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Electric and Hybrid Vehicles Final Exam: Updated
A+ Guide Solution
Describe the Charge-Depleting (CD) mode of PHEVs (Ans- an operating mode in which the SOC of PPS may fluctuate, but decreases on average while driving Describe the Charge-Sustaining (CS) mode of PHEVs (Ans- an operating mode in which the SOC of PPS may fluctuate, but is maintained at a certain level on average while driving Describe All Electric Range (AER) of PHEVs (Ans- after full recharge, the total kilometers driven electrically (engine off) before the engine turns on for the first time Describe the difference between Electric Vehicle Kilometers (EVKM) and Charge-Depleting Range (CDR) of PHEVs (Ans-
- for EVKM, after full recharge, the cumulative kilometers driven electrically (engine off) before the vehicle reaches charge-sustaining (CS) mode
- for CDR, after full recharge, the total kilometers driven before the vehicle reaches CS mode, Including propulsion of the engine, not just electrically
Describe the PHEVxx definition of PHEVs (Ans- a PHEV with useable energy storage equivalent to xx miles/kilometers on a referenced driving cycle, where xx is number of miles/kilometers. e.g. PHEV20 can displace fuel energy for an equivalent 20 kilometers of driving Describe the All Electric Range (AER) control strategy for PHEVs (Ans-
- uses energy of the energy storage intensively in the AER
- allows driver to manually select between CS mode and full EV
- if combustion engine use is restricted, design can go into full EV mode
- under normal conditions, driver can select pure EV mode, when the energy of the energy storage depletes to that of CS mode, CS mode will start automatically Describe the energy management approach of All Electric Range (AER) for PHEVs in terms of series hybrid or parallel hybrid design (Ans-
- the energy management approach divides the whole trip into pure EV and CS modes
- larger energy storage
- good vehicle performance Describe the blended control strategy approach for PHEVs (Ans-
- this strategy uses both engine and motor for traction, with Charge Depletion (CD) mode, until the SOC of PPS reaches the specified threshold
- at threshold, vehicle begins to operate in CS mode
- during CD mode, engine and motor operate at the same time
- the range before entering CS mode is longer than in full EV mode (AER control) When observing two graphs that both plot "remaining energy in PPS vs kilometers driven", how could we differentiate the two as using the All Electric Range (AER) control strategy or the Blended control strategy (Ans-
- both graphs will plot a linearly decreasing line that turns into a horizontally straight line at y = 0.3 (30% SOC of PPS), illustrating the vehicle reaching CS mode
- the graph with the steeper slope will use AER whereas the shallower slope uses blended
- this is because Blended control lasts longer in CD mode than AER control lasts in full EV mode before reaching CS mode Describe energy storage design of PHEVs in terms of its importance, the factors it impacts, and the parameters when designing energy storage (Ans-
- one of the most important components in PHEV
- energy storage closely relates to vehicle performance, fuel consumption, fuel displacement, initial cost, and operation cost
- most important parameters in energy storage design are the storage energy and power capacities The power requirement of a PHEVs energy storage is determined by what (Ans- solely the electric motor power rating and power electric component efficiencies Describe the working principle of a fuel cell (Ans-
- galvanic cell in which chemical energy of a fuel is converted directly into electrical energy by electrochemical processes
- fuel and oxidizing agent are continuously and separately supplied to cathode of the cell
List the 5 auxiliaries systems needed to support fuel cell operation (Ans-
- air circulating pump (largest energy consumer)
- coolant circulating pump
- ventilation fan
- fuel supply pump
- electrical control device List 6 major types of fuel cells and their electrolyte state (Ans-
- polymer exchange membrane fuel cell (PEMFC), solid
- alkaline fuel cell (AFC), liquid
- phosphoric acid fuel cell (PAFC), liquid
- molten carbonate fuel cell (MCFC), liquid
- solid oxide fuel cell (SOFC), solid
- direct methanol fuel cell (DMFC), solid Which type of fuel cell is the most investigated technology for automotive applications? State its operating temperature (C) and its electrolyte state
(Ans- polymer exchange membrane fuel cell (PEMFC), 60-100 C, solid electrolyte List 2 methods we could supply hydrogen fuel to fuel cells in regards to a vehicle application (Ans-
- produce hydrogen in ground stations and store pure hydrogen on- board
- produce hydrogen on-board from an easy carrying hydrogen carrier and feed fuel cells directly List 3 methods of on-board hydrogen storage for fuel cells (Ans-
- compressed hydrogen in a container at ambient temperature
- cryogenic liquid hydrogen at low temperature
- metal hydride method At the believed maximum pressure that hydrogen gas can reach, that being 700 Bar, how does the energy per litre for 1L of hydrogen compare to that of gasoline (Ans- the energy from 1 L of hydrogen at 700 Bar is only equivalent to 0.2 L of gasoline, or 1/5th of the energy capacity
- hydrocarbons such as gasoline, methane, or methanol are most likely candidates due to their ease of reforming List 3 methods of reforming and the hydrocarbons reformed with each (Ans-
- steam reforming (SR) (methanol, methane, gasoline)
- auto-thermal reforming (ATR) (gasoline)
- partial oxidation reforming (POX) (gasoline) List 3 disadvantages of the fuel cell HEV when compared with the current ICE (Ans- 1. heavy and bulky power unit
- low overall efficiency due to large power output under acceleration and low power output at low speed driving
- fuel cell HEV is completely different from conventional ICE powered vehicles, requiring a totally new powertrain design List the 9 key components of a fuel cell HEV drivetrain (Ans- 1. auxiliary battery
