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 

SunLine Transit Agency 

Hydrogen-Powered Transit Buses: 

Preliminary Evaluation Results 

K. Chandler 

Battelle 

L. Eudy 

National Renewable Energy Laboratory 

Technical Report 

NREL/TP-560-41001 

February 2007 

NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 
SunLine Transit Agency 

Hydrogen-Powered Transit Buses: 

Preliminary Evaluation Results 

K. Chandler 

Battelle 

L. Eudy 

National Renewable Energy Laboratory 

Prepared under Task No. H270.8200 

Technical Report 

NREL/TP-560-41001 

February 2007 

National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov 

Operated for the U.S. Department of Energy 

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by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337
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Acknowledgements 

This evaluation at SunLine Transit Agency would not have been possible without the support 

and cooperation of many people. The authors thank the following: 

U.S. DOE 

Sigmund Gronich 

John Garbak 

National Renewable Energy Laboratory 

Keith Wipke 

George Sverdrup 

SunLine 

C. Mikel Oglesby 

Tommy Edwards 

Polo Del Toro 

Ed Gallardo 

Karen Thomas 

Mike Hayes 

UTC Power 

Mike Tosca 

Matthew Riley 

Sandy Lajewski 

ISE 

Thomas Blazek 

Tavin Tyler 

Paul Scott 

HyRadix 

Terry Schuster 

 iii
Table of Contents 

Executive Summary........................................................................................................................ 1 

Alternative Fuels and Hydrogen at SunLine............................................................................... 1 

Infrastructure and Facilities ........................................................................................................ 1 

Evaluation Results ...................................................................................................................... 2 

What’s Next for This Demonstration?........................................................................................ 4 

Overview......................................................................................................................................... 5 

Project Design and Data Collection............................................................................................ 6 

Host Site Profile.......................................................................................................................... 7 

Infrastructure and Facilities .......................................................................................................... 13 

Natural Gas Fueling .................................................................................................................. 13 

Natural Gas Fueling Experience ............................................................................................... 15 

Hydrogen Fueling ..................................................................................................................... 15 

Early Hydrogen Fueling Experience......................................................................................... 18 

Maintenance Facilities.............................................................................................................. 20 

Fuel Cell, Hydrogen Engine, and CNG Buses.............................................................................. 22 

Fuel Cell Bus Propulsion System Description.......................................................................... 23 

HHICE Bus Propulsion System Description ............................................................................ 24 

CNG Bus Propulsion System Description ................................................................................ 25 

Early Bus Experience................................................................................................................ 26 

Evaluation Results ........................................................................................................................ 30 

Route Descriptions.................................................................................................................... 30 

Bus Use and Availability .......................................................................................................... 31 

Fuel Economy and Cost............................................................................................................ 33 

Maintenance Analysis............................................................................................................... 35 

Roadcall Analysis ..................................................................................................................... 39 

What’s Next for This Demonstration?.......................................................................................... 40 

Contacts......................................................................................................................................... 41 

Acronyms and Abbreviations ....................................................................................................... 43 

References and Related Reports ................................................................................................... 44 

Appendix: Fleet Summary Statistics............................................................................................. 45 

Appendix: Fleet Summary Statistics – SI Units ........................................................................... 51 

 iv
Executive Summary 

This report provides preliminary evaluation results for one 

prototype fuel cell bus and one prototype hydrogen hybrid 

internal combustion engine (HHICE) bus operating at the 

SunLine Transit Agency (SunLine) in Thousand Palms, 

California (Palm Springs/Coachella Valley area). Purchased 

for $3.1 million and manufactured by Van Hool and ISE 

Corp., the fuel cell bus features an electric hybrid drive 

system with a UTC Power PureMotionTM 120 Fuel Cell 

Power System and ZEBRA batteries for energy storage. 

Purchased for $1.2 million, the HHICE bus from New Flyer has essentially the same electric 

hybrid drive system from ISE Corp., but with ultracapacitors for energy storage and a Ford V10 

Triton engine customized to operate on hydrogen fuel. 

SunLine has been operating both of these hydrogen-fueled transit buses in normal revenue 

service. The evaluation in this report is based on a comparison to five new compressed natural 

gas (CNG) buses operating from the same SunLine location. Purchased for $375,000 each, the 

new CNG buses from Orion Bus Industries use Cummins Westport C Gas Plus natural gas 

engines. 

This evaluation of prototype fuel cell and HHICE transit buses at SunLine is a part of the U.S. 

Department of Energy’s (DOE) Hydrogen, Fuel Cells & Infrastructure Technologies Program, 

which integrates activities in hydrogen production, storage, and delivery with transportation and 

stationary fuel cell applications. This evaluation focuses on documenting progress and 

opportunities for improving the vehicles, infrastructure, and procedures. There is no intent to 

consider the implementation of these hydrogen-fueled transit buses as commercial (or full 

revenue transit service).

Alternative Fuels and Hydrogen at SunLine 

SunLine has been operating its entire fleet and support vehicles on CNG since May 1994. 

SunLine has remained fully committed to operating its fleet on alternative fuels and continues 

that commitment to this day with CNG and hydrogen-fueled transit buses. 

The importance of the demonstration of hydrogen-fueled fuel cell and internal combustion 

engines is to further the development and create enough hydrogen demand to make onsite 

production of hydrogen cost-effective. The fuel cell technology produces only emissions of 

water and a small amount of waste hydrogen. The use of hydrogen in internal combustion 

engines significantly reduces oxides of nitrogen emissions when used alone, as in the case of the 

HHICE bus and when used as a blend with CNG. 

Infrastructure and Facilities 

Fueling facilities at SunLine include private and public access for CNG, liquefied natural gas 

(LNG), compressed hydrogen, and a blend of hydrogen and CNG. SunLine has hydrogen 

production on site from a HyRadix natural gas reformer. When SunLine first began testing 

 1
hydrogen buses, it built a special onsite maintenance facility. The building is located behind the 

CNG bus maintenance building and is essentially a tent designed to vent hydrogen through its 

roof. This type of structure can provide a low-cost option to an agency in warmer climates, such 

as SunLine. 

 

Evaluation Results 

The evaluation periods presented in this report are as follows: 

• Fuel Cell Bus – January 2006 through November 2006 (11 months of operation) 

• HHICE Bus – January 2006 through November 2006 (11 months of operation) 

• New CNG Buses – July 2006 through November 2006 (5 months of operation) 

SunLine Routes – SunLine operates 12 fixed routes in the Coachella Valley along State 

Highway 111 and Interstate 10. Bus service averages 13.4 mph during the week and 12.7 mph 

on the weekend to give a weekly average of 13.2 mph. The fuel cell bus has been used on Line 

50 and Line 111. The HHICE bus has been used almost exclusively on Line 50. The CNG 

buses in this evaluation have been used randomly on all routes/lines from the Thousand Palms 

operation. 

Bus Use and Availability – Bus use and availability are indicators of reliability. Lower bus 

usage may indicate downtime for maintenance, repair, or purposeful reduction of planned work 

for the buses. Availability is the percent of time that the buses are planned for operation 

compared to the time the buses are actually available for that planned operation. The availability 

goal is 85% for all buses. During the evaluation period, the CNG buses essentially met the goal. 

The HHICE bus was at or above the availability target except for July-August 2006. During this 

timeframe, the HHICE bus was held out of service because of a lack of hydrogen during the 

installation of the new HyRadix reformer unit. 

The fuel cell bus availability was much lower than the target during May through September 

2006 because of problems with the air conditioning and fuel cell systems. When the air 

conditioning and fuel cell systems were operating properly, the availability was generally close 

to target. 

Fuel Economy and Cost – Figure ES-1 shows hydrogen and CNG fuel economy by month 

during the evaluation periods. Using the gasoline gallon equivalent (GGE) fuel economy (this is 

essentially the same as miles per kg for the hydrogen-fueled buses) with the CNG buses as the 

baseline, the fuel economy of the fuel cell bus was 149% higher than the CNG buses and the fuel 

economy of the HHICE bus was 46% higher than the CNG buses. The fuel economy of the fuel 

cell bus was 71% higher than the HHICE bus. 

Maintenance Costs – Total maintenance costs for the three study groups of buses are not 

intended to include warranty work; however, further study is planned for the final report to better 

assess the warranty work costs. The CNG buses have the lowest total maintenance cost at $0.25 

per mile. The fuel cell bus and HHICE bus have per mile maintenance costs that are 76% higher 

($0.44 per mile) and 2.2 times higher ($0.55 per mile), respectively, than the baseline/CNG 

buses. 

 2
0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

Jan-06

Feb-06

Mar-06

Apr-06

May-06

Jun-06

Jul-06

Aug-06

Sep-06

Oct-06

Nov-06

Miles per Gallon/kg

FC1 miles/kg HHICE miles/kg CNG miles/GGE

Figure ES-1. Monthly average fuel economy (miles per kg or GGE) 

Specific Experience Fuel Cell Bus – The fuel cell bus was delivered in November 2005 and 

placed into revenue service in December 2005. Both ISE and UTC Power have a technician 

available to SunLine for warranty support of the fuel cell bus, and SunLine reports that this 

support has been excellent. 

There have been a few significant issues with the fuel cell bus so far: 

1. ZEBRA batteries – These batteries have had significant problems in this application. 

The main challenges have been accommodating cell failures and optimizing the state of 

charge (SOC) algorithm. 

2. Air conditioning – SunLine’s summer operation exposes buses to extreme heat 

conditions, with average high temperatures reaching the 110-120° F range. Also, this 

hybrid design is unique because the air conditioning unit is driven electrically instead of 

mechanically (by belt) like most vehicles. In this application, the system has experienced 

problems with failed evaporator and condenser motors. 

3. UTC Power PureMotionTM 120 Fuel Cell Power System – UTC Power monitors the 

performance of the fuel cell power system remotely to analyze actual performance vs. 

predicted performance. In June 2006, UTC Power observed that the CSA (cell stack 

assembly) performance was decaying at high current densities at rates that were beyond 

what was predicted and required for a minimum 4,000-hour fuel cell life. 

With the SunLine bus accumulating the most hours early on, the issue was observed there 

first. On June 30, 2006, the fuel cell power system in the SunLine bus was removed and 

sent to UTC Power in Connecticut for advanced testing. To minimize down time, a 

spare, developmental UTC Power fuel cell power system was installed on July 6, 2006. 

 3
An engineering investigation determined that contaminants were released from a CSA 

material due to a supplier quality control problem with that material. As part of UTC 

Power’s ongoing development, it has modified the CSAs, thus eliminating this condition 

for all builds. Between September 25 and 27, 2006, the developmental fuel cell power 

system was removed and replaced with a new unit that incorporated the new CSA design. 

Specific Experience HHICE Bus – This bus is currently a one-of-a-kind application. It was 

developed in 2004 and delivered to SunLine for operation in December 2004. The HHICE bus 

did not stay long at SunLine before it was shipped to Winnipeg, Manitoba, Canada for 

winter/cold weather testing. The HHICE bus was away from SunLine from approximately 

January 16, 2005 through April 20, 2005 before resuming operation at SunLine in May 2005. 

The bus was test-driven in Canada during February and March 2005 on a regular Winnipeg 

Transit route. In later operation at SunLine, the HHICE bus engine experienced significant 

failure of components during October and November 2005. This failure was caused by an 

incorrectly installed crankshaft damper. A new engine was installed into the HHICE bus in 

December 2005. The bus resumed revenue service later that month. The evaluation results 

presented in this report are focused on the operation of the newer engine. 

Specific Experience with New CNG Buses – SunLine has been operating an all CNG fleet 

since May 1994; however, that fleet of buses is now reaching the end of its usable life. The bus 

bodies have done well in the desert climate, but the engines are a first generation natural gas 

design. A phased approach to the replacement of the CNG bus fleet was designed and the first 

15 new CNG Orion V high floor buses were ordered as part of an existing order by Fresno Area 

Express. These new CNG buses were delivered in June 2006. SunLine reported that the new 

bus order had some minor quality control issues with the bus systems (as all bus orders seem to 

have), but start-up of operations with these 15 CNG buses went well. The main challenge for 

SunLine has been the fact that newer buses (regardless of propulsion) have significant upgrades, 

such as multiplexed controls onboard. While the mechanics have had to undergo additional 

training on these new systems, SunLine staff has reportedly embraced the new technology and is 

quickly catching up. 

Roadcall Analysis – A roadcall (RC) or revenue vehicle system failure (as named in the 

National Transit Database) is defined as a failure of an in-service bus that causes the bus to be 

replaced on route or causes a significant delay in schedule. The CNG buses have had very few 

RCs. The fuel cell and HHICE buses have had several RCs and lower vehicle usage (about half 

or less that of the baseline CNG buses), which is indicative of the prototype nature of these two 

buses. Compared to the fuel cell bus, the HHICE bus has a slightly higher miles-between-RC 

rate. 

What’s Next for This Demonstration? 

This report covers SunLine’s operation of the fuel cell, HHICE, and CNG buses through 

November 2006. The next evaluation report for this site will include at least 12 months of 

operation for the CNG buses, which will require the evaluation period to run through at least 

June 2007. The next evaluation report is planned for release around November 2007. 

 4
Overview 

This report provides preliminary results from an evaluation of prototype fuel cell and hydrogen 

internal combustion engine-equipped transit buses operating at SunLine in Thousand Palms, 

California. Preliminary evaluation results are also provided for new CNG transit buses for a 

baseline comparison to the prototype hydrogen-fueled transit buses. This report describes the 

equipment used (buses and infrastructure) and provides early experience details, lessons learned, 

and results from the operation of the buses and supporting hydrogen and CNG fuel stations 

through November 30, 2006. 

