California Air 

Resources Board 

2009 ZEV Symposium

Keith Wipke, Sam Sprik, 

Jennifer Kurtz, Todd 

Ramsden1, John Garbak2

September 21, 2009

Cal/EPA, Sacramento, CA

NREL/PR-560-46736

National Fuel Cell Vehicle Learning 

Demonstration: Gen 2 Progress

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

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

1NREL, 2US Dept. of Energy

Session 2: 

Automotive Fuel Cell Vehicle Technologies
National Renewable Energy Laboratory 2 Innovation for Our Energy Future

Outline

• Project Objectives and Partners

• Overall Project Status

• Vehicle Analysis Results

• Infrastructure Analysis Results

• Summary
National Renewable Energy Laboratory 3 Innovation for Our Energy Future

Fuel Cell Vehicle Learning Demonstration 

Project Objectives and Targets

• Objectives

– Validate H2 FC Vehicles and Infrastructure in Parallel

– Identify Current Status and Evolution of the Technology

– Objectively Assess Progress Toward Technology Readiness 

– Provide Feedback to H2 Research and Development

Photo: NREL

Solar Electrolysis Station, Sacramento, CA

Performance Measure 2009 2015

Fuel Cell Stack Durability 2000 hours 5000 hours

Vehicle Range 250+ miles 300+ miles

Hydrogen Cost at Station $3/gge $2-3/gge

Key Project Targets
National Renewable Energy Laboratory 4 Innovation for Our Energy Future

Fuel Cell Vehicle Learning Demonstration 

Project Objectives and Targets

• Objectives

– Validate H2 FC Vehicles and Infrastructure in Parallel

– Identify Current Status and Evolution of the Technology

– Objectively Assess Progress Toward Technology Readiness 

– Provide Feedback to H2 Research and Development

Photo: NREL

Solar Electrolysis Station, Sacramento, CA

Performance Measure 2009 2015

Fuel Cell Stack Durability 2000 hours 5000 hours

Vehicle Range 250+ miles 300+ miles

Hydrogen Cost at Station $3/gge $2-3/gge

Key Project Targets

Under 

review
National Renewable Energy Laboratory 5 Innovation for Our Energy Future

Industry Partners: 

Four Automaker/Energy-Supplier Teams

Gen 1 Gen 1

Gen 1 & 2

Gen 2

Gen 2

Gen 1

Gen 2
National Renewable Energy Laboratory 6 Innovation for Our Energy Future

Vehicle Deployment Complete at 140 FCVs, 

Some Early Vehicles Retired

60

49

-

20 

40 

60 

80 

100 

120 

140 

160 

Cumulative Vehicles Deployed/Retired1

Vehicle Deployment by On-Board Hydrogen Storage Type

700 bar on-road

350 bar on-road

Liquid H2 on-road

700 bar retired

350 bar retired

Liquid H2 retired

Created Feb-23-2009 1:20 PM (1) Retired vehicles have left DOE fleet and are no longer providing data to NREL Created Aug-26-2009 4:21 PM

140

(1) Retired vehicles have left DOE fleet and are no longer providing data to NREL 
National Renewable Energy Laboratory 7 Innovation for Our Energy Future

0

5

10

15

20

25

30

35

Number of Vehicles

Total Vehicle Hours

Vehicle Hours: All OEMs, Gen 1 and Gen 2

In Service

Retired

Total Vehicle Hours = 100,284

Through 2009 Q2

Created: Aug-26-09 04:13 PM

0

5

10

15

20

25

30

35

40

45

Number of Vehicles

Total Vehicle Miles

Vehicle Miles: All OEMs Combined, Gen 1 and 2

In Service

Retired

Total Vehicle Miles Traveled = 2,318,038

Through 2009 Q2

Created: Aug-26-09 04:13 PM

DOE Learning Demo Fleet Has Surpassed 

100,000 Vehicle Hours and 2.3 Million Miles

Gen 2 vehicles make up most 

of 2nd bulge at low hours/miles

Some Gen 1 vehicles 

have now been retired 

(red bars)
National Renewable Energy Laboratory 8 Innovation for Our Energy Future

