hybrid drive systems for vehicles - iea - lund university

Hybrid Drive Systems for Vehicles• L4

– Alternative drive train Components

© Mats Alaküla EHS

Drawback with conventional drivetrains• Limited ability to optimize

operating point

• No ability to regenerate braking power


Solutions• Smaller Engine

+ Reach higher operating points- Still cannot regenerate

• Store energy in the vehicle mass- Speed variations- Still cannot regenerate

• Secondary energy storage+ Selectable operating point (Pstorage

= Pice – Proad)

+ Can regererate- Expensive


Smaller Engine – cylinder deactivation


IC E EM

PEBatt

GEARClutch

DIFFIC E Clutch

0 200 400 6000

50

100

150

0 200 400 6000

50

100

150

0 200 400 6000

50

100

150

Combustion On Demand• Cylinder deactivation via free

valve control

• 4-stroke, 6-stroke, 8-stroke ...


Optimized efficiency

0200

400600

020

40

6080

0

0.05

0.1

0.15

0.2

0.25

0.3

Speed [rad/s]Torque [Nm] 0200

400600

020

40

6080

0

0.05

0.1

0.15

0.2

0.25

0.3

Speed [rad/s]Torque [Nm] 0200

400600

020

40

6080

0

0.5

1

1.5

2

Speed [rad/s]

Number of Cylinders in use

Torque [Nm]


Max efficiency

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 104

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

ICE Power [W]

Opt

imal

Effi

cien

cy

Blue=2-cylinder std, Red=2-cylinder COD


Secondary Energy Storage selection• Why electric?

– Efficient secondary energy converters (Electrical machines)

– Safe, quiet, flexible installation– Increasing need for Auxilliary electric

power– High torque density of Electrical

Mchines• Up to 30 Nm/kg• ICE: <2 Nm/kg


Secondary energy storage – Hybridisation


Energy Storage Systems

Industrial Electrical Engineering and Automation

How does a battery look?


Design criteria


Cost

OperationPerformance

Vehicle

Driving the Hybrid by the Atoms


Source: Uppsala University

Technologies


NiMHNiMH

Li-ionLi-ion S.C.S.C.

LeadLead

Limiting Factors


NiMHNiMHDurabilityWeightCost

Li-ionLi-ionCostSafety S.C.S.C.Energy

Initial Cost

LeadLeadCharge PowerDurability

WeightMaintenance

Performance


Pb-Acid

NiMH

Li-ion

Pow

er D

ensi

ty

Energy Density

S.C

Effpower

Battery Cell Properties


• All parameters are non-linear• Strong dependence on SOC,

temperature, current rate & direction, and history.

• OSV = Open Circuit Voltage• R0, R1, C1 describe the battery

resistance, charger transfer and “double layer effect”1

• R2, C2 describe the diffusion2 effect1) The first layer, the surface charge (either positive or

negative), consists of ions adsorbed onto the object due to chemical interactions. The second layer is composed of ions attracted to the surface charge via the Coulomb force, electrically screening the first layer. https://en.wikipedia.org/wiki/Double_layer_(surface_science)

2) Movement of Lithium ions

https://www.sciencedirect.com/science/article/pii/S0360544217317127#fig1

http://www.mdpi.com/1996-1073/9/6/444

Super Capacitor Cell PropertiesRohm = f(T, ω)

C = f(U, T, ω)

Terminal Voltage

+

-

Rleak = f(T)

L = f(T, ω)

Losses


– Fewer non-linear elements– Strong dependance on SOC & temperature only

”Semi” Steady-State Operation!

Combined Energy Storage System


SuperCaps

Ener

gy D

ensi

ty

Power Density

Combined SystemBattery

Driving Criteria Power output/regeneration at a specific time Charge and Discharge Properties Cooling Issues Pure Electric Range Upcoming energy need (GPS, weather and traffic

info, etc.)

Factors Determined by:State of Function = State of Charge + State of Health


State of Charge


Volta

ge

100% State of Charge 0%

Li-ion

NiMHS.C.

https://www.researchgate.net/figure/Discharge-curves-for-different-technologies-and-different-batteries_fig1_224395476

• C-rate = P[kW] / W[kWh]– C=1: 1 h full charge– C=2: 30 min full charge

State of Health• Temperature and Temperature Changes• Charge and Discharge Properties• Pure Electric Range• State of Charge• 200 - 500 individual cells in a battery

system– ALL need to be managed

• Management unit is needed– BMU (Battery Management Unit)


SAFT data

© Mats Alaküla EHS© Mats Alaküla

SAFT Lithium teknologi

© Mats Alaküla EHS© Mats Alaküla

Battery Lifetime : II• Calculate the total converted

energy as:Wconv=Wbatt*DoD/100*NoC

• And the battery cost per kWh converted energy as:SEKperkWh = CostPerkWh*Wbatt /

WconvCostPerkWh = 3000 [SEK]

Battery Lifetime : III

• Note! – The total converted energy falls fast with increased DoD !!!

