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Energy Storage System Requirements forEnergy Storage System Requirements for Fuel Cell Vehicles
October 2004
A i RAymeric RousseauPhil Sharer
Rajesh AhluwaliaArgonne National LaboratoryArgonne National Laboratory
Sponsored by Lee Slezak (U.S. DOE)
This presentation does not contain any proprietary, confidential, or otherwise restricted information
Fuel Cell Vehicle Fuel Economy OptimumOptimum Study Scope
Hybridization Degree
Energy Storage Technology
Control Strategy
Perspectives
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FreedomCAR FCV Energy Storage Proposed Goals Spring 2003 Proposed Goals Spring 2003
FreedomCAR Goals Low Power High Power Characteristics Units Energy Storage Energy Storage
Pulse Discharge Power (10s) kW 25 50 M R P l (5 ) kW 30 60Max Regen Pulse (5s) kW 30 60Total Available Energy kWh 1.5 3 Round Trip Efficiency % >90 >90 Cycle Life Cyc. TBD (15 year life equiv.) TBD (15 year life equiv.)Cold-start at -30°C (TBD kW for TBD min.) kW 5 5Cold start at 30 C (TBD kW for TBD min.) kW 5 5Calendar Life Yrs 15 15 Max Weight kg 40 65 Max Volume liters 32 50 Production Price @ 100k units/yr $ 500 1,000 M i O ti V lt Vd </ 440 </ 440Maximum Operating Voltage Vdc </= 440 max </= 440 maxMinimum Operating Voltage Vdc >/= 0.5 x Vmax >/= 0.5 x Vmax Maximum Self Discharge Wh/d 50 50 Operating Temperature °C -30 to +52 -30 to +52 Survival Temperature °C -46 to +66 -46 to +66
3
p
Structure of the Study
Hybridization HotCurrent FCHybridizationDegrees
FUDS
ESSSUV Mid-Term FC FHDS AmbESSTechnologies
C t lCar Future FC US06 ColdControlStrategies
4
Fuel Cell HEV ConfigurationFuel Cell HEV Configuration
DC Link
5
Major AssumptionsMajor Assumptions Vehicle and Performance
– Mid‐size SUV (Explorer, Durango, Blazer)– Target 0‐60 mph acceleration in 10.2 s – 55 mph at grade of 6.5% continuous (a least 20 minutes) – Top speed of 100 mph
Fuel Cell System Requirements Fuel Cell System Requirements – Fuel cell should be sized to provide a least power for top speed and grade
performance– FCS must have 1‐s transient response time for 10% to 90% power.p p– FCS should reach maximum power in 15 s for cold start from 20C ambient
temperature and in 30 s for cold start from ‐20C ambient temperature Power Requirements (based on PSAT simulations)
160kW k f 0 60 h l i– 160kW peak power for 0‐60 mph acceleration– Minimum fuel cell power of 80kW for achieving speed at 6.5% grade
Default: tight SOC control, lithium‐ion, FUDS
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Detailed Models Necessary for l hRealistic Behavior
(%)
ffici
ency
Fuel Cell System Efficiencyyste
m E
ff
Fuel Cell System Efficiency is Not a Monotonic Function of Power Demand
l Cel
l Sy
Fuel
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Power Demand (kW)
Design-Specific FC System Modeling R i d t A C t I tRequired to Assess Component Impact
Process Water
Coolant
Electric Motor
Hydrogen Tank
Humidified Air
Humidifier Heater
PEFCStack
Humidified Hydrogen
Demister
Radiator & Condenser
Fan
AirExhaust
Radiator & Condenser
W t T kCondensate
Pump
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Compressor/Motor/ExpanderWater Tank Pump
Small Differences in Components Can lHave Large System Implications
(%)
ffici
ency
ys
tem
Eff
l Cel
l Sy
Fuel
9
Power Demand (kW)
Design-Specific Models Required for Realistic FC Cycle EfficiencyRealistic FC Cycle Efficiency
