EVALUATION OF PERFORMANCES OF HYBRID ELECTRIC …€¦ · e applications – 3-3 1 evaluation of performances of hybrid electric energy storage system (li-ion batteries/ supercapacitors):

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EVALUATION OF PERFORMANCES OF

HYBRID ELECTRIC ENERGY STORAGE

SYSTEM (LI-ION BATTERIES/

SUPERCAPACITORS): EV AND HEV

APPLICATIONS

J. Lemaire, J. Nzisabira, P. Duysinx

Department of Aerospace and Mechanical Engineering

University of Liège

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INTRODUCTION EESS APPLICATIONS CONCLUSION MODELLING & SIMULATION EV HESS

2

OUTLINE

Introduction

Electric vehicle

Electric energy storage systems

Hybrid energy storage systems

Modeling and simulation

Applications

Conclusion and perspectives

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INTRODUCTION

ELECTRIC AND HYBRID ELECTRIC VEHICLES Alternative solutions to reduce the air-pollution, noise and fossil fuel

dependence of the transportation sector

Limitations

Energy storage systems must have a sufficient power, energy density and autonomy.

Batteries’ life time and capacity are limited by the number and the magnitude of current peaks

The efficiency depends on the discharge current regime.

Cost

Foreseen solution

Peak power units (e.g. supercapacitors, flywheels...)

The hybridization of the energy storage systems (Battery&EDLC) allows increasing the life-time of the main energy source in case of a battery-electric vehicle

The aim of this study is to evaluate the performances of a hybrid energy storage system (Li-ion batteries and EDLC) in the case of an EV.

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ELECTRIC VEHICLE

PRINCIPLE:

Electric storage system (i.e.

batteries)

Electronic unit

Electric motor

Transmission to wheels

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ELECTRIC ENERGY STORAGE SYSTEMS

BATTERIES

Improved chemical energy storage

High energy density : ~100 Wh/kg

Low Power density : ~1 kW/kg

Good efficiency (less than 70% to 98%)

Limited life cycle : < 5000 cycles

Small temperature range : bad efficiency

and battery components damages for

negative temperatures

Recycling not improved

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SUPERCAPACITORS

Increasing electric storage interest

Low energy density: ~10 Wh/kg

Higher power density : ~10 kW/kg

High efficiency (95% to 100%)

Long life cycle : > 100.000 cycles

High temperature range : -45 to 60°C

Less pollutant than batteries : easiest to

recycle

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COMPARISON BETWEEN BATTERIES AND SUPERCAPACITORS

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COMPARISON BETWEEN BATTERIES AND SUPERCAPACITORS

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HYBRID ENERGY STORAGE SYSTEMS

PRINCIPLE

Parallel combination of battery pack directly connected on a power bus (nearly constant voltage) and supercapacitors module linked with a DC/DC converter

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HYBRID ENERGY STORAGE SYSTEMS

ADVANTAGES

Energy < batteries (autonomy)

Power < supercapacitors

(accelerations)

If extra power needed then the 2

systems (battery and scaps) are

summed up

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MODELLING & SIMULATION

POWER MODEL

Vehicle dynamic :

mvax = Ft - mvg sin θ - Fr – Fa

Ft : traction force

mvg sin θ : grade force

Fr = cr (v, p,…) . mv .g .cos(α) : rolling force

Fa = ½ ρa . Af . cx (v,…) . vr² : aerodynamic force

Total power :

P = Pt - PR = W / Δ t = F

dx/dt = F . V

Current :

P = U . I

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EFFICIENCY : 90% from energy storage to wheel

Batteries : strongly variable (depends on current density and variability, temperature…), 70% to 98% (discrete steps decreasing with current growing)

SC : mainly constant and high, 98%

DRIVING CYCLES : ARTEMIS CYCLES

Artemis (Assessment and Reliability of Transport Emission Models in Inventory Systems)

Realistic cycles

3 cycle types :

urban cycle (distance = 4,870 km)

road cycle (distance = 17,272 km)

motorway cycle (distance = 29,545 km)

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DRIVING CYCLES : ARTEMIS CYCLES ARTEMIS urban driving cycle for passenger cars

0

10

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30

40

50

60

70

80

90

100

0 120 240 360 480 600 720 840 960Time (s)

Speed

(km/h)

-5

-4

-3

-2

-1

0

1

2

3

4

5

Acc

(m/s2)urban dense congested,

stops

flowing,

table

free-flow urban congested,

low speed

start

phase

Speed

Acceleration

Speed max. : 58 km/h

Speed average. : 17,7 km/h

Acceleration max. : +2,44 -2,81m/s2

Distance max. : 4,87 kms

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APPLICATIONS

VW GOLF VI 100kW :

Mass : m ~1500 kg

Drag coefficient :

Cx ~ 0,31

Front surface :

Af ~ 2,6 m²

Coefficient of rolling resistance : cr ~ 0,012

Power ICE : P = 100 kW

Maximum engine performance : η = 0,35

Motorisation mass : ~ 250 kg

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APPLICATIONS

POWER CURVES Urban power

-40

-35

-30

-25

-20

-15

-10

-5

0

5

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15

20

25

30

35

40

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960Time [s]

Po

wer

[kW

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APPLICATIONS

POWER CURVES Road power

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 1020 1080

Time [s]

