A national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

National Renewable Energy Laboratory 

Innovation for Our Energy Future 

Learning Demonstration 

Progress Report – Spring 2008 

K. Wipke, S. Sprik, and J. Kurtz 

Technical Report 

NREL/TP-560-42986 

April 2008 

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Technical Report 

NREL/TP-560-42986 

April 2008 

Learning Demonstration 

Progress Report – Spring 2008 

K. Wipke, S. Sprik, and J. Kurtz 

Prepared under Task No. H270.8100 
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Executive Summary 

This purpose of this report is to document and discuss key results based on data through 

December 2007 from the U.S. Department of Energy’s (DOE) Controlled Hydrogen Fleet and 

Infrastructure Validation and Demonstration Project, also referred to as the Fuel Cell Vehicle 

(FCV) and Infrastructure Learning Demonstration. This report serves as one of many 

mechanisms to help transfer knowledge and lessons learned within various parts of DOE’s 

hydrogen program, as well as externally to other stakeholders. 

The DOE’s National Renewable Energy Laboratory (NREL) has now analyzed data from almost 

three years of the five-year project. During this time, 92 vehicles have been deployed, 14 project 

refueling stations have been placed in use, and no fundamental safety issues have been identified. 

We’ve analyzed data from over 200,000 individual vehicle trips covering 1,100,000 miles 

traveled and over 40,000 kg hydrogen produced or dispensed. With additional hours of 

operation accumulated on the stacks, the fuel cell degradation projections have been updated and 

the four-team average projection is at 1,200 hours. In the next six months NREL will improve 

the accuracy of its projections by adding a non-linear fit (or a two-step linear fit) to avoid 

overestimating the projected time that could occur as the accumulated hours continues to grow. 

To understand what is causing the stacks to gradually degrade, NREL continues to characterize 

how each stack is used and performs multivariate analysis on this dataset to examine dominant 

variables affecting stack voltage degradation rate. Results to date indicate that trends across all 

four teams are probably not possible to extract due to differences among the teams, but that 

individual results may be useful to the teams individually and for feeding trends back into the 

research and development (R&D) program. We’ve analyzed fuel cell system efficiency at 1⁄4-

power and compared it to the DOE target of 60%; system efficiency results from the four teams 

ranged from 52.5% to 58.1%. 

Using data on communication vs. non-communication fills we found that communication fills 

demonstrated a higher rate of fill than non-communication; the slowest of the noncommunication fill rates are being phased out. We also examined refueling and driving 

behavior, and found the Learning Demonstration fleet to be representative of national statistics 

with the exception of fewer late afternoon and weekend trips, an abundance of short trips, and a 

shorter average distance traveled per day. Finally, we’ve now published a total of 47 composite 

data products (CDPs) to date and made them directly accessible to the public from our Hydrogen 

Technology Validation Web site. 

iii
Contents 

Executive Summary .....................................................................................................................iii 

1. Learning Demonstration Progress Report – Spring 2008 .....................................................1 

1.1 Introduction .....................................................................................................................1 

1.2 Approach .........................................................................................................................2 

1.3 Key Analysis Accomplishments .....................................................................................3 

2. Results.........................................................................................................................................4 

2.1 Vehicle Results................................................................................................................6 

2.2 Infrastructure Results ....................................................................................................12 

2.3 Conclusions and Future Directions ...............................................................................15 

2.4 Recent Publications/Presentations from 2007/2008......................................................16 

2.5 Acronyms ......................................................................................................................17 

2.6 Composite Data Products Referenced in Previous Discussion .....................................18 

Figures 

Figure 1: Photographs of the Four Teams' First-Generation Vehicles with Small Inset Photos 

Showing the Second-Generation Vehicles....................................................................1

Figure 2: Four Examples of Hydrogen Production and Refueling Facilities................................2

Figure 3: Data Flow for Hydrogen Secure Data Center (HSDC) Analysis and Results, Overlaid 

on Top of Quantity of Data Received at HSDC............................................................3

Figure 4: Screen Capture from NREL's Composite Data Product Web Site................................5

Figure 5: Fuel Cell System Efficiency at ~25% Net Power (CDP8)..........................................18

Figure 6: Histogram of Time Spent At FC Power Levels (CDP46)...........................................18

Figure 7: Fuel Cell System Energy within Power Levels (CDP53) ...........................................19

Figure 8: Trip Length (CDP47) ..................................................................................................19

Figure 9: Fuel Cell System Energy by Trip (CDP55).................................................................20

Figure 10: Daily Driving Distance (CDP56) ................................................................................20

Figure 11: Time between Trips (CDP54) .....................................................................................21

Figure 12: Fuel Economy (CDP6)................................................................................................21

Figure 13: Vehicle Range (CDP2)................................................................................................22

Figure 14: Percentage of Theoretical Range Traveled between Refuelings (CDP33) .................22

Figure 15: Effective Vehicle Range (CDP34) ..............................................................................23

Figure 16: Weight % Hydrogen Stored (CDP10).........................................................................23

Figure 17: Volumetric Capacity of Hydrogen Storage (CDP11)..................................................24

Figure 18: Hydrogen Storage System Mass and Volume Breakdown (CDP 57).........................24

Figure 19: Vehicle Hydrogen Tank Cycle Life (CDP12).............................................................25

Figure 20: Hours Accumulated and Projected Hours to 10% Stack Voltage 

Degradation (CDP1)....................................................................................................25

Figure 21: Primary Factors Affecting Learning Demo Fleet Fuel Cell Degradation (CDP48)....26

Figure 22: Primary Factors Affecting Learning Demo Team Fuel Cell Degradation (CDP49)...26

Figure 23: Driving Start Time – Day (CDP44) ............................................................................27

Figure 24: Driving Start Time – Night (CDP51)..........................................................................27

Figure 25: Driving by Day of Week (CDP45)..............................................................................28

iv
Figure 26: Safety Reports – Vehicles (CDP9)..............................................................................28

Figure 27: Range of Ambient Temperature during Vehicle Operation (CDP21).........................29

Figure 28: Vehicle Operating Hours (CDP22) .............................................................................29

Figure 29: Vehicles vs. Miles Traveled (CDP23).........................................................................30

Figure 30: Cumulative Vehicle Miles Traveled (CDP24)............................................................30

Figure 31: Vehicle Hydrogen Storage Technologies (CDP25) ....................................................31

Figure 32: Hydrogen Purity Scatter Plot (CDP27) .......................................................................31

Figure 33: Hydrogen Impurities Scatter Plot (CDP28).................................................................32

Figure 34: Infrastructure Maintenance (CDP30)..........................................................................32

Figure 35: Safety Reports – Infrastructure (CDP20)....................................................................33

Figure 36: Primary Factors of Infrastructure Safety Reports (CDP37)........................................33

Figure 37: Average Refuelings between Infrastructure Safety Reports (CDP35)........................34

Figure 38: Type of Infrastructure Safety Report by Quarter (CDP36).........................................34

Figure 39: Refueling Times (CDP38)...........................................................................................35

Figure 40: Refueling Amounts (CDP39)......................................................................................35

Figure 41: Refueling Rates (CDP18)............................................................................................36

Figure 42: Fueling Rates – Communication and Non-Communication Fills (CDP29)................36

Figure 43: Refueling Data by Year (CDP52) ...............................................................................37

Figure 44: Hydrogen Tank Level at Refueling (CDP40)..............................................................37

Figure 45: Refueling Tank Levels - Medians (CDP41)................................................................38

Figure 46: Refueling by Time of Day (CDP42) ...........................................................................38

Figure 47: Refueling by Time of Night (CDP50).........................................................................39

Figure 48: Refueling by Day of Week (CDP43) ..........................................................................39

Figure 49: Cumulative Hydrogen Produced or Dispensed (CDP26)............................................40

Figure 50: Infrastructure Hydrogen Production Methods (CDP32) .............................................40

Figure 51: Number of Reporting Stations (CDP31) .....................................................................41

v
1 Learning Demonstration Progress Report – Spring 2008 

1.1 Introduction 

This purpose of this report is to document and discuss key results to date (based on data through 

December 2007) from the U.S. Department of Energy’s (DOE) Controlled Hydrogen Fleet and 

Infrastructure Validation and Demonstration Project, also referred to as the Fuel Cell Vehicle 

(FCV) and Infrastructure Learning Demonstration. This report is one of many mechanisms we 

use to help transfer knowledge and lessons learned within various parts of DOE’s hydrogen 

program, as well as externally to other stakeholders. Other mechanisms have included: briefings 

to FreedomCAR and Fuels technical teams, presentations at technical conferences, postings of 

individual results to the National Renewable Energy Laboratory’s (NREL) Web site, 

presentations at DOE’s Annual Merit Review, and participation in groups such as the California 

Hydrogen Business Council, US Fuel Cell Council Joint Hydrogen Quality Task Force, and 

various California Fuel Cell Partnership working groups. 

Figure 1: Photographs of the Four Teams' First-Generation Vehicles with Small Inset Photos 

Showing the Second-Generation Vehicles 

The primary goal of this project is to validate vehicle and infrastructure systems using hydrogen 

as a transportation fuel for light-duty vehicles. This means validating the use of FCVs and 

hydrogen refueling infrastructure under real-world conditions using multiple sites, various 

climates, and a variety of hydrogen sources. See Figure 1 for photographs of the first-generation 

1
vehicles and logos of the four teams and Figure 2 for photographs representing examples of the 

four types of hydrogen refueling stations. 