This evaluation is part of DOE’s Hydrogen, Fuel Cells & Infrastructure Technologies (HFCIT) 

Program, which integrates activities in hydrogen production, storage, and delivery with 

transportation and stationary fuel cell applications. DOE’s National Renewable Energy 

Laboratory (NREL) works with fleets and industry groups to test advanced technology, heavyduty vehicles in service and provides unbiased information resources for fleet managers 

considering these technologies. Information collected during vehicle performance and operation 

evaluations is fed back to research programs to help shape future work. 

In early 2003, DOE initiated the Controlled Hydrogen Fleet and Infrastructure Demonstration 

and Validation Project, which focuses on light-duty fuel cell vehicles and supporting 

infrastructure. The purpose of the project is to examine the impact and performance of fuel cell 

vehicles and supporting hydrogen infrastructure in real-world applications. The data collected 

and analyzed during this “learning demonstration” are used to verify performance targets to 

assess technology readiness. To coordinate efforts, the fuel cell bus evaluation team is working 

closely with the light-duty demonstration project teams. The overall goal of this coordination is 

to ensure that similar data for heavy-duty fuel cell vehicles are collected with the intent that this 

will enable a more complete picture of fuel cell performance over a wider range of vehicle 

applications than just light-duty. 

In addition to the light-duty demonstration project, DOE and NREL are also working with the 

FTA, an agency of the U.S. Department of Transportation (DOT), and heavy vehicle operators 

(mostly transit agencies) to demonstrate heavy fuel cell and hydrogen vehicles and to collect 

operations experience data. This collaboration is directly supporting FTA’s National Fuel Cell 

Bus Program (NFCBP). This data collection and evaluation follows the DOE/NREL 

standardized evaluation protocol1

 and detailed data collection templates based on the light-duty 

demonstration. A customized version of the General Evaluation Plan, created for fuel cell bus 

evaluations, is described in the draft Fuel Cell Transit Bus Evaluation Protocol of June 2005. 

Current heavy fuel cell vehicle evaluation sites are shown in Table 1. More information is 

available at 

www.eere.energy.gov/hydrogenandfuelcells/tech_validation/ca_transit_agencies.html. 

 

1

 General Evaluation Plan, Fleet Test & Evaluation Projects, July 2002, NREL/BR-540-32392, 

www.nrel.gov/vehiclesandfuels/fleettest/pdfs/32392.pdf. 

 5
This preliminary data report examines evaluation results from one prototype fuel cell bus, one 

prototype HHICE bus, and five new CNG baseline buses operating from the same SunLine bus 

depot. The evaluation periods presented in this report are as follows: 

• Fuel Cell Bus – January 2006 through November 2006 (11 months of operation) 

• HHICE Bus – January 2006 through November 2006 (11 months of operation) 

• New CNG Buses – July 2006 through November 2006 (5 months of operation) 

Table 1. DOE/NREL Heavy Vehicle Fuel Cell/Hydrogen Evaluations 

Fleet Vehicle/Technology Evaluation Status 

Shuttle bus: Hydrogenics and Enova, 

battery-dominant fuel cell hybrid (one 

bus) 

Shuttle bus in operation, data 

U.S. Air Force/Hickam Air Force Base collection started 

(Honolulu, Hawaii) Delivery van: Hydrogenics and Enova, 

fuel cell hybrid (one van) 

Van in operation, data collection 

started 

Alameda-Contra Costa Transit District 

(AC Transit) 

(Oakland, California) 

Van Hool/UTC Power fuel cell hybrid 

transit bus integrated by ISE Corp. 

(three buses) 

Evaluation in process, all three 

buses in operation since March 

2006, full service started in April 

2006; preliminary evaluation results 

reported Feb 2007 

New Flyer ISE Corp. hydrogen internal 

combustion engine transit bus (one 

bus-HHICE) 

Evaluation in process, preliminary 

evaluation results reported here SunLine Transit Agency 

(Thousand Palms, California) Van Hool/UTC Power fuel cell hybrid 

transit bus integrated by ISE Corp. 

(one bus-FCB) 

Evaluation in process, preliminary 

evaluation results reported here 

VTA (San Jose, California) and 

SamTrans (San Carlos, California) 

Gillig/Ballard fuel cell transit bus (three 

buses) Completed and reported in 2006 

SunLine Transit Agency 

(Thousand Palms, California) 

ISE Corp./UTC Power ThunderPower 

hybrid fuel cell transit bus (one bus) Completed and reported in 2003 

Project Design and Data Collection 

As mentioned earlier, DOE/NREL evaluation projects focus on using a standardized process for 

data collection and analysis, communicating results clearly, and providing an accurate and 

complete evaluation. The objectives of the data collection are to validate fuel cell and hydrogen 

technologies in bus applications to: 

• Determine the status of fuel cell systems for buses and corresponding hydrogen 

infrastructure 

• Provide feedback for DOE HFCIT Program research and development 

• Provide “lessons learned” on implementing next generation fuel cell systems into bus 

operations. 

This evaluation includes prototype fuel cell-powered and hydrogen internal combustion engineequipped transit buses (40 foot) operating at SunLine in Thousand Palms, California (buses 

shown in Figure 1). Five new CNG buses (shown in Figure 2) were selected from SunLine’s 

newest order of Orion CNG buses operating at the same depot (Thousand Palms). Data were 

collected in parallel for the two prototype buses during the evaluation periods, which ended in 

November 2006. The CNG baseline data were collected and analyzed along side the prototype 

transit buses to assess the progress of the hydrogen propulsion development (fuel cell and 

internal combustion engine) for heavy vehicles and specifically in this application at SunLine. 

 6
 Figure 1. Fuel cell (left) and HHICE (right) transit buses at SunLine 

Figure 2. New Orion V CNG bus at SunLine 

Data for this evaluation were taken from SunLine’s data system. Data parameters included: 

• CNG fuel consumption by vehicle and fill 

• Hydrogen fuel consumption by vehicle and fill 

• Mileage data and route assignments from every vehicle in the study 

• Preventive maintenance action work orders, parts lists, labor records, and related 

documents 

• Records of unscheduled maintenance, including roadcalls and warranty actions by 

vendors (when available in the data system). 

Additional information has been collected on the maintenance/operation experience, issues at the 

hydrogen fueling station and SunLine facilities, and lessons learned at the start-up and during the 

operation of the prototype buses. 

Host Site Profile 

SunLine (www.sunline.org) is located in the Palm Springs/Coachella Valley, Calif., area and 

serves an area greater than 1,100 square miles (Figure 3). The Coachella Valley is a desert 

valley region with annual rainfall around five inches per year. Average high temperatures are 

typically above 80° F for eight months of the year, and can get as high as 120° F. 

Transit bus operations started in 1977 with 22 vehicles. SunLine provides bus service from two 

locations in the Valley – one in Thousand Palms, which serves as headquarters, and another in 

Indio (both locations shown in Figure 4). In fiscal year 2006, ridership was reported as 

 7
approximately 3.5 million passengers, the fleet operated 2.8 million miles, and SunLine had an 

operating budget of $18.2 million. 

Figure 3. SunLine operating area in the Coachella Valley, California 

 Figure 4. SunLine headquarters in Thousand Palms (left) and Indio bus garage (right) 

SunLine is a Joint Powers Authority (JPA) created by its nine member cities as well as the 

county (Riverside). Each member city and the county have an appointed member on the 

SunLine board. 

 8
• Desert Hot Springs 

• Palm Springs 

• Cathedral City 

• Rancho Mirage 

• Palm Desert 

• Indian Wells 

• La Quinta 

• Indio 

• Coachella 

• Additional board member from Riverside County 

SunLine operates 12 fixed routes (SunBus) and provides paratransit services (SunDial). The 

current bus fleet includes 48 full size transit buses (40 foot) including 46 CNG buses, one New 

Flyer HHICE bus, and one Van Hool fuel cell bus. The fleet also includes 23 CNG paratransit 

vehicles and 35 light- and medium-duty CNG vehicles. 

Alternative Fuels. SunLine started looking for a defining position on clean bus operations in 

1991. At that time, a decision was made to convert the entire SunLine fleet (buses and support 

vehicles) to CNG in order to maximize the impact of potential emissions reductions and 

economic benefits. This decision was made at a very early stage in CNG bus development and 

deployment in the United States. For context, in 1991 approximately 25 heavy CNG buses had 

just been placed into service in this country, with another 70 on order. 

As background for SunLine’s interest in alternative fuels, the State of California has identified 

some severe air quality challenges, especially in the Los Angeles metropolitan area. The 

Coachella Valley, including Palm Springs, is located in Riverside County, which is one of the 

four counties (Los Angeles, Orange, Riverside, and San Bernardino counties) included in the Los 

Angeles metropolitan area. Starting in the late 1980s and early 1990s, the California Air 

Resources Board (CARB) began to strongly encourage alternative fuels for vehicles to help with 

emissions reductions. The South Coast Air Quality Management District (SCAQMD) launched 

several incentive programs for conversion of vehicles in the district to alternative fuels. One of 

these incentive programs focused on transit buses because of the potential significant emissions 

impact in urban areas. 

The SunLine board of directors approved a 100% alternative fuels approach in 1992 and took 

advantage of local and state incentives for purchasing alternative fuel vehicles. Natural gas 

vehicle training programs were developed at the College of the Desert’s Energy Technology 

Training Center, and the SunLine mechanics were the first “graduates” of that training. All 

SunLine employees received some natural gas vehicle safety familiarization training. SunLine 

was the nation’s first fleet to change to 100% CNG bus operations, which occurred essentially 

overnight in May 1994. An NREL report documenting SunLine’s first 10 years of CNG 

operations experience is available2. Since May 1994, SunLine has remained fully committed to 

 

2

 NREL, 2006, “Ten Years of Compressed Natural Gas Operations at SunLine Transit Agency,” 

http://www.nrel.gov/vehiclesandfuels/ngvtf/pdfs/39180.pdf 

 9
operating its entire fleet on alternative fuels and continues that commitment to this day with 

CNG and hydrogen-fueled transit buses. 

Experience with Hydrogen. SunLine has successfully taken advantage of its unique 

capabilities with gaseous fuels, small size, and high temperature/low humidity location for 

attracting testing projects with government and manufacturer partners. Over the years, many 

projects have involved natural gas, hydrogen, fuel cells, and various combinations of these 

technologies. The objectives for these projects have been to advance clean transit bus propulsion 

systems and leverage project funding to afford SunLine additional equipment and infrastructure. 

Table 2 provides a summary of several hydrogen-related projects at SunLine since the 

installation of onsite hydrogen production and dispensing in 2000. The Ballard P4 fuel cell bus 

(ZEBus) was demonstrated during 2000 and 2001 (shown in Figure 5), but was not used in actual 

revenue service3. The next major project was a development project with NREL and Cummins 

Westport, Inc. (CWI) to develop and demonstrate a natural gas engine capable of using hydrogen 

and CNG blended fuel4

. The second fuel cell bus demonstrated at SunLine was the ISE 

integrated ThunderPower bus powered by UTC Power’s 60 kW fuel cell power system (shown in 

Figure 6) in 2002 through 20035. This fuel cell bus went on to be demonstrated in several 

locations, including AC Transit. 

SunLine and HyRadix (www.hyradix.com) worked together in 2004 to install a natural gas 

reformer to produce high purity hydrogen for use by vehicles. The testing of this HyRadix 

reformer was completed in 2006 and a commercial design was released for purchase. The 

SunLine unit was replaced with the new/commercial design and placed back into service in 

August 2006. 

 

 Figure 5. Ballard P4 ZEBus fuel cell bus Figure 6. ThunderPower fuel cell bus 

The ISE/New Flyer HHICE bus was introduced into service in late 2004. Soon after arriving at 

SunLine, the HHICE bus was shipped to Manitoba, Canada for cold weather testing in February 

and March 20056

. In December 2005, SunLine received its third fuel cell bus; this one was 

developed by ISE, Van Hool, and UTC Power. The HHICE and Van Hool fuel cell bus are 

currently in operation and preliminary evaluation results are provided in this report. SunLine has 

 

3

 Ballard/Xcellsis, 2001, “Customer Report of ZEBus at SunLine Transit,” 

http://www.eere.energy.gov/hydrogenandfuelcells/tech_validation/pdfs/sunline_project_reports2.pdf 4

 NREL, 2005, “Development and Demonstration of Hydrogen and Compressed Natural Gas Blend Transit Buses,” 

http://www.nrel.gov/vehiclesandfuels/ngvtf/pdfs/38707.pdf 5

 NREL, 2003, “Fuel Cell Transit Buses, ThunderPower Bus Evaluation at SunLine Transit Agency,” 

http://www.eere.energy.gov/hydrogenandfuelcells/tech_validation/pdfs/sunline_report.pdf 6

 Manitoba Energy Science and Technology, 2005, “Cold Weather Demonstration in Winnipeg, Manitoba, Canada” 

 10
expressed its interest in the successful operation of these hydrogen fueled buses and would like 

to add more to its fleet. SunLine has already secured funding for further development of fuel cell 

buses through FTA. SunLine would also like to purchase another HHICE bus if funding can be 

secured. 