- battery pack
- DC/DC converter
- electric traction motor
- fuel cell stack
- fuel tank
- power electronics controller
- thermal cooling system
- transmission no answer Draw the configuration of a fuel cell hybrid drivetrain (Ans- no answer When designing an electric vehicle, referencing a mild driving cycle will result in what (Ans-
- smaller energy storage
- sluggish vehicle performance no answer review AER focused control strategy simulation results (PHEV lectures, slides 9-15) (Ans- no answer The fuel cell hybrid control strategy ensures what 3 things (Ans- 1. power output of electric motor always meets demanded power
- energy level of PPS always maintained within optimal region
Describe the control strategy corresponding to the given scenario for traction mode in a fuel cell HEV drivetrain: Demanded power is less than preset minimum power of fuel cell system, and PPS does not require charging (Ans- - fuel cell system operates at idle
- PPS alone drives the wheels Describe the control strategy corresponding to the given scenario for traction mode in a fuel cell HEV drivetrain: Demanded power is greater than preset minimum power but less than maximum rated power of fuel cell system, and PPS does not require charging (Ans- fuel cell system operates optimally to drive the wheels Describe the control strategy corresponding to the given scenario for traction mode in a fuel cell HEV drivetrain: Demanded power is greater than preset minimum power but less than maximum rated power of fuel cell system, and PPS requires charging (Ans- fuel cell system operates at maximum rated power, driving wheels and charging PPS
Regenerative braking is effective only for the _____ axle on passenger vehicles (Ans- front List the % of braking energy to total tractive energy of a specific drive cycle (Ans- FTP75 - 55.4% LA92 - 58.01% US06 - 40.73% NYCC - 81.9% ECE15 - 34.08% It is _____ to regenerate at low speeds, because of _____ motor _____ (Ans- difficult, low, voltage A successfully designed braking system for a vehicle must always meet the demands of: (Ans- - quickly reducing vehicle speed
- maintaining vehicle direction controllable by steering wheel Generally, braking torque required is _____ than the torque that an electric motor can produce (Ans- much larger Possible design and control configurations of parallel hybrid braking systems include: (Ans- - fixed ratios between electrical and mechanical braking forces
For the control strategy of optimal braking performance, which conditions will require mechanical and/or regenerative braking (Ans- - if demanded braking force is less than that produced by the electric motor, the motor produces the total braking force, aka all regenerative braking and no mechanical
- if demanded braking force is greater than that produced by the electric motor, the electric motor should produce its maximum braking force that is limited by the motor or energy storage, the rest is mechanical braking For the control strategy of optimal energy recovery, describe the relationship between braking of front and rear axle (Ans- - braking forces on front and rear axle are variable within certain range, which is dependant on vehicle deceleration rate (j) and road adhesive coefficient (μ) List the 4 mechanical components that make up a planetary gear speed- coupling device (Ans- 1. ring gear
- sun gear
- planetary gears 4, yoke When _____ element(s) among the sun gear, ring gear, and yoke is locked to the _____, that is, _____ degree(s) of freedom is constrained, the unit becomes a ______ transmission (Ans- - one
- vehicle frame
- one
- single gear List the 3 sub modes of operation for speed-coupling mode of a series- parallel drivetrain (Ans- 1. engine alone traction
- motor/generator alone traction
- engine and motor/generator with speed-coupling traction List the 6 sub modes of operation for torque-coupling mode of a series- parallel drivetrain (Ans- 1. engine alone plus traction motor motoring
- engine alone plus traction motor generating
- motor/generator alone plus traction motor motoring
- motor/generator alone plus traction motor generating
- speed-coupling traction plus traction motor motoring
- speed-coupling traction plus traction motor generating Describe regenerative braking in terms of which components produce braking torque, where the energy is captured, and which components are not operating (Ans- - the traction motor, motor/generator, or both produce the braking torque
- the recaptured energy is used to charge the PPS
For a PHEV, the average net energy consumption of the PPS in a complete driving cycle is what (Ans- zero, energy level in PPS at the beginning and end of the driving cycle are equal For a PHEV, the energy storage in the PPS is considered sufficient if it can sustain operation for what range of time (Ans- 0.05 hours to 0. hour Which components are the most promising candidates as the PPS for PHEV's (Ans- ultracapacitors, high-power batteries, or the combination of both What 3 things make PPS sustained hybrid drivetrains unique from other powertrains (Ans- - drivetrain control strategy
- energy storage design
- slightly different electric motor power design The major feature of PHEVs is what (Ans- charging energy in the energy storage device from the utility grid, opposed to through petroleum, displacing part of the petroleum fuel consumption
The amount of petroleum fuel displaced by the utility electricity depends on what 3 things (Ans- - amount of electrical energy per recharge
- total driving distance between recharges
- electrical power usage profiles List 3 driving cycles used to represent driving in the USA (Ans- - FTP 72: urban route, starts with engine cold start
- FTP 75: like FTP 72 but executed with a hot engine
- LA-92: represents urban driving cycle with average speed higher than FTP 72
- NYCC: represents urban route through New York
- US06: aggressive driving cycle that describes driving pattern under high engine loads
