plug-in hev vehicle design options and expectations
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Plug-In HEV Vehicle Design
Options and Expectations
ZEV Technology SymposiumCalifornia Air Resources Board
Sacramento, CA
September 27, 2006
Tony MarkelNational Renewable Energy Laboratory
With support from
FreedomCAR and Vehicle Technologies Program
Office of Energy Efficiency and Renewable Energy
U.S. Department of Energy
NREL/PR-540-40630
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Key Messages
There are many ways to design a PHEV
the best design depends on your objective
PHEVs provide potential for petroleumdisplacement through fuel flexibility
what are the cost and emissions tradeoffs
PHEV design space has many dimensions
simulation being used for detailed exploration
Simulations using real-world travel data providesearly glimpse into in-use operation
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PHEV Stakeholder Objectives
ConsumersConsumersAffordable
Fun to driveFunctional
California Gov.California Gov.
Reduced air pollution
US Gov./DOEUS Gov./DOE
Reduced petroleum use
Auto ManufacturerAuto Manufacturer
Sell cars
Electric UtilityElectric Utility
Sell electricity
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A Plug-In Hybrid-Electric Vehicle (PHEV)
ELECTRIC ACCESSORIES
ADVANCED ENGINE
ENGINE IDLE-OFF
ENGINE DOWNSIZING
REGENERATIVE BRAKING
BATTERY RECHARGE
ELECTRICITY
PETROLEUM
AND/OR
Fuel Flexibility
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Some PHEV Definitions
Charge-Depleting (CD) Mode: An operating mode in which the energy storage SOCmay fluctuate but on-average decreases while driving
Charge-Sustaining (CS) Mode: An operating mode in which the energy storage SOCmay fluctuate but on-average is maintained at a certain level while driving
All-Electric Range (AER): After a full recharge, the total miles driven electrically(engine-off) before the engine turns on for the first time.
Electric Vehicle Miles (EVM): After a full recharge, the cumulative miles drivenelectrically (engine-off) before the vehicle reaches charge-sustaining mode.
Charge-Depleting Range (CDR): After a full recharge, the total miles driven before thevehicle reaches charge-sustaining mode.
Blended Strategy: A charge-depleting operating strategy in which the engine is used tosupplement battery/motor power.
PHEV20: A PHEV with useable energy storage equivalent to 20 miles of driving energyon a reference driving cycle. A PHEV20 can displace petroleum energy equivalent to20 miles of driving on the reference cycle with off-board electricity.
NOTE: PHEV20 does not imply that the vehicle will achieve 20 miles of AER, EVM or
CDR on the reference cycle nor any other driving cycle. Operating characteristics alsodepend on the power ratings of components, the powertrain control strategy and thenature of the driving cycle
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Battery Definition as Key Input to Simulation
kWh/mi(from simulation)
SOC window
PHEV range
P/E ratio
Performanceconstraints
kWh usable
kWh total
kWmotor
kWengine
DOH
Benefit of
plugging-in
Benefit ofhybridization
Total MPG Benefit
mass compounding
Input parameters that define the battery in BLUE
DOH = degree of hybridization
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Batteries in Current PHEVs
Johnson Controls/SAFT
Varta
Valence Technology
Kokam
A123 Systems
Electro Energy Inc.
NiMH
Co/Nibased
Li-I
on
Ironp
hosphate
basedLi-Ion
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Battery SOC Design Window
Battery cycle life is a strong
function of SOC swing:
In setting requirements, we must have realistic expectations for batterySOC design window because of the impacts on total battery size and life.
SOC design window is a key
factor in battery sizing: windowSOC
kWh
kWh
useable
total =
Daily Mileage Probability Distribution
0%
5%
10%
15%
20%
25%
0 10 20 30 40 50 60 70 80 90 100
Daily mileage (
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0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10 20 30 40 50 60
Daily Mileage / PHEVx
Design SOC window
based on PHEVx
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10 20 30 40 50 60
Daily Mileage / PHEVx
Average daily SOC
swing based on daily
mileage distribution
Daily mileage probability distribution
Battery SOC Design Window
Battery SOC design curve for 15 year cycle life
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Operating Strategy OptionsAll-Electric or Blended
Engine turns on when powerexceeds battery power capability
Engine only provides load thatexceeds battery power capability
Engine turns on when batteryreaches low state of charge
Requires high power battery andmotor
-30
-20
-10
0
10
20
30
40
50
60
70
0 5 10 15 20 25 30 35 40
Distance (mi)
Power(kW
)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
SOC(%)
engine
motor
SOC
All-Electric
-30
-20
-10
0
10
20
30
40
50
60
70
0 5 10 15 20 25 30 35 40
Distance (mi)
Power(kW)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
SOC
(%)
engine
motor
SOC
Blended
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Real Driving Survey Data
Provides valuable insight into travel behavior GPS augmented surveys supply details neededfor vehicle simulation