Table 2. Hydrogen-Related Activities at SunLine 

Timeframe Activity Description 

2000-2004 Addition of hydrogen dispensing A Stuart Energy electrolyzer was installed for testing and used 

to produce hydrogen; decommissioned and removed in 2004 

2000-2001 Ballard P4 Fuel Cell Bus 

Demonstration (ZEbus) 

Demonstration of the Ballard phase 4 fuel cell bus from July 

2000 through June 2001; still on site as a static display 

2002-2004 Development and testing of a 

hydrogen and CNG blend engine 

Support for development and testing of a Cummins natural gas 

engine to operate on a hydrogen CNG fuel blend. Buses in 

service during 10/2003 and 6/2004; buses retired in 2005. 

2002-2003 Demonstration of ThunderPower 

fuel cell bus 

Demonstration of a small transit bus integrated by ISE, power 

plant from UTC Power; bus demonstrated in other locations; 

currently static display at ISE 

2004-2006 Addition of HyRadix natural gas 

reformer 

Prototype HyRadix natural gas reformer was installed to 

produce high pressure hydrogen for use with the HHICE bus 

and other vehicles using hydrogen. Unit was replaced with 

commercial design in 2006. 

2004-present Demonstration of HHICE bus Demonstration of ISE/New Flyer HHICE bus started in 

December 2004. The bus was tested in Manitoba, Canada 

during February and March 2005, and then returned to SunLine 

for operation. 

2005-present Demonstration of fuel cell bus Demonstration of Van Hool/ISE/UTC Power fuel cell bus started 

in December 2005 

2006-present Upgrade of HyRadix natural gas 

reformer to commercial product 

HyRadix has introduced its natural gas reformer as a 

commercial product; the unit at SunLine was replaced with the 

commercial product design; on November 16, 2006 SunLine 

announced the availability of public hydrogen fueling at its 

Thousand Palms facility 

2006-present FTA National Fuel Cell Bus 

Program announcement 

SunLine received $2.8 million to develop a new fuel cell bus 

plus inclusion into other fuel cell bus studies 

Current Advanced Propulsion Direction at SunLine. In 2003, SunLine’s CEO and CFO 

resigned amidst concerns of mismanagement of funds. Mr. C. Mikel Oglesby was hired as the 

new general manager of SunLine in 2004 and got to work restoring public confidence in 

SunLine, establishing a vision for the future, balancing the budget, and initiating enhancements 

to operations and service. Multiple enhancements to transit operations have been made at 

SunLine in a very short period of time. In 2006, SunLine gained control of its natural gas fueling 

infrastructure (from Clean Energy) and launched SunFuels as an alternative fuels provider. 

Another initiative was to complete a comprehensive operational analysis to evaluate and 

restructure both the fixed-route and paratransit services at SunLine. 

Along with the many hydrogen projects underway, the future of CNG bus operations at SunLine 

is also bright. In September 2006, SunLine announced the arrival of 15 new Orion V CNG buses 

with Cummins C Gas Plus engines (purchased on an existing order from Fresno Area Express 

transit agency). SunLine plans to replace the entire heavy CNG bus fleet by 2009. The next 

order of CNG buses includes five 30-foot buses and eight to ten 40-foot buses (depending on 

available funding), all from New Flyer and all low floor. 

 11
Hydrogen Fuel Use in Transit

Fuel cell propulsion systems provide an opportunity to reduce vehicular emissions to zero 

(except for water vapor and a small amount of waste hydrogen). Typically, transit bus 

demonstrations have been introduction points for new heavy-duty vehicle propulsion 

technologies (i.e., natural gas and hybrid electric). This is because: 

 Transit buses are centrally fueled and maintained. 

 Transit buses typically operate on fixed routes in urban stop-and-go duty cycles. 

 Transit bus size and weight can easily accommodate new technologies. 

 Capital purchases of transit buses and supporting infrastructure are federally supported 

(80% federal share and other funding programs). 

 Transit buses have high visibility and impact because they operate in densely 

populated areas*

Development of fuel cell propulsion systems in full-size transit buses is progressing as shown 

in this evaluation report. At the same time, the development and production of high-purity 

hydrogen at a reasonable price must be a high priority for introduction of fuel cell propulsion to 

be successful (or even possible). Production of hydrogen fuel at a reasonable price requires 

development of large quantity production without large distribution/transportation costs. Using 

hydrogen fuel in transit buses is one opportunity for creating the demand for large quantity 

production and use close to the source (this is mostly focused on high-purity hydrogen 

production from reforming natural gas). 

The current price of a full-size, fuel cell transit bus is reported as $2 to $3 million depending on 

the quantity purchased. This high capital cost minimizes the number of fuel cell transit buses 

that can be purchased and placed into service at any given location. In order to continue 

increasing the use of hydrogen fuel, other lower purchase-price propulsion 

technologies/strategies have been introduced (and tested at SunLine). One strategy is to add 

hydrogen fuel to CNG, typically in an 80% CNG and 20% hydrogen blend. With some minor 

modifications to commercial CNG engines, the existing CNG bus fleet can use some 

hydrogen. Hydrogen/CNG blends also provide a significant benefit in terms of reducing oxides 

of nitrogen (NOx) emissions in the already low-emission CNG technology. 

The second strategy for development of hydrogen fuel use is to introduce hydrogen internal 

combustion engines (ICEs) that use hydrogen directly in the engine. Hydrogen-fueled ICEs, 

such as the engine in the HHICE bus, help build demand and support for hydrogen 

infrastructure while fuel cell technology is being perfected (and purchase prices come down). 

The HHICE bus can be a good candidate for transit agencies because fleet mechanics are 

familiar with the workings of combustion engines. This innate knowledge, therefore, frees up 

maintenance workers to focus on the nuances of using a new gaseous fuel. 

Hydrogen ICEs also have the potential for near-zero emissions. Because the fuel contains no 

carbon, the engine does not produce carbon dioxide or any other carbon compounds. The 

only undesirable emission is NOx. However, operating the ICE at ultra-lean conditions keeps 

the combustion temperature low enough to nearly eliminate NOx without using any 

aftertreatment device. 

* Information excerpted from an FTA presentation at the American Public Transportation Association Bus and 

Paratransit Conference committee meeting in Milwaukee, Wisconsin, May 2003. 

 12
Infrastructure and Facilities 

SunLine’s gaseous fuel experience began in the early 1990s when the agency switched its fleet to 

CNG. Protecting the air quality in the Coachella Valley was the primary reason the agency 

chose to abandon diesel for natural gas. To accomplish 

this conversion, SunLine sought out various partners. 

College of the Desert, a local community college, created 

a training program for alternative fuels. SunLine 

partnered with the local natural gas provider, Southern 

California Gas Company (SoCal Gas), to build the 

fueling infrastructure. The CNG station was completed 

and ready for operation by the end of 1993. The most 

unusual aspect of the station, from a transit perspective, i

the fact that it is open to the public. SunLine recently 

took over full ownership of the station, and now benefits 

fully from the sale of fuel. In addition to CNG, the 

station offers liquefied natural gas (LNG), a blend of 

CNG and hydrogen, and pure hydrogen. Diesel and 

gasoline are not available at SunLine. 

Photo courtesy of SunLine

s 

Natural Gas Fueling 

SunLine has two bus operations sites, and both locations have a CNG fueling station for the bus 

fleet and for public fueling. As mentioned earlier, SunLine and SoCal Gas built the original 

CNG fast fill station at the Thousand Palms facility with construction starting in 1993. In 1997, 

Clean Energy purchased the SoCal Gas portion of the fueling station and operation. The station 

has a public filling station on the outside of the facility at Thousand Palms (Figure 7) and piping 

is run underground to SunLine’s private bus filling station (Figure 8). The public and private 

stations provide CNG at 3,000 psi. SunLine has commitment for funding to upgrade this CNG 

fueling station to provide 3,600 psi fuel, but the funding is not in contract yet. LNG was added 

to this fueling station in 2001. 

Photo courtesy of SunLine

Figure 7. Public fueling at SunLine’s Thousand Palms CNG fueling station 

 13
Figure 8. CNG fueling lane and bus wash (Thousand Palms) 

The CNG fueling station at Thousand Palms includes two 400 hp natural gas compressors from 

Wilson Technologies (shown in Figure 9) and provides a 10-minute CNG fill for a transit bus. 

The station design includes six American Society of Mechanical Engineers (ASME) tubes for a 

buffer to help start the fast fill. 

Figure 9. CNG compressor station (Thousand Palms) 

In 1995, SunLine opened a second operating location in Indio called the Clean Air Center, which 

now operates approximately 40% of SunLine’s service. A CNG fueling station was added at this 

location in 1995. This station includes both public and private fueling, with higher speed fueling 

behind the fence of the facility. One Sulzer and one IMW Industries natural gas compressor 

along with three ASME tubes for a buffer were installed at Indio (Figure 10). Fueling times 

range from 12 minutes up to 20 minutes, depending on demand. Some trucks and support 

vehicles are also fueled at this location from the public side of the station. 

 14
Figure 10. CNG fueling equipment (Indio) 

Natural Gas Fueling Experience 

SunLine personnel expressed that the CNG fueling times were acceptable at both stations. 

Transit agencies typically require fueling equipment that can fill a transit bus in 10 minutes or 

less. Overhauls of the compressors are performed on a 2-year basis, so one compressor is 

overhauled each year while the other compressor is kept in service. 

Drive-aways at the fueling dispenser have been the main safety issue at the public fueling station 

in Thousand Palms. New drivers of light-duty vehicles at the public station have regularly 

ripped hoses off the dispenser. As with public gasoline dispensers, the CNG dispenser hoses 

have a break-away point so that the dispenser is not damaged in the event of a drive-away. The 

hose pulls away from the dispenser and then can be repaired. However, one particular driveaway ripped the entire dispenser out because the hose had wrapped around the dispenser and did 

not have a chance to pull out at the break-away point. 

The transit buses do not generally present the drive-away problem because of a starter cut-out 

switch at the fueling door. When that fueling door is open, the bus cannot be started. All of the 

SunLine vehicles (including paratransit and support vehicles) have starter cut-out switches. 

SunLine has attempted to address the drive-away issue at the public station through training of 

public access consumers and its own employees. Labels with pictorial instructions were also 

added to the dispensers to help alleviate the problem. SunLine personnel reported that the small 

size of their fleet and staff has most likely made it easier to facilitate training and awareness than 

would be the case at a larger operation. 

Hydrogen Fueling 

SunLine has been providing hydrogen fuel for various vehicles on site since 2000. Acting as a 

“test bed” for advanced technologies, SunLine has partnered with various organizations to test 

and optimize hydrogen production technologies. The fleet has demonstrated hydrogen 

 15
production methods, including electrolyzers from two different manufacturers (using energy 

from solar and wind) and natural gas reformers. 

In 2004, HyRadix was selected to demonstrate its prototype natural gas reformer at SunLine 

under a project funded by DOE and SCAQMD. The objectives of the project included 

demonstrating the unit in real-world conditions, evaluating the fill rates for vehicles, and 

evaluating the cost of hydrogen production compared to DOE targets. During the demonstration, 

the reformer provided high purity hydrogen to SunLine and gave HyRadix the opportunity to 

fully test the unit’s capabilities for transit applications. Lessons learned during the 

demonstration have been used to optimize the system for commercialization. For more 

information on the results of the demonstration, refer to the 2005 DOE Annual Merit Review 

Proceedings at www.hydrogen.energy.gov/pdfs/review05/tvp_6_harness.pdf and the Annual 

Progress Report at www.hydrogen.energy.gov/pdfs/progress05/viii_c_3_harness.pdf. 

In June, 2006 SunLine awarded a contract to HyRadix to replace the existing unit with its 

commercial reformer, the Adéo. The cost of a new Adéo reformer from HyRadix starts around 

$750,000. This is the first HyRadix commercial unit to be installed in North America. The 

installation was completed and the unit went into service in August 2006. Funding for the new 

reformer was provided by SCAQMD and FTA. SunLine also purchased a 6-year service 

contract from HyRadix for operation and maintenance of the reformer ($300,000 total). 

On November 16, 2006, SunLine and HyRadix announced the opening of the first hydrogen 

fueling station available to the public. The SunLine public fueling station provides CNG, LNG, 

hydrogen, and blended hydrogen (20%) and CNG (80%) fuel to the public. SunLine estimates 

that this hydrogen fueling infrastructure can produce enough hydrogen to comfortably operate 

five full-size transit buses without running out of fuel for the small hydrogen vehicles expected 

to be fueled at this station. 

The HyRadix Adéo7 is a natural gas reformer that uses a proprietary catalytic auto-thermal 

reforming technology. The reformer generates hydrogen in four steps (as shown in Figure 11): 

1. Sulfur removal – The natural gas is fed through an ambient temperature sulfur 

adsorption device to remove specific impurities, such as the odorant added for leak 

detection. These compounds can affect the performance of the catalysts used in the 

reforming process. 

2. Reforming – The natural gas is converted into a hydrogen-rich product stream through 

auto-thermal reforming, which uses a bi-functional catalyst that promotes two reactions 

(partial oxidation reaction and steam reforming reaction) in the same catalyst bed. 

3. Heat integration – To increase overall efficiency, heat recovered during the process is 

used to pre-heat the feed into the reactor and generate steam for the reforming reaction. 

4. Purification – Pressure swing adsorption (PSA) technology is used to purify the 

hydrogen. 

