Comparison Between Fuel Cell andComparison Between Fuel Cell and Hydrogen Engine Fuel Consumption 

April 2008SAE 2008‐01‐0635

Aymeric Rousseau, Sylvain Pagerit,Thomas Wallner, Henning Lohse‐Busch

Sponsored by Lee Slezak (U.S. DOE)

This presentation does not contain any proprietary, confidential, or otherwise restricted information

Outline

PSAT Modeling Assumptions Vehicle

Fuel Cell System

H d E i Hydrogen Engine

Component Sizing

Si l ti R lt Simulation Results

Vehicle AssumptionsMidsize car platform Both non‐hybrid and hybrid configurations considered All vehicles achieve similar performances (0‐60mph, grade)All vehicles achieve similar performances (0 60mph, grade) All vehicles have same amount of onboard H2 (5kg) Component uncertainties taken into account UDDS and HWFET drive cycles considered

Parameter Unit Midsize Car

Ratios based on fuel economy gasoline equivalent using 2008 EPA corrections

Parameter Unit Midsize CarGlider Mass kg 990

Frontal Area m2 2.1

D C ffi i t 0 29

Parameter Unit Value0–60mph s 9 +/- 0.1

0–30mph s 3Drag Coefficient 0.29

Wheel Radius m 0.317

Rolling Resistance 0.008

0 30mph s 3

Grade at 60 mph % 6

Maximum Speed mph > 100 (1)

(1) Two gear transmission used for series(1) Two gear transmission used for series

Fuel Cell System AssumptionsParameter Unit Current Status FreedomCAR

GoalSpecific Power W/kg 500 650

0.7

Specific Power W/kg 500 650

Peak Efficiency % 55 60

d l

0.5

0.6

(%)

FreedomCAR2007 Status

Model Limitation:The efficiency curves used are steady‐state, underestimating the

0.3

0.4

Sys

tem

Effi

cien

cy ( underestimating the 

parasitic load, which is much higher in real‐world driving because of transient and non

Without CEM

0 10 20 30 0 00

0.1

0.2S

because of transient and non optimum controlWith Compressor Expander 

Module (CEM)

0 10 20 30 40 500

Fuel Cell Power (kW)

Hydrogen Engine Characteristics for C t T h l G t d f Current Technology Generated from Experimental Data Manufacturer  Ford Motor Co.

M d l 2 3L D t Model 2.3L Duratec

Cylinders 4

Bore 87.5 mm

Stroke 94 mm

Compression ratio 12

Valve train 4V DOHCValve train 4V DOHC

Speed range 6000 RPM

ModificationsSupercharger and intercooler– Supercharger and intercooler

– Hydrogen port fuel injection

– After‐market ECU4‐cylinder hydrogen engine setup

Port Injected Maps Generated for Different Air/Fuel RatiosAir/Fuel Ratios

Final Port Injected Map Generated To Maximize Brake Thermal EfficiencyMaximize Brake Thermal Efficiency

Brake thermal efficiency increases with increased i /f l iair/fuel ratio

Maximum torque decreases with increased air/fuel ratiowith increased air/fuel ratio

Due to lean operation peak efficiency is achieved at full l dload

Direct Injection Hydrogen Engine OperationEstimated from Single Cylinder Test Datag y

DI results in increased peak torque

Increased compression ratio & turbo charging

Hydrogen Direct Injection will increase the peak torque curve

Torque

Increased compression ratio will result in an increase in engine efficiency

Turbo-charging will increase the engine efficiency compared to supercharging

l d ll Lean part load operation will result in a further part load efficiency increase compared to throttled operation

SpeedLean part load

throttled operation

Component Average Power

140

160EngineFuel CellElectric Machine

100

120

r (kW

)

MC2 / GCBattery

Specific Power(W/kg)

80

100

onen

t Pow

er (W/kg)

40

60

Com

po

0

20

Conv Split Series ICE FC FC HEV

Vehicle Mass

1900

2000

Future vsCurrent vs. 

1800

1900

s (k

g)

Future vs. Future

Current

1700

le T

est M

ass

1500

1600

Vehi

cl

1400

1500

C S lit S i ICE FC FC HEVConv Split Series ICE FC FC HEV

2 5

Non-Hybrid Configurations Comparison

2.0

2.5 H2 ICE consumes between 1.7 and 2.1 times more than the fuel cell

1.5

mpt

ion

Rat

io

Future H2 ICE consumes between 1.6 h h f l ll

1.0

Fuel

Con

sum times more than the current fuel cell

0.5

F

0.0Conv FC

Current vs. current  ‐> H2 ICE will consume 1.7 more than fuel cellFuture vs. future  ‐> H2 ICE will consume 2.1 more than fuel cellCurrent fuel cell vs. future ICE ‐> H2 ICE will consume 1.57 more than fuel cell

Hybrid Configurations ComparisonH2 ICE consumes from 1 1 to 1 2 (Split) and 1 4 to 1 6

1 4

1.6

1.8 H2 ICE consumes from 1.1 to 1.2 (Split) and 1.4 to 1.6 times more than the fuel cell

Future H2 ICE Series consumes the same than current fuel cell HEV

1.0

1.2

1.4

ptio

n R

atio

same than current fuel cell HEV

0.6

0.8

Fuel

Con

sum

p

0.2

0.4

F

Future H2 ICE Split consumes less (0.8) than current fuel cell HEV 

0.0Split Series ICE FC HEV

Current vs. current  ‐> H2 ICE Split will consume 1.24 more than fuel cellFuture vs. future  ‐> H2 ICE Split will consume 1.1 more than fuel cellCurrent fuel cell vs. future ICE ‐> H2 ICE Split will consume 0.8 less than fuel cell

All Configurations Comparison

1 0

1.2Current Power split HEV is similar to Current Fuel Cell Only

0.8

1.0

Rat

io

Future series HEV is close to current Fuel Cell HEV

0.6

onsu

mpt

ion

0.4

Fuel

Co

0.0

0.2

Conv Split Series ICE FC FC HEV

Fuel Economy Results Analysis All HEVs configuration capture similar amount of energy at the 

wheel during deceleration (~98% on UDDS). However, the series fi ti h l d t l l t i hiconfigurations have more losses due to lower electric machine 

efficiencies than the power split.

Both HEV configurations using ICE have similar average efficiencies g g g(~31% for port injected and ~41.5% for direct injection on UDDS).

The fuel cell system average efficiency remains higher (~47% for d 51% f f UDDS)current case and ~51% for future case on UDDS).

In addition, the series configuration with H2‐ICE is penalized by the driveline inefficiencies (both generator ~90% and electric machinedriveline inefficiencies (both generator  90% and electric machine ~81%)

Conclusion

The DI H2‐ICE has been defined based on a combination of four‐cylinder and single cylinder data generated for different A/F ratios.

H2 ICE t i h ld b h b idi d t b titi ith f l ll H2‐ICE powertrain should be hybridized to be competitive with fuel cell systems vehicle fuel consumption.

Power split configuration offers the best fuel consumption when using H2‐ICE due to added inefficiencies in the series configuration.

If one considers that the current fuel cell system efficiencies will remain constant in the future (most research is focused on cost and durability),constant in the future (most research is focused on cost and durability), DI H2‐ICE could provide an interesting option (up to 20% reduction in fuel consumption).

If one considers both future technologies within an HEV a 10 to 40% If one considers both future technologies within an HEV, a 10 to 40% increase in fuel consumption is noticed when using H2‐ICE.