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Plug-in HEV Vehicle DesignOptions and Expectations

ZEV Technology SymposiumCalifornia Air Resources Board

Sacramento, CA

September 27, 2006

Tony Markel

National Renewable Energy Laboratory

With support from

FreedomCAR and Vehicle Technologies Program

Office of Energy Efficiency and Renewable Energy

U.S. Department of Energy


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Disclaimer and Government License

This work has been authored by Midwest Research Institute (MRI) under Contract No. DE-AC36-99GO10337 with the U.S. Department of Energy (the DOE). The United States Government (theGovernment) retains and the publisher, by accepting the work for publication, acknowledges thatthe Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish orreproduce the published form of this work, or allow others to do so, for Government purposes.

Neither MRI, the DOE, the Government, nor any other agency thereof, nor any of their employees,makes any warranty, express or implied, or assumes any liability or responsibility for the accuracy,completeness, or usefulness of any information, apparatus, product, or process disclosed, orrepresents that its use would not infringe any privately owned rights. Reference herein to anyspecific commercial product, process, or service by trade name, trademark, manufacturer, orotherwise does not constitute or imply its endorsement, recommendation, or favoring by the

Government or any agency thereof. The views and opinions of the authors and/or presentersexpressed herein do not necessarily state or reflect those of MRI, the DOE, the Government, orany agency thereof.


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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 ManufacturerSell cars

Electric UtilityElectric UtilitySell 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 orCDR on the reference cycle nor any other driving cycle. Operating characteristics alsodepend on the power ratings of components, the powertrain control strategy and the

nature 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 ofplugging-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/Ni

based

Li-Ion

Iro

nphosphate

b

asedLi-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 keyfactor in battery sizing: windowSOC

kWhkWh useabletotal

=

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 windowbased 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 SOCswing based on dailymileage distribution

Battery SOC Design Window

Daily mileage probability distribution

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 and

motor

-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(%)

enginemotor

SOC

Blended


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Real Driving Survey Data

Provides valuable insight into travel behavior GPS augmented surveys supply details needed

for vehicle simulation


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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

CumulativeFrequenc

y(%)

Frequency (%)Cumulative Freq. (%)

~29 mi

St. Louis HHTS Data


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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)

Percentag

eofFleet(%)

Conventional

0 5 10 15 20 250

10

20

30

40


Percentag

eofFleet(%)

Hybrid

0 5 10 15 20 250

10

20

30

40PHEV20


PercentageofFleet(%)

0 5 10 15 20 250

10

20

30

40


PercentageofFleet(%)

PHEV40

Real-world

City/HighwayComposite

39.2 mpg (6.0 L/100km)

US0633.2 mpg (7.1 L/100km)

Real-world


67.4 mpg (3.49 L/100km)


54 mpg (4.35 L/100km)

US0651.5 mpg (4.57 L/100km)

US0639.6 mpg (5.94 L/100km)

Real-worldReal-world


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.


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0 5 10 15 20 25 300

5

10

15

20

25

30

35

40

Time of Day (hr)

PercentageofVehicle

FleetInUse(%

)

0 5 10 15 20 25 300

50

100

150

200

250

300

350

400

Cumu

lativeFuelConsumed(gallons)

Conventional

Hybrid

PHEV20PHEV40

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 energycosts

>$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


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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)

PercentageofFlee

t(%)

PHEV20

0 5 10 15 20 25 30 35 400

5

10

15

20

25

30

35

40

All Electric Range (mi)

PercentageofFlee

t(%)

PHEV40


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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 higherthan 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/aHEV 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)


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PHEV20 Savings Relative to Conventional and HEV

Savings relative toconventional are

almost entirelydistance dependent

Savings relative to

HEV are distancedependent up toPHEV distance then

constant


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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 hadperiods of 60+ mph highway driving and the accelerations were significantly more

aggressive

Most Savings Least Savings

Deep Dive into Real-World PHEV Simulations


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Summary and Conclusions

PHEVs provide petroleum displacement through fuelflexibility

Design needs to consider a spectrum of stakeholderobjectives

Analysis of real-world travel behavior providesperspective 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-electricrange

Consider energy equivalentall-electric range

PHEV benefit is strongly related to distance andaggressiveness of real-world usage

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