The resulting purified hydrogen is compressed to 6,000 psi for storage prior to dispensing into 

the buses. The reformer is capable of producing a maximum of 9 kg of hydrogen per hour; 

 

7

 HyRadix specifications 2-page handout, http://www.hyradix.com/common/documents/adeo_specs.pdf 

 16
however the current compressor model is not adequate to keep up with that level of throughput at 

this time. SunLine typically operates the unit at 4.5 kg per hour. The HyRadix reformer unit is 

shown in Figure 12. Onsite storage of hydrogen is approximately 180 kg of hydrogen in nine 

ASME tubes and a tube trailer with another 16 ASME tubes (shown in Figure 13). Figure 14 

shows the hydrogen dispenser, which provides hydrogen to vehicles at a pressure up to 5,000 psi. 

Figure 11. HyRadix hydrogen production process (Courtesy of HyRadix) 

Photo courtesy of SunLine

Figure 12. HyRadix natural gas reformer 

 17
Figure 13. Hydrogen storage at SunLine Photo courtesy of SunLine

Figure 14. Hydrogen dispenser at SunLine 

Early Hydrogen Fueling Experience 

SunLine credits its ease of permitting for the hydrogen station to its extensive work when first 

planning the CNG station. The time spent educating and building relationships with local fire 

marshals, emergency responders, and city and county officials in 1993 paid off when it was time 

to add hydrogen to the site. SunLine was given the green light to proceed based on the following 

facts: 

 18
• The agency was already dealing with flammable, compressed gases in high volumes. 

• Policies and procedures were in place to deal with flammable, compressed gases and 

associated equipment. 

• Formal, ongoing training programs were conducted for all personnel in accordance with 

the requirements for handling gaseous fuels and equipment. 

Figure 15 shows total monthly hydrogen dispensed from the SunLine hydrogen dispenser for 

December 2005 through November 2006. The total fuel used in December 2005 only represents 

about 10 days of bus fueling at the end of the month. The fuel cell bus was just being placed into 

operation at that time. The HHICE bus had undergone an engine replacement and was just 

returning to service (discussed later). March 2006 was a low point for hydrogen dispensing due 

to training completed on both the HHICE and fuel cell buses during the first half of the month 

(this reduced the amount of fuel typically used by each bus). 

The other low point in hydrogen consumption was August 2006. This low point occurred when 

the HyRadix reformer was out of service for its upgrade. At this time, SunLine was filling the 

tube trailer at a chemical plant to supply hydrogen. In order to maximize the hydrogen available 

for the fuel cell bus, the HHICE bus was held out of service for the second half of July 2006 and 

the first half of August 2006. A contributing factor to low hydrogen fuel use from July through 

September 2006 was downtime for the fuel cell bus caused mostly by air conditioning problems, 

but a few fuel cell issues contributed as well. 

Figure 16 shows the average daily hydrogen use from the station. This daily use rate only 

includes days in which hydrogen was dispensed from the station. The hydrogen fueling station 

was used at least once each day for 81% of the days during the period shown. 

0

100

200

300

400

500

600

700

800

900

1000

Dec-05

Jan-06

Feb-06

Mar-06

Apr-06

May-06

Jun-06

Jul-06

Aug-06

Sep-06

Oct-06

Nov-06

Total Monthly H2 (kg) Use

Figure 15. Total monthly hydrogen dispensed 

 19
0.0

5.0

10.0

15.0

20.0

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40.0

Dec-05

Jan-06

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May-06

Jun-06

Jul-06

Aug-06

Sep-06

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Nov-06

H2 Amount (kg) / Day

Figure 16. Average hydrogen dispensed per day (excluding 0 kg days) 

Maintenance Facilities 

In order to support operations and maintenance of CNG buses, SunLine made some 

modifications and upgrades to the maintenance facility in 1995. These included the addition of 

combustible gas detectors and the upgrade of some of the electrical conduit, lighting, and 

ventilation in the maintenance bays. The fueling station and maintenance facility upgrade costs 

at the Thousand Palms location were reported to be $1.47 million in 1995. Figure 17 shows the 

maintenance facility at Thousand Palms. There were no additional costs for the outside bus 

parking areas. 

The combustible gas sensors and alarms in the maintenance facility are required by building 

codes for indoor maintenance of CNG vehicles. The combustible gas detection system is 

designed to alarm at a 20% lower flammability limit (LFL) in air with a siren and lights. At 40% 

LFL the siren and lights latch on, power in the building is turned off, and the vents are opened in 

the roof of the building. The proper operation of this system is tested quarterly and the 

combustible gas detectors are calibrated every six months. 

 20
Figure 17. CNG maintenance facility in Thousand Palms 

When SunLine first began testing hydrogen buses, it built a special onsite facility for 

maintenance (shown in Figure 18). Located behind the CNG bus maintenance building, the 

facility is essentially a tent designed to vent hydrogen through its roof. It consists of an 

aluminum frame covered with fireproof canvas, which is ventilated along the ridgeline with an 

18-inch gap and a 6-inch raised "rain cap" to allow hydrogen gas to safely escape if it is 

inadvertently released from the vehicle. All lighting within the tent structure and adjacent 

maintenance bay is rated Class 1, Division 1. The building is also equipped with sensors that 

sound an alarm if a hydrogen leak is detected. Construction of the building cost approximately 

$50,000 ($21,000 for the building, doors, and ventilation system, and $29,000 for the fire and 

combustible gas sensors and the alarm system). This type of structure can provide a low-cost 

option to an agency in warmer climates, such as SunLine. 

There have been no reported hydrogen leaks in the hydrogen maintenance facility, and no alarms 

have occurred. The system and sensors are checked and calibrated twice a year. 

Figure 18. Hydrogen maintenance building 

 21
Fuel Cell, Hydrogen Engine, and CNG Buses 

Table 3 provides bus system descriptions for the fuel cell, HHICE, and new CNG buses that 

were studied in this evaluation. SunLine unveiled its Van Hool hybrid fuel cell bus from ISE 

Corporation on November 21, 2005 at the Thousand Palms facility. This fuel cell bus started 

revenue service at SunLine in late December 2005. The purchase, manufacturing, and packaging 

of the Van Hool fuel cell bus took about two years and cost approximately $3.1 million. This 

SunLine bus is a sister to three other Van Hool fuel cell buses developed for AC Transit. 

The ISE Corp./New Flyer HHICE bus was purchased by SunLine as part of a joint 

FTA/SCAQMD project in 2004. The bus went into service in December 2004. As mentioned 

earlier, soon after the HHICE bus started operation at SunLine, it was sent to Winnipeg, 

Manitoba, Canada for cold weather testing in February and March 2005, and then resumed 

operation at SunLine. A single new HHICE bus is estimated (by ISE Corp.) to cost between $1 

million and $2 million to purchase today, depending on the number of buses purchased. 

The new CNG buses from Orion were purchased in 2005, and were delivered in June 2006. For 

this evaluation, five buses of an order of 15 new Orion V CNG buses were selected for a baseline 

comparison to the fuel cell and HHICE buses at SunLine. These CNG buses are operated from 

the Thousand Palms operating depot along with the two hydrogen-fueled buses. The purchase 

price reported for these CNG buses ($375,000 each) includes all preparation for SunLine service, 

such as the radio and farebox. 

Table 3. Fuel Cell, HHICE, and CNG Bus System Descriptions 

Operation from Thousand Palms Depot Vehicle System Fuel Cell Bus HHICE Bus CNG Bus 

Number of Buses 1 1 5 

Bus Manufacturer and 

Model 

Van Hool A330 

Low floor 

New Flyer TB-40 

Low floor 

Orion V 

High floor 

Model Year 2005 2004 2006 

Length/Width/Height 40 ft/102 in/139 in 40 ft/102 in/137 in 40 ft/102 in/135 in 

GVWR/Curb Weight 43,240 lb/36,000 lb 40,000 lb/32,032 lb 40,600 lb/29,600 lb 

Wheelbase 228 in 293 in 280 in 

Passenger Capacity 

30 seated or 26 seated 

and two wheelchairs 

15 standing 

39 seated or 33 seated 

and two wheelchairs 

13 standing 

44 seated or 38 seated 

and two wheelchairs 

21 standing 

Engine Manufacturer 

and Model 

UTC Power 

PureMotionTM 120 Fuel 

Cell Power System 

Ford 6.8 liter 

Triton V10 hydrogen Cummins C Gas Plus 

 Drive Motor Rated 

Power 170 kW 150 kW @ 3100 rpm 280 hp @ 2400 rpm 

 Rated Torque 220 Nm 400 lb-ft @ 3250 rpm 850 lb-ft @ 1400 rpm 

Accessories Electrical Electrical Mechanical 

Emissions Equipment None None Catalytic converter 

Transmission/Retarder Gearbox/Flenders 

Regenerative braking 

Gearbox/Flenders 

Regenerative braking 

ZF 5HP592 

Integrated retarder 

Fuel Capacity 50 kg hydrogen 58 kg hydrogen 125 DGE 

Bus Purchase Cost $3.1 million $1 million to $2 million $375,000 

 22
Table 4 provides descriptions of some of the electric propulsion systems for the fuel cell and 

HHICE buses. The electric propulsion systems for these two buses are nearly identical except 

for the energy storage and slightly more hydrogen storage on the HHICE bus. Note that the 

CNG buses are not a hybrid configuration and do not have regenerative braking or energy 

storage for the drive system. 

Table 4. Additional Electric Propulsion System Descriptions 

Propulsion Systems Fuel Cell Bus HHICE Bus 

Manufacturer/Integrator ISE Corporation ISE Corporation 

Hybrid Type Series, charge sustaining Series, charge sustaining 

Drive System Siemens ELFA/ISE Siemens ELFA/ISE 

Propulsion Motor 2-AC induction, 85 kW each 2-AC induction, 85 kW each 

Energy Storage 

Battery – 3 modules/216 cells 

sodium/nickel chloride ZEBRA®; 

53 kWh capacity 

Ultracapacitors – 2 packs/144 

modules each; Maxwell; 0.6 kWh 

capacity 

Fuel Storage Eight, roof mounted, SCI, type 3 

tanks; 5,000 psi rated 

Eight, roof mounted, SCI, type 3 

tanks; 5,000 psi rated 

Regenerative Braking Yes Yes 

Fuel Cell Bus Propulsion System Description 

The prototype fuel cell bus in service at SunLine is the result of a collaboration between ISE 

Corporation (www.isecorp.com), UTC Power (www.utcpower.com), and Van Hool (www.abccompanies.com/sales_vh.htm). The bus uses the PureMotionTM 120 Fuel Cell Power System 

manufactured by UTC Power in a hybrid electric drive system designed by ISE. The Van Hool 

A330 transit bus chassis was redesigned to integrate the fuel cell system. The bus has a low 

floor from front to back and three doors for easy passenger boarding. 

ISE’s hybrid system (shown in Figure 19) is a series configuration, meaning the fuel cell power 

system is not mechanically coupled to the drive axle. The fuel cell power system and energy 

storage system work together to provide power to two electric drive motors, which are coupled to 

the driveline through a combining gearbox. When the bus needs extra power, the fuel cell power 

system and energy storage provide power to the drive motors. When the power requirements of 

the bus are low, the fuel cell power system provides power and recharges the energy storage 

system. 

The hybrid system is also capable of regenerative braking, which captures the energy typically 

expended during braking and uses it to recharge the energy storage system. Each component of 

the propulsion system is carefully controlled through an ISE-developed operating system. 

ISE designed the system to be flexible. Depending on a client’s needs, a variety of powerplants 

and energy storage options can be integrated into the system. The bus at SunLine has a fuel cell 

powerplant and three ZEBRA® (sodium/nickel chloride) batteries (www.betard.co.uk/) as the 

energy storage system. 

The powerplant, which is the primary power source for the hybrid system is UTC Power’s 

PureMotionTM 120 Fuel Cell Power System which produces 120 kW from its proton exchange 

membrane (PEM) fuel cell stacks. UTC Power’s fuel cells operate at near-ambient pressure, 

 23
which eliminates the need for a compressor. This not only increases the efficiency of the system, 

but also results in very quiet operation. 

Figure 19. ISE’s hybrid propulsion system 

HHICE Bus Propulsion System Description 

The HHICE bus was developed by ISE Corporation with cooperation and support from New 

Flyer (www.newflyer.com). The major systems are shown in Figure 20. New Flyer delivered 

the bus to ISE as a “glider” without the power train. The HHICE bus features ISE’s 

ThunderVolt hybrid drive system (essentially the same hybrid system as described above for the 

fuel cell bus at SunLine) and Ford Motor Company’s Triton V10 engine, which is optimized to 

run on hydrogen. ISE’s hybrid system is a series configuration, meaning that the powerplant is 

not mechanically coupled to the drive axle. The powerplant and energy storage system work 

together to provide power to two electric drive motors that are connected to the driveline through 

a combining gearbox. 

As with the fuel cell bus, the hybrid system in the HHICE bus uses regenerative braking to 

recharge the energy storage system. The energy storage system on the HHICE bus consists of 

two packs of Maxwell ultracapacitors (www.maxwell.com). The benefit of using ultracapacitors 

over batteries is the speed at which energy can be stored and retrieved from the capacitors; the 

challenge with ultracapacitors is having enough energy density onboard a vehicle to enable 

efficient use of the energy storage system. Each component of the propulsion system is carefully 

controlled through an ISE-developed operating system. 

 24
Ford V10 H2 Engine 

Control System 

Energy Storage 

Accessories 

Inverter 

Generator 

Drive Motor 

Figure 20. Propulsion system for HHICE bus (courtesy of ISE Corp.) 

