combined hybrid talks
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MAE 442 Automotive Engineering:
Hybrids
Ewan Pritchard, PE
October 5th, 2009
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Hybrid Definition
A hybrid is a combination of two things
In this case we mean a vehicle powered by two different
power plants> Electric motor
> Internal combustion engine
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Is a Hybrid Vehicle a New Idea?
Hybrids existed in the late 1800s
> Cars could be fuelled by either electric or ethanol
> No regenerative energy
> The invention of the IGBT
between 1960 and 1990
made way for the modern
hybrid electric
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The Modern Hybrid
Does not idle when stopped
Uses a battery pack to store energy
Uses an electric motor to accelerate
Recharges batteries when braking or coasting Allows for a smaller gasoline engine
Increased fuel economy, lower emissions, and lower enginewear
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Why Hybrid: Fuel Economy
As fuel prices riseso does the drive to improve fueleconomy
Reduced Dependence on Foreign Fuel
Fossil fuels are not sustainableit took millions of years tomake them, and about 300 years to consume them.
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Why Hybrid: Emissions
Environmental issues
>NOxnitrogen oxides Works with sunlight to form ozone (lung damage)
Forms nitric acid in the air (acid rain) Enters the upper atmosphere and causes a
greenhouse effect. (Global warming & climate change)>
CO2carbon dioxide Enters the upper atmosphere and causes a
greenhouse effect. (Global warming & climate change)
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Why Hybrid: Emissions
Environmental issues
> Particulate Matter
PM1010 microns in size, particulates enter the upperrespiratory system and cause congestion, smaller
particles cause lung damage.
PM2.52.5 microns in size, passes through the alveoli
in the lungs and enters the bloodstream to cause
pulmonary distress
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Why Hybrid: PerformanceA tale of two drivelines both 102 kW (137 HP)
0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000
100
200
300
400
500
600
Speed (rpm)
Torque(Nm)
Fuel Converter Operation
1991 Dodge Caravan 3.0L (102kW) SI Engine - transient data
0.10.14
0.1
0.18
0.1
0.20.2
0.22
0.22
0.240.26
0.28
0.28
0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000
100
200
300
400
500
600
Speed (rpm)
MotorTorque(Nm)
Motor/Inverter Eff iciency and Continuous Torque Capability -
Unique Mobility 100kW (peak) PM motor/inverter
0.82
0.84
0.86
0.880.9
0.92
0.94
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Conventional versus Hybrid Design
Conventional Design Characteristics:
> Total Power (Top Speed)
> mile time
> 0-60
Modern Design Characteristics:
>
Pep (acceleration at particular speeds)> Fuel economy on a specific drive cycle
> Ability to meet trace
> Minimized emissions on that cycle
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Drive Cycle
Hybrids and Plug-In hybrids add new dimensions to a
historically single dimension problem
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Where the Power Goes
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A Hybrid Electric System Can Help Minimize
These Losses
Engine losses
Standby/idle losses
Driveline losses
Braking losses
Electric accessories
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Engine Losses and Idling
~80% of Total Losses An engine will typically run at manydifferent efficienciesThis engine could run at 44% efficient
It will likely average at about 18%
By eliminating idling and low torque, the
average could be easily running over 30%
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Driveline Losses
~5.6% of Total LossesHybrid drivelines can be applied inseveral ways, one possibility (series
hybrid) can eliminate the driveline
completely, eliminating this loss
All Electric
Conventional
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Driveline Losses
~5.6% of Total LossesIn a series driveline, only anelectric motor is connected to the
drive wheels
In a parallel system, both the
gasoline and the electric motor are
connected to the drive wheels
Parallel
Series
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Braking Losses and Inertia
~5.8% of Total Losses A hybrid vehicle can significantly reducebraking losses by recapturing the energyelectrically in a generator
This also significantly reduces brake wear
The vehicle is also slowed while traveling
down hills by regeneration
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Auxiliary and Accessory Loads
~2.2% of Total Losses
Includes fans, pumps, compressors and alternator
When these are belt driven, they are subject to the current engine speed, which canrange from 800 RPM up to 6000 RPM
At varying speeds these accessories are typically VERY inefficient
Each of these is moving towards electrically driven components due to the inherentlyhigher efficiency of electric motors
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Hybrid and Electric Vehicle Components
All hybrid and electric vehicles have 4 basic components.