Figure 2: Four Examples of Hydrogen Production and Refueling Facilities 

By 2009 we will validate hydrogen vehicles and infrastructure against the following targets: 

• 250-mile range 

• 2,000-hour fuel cell durability 

• $3/gge hydrogen production cost (based on volume production). 

We are identifying the current status of the technology and tracking its evolution over the fiveyear project duration. In particular, we are tracking differences between the first- and secondgeneration FCVs. NREL works to provide DOE and industry with maximum value from the 

data produced by this “learning demonstration.” We seek to understand the progress toward the 

technical targets, and provide that information to the Hydrogen Fuel Cells and Infrastructure 

Technologies (HFCIT) research and development (R&D) activities. This information will allow 

the program to move more quickly toward cost-effective, reliable hydrogen FCVs and supporting 

refueling infrastructure. 

1.2 Approach 

NREL’s approach to accomplishing the project’s objectives is structured around a highly 

collaborative relationship with each of the four industry teams: Chevron/Hyundai-Kia, 

Chrysler/BP, Ford/BP, and GM/Shell. We are receiving raw technical data on both the hydrogen 

vehicles and refueling infrastructure that allows us to perform unique and valuable analyses 

across all four teams. Our primary objectives are to feed the current technical challenges and 

opportunities back into the DOE Hydrogen R&D Program and assess the current status and 

progress toward targets. 

Hydrogen and Gasoline Station

Washington, DC Mobile Refueler

Sacramento, CA 

Steam Methane Reforming

Oakland, CA 

DTE/BP Power Park 

Southfield, MI 

Delivered 

Compressed 

H2

Natural Gas 

On-Site 

Reforming

Delivered 

Liquid H2 

Electrolysis 

2
To protect the commercial value of these data for each company, we established the Hydrogen 

Secure Data Center (HSDC) to house the data and perform our analysis (Figure 3 shows the flow 

of data and results, overlaid on top of the quantity of data received at the HSDC). To ensure 

value is fed back to the hydrogen community, we publish composite data products (CDPs) twice 

a year at technical conferences. These data products report on the progress of the technology and 

the project, focusing on the most significant results. Additional CDPs are conceived as 

additional trends and results of interest are identified. We also provide our detailed analytical 

results from each individual company’s data back to them to maximize the industry benefit from 

NREL’s analysis work and obtain feedback on our methodologies. These individual results are 

not made available to the public. 

On-Road Data Received -- Running Totals

49245

203379

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

Sep-04

Dec-04

Mar-05

Jun-05

Sep-05

Dec-05

Mar-06

Jun-06

Sep-06

Dec-06

Mar-07

Jun-07

Sep-07

Dec-07

MB of Data

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

220000

240000

260000

# Trips

Figure 3: Data Flow for Hydrogen Secure Data Center (HSDC) Analysis and Results, Overlaid on 

Top of Quantity of Data Received at HSDC 

1.3 Key Analysis Accomplishments 

• Created and published 47 new or updated CDPs (the fifth such set of public results) 

representing results of analyzing almost three years of Learning Demonstration data. The 

results will be presented publicly at the National Hydrogen Association conference 

(Sacramento, CA) and DOE’s Annual Merit Review (Washington, DC). 

MB of data

# trips

Composite 

Data 

Products

Through January 2008: 

>200,000 individual 

vehicle trips 

49 GB of on-road data 

NREL

HSDC 

Detailed 

Data 

Products

3
• Provided all CDPs on an NREL Web page at 

http://www.nrel.gov/hydrogen/cdp_topic.html to allow direct public access to the latest 

CDPs organized by topic, date, and CDP number. This also allows the results to be 

indexed directly by search engines. 

• Made major improvements to NREL’s Fleet Analysis Toolkit (FAT) to include 

multivariate analysis of primary factors affecting stack degradation. We have also 

improved the creation and organization of detailed data product generation to allow easier 

distribution of protected results to the respective industry teams. 

• Further developed the collaborative technical relationship with all four industry teams by 

giving presentations to each team. The presentations included detailed results from 

NREL’s analysis of their vehicle and infrastructure data. 

• Received and processed information from over 200,000 individual vehicle trips, 

amounting to over 49 GB of data, since project inception. 

2 Results 

The results discussed here came from analyzing almost three years of vehicle and infrastructure 

data (through December, 2007). This resulted in a total of 47 new or updated CDPS that we 

could present at technical conferences. To accomplish the analysis, we continued to improve and 

revise our in-house fleet analysis tool, FAT. 

Since there are now so many technical results from the project, they cannot normally all be 

discussed during 15-20 minute conference presentations. Therefore, in January 2007 NREL 

launched a new Web page at http://www.nrel.gov/hydrogen/cdp_topic.html to provide the public 

with direct access to the results (see Figure 4 for a screen capture of this Web page). The Web 

site makes current and archived CDPs available to the public. The most recent results are 

scheduled to be presented publicly at the National Hydrogen Association conference (4/08) and 

the DOE Annual Hydrogen Program Merit Review (6/08) as the “Spring 2008 Results.” In order 

to focus on high-level results, conclusions, and trends, this report will discuss the results in bullet 

form, organized by technical topic. The last section includes all of the CDPs in the order they are 

referenced. 

4
Figure 4: Screen Capture from NREL's Composite Data Product Web Site 

5
2.1 Vehicle Results 

• Fuel Cell System Efficiency: Researchers from the car companies measured fuel cell 

system efficiency from select vehicles on a vehicle chassis dynamometer at several 

steady-state points of operation. NREL worked with the data and the companies to 

ensure that appropriate balance-of-plant electrical loads were included. This ensured that 

the results were comparable to the target and based on the entire system rather than just 

the stack. DOE’s technical target for net system efficiency at 1⁄4-power is 60%. Baseline 

data from the four Learning Demonstration teams showed a range of net system 

efficiency from 52.5% to 58.1% (Figure 5), which is very close to the target. These 

results have not changed since they were first published because they are baseline results 

for first-generation vehicles, but the teams will test second-generation systems as soon as 

they are introduced in the next year to evaluate any efficiency changes as the systems get 

closer to technology readiness. 

• Fuel Cell Operating Points: Since a fuel cell system’s peak efficiency is normally at low 

powers (typically 10% to 25%), we evaluated the fuel cell system operation from a 

number of different perspectives to better understand whether the unique performance 

characteristics of the fuel cell system were being maximized. As reported in the last 

progress report (September 2007), a significant amount of time is being spent at low fuel 

cell system power (Figure 6). In fact, the teams’ average amount of time spent at <5% of 

peak power was over 50%. However, for overall vehicle fuel efficiency, the amount of 

energy spent at various power levels and the efficiency at those power levels is the 

critical metric. We found that much of the fuel cell energy (about 40%) is expended at 

fuel cell power levels between 20% and 50% of peak power (Figure 7). This matches up 

very well with the peak fuel cell system efficiency points (at ~25% power) previously 

discussed. Only about 20% of the energy is expended at powers <15% of peak power, 

indicating that low power efficiency is not as important as the percentage of time spent 

there would imply. 

• Trip Length Evaluation: In order to understand why so much time was spent at low 

power, we analyzed the length of trips and compared the results to national statistics 

(Figure 8). With more than 40% of the Learning Demonstration trips being less than one 

mile long, it is clear that the amount of time spent at low fuel cell power is due in part to 

a large number of short trips for which the vehicle is not likely accelerated to higher 

speeds. This differs from the national driving statistics, which show that only about 10% 

of the trips are less than one mile long. If a large number of starts/hour is one of the 

major degradation factors, as has been reported at the laboratory scale, then this large 

number of short driving trips could be prematurely shortening the life of the Learning 

Demonstration fuel cells. Further investigation is necessary before that linkage can be 

made based on our analysis of the real-world data. 

• The Impact of Short Trips: Recently there has been much public attention on the 

potential for plug-in hybrid-electric vehicles (PHEVs) to improve the United States’ oildependency situation without waiting for fuel cell vehicles to be commercialized. The 

Learning Demonstration vehicle data were evaluated to see how these early fuel cell 

vehicles were being used (mostly in fleet operation) and what impact these duty cycles 

would have on plug-in vehicles and potentially future plug-in versions of these fuel cell 

vehicles. We first looked at the amount of energy consumed by all Learning 

6
Demonstration vehicle trips (Figure 9) and found that almost 40% of the trips required 

less than 0.5 kWh of energy to be produced by the fuel cell system. This indicates that a 

battery would not have to be very large to handle several plug-in FCV trips for the 

Learning Demonstration vehicles, provided that the battery could also provide the peak 

power required and survive the larger swings in state-of-charge. However, this is not the 

entire story, and if the assumption is that PHEVs will primarily be recharged slowly 

during off-peak/night times, then these data need to be analyzed with both the daily miles 

traveled (Figure 10) and the amount of time between trips (Figure 11) in mind. 

What we find is that an effective 20-mile electric range would electrify about 1⁄2 of the 

Learning Demonstration fleet’s daily miles traveled. However, this would satisfy only 

about 1⁄4 of the national daily average miles traveled. While the large number of Learning 

Demonstration vehicle “hot-starts” could be beneficial for fuel efficiency (about 60% of 

trips occur within one hour of the previous trip) this also indicates that not all of the short 

trips could necessarily be electrified because there may not be sufficient time to recharge 

the battery from the grid in between trips, even if day-time opportunity charging is used. 