CNG Bus Propulsion System Description 

SunLine is in the process of replacing its existing fleet of model year 1994 Orion V CNG buses. 

In June 2006, SunLine received 15 new CNG Orion V buses with Cummins Westport, Inc. 

(CWI, www.cumminswestport.com) C Gas Plus engines (engine shown in Figure 21). 

Development of the “Plus” version of the engine (modifications for better fuel and emission 

control) was supported by DOE and NREL8. Orion Bus Industries (www.orionbus.com) is 

located in Mississauga, Ontario, Canada and Oriskany, N.Y. Both the CNG engine and Orion V 

models are established, commercial products in the transit bus industry. 

 

8

 “On-Road Development of the C-Gas Plus Engine in Heavy-Duty Vehicles,” 2003, NREL/FS-540-32871; “An 

Emission and Performance Comparison of the Natural Gas C-Gas Plus Engine in Heavy-Duty Trucks,” 2003, 

NREL/SR-540-32863. Visit www.eere.energy.gov/afdc to obtain these publications.

 25
Figure 21. CWI C Gas Plus engine 

Early Bus Experience 

SunLine operators and mechanics are used to testing vehicles with new propulsion systems. 

First, they have operated and maintained CNG buses for more than 12 years. Second, SunLine 

staff has been working with hydrogen-fueled vehicles since 2000. The experience with gaseous 

fuels (i.e., CNG) has made the transition to using hydrogen much easier. SunLine has worked 

with the College of the Desert to develop9

 and provide training to its entire staff. 

All new transit bus orders have some break-in issues after delivery. The buses in this evaluation 

are no exception. The following descriptions provide some initial/early experience details for the 

fuel cell, HHICE, and CNG buses operating at SunLine. 

Fuel Cell Bus. The fuel cell bus was delivered in November 2005 and placed into revenue 

service in January 2006. SunLine has only one fuel cell bus and reports that having the bus 

operate in revenue service is extremely important. Both ISE and UTC Power have technical 

support available to SunLine for warranty support of the fuel cell bus, and SunLine reports that 

this support has been excellent. SunLine is responsible for bus maintenance, and UTC Power 

and ISE are responsible for the propulsion and drive system; however, at least one SunLine 

mechanic follows the UTC Power or ISE technicians when repairs are made. 

The drivers of the fuel cell bus were excited about and really liked the bus. It offers a smooth, 

quiet ride and has a comfortable driver’s seat with good access to the controls. This new bus 

also has a hands-free public address system. 

There have been a few significant issues with the fuel cell bus so far: 

1. ZEBRA batteries – These batteries have had significant problems in this application. 

The main challenges have been accommodating cell failures and optimizing the state of 

charge (SOC) algorithm. A cell failure in this serial string causes a short that decreases 

 

9

 Training materials developed by College of the Desert available on the DOE EERE Web site at 

http://www.eere.energy.gov/hydrogenandfuelcells/tech_validation/h2_manual.html 

 26
the overall voltage of a pack (in the group of three packs). Because these batteries 

operate at 300° C, it has also been difficult to make sure that a spare battery is available 

and up to operating temperature for efficient replacement of another battery in the set of 

three batteries. This issue will be discussed later in the evaluation results section. 

2. Air conditioning – SunLine’s summer operation exposes buses to extreme heat 

conditions, with average high temperatures reaching the 110-120° F range. Also, this 

hybrid design is unique because the air conditioning unit is driven electrically instead of 

mechanically (by belt) like most vehicles. In this application, the system has experienced 

problems with failed evaporator and condenser motors. Several changes and upgrades 

have been attempted and the problem seems to be resolved. However, this resolution did 

not occur until after the high heat of summer. Resolution of this issue will be revisited in 

the summer of 2007. 

3. UTC Power PureMotionTM 120 Fuel Cell Power System – UTC Power monitors the 

performance of the fuel cell power system remotely to analyze actual performance vs. 

predicted performance. In June 2006, UTC Power observed that the CSA (Cell Stack 

Assembly) performance was decaying at high current densities at rates that were beyond 

what was predicted and required for a minimum 4,000-hour fuel cell life. The 

performance manifested itself as lowered voltage for a given current at high power levels. 

With the SunLine bus accumulating the most hours early on, the issue was observed there 

first. On June 30, 2006, the fuel cell power system in the SunLine bus (the unit had 

approximately 1,140 hours) was removed from the bus and sent to UTC Power in 

Connecticut for advanced testing that could not be accomplished in the field. Just prior to 

that removal, UTC Power asked SunLine to limit operation to hold the performance 

decay at its current state, which resulted in a short loss of availability. To minimize 

overall down time, the SunLine bus was retrofitted with a spare, developmental UTC 

Power fuel cell power system on July 6, 2006. 

During testing (back at UTC Power in Connecticut), it became apparent to UTC Power 

that the problem was with the CSAs and not a boundary condition issue (such as bad 

fuel). An engineering investigation determined that contaminants were released from a 

CSA material due to a supplier quality control problem with that material, which resulted 

in decayed performance. It should be noted that the issue was performance-related only 

and did not pose any safety issues nor was there a failure of the CSAs. 

As part of UTC Power’s ongoing development, UTC Power has incorporated corrective 

action into the CSAs thus eliminating this condition for all builds. UTC Power replaced 

the SunLine unit with a new fuel cell power system which incorporated the new CSA 

design as well as improvements to balance of plant hardware that were identified during 

the first year of operation. UTC Power wanted to use this opportunity to gain experience 

with the newly designed CSAs and balance of plant. 

On September 25, 2006, the spare fuel cell power system was removed from the SunLine 

bus after accumulating approximately 100 load hours at SunLine. It should be noted that 

 27
the number of load hours was significantly limited because of issues with the air 

conditioning system during that timeframe. The new fuel cell power system was installed 

over September 26 and 27, 2006. 

Now that the upgraded fuel cell power system has been installed in the SunLine bus, 

there is a desire to maximize/accelerate the use of this fuel cell bus. This accelerated 

testing is currently hampered by issues with the ZEBRA battery packs. 

HHICE Bus. This bus is currently a one-of-a-kind application. This bus was developed in 2004 

and delivered to SunLine for operation in December 2004. As mentioned earlier, the HHICE bus 

did not stay long at SunLine before it was shipped to Winnipeg, Manitoba, Canada for 

winter/cold weather testing. The HHICE bus was away from SunLine from approximately 

January 16, 2005 through April 20, 2005 before resuming operation at SunLine in May 2005. 

The bus was test-driven in Canada during February and March 2005 on a regular Winnipeg 

Transit route. 

The HHICE bus reportedly performed well in Canada, carrying more than 1,000 passengers and 

logging more than 300 miles in revenue service. A total of 1,800 miles were accumulated while 

operating in Canada. The bus was able to keep passengers sufficiently warm during operation, 

and was noticeably quieter than conventional diesel buses. As referenced earlier, the results of 

this cold weather testing have been published. Some of the lessons learned and needs identified 

from that testing are as follows: 

• Develop permanent hydrogen facilities for storage, maintenance, and fueling 

• Reduce insurance costs based on continuing experience with operating hydrogen vehicles 

• Develop hydrogen safety training programs 

• Improve systems to measure and control water vapor in hydrogen fuel and reconsider 

hydrogen fuel specification 

In later operation at SunLine, the HHICE bus engine experienced significant failure of 

components during October and November 2005. This failure was caused by an incorrectly 

installed crankshaft damper. A new engine was installed into the HHICE bus in December 2005. 

The bus resumed revenue service later that month. The evaluation results presented later in this 

report focus on the operation of this newer engine; however, some comparisons are made to the 

older engine/first year of operation. 

 

New CNG buses. SunLine has been operating an all CNG fleet since May 1994; however, that 

fleet of buses is now reaching the end of its usable life. The bus bodies have done well in the 

desert climate, but the engines are a first generation natural gas design. In 2004 the new SunLine 

general manager decided that the agency should stay on course with alternative fuels, but that the 

fleet needed to be replaced. A phased approach to the replacement of the CNG bus fleet was 

designed and the first 15 new CNG Orion V high floor buses were ordered as part of an existing 

order by Fresno Area Express. 

These new CNG buses were originally expected in January 2006, but a mix-up in the color 

scheme of the buses delayed delivery until June 2006. SunLine reported that the new bus order 

 28
had some minor quality control issues with bus systems (as all bus orders seem to have), but 

start-up of operations with these 15 CNG buses went well. The main challenge for SunLine has 

been the fact that newer buses (regardless of propulsion) have significant upgrades, such as 

multiplexed onboard controls. While the mechanics have had to undergo additional training, 

SunLine staff has reportedly embraced the new technologies and is quickly catching up. 

One of the changes with the new CNG buses is that SunLine is now able to use a single lube oil 

for the engine, transmission, and hydraulic systems. This has simplified maintenance and 

support (and hopefully cost) of the new CNG buses. Drivers do not appear to have any issues. 

They seem to like the new buses, including the acceleration and air conditioning systems. One 

of the new CNG buses had an engine oil consumption issue, but it was resolved by the Cummins 

dealer. 

 29
Evaluation Results 

The evaluation periods for the three study groups of buses ended in November 2006; however, 

the starting point was different for the CNG buses: 

• Fuel Cell Bus – January 2006 through November 2006 (11 months) 

• HHICE Bus – January 2006 through November 2006 (11 months) 

• CNG Buses – July 2006 through November 2006 (5 months) 

Both the fuel cell and HHICE buses were in service during a portion of December 2005, but this 

is not included in the evaluation because of low bus use during the month. This also helps 

remove some of the start-up issues at the very beginning of operation. This has also been done 

for the new CNG buses. These buses went into service near the end of June 2006, and the 

evaluation period started on July 1, 2006. 

In this evaluation report, both the fuel cell and HHICE buses are considered prototype 

technology that is in the process of being commercialized. The analysis and comparison 

discussions with standard/new CNG buses were done to help baseline the status and progress of 

these two hydrogen propulsion technologies. The intent of this analysis is to determine the status 

of this implementation and document the improvements that have been made over time at 

SunLine. There is no intent to consider this implementation of fuel cell or HHICE buses as 

commercial (or full revenue transit service). The evaluation focuses on documenting progress 

and opportunities for improvement of the vehicles, infrastructure, and procedures. 

Route Descriptions 

SunLine operates 12 fixed routes in the Coachella Valley along State Highway 111 and Interstate 

10. Table 5 shows a weekly summary of bus usage at SunLine, and indicates that bus service 

operates at an average of 12.7 mph on the weekends and 13.4 mph during the week for an overall 

average of 13.2 mph. The weather plays a role in how the SunLine buses are operated. During 

the eight months in the year when the average high temperature is above 80° F, drivers typically 

idle on the shorter layovers to keep the buses cool for passengers. This causes the bus average 

speed to go down and the air conditioning load to go up, both of which have a significant impact 

on fuel efficiency. 

Table 5. Summary of Total Weekly Bus Usage at SunLine 

Day of Week Total Miles Hours Average Speed 

Weekday 30,534.5 2,278.5 13.4 

Weekend 8,777.4 693.8 12.7 

Total 39,311.9 2,972.3 13.2 

Buses at the two SunLine operating locations are generally dispatched randomly. However, the 

HHICE bus has been used almost exclusively on Line 50 (average speed of 14.1 mph), except for 

a few days on Line 30 and Line 31 in January 2006. The fuel cell bus has been used on Line 50 

(operated 112 days) and Line 111 (operated 37 days, average speed of 14.3 mph). In-service 

 30
data indicates an average operating speed of 13.0 mph based on mileage and fuel cell system 

operating hours. The new CNG buses have been randomly dispatched. 

Bus Use and Availability 

Bus use and availability are indicators of reliability. Lower bus usage may be an indication of 

downtime for maintenance or purposeful reduction of planned work for the buses. This section 

provides a summary of bus usage and availability for the three study groups of buses. 

Figure 22 shows mileage and fuel cell system operating hour accumulation for the fuel cell bus 

during the evaluation period (January through November 2006). Total mileage accumulation for 

the evaluation period was 19,208 miles, and the fuel cell system accumulated 1,345 hours. 

These numbers indicate an overall average speed of operation at 13.0 mph, which is nearly the 

same as the overall SunLine operation speed of 13.2 mph. 

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Jan-06

Feb-06

Mar-06

Apr-06

May-06

Jun-06

Jul-06

Aug-06

Sep-06

Oct-06

Nov-06

Total Miles

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Total FC System Hours

Total Miles Total FC System Hours

Figure 22. Cumulative mileage and fuel cell hours for one fuel cell bus 

Table 6 summarizes average monthly mileage accumulation by bus and study group for the 

evaluation periods. Using the CNG buses as the baseline, the fuel cell bus had average monthly 

mileage 40% of CNG operation and the HHICE bus had average monthly mileage 50% of CNG 

operation. 

Another measure of reliability is availability – the percent of time that the buses are planned for 

operation compared to the time the buses are actually available for that planned operation. 

Figure 23 shows the monthly average availability for each of the three study bus groups. As 

shown on the chart, the availability goal is 85% for all buses. The chart shows that the CNG 

buses are essentially right on the goal; however, it should be noted that one CNG bus had 

availability at 63% and the other CNG buses were above the availability target. The HHICE bus 

 31
was at or above the availability target except for July-August 2006. During this timeframe, the 

HHICE bus was out of service because of a lack of hydrogen availability during the installation 

of the new HyRadix reformer unit. 