1. Electric Motor
2. Controller/Inverter/Drive
3. Batteries
4. Logic
Improvements in high power electronics, materials and
computing capacity have led to significant changes in the
past 20 years.
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INDUCTIONMOTOR COMPONENTS
Rotating components
> [1] Shaft
> [2] Rotor
> [3] Rotor fins> [4] Fan
[1] [2] [3] [4]
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INDUCTIONMOTOR COMPONENTS
Housing components
> [5] End bells / bearing
housings
>
[6] Stator housing> [7] Cooling fins
> [8] Junction box
> [9] Fan shroud
[5] [6] [7] [8] [9]
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INDUCTIONMOTOR COMPONENTS
Fixed components
> [10] Seals
> [11] Stator windings
> [12] Core iron / laminationstack
> [13] Bearings
[10] [11] [12] [13]
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Components:Electric Motor - DC
Graphic courtesy of SMMA | www.smma.org
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Components:Electric Motor - AC
Graphic courtesy of SMMA | www.smma.org
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Components:Electric Motor - Controlled
Graphic courtesy of SMMA | www.smma.org
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Controller
Converts Battery DC to a chopped DC power
Can chop in amplitude (DC) or frequency (AC)
Power is based on low voltage input signal
> 4-20 mA or 0-5V
In other fields this is called a drive or inverter
> Variable Frequency (AC)
> Pulse Width Modulation (AC)
> Buck Conversion (Reduce - DC)
> Boost Conversion (Increase - DC)
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Batteries
Batteries rule the performance of the vehicle> They dictate how much power you get (kW)
> They dictate how much energy you get (kWh)
A single cell dictates the battery voltage each cell mates twodissimilar materials
> Lead Acid (2.1 V)
>
Nickel Cadmium (1.2 V)> Nickel-Metal Hydride (1.2 V)
> Lithium-Ion (3.7 V)
Anode (+) Cathode Electrolyte
Pb PbO2 KOH
NiOOH Ni H2SO4
NiOOH AB5 * KOH
LiC6 Li2FePO4F LiPF6
* AB5is a combination of (A) rare earth mixture and (B) Zirconium or Nickel
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Batteries: Packaging
Cylindrical
Prismatic
Button
Pouch
Source: www.batteryuniversity.com
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Batteries: Packaging
Cylindrical
Prismatic
Button
Pouch
Source: www.batteryuniversity.com
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Batteries: Packaging
Cylindrical
Prismatic
Button
Pouch
Source: www.batteryuniversity.com
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Batteries:PackagingCylindrical
Prismatic
Button
Pouch
Source: www.batteryuniversity.com
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Batteries (section 12.1.2)
State of Charge (SOC)
> Measured as a percentage of total
battery energy (0-100%)
>
Typically should not go below 20%
Depth of Discharge (DoD)
> Inverse of SOC
Power (kW)
Energy (kWh)
The 18650 cell is proving to be
common for hybrids. Similar to
a AA cell, the dimensions are
18mm in diameter and 650mm
in length.