The bottom-line is that a thorough analysis of actual target-market duty cycles must occur 

for the benefits of PHEVs to be understood, preferably through using actual PHEV fleets 

and recharging behavior. Such an evaluation is envisioned through DOE’s current 

solicitation for a PHEV Learning Demonstration (see Web site for details: 

http://www.netl.doe.gov/business/solicitations/#00360). 

• Vehicle Fuel Economy: Vehicle fuel economy was measured using city and highway 

drive-cycle tests (Figure 12) on a chassis dynamometer using draft SAE J2572 (left blue 

bar, representing the range of four points, one from each original equipment manufacturer 

[OEM]). These raw test results were then adjusted according to U.S. Environmental 

Protection Agency (EPA) methods to create the “window-sticker” fuel economy that 

consumers see when purchasing the vehicles (0.78 x Hwy, 0.9 x City) (center blue bar). 

This resulted in an adjusted fuel-economy range of 42 to 56.5 miles/kg hydrogen for the 

four teams. As with all vehicles sold today, including gasoline hybrids, actual on-road 

fuel economy is slightly lower than this rated fuel economy (right blue bar). The on-road 

fuel economy spans the range of 30 miles/kg hydrogen to about 45 miles/kg hydrogen. 

Note that the EPA has adjusted its testing and reporting methodology beginning with 

model-year 2008 vehicles to try to make the window-sticker fuel economy better reflect 

on-road driving performance, but this project is using the EPA adjustment that was in 

place when the vehicles were introduced. 

• Vehicle Driving Range: Vehicle driving range was calculated using the fuel economy 

results discussed above and multiplying them by the usable hydrogen stored onboard 

each vehicle (Figure 13). Using the EPA-adjusted fuel economy resulted in a range from 

just over 100 miles up to 190 miles from the four teams. The second-generation vehicles 

will strive to push this range up to 250 miles to reach the 2009 DOE target. Note that two 

other CDPs relating to range were also generated. Figure 14 shows a histogram of the 

distance vehicles actually traveled between fuelings as a percentage of each vehicle’s 

dynamometer range. This shows that the majority of the vehicles (75%) travel less than 

50% of the dynamometer range between fuelings. This is due to several factors, but the 

dominant ones are limited hydrogen infrastructure, fear of running out of fuel, and actual 

on-road fuel economy being lower than the dynamometer fuel economy, as has already 

7
been discussed. Figure 15 shows the on-road range of the four teams (green bar) as a 

percentage of their dynamometer range. The spread of this on-road range has decreased 

significantly in the last year, indicating that the vehicles’ on-road fuel economy as a 

percentage of their dynamometer fuel economy (~63%-73%) is similar across all four 

teams. There is a good potential for a greater range from the second-generation vehicles 

due to higher hydrogen storage pressure (700 bar) and more vehicles that may be 

designed with storage system limitations (packaging, in particular) in mind. 

• On-Board Hydrogen Energy Storage System Status: In the last six months, additional 

hydrogen storage data have been reported to NREL using a more detailed hydrogen 

storage system breakdown spreadsheet. This spreadsheet includes the breakdown of the 

mass and volume due to the hydrogen itself, the pressure vessel, and the balance-of-plant. 

The balance-of-plant category includes: 

o Controls and measurement (hydrogen storage-specific electronics) 

o Fuel delivery to powerplant (plumbing) 

o Hazard mitigation components (hydrogen sensors, pressure release devices 

(PRD), venting) 

o Fueling equipment (filters, nozzle receptacle, piping, communications, grounding) 

o Mounting brackets, auxiliary equipment (thermal management, etc.). 

While previous published results only included first-generation vehicle data, the recent 

detailed data were supplied for both first- and second-generation hydrogen storage 

systems. Figure 16 shows the difference in the ranges of mass (as a percentage of the 

total mass) stored in the teams’ 350 bar and 700 bar systems. We can see the potential 

for the percentage of system mass to increase in the second-generation systems, but we 

need to realize that the second-generation (700 bar) systems also typically have the 

benefit of economies of scale because they will have a larger total mass of hydrogen 

stored to meet the 250-mile range target. 

Figure 17 shows the same type of 350 bar vs. 700 bar comparison but for the volumetric 

capacity (how much hydrogen can be stored per storage system volume). This is where 

the advantage of going to a higher pressure really shines, showing the potential for a 

significant increase in the mass of hydrogen stored per liter, making the packaging of the 

system on a vehicle more attractive. Finally, the percentage breakdown by each of these 

categories was averaged across the four teams so that pie-charts of the differences 

between 350 bar and 700 bar could be examined for the mass and volumetric 

characteristics (Figure 18). The comparison shows that while the average hydrogen 

weight percentages are similar for 350 and 700 bar, and the pressure vessel and balanceof-plant for 700 bar take up a larger percentage of the system volume, the 700 bar 

systems allow for a more compact package and extended range. Figure 19 shows the 

tank cycle life, which may be updated in the future if data can be obtained for this metric 

for second-generation systems at 700 bar. 

• Fuel Cell Durability: Fuel cell stacks will need roughly a 5,000 hour life to enter the 

market for light-duty vehicles. For this demonstration project, targets were set by DOE at 

1,000 hours in 2006 and 2,000 hours in 2009. Results were first published in the fall of 

2006. These results were relatively preliminary because most stacks at that time only had 

a few hundred hours of operation or less accumulated on-road. Since DOE’s target for 

8
2006 was 1,000 hours, NREL developed a methodology for projecting the gradual 

degradation of the voltage based on the data received to date. This involved creating 

periodic fuel cell polarization curve fits from the on-road stack voltage and current data, 

and calculating the voltage under high current. This enabled us to track the gradual 

degradation of the stacks with time and do a linear fit through each team’s data. We then 

compared these results to the first-generation target of 1,000 hours for 2006. 

In the past year and a half, many more hours have been accumulated on the fuel cell 

stacks, and the range of fleet averages is ~200 to 700 hours, with the range of fleet 

maximums spanning ~300 to 1,200 hours (Figure 20). This is the first time, to our 

knowledge, that a light-duty passenger fuel cell car has accumulated more than 1,000 

hours in real-world operation without repair, which is a significant project 

accomplishment. Therefore, the amount of extrapolation we have to make using the 

slope of the linear voltage degradation method (10% voltage drop target divided by the 

mV/hour slope), continues to decrease. However, with the additional data we have 

received, we are also finding that the accuracy of the 10% voltage degradation target 

could be improved by using a non-linear fit to account for the more rapid degradation that 

occurs within the first few hundred hours. It appears as though the current linear fit may 

be overestimating the time to a 10% voltage drop for the stacks that have a significant 

number of accumulated hours, and we will be pursuing a non-linear or two-step linear fit 

to improve the accuracy in the future. 

The projected times to 10% fuel cell stack voltage degradation from the four teams using 

the linear technique had an average of more than 1,200 hours with a high projection of 

more than 1,900 hours from one team, surpassing the 1,000-hour DOE target. Note that 

the 10% criterion, which is used for assessing progress toward DOE targets, may differ 

from the OEM’s end-of-life criterion and does not address “catastrophic” failures such as 

membrane failure. The second-generation stacks introduced in this project beginning in 

late 2007 will be compared to the 2,000-hour target for 2009. 

• Factors Affecting Fuel Cell Durability: We have continued the multivariate analysis that 

was initiated in 2007 to determine the dominant factors that are affecting the rates of 

degradation. We started out by creating a database of all of the Learning Demonstration 

stacks and various performance attributes. Each individual stack was examined for the 

hours of data accumulated to date and the confidence in the fit of the degradation slope. 

We then manually removed about one-third of the stacks from the degradation factors 

analysis to try to have as clean a data set as possible for the analysis. The database now 

includes the following key factors for each stack: 

o Average voltage degradation rate (key dependent variable) 

o Ambient temperature 

o Time at various voltages 

o Time at various currents 

o Number of cold and hot starts (based on time between trips) 

o Idle time 

o Trip length 

o Average number of stack starts/hour. 

9
After trying many techniques, we focused on partial least squares regression (PLS) 

analysis because it was the most direct way of measuring how much of the variance in 

voltage degradation could be explained by specific groups of factors. We first performed 

the PLS on the stack data from all four teams to see if there were any overall trends that 

covered all of the technology involved (Figure 21). The trends across all four teams were 

not strong, which we soon discovered was because the trends among the companies were 

often different. 

Next we looked at each team’s data individually and performed the same PLS analysis 

(Figure 22). The connection between voltage degradation rate and the variables 

improved, and we were able to pull out groupings of factors that appeared to cause either 

higher or lower than average decay rates within each team. Note that the teams’ PLS 

models have a high percentage of explained decay rate variance, but the models are not 

very robust and results are scattered. We found that while there were some common 

factors among several team’s results, there were also normally contradictory trends from 

one of the teams (an example of this conflicting trend is for high voltage time and low 

current time for team four vs. team two). This analysis effort is continuing in close 

collaboration with each of our industry partners. NREL will work closely with each team 

to carefully examine the inputs and outputs from this analysis and see if there are 

valuable lessons that can be fed back into the companies’ research as well as into DOE’s 

R&D program. 