0

1

2

3

4

5

6

7

8

Delivered 

Compressed H2

Natural Gas On-site 

Reforming

Electrolysis Delivered Liquid H2

# of Stations

Production Technology

Infrastructure Hydrogen Production Methods 

Existing Stations

Retired Stations

Created Aug-27-09 1:03pm

0

5

10

15

20

25

Number of Stations

Reporting Period

Online Stations

Existing Stations

Retired Stations

Created Aug-27-09 1:03pm

Project Exploring 4 Types of Hydrogen Refueling 

Infrastructure: Delivered and Produced On-Site

Delivered Liquid, 700 bar 

Irvine, CA

Mobile Refueler

Sacramento, CA

Steam Methane Reforming

Oakland, CA

Water Electrolysis

Santa Monica, CA

Total of 115,000 kg H2

produced or dispensed

20

retired

retired
National Renewable Energy Laboratory 9 Innovation for Our Energy Future

Refueling Stations Test Performance in Various Climates; 

Learning Demo Stations Comprise ~1/3 of all U.S. Stations

Sep-14-2009

5

63

6

SF Bay Area DC to New York

7

Detroit Area

2

Orlando Area Los Angeles Area

17
National Renewable Energy Laboratory 10 Innovation for Our Energy Future

0 2 4 6 8 10 12 -30

-20

-10

0

10

20

30

40

50

60

1.4 % trips below 0 o

C

Max Op = 140.0 oF

Min Op = -5.8 oF

26.9 % trips above 28 o

C

Trip Frequency [%]

Temperature [

oC]

Average Ambient Trip Temperature: DOE Fleet

Created: Aug-14-09 4:47 PM

Average Ambient Temperature of Learning 

Demo Vehicles Spans Most Climates

Data distributed 

normally around 20 C

More time spent below 

freezing due to Gen 2 

freeze capability
National Renewable Energy Laboratory 11 Innovation for Our Energy Future

72 Public Composite Data Products Have Been Published; 

New Results and Updates Every 6 Months

A small subset of the 

72 latest results follow

Last Briefing to 

CARB Was 3 Years 

Ago with 24 Results
National Renewable Energy Laboratory 12 Innovation for Our Energy Future

0 10 20 30 40 50 60 70 80 90 100 0

10

20

30

40

50

60

Net System Power [%]

Efficiency [%]

Fuel Cell System1 Efficiency2

 Eff. at 25% Pwr Eff. at 100% Pwr

 ------------------- -------------------

Gen1 51 - 58% 30 - 54%

Gen2 53 - 59% 42 - 53%

DOE Target at 25% Power

DOE Target at 100% Power

Gen 1 Efficiency Range

Gen 2 Efficiency Range

Created: Sep-02-09 11:27 AM

1

 Gross stack power minus fuel cell system auxiliaries, per DRAFT SAE J2615. Excludes power electronics and electric drive.

2

 Ratio of DC output energy to the lower heating value of the input fuel (hydrogen). 

3

 Individual test data linearly interpolated at 5,10,15,25,50,75,and 100% of max net power. Values at high power linearly extrapolated 

 due to steady state dynamometer cooling limitations.

While Improving Durability and Freeze 

Capability, FC System Efficiency Stays High

Gen 2

Gen 1
National Renewable Energy Laboratory 13 Innovation for Our Energy Future

Dyno (1) Window-Sticker (2) On-Road (3)(4) 0

10

20

30

40

50

60

70

80

Fuel Economy (miles/kg H

2

)

Fuel Economy

 Gen 1

 Gen 2

Created: Aug-27-09 3:32 PM

(1) One data point for each make/model. Combined City/Hwy fuel economy per DRAFT SAE J2572.

(2) Adjusted combined City/Hwy fuel economy (0.78 x Hwy, 0.9 x City).

(3) Excludes trips < 1 mile. One data point for on-road fleet average of each make/model.

(4) Calculated from on-road fuel cell stack current or mass flow readings.

Ranges of Fuel Economy from Dynamometer 

and On-Road Data Slightly Improved for Gen 2
National Renewable Energy Laboratory 14 Innovation for Our Energy Future

Dyno Range (2) Window-Sticker Range (3) On-Road Range (4)(5) 0

50

100

150

200

250

300

Vehicle Range (miles)

Vehicle Range1

2015 Target

2009 Target

 Gen 1

 Gen 2

Created: Aug-27-09 3:32 PM

(1) Range is based on fuel economy and usable hydrogen on-board the vehicle. One data point for each make/model.

(2) Fuel economy from unadjusted combined City/Hwy per DRAFT SAE J2572.