Po

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W]

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APPLICATIONS

POWER CURVES Motorway power

-100

-80

-60

-40

-20

0

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40

60

80

100

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 1020Time [s]

Po

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[kW

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APPLICATIONS

ENERGY CAPACITY NEEDED

Choice of 400V bus voltage

Initially only from batteries

Combination of twice the 3 cycles :

~ 103 km

energy needed : 60,84 Ah

Li-ion battery : not under 80% DoD

final energy : 76,05 Ah

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APPLICATIONS

BATTERY

Dow Kokam Xalt HE 75 (Li-Po)

Mass : 1,53 kg

Vnom : 3,7 V

Capacity : 75 Ah

Spec. Power : 0,54 kW/kg

Spec. Energy : 180 Wh/kg

Impedance : 0,5 mΩ

Battery pack :

Cells’ number : 108 (~400V)

Mass : ~ 165 kg

Volume : ~ 86 dm³

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APPLICATIONS

BATTERY EFFICIENCY

Constant current discharge

Variable current discharge

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APPLICATIONS

CURRENT CURVES Urban current limits

-100

-80

-60

-40

-20

0

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60

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100

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960Time [s]

Cu

rren

t [A

]

0,5C

1C

-1C

-0,5C

0,25C

-0,25C

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APPLICATIONS

CURRENT CURVES Motorway current limits

-240

-200

-160

-120

-80

-40

0

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80

120

160

200

240

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Time [s]

Cu

rren

t [A

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0,5C

-0,5C

-1C

-1,5C

-2C

1C

1,5C

2C

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APPLICATIONS

SUPERCAPACITOR

Limits peaks current on batteries

Supercapacitor Maxwell BCAP 2600

CN : 2600 F

UN : 2,5 V

Mass : 0,52 kg

Rint : 0,25 mΩ

Spec. energy :

~ 4,34 Wh/kg

Spec. power :

~ 15 kW/kg

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APPLICATIONS

SUPERCAPACITOR MODULE Cells’ number : optimization

between available supercapacitor’s energy and additional mass

energy depends on driving situation (urban, road or motorway)

hardest in discharging is motorway

SC pack : Cells’ number : 160 (in series, 400V max)

Mass : 83 kg

Volume : 72,38 dm³

Energy (Unom – U/2) : 270 Wh

~ 1,13 Ah

Motorway current limits

-240

-200

-160

-120

-80

-40

0

40

80

120

160

200

240

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Time [s]

Cu

rren

t [A

]

0,5C

-0,5C

-1C

-1,5C

-2C

1C

1,5C

2C

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APPLICATIONS

SUPERCAPACITOR MODULE

Efficiency


-240

-200

-160

-120

-80

-40

0

40

80

120

160

200

240

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 1020

Time [s]

Cu

rren

t [A

]

0,5C

-0,5C

-1C

-1,5C

-2C

1C

1,5C

2C

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APPLICATIONS


Efficiency

Problem : urban cycle never goes above 1,5C

supercapacitors not used in urban cycle!


-240

-200

-160

-120

-80

-40

0

40

80

120

160

200

240

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 1020

Time [s]

Cu

rren

t [A

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0,5C

-0,5C

-1C

-1,5C

-2C

1C

1,5C

2C

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APPLICATIONS


Solutions :

selector mode (with bypass : motorway by default and speed over 60 km/h)

GPS data (automatic)

Different defined limits :

Urban : 0C – 0.25C

Road : 0C – 1C

Motorway : 0C – 2C

breaking only SC!

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APPLICATIONS

LIMIT CURVES Motorway

-240

-180

-120

-60

0

60

120

180

240

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 102

0Time [s]

Cur

rent

[A]

0

40

80

120

160

200

240

280

320

Spe

ed [k

m/h

]

0C

2C

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APPLICATIONS

LIMIT CURVES Urban

-100

-50

0

50

100

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960

Time [s]

Cur

rent

[A]

0

20

40

60

80

100

120

Spe

ed [k

m/h

]

0 C

0,25 C

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APPLICATIONS

RESULTS

Motorway/road cycles : no significant direct gain (3,5 to 5% respectively @ 1C and 2C) but batteries less damaged (limited peaks of current)

Urban :

Direct energy gain : 17% @ 0.25C

More autonomy

Current in batteries nearly constant

Aging limited

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APPLICATIONS

RESULTS Urban efficiencies

50

55

60

65

70

75

80

85

90

95

100

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960

Time [s]

Effi

cien

cy [%

]

Batt. eff.

HESS eff.

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APPLICATIONS

RESULTS Urban delta efficiency

0

5

10

15

20

25

30

35

40

45

50

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960

Time [s]

Del

ta e

ffici

ency

[%]

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CONCLUSIONS

Autonomy improvement mainly in urban situation

Battery aging limited

Additionnal cost with supercapacitors but HESS is profitable considering all lifecycle

HEV : HESS suitable but downsizing limits gain

Challenge : real battery efficiency in dynamic conditions difficult to measure and to predict

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Thank you for your attention !

Documents

EVALUATION OF PERFORMANCES OF HYBRID ELECTRIC …€¦ · e applications – 3-3 1 evaluation of performances of hybrid electric energy storage system (li-ion batteries/ supercapacitors):