• Time of Day Vehicles Are Driven: Some questions have arisen about whether the 

Learning Demonstration vehicles are being used like conventional vehicles, or whether 

their usage is being too “controlled” to match typical driving behavior. To investigate 

this we looked at the time of day people initiated their trips and which day of the week 

the trips were occurring on. Figure 23 shows a clock-face radial histogram, with the 

green data representing the time of day when people initiated their trips. Overlaid on top 

of that we have placed pink diamonds to show the national statistics based on the 2001 

National Household Travel Survey (NHTS) data. What we find is that the Learning 

Demonstration vehicles are driven at similar times of day to the national statistics, with 

the exception of the late afternoon between 4 and 6 p.m. when the average person 

(nationally) is likely either picking up kids from school, driving home from work, or 

running errands. Since the first-generation Learning Demonstration vehicles are 

primarily used for professional or fleet activities, it is not surprising that there would be a 

difference. The percentage of trips taken between 6 a.m. and 6 p.m. corresponds 

relatively closely to the national statistics (88.7% vs. 81.5%). The nighttime driving 

behavior trend is also similar to the national statistics (Figure 24), although there are 

overall more evening trips driven nationally than within the Learning Demonstration. 

• Day of Week Vehicles Are Driven: We examined the days of the week that people drove 

the Learning Demonstration FCVs and compared this with the national statistics. Figure 

25 shows a bar for each day of the week, beginning with Sunday, and overlays a diamond 

symbol for the national statistics. We can easily see that nationally the trips are relatively 

uniform on weekdays, with a slight dip on the weekends, but that the Learning 

Demonstration vehicles are rarely driven on the weekends. Additionally, Learning 

Demonstration vehicles have significantly more trips Tuesday through Thursday as 

compared to Monday and Friday, which does not reflect typical national behavior. While 

10
the day of the week doesn’t matter to the car’s performance, it might be an indication that 

some of the weekend types of trips (for example: long trips to mountains or lots of short 

trips to the hardware store) are not being captured in the first-generation vehicle duty 

cycles. 

• Vehicle Safety: The Learning Demonstration has had a very strong safety record to date. 

Figure 26 shows the latest number and type of vehicle safety reports by quarter. In the 

last six months there have been two safety report additions: one traffic accident and two 

hydrogen tanks that were removed from service due to minor scratches noted during 

inspection. In the case of the traffic accident, there was no hydrogen release and only 

minor injuries due to the two-vehicle impact (not hydrogen related). In the case of the 

two tanks that were removed for service, the team determined that the tanks had been 

scratched during service of a nearby system and that the scratches could be easily 

repaired without affecting the safety of the tanks. 

• Other Vehicle Metrics: There are several other vehicle-related CDPs that will be briefly 

mentioned here. Figure 27 shows the range of ambient temperature during vehicle 

operation spanning from 1°F-123°F, with no change from what has previously been 

reported. Fuel cell vehicles are currently able to operate in extreme temperature 

conditions, and second-generation vehicle tests will determine their ability to also start 

from sub-freezing temperatures. Figure 28 shows the distribution of vehicle operating 

hours, showing a total of over 50,000 hours with a median of about 600 hours. The 

introduction of second-generation vehicles has introduced a second bulge on the left side 

of the histogram at low vehicle operating hours. Similarly, with vehicle miles traveled 

(shown in Figure 29), the peak number of vehicles occurs at 10,500 – 14,000 miles. The 

fleet has now accumulated over 1.1 million miles. Figure 30 shows that after the first few 

quarters, mileage accumulation has been relatively linear. The rate of mileage 

accumulation should rise with the introduction of the second-generation vehicles. Figure 

31 tracks the total number of Learning Demonstration vehicles deployed by quarter and 

the on-board hydrogen storage systems that they use. Figure 31 also shows many of the 

second-generation deployments with 700 bar tanks. 

11
2.2 Infrastructure Results 

• Hydrogen Quality: Hydrogen quality was determined by measuring the impurities and 

calculating the hydrogen fuel quality index as a percentage. SAE J2719 has established a 

99.99% hydrogen fuel quality index target. The hydrogen fuel quality index from all the 

stations sampled ranged from 99.73% to 99.999%, as shown in Figure 32. The values on 

the lower end were due to some high detection limits on inert gases, and likely do not 

really represent hydrogen fuel quality that low. This result has not changed significantly 

in the last six months with most of the new data coming in very close to the 99.99% 

target. 

• Hydrogen Impurities: More important than the absolute hydrogen fuel quality index is the 

actual level of impurities by constituent. Impurities evaluated include particulates, inert 

gases (N2 + H2 + Ar), NH3, CO, CO2, O2, total HC, H2O, and total sulfur, and are shown 

in Figure 33. One key finding was that reported values are, in general, close to the SAE 

J2719 target values. As previously reported, all but one sulfur data point are at the 

detection limits of the hardware used. While the target for sulfur is 4 parts per billion 

(ppb), results ranged from 1-70 ppb. Therefore, either new cost-effective techniques to 

get real measurements at such low concentrations should be developed, or the target 

should be raised to something that can effectively be measured with confidence. 

• H2 Infrastructure Maintenance: An evaluation of all of the maintenance required on 

refueling station equipment found that roughly 1⁄2 of all labor hours were unplanned, 

accounting for 60% of the maintenance events (Figure 34). With the large volume of 

infrastructure maintenance items over the past three years, there is no significant shift 

between the planned and unplanned maintenance events. 

• Infrastructure Safety: With respect to hydrogen refueling infrastructure, there has been 

one new report that was classified as an incident (making for a total of two over the entire 

project). This new report involved a hydrogen compressor that shut down due to 

excessive vibration. Upon inspection technicians discovered that some of the bolts on the 

compressor had fallen out, which could have caused a serious problem later if it had not 

been discovered. At a less severe level (see Figure 35), there were 23 events categorized 

as near-misses and over 100 non-events (over 70 were alarms-only). All but five of the 

near-misses involved a minor release of hydrogen with no ignition. 

Figure 36 shows that no single primary factor led to the majority of infrastructure safety 

reports, but over 30 of them were due to calibration/settings or software controls. Figure 

37 shows that the number of refuelings normalized by the number of safety reports per 

quarter had improved by a factor of 10 (higher is better) since the beginning of the 

project, but then dipped down to 60-80 as new stations came online. It has since gone 

back up to around 100 refuelings/report; however no new stations have come online in 

the last nine months. Figure 38 also shows the apparent correlation between new stations 

coming online and a higher number of safety reports. On most of the safety CDPs we 

have now added the DOE definition of incident and near-miss that are being used for this 

project to remove any questions about what they mean. 

• Vehicle Refueling Rates: Hydrogen vehicle refueling needs to be as similar as possible to 

conventional vehicle refueling to allow an easier commercial market introduction. Over 

8,700 refueling events have been analyzed to date, and the refueling amount, time, and 

12
rate have been quantified. The average time to refuel was 3.43 minutes with 87% of the 

refueling events taking less than 5 minutes (Figure 39). The average amount per fill was 

2.25 kg, reflecting both the limited storage capacity of these vehicles (~4 kg max) and 

peoples’ comfort level with letting the fuel gauge get close to empty (see Figure 40 for 

the shape of the distributions), which will be shown in a separate analysis. DOE’s target 

refueling rate is 1 kg/minute, and these Learning Demonstration results indicate an 

average of 0.79 kg/min, with 24% of the refueling events exceeding 1 kg/minute (Figure 

41). Therefore, we can conclude that high-pressure gases are approaching adequate 

refueling times and rates for consumers; however, the challenge is still in packaging 

enough high-pressure hydrogen onboard to provide adequate range, or finding alternate 

advanced hydrogen storage materials that can replace the need for high-pressure tanks. 

• Communication vs. Non-Communication Fills: The previous refueling histograms 

included all types of refueling events. There has been much interest from industry and 

from the codes and standards community about the potential for communication fills to 

occur at a higher rate and with a more complete fill. A communication fill means that the 

vehicle communicates data about the state of its hydrogen storage tank(s) to the refueling 

station, such as tank temperature, pressure, and max pressure rating. Figure 42 shows 

two curves: the red curve is a spline fit to the histogram for non-communication fills 

while the blue curve represents the communication fills. The center part of the graph 

shows a similar rate of fill for the communication and non-communication fills, however 

the communication fills are capable of having a higher fill rate (up to around 1.7 kg/min). 

There is also a group of vehicle/station combinations still doing non-communication fills 

at the slower rate of ~0.2 kg/min on the left portion of the graph. This rate of fill was 

established many years ago in California to provide a conservative and safe approach for 

refueling vehicles before much real-world experience had been gained. Figure 43, which 

shows the fill rates by year, indicates that this slower refueling rate was heavily used in 

2006 but has been almost completely phased out in 2007. With these differences in 

distribution in mind, the average fill rate for all communication fills is 0.94 kg/min vs. 

0.66 kg/min for non-communication fills, with 36% and 20%, respectively, exceeding 

DOE’s 1 kg/min target. 

• Level in Fuel Tank When People Refuel: As previously mentioned, with limited hydrogen 

refueling infrastructure and limited on-board hydrogen storage, some drivers do not like 

to let the tank get close to empty to minimize the risk of running out of fuel. To 

investigate this further, NREL used the data submitted in a new and unique way, which 

was to look at what the fuel level in the tank was just prior to each refueling event. In 

some cases these data came from on-board data based on the pressure in the tank, and in 

other cases they came from refueling logs where each fill was assumed to be to the “full” 

level, allowing a subtraction of the amount fueled to determine the initial tank level. 