(3) Fuel economy from EPA Adjusted combined City/Hwy (0.78 x Hwy, 0.9 x City).

(4) Excludes trips < 1 mile. One data point for on-road fleet average of each make/model.

(5) Fuel economy calculated from on-road fuel cell stack current or mass flow readings.

Driving Range for Gen 1 and Gen 2 Vehicles: 

Based on Fuel Economy and Usable H2

Gen 2 Vehicle Range Shows Significant 

Improvement from 700 bar Storage

250-mile 2008 

milestone met

Note: All Learning 

Demo Vehicles 

Based on Existing

Platforms
National Renewable Energy Laboratory 15 Innovation for Our Energy Future

Gen1 Gen2 Gen1 Gen2 Gen1 Gen2 0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

2006 Target

2009 Target

Actual Operating Hours Accumulated To-Date Projected Hours to 10% Voltage Degradation

Time (Hours)

DOE Learning Demonstration Fuel Cell Stack Durability:

Based on Data Through 2009 Q2

Max Hrs Accumulated (1)(2) Avg Hrs Accumulated (1)(3) Projection to 10% Voltage Degradation (4)(5)(6)

Max Projection

Avg Projection

Created: Sep-09-09 10:48 AM

(1) Range bars created using one data point for each OEM. Some stacks have accumulated hours beyond 10% voltage degradation.

(2) Range (highest and lowest) of the maximum operating hours accumulated to-date of any OEM's individual stack in "real-world" operation.

(3) Range (highest and lowest) of the average operating hours accumulated to-date of all stacks in each OEM's fleet.

(4) Projection using on-road data -- degradation calculated at high stack current. This criterion is used for assessing progress against DOE targets,

 may differ from OEM's end-of-life criterion, and does not address "catastrophic" failure modes, such as membrane failure.

(5) Using one nominal projection per OEM: "Max Projection" = highest nominal projection, "Avg Projection" = average nominal projection.

 The shaded projection bars represents an engineering judgment of the uncertainty on the "Avg Projection" due to data and methodology limitations. 

 Projections will change as additional data are accumulated.

(6) Projection method was modified beginning with 2009 Q2 data, includes an upper projection limit based on demonstrated op hours.

Gen 1 and Gen 2 Stack Operating Hours and 

Projected Time to 10% Voltage Drop

(DOE Milestone)

Gen 2 projections 

are early but 

encouraging

Some Gen 1 FC stacks 

have demonstrated >2000 

hours without repair
National Renewable Energy Laboratory 16 Innovation for Our Energy Future

0

5

10

15

20

25

30

35

40

45

Stack Count

Fuel Cell Stack Operation Hours: Gen1

Gen1

0-200

400600800

100012001400160018002000

Gen1 Hours >2000

32% of stacks in operation

In Op1

Retired2

Other3

0

5

10

15

20

25

30

35

40

45

Stack Count

Fuel Cell Stack Operation Hours: Gen2

Gen2

0-200

400600800

100012001400160018002000

Gen2 Hours >2000

65% of stacks in operation

In Op1

Retired2

Other3

Created: Sep-09-09 10:48 AM

1) Stack currently accumulating hours

2) Stack removed for low performance

3) Stack not currently accumulating hours, but not removed because of low performance

Fuel Cell Stack Operation Hours; Early in 

Gen 2 Life, But Results Encouraging

Very Few Gen 2 

Stacks Retired Due to 

Low Performance;

Most Still in Operation

Many Gen 1 Stacks 

Retired with <400 

Hours; Some with 

Very High Hours
National Renewable Energy Laboratory 17 Innovation for Our Energy Future

30

40

50

60

70

80

90

100

110

120

130

 0 100 200 300 400 500 600 700 800 900 10001100120013001400150016001700180019002000

Stack Op Hour Segments(2)

% Power(1)

Max Fuel Cell Power Loss vs Op Hours: Gen1

1) Normalized by fleet median value at 200 hours.

2) Each segment point is median FC power (+-50 hrs).

 Box not drawn if fewer than 4 points in segment.

Gen1 Data Range

25th & 75th Percentiles

Group Median

Outlier

Created: Sep-09-09 10:48 AM

Max Fuel Cell Power Degradation – Gen 1

Note that 

degradation 

flattens out after 

~200 hours

Need ~1000 

hours to see 

degradation 

curve flatten out
National Renewable Energy Laboratory 18 Innovation for Our Energy Future

30

40

50

60

70

80

90

100

110

120

130

 0 100 200 300 400 500 600 700 800 900 10001100120013001400150016001700180019002000

Stack Op Hour Segments(2)

% Power(1)

Max Fuel Cell Power Loss vs Op Hours: Gen2

1) Normalized by fleet median value at 200 hours.

