Fuel Cells Durability & 

Performance

Jennifer Kurtz, Keith Wipke, 

Sam Sprik, Todd Ramsden

December 8, 2009

Alexandria, VA

NREL/PR-560-47279

Analysis of Real World Fuel Cell 

Degradation

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.
National Renewable Energy Laboratory 2 Innovation for Our Energy Future

Fuel Cell Durability Analysis

FC Applications

Objectives

FC Durability Analysis

Results

Summary
National Renewable Energy Laboratory 3 Innovation for Our Energy Future

Government Funded Fuel Cell Sites by Application

Many site locations to be determined.

Quantity and sites are subject to change.

Project partners include DOE, 

DoD, FTA, FC developers, H2

suppliers, and end users
National Renewable Energy Laboratory 4 Innovation for Our Energy Future

HSDC: FC Vehicle Summary

Gen 1

Gen 2

Gen 1

Gen 1 & 2

Since 2005, continued into 2010

140 Vehicles and 20 H2 Stations

2.3 million miles traveled

115,000 kg H2 produced or dispensed

346,000 individual trips analyzed
National Renewable Energy Laboratory 5 Innovation for Our Energy Future

2009 Q1 2009 Q2 2009 Q3 2009 Q4 2010 Q1 2010 Q2 2010 Q3 2010 Q4 2011 Q1 0

200

400

600

800

1000

1200

1400

FC Count

Install Quarter

Government Funded Early Market Fuel Cell Count

Projected Quantities Subject to Change

DoD Forklift

ARRA Forklift

IAA Backup

ARRA Backup

ARRA Stationary

Created: Nov-12-09 4:40 PM

HSDC: FC Early Market Summary

1000
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HSDC: FC Bus Summary

8 FCBs in transit service at 4 sites (since 2004)

> 325,000 miles & > 31,000 hours

> 78,000 kg of H2 dispensed

Planned new projects: 24 buses, 8 different 

transit agencies (states: CA, CT, NY, SC)
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Analysis Objectives

General

• Independent FC & H2 technology assessment

• Establish baseline of real world FC 

demonstrations

• Support FC & H2 market growth

• Report on technology status & progress to 

stakeholders (R&D, FC & H2 developers, end 

users)

Durability

• Analyze FC durability

• Measure FC durability against targets

• Investigate factors affecting durability
National Renewable Energy Laboratory 9 Innovation for Our Energy Future

1) Data templates are created for each different application/report and are 

common to all partners in an application.

2) Data exchange may happen more frequently based on data, analysis, & 

collaboration

3) Results published via NREL Tech Val website, conferences, and reports

Data Flow

CDPs every 6 

months3

DDPs every 6 months2; 

used for CDP review

Internal analysis 

completed quarterly

Bundled data1 delivered 

to NREL quarterly

CDPs

Project Team

Partner/Site

Operation Data

NREL HSDC

Data Processing & Analysis

Results

Data Products

Evaluating secure data transfer options 

such as mail and secure FTP
National Renewable Energy Laboratory 10 Innovation for Our Energy Future

72 Public Composite Data Products Have Been Published; 

New Results and Updates Every 6 Months

2005 - 16 CDPs 

Planned
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Improved Method for Calculating Projected Time to 10% 

Voltage Drop for Stack and Fleet

1

1. FC Stack voltage & current polarization fit 

Note, 10% voltage drop is a DOE 

target/metric, not an indicator of end-of-life

Consistent analysis method applied to all data
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0 200 400 600 800 1000 1200 1400 1600 1800 2000 220

230

240

250

260

270

280

290

300

Op Hours

Voltage

Voltage vs. Operation Hours at 300A: Vehicle19-Stack1 871 847 900

288

259

0

0.2

0.4

0.6

0.8

1

Stack Weight Factors

Weight Value

Overall

DatQty

DatGap

DR1ciDR2ci

Created: Oct-09-08 3:01 PM

warm-up time=10 min

pwr rate filt=1000 kW/s

amp rate filt=1000 A/s

pts per fit=2500

1 data pt every 1seconds

2

2. FC Stack voltage decay estimate using 

robust, improved segmented linear fit

instead of linear fit (follows non-linear 

decay trends & early voltage decay)

Improved Method for Calculating Projected Time to 10% 

Voltage Drop for Stack and Fleet

1

1. FC Stack voltage & current polarization fit 

Note, 10% voltage drop is a DOE 

target/metric, not an indicator of end-of-life

Consistent analysis method applied to all data
National Renewable Energy Laboratory 13 Innovation for Our Energy Future

0 200 400 600 800 1000 1200 1400 1600 1800 2000 220

230

240

250

260

270

280

290

300

Op Hours

Voltage

Voltage vs. Operation Hours at 300A: Vehicle19-Stack1 871 847 900

288

259

0

0.2

0.4

0.6

0.8

1

Stack Weight Factors

Weight Value

Overall

DatQty

DatGap

DR1ciDR2ci

Created: Oct-09-08 3:01 PM

warm-up time=10 min

pwr rate filt=1000 kW/s

amp rate filt=1000 A/s

pts per fit=2500

1 data pt every 1seconds

2

2. FC Stack voltage decay estimate using 

robust, improved segmented linear fit

instead of linear fit (follows non-linear 

decay trends & early voltage decay)