The fuel cell bus was much lower than the availability target during May through September 

2006 because of problems with the air conditioning and the fuel cell systems, as discussed above 

in the early experience section. When the air conditioning and fuel cell systems were operating 

properly, the availability was generally close to target. 

Table 6. Average Monthly Mileage (Evaluation Period) 

Bus Starting 

Hubodometer 

Ending 

Hubodometer

Total 

Mileage Months Monthly Average 

FC1 2,865 22,073 19,208 11 1,746 

550 HHICE 17,481 41,260 23,779 11 2,162 

563 CNG 4,916 30,021 25,105 5 5,021 

565 CNG 7,637 31,349 23,712 5 4,742 

566 CNG 5,576 20,764 15,188 5 3,038 

567 CNG 7,104 29,427 22,323 5 4,465 

568 CNG 6,388 28,600 22,212 5 4,442 

Total CNG 108,540 25 4,342 

0

10

20

30

40

50

60

70

80

90

100

Jan-06

Feb-06

Mar-06

Apr-06

May-06

Jun-06

Jul-06

Aug-06

Sep-06

Oct-06

Nov-06

Percent Availability

FC1 HHICE CNG

Availability Target 85%

Figure 23. Availability for all three study bus groups 

Table 7 provides a summary of the availability and unavailability reasons for each of the three 

study bus groups. Overall during the evaluation periods, the average availability for the fuel cell 

bus was 61%, the HHICE bus was 80%, and the CNG buses were 86%. Issues that kept the fuel 

cell bus out of service included problems with the air conditioning (36%), fuel cell system 

 32
(33%), and ZEBRA batteries (15%). Issues that kept the HHICE bus out of service included 

problems with the drive system (55%), lack of hydrogen fuel (43%), and general maintenance 

activities (2%). Issues that kept the CNG buses out of service included general maintenance and 

some air conditioning repairs. 

Table 7. Summary of Reasons for Availability and Unavailability of Buses for Service 

Fuel Cell Bus HHICE Bus CNG Buses Category Number Percent Number Percent Number Percent 

Planned Work Days 263 284 690 

Days Available 160 61 228 80 590 86 

Available 160 100 228 100 590 100 

On-Route 149 94 210 92 585 99 

Event/Demonstration 3 2 3 1 0 0 

Training 6 4 13 5 0 0 

Not Used 2 0 6 2 5 1 

Unavailable 103 100 56 100 100 100 

Fuel Cell Propulsion 34 33 

ISE Propulsion 9 9 31 55 

ZEBRA Battery 16 15 

Air Conditioning 36 35 0 0 6 6 

Headsign 7 7 

SunLine Maintenance 0 0 1 2 94 94 

Fueling Unavailable 1 1 24 43 

Fuel Economy and Cost 

Hydrogen fuel is supplied at SunLine by a HyRadix natural gas reformer for compression up to 

5,000 psi into vehicles. CNG is brought into the SunLine property via a high-pressure natural 

gas line and then compressed up to 3,000 psi for delivery into vehicles. SunLine has approved 

funding to upgrade the Thousand Palms natural gas fueling infrastructure to dispense CNG up to 

3,600 psi. 

SunLine provides both hydrogen and CNG for purchase at its public dispensing island. This has 

caused SunLine to track all of its fuels in gasoline gallon equivalent (GGE) units for state fuel 

sales regulations. In the case of hydrogen, the unit used is typically kilograms (kg), and this just 

so happens to be essentially the same energy equivalent as a GGE. The analysis in this report 

presents both GGE (or kg for hydrogen) and diesel gallon equivalent (DGE) for hydrogen and 

CNG fuel consumption. Energy conversion calculations for GGE and DGE are shown in the 

appendix. 

Table 8 shows hydrogen and CNG fuel consumption and fuel economy for the three study bus 

groups during the evaluation periods. Using the GGE fuel economy and the CNG buses as the 

baseline, the fuel cell bus has a fuel economy 2.5 times higher than the CNG buses and the 

HHICE bus has a fuel economy 46% higher than the CNG buses. The fuel cell bus has a fuel 

economy 71% higher than the HHICE bus. Figure 24 shows the average monthly fuel 

economies for each of the three study groups of buses. The average fuel economy line for the 

fuel cell bus fluctuates during May through September. This occurred because of the low 

number of fuelings and limited bus usage during those months due to significant down time, as 

discussed earlier. 

 33
SunLine has tracked the utility (electricity, natural gas, and water) costs along with the costs to 

maintain the HyRadix reformer since the prototype unit was placed into service. They report that 

hydrogen production has cost $4.26 per kg since the reformer started operation to present. This 

hydrogen fuel cost for production indicates that the fuel cell bus fuel cost is $0.58 per mile and 

the HHICE bus fuel cost is $0.99 per mile. 

Table 8. Fuel Use and Economy (Evaluation Period) 

Bus Mileage 

(Fuel Base) 

Hydrogen (kg) 

or CNG (GGE) 

Miles per 

kg or GGE 

Diesel Equivalent 

Amount (Gallon) 

Miles per 

Gallon (DGE)

FC1 19,208 2,622.2 7.33 2,320.5 8.28 

550 HHICE 23,779 5,513.9 4.29 4,879.6 4.85 

563 CNG 25,105 8,592.5 2.92 7,690.3 3.26 

565 CNG 23,712 8,083.6 2.93 7,234.8 3.28 

566 CNG 15,188 4,947.4 3.07 4,427.9 3.43 

567 CNG 22,323 7,546.6 2.96 6,754.2 3.31 

568 CNG 22,212 7,379.4 3.01 6,604.6 3.36 

CNG Total 108,540 36,549.5 2.97 32,711.8 3.32 

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

Jan-06

Feb-06

Mar-06

Apr-06

May-06

Jun-06

Jul-06

Aug-06

Sep-06

Oct-06

Nov-06

Miles per Gallon/kg

FC1 miles/kg HHICE miles/kg CNG miles/GGE

Figure 24. Monthly average fuel economy (miles per kg or GGE) 

SunLine provides CNG fuel for its entire bus operation and sells CNG to the public. This large 

volume of CNG allows SunLine to provide CNG at a reasonable price compared to diesel fuel 

cost. Over the last six months (June through October 2006), the average price of CNG was $0.98 

per gasoline gallon equivalent (GGE). This CNG cost indicates that the CNG buses have a fuel 

cost of $0.33 per mile. The fuel cell bus hydrogen cost per mile has been 76% higher, and the 

HHICE hydrogen cost per mile has been three times higher than for the CNG buses. 

 34
Maintenance Analysis 

The maintenance cost analysis in this section is only for the evaluation period (FC1 and HHICE: 

January 2006 through November 2006; CNG: July 2006 through November 2006). It is the 

intent that warranty costs not be included in the cost-per-mile calculations. More work is 

required for collecting warranty maintenance costs and ensuring that all these warranty-covered 

costs have been removed from the analysis. This will be a high priority for the final evaluation 

report for this site. 

All work orders for the study buses were collected and analyzed for this evaluation. For 

consistency, the maintenance labor rate was kept at a constant $50 per hour; this is not reflective 

of an average rate for SunLine. This section first covers total maintenance costs, then 

maintenance costs broken down by bus system. 

Total Maintenance Costs – Total maintenance costs include the price of parts and hourly labor 

rates of $50 per hour. Cost per mile is calculated as follows: 

Cost per mile = ((labor hours * 50) + parts cost) / mileage 

Table 9 shows total maintenance costs for the fuel cell, HHICE, and CNG buses. The CNG 

buses have the lowest total maintenance cost per mile of the three study bus groups. The per 

mile maintenance costs for the fuel cell and HHICE buses are 76% higher and 2.2 times higher, 

respectively, than the baseline/CNG buses. All three study bus groups were under warranty 

during the entire evaluation period. Although the HHICE bus is still under warranty, it has 

higher costs than the fuel cell bus because the SunLine mechanics do much more of the work on 

the HHICE bus than the fuel cell bus. The fuel cell bus maintenance is done almost exclusively 

by ISE and UTC Power, except for routine and non-drivetrain maintenance. 

Table 9. Total Maintenance Costs (Evaluation Period) 

Bus Mileage Parts ($) Labor 

Hours 

Cost ($) 

per Mile 

FC1 19,208 99.80 168.8 0.44 

550 HHICE 23,779 1,779.70 224.3 0.55 

563 CNG 25,105 622.07 79.8 0.18 

565 CNG 23,712 714.43 126.5 0.30 

566 CNG 15,188 693.80 76.5 0.30 

567 CNG 22,323 1,114.78 84.0 0.24 

568 CNG 22,212 791.17 90.8 0.24 

Total CNG 108,540 3,936.25 457.5 0.25 

Avg. per Bus 21,708 787.25 91.5 -- 

Maintenance Costs Broken Down by System – Table 10 shows maintenance costs by vehicle 

system and bus study group (without warranty costs included). The vehicle systems shown in 

the table include the following: 

 35
• Cab, Body, and Accessories: Includes body, glass, and paint repairs following accidents; 

cab and sheet metal repairs on seats and doors; and accessory repairs such as 

hubodometers and radios 

• Propulsion-Related Systems: Repairs for exhaust, fuel, engine, electric motors, fuel cell 

modules, propulsion control, non-lighting electrical (charging, cranking, and ignition), air 

intake, cooling, and transmission 

• Preventive Maintenance Inspections (PMI): Labor for inspections during preventive 

maintenance 

• Brakes 

• Frame, Steering, and Suspension 

• Heating, Ventilation, and Air Conditioning (HVAC) 

• Lighting 

• Air System, General 

• Axles, Wheels, and Drive Shaft 

• Tires.

The systems with the highest percentage of maintenance costs for the fuel cell bus were 

propulsion-related; HVAC; and cab, body, and accessories. For the HHICE bus, the three 

highest cost systems were propulsion-related; PMI; and cab, body, and accessories. The CNG 

buses had the same three systems as the HHICE bus, but in a slightly different ranking. 

Table 10. Breakdown of Vehicle System Maintenance Cost per Mile (Evaluation Period) 

Fuel Cell HHICE CNG 

System Cost per 

Mile ($) 

Percent of 

Total (%) 

Cost per 

Mile ($) 

Percent of 

Total (%) 

Cost per 

Mile ($) 

Percent of 

Total (%) 

Cab, Body, and 

Accessories 0.07 16 0.06 12 0.08 32 

Propulsion-Related 0.17 39 0.33 60 0.06 24 

PMI 0.05 11 0.09 16 0.08 32 

Brakes 0.01 2 0.00 0 0.00 0 

Frame, Steering, and 

Suspension 0.00 0 0.01 2 0.00 0 

HVAC 0.13 30 0.00 0 0.01 4 

Lighting 0.01 2 0.03 5 0.01 4 

Axles, Wheels, and 

Drive Shaft 0.00 0 0.00 0 0.00 0 

Tires 0.00 0 0.03 5 0.01 4 

Total 0.44 100 0.55 100 0.25 100 

The cab, body, and accessories category had similar costs/mile for each of the three study bus 

groups, although the percent of totals were significantly different. The propulsion-related 

maintenance costs were high for the HHICE and fuel cell buses compared with the CNG buses, 

with the HHICE bus having the highest cost per mile. For the PMI category, the HHICE and 

CNG buses had similar costs per mile. The fuel cell bus had significantly lower PMI than the 

other two study bus groups. This was caused by much of the PMI being done under warranty by 

the UTC Power and ISE technicians and not the SunLine mechanics. 

The only other system maintenance category of note is the HVAC system for the fuel cell bus. 

The air conditioning on the fuel cell bus has required significant maintenance attention and has 

 36
caused significant unavailability of the bus for service. The problem was with the evaporator 

and condenser motors, which were failing on a regular basis. SunLine was having difficulty 

keeping replacement motors in stock to keep the bus available for service. A redesign of the 

motors was implemented in September 2006, after the heat of the summer had passed. Although 

this issue appears to be resolved, proof of this will not be possible until next summer. 

Propulsion-Related Maintenance Costs – The propulsion-related vehicle systems include the 

exhaust, fuel, engine, electric propulsion, air intake, cooling, non-lighting electrical, and 

transmission systems. Table 11 categorizes the propulsion-related system repairs for the three 

study bus groups during the evaluation period (no warranty). Each of the three study groups of 

buses was under warranty during the entire evaluation period. Also, the fuel cell and HHICE 

buses were maintained by the UTC Power and ISE technicians when significant repairs to the 

fuel cell power system or drive system were required. In most cases, the only costs captured 

here are for support by the SunLine mechanics to the manufacturer technicians. 

• Total propulsion-related – The HHICE bus had the highest maintenance costs for these 

systems, followed by the fuel cell bus. The CNG buses had very low maintenance costs 

for these systems (as expected because the buses were new and featured fully commercial 

technology). 

• Exhaust – There were little or no costs for this system for the three study groups of 

buses. 

• Fuel – The fuel cell bus had no reported fuel system maintenance costs. The HHICE bus 

is older than the fuel cell bus and had some maintenance costs for hydrogen fuel line 

leaks. The CNG buses had some maintenance for small leaks and rerouting of fuel lines 

(shakedown issues from the new buses). 

• Powerplant and electric propulsion – The fuel cell bus maintenance reported here 

involved almost exclusively SunLine mechanics supporting UTC Power and ISE 

technicians’ work on the bus. One significant issue was the ZEBRA batteries and the 

number of problems and changeouts of the three battery packs. The HHICE bus had 

issues with injectors and the turbocharger, which were repaired under warranty with 

support from SunLine. The only other repairs were for preventive maintenance. The 

preventive maintenance for the CNG buses was almost exclusively in the powerplant 

category (and none for electric propulsion). 