2) Each segment point is median FC power (+-50 hrs).

 Box not drawn if fewer than 4 points in segment.

Gen2 Data Range

25th & 75th Percentiles

Group Median

Outlier

Created: Sep-09-09 10:48 AM

Max Fuel Cell Power Degradation – Gen 2

From limited Gen 2 data 

received so far, trend of 

flattening after 200 

hours appears similar

Too early to tell how much 

flatter the tail will be
National Renewable Energy Laboratory 19 Innovation for Our Energy Future

0-200 400 600 800 1000 1200 1400 1600 1800 2000 >2000 0

5

10

15

20

25

30

27% Gen1 > 2000 projected hrs

9% Gen2 > 2000 projected hrs

Projected Hours

% Stacks

Durability: Projected Hours to Low Fuel Cell Power Limit

Gen1 (> 200 operation hrs)

Gen1 (< 200 operation hrs)

Gen2 (> 200 operation hrs)

Gen2 (< 200 operation hrs)

Created: Sep-09-09 10:48 AM

1. Low fuel cell power limit is dependent on the fuel cell vehicle system and is unique to each company in this Learning Demonstration.

2. Acceptable low vehicle performance limit will be determined by retail customer expectations.

3. Power projection method based on the voltage degradation techniques, but uses max fuel cell power instead of voltage at a specific

high current.

4. Stacks with less than 200 operation hours are in separate groups because the projection is based on operation data and with operation

hours greater than 200 the degradation rate tends to flatten out.

Projected Hours to OEM Low Power 

Operation Limit

Projections based 

on OEM power 

limits will improve 

with more hours
National Renewable Energy Laboratory 20 Innovation for Our Energy Future

Fuel Cell System (including H2 storage) 

Close to 2010 and 2015 W/L and W/kgTargets

0

50

100

150

200

250

300

350

400

Power Density (W/L)

FC System (Including Hydrogen Storage) Power Density (W/L)

2010 and 2015 FreedomCAR Research Goal1

 Gen 1

 Gen 2

Created: Sep-08-09 10:32 AM (1) Fuel cell system includes fuel cell stack, BOP and H2 stroage, but excludes power electronics, battery storage, and electric drive.

0

50

100

150

200

250

300

350

400

Specific Power (W/kg)

FC System (Including Hydrogen Storage) Specific Power (W/kg)

2010 and 2015 FreedomCAR Research Goal1

 Gen 1

 Gen 2

Created: Aug-28-09 8:42 AM (1) Fuel cell system includes fuel cell stack, BOP and H2 storage, but excludes power electronics, battery storage, and electric drive.

Significant Improvements 

Seen in Specific Power 

(...systems getting lighter)

Power Density Held Similar 

Between Gen 1 and Gen 2 

(...same size or larger) Gen 1

Gen 1 Gen 2

Gen 2
National Renewable Energy Laboratory 21 Innovation for Our Energy Future

0 2 4 6 8 10 12 14 16 18 20 0

500

1000

1500

2000

2500

3000

Time (min)

Number of Fueling Events

Histogram of Fueling Times

All Light Duty Through 2009Q2

Average = 3.26 min

86% <5 min

 2006 MYPP Tech Val Milestone (5 kg in 5 min at 350 bar)

 2012 MYPP Tech Val Milestone (5 kg in 3 min at 350 bar)

Created: Aug-14-09 10:40 AM

Refueling Times are Short; Amounts are 

Reflective of Demonstration-Sized Systems

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0

100

200

300

400

500

600

700

800

900

Amount Fueled (kg)

Number of Fueling Events

Histogram of Fueling Amounts

All Light Duty Through 2009Q2

Average = 2.14 kg

Created: Aug-14-09 10:40 AM

Average 

Refueling Time is 

3.26 minutes

Average 

Refueling Amount 

is 2.14 kg
National Renewable Energy Laboratory 22 Innovation for Our Energy Future