64.5
cy (%
)
FUDS Cycle
63 5
64
ency
(%)
Effic
ienc
63
63.5
Cyc
le E
ffici
em
Cyc
le E
62
62.5
Cel
l Sys
tem
Cl S
yste
m
61
61.5Fuel
CFu
el C
ell
10
61FC HEV 140kW FC HEV 120kW FC HEV 100kW FC HEV 80kW
F
Increase in Hybridization Degree Can Lead to Decrease in Fuel EconomyLead to Decrease in Fuel Economy
65
mpg
e)
50*37.5*
25*FUDS Cycle
60
. (m
pge)
e Eq
. (m
12.5*
55
Gas
olin
e Eq
.G
asol
ine
50
el E
cono
my
Gco
nom
y
0*
40
45Fue
Fuel
Ec
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*Hybridization Degree
40FC HEV 160kW FC HEV 140kW FC HEV 120kW FC HEV 100kW FC HEV 80kW
Because the Regen Energy Increase is Nullified by the FC Efficiency Decrease
84.590 FC system effPercentage regen braking
FUDS Cycle
Nullified by the FC Efficiency Decrease
64.0 63.660.9 63.0
72.2
62.270
80
38.550
60
20
30
40
0
10
20
12
0FC HEV 140kW FC HEV 120kW FC HEV 100kW FC HEV 80kW
Optimum Hybridization Degree d h h l
62.5
63
ge)
Depends upon the ESS Technology
mpg
e) FUDS Cycle
61.5
62
ne E
q (m
pg
Li-ione Eq
. (m
60
60.5
61
my
Gas
olin
Li ionNiMHUltracap
Gas
olin
e
59
59.5
60
el E
cono
mco
nom
y
58
58.5
140 120 100 80
Fue
Fuel
Ec
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Fuel Cell Power (kW)
Numerous Control Strategies Options Were Considered Were Considered Use the fuel cell as main power source
– SOCtarget = 0.7g• Min fuel cell power demand = 0 (Default Control)
• Min fuel cell power demand = 5kW different ways to increase
• Min fuel cell power demand = 15kW
– SOCtarget = 0.5• Min fuel cell power demand = 0
to increase SOC window
• Min fuel cell power demand = 0
• Min fuel cell power demand = 15kW
Use the battery as main power source
– SOCtarget = 0.7
– SOCtarget = 0.5
With i f l ll d d P h l + P(SOC)14
With min fuel cell power demand = Pwheel + P(SOC)
Default Control Strategy Maximizes Fuel Cell System Usey
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Smaller Target SOC (0.5) Leads to Fuel Economy Benefits
59.360
Fuel Economy Benefits
mpg
e) FUDS Cycle
57 3
58.159
Eq. (
mpg
e)e
Eq. (
m
57.3
56.557
58
Gas
olin
e E
Gas
olin
e
56
Econ
omy
Gco
nom
y
54
55
Fuel
EFu
el E
c
16
SOC = 0.7; Pfcmin=0
SOC = 0.5; Pfcmin=0
SOC = 0.7; Pfcmin=15kW
SOC = 0.5Pfcmin=15kW
US06 Cycle Could Benefit From Using More The Battery
57.5
80kW
ym
pge)
56.5
57
on (m
pg) 80kW
100kW FC120kW FC
e Eq
. (m
55.5
56
Com
paris
oG
asol
ine
54.5
55
Econ
omy
Cco
nom
y
53 5
54
54.5
Fuel
EFu
el E
c
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53.5FC main source - SOC = 0.7 ESS main source - SOC = 0.7
System Approach is Needed to Achieve Optimum Fuel EconomyOptimum Fuel Economy
• Key benefit of hybridization is fuel economy increase for FUDS thanks to regenerative brakingthanks to regenerative braking
• Optimum hybridization degree is energy storage technology dependant
• Fuel cell system efficiency and regenerative braking trade‐off is key to optimum fuel economy‐ Increasing hybridization degree and SOC window can lowerIncreasing hybridization degree and SOC window can lower fuel economy
‐ Minimizing SOC target is a good way to increase the regenerative brakingregenerative braking
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Aymeric Rousseau arousseau@anl govAymeric Rousseau [email protected] Sharer [email protected] Ahluwalia [email protected]
Transportation website www.transportation.anl.gov
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