• Non-lighting electrical (charging, cranking, and ignition) – The fuel cell bus had 

almost no costs in this category. The HHICE bus had significant repairs with the 

standard batteries on the bus (at least 8 changeouts and 4 roadcalls). Other maintenance 

costs included 2 sets of spark plugs and 2 sets of coils. The CNG buses mostly had 

preventive maintenance repairs in this category for spark plugs at the 18,000 preventive 

maintenance cycle for each bus. Other repairs in this category included changeout of all 

6 coil boots for one bus, one starter under warranty, and one voltage regulator under 

warranty. 

• Air intake – The fuel cell bus costs in this category were just for support by SunLine 

mechanics. The HHICE and CNG buses only had air filter changeouts in this category. 

 37
Table 11. Propulsion-Related Maintenance Costs by System (Evaluation Period) 

Maintenance System Costs Fuel Cell HHICE CNG 

Mileage 19,208 23,779 108,540

Total Propulsion-Related Systems (Roll-up) 

Parts cost ($) 22.39 1,458.76 1,991.58

Labor hours 65.0 127.3 77.5

Total cost ($) 3,272.39 7,821.26 5,866.58

Total cost ($) per mile 0.17 0.33 0.06

Exhaust System Repairs 

Parts cost ($) 0.00 0.00 0.00

Labor hours 0.0 0.0 3.0

Total cost ($) 0.00 0.00 150.00

Total cost ($) per mile 0.00 0.00 0.00

Fuel System Repairs 

Parts cost ($) 0.00 4.00 38.54

Labor hours 1.0 8.5 17.3

Total cost ($) 50.00 429.00 901.04

Total cost ($) per mile 0.00 0.02 0.01

Powerplant System Repairs 

Parts cost ($) 10.01 139.70 1,242.31

Labor hours 27.5 70.0 8.8

Total cost ($) 1,385.01 3,639.70 1,679.81

Total cost ($) per mile 0.07 0.15 0.02

Electric Propulsion System Repairs 

Parts cost ($) 0.00 0.00 0.00

Labor hours 23.5 0.8 0.0

Total cost ($) 1,175.00 37.50 0.00

Total cost ($) per mile 0.06 0.00 0.00

Non-Lighting Electrical System Repairs (General Electrical, Charging, Cranking, 

Ignition) 

Parts cost ($) 0.00 1,201.26 223.77

Labor hours 1.5 38.5 32.3

Total cost ($) 75.00 3,126.26 1,836.27

Total cost ($) per mile 0.00 0.13 0.02

Air Intake System Repairs 

Parts cost ($) 0.00 104.80 284.89

Labor hours 6.5 2.5 0.0

Total cost ($) 325.00 229.80 284.89

Total cost ($) per mile 0.02 0.01 0.00

Cooling System Repairs 

Parts cost ($) 12.38 9.00 8.75

Labor hours 5.0 7.0 15.5

Total cost ($) 262.38 359.00 783.75

Total cost ($) per mile 0.01 0.02 0.01

Transmission System Repairs 

Parts cost ($) 0.00 0.00 193.32

Labor hours 0.0 0.0 0.8

Total cost ($) 0.00 0.00 230.82

Total cost ($) per mile 0.00 0.00 0.00

 38
• Cooling – The fuel cell bus had little cost in this category. The HHICE bus had 

maintenance for problems with the low coolant sensor (replaced 3 times and caused 2 

roadcalls). The CNG buses only had shake down issues for new buses for securing 

coolant lines and alarms. 

• Transmission – Only the CNG buses had costs in this category for filters under 

preventive maintenance. 

Roadcall Analysis 

A roadcall (RC) or revenue vehicle system failure (as named in the National Transit Database) is 

defined as a failure of an in-service bus that causes the bus to be replaced on route or causes a 

significant delay in schedule. If the problem with the bus can be repaired during a layover and 

the schedule is kept, this is not considered a RC. The analysis provided here only includes RCs 

that were caused by “chargeable” failures. Chargeable RCs include systems that can physically 

disable the bus from operating on route, such as interlocks (doors and wheelchair lift), engine, 

etc. They do not include RCs for things such as radios, HVAC, or destination signs. 

Table 12 shows the RCs and miles between roadcalls (MBRC) for each study bus in two 

categories: all RCs and propulsion-related-only RCs. The CNG buses have had very few 

roadcalls. The fuel cell and HHICE buses have had several roadcalls and low vehicle usage, 

which is indicative of the prototype nature of these two buses. Compared to the fuel cell bus, the 

HHICE bus has slightly higher MBRC rates for both the all-roadcalls category and the 

propulsion-only category. 

Table 12. Roadcalls and MBRC (Evaluation Period) 

Bus Mileage All 

Roadcalls All MBRC Propulsion Roadcalls 

Propulsion 

MBRC 

FC1 19,208 22 873 17 1,130 

550 HHICE 23,779 10 2,378 8 2,972 

563 CNG 25,105 3 8,368 1 25,105 

565 CNG 23,712 0 0 

566 CNG 15,188 1 15,188 0 

567 CNG 22,323 2 11,162 0 

568 CNG 22,212 0 0 

Total CNG 108,540 6 18,090 1 108,540 

 39
What’s Next for This Demonstration? 

This report covers SunLine operation of the fuel cell, HHICE, and CNG buses through 

November 2006. The next evaluation report for this site will include at least 12 months of 

operation for the CNG buses, which will require that the evaluation period run through at least 

June 2007. The next evaluation report is planned for release around November 2007. 

As described above, SunLine is also a recipient of a grant from the FTA for its National Fuel 

Cell Bus Program. This grant includes $2.8 million to support the development of a new fuel 

cell bus design and demonstration at SunLine. The partners in this effort are New Flyer Bus, ISE 

Corp., and UTC Power. SunLine was also listed as a partner for accelerated testing of the Van 

Hool fuel cell buses with AC Transit. FTA, DOE, and NREL plan to work together to continue 

evaluations of the NFCBP and other hydrogen and fuel cell-related transit operations. 

 40
Contacts 

DOE 

1000 Independence Ave., SW 

Washington, DC 20585 

Sigmund Gronich 

Technology Validation Manager 

Office of Hydrogen, Fuel Cells, and 

Infrastructure Technologies 

Phone: 202-586-1623 

E-mail: sigmund.gronich@ee.doe.gov 

NREL 

1617 Cole Boulevard 

Golden, CO 80401 

Leslie Eudy 

Senior Project Leader 

Phone: 303-275-4412 

E-mail: leslie_eudy@nrel.gov 

SunLine 

32-505 Harry Oliver Trail 

Thousand Palms, CA 92276 

Tommy Edwards 

Director of Maintenance 

Phone: 760-343-3456 

E-mail: tedwards@sunline.org 

UTC Power 

195 Governor’s Highway 

South Windsor, CT 06074 

Michael Tosca 

Senior Product Manager 

Phone: 860-727-7324 

E-mail: michael.tosca@utcpower.com

Matthew Riley 

Systems Engineer 

Phone: 860-727-2864 

E-mail: Matthew.Riley@utcpower.com 

ISE Corporation 

12302 Kerran Street 

Poway, CA 92064 

Paul Scott 

Chief Scientific Officer 

Phone: 858-413-1742 

E-mail: pscott@isecorp.com 

Tavin Tyler 

Director of Prototype Programs 

Phone: 858-413-1745 

E-mail: ttyler@isecorp.com 

Ford Motor Company 

Ford Scientific Research Laboratories 

2101 Village Road 

Dearborn, MI 48121 

Bob Natkin 

Technical & Group Leader for H2 IC 

Engine Applications Powertrain Research 

Dept. 

Phone: 313-322-1725 

E-mail: rnatkin@ford.com

New Flyer 

Winnipeg, Manitoba 

Canada R2J 4B9 

Paul Zanetel 

Chief Technical Advisor 

Phone: 204-982-8180 

E-mail: paul_zanetel@newflyer.com

HyRadix 

175 West Oakton Street 

Des Plaines, IL 60018 

Terry Schuster 

Director of Sales 

Phone: 630-416-7425 

E-mail: terry.schuster@hyradix.com 

 41
Van Hool Battelle 

Bernard Van Hoolstraat 58 505 King Avenue 

B-2500 Lier Koningshooikt Columbus, OH 43201 

Belgium 

Kevin Chandler 

Paul Jenné Program Manager 

Automotive Relations Phone: 614-424-5127 

Phone : +32 (3) 420 22 10 E-mail: chandlek@battelle.org 

E-mail: paul.jenne@vanhool.be

 42
Acronyms and Abbreviations

APTA American Public Transportation Association 

ASME American Society of Mechanical Engineers 

CARB California Air Resources Board 

CEO Chief executive officer 

CFO Chief financial officer 

CNG Compressed natural gas 

CSA Cell stack assembly 

CWI Cummins Westport Inc. 

DGE Diesel gallon equivalent 

DOE U.S. Department of Energy 

FCB Fuel cell bus 

ft Feet 

FTA Federal Transit Administration 

GGE Gasoline gallon equivalent 

HFCIT Hydrogen, Fuel Cells, and Infrastructure Technology 

HHICE Hydrogen Hybrid Internal Combustion Engine 

hp Horsepower 

HVAC Heating, ventilation, and air conditioning 

ICE Internal combustion engine 

in Inches 

JPA Joint powers authority 

kg Kilogram 

kW Kilowatts 

lb Pounds 

LFL Lower flammability limit 

MBRC Miles between roadcalls 

mph Miles per hour 

NFCBP National Fuel Cell Bus Program 

Nm Newton meters 

NOx Oxides of nitrogen 

NREL National Renewable Energy Laboratory 

PMI Preventive maintenance inspection 

PSA Pressure swing adsorption 

psi Pounds per square inch 

RC Roadcall 

rpm Revolutions per minute 

SCAQMD South Coast Air Quality Management District 

SOC State of charge 

ZEBus Zero emission bus 

 43
References and Related Reports 

Chandler, K., Eudy, L., 2006, Santa Clara Valley Transportation Authority and San Mateo 

County Transit District, Fuel Cell Transit Buses: Evaluation Results, National Renewable 

Energy Laboratory, Golden, CO, NREL/TP-560-40615 

NREL, 2006, SunLine Tests HHICE Bus in Desert Climate, National Renewable Energy 

Laboratory, Golden, CO, DOE/GO-102006-2333 

NREL, 2006, AC Transit Demos Three Prototype Fuel Cell Buses, National Renewable Energy 

Laboratory, Golden, CO, DOE/GO-102006-2286 

NREL, 2006, SunLine Expands Horizons with Fuel Cell Bus Demo, National Renewable Energy 

Laboratory, Golden, CO, DOE/GO-102006-2287 

Chandler, K., 2006, Ten Years of Compressed Natural Gas (CNG) Operations at SunLine 

Transit Agency, National Renewable Energy Laboratory, Golden, CO, NREL/SR-540-39180 

NREL, 2005, VTA, SamTrans Look into Future with Bus Demo, National Renewable Energy 

Laboratory, Golden, CO, DOE/GO-102005-2147 

NREL, 2005, Draft Fuel Cell Transit Bus Evaluation Plan, National Renewable Energy 

Laboratory, Golden, CO 

EvoBus GmbH, 2004, Clean Urban Transport for Europe (CUTE), A Fuel Cell Bus Project in 

Nine European Cities, EvoBus, Ulm, Germany 

Chandler, K., Eudy, L., 2003, ThunderPower Bus Evaluation at SunLine Transit Agency, 

National Renewable Energy Laboratory, Golden, CO, DOE/GO-102003-1786 

NREL, 2003, SunLine Test Drives Hydrogen Bus, National Renewable Energy Laboratory, 

Golden, CO, DOE/GO-102003-1768 

NREL, 2002, General Evaluation Plan, Fleet Test & Evaluation Projects, National Renewable 

Energy Laboratory, Golden, CO, NREL/BR-540-32392 

College of the Desert, 2001, Hydrogen Fuel Cell Engines and Related Technologies (Course 

Materials, Modules 1-11), College of the Desert, Palm Desert, CA 

Reports from DOE/NREL evaluations can be downloaded via the following Web sites: 

Hydrogen and fuel cell related: www.nrel.gov/hydrogen/proj_fc_bus_eval.html

Hybrid and other technologies: www.nrel.gov/vehiclesandfuels/fleettest/publications_bus.html 

 44
Appendix: Fleet Summary Statistics 

Fleet Summary Statistics: SunLine Transit Agency

FCB, HHICE, and CNG Study Groups 

Fleet Operations and Economics

Fuel Cell HHICE CNG 

Number of Vehicles 1 1 5

Period Used for Fuel and Oil Op Analysis 1/06-11/06 1/06-11/06 7/06-11/06

Total Number of Months in Period 11 11 5

Fuel and Oil Analysis Base Fleet Mileage 19,208 23,661 108,540

Period Used for Maintenance Op Analysis 1/06-11/06 1/06-11/06 7/06/11/06

Total Number of Months in Period 11 11 5

Maintenance Analysis Base Fleet Mileage 19,208 23,779 108,540

Average Monthly Mileage per Vehicle 1,746 2,162 4,342

Availability 61% 80% 86%

Fleet Fuel Usage in CNG GGE/H2 kg 2,622 5,514 36,550

Roadcalls 22 10 6

RCs MBRC 873 2,378 18,090

Propulsion Roadcalls 17 8 1

Propulsion MBRC 1,130 2,972 108,540

 

