Mobility System
Joint Research Chair

Framework for Considering Electrification of Bus Routes:
Demonstration Experiment Using Osaka University
Inter-Campus Shuttle Bus*
7 May 2024
Katsuya Sakai
Mobility System Joint Research Chair,
Graduate School of Eng., Osaka University*Katsuya Sakai and Yutaka Ota, IEEJ Journal of Industry Applications, 144(7), July 2024 (in Japanese)1

e-Mobility Digital Twin by Osaka University
Transportation Layer

Mobility System
Joint Research Chair

EV Dynamics(Stay/Move/Charge)

Future Scenarios(Population/Stocks)(Carbon Neutrality Target)
V2X

Stationary Infrastructure(Electric Power/Road Network)(House/Building/Chargers)

Prof. Ota
Urban Layer

V2XCharging
Infrastructure
Desin

Flow Data(People/Logistics/Vehicle)(Climate/Power & Energy)

Power System Layer

Regional Power &Energy Balancing

Assoc. Prof.
Yoshizawa

Data-driven, Stock and Flow estimated, Geographic Simulation Platform[Y.Ota, S.Yoshizawa, K.Sakai, Y.Ueda, M.Takashima, K.Kagawa, and A.Iwata, "e-Mobility and Energy
Coupled Simulation for Designing Carbon Neutral Cities and Communities", IATSS Research (2023/6)]

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Osaka University Inter-campus Shuttle Bus

Mobility System
Joint Research Chair

Out-bound• Osaka University has threecampuses.
• 80 bus services are operated everyschool day.
• From October 2021, an electricbus was introduced.
• We have conducteddemonstration experiment ofconsidering electrification of busroutes.

Dec. 22, 2020 created

Bus #Toyonaka

MinohConvention
Dept. of Eng.
Bus #Toyonaka
MinohConvention
Dept. of Eng.

In-boundBus #Dept. of Eng.
Human Sci.
Minoh
Toyonaka
Bus #Dept. of Eng.
Human Sci.
Minoh

Toyonaka

Electric Bus

Depot Dept.

Depot Arr.

Suita
Dept. of Engineering

MinohConvention
CenterSchool of
Human Sciences

Toyonaka

Senri Depot:
Office & Charger
Bus Routes―― Toyonaka-Minoh-Suita

3ObjectivesMobility System
Joint Research Chair• To understand electric bus power consumption and its fluctuation factors• To construct framework to consider electrification of bus routes• We examine the possibility of the bus routes electrification in terms of:(1) Driving range(2) Charging schedule at bus depot

BYD K8GPS logger installed at bus front

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Kinematic Model to Estimate Power

Mobility System
Joint Research Chair

GPS Trajectory Data

Temperature Data
𝟏
𝑷𝑬𝑽 = 𝜼𝒗(𝒎𝒈𝒔𝒊𝒏𝜽 + 𝒎𝒈𝑪𝒓 𝒄𝒐𝒔𝜽 + 𝝆𝒗𝟐 𝑨𝑪𝒅 + 𝒎𝒂)+ 𝑷𝒂𝒖𝒙 + 𝑷𝒂𝒊𝒓𝟐
η: drive system efficiency, v: speed, a: acceleration, θ: slope angle, m: vehicle weight, Cr: rolling resistance coefficient,
ρ: air density, A: vehicle front area, Cd: air resistance coefficient, Paux: auxiliary power, Pair: air conditioning power5Model Parameters and Output Example

Mobility SystemJoint Research Chair

141210Pair [kW]Average power consumption

η=0.95
Cr=0.015
Cd=0.7
Paux=600 [W]
A=2.5×3.36=8.4 m2
m=11850+55*30=13,500 kg

86420-50510 15 20 25 30 35

Maximum temperature in a day Th [℃]

𝑃𝑎𝑖𝑟 = 𝑚𝑎𝑥 −0.63𝑇ℎ + 11.03, 0, 0.36𝑇ℎ − 8.34

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Estimated vs Actual Energy Consumption a Day

Mobility System
Joint Research Chair

Daily power consumption [kWh]200180160140120100806040200

airrolling

grade

inertia

cooling

auxiliary

actual7

To improve model accuracy...

AC/DC Load Current

Mobility System
Joint Research Chair

AC/DC AUTO-ZERO CURRENT SENSOR
Connection Image• Current loggers installed to measure air conditioning
energy and total energy consumption• Heating power on/off behavior could be observed.
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Improved Model

Mobility System
Joint Research ChairDrive system efficiency:
Powerηp=0.95
Regeneration ηr=0.85

Air conditioning:
Heating Pair=7kw-300W/℃
Cooling Pair=200W/℃

9Electric Bus Charging Management Model
Input Data

Estimation Model

GPSTrajectory

Driving Power
Consumption

Temperature

Air Conditioning
Power Consumption

Mobility System
Joint Research Chair

Electric Bus Daily
Power Consumption

Output Data
OfficeElectricity
Contract andEquipment
Chargers
number andspecs

Office Power Demand
Including Electric Bus
Charging Power

Office Power Demand
Valley Filling Algorithm:

Electric bus charging power isdetermined as the maximum within
the contracted power availability.

Charging power:
50 kW10

Energy Consumption & Charging Simulation

Mobility System
Joint Research Chair• Two buses aresimulated for twodays.
• Contract power is
90 kW.
• Two buses charge isfinished at 5am.

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Energy Consumption & Charging Simulation

Mobility System
Joint Research Chair• Case study withassuming all fivebuses are electrified.
• Contract power is
160 kW.
• All buses charge isfinished at 6am.

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Summary

Mobility System
Joint Research Chair• Power consumption estimation simulation• Estimating power consumption/regeneration by each factor(rolling/air/ascending/acceleration/auxiliary/cooling/heating)from GPS trajectory data and temperature data

• Simulation of energy management at an e-bus depot• Simulation of charge/discharge connected from power
consumption estimation simulation

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SummaryMobility System
Joint Research Chair• Practical steps to consider electrification of bus routes are:(1) Installing a GPS sensor on a current bus and driving it toestimate the power consumption of the running and auxiliary parts(2) Collecting data on seasonal temperature forecasts(3) Simulating change in SOC and estimating the risk of electricity
shortage in advance to install electric bus.

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