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

500

1000

1500

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

All Light Duty Through 2009Q2

5 minute fill of

5 kg at 350 bar

3 minute fill of

5 kg at 350 bar

21854 Events

Average = 0.78 kg/min

24% >1 kg/min

2006 MYPP Tech Val Milestone

2012 MYPP Tech Val Milestone

Created: Aug-14-09 10:09 AM

Actual Vehicle Refueling Rates from 21,000 

Events: Measured by Stations or by Vehicles

Average rate = 0.78 kg/min

24% of refueling events 

exceeded 1 kg/min

All Fills
National Renewable Energy Laboratory 23 Innovation for Our Energy Future

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

50

100

150

200

250

300

350

400

450

500

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

All Light Duty by Year Through 2009Q2

5 minute fill of

5 kg at 350 bar

3 minute fill of

5 kg at 350 bar

Year Avg (kg/min) %>1 

------- ----------------- -------

2005 0.66 16%

2006 0.74 21%

2007 0.81 26%

2008 0.77 23%

2009 0.79 26%

2005

2006

2007

2008

2009

2006 MYPP Tech Val Milestone

2012 MYPP Tech Val Milestone

Created: Aug-14-09 3:32 PM

Refueling Rates by Year: ~1/4 Now Exceed 1 

kg/min, 2009 to be Highest # of Fills

Comparison 

by Year

2008

2007

2006

2005

2009

(first 1⁄2 year)
National Renewable Energy Laboratory 24 Innovation for Our Energy Future

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

200

400

600

800

1000

1200

1400

1600

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

Comm vs Non-Comm Fills - All Light Duty Through 2009Q2

5 minute fill of

5 kg at 350 bar

3 minute fill of

5 kg at 350 bar

Fill Type Avg (kg/min) %>1 

------------- ------------------ -------

Comm 0.92 36%

Non-Comm 0.66 13%

Comm

Non-Comm

2006 MYPP Tech Val Milestone

2012 MYPP Tech Val Milestone

Created: Sep-02-09 11:32 AM

Non-Comm Has a 2nd

Peak at ~0.2 kg/min

Comm Fills Can

Achieve Higher

Fill Rates

Communication H2 Fills Achieving 39%

Higher Average Fill Rate than Non-Communication

Comm.

Non-Comm.

Comparison 

by Comm.
National Renewable Energy Laboratory 25 Innovation for Our Energy Future

0

100

200

300

400

500

600

700

WTW GHG Emissions (g CO2-eq/mi)

Learning Demonstration Fuel Cycle Well-to-Wheels Greenhouse Gas Emissions1

Baseline Conventional Mid-Size Passenger Car2

Baseline Conventional Mid-Size SUV2

Average WTW GHG Emissions (Learning Demo)

Minimum WTW GHG Emissions (Learning Demo)

WTW GHG Emissions (100% Renewable Electricity)

WTW GHG Probability Based on Learning Demo3

Created: Sep-08-09 4:21 PM

On-Site Natural Gas Reforming On-Site Electrolysis(4)

1. Well-to-Wheels greenhouse gas emissions based on DOE's GREET model, version 1.8b. Analysis uses default GREET values except for FCV fuel economy, hydrogen

production conversion efficiency, and electricity grid mix. Fuel economy values are the Gen 1 and Gen 2 window-sticker fuel economy data for all teams (as used in CDP #6);

conversion efficiency values are the production efficiency data used in CDP #13.

2. Baseline conventional passenger car and light duty truck GHG emissions are determined by GREET 1.8b, based on the EPA window-sticker fuel economy of a conventional

gasoline mid-size passenger car and mid-size SUV, respectively. The Learning Demonstration fleet includes both passenger cars and SUVs.

3. The Well-to-Wheels GHG probability distribution represents the range and likelihood of GHG emissions resulting from the hydrogen FCV fleet based on window-sticker fuel

economy data and monthly conversion efficiency data from the Learning Demonstration.

4. On-site electrolysis GHG emissions are based on the average mix of electricity production used by the Learning Demonstration production sites, which includes both

grid-based electricity and renewable on-site solar electricity. GHG emissions associated with on-site production of hydrogen from electrolysis are highly dependent on

electricity source. GHG emissions from a 100% renewable electricity mix would be zero, as shown. If electricity were supplied from the U.S. average grid mix, average GHG

emissions would be 1245 g/mile.

Learning Demonstration Vehicle Greenhouse Gas Emissions 

Using Actual Production Efficiencies and Fuel Economies

H2 FCVs Offer 

Significant Reduction 

of GHGs, even from 

Natural Gas Ref.