Figure 44 shows the results from this analysis, where a histogram has been placed 

radially on an image of a fuel gauge to make interpreting the graph as intuitive as 

possible. The level at which people most commonly refuel the Learning Demonstration 

vehicles is at just over 1⁄4 full; this covers 15% of the refuelings. While some drivers are 

letting the tank get even lower than that, few let it get close to being empty. Additionally, 

we have placed a green needle on the chart which indicates the median tank level at fill 

(1⁄2 above, 1⁄2 below), which is a little above 3⁄8 of a tank (40% of full). Figure 45 shows 

13
the collection of medians for each of the 92 vehicles in the Learning Demonstration fleet 

to show that there is a large spread in when individuals choose to refuel their vehicles, 

with several vehicles being refueled more than half of the time with greater than a halffull tank, but the majority being refueled between 1⁄4 and 1⁄2 full. In the future, we would 

like to compare these data results to data from conventional liquid fueled vehicles, if they 

exist, to see if people are refueling their fuel cell vehicles differently than their 

conventional vehicles. 

• Time of Day When People Refuel: We also looked at the time of day people refueled in 

order to understand the usage patterns at the hydrogen refueling stations and better allow 

new stations to understand the potential demand by time of day. For traditional liquid 

fuels, with big tanker truck deliveries periodically, the time of day people refuel does not 

normally matter. Instead, the station operator must simply ensure that the next tanker 

comes before he runs out of fuel. For today’s hydrogen fuel stations, with very limited 

storage capacity and some sites producing hydrogen throughout the day, it is important to 

know the time of day that people refuel in order to match the supply (on-site production) 

with the demand. 

Figure 46 shows a radial histogram of the time of day Learning Demonstration vehicles 

were refueled between 6 a.m. and 6 p.m., with Figure 47 showing the time between 6 

p.m. and 6 a.m. We found that 86% of the fills occurred between 6 a.m. and 6 p.m., with 

14% being done at night. The distribution is relatively uniform with steady usage 

between 8 a.m. and 4 p.m., and a mild peak at lunchtime (9%). The conclusion from this 

analysis is that with a uniform distribution of when people refuel during the day, a station 

that has on-site production can either be sized to meet that demand during the day and 

then essentially shut off at night, or it can be sized (smaller) for the average over a 24-

hour period, have a larger on-site hydrogen storage buffer, and run continuously. Finally, 

we looked at what day of the week people were refueling (Figure 48) and found that the 

Learning Demonstration vehicles are primarily refueled Monday through Friday, with 

very few vehicles refueled on the weekend. This is consistent with the days of the week 

that people are driving the vehicles most and when the hydrogen stations that have 

attendants are open. 

• Other Infrastructure Metrics: The amount of hydrogen produced or dispensed has also 

been tracked by quarter (blue diamonds) with the number of stations shown on the same 

graph (green squares) in Figure 49. Note that the amount of hydrogen produced is not the 

same as the amount dispensed because the project includes a power park where the 

unused hydrogen can be converted back into grid electricity during peak utility load 

periods in the afternoon (due to higher air-conditioning loads) using on-site fuel cells. As 

discussed in Figure 2, there are four major types of hydrogen refueling stations being 

demonstrated (shown in Figure 50) and the rate of introduction of these stations is shown 

in Figure 51. 

14
2.3 Conclusions and Future Directions 

NREL has now analyzed data from almost three years of the five-year Learning Demonstration 

project with 92 vehicles deployed, 14 project refueling stations in use, and no fundamental safety 

issues identified. We have analyzed data from over 200,000 individual vehicle trips covering 

1,100,000 miles traveled and over 40,000 kg hydrogen produced or dispensed. With additional 

hours of operation accumulated on the stacks, the range of fleet average hours accumulated is 

now ~200 to 700 hours, with the range of fleet maximums spanning ~300 to 1,200 hours. This is 

the first time, to our knowledge, that a light-duty passenger fuel cell car has accumulated more 

than 1,000 hours in real-world operation without repair, which is a significant project 

accomplishment. The four-team average projected time to a 10% voltage degradation is 1,200 

hours. In the next six months NREL will improve the accuracy of its projections by adding a 

non-linear fit (or a two-step linear fit) to avoid overestimating the projected time as the 

accumulated hours continues to grow. 

To understand what is causing the stacks to gradually degrade, NREL continues to characterize 

how each stack is used and perform multivariate analysis on this dataset to examine dominant 

variables affecting stack voltage degradation rates. Results to date indicate that trends across all 

four teams are probably not possible to extract due to differences among the teams, but that 

individual results may be useful to the teams individually and for feeding trends back into the 

R&D program. We’ve analyzed fuel cell system efficiency at 1⁄4-power and compared it to the 

DOE target of 60%; system efficiency results from the four teams ranged from 52.5% to 58.1%. 

Using data on communication vs. non-communication fills we found that communication fills 

demonstrated a higher rate of fill than non-communication; the slowest of the noncommunication fill rates are being phased out. We also examined refueling and driving 

behavior, and found the Learning Demonstration fleet to be representative of national statistics 

with the exception of fewer late afternoon and weekend trips, an abundance of short trips, and a 

shorter average distance traveled per day. Finally, we’ve now published a total of 47 CDPs and 

made them directly accessible to the public through our Hydrogen Technology Validation Web 

site (http://www.nrel.gov/hydrogen/proj_learning_demo.html). 

In the future, we will further explore the correlations of real-world factors influencing fuel cell 

degradation and strive to separate their interwoven dependencies. We will semi-annually 

(spring/fall) compare technical progress to program objectives and targets and provide results to 

the public by participating in technical conferences and writing reports such as this one. 

Specifically, we will create new and updated CDPs based on data through June 2008, and 

prepare those new results for publication at the Fuel Cell Seminar as the “Fall 2008” results. For 

the second-generation vehicles introduced this year, we will begin evaluating improvements in 

fuel cell durability, range, fuel economy, and safety, and publish results when there are sufficient 

second-generation vehicles to mask the companies’ identities. As an important part of the 

project, we will identify opportunities to feed project findings back into HFCIT Program R&D 

activities to maintain the project as a “learning demonstration.” 

15
2.4 Recent Publications/Presentations from 2007/2008 

1. Wipke, K., Sprik, S., Kurtz, J., “Composite Data Products for the Controlled Hydrogen Fleet 

and Infrastructure Demonstration and Validation Project,” Golden, CO: National Renewable 

Energy Laboratory, updated February 2008. (presentation, online at 

http://www.nrel.gov/hydrogen/cdp_topic.html). 

2. Wipke, K., “Hydrogen Secure Data Center: Procedures to Protect Technical Data Submitted 

under the Controlled Hydrogen Fleet and Infrastructure Demonstration and Validation 

Project,” Golden, CO: National Renewable Energy Laboratory, updated December 2007. 

(HSDC document) 

3. Wipke, K., Sprik, S., Kurtz, J., Thomas, H., “FCV Learning Demonstration: Project 

Midpoint Status and Fall 2007 Results,” EVS-23 Conference, Anaheim, CA, December 

2007. (paper and presentation) 

4. Kurtz, J., Wipke, K., Sprik, S., “FCV Learning Demonstration: Factors Affecting Fuel Cell 

Degradation,” Fuel Cell Durability & Performance, Miami, Florida, November 2007. 

(presentation). 

5. Wipke, K., Sprik, S., Kurtz, J., Thomas, H., Garbak, J., “FCV Learning Demonstration: 

Project Midpoint Status and First-Generation Vehicle Results,” ZERO REGIO Conference, 

Montecatini Terme, Italy, November 2007. (presentation) 

6. Wipke, K., Sprik, S., Thomas, H., Welch, C., Kurtz, J., “Controlled Hydrogen Fleet and 

Infrastructure Analysis Project,” 2007 DOE HFCIT Program Annual Progress Report, 

System Analysis Section VI.D.1, November 2007. (paper) 

7. Wipke, K., presentation of Learning Demonstration results to FreedomCAR and Fuels 

Delivery Tech Team, November, 2007. (presentation) 

8. Wipke, K., Sprik, S., Kurtz, J., Thomas, H., Garbak, J., “FCV Learning Demonstration: 

First-Generation Vehicle Results and Factors Affecting Fuel Cell Degradation,” Fuel Cell 

Seminar, San Antonio, TX, October 2007. (presentation and extended abstract). 

9. Wipke, K., Sprik, S., Kurtz, J., Thomas, H., Garbak, J., “Fuel Cell Vehicle and 

Infrastructure Learning Demonstration: Activities in California,” H2 Infrastructure Forum 

Between National & Local Governments and Industry, hosted by USFCC, Washington, DC, 

October 2007. (presentation) 

10. Wipke, K., Sprik, S., Kurtz, J., Thomas, H., “Learning Demonstration Progress Report – 

September 2007,” National Renewable Energy Laboratory Technical Report NREL/TP-560-

42264, October 2007. (paper) 

11. Wipke, K., presentation of Learning Demonstration results to Vehicle Technologies 

Program at DOE, October 2007. (presentation) 

12. Wipke, K., presentation of Learning Demonstration results to FreedomCAR and Fuels 

Hydrogen Storage Tech Team, October, 2007. (presentation) 

16
13. Wipke, K., presentation of Learning Demonstration results to HFCIT Program at DOE, 

October 2007. (presentation) 

14. Wipke, K., Sprik, S., Thomas, H., Welch, C., Kurtz, J., “Learning Demonstration Interim 

Progress Report – Summer 2007,” National Renewable Energy Laboratory Technical 

Report NREL/TP-560-41848, July 2007. (paper) 

15. Wipke, K., Welch, C., Thomas, H., Sprik, S., “Controlled Hydrogen Fleet and Infrastructure 

Analysis,” 2007 DOE Annual Merit Review Meeting, Washington, DC, May 2007. 