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Vehicle12 Stack1

Vehicle15 Stack1

Vehicle17 Stack1

Vehicle19 Stack1

Vehicle16 Stack2

EcoCars

EcoCars: Stack OpHr Projections

Op Hrs

Stack

FleetWgtAve

OpTime

0 0.2 0.4 0.6 0.8

Vehicle12 Stack1

Vehicle15 Stack1

Vehicle17 Stack1

Vehicle19 Stack1

Vehicle16 Stack2

EcoCars: Stack Weights

Weight

Created: Oct-09-08 1:20 PM Stacks sorted by Stack Weight

3

Fleet

Stack

3. Fleet weighted average using FC Stack 

operating hour projections and weights 

(based on data and confidence in fit)

Improved Method for Calculating Projected Time to 10% 

Voltage Drop for Stack and Fleet

1

1. FC Stack voltage & current polarization fit 

Note, 10% voltage drop is a DOE 

target/metric, not an indicator of end-of-life

Consistent analysis method applied to all data
National Renewable Energy Laboratory 14 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

2000
National Renewable Energy Laboratory 15 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

10% V Drop = DOE Metric

10

Projections are limited by 

demonstrated hours to minimize 

extrapolations

Gen 2 Hours < Gen 1 Hours
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

A few with very 

high hours

Many retired with 

< 400 hours

Very few retired

Most still in operation
National Renewable Energy Laboratory 17 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

Low operation hours = 

uncertainty in projection

Limit is system and 

user dependent
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: 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
National Renewable Energy Laboratory 19 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

Low operation hours = 

uncertainty in projection
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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

Degradation flattens out 

after ~200 hours

Low operation hours = 

uncertainty in projection

At ~1000 hours, the 

primary degradation 

trend can be observed
National Renewable Energy Laboratory 21 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

Low operation hours = 

uncertainty in projection
National Renewable Energy Laboratory 22 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

Low operation hours = 

uncertainty in projection

Trend appears to follow Gen 1 

trend of a change in degradation 

rate around 200 hours, but 

prediction of degradation after 200 

hours difficult because of low 

hours
National Renewable Energy Laboratory 23 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

Low operation hours = 

uncertainty in projection

Trend appears to follow Gen 1 

trend of a change in degradation 

rate around 200 hours, but 

prediction of degradation after 200 

hours difficult because of low 

hours
National Renewable Energy Laboratory 24 Innovation for Our Energy Future

Operation Trends for Degradation 

Factors

• Determination and/or prediction of the end of stack 

operation difficult to predict because of many 

influencing factors

• Stack degradation varies between and within fleets. 

Possible explanations could be: 

• Variation of stack operation hours

• Variation in stack system (e.g. manufacturing of cells)

• Variation in operation

• Many CDPs identify trends for operation and are also 

used for a more detailed investigation of factors 

affecting degradation

• CDP shows overall trends and outliers

• Detailed data shows fleet and individual stack trends
National Renewable Energy Laboratory 25 Innovation for Our Energy Future

0-5 10 15 20 25 30 35 40 >40 0

5

10

15

20

25

30

Stack Count

% FC Power Drop

FC Power Drop During Operation Period: Gen1

Gen1

68% of In Op stacks

have > 10% power drop

In Op1

Retired2

Other3

0-5 10 15 20 25 30 35 40 >40 0

5

10

15

20

25

30

Stack Count

% FC Power Drop

FC Power Drop During Operation Period: Gen2

Gen2

95% of In Op stacks

have > 10% power drop

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

Power Drop During Fuel Cell Stack Operation 

Period

Many external factors
National Renewable Energy Laboratory 26 Innovation for Our Energy Future

0

5

10

15

20

25

Operating Time [%]

Operating Time at Fuel Cell Stack Voltage Levels: DOE Fleet

<50%

50-55%

55-60%

60-65%

65-70%

70-75%

75-80%

80-85%

85-90%

90-95%

95-100%

>100%

% Max Fuel Cell Stack Voltage

All time

Time at low current

Created: Aug-14-09 4:47 PM

Fuel Cell Voltage & Low Current Op Time

Majority of operation time 

spent at high voltage and 

low current (~OCV)
National Renewable Energy Laboratory 27 Innovation for Our Energy Future

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 >8 0

5

10

15

20

25

30

Segmented Trips/Hour Histogram: DOE Fleet

Trips/Hour*

Frequency [%]

*Trips/Hour based on 50 hour segments

spanning stack operating period Created: Aug-26-09 2:14 PM

Fuel Cell Stack Trips Per Hour Histogram

The number of trips per hour 

demonstrated in the field may be 

different than start/stop testing
National Renewable Energy Laboratory 28 Innovation for Our Energy Future

