Configuration of Electric Vehicles for Specific Applications from a Holistic Perspective
2. Material and Methods
- Phase 1: For the given application, monitor the current operation of the fossil-fueled vehicles for a long period to determine their real driving patterns and operational conditions.
- Phase 2: Use the collected data to construct a representative real-world driving cycle.
- Phase 3: Use a multi-objective optimization and an iterative energy-based approach to determine the best electric vehicle’s powertrain configuration (number of batteries, motor size, and gearbox transmission ratio) for the given application.
2.1. Phase 1: Current Operation of the Case Study
2.2. Phase 2: Driving Cycle
2.3. Phase 3: The Multi-Objective Powertrain Optimization
- Minimizes the power required from the motor while maintaining the current operation with the purpose of reducing the initial cost of the brand-new vehicle.
- Minimizes energy consumption to minimize the operative cost.
- Minimizes the net well-to-wheel CO2 emissions generated per kilometer driven.
- Minimizes the total cost of ownership (TCO).
- Maximizes the acceleration capacity of the vehicle (i.e., less time to reach a given reference speed).
- Maximizes the top speed that the vehicle can reach. As long as the vehicle’s top speed satisfies the driving cycle maximum speed, this characteristic is irrelevant in defining the tailored powertrain for the specific application under consideration. However, high top speed increases the possibility of using the vehicle for eventual other applications. Furthermore, from the marketing point of view, vehicles with high top speed are preferred by drivers. Therefore, in this work, we kept this criterion in the optimization process with low relevance.
2.3.1. The First Loop of Optimization for Determining the Size of the Motor and Battery Pack
|: mass of the vehicle||: instant velocity of the vehicle|
|: resulting acceleration of the vehicle||: rolling coefficient|
|: drag coefficient||: gravity|
|: frontal area of the vehicle||: road grade|
2.3.2. The Second Loop of Multi-Objective Powertrain Optimization
CO2 Net Emissions
Total Cost of Ownership—TCO
- Initial investment costs: For electric buses, we considered the cost of the defined motor, transmission, battery pack, chassis with body and accessories, and a charging station; for diesel buses, we considered the cost of the current commercial vehicle.
- Operational costs: This includes the cost of diesel or electricity, corrective and preventive maintenance, insurance, battery-pack replacements, emissions penalties, and driver’s salary.
- Financial costs: This includes loans, financing interest rates, taxes, inflation, depreciation, and savage value after the expected lifespan of the vehicle.
Muti-Objective Optimization Varying the Transmission Ratios
3.1. The Current Vehicle Operation
3.2. Driving Cycle
3.3. Multi-Objective Powertrain Optimization
Conflicts of Interest
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|Drivetrain||Rear Wheel Drive|
|Engine type and fuel||4 cylinders inline, Intercooled Turbo Diesel EURO V|
|Gross vehicle weight (kg)||4100|
|Engine displacement (cm³)||2143|
|Engine rated power (kW)/(HP)||120 (163) @ 3800 RPM|
|Rated torque (Nm)||380 @ 2000 RPM|
|Transmission gearbox||ECO Gear 360 6-speed manual transmission|
|Spec. Energy |
|Motor Power Needed||TCO|
|Deep Cycle Lead Acid 1||Li-Ion 1||Na-NiCl2 2||Ni-MH 2||Lithium-Sulfur 2|
|Nominal Voltage [V]||12.00||3.6||289||288||305|
|Battery Energy [Wh]||1992||13||24,276||24,480||24,400|
|Specific Energy [Wh/kg]||183.88||1008||191.23||165.03||507.75|
|Price per unit [USD]||499.00||2.45||14,403||11,619||7238|
|Price per kWh [USD/kWh]||250.50||194.44||593.33||474.66||296.66|
|Assumptions Included in the TCO Calculation|
|Because the electric bus is intended to run under the same operating conditions (driving cycle) of the current diesel buses, the distance driven by the vehicle per year and driver’s salary will remain equal to the diesel counterpart.|