(presentation) 

16. Wipke, K., presentation on Learning Demonstration project to National Academy of 

Sciences, Washington, DC, April 2007. (presentation) 

17. Wipke, K., Welch, C., Thomas, H., Sprik, S., Kurtz., J., “DOE’s Controlled Hydrogen Fleet 

and Infrastructure Demonstration and Validation Project: Quarterly Validation Assessment 

Reports,” (HSDC papers only) 

o 4Q 2006, March 2007. 

o 1Q 2007, June 2007. 

o 2Q 2007, September 2007. 

18. Wipke, K., Welch, C., Thomas, H., Sprik, S., Gronich, S., Garbak, J., Hooker, D., “Fuel Cell 

Vehicle Learning Demonstration: Spring 2007 Results,” NHA Annual Hydrogen Meeting 

and Exposition, San Antonio, TX, March 2007. (presentation) 

19. Wipke, K., presentation of Learning Demonstration results to California Hydrogen Business 

Council Meeting, January, 2007. (presentation) 

2.5 Acronyms 

CDP composite data product 

DOE U.S. Department of Energy 

FAT Fleet Analysis Toolkit (software tool developed at NREL) 

FCV fuel cell vehicle 

FY fiscal year 

gge gallon of gasoline equivalent 

H2 hydrogen 

HFCIT Hydrogen, Fuel Cells & Infrastructure Technologies (DOE 

program) 

HSDC Hydrogen Secure Data Center (at NREL) 

MYPP Multi-Year Program Plan (DOE document) 

NHA National Hydrogen Association 

NREL National Renewable Energy Laboratory 

PLS partial least squares 

R&D research and development 

17
2.6 Composite Data Products Referenced in Previous Discussion 

0

10

20

30

40

50

60

70

All OEMs

Efficiency (%) 

Fuel Cell System1 Efficiency2 at ~25% Net Power.

DOE Target

Created: Aug-29-06 4:09 PM

1

 Gross stack power minus fuel cell system auxiliaries, per DRAFT SAEJ2615.

2

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

Excludes power electronics and electric drive.

Figure 5: Fuel Cell System Efficiency at ~25% Net Power (CDP8) 

0

5

10

15

20

25

30

35

40

45

50

%Time at Power Levels v2: DOE Fleet

% Time at Power Level

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%

Created: Feb-27-08 12:04 PM % Fuel Cell Power (Gross) of Max

17.6%-47.9% of operating time at idle

(Vehicle Speed = 0 & F.C. Power > 0)

Figure 6: Histogram of Time Spent At FC Power Levels (CDP46) 

18
0

2

4

6

8

10

% Energy by Power levels: DOE Fleet

% Energy

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%

% Fuel Cell Power (Gross) of Max

Cumulative %

0

20

40

60

80

100

Created: Feb-27-08 12:04 PM

Figure 7: Fuel Cell System Energy within Power Levels (CDP53) 

0 5 10 15 20 25 0

5

10

15

20

25

30

35

40

45

Frequency (%)

Trip Length (miles)

Trip Length: DOE Fleet

DOE Fleet

NHTS

Created: Feb-27-08 11:56 AM

2001 NHTS Data Includes Car, Truck, Van, & SUV day trips

ASCII.csv Source: http://nhts.ornl.gov/download.shtml#2001

Figure 8: Trip Length (CDP47) 

19
0-0.5 0.5-1 1-1.5 1.5-2 2-2.5 2.5-3 3-3.5 3.5-4 4-4.5 4.5-5 >5 0

5

10

15

20

25

30

35

40

Trip Energy: DOE Fleet

% Trips

Energy Consumed [kWh]

Created: Feb-27-08 12:04 PM

# of Trips: 150221

Figure 9: Fuel Cell System Energy by Trip (CDP55) 

0 5 10 15 20 25 30 35 40 0

5

10

15

20

25

Frequency (%)

Daily Distance (miles)

Daily Distance: DOE Fleet

DOE Fleet

NHTS

Created: Feb-27-08 11:56 AM

Cumulative Frequency

@ 20 miles

DOE Fleet: 50.9%

NHTS: 27.2%

Cumulative Frequency

@ 40 miles

DOE Fleet: 69.9%

NHTS: 52.9%

2001 NHTS Data Includes Car, Truck, Van, & SUV day trips

ASCII.csv Source: http://nhts.ornl.gov/download.shtml#2001

Figure 10: Daily Driving Distance (CDP56) 

20
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

% Trips

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

60

% Trips

Time

0-60 min Breakdown: DOE Fleet

Created: Feb-27-08 11:56 AM

Figure 11: Time between Trips (CDP54) 

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

Created: Feb-15-08 7:17 AM

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

(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).

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

Figure 12: Fuel Economy (CDP6) 

21
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

Created: Feb-15-08 7:37 AM

(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.

Figure 13: Vehicle Range (CDP2) 

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

1

2

3

4

5

6

7

8

9

10

11

12

Range Histogram: All OEMs

Percentage of chassis dyno range1

 b/w refuelings

Percentage of Refuelings

0 10 20 30 40 50 60 70 80 90 1000

25

50

75

100

Cumulative Percentage

Created: Feb-15-08 9:20 AM

Total refuelings2 = 10991

1. Range calculated using the combined City/Hwy fuel economy from dyno testing (not EPA

adjusted) and usable fuel on board.

2. Some refueling events are not detected/reported due to data noise or incompleteness.

Figure 14: Percentage of Theoretical Range Traveled between Refuelings (CDP33) 

22
0 10 20 30 40 50 60 70 80 90 100

Vehicle Range Factors

Percentage of chassis dyno range1

.

All OEMs

Window-Sticker 2On-Road 3Dyno 1

Created: Feb-15-08 9:20 AM

1. Calculated using the combined City/Hwy fuel economy from dyno testing (non-adjusted)

and usable fuel on board.

2. Applying window-sticker correction factors for fuel economy: 0.78 x Hwy and 0.9 x City.

3. Using fuel economy from on-road data (excluding trips > 1 mile, consistent with other data products).

Figure 15: Effective Vehicle Range (CDP34) 

350bar 700bar 0

1

2

3

4

5

6

7

8

9

Weight Percent Hydrogen (%)

Weight Percent Hydrogen

2015 DOE MYPP Target1

2010 DOE MYPP Target1

2007 DOE MYPP Target1

Created: Feb-15-08 7:32 AM

1

Targets are set for advanced materials-based hydrogen storage technologies.

Figure 16: Weight % Hydrogen Stored (CDP10) 

23
350bar 700bar 0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Mass H2 per Liter (kg/L)

Mass of Hydrogen Per Liter

2015 DOE MYPP Target1

2010 DOE MYPP Target1

2007 DOE MYPP Target1

Created: Feb-15-08 7:32 AM

1

Targets are set for advanced materials-based hydrogen storage technologies.

Figure 17: Volumetric Capacity of Hydrogen Storage (CDP11) 

Average Breakout of H2 Storage System Volume

73%

24%

3%

Average Breakout of H2 Storage System Mass

73%

23%

3.26%

 350 bar

35% 55%

10%

H2 Volume (%)

Pressure Vessel Volume (%)

Balance of Plant Volume (%)

26%

3.45%

71%

H2 Mass (%)

Pressure Vessel Mass (%)

Balance of Plant Mass (%)

 700 bar

Created: Feb-15-08 6:53 AM

Figure 18: Hydrogen Storage System Mass and Volume Breakdown (CDP 57) 

24
0

2000

4000

6000

8000

10000

12000

All OEMs

Number of cycles

Hydrogen Tank Cycle Life

2015 DOE MYPP Target1

2010 DOE MYPP Target1

2007 DOE MYPP Target1

Created: 23-Feb-2006

1

Some near-term targets have been achieved with compressed and liquid tanks. Emphasis is on advanced materials-based technologies.

Figure 19: Vehicle Hydrogen Tank Cycle Life (CDP12) 

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2006 Target

2009 Target

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

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

Time (Hours)

DOE Learning Demonstration Fuel Cell Stack Durability:

Based on Data Through 2007 Q4

Max Projection

Avg Projection

Created: Feb-26-08 11:46 AM

(1) Range bars created using one data point for each OEM.

(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 green bar represents an engineering judgment of the uncertainty due to data and methodology limitations. Projections will change

 as additional data are accumulated.

Figure 20: Hours Accumulated and Projected Hours to 10% Stack Voltage Degradation (CDP1) 

25
DOE Fleet

High Current Time

Hot Starts

Starts/hour

Low Voltage Time

High Voltage Time

Cold Starts

Short Trips

0 Speed Trips

Hot Ambient Temp

H*

H*

1) On-going fuel cell degradation study using Partial Least Squares (PLS) 

regression model for combined Learning Demonstration Fleet.

2) DOE Fleet model has a low percentage of explained decay rate variance. 

Created: Feb-21-08 9:32 AM

H*: Factor group associated with high decay rate fuel cell stacks

L**: Factor group associated with low decay rate fuel cell stacks

Due to differences among teams, the 

DOE Fleet Analysis results are spread 

out and concrete conclusions are difficult 

to draw.

Individual team analyses (CDP#49) 

focused on patterns within a fleet.