0

2

4

6

8

10

12

14

HWFET CycleUS06 CycleUDDS Cycle1015 Cycle

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Percent Idle in Trip

% Idle

Trip Frequency [%]

Created: Sep-08-09 3:29 PM

Percent Idle in Trip with Comparison to 

Standard Drive Cycles 

Comparison of field data with 

Std Drive Cycles that may be 

used in testing fuel cells
National Renewable Energy Laboratory 29 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 oC

Max Op = 140.0 oF

Min Op = -5.8 o

F

26.9 % trips above 28 oC

Trip Frequency [%]

Temperature [oC]

Average Ambient Trip Temperature: DOE Fleet

Created: Aug-14-09 4:47 PM

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0

5

10

15

20

25

30

35

40

Speed [mph]

Operation Time [%]

Fuel Cell Vehicle Speed

DOE Fleet Speed

DOE Fleet Idle

1015 Cycle (14.1 mph avg)

UDDS Cycle (19.6 mph avg)

HWFET Cycle (48.0 mph avg)

US06 Cycle (48.2 mph avg)

Created: Sep-09-09 7:39 AM

Other CDP Operation Examples: Power, 

Temperature, Speed, & Time between Trips

0

10

20

30

40

50

Time at Fuel Cell Stack Power Levels: DOE Fleet

Operating Time [%]

0-5%

5-10%

10-15%

15-20%20-25%

25-30%

30-35%

35-40%40-45%45-50%

50-55%

55-60%60-65%

65-70%

70-75%

75-80%

80-85%

85-90%

90-95%

95-100%

>100%

% Max Fuel Cell Power (Gross)

All time

Time with 0 speed

Created: Aug-26-09 2:15 PM

0-1 hr 1-6 hr 6-12 hr 12-18hr 18-24hr 1-7days 7-30days >30days 0

10

20

30

40

50

60

Trip Frequency [%]

Time

Time between Trips: DOE Fleet

0-10 min 10-20 min 20-30 min 30-40 min 40-50 min 50-60 min 0

10

20

30

40

50

% Trips

Time

0-60 min Breakdown: DOE Fleet

Created: Aug-14-09 5:36 PM
National Renewable Energy Laboratory 30 Innovation for Our Energy Future

DURABILITY ANALYSIS

State-of-the-art fuel cell laboratory data
National Renewable Energy Laboratory 31 Innovation for Our Energy Future

FC Lab Data Durability Projected Time to 10%

Voltage Drop

Automotive Forklift Stationary

Application Category

Time [Hours](5)

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

Automotive Target6

Stationary Target6

Created: May-07-09 4:26 PM

(1) The DOE 10% voltage degradation metric is

a general metric for assessing voltage

degradation, which may not be the same as an

OEM's end-of-life criteria and does not address

"catastrophic" failure modes such as membrane

failure.

(2) Collected data consists of lab test data from

short stacks and systems in multiple applications.

(3) Collected data was generated with various

test bench operation such as constant current

and accelerated degradation tests.

(4) Operating period for collected data spans

from 2004 to early 2009.

(5) The upper limit of the bar represents the

maximum operating time to 10% voltage

degradation.

(6) The DOE Automotive and Stationary targets

are applied to real-world applications; refer to

Hydrogen, Fuel Cells, & Infrastructure

Technologies Program Plan.

PEM Fuel Cell Stack 10% Voltage Degradation Projections1

 -

Laboratory Durability Test Data2-4

Targets for real-world operation

Data variability limits the 

extent of data details
National Renewable Energy Laboratory 32 Innovation for Our Energy Future

0

1000

2000

3000

4000

5000

6000

7000

FCV Field (LD Gen1) FCV Field (LD Gen2) Lab (FCV App)

Projected Hours to 10% Voltage Drop

Comparison of Fuel Cell Vehicle Field and Lab Durability Projections

2015 Target

2009 Target

2006 Target

Ave Proj

Max Proj

Created: Dec -02-09 5:36 PM

Fuel Cell Durability Comparison 

between Field and Lab Data

Improvements in durability 

demonstrated

Disconnect between lab and 

on-road data projections
National Renewable Energy Laboratory 33 Innovation for Our Energy Future

Possible approach for a look at durability status (and other 

metrics) across many applications
National Renewable Energy Laboratory 34 Innovation for Our Energy Future

Summary

• Many fuel cell applications analyzed 

in HSDC through 2009

• Demonstrated progress in FC 

durability

• Apply degradation analysis 

developed for FC vehicle to other 

applications

• Able to compare and study durability between applications, 

technology generations, and state-of-the-art laboratory 

data

• Collaborative effort with DOE, project partners, and R&D 

community
National Renewable Energy Laboratory 35 Innovation for Our Energy Future

Website & Contact Info

Jennifer Kurtz

jennifer.kurtz@nrel.gov

303-275-4061

www.nrel.gov/hydrogen/proj_tech_validation.html