Mobility2Grid Workshop @ Kyoto, May 8th 2024

The depot and charging facility location problem forelectrifying urban bus services
Yu-Ting Hsu / National Taiwan University
Shangyao Yan, Powei Huang / National Central University

BackgroundTo transition from diesel-consuming buses toelectric ones
 Fostering sustainable development with environment-

friendlier public transport

 Targeting zero emissions
 Containing air pollutants(particularly PM 2.5)

 Advances in electricity

storage and battery technologies
2Location problem of deploying
diesel-consuming bus services
Basic concerns in practice Perspective of bus operators: operating cost andefficiency- Bus operation (fleet size, route assignment, deadhead
mileage…)- Infrastructure construction and maintenance (depotcapacity and land acquisition…)

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Location problem of deploying
diesel-consuming bus services
Basic concerns in practice Perspective of social welfare- Service level- Alleviating traffic congestion- Environmental impact- Accessibility and equity-4

Transition to electric bus services
Additional issues
 Fleet size and mixture of diesel-consuming and electricbuses Deployment of charging stations- slow-recharging, fast-recharging, and battery exchange
stations- power tracks Single charge range / range anxiety

Fundamental considerations: cost-benefit analysis
over the life cycle

5Strategic planning
Considering both planning and operational perspectives(where system deployment cost over the planninghorizon is converted into net present value)

To determine deployment strategies that minimize lifecycle operating cost6

Formulation
Objective function:
Deadhead mileage

Establishing
maintenance stations
Decision variables:

Establishingchargers

Establishing andoperating depots

Rentingexternal buses- Whether to establish depots, maintenance stations, chargers,
and the associated capacities- Route assignments (over multi-size and multiple fuel types)- Whether to rent external buses- Whether to close and sell off the land of existing depots

Selling off
existing depots
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Formulation
Constraints:

Required number of buses for route assignments

Capacities of depots,maintenance stations,and chargers

8Formulation
Constraints:

Requirement on the number of electric buses
and associated route assignments

Binary and non-negative integer values of decision variables

9Solution algorithm (for the NP-hard problem)
Two-stage heuristic
Stage 1

Stage 2Relaxing integer constraints(route assignments)

Fixing the locations of depots
and charging facilities (from S1)

Solving the location problem

Solving the bus allocation
problem

Deriving the locations of depots
and charging facilities

Deriving the allocation ofvehicles

Hsu, Y. T., Yan, S., & Huang, P. (2021). The depot and charging facility location problem for electrifying
urban bus services. Transportation Research Part D: Transport and Environment, 100, 103053.

Case study in Taoyuan, Taiwan

Existing depots(red circles,d1-d10)

Candidate depots(blue circles,d11-d20)

over 218 routes where 10routes are required to be
100% served by electric11buses

Case study in Taoyuan, Taiwan

12Operating cost (USD/km) Large-sized

Findings

Medium-sized

Diesel-consuming buses

0.756

0.529

Electric buses

1.404

0.907

Approximate linear increase in total operating cost withthe required level of electrification
Total operating cost over(USD) required number of routes to be fully served by electric buses

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Findings
A larger fleet size enables more robust and flexible operation(and lower needs for external buses)

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Findings
 Sensitivity analysis on VMT cost

- Decreasing VMT cost longer deadhead mileage (deploying depots insuburban areas) Sensitivity analysis on capacities of new depots- Improved operational efficiency by replacing largersized depots with smaller ones
 Sensitivity analysis on costs of establishing andoperating new depots- Moving depots from downtowns to suburban areas toattain better urban development
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Issues to be further explored

Demand and land-use pattern modelingSubsidy and financial analysis



Mixed fleet with hybrid vehicles



Scheduling of bus operation and charging

Integrated model of electric bus system deployment andpower grid designComprehensive analysis of economic benefits(Wiki)

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Into the real world: some facts about Taiwan
Population: 23.4 million
 No. passenger cars: 8.6 million
 No. motorcycles: 14.5 million
17Into the real world
Progress in Taipei: 2018  2023 (650 electric buses, 19%)
 2030 (100% electric buses)

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Into the real world
Electric bus: 11 million TWD (~370 thousand USD)
Diesel-consuming bus: 4.5 million TWD (~150 thousand USD)
Subsidy up to 120+100 thousand USD
over 8 year

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Into the real world20

Into the real world21Some concluding remarks


Motivation for bus operators to join electrification: subsidy
and financial planning based on transparent cost structure

Sophisticated problem contexts depending on transit andenergy markets: needing to be supported by reliableridership and electricity supplyHolistic and robust policy-making that coordinates
perspectives of different stakeholders and against
development variability

Monitoring and data management platform to better
understand the market and operational characteristics ofelectric bus systems
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Mobility2Grid Workshop@ Kyoto, May 8th 2024

Thanks for listening & Questions are welcome!
Yu-Ting Hsu / National Taiwan University yutinghsu@ntu.edu.tw
Shangyao Yan, Powei Huang / National Central University