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Batteries: Basic Characteristics
A-h> Typically used for power batteries
> Cells often described in mA-h
C Rate
> A normalized rate of power use to qualify testing
>100% discharge divided by the time in hours
> C2 means the discharge rate was 100% in hour
> C/2 means the rate was less aggressiveover 2 hours
Cycle Life
> Always measured based on DoD
>
Ex. 1000 cycles at 80% DoD Weight/Volume
> Measures in terms of
W/kg and W-h/kg
W/l and W-h/l
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Cycle Life
Source: Duvall, EPRI Study of cycle life versus depth of discharge
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Energy Densities
Source: www.batteryuniversity.com
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Ragone Plot
Source: Lawrence Berkeley National Labs
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MAE 442 Automotive Engineering:
Hybrids II
Ewan Pritchard, PE
October 7th
, 2009
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Agenda
Batteries
Engine Coupling
Prius Transmission School Bus Program
FinishViewing ATEC Plug-In Prius Outside
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Battery Prices
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Lithium Ion
Battery PbA Ni-MH Li-Ion
Energy/weight (W-h/kg) 40 80 160
Energy/size (W-h/l) 75 300 270
Power/weight (W/kg) 180 1000 1800
C/D efficiency (%) 80% 66% 99.9%
Price ($/kW-h) 200 400 600
Self-discharge rate (%/month) 10% 30% 3%
Cycle durability (80% cycles) ~900 ~6,500 ~10,000
Nominal Cell Voltage (V) 2.0 1.2 3.6/ 3.7
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Engine Map: Efficiency
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Engine Map: Efficiency
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Engine Map: NOxEmissions
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Engine Map: PM
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Powertrain Integration
Series Hybrid
> Driveline (Volt)
> Hub motor (Volvo)
Parallel Hybrid
> Pre-transmission (Honda, Eaton)
> Post-transmission (Enova School Buses)
> Transmission Integrated (Ford, Toyota, GM, Allison)
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Electric (Easiest)
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Series
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Through The Road (Parallel)
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Parallel
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Transmission Integrated
Planetary Gearset (Prius, Ford, GM Two-Mode)
Sun MG1
Planet Carrier - Internal
Combustion Engine
Outer Ring MG2
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Transmission IntegratedImage from
http://privatenrg.com/#Nomograph
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Planetary Gearset (Toyota, Ford, GM)
Flash animation from Eric Hart at:
http://eahart.com/flash/PSDAnim.swf
Sun:30 Teeth MG1PM AC Sync
6,500 RPM
18 kW. This has been increased
to 10,000 RPM
Planets:23 Teeth Combustion
engine+5000 RPM
57 kW
Outer Ring:78 Teeth
MG2 PM AC Sync.
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Prius Transmission
Due to the gear ratios, we can say that:
> If Planet Carrier (ICE) is held:
MG1(sun)= -78/30*MG2 (Outer Race)= -2.6*MG2
> If Outer Race is held:
MG1= 3.6 * ICE
MG1 = 3.6 * ICE - 2.6 * MG2
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Prius Transmission
Due to the gear ratios, we can say that:
> If Planet Carrier (ICE) is held:
MG1(sun)= -78/30*MG2 (Outer Race)= -2.6*MG2
> If Outer Race is held:
MG1= (1 + 2.6 )*ICE
MG1 = 3.6 * ICE - 2.6 * MG2
Excerpt from:
http://prius.ecrostech.com/original/Understanding/PowerSplitDevice.htm
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Hybrid School Bus Project
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IC Corporation (International)selected based on specific criteria
Plug-in
PHEV-22.5kWh Li-Ion
$220k (or $139k premium)
First bus delivered March 2007
11 buses delivered to date
Early success for HD-PHEV
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PHEV components
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Estimated benefits
Plugging-in is optional
90-100% fuel economy improvement for first 45 miles,
40% increase for remainder
90% reduction in particulate matter
60% reduction in NOx
Increased engine, transmission and brake life Electricity cost of 60 / gallon equivalent
Option for renewable energy at $1 / gallon
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Nationwide plug-in deploymentDelivered
Arkansas (1)
California (1)
Florida (2)
North Carolina (2)
Pennsylvania (1)
South Carolina (2)
Texas (1)
Washington (1)
Funded / Ordered
Iowa (2)
