Optimal operating strategy of short turning lines for the battery electric bus system

Operating short turning line is an efficient strategy to satisfy the unevenly distributed demand during peak periods while reducing operational cost.However,for the battery electric bus(BEB)system,the application of the strategy is challenging due to the disadvantages of BEBs,such as limited driving mileage and long charging time.Improper vehicle configuration and charging scheduling may dramatically increase the operational cost and cut the benefits of these strategies.In this work,we propose a general framework to design an effective short turning strategy for the BEB system at a tactical planning level.First,the trade-off relationship between the battery capacity and the average trip time is identified by modeling the BEBs operations.Second,a microeconomic model is formulated to jointly optimize the frequencies and charging schedules of the whole bus line and the short turning line,to effectively minimize passengers’waiting time and operational cost.Finally,numerical experiments have been carried out for an illustrative linear line to demonstrate the potential benefits of the sub-line operating strategy compared with the normal operation.

Battery electric buses charging schedule optimization considering time-of-use electricity price

Purpose–This paper aims to optimize the charging schedule for battery electric buses(BEBs)to minimize the charging cost considering the time-ofuse electricity price.Design/methodology/approach–The BEBs charging schedule optimization problem is formulated as a mixed-integer linear programming model.The objective is to minimize the total charging cost of the BEB fleet.The charge decision of each BEB at the end of each trip is to be determined.Two types of constraints are adopted to ensure that the charging schedule meets the operational requirements of the BEB fleet and that the number of charging piles can meet the demand of the charging schedule.Findings–This paper conducts numerical cases to validate the effect of the proposed model based on the actual timetable and charging data of a bus line.The results show that the total charge cost with the optimized charging schedule is 15.56%lower than the actual total charge cost under given conditions.The results also suggest that increasing the number of charging piles can reduce the charging cost to some extent,which can provide a reference for planning the number of charging piles.Originality/value–Considering time-of-use electricity price in the BEBs charging schedule will not only reduce the operation cost of electric transit but also make the best use of electricity resources.

A bi-level optimization framework for charging station design problem considering heterogeneous charging modes

Purpose–The purpose of this paper is to optimize the design of charging station deployed at the terminal station for electric transit,with explicit consideration of heterogenous charging modes.Design/methodology/approach–The authors proposed a bi-level model to optimize the decision-making at both tactical and operational levels simultaneously.Specifically,at the operational level(i.e.lower level),the service schedule and recharging plan of electric buses are optimized under specific design of charging station.The objective of lower-level model is to minimize total daily operational cost.This model is solved by a tailored column generation-based heuristic algorithm.At the tactical level(i.e.upper level),the design of charging station is optimized based upon the results obtained at the lower level.A tabu search algorithm is proposed subsequently to solve the upper-level model.Findings–This study conducted numerical cases to validate the applicability of the proposed model.Some managerial insights stemmed from numerical case studies are revealed and discussed,which can help transit agencies design charging station scientifically.Originality/value–The joint consideration of heterogeneous charging modes in charging station would further lower the operational cost of electric transit and speed up the market penetration of battery electric buses.