Electrolysis Reformation
National Renewable Energy Laboratory 26 Innovation for Our Energy Future

Summary

• Learning Demo evaluation is ~80% complete

– 140 vehicles and 20 stations deployed

– 2.3 million miles traveled, 115,000 kg H2 produced or dispensed

– 346,000 individual vehicle trips analyzed

– Project to continue through 2010

• Emphasis from project has been on providing maximum 

value from the data collected during project

– 72 results have been published

– Updates every 6 months

– Current results are always available on our web page

• Vehicle/Station Status

• 2nd generation vehicles have now been on road for >1 year

• Station deployment nearing completion; some early stations retired

• Similar Evaluations Now Underway at NREL for FC Forklifts 

& Backup Power
National Renewable Energy Laboratory 27 Innovation for Our Energy Future

Questions and Discussion

All public Learning Demo and FC Bus Evaluation papers and presentations are available 

online at http://www.nrel.gov/hydrogen/proj_tech_validation.html

Primary Contact: Keith Wipke, National Renewable Energy Lab

303.275.4451 keith.wipke nrel.gov @

The NREL Learning 

Demo Analysis 

Team in Colorado
National Renewable Energy Laboratory 28 Innovation for Our Energy Future

Additional Results for Reference
National Renewable Energy Laboratory 29 Innovation for Our Energy Future

12 hr Equilibrium 12 hr Equilibrium 0

100

200

300

400

500

600

Time to Drive Away Time to Max FC Power

Time [s]

Fuel Cell Vehicle Start Time from Sub-Freezing Soak Condition1

Created: Sep-08-09 10:54 AM

(1) Learning Demo soak temperature for freeze tests were between -9 and -20 oC

(2) 2010 & 2015 DOE MYPP Cold Start Up Time Target: 30 seconds to 50% of rated power from -20 o

C (soak duration not specified).

Fuel Cell Start Times from 

Sub-Freezing Soak Conditions

Some FC Systems Today 

Would Meet Customer Cold 

Startup Expectations;

Improvements Ongoing
National Renewable Energy Laboratory 30 Innovation for Our Energy Future

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

500

1000

1500

2000

2500

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

350 vs 700 bar Fills - All Light Duty Through 2009Q2

5 minute fill of

5 kg at 350 bar

3 minute fill of

5 kg at 350 bar

Fill Type Avg (kg/min) %>1 Count

------------- ------------------ ------- --------

350 bar 0.82 29% 17847

700 bar 0.62 3% 3792

350 bar

700 bar

2006 MYPP Tech Val Milestone

2012 MYPP Tech Val Milestone

Created: Aug-31-09 12:59 PM

Comparison of Fueling Rates for 

350 and 700 bar Pressure Fueling Events

700 bar fills are currently 27% 

slower than 350 bar fills

350 bar

700 bar

Comparison 

by Pressure
National Renewable Energy Laboratory 31 Innovation for Our Energy Future

10 15 20 25 30 0

200

400

600

800

1000

1200

1400

1600

1800

2000

Fuel Cell Stack Projected Hours as a Function of Voltage Drop

% Voltage Drop

Projected Hours

2,3

Gen 1 Average Projections

Gen 1 Average Projection to 10% Voltage Degradation1

Gen 2 Average Projections

Gen 2 Average Projection to 10% Voltage Degradation1

Created: Sep-11-09 8:57 AM

(1) 10% Voltage degradation is a DOE metric for assessing fuel cell performance.

(2) Projections using on-road data -- degradation calculated at high stack current.

(3) Curves generated using the Learning Demonstration average of each individual fleet average at various voltage degradation levels.

(4) The projection curves display the sensitivity to percentage of voltage degradation,

 but the projections do not imply that all stacks will (or do) operate at these voltage degradation levels.

(5) The voltage degradation levels are not an indication of an OEM's end-of-life criteria and do not address catastrophic stack 

 failures such as membrane failure.

(6) All OEM Gen 2 average fleet projections are higher than Gen1 projections, however due to less operation data for Gen 2,

 these projections are limited by demonstrated operation hours to minimize extrapolations.

10% Voltage Drop Is One Metric –

Sensitivity of Projections to % Voltage Drop

Gen 2 average fleet projections 

are actually higher than Gen 1 

projections, however due to less 

operation data for Gen 2, 

these projections are limited by 

demonstrated hours to minimize 

extrapolations