New York (2)
Pending
Texas (1)
Virginia (1)
Washington (1)
Washington DC (1)
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Next steps
Four more buses have been ordered
Two year monitoring period to record performance
> Emission
> Fuel economy> Maintenance
> General operation
> Driving performance
How closely we monitor them is dependent upon funding
Facilitation of 300 bus purchase
> Anticipated $80,000 premium
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Preliminary monitoring results
0
1
2
3
4
5
6
7
8
9
8/5/20
07
8/15/200
7
8/25
/200
7
9/4/20
07
9/14/200
7
9/24
/200
7
10/4/200
7
10/1
4/20
07
10/2
4/20
07
Date (DD/MM/YYYY)
604 Control
607 Hybrid
604 Control Average: 5.4 MPG
607 Plug-In Hybrid Average: 7.4 MPG
Plug-In Hybrid Benefit:
2 MPG increase
30% increase
* Control Route Shifted by 2 w eeks to align route and driver
FuelEconomy(MPG
)
Florida Buses (Track 1)
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0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
7/17/2007 7/27/2007 8/6/2007 8/16/2007 8/26/2007 9/5/2007 9/15/2007 9/25/2007 10/5/2007
Date
MPG
Not Plugged In
Plugged In
Plug-in benefitsWake County, N.C., Hybrid School Bus
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Enova data logging
-100
-80
-60
-40
-20
0
20
40
60
80
100
0 10 20 30 40 50 60
Speed (mph)
Power(kW) First Gear
Second Gear
Third Gear
Fourth Gear
Fifth Gear
Power versus Speed
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Incremental cost per unit
$0
$40,000
$80,000
$120,000
$160,000
$200,000
0 200 400 600 800 1000 1200 1400 1600 1800 2000
IncrementalCost($
)
Number of Units Sold
School districts
portion
In need of funding
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School Bus Modeling
The characteristics are used to virtually build a
bus in ADVISOR NRELsADvanced VehIcle
SimulatOR
ADVISOR uses Matlab and Simulink to model
a vehicle based on a specific route and vehicleinformation.
The results are Performance, Fuel Economy,
and Emissions.
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School Bus Modeling
By defining each component, any vehicle can
be adequately modeled.
There is a LOT to define and wide assumptions
can lead to a lot of error.
We ran many trials to understand thesensitivity of the variables
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School Bus Modeling
By defining each component, any vehicle can
be adequately modeled
There is a LOT to define and wide assumptions
can lead to a lot of error
We ran many trials to understand thesensitivity of the variables
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School Bus Modeling
Each model can be run through a predefined
route
We used the West Virginia Suburban Cycle six
times
The vehicle can also be run throughacceleration and grade trials.
Each model takes about 3 minutes to run.
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School Bus Modeling
The results show acceleration rates, fuel usage
and emissions
Many parameters can be analyzed such as
overall ratio
Additional information can be gathered aboutenergy use
This model appears to be off, we know the fuel
economy should average at about 8.2 miles per
gallon
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School Bus Modeling
The loss plot shows usages of each
component
From this loss plot we can imaging how
much energy could have been saved.
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School Bus Modeling
The Parallel Model
80 kW engine (~107 hp)
Lead Acid Batteries
100 kW Electric Motor
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School Bus Modeling
11.4 mpg
But.. It is depleting the battery pack
9.107 grams per mile NOx
Much Faster acceleration times, this
model is likely oversized
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School Bus Modeling
Series Model
112 kW engine (150 hp)
116 kW Electric Motor (155 hp)
131 kW generator (175 hp)
1 speed transmission
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School Bus Modeling
9 mpg
Still depleting the battery pack
1.583 grams per mile NOx
Slightly better acceleration
Engine is ALWAYS on.
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Where can you fit in?
Currently seeking graduate students to perform research
under ATEC
Join Eco-Car Challenge
Go work for a major auto manufacturer and join ATEC
Tell others about the work going on at NCSU
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Please Call with QuestionsEwan Pritchard, PE
Program ManagerAdvanced Transportation Energy Center (ATEC)
North Carolina State University
MRC - Suite 339Campus Box 7237
Raleigh, NC 27695-7237
919.515.2194 (office)
919.819.0098 (cell)[email protected]
www.atec.ncsu.edu