DOE Fleet

High Current Time

Hot Starts

Starts/hour

Low Voltage Time

High Voltage Time

Cold Starts

Short Trips

0 Speed Trips

Hot Ambient Temp

H*

H*

1) On-going fuel cell degradation study using Partial Least Squares (PLS) 

regression model for combined Learning Demonstration Fleet.

2) DOE Fleet model has a low percentage of explained decay rate variance. 

Created: Feb-21-08 9:32 AM

H*: Factor group associated with high decay rate fuel cell stacks

L**: Factor group associated with low decay rate fuel cell stacks

Due to differences among teams, the 

DOE Fleet Analysis results are spread 

out and concrete conclusions are difficult 

to draw.

Individual team analyses (CDP#49) 

focused on patterns within a fleet.

Figure 21: Primary Factors Affecting Learning Demo Fleet Fuel Cell Degradation (CDP48) 

Team 1

High Voltage Time

High Current Time

Hot Ambient Temp

Short Trips

Starts/hour

Team 2

Team 3

Team 4

Hot Starts

Starts/hour

High Voltage Time

Low Current Time

Idle Time

Cold Starts

Warm Ambient Temp

Long Trips

High Voltage Time

Low Current Time

Hot Starts

Idle Time

Short Trips

Starts/hour

1) On-going fuel cell degradation study using Partial Least Squares (PLS) 

regression model for each team.

2) Teams’ PLS models have a high percentage of explained decay rate variance, 

but the models are not robust and results are scattered. 

H*

L**

High Voltage Time

Low Current Time

Idle Time

Low Voltage Time

Cold Starts

Hot Ambient Temp

Short Trips

Starts/hour

H*

H*

H*

H*

L**

L**

H*: Factor group associated with high decay rate fuel cell stacks

L**: Factor group associated with low decay rate fuel cell stacks

Created: Feb-27-08 12:17 PM

Team 1

High Voltage Time

High Current Time

Hot Ambient Temp

Short Trips

Starts/hour

Team 2

Team 3

Team 4

Hot Starts

Starts/hour

High Voltage Time

Low Current Time

Idle Time

Cold Starts

Warm Ambient Temp

Long Trips

High Voltage Time

Low Current Time

Hot Starts

Idle Time

Short Trips

Starts/hour

1) On-going fuel cell degradation study using Partial Least Squares (PLS) 

regression model for each team.

2) Teams’ PLS models have a high percentage of explained decay rate variance, 

but the models are not robust and results are scattered. 

H*

L**

High Voltage Time

Low Current Time

Idle Time

Low Voltage Time

Cold Starts

Hot Ambient Temp

Short Trips

Starts/hour

H*

H*

H*

H*

L**

L**

H*: Factor group associated with high decay rate fuel cell stacks

L**: Factor group associated with low decay rate fuel cell stacks

Created: Feb-27-08 12:17 PM

Figure 22: Primary Factors Affecting Learning Demo Team Fuel Cell Degradation (CDP49) 

26
Driving Start Time - Day: DOE Fleet

9%

3

12

9

6

DOE Fleet

NHTS

Created: Feb-27-08 10:51 AM

Total Driving3 % of driving trips b/t 6 AM & 6 PM: 88.7% Events = 139968

1. Driving trips between 6 AM & 6 PM

2. The outer arc is set at 12 % total Driving.

3. Some events not recorded/detected due to data noise or incompleteness.

AM PM

% of NHTS trips b/t 6 AM & 6 PM: 81.5%

2001 NHTS Data Includes Car, Truck, Van, & SUV day trips

ASCII.csv Source: http://nhts.ornl.gov/download.shtml#2001

Figure 23: Driving Start Time – Day (CDP44) 

Driving Start Time - Night: DOE Fleet

3%

3

12

9

6

DOE Fleet

NHTS

Created: Feb-27-08 10:51 AM

Total Driving3 % of driving trips b/t 6 PM & 6 AM: 11.3% Events = 139968

1. Driving trips between 6 PM & 6 AM

2. The outer arc is set at 12 % total Driving.

3. Some events not recorded/detected due to data noise or incompleteness.

PM AM

% of NHTS trips b/t 6 PM & 6 AM: 18.4%

2001 NHTS Data Includes Car, Truck, Van, & SUV day trips

ASCII.csv Source: http://nhts.ornl.gov/download.shtml#2001

Figure 24: Driving Start Time – Night (CDP51) 

27
Sunday Monday Tuesday Wednesday Thursday Friday Saturday 0

5

10

15

20

Driving Trips by Day of Week: DOE Fleet

% of Driving Trips in a Day

Day

DOE Fleet

NHTS

Created: Feb-27-08 10:51 AM

2001 NHTS Data Includes Car, Truck, Van, & SUV day trips

ASCII.csv Source: http://nhts.ornl.gov/download.shtml#2001

Figure 25: Driving by Day of Week (CDP45) 

Safety Reports - Vehicle Operation

0

1

2

3

2005 Q2

2005 Q3

2005 Q4

2006 Q1

2006 Q2

2006 Q3

2006 Q4

2007 Q1

2007 Q2

2007 Q3

2007 Q4

Number of Reports

Tank Scratch

Traffic Accident

H2 Leak - During Fueling

H2 Alarm - Stack

H2 Alarm - Fuel System

H2 Alarm - Passenger Compartment

Created: 2/15/08 9:00 AM

Figure 26: Safety Reports – Vehicles (CDP9) 

28
-30

-20

-10

0

10

20

30

40

50

60

1.4oF

122.9oF

Degrees Celsius

Ambient Temperature During Operation

All OEMs

Created: Feb-14-08 5:40 PM

Figure 27: Range of Ambient Temperature during Vehicle Operation (CDP21) 

Vehicle Hours: All OEMs Combined

0

2

4

6

8

10

12

14

16

18

0-150

150-300

300-450

450-600

600-750

750-900

900-1050

1050-1200

1200-1350

>1350

Total Vehicle Hours

Number of Vehicles

Through 2007 Q4

Created: Feb-15-08

Total Vehicle Hours = 52,268

Figure 28: Vehicle Operating Hours (CDP22) 

29
Vehicle Miles: All OEMs Combined

0

2

4

6

8

10

12

14

16

0-3500

3500-7000

7000-10500

10500-14000

14000-17500

17500-21000

21000-24500

24500-28000

28000-31500

>31500

Total Vehicle Miles

Number of Vehicles

Total Miles Traveled = 1,105,440

Through 2007 Q4

Created: Feb-15-08

Figure 29: Vehicles vs. Miles Traveled (CDP23) 

Cumulative Vehicle Miles Traveled: All OEMs

-

200,000

400,000

600,000

800,000

1,000,000

1,200,000

2005Q2

2005Q3

2005Q4

2006Q1

2006Q2

2006Q3

2006Q4

2007Q1

2007Q2

2007Q3

2007Q4

Vehicle Miles Traveled

Created: Feb-15-08

Figure 30: Cumulative Vehicle Miles Traveled (CDP24) 

30
On-Board Hydrogen Storage Methods

-

10

20

30

40

50

60

70

80

90

100

2005Q2

2005Q3

2005Q4

2006Q1

2006Q2

2006Q3

2006Q4

2007Q1

2007Q2

2007Q3

2007Q4

Cumulative Vehicles Deployed

Liquid H2

700 bar tanks

350 bar tanks

Created Feb-08-2008 8:57AM

92

Figure 31: Vehicle Hydrogen Storage Technologies (CDP25) 

99.73

99.74

99.75

99.76

99.77

99.78

99.79

99.8

99.81

99.82

99.83

99.84

99.85

99.86

99.87

99.88

99.89

99.9

99.91

99.92

99.93

99.94

99.95

99.96

99.97

99.98

99.99

100

Hydrogen Fuel Quality Index (%)

Hydrogen Fuel Quality Index Sampled from Stations(1)

Data Range

Data

SAE J2719

Created: Feb-15-08 2:10 PM

(1) Includes sampling from both electrolysis and reforming

Figure 32: Hydrogen Purity Scatter Plot (CDP27) 

31
0 1 2 3 4 5 6 7 8 9 10

Particulates 

μg/L

H2

 Impurities

Data Range SAE J2719 Measured Less Than or Equal To (Detection Limited)

0 500 1000 1500 2000 2500 3000

(N2 + He + Ar) 

0 5 10 15 20 25 30 35 40

H20 

Total HC 

O2 

CO2 

CO 

NH3 

μmol/mol (ppm)

0 10 20 30 40 50 60 70 80 90 100

Total S* 

nmol/mol (ppb) Created: Feb-15-08 2:10 PM *Calculated from SO2, COS, H2S, CS2, and Methyl Mercaptan (CH3SH).