St Louis Travel Data Analysis
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St. Louis data set includes 227 vehicles from 147 households Complete second by second driving profile for one day 8650 miles of travel St. Louis data set is a small sample of real data
NPTS data is generated from mileage estimates
St. Louis Travel Data AnalysisDaily Driving Distance Similar to 1995 NPTS Data
0
2
4
6
8
10
12
00-
55-
10
10-1
5
15-2
0
20-2
5
25-3
0
30-3
5
35-4
0
40-4
5
45-5
0
50-5
5
55-6
0
60-6
5
65-7
0
70-7
5
75-8
0
80-8
5
85-9
0
90-9
5
95-1
00
Daily Distance (mi)
Frequency(
%)
0
10
20
30
40
50
60
70
80
90
100
CummulativeFrequency(%)
1995 NPTS Data
~33 mi0
1
2
3
4
5
6
7
2 4 6 8101214161820222426283032343638404244464850525456586062646668707274767880828486889092949698100
Daily Travel Distance (miles)
Frequency(%
)
0
10
20
30
40
50
60
70
80
90
100
CumulativeFreque
ncy(%)
Frequency (%)
Cumulative Freq. (%)
~29 mi
St. Louis HHTS Data
Consumption Distribution
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Consumption DistributionMany PHEVs Better than Rated Values
0 5 10 15 20 250
10
20
30
40
Fuel Consumption (L/100km)
PercentageofFleet(%)
Conventional
0 5 10 15 20 250
10
20
30
40
Fuel Consumption (L/100km)
PercentageofFleet(%)
Hybrid
0 5 10 15 20 250
10
20
30
40PHEV20
Fuel Consumption (L/100km)
Percentageo
fFleet(%)
0 5 10 15 20 250
10
20
30
40
Fuel Consumption (L/100km)
PercentageofFleet(%)
PHEV40
Real-world
City/HighwayComposite
39.2 mpg (6.0 L/100km)
US06
33.2 mpg (7.1 L/100km)
Real-world
City/Highway
Composite
67.4 mpg (3.49 L/100km)
City/Highway
Composite
54 mpg (4.35 L/100km)
US06
51.5 mpg (4.57 L/100km)
US06
39.6 mpg (5.94 L/100km)
Real-worldReal-world
City/Highway
Composite
26 mpg (9.05 L/100km)
US06
24.6 mpg (9.55 L/100km)
Fleet results are based on simulations of 227 vehicle
driving profiles from St. Louis metropolitan area.
PHEV R d F l C ti B >50%
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0 5 10 15 20 25 30
0
5
10
15
20
25
30
35
40
Time of Day (hr)
PercentageofVehicle
FleetInUse(%)
0 5 10 15 20 25 30
0
50
100
150
200
250
300
350
400
Cumula
tiveFuelConsumed(gallon
s)
Conventional
Hybrid
PHEV20
PHEV40
PHEVs Reduce Fuel Consumption By >50%
On Real-World Driving Cycles
8647 total miles driven 100% replacement of
sample fleet
227 vehicles from St. Louis each modeled as a conventional, hybr227 vehicles from St. Louis each modeled as a conventional, hybrid and PHEVid and PHEV
26 mpg
58 mpg &
140 Wh/mi
PHEVs:>40% reduction in energy
costs>$500 annual savings
37 mpg
76 mpg &
211 Wh/mi
Assumes $2.41/gal and 9/kWh
$1.21
$1.58
$2.48
$3.45
Gas.
Average Daily Costs
$0.72
$0.48
---
---
Elec.
5.1
5.4
6.5
9.1
/mi
PHEV40
PHEV20
HEV
CV
Simulated In Use All Electric Range Distribution
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Simulated In-Use All-Electric Range Distribution
Vehicles were designed to operate all electricallyon UDDS
Power demands of real profiles exceed UDDS peak
power within the first few miles
1 3 5 7 9 11 13 15 17 19 21 23 250
5
10
15
20
25
30
All Electric Range (mi)
PercentageofFleet(%)
PHEV20
0 5 10 15 20 25 30 35 400
5
10
15
20
25
30
35
40
All Electric Range (mi)
PercentageofFleet(%)
PHEV40
F el Econom and All Electric Range Comparison
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Fuel Economy and All-Electric Range Comparison
Significant difference between rated (EPA drivecycles) and real-world median values for PHEVs
Consumers likely to observe fuel economy higher
than rated value in daily driving
Vehicles designed with all-electric range likely tooperate in a blended mode to meet driver demands
** Fuel economy values do not include electrical energy consumption
Rated Median Rated Median
Conventional 26 24.4 n/a n/a
HEV 39.2 35.8 n/a n/aPHEV20 54 70.2 22.3 5.6PHEV40 67.4 133.6 35.8 3.8
Fuel Economy (mpg) ** All Electric Range (mi)
PHEV20 Savings Relative to Conventional and HEV
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PHEV20 Savings Relative to Conventional and HEV
Savings relative toconventional arealmost entirely
distance dependent
Savings relative to
HEV are distancedependent up toPHEV distance then
constant
Deep Dive into Real World PHEV Simulations
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Insights:
The PHEV20s that saved the most fuel relative to an HEV travel ~25 miles with speedsunder 60 mph and light accelerations
The PHEV20s that saved the least fuel relative to the HEV in the 20-30 mile range had
periods of 60+ mph highway driving and the accelerations were significantly moreaggressive
Most Savings Least Savings
Deep Dive into Real-World PHEV Simulations
Summary and Conclusions
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Summary and Conclusions
PHEVs provide petroleum displacement through fuelflexibility
Design needs to consider a spectrum of stakeholder
objectives Analysis of real-world travel behavior provides
perspective on design challenges
Vehicles designed as all-electric likely to operate as blended Whats emissions impact of real-world blended operation
In-use petroleum displacement not tied to all-electric
range Consider energy equivalentall-electric range
PHEV benefit is strongly related to distance andaggressiveness of real-world usage