibility analysis result, a repurposing-plan will be developed for batteries, vehicles, and equipment. Consequently, a charging infrastructure placement plan will be developed to satisfy the charging demand of electric buses. Moreover, the proper scheduling and dispatching strategies will be developed for the sustainable mixed urban transit system to maintain highly reliable schedule and achieve optimal environmental benefit.