Fleet Miles/kg Hydrogen or CNG GGE 7.33 4.29 2.97

(1.13 kg H2/gal Diesel Fuel) 

Representative Fleet MPG (energy equiv.) 8.28 4.85 3.32

 

Hydrogen Cost per kg 4.26 4.26 

Cost per Gasoline Gallon Equivalent 0.98

Fuel Cost per Mile 0.58 0.99 0.33

 

Total Scheduled Repair Cost per Mile 0.08 0.10 0.11

Total Unscheduled Repair Cost per Mile 0.37 0.45 0.13

Total Maintenance Cost per Mile 0.44 0.55 0.25

 

Total Operating Cost per Mile 1.03 1.54 0.58

Maintenance Costs

 Fuel Cell HHICE CNG 

Fleet Mileage 19,208 23,779 108,540

 

Total Parts Cost 99.80 1,779.20 3,936.25

Total Labor Hours 168.8 224.3 457.5

Average Labor Cost (@ $50.00 per hour) 8,437.50 11,212.50 22,875.00

 

Total Maintenance Cost 8,537.30 12,991.70 26,811.25

Total Maintenance Cost per Bus 8,537.30 12,991.70 5,362.25

Total Maintenance Cost per Mile 0.44 0.55 0.25

 45
Breakdown of Maintenance Costs by Vehicle System

Fuel Cell HHICE CNG 

Fleet Mileage 19,208 23,779 108,540

 

Total Propulsion-Related Systems (ATA VMRS 27, 30, 31, 32, 33, 41, 42, 43, 44, 45, 65) 

Parts Cost 22.39 1,458.76 1,991.58

Labor Hours 65.0 127.3 77.5

Average Labor Cost 3,250.00 6,362.50 3,875.00

Total Cost (for system) 3,272.39 7,821.26 5,866.58

Total Cost (for system) per Bus 3,272.39 7,821.26 1,173.32

Total Cost (for system) per Mile 0.17 0.33 0.06

 

Exhaust System Repairs (ATA VMRS 43) 

Parts Cost 0.00 0.00 0.00

Labor Hours 0.0 0.0 3.0

Average Labor Cost 0.00 0.00 150.00

Total Cost (for system) 0.00 0.00 150.00

Total Cost (for system) per Bus 0.00 0.00 30.00

Total Cost (for system) per Mile 0.00 0.00 0.00

 

Fuel System Repairs (ATA VMRS 44) 

Parts Cost 0.00 4.00 38.54

Labor Hours 1.0 8.5 17.3

Average Labor Cost 50.00 425.00 862.50

Total Cost (for system) 50.00 429.00 901.04

Total Cost (for system) per Bus 50.00 429.00 180.21

Total Cost (for system) per Mile 0.00 0.02 0.01

 

Powerplant (Engine) Repairs (ATA VMRS 45) 

Parts Cost 10.01 139.70 1,242.31

Labor Hours 27.5 70.0 8.8

Average Labor Cost 1,375.00 3,500.00 437.50

Total Cost (for system) 1,385.01 3,639.70 1,679.81

Total Cost (for system) per Bus 1,385.01 3,639.70 335.96

Total Cost (for system) per Mile 0.07 0.15 0.02

 

Electric Propulsion Repairs (ATA VMRS 46) 

Parts Cost 0.00 0.00 0.00

Labor Hours 23.5 0.8 0.0

Average Labor Cost 1,175.00 37.50 0.00

Total Cost (for system) 1,175.00 37.50 0.00

Total Cost (for system) per Bus 1,175.00 37.50 0.00

Total Cost (for system) per Mile 0.06 0.00 0.00

 

 46
Breakdown of Maintenance Costs by Vehicle System (continued)

 Fuel Cell HHICE CNG 

Electrical System Repairs (ATA VMRS 30-Electrical General, 31-Charging, 32-Cranking, 33-

Ignition)

Parts Cost 0.00 1,201.26 223.77

Labor Hours 1.5 38.5 32.3

Average Labor Cost 75.00 1,925.00 1,612.50

Total Cost (for system) 75.00 3,126.26 1,836.27

Total Cost (for system) per Bus 75.00 3,126.26 367.25

Total Cost (for system) per Mile 0.00 0.13 0.02

 

Air Intake System Repairs (ATA VMRS 41) 

Parts Cost 0.00 104.80 284.89

Labor Hours 6.5 2.5 0.0

Average Labor Cost 325.00 125.00 0.00

Total Cost (for system) 325.00 229.80 284.89

Total Cost (for system) per Bus 325.00 229.80 56.98

Total Cost (for system) per Mile 0.02 0.01 0.00

 

Cooling System Repairs (ATA VMRS 42) 

Parts Cost 12.38 9.00 8.75

Labor Hours 5.0 7.0 15.5

Average Labor Cost 250.00 350.00 775.00

Total Cost (for system) 262.38 359.00 783.75

Total Cost (for system) per Bus 262.38 359.00 156.75

Total Cost (for system) per Mile 0.01 0.02 0.01

 

General Air System Repairs (ATA VMRS 10) 

Parts Cost 0.00 0.00 0.00

Labor Hours 0.0 0.0 2.0

Average Labor Cost 0.00 0.00 100.00

Total Cost (for system) 0.00 0.00 100.00

Total Cost (for system) per Bus 0.00 0.00 20.00

Total Cost (for system) per Mile 0.00 0.00 0.00

 

Brake System Repairs (ATA VMRS 13) 

Parts Cost 0.00 0.00 1.82

Labor Hours 5.5 1.5 2.5

Average Labor Cost 275.00 75.00 125.00

Total Cost (for system) 275.00 75.00 126.82

Total Cost (for system) per Bus 275.00 75.00 25.36

Total Cost (for system) per Mile 0.01 0.00 0.00

 

 47
Breakdown of Maintenance Costs by Vehicle System (continued)

 Fuel Cell HHICE CNG 

Transmission Repairs (ATA VMRS 27) 

Parts Cost 0.00 0.00 193.32

Labor Hours 0.0 0.0 0.8

Average Labor Cost 0.00 0.00 37.50

Total Cost (for system) 0.00 0.00 230.82

Total Cost (for system) per Bus 0.00 0.00 46.16

Total Cost (for system) per Mile 0.00 0.00 0.00

Inspections Only – No Parts Replacements (101) 

Parts Cost 0.00 0.00 0.00

Labor Hours 21.0 40.5 177.0

Average Labor Cost 1,050.00 2,025.00 8,850.00

Total Cost (for system) 1,050.00 2,025.00 8,850.00

Total Cost (for system) per Bus 1,151.00 2,025.00 1,770.00

Total Cost (for system) per Mile 0.05 0.09 0.08

 

HVAC System Repairs (ATA VMRS 01) 

Parts Cost 0.00 0.00 220.22

Labor Hours 51.3 1.5 18.0

Average Labor Cost 2,562.50 75.00 900.00

Total Cost (for system) 2,562.50 75.00 1,120.22

Total Cost (for system) per Bus 2,562.50 75.00 224.04

Total Cost (for system) per Mile 0.13 0.00 0.01

 

Cab, Body, and Accessories Systems Repairs 

(ATA VMRS 02-Cab and Sheet Metal, 50-Accessories, 71-Body) 

Parts Cost 65.91 123.46 1,598.68

Labor Hours 24.0 27.3 149.0

Average Labor Cost 1,200.00 1,362.50 7,450.00

Total Cost (for system) 1,265.91 1,485.96 9,048.68

Total Cost (for system) per Bus 1,265.91 1,485.96 1,809.74

Total Cost (for system) per Mile 0.07 0.06 0.08

 

Lighting System Repairs (ATA VMRS 34) 

Parts Cost 11.50 196.98 56.65

Labor Hours 1.5 9.3 11.8

Average Labor Cost 75.00 462.50 587.50

Total Cost (for system) 86.50 659.48 644.15

Total Cost (for system) per Bus 86.50 659.48 128.83

Total Cost (for system) per Mile 0.00 0.03 0.01

 

 48
Breakdown of Maintenance Costs by Vehicle System (continued)

 Fuel Cell HHICE CNG 

Frame, Steering, and Suspension Repairs (ATA VMRS 14-Frame, 15-Steering, 16-Suspension) 

Parts Cost 0.00 0.00 67.30

Labor Hours 0.5 3.5 3.3

Average Labor Cost 25.00 175.00 162.50

Total Cost (for system) 25.00 175.00 229.80

Total Cost (for system) per Bus 25.00 175.00 45.96

Total Cost (for system) per Mile 0.00 0.01 0.00

 

Axle, Wheel, and Drive Shaft Repairs (ATA VMRS 11-Front Axle, 18-Wheels, 22-Rear Axle, 24-

Drive Shaft) 

Parts Cost 0.00 0.00 0.00

Labor Hours 0.0 1.5 0.0

Average Labor Cost 0.00 75.00 0.00

Total Cost (for system) 0.00 75.00 0.00

Total Cost (for system) per Bus 0.00 75.00 0.00

Total Cost (for system) per Mile 0.00 0.00 0.00

 

Tire Repairs (ATA VMRS 17)

Parts Cost 0.00 0.00 0.00

Labor Hours 0.0 12.0 16.5

Average Labor Cost 0.00 600.00 825.00

Total Cost (for system) 0.00 600.00 825.00

Total Cost (for system) per Bus 0.00 600.00 165.00

Total Cost (for system) per Mile 0.00 0.03 0.01

 49
Notes

1. To compare the hydrogen fuel dispensed and fuel economy to diesel, the hydrogen dispensed 

was also converted into diesel energy equivalent gallons. The general energy conversions are as 

follows, actual energy content will vary by location: 

Lower heating value (LHV) for hydrogen = 51,532 Btu/lb 

LHV for diesel = 128,400 Btu/lb 

1 kg = 2.205 * lb 

51,532 Btu/lb * 2.205 lb/kg = 113,628 Btu/kg 

Diesel/hydrogen = 128,400 Btu/gallon / 113,628 Btu/kg = 1.13 kg/diesel gallon 

The gasoline LHV or GGE is 115,000 Btu/gal, which is approximately 1% higher than 

113,628 Btu/kg for hydrogen; these have been called equivalent for this report. 

Gasoline/Diesel = 115,000 Btu/gallon / 128,400 Btu/gallon = 0.896 

2. The propulsion-related systems were chosen to include only those vehicle systems that could be 

directly impacted by the selection of a fuel/advanced technology. 

3. ATA VMRS coding is based on parts that were replaced. If there was no part replaced in a given 

repair, then the code was chosen by the system being worked on. 

4. In general, inspections (with no part replacements) were only included in the overall totals (not by 

system). 101 was created to track labor costs for PM inspections. 

5. ATA VMRS 02-Cab and Sheet Metal represents seats, doors, etc.; ATA VMRS 50-Accessories 

represents things like fire extinguishers, test kits, etc.; ATA VMRS 71-Body represent mostly 

windows and windshields. 

6. Average labor cost is assumed to be $50 per hour. 

7. Warranty costs are not included. 

 50
Appendix: Fleet Summary Statistics – SI Units 

Fleet Summary Statistics: SunLine Transit Agency

FCB, HHICE, and CNG Study Groups 

Fleet Operations and Economics

Fuel Cell HHICE CNG 

Number of Vehicles 1 1 5

Period Used for Fuel and Oil Op Analysis 1/06-11/06 1/06-11/06 7/06-11/06

Total Number of Months in Period 11 11 5

Fuel and Oil Analysis Base Fleet Kilometers 30,911 38,078 174,673

Period Used for Maintenance Op Analysis 1/06-11/06 1/06-11/06 7/06-11/06

Total Number of Months in Period 11 11 5

Maintenance Analysis Base Fleet Kilometers 30,911 38,268 174,673

Average Monthly Kilometers per Vehicle 2,810 3,479 6,988

Availability 61% 80% 86%

Fleet Fuel Usage in Gasoline L/H2 kg 2,622 5,514 138,342

Roadcalls 22 10 6

Kilometers between Roadcalls (KBRC) 1,405 3,827 29,112

Propulsion Roadcalls 17 8 1

Propulsion KBRC 1,818 4,784 174,673

 

Fleet kg Hydrogen/100 km 8.48 14.48 

Representative Fleet MPG (L/100 km) 32.11 54.81 79.20

 

Hydrogen Cost per kg 4.26 4.26 

CNG Cost per Liter (based on GGE) 0.26

Fuel Cost per Kilometer 0.36 0.62 0.21

 

Total Scheduled Repair Cost per Kilometer 0.05 0.06 0.07

Total Unscheduled Repair Cost per Kilometer 0.23 0.28 0.08

Total Maintenance Cost per Kilometer 0.28 0.34 0.15

 

Total Operating Cost per Kilometer 0.64 0.96 0.36

Maintenance Costs

 Fuel Cell HHICE CNG 

Fleet Kilometers 30,911 38,078 174,673

 

Total Parts Cost 99.80 1,779.20 3,936.25

Total Labor Hours 168.8 224.3 457.5

Average Labor Cost (@ $50.00 per hour) 8,437.50 11,212.50 22,875.00

 

Total Maintenance Cost 8,537.30 12,991.70 26,811.25

Total Maintenance Cost per Bus 8,537.30 12,991.70 5,362.55

Total Maintenance Cost per Kilometer 