• The cost per converted kWh increases rapidly with increased DoD

0 2 0 4 0 6 0 8 0 1 0 01 0 3

1 0 4

1 0 5

1 0 6

NoC

D e p th O f D is c h a rg e [% ]

0 2 0 4 0 6 0 8 0 1 0 01 0 0

1 0 1

1 0 2

1 0 3


Con

verte

d E

nerg

y [M

Wh]

0 2 0 4 0 6 0 8 0 1 0 00

0 .5

1

1 .5

2


Cos

t[SE

K/k

Wh]

Battery Lifetime : IV

1002,

batt

avech

W

tPDoD

• Assume that DoD is driven by a constant charge Power

• then… :

DoD

SOC

Pcharge Pch,ave

0 t

0

5

1 0

1 5

2 00 2 0 4 0 6 0 8 0 1 0 0

0

2

4

6

8

1 0

1 2

D o D [% ]

B a t te ry L ife t im e in Y e a rs , u s e d 8 h /d a y , 3 0 0 d a y s /y e a r

P c h ,a ve /W b a t t [ 1 /h ]

[yea

rs]

Battery Lifetime : V

NoC

WPDoD

NoCP

WDoDLifetime

W

tPDoD

batt

avech

avech

batt

batt

avech

100

2100

2

1002

,

,

,

• The battery lifetime can be calculated as:

• Now, plot the battery lifetime as a function of DoD and (Pch,ave/Wbatt)– Assume 8h/day, 300 days/year

Battery Lifetime: Conclusions• Deep discharge of a

battery costs lifetime– Best with less than 10 % DoD

• The battery may have a high power density BUT using it is expensive, i.e. a high power/energy ratio costs lifetime– Best with an average battery

power in the range 3…4 x the battery energy capacity.

Other technologies?Material Average Voltage Gravimetric Capacity

LiCoO2 3.7 V 140 mAh/g

LiMnO2 4.0 V 100 mAh/g

LiFePO4 3.3 V 120 mAh/g

Li2FePO4F 3.6 V 115 mAh/g

• Lithium batteries comes in a number of siblings– Lithium-Manganese Oxide or– Lithium Nickel Oxide or– Lithium Cobolt Oxide or– Lithium Iron Phosphate

• Most of these are considered thermally unsafe since the oxygen is easily released in case of cell abuse

• The only alternative, up to now, that is considered thermally stable is– Lithium Iron Phosphate– Watch :– http://www.valence.com/why-

valence/safety

Toshiba SCiB ?• New Lithium chemistry?• Toshiba calls it SCiB• Claims 90 % recharge in 5 minutes

and 5000 Cycles life• 90 % in 5 minutes means

(0.9/(5/60)) = 10.8 in Power/EnergyCapacity ratio.– A 10 kWh battery would be possible

to recharge with 108 kW charging power without damage …

• 2.4*4.2/1000/0.150 = 0.0672 kWh/kg … normal

Nominal Voltage 2.4 V

Nominal Capacity 4.2 Ah

Size Approx. 62 x 95 x 13mm

Weight Approx. 150 g

Toshiba vs LiFePo …

05

1 01 5

2 0 02 0

4 06 0

8 01 0 0

0

5

1 0

1 5

2 0

2 5

D o D [% ]

B a t te ry L ife t im e in Y e a rs , u s e d 8 h /d a y , 3 0 0 d a y s /y e a r

P c h ,a ve /W b a t t [ 1 /h ][y

ears

]

0 2 0 4 0 6 0 8 0 1 0 01 0

2

1 0 4

1 0 6

1 0 8

NoC


0 2 0 4 0 6 0 8 0 1 0 01 0 0

1 0 1

1 0 2

1 03


Con

verte

d E

nerg

y [M

Wh]

0 2 0 4 0 6 0 8 0 1 0 00

0 .5

1

1 .5

2


Cos

t[SE

K/k

Wh]

Battery simulation model : I


b a t ti

b a t te

b a ttR

ec hP a rg te rmP

lo s sP

term

echbatt

losstermech

battbattloss

batt

term

batt

batt

batt

battbatt

battbattbattbattbattbattbattbattterm

PP

PPPiRP

RP

Re

Rei

iRieiiReP

arg

arg

2

2

2

22

)(

Battery Simulation model : II


- 1 - 0 .5 0 0 .5 1

x 105

0

0 .2

0 .4

0 .6

0 .8

1

1 .2

1 .4

1 .6

1 .8

2B a tte r y c h ar g e e f f ic ie n c y

B at te ry p o we r [ W ]

Effic

ienc

y

Super Capacitors : I• Low voltage -> series connection


2

21

CC uCW

units unit

system

C

C

#

11

http://www.maxwell.com/products/ultracapacitors/industries/transportation

30 ton, 50 km/h = ½*m*v^2 = 0.82 kWh0.82/0.0023 = 355 kg

Supe Capacitors : II


Fly wheel energy storage• High speed rotating mass


2

21

wheelJW mech

• A flywheel made of steel and carbon fibre that rotated at over 60,000 RPM inside an evacuated chamber

• The flywheel casing featured containment to avoid the escape of any debris in the unlikely event of a flywheel failure

• The flywheel was connected to the transmission of the car on the output side of the gearbox via several fixed ratios, a clutch and a Continuously Variable Transmission

• 60 kW power transmission in either storage or recovery

• 400 kJ of usable storage• A total system weight of 25 kg

A l k i l f 13 li

hybrid drive systems for vehicles - iea - lund university

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