Figure 33: Hydrogen Impurities Scatter Plot (CDP28) 

0 20 40 60 80 100 120 140 160

Adjustment

Check Only

Other

Repair

Replacement

Maintenance: Average Labor Hours Per Station Since Inception

Through 2007 Q4

Scheduled

Un-Scheduled

0 5 10 15 20 25 30 35

Adjustment

Check Only

Other

Repair

Replacement

Maintenance: Average Number of Events Per Station Since Inception

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

# of Events

Hours

Comparison of Scheduled/Un-Scheduled Maintenance

Created: Feb-13-08 4:54 PM

Figure 34: Infrastructure Maintenance (CDP30) 

32
0 20 40 60 80 100 120

Non-Event

Near Miss

Incident

Number of Reports

Severity

Total Infrastructure Safety Reports by Severity

and Report Type Through 2007 Q4

Alarms Only

Automatic System Shutdown

Electrical Issue

Equipment Malfunction

False Alarm/Mischief

H2 Release - Minor, NO Ignition

H2 Release - Significant, NO Ignition

Non-H2 Release

Structural Issue

System Trouble, not Alarm

Created: Feb-15-08 1:24 PM

An INCIDENT is an event that results in:

 - a lost time accident and/or injury to personnel

 - damage/unplanned downtime for project equipment, facilities or property

 - impact to the public or environment

 - any hydrogen release that unintentionally ignites or is sufficient to sustain a flame if ignited

 - release of any volatile, hydrogen containing compound (other than the hydrocarbons used as common fuels)

A NEAR-MISS is:

 - an event that under slightly different circumstances could have become an incident

 - unplanned H2 release insufficient to sustain a flame

Figure 35: Safety Reports – Infrastructure (CDP20) 

0 20 40 60 80 100 120

Non-Event

Near Miss

Incident

Number of Reports

Severity

Primary Factors of Infrastructure Safety Reports

Through 2007 Q4

Calibration/Settings/ Software Controls

Design Flaw

Environment (Weather, Power Disruption, Other)

Inadequate Training, Protocol, SOP

Inadequate/ Non-working Equipment

Maintenance Required

Mischief, Vandalism, Sabotage

New Equipment Materials

Not Yet Determined

Operator/Personnel Error

Created: Feb-15-08 1:24 PM

An INCIDENT is an event that results in:

 - a lost time accident and/or injury to personnel

 - damage/unplanned downtime for project equipment, facilities or property

 - impact to the public or environment

 - any hydrogen release that unintentionally ignites or is sufficient to sustain a flame if ignited

 - release of any volatile, hydrogen containing compound (other than the hydrocarbons used as common fuels)

A NEAR-MISS is:

 - an event that under slightly different circumstances could have become an incident

 - unplanned H2 release insufficient to sustain a flame

Figure 36: Primary Factors of Infrastructure Safety Reports (CDP37) 

33
2005Q2 2005Q3 2005Q4 2006Q1 2006Q2 2006Q3 2006Q4 2007Q1 2007Q2 2007Q3 2007Q4 0

5

10

15

Reporting Period

Number of Stations

Infrastructure Safety Trend and Online Stations Through 2007 Q4

Number of Online Stations

Avg Refuelings Between Safety Reports

Created: Feb-15-08 1:24 PM

0

50

100

150

200

250

Number of Refuelings

7 13

34

41

114

125 129

43

67

114

89

Figure 37: Average Refuelings between Infrastructure Safety Reports (CDP35) 

2005Q2 2005Q3 2005Q4 2006Q1 2006Q2 2006Q3 2006Q4 2007Q1 2007Q2 2007Q3 2007Q4 0

5

10

15

20

25

Reporting Period

Number of Reports

Type of Infrastructure Safety Reports by Quarter Through 2007 Q4

Incident

Near Miss

Non-Event

Stations Online

Avg # Reports/Station

Created: Feb-15-08 1:24 PM

An INCIDENT is an event that results in:

 - a lost time accident and/or injury to personnel

 - damage/unplanned downtime for project equipment, facilities or property

 - impact to the public or environment

 - any hydrogen release that unintentionally ignites or is sufficient to sustain a flame if ignited

 - release of any volatile, hydrogen containing compound (other than the hydrocarbons used as common fuels)

A NEAR-MISS is:

 - an event that under slightly different circumstances could have become an incident

 - unplanned H2 release insufficient to sustain a flame

Figure 38: Type of Infrastructure Safety Report by Quarter (CDP36) 

34
0 2 4 6 8 10 12 14 16 18 20 0

200

400

600

800

1000

1200

1400

Time (min)

Number of Fueling Events

Histogram of Fueling Times

All Light Duty Through 2007Q4

Average = 3.43

 % <5 = 87

Created: Feb-15-08 1:44 PM

Figure 39: Refueling Times (CDP38) 

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

50

100

150

200

250

300

350

Amount Fueled (kg)

Number of Fueling Events

Histogram of Fueling Amounts

All Light Duty Through 2007Q4

Average = 2.25

Created: Feb-15-08 1:44 PM

Figure 40: Refueling Amounts (CDP39) 

35
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0

100

200

300

400

500

600

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

All Light Duty Through 2007Q4

5 minute fill of

5 kg at 350 bar

3 minute fill of

5 kg at 350 bar

Average = 0.79

 % >1 = 24

2006 Tech Val Milestone

2010 MYPP Adv Storage Materials Target

Created: Feb-15-08 1:44 PM

Figure 41: Refueling Rates (CDP18) 

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

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

Comm vs Non-Comm Fills - All Light Duty Through 2007Q4

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 0.94 36%

Non-Comm 0.66 20%

Comm

Non-Comm

2006 Tech Val Milestone

2010 MYPP Adv Storage Materials Target

Created: Feb-27-08 11:26 AM

Figure 42: Fueling Rates – Communication and Non-Communication Fills (CDP29) 

36
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

Avg Fuel Rate (kg/min)

Number of Fueling Events

Histogram of Fueling Rates

All Light Duty by Year Through 2007Q4

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 17%

2006 0.72 20%

2007 0.86 28%

2005

2006

2007

2006 Tech Val Milestone

2010 MYPP Adv Storage Materials Target

Created: Feb-27-08 11:39 AM

Figure 43: Refueling Data by Year (CDP52) 

Tank Levels: DOE Fleet

15%

E F

Created: Feb-27-08 10:51 AM

Total refuelings1 = 13085

1. Some refueling events not recorded/detected due to data noise or incompleteness.

Median Tank Level = 39% at Fill

2. The outer arc is set at 20% total refuelings.

3. If tank level at fill was not available, a complete fill up was assumed.

Figure 44: Hydrogen Tank Level at Refueling (CDP40) 

37
E F

Tank Level Medians: DOE Fleet, All Vehicles

Created: Feb-27-08 10:51 AM

Total refuelings1 = 13085

1. Some refueling events not recorded/detected due to data noise or incompleteness.

2. If tank level at fill was not available, a complete fill up was assumed.

Figure 45: Refueling Tank Levels - Medians (CDP41) 

Refueling by Time of Day: DOE Fleet

9%

3

12

9

6

Created: Feb-27-08 10:51 AM

Total Fill3 % of fills b/t 6 AM & 6 PM: 86.5% Events = 11356

1. Fills between 6 AM & 6 PM

2. The outer arc is set at 12 % total Fill.

3. Some events not recorded/detected due to data noise or incompleteness.

AM PM

Figure 46: Refueling by Time of Day (CDP42) 

38
Refueling by Time of Night: DOE Fleet

5%

3

12

9

6

Created: Feb-27-08 10:51 AM

Total Fill3 % of fills b/t 6 PM & 6 AM: 13.5% Events = 11356

1. Fills between 6 PM & 6 AM

2. The outer arc is set at 12 % total Fill.

3. Some events not recorded/detected due to data noise or incompleteness.

PM AM

Figure 47: Refueling by Time of Night (CDP50) 

Sunday Monday Tuesday Wednesday Thursday Friday Saturday 0

5

10

15

20

Fills by Day of Week: DOE Fleet

% of Fills in a Day

Day

Created: Feb-27-08 10:51 AM

Figure 48: Refueling by Day of Week (CDP43) 

39
Cumulative Hydrogen Produced or Dispensed 

Through 2007 Q4

0

5

10

15

20

25

30

35

40

45

50

2005 Q2

2005 Q3

2005 Q4

2006 Q1

2006 Q2

2006 Q3

2006 Q4

2007 Q1

2007 Q2

2007 Q3

2007 Q4

Calendar Quarter

Mass of Hydrogen (kg) 

(thousands)

0

2

4

6

8

10

12

14

16

Cumulative Hydrogen

Number of Stations

Number of Stations

Created Feb-28-08

Figure 49: Cumulative Hydrogen Produced or Dispensed (CDP26) 

Infrastructure Hydrogen Production Methods 

0

1

2

3

4

5

Delivered

Compressed H2

Natural Gas On-site

Reforming

Electrolysis Delivered Liquid H2

Production Technology

# of Stations

Created Feb-15-08

Figure 50: Infrastructure Hydrogen Production Methods (CDP32) 

40
Online Stations

0

2

4

6

8

10

12

14

16

2005

Q2

2005

Q3

2005

Q4

2006

Q1

2006

Q2

2006

Q3

2006

Q4

2007

Q1

2007

Q2

2007

Q3

2007

Q4

Reporting Period

Number of Stations

Created Feb-15-08

Figure 51: Number of Reporting Stations (CDP31) 

41
F1147-E(09/2007) 

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

April 2008 

2. REPORT TYPE

Technical Report 

3. DATES COVERED (From - To)

 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

4. TITLE AND SUBTITLE

Learning Demonstration Progress Report – Spring 2008 

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

NREL/TP-560-42986 

5e. TASK NUMBER

H2708100 

6. AUTHOR(S)

K. Wipke, S. Sprik, and J. Kurtz 

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

8. PERFORMING ORGANIZATION 

REPORT NUMBER

NREL/TP-560-42986 

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13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

This report documents key results from DOE's Controlled Hydrogen Fleet and Infrastructure Validation and 

Demonstration Project based on data through December 2007. 

15. SUBJECT TERMS

Hydrogen fleet; hydrogen vehicle; hydrogen infrastructure; demonstration; validation; fuel cell vehicle" 

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