|A ten-year lifetime expectancy was considered for both the diesel and electric bus.|
|Penalties for vehicles that produce on-road emissions were not considered.|
|No government incentives for purchasing an electric vehicle were considered.|
|Insurance of the diesel bus is considered to be 25% lower than the electric counterpart.|
|One charging station investment is considered, and its annual maintenance cost.|
|The battery pack is replaced depending on the lifespan of the battery. One thousand cycles were considered for the lifespan of the batteries. When replaced, a 20% expected increase in prices with a 4% price inflation rate per year was included. A salvage value of 80% for the used batteries is considered with this strategy.|
|The vehicle (diesel and electric) is depreciated by 20% of its current value every year, resulting in a 13% salvage value after 10 years of lifespan.|
|80% of the initial investment cost is financed through a 5-year loan.|
|The tax rate of 30%, cost of debt of 3.27%, risk-free rate of 4.5%, and Equity Risk Premium (ERP) of 5% are considered.|
|The Net Present Value (NPV) was estimated with a discount rate of 9.22% based on a weighted average cost of capital (WACC) approach.|
|Parameter (Abbreviation)||SFC Scenario||Unit|
|Average Specific fuel consumption (SFC) 1||18.75||22.74||30.00||L/100 km|
|Average Kinetic Intensity (KI)||2.06||5.15||13.69||m−1|
|Average Vehicle Specific Power (VSP)||1.18||0.68||0.51||kW/ton|
|Number of accelerations per km (accel/km)||15.87||21.87||22.74||1/km|
|Cruising percentage (% cruising)||26.76||23.57||16.22||%|
|Accelerating percentage (% a+)||24.06||25.80||16.94||%|
|Decelerating percentage (% a−)||31.77||21.23||23.23||%|
|Idle percentage (% idling) 1||17.40||28.50||44.51||%|
|Average acceleration (a+ ave)||0.43||0.42||0.43||m/s2|
|Average deceleration (a− ave)||0.59||0.58||0.59||m/s2|
|Maximum acceleration (a+ max)||1.41||1.48||1.30||m/s2|
|Maximum deceleration (a− max)||3.89||2.62||2.15||m/s2|
|Average speed (Speed ave) 1||23.72||14.76||11.16||km/h|
|Maximum speed (Speed max)||64.01||47.99||51.98||km/h|
|NTD for low SFC scenario||18.93||10.03||5.32||2.82|
|NTD for typical SFC scenario||18.93||8.71||4.01||1.84|
|NTD for high SFC scenario||18.93||13.25||9.28||6.49|
|Diesel||Deep-Cycle Lead Acid||Li-Ion||Na-NiCl2||Ni-MH||Lithium-Sulfur|
|Motor power req. [kW]||89||79||65||78||81||69|
|Motor torque req. [Nm]||370||335||236||331||342||290|
|Acceleration capacity (time to 70 km/h) [s]||23.43||15.55||15.60||15.56||15.55||15.59|
|Max. speed 1 [km/h]||112||156||142||156||158||145|
|Energy consumption 2 [Wh/km]||2147.7||653.2||539.7||645.2||665.2||571.9|
|Vehicle Curb weight [kg]||2575||3242||2354||3181||3335||2613|
|Number of batteries in a rack||-||25||83||-||-||-|
|Number of battery racks||-||1||26||2||2||2|
|Dist. Until 0% SoC [km]||327||117||77||120||118||128|
|Dist. until 20% SoC [km]||261||94||61||96||94||102|
|CO2 net emissions|
|Well to Tank 3 [gCO2/km]||139||574||474||567||585||502|
|Tank to Wheel [gCO2/km]||553||0||0||0||0||0|
|Well to Wheel [gCO2/km]||692||574||474||567||585||502|
|Vehicle cost [USD]||$48,790||$40,860||$33,037||$57,148||$51,691||$42,407|
|Battery pack cost [USD]||-||$12,475||$5287||$28,807||$23,239||$14,477|
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Huertas, J.I.; Mogro, A.E.; Jiménez, J.P. Configuration of Electric Vehicles for Specific Applications from a Holistic Perspective. World Electr. Veh. J. 2022, 13, 29. https://doi.org/10.3390/wevj13020029
Huertas JI, Mogro AE, Jiménez JP. Configuration of Electric Vehicles for Specific Applications from a Holistic Perspective. World Electric Vehicle Journal. 2022; 13(2):29. https://doi.org/10.3390/wevj13020029Chicago/Turabian Style
Huertas, José I., Antonio E. Mogro, and Juan P. Jiménez. 2022. "Configuration of Electric Vehicles for Specific Applications from a Holistic Perspective" World Electric Vehicle Journal 13, no. 2: 29. https://doi.org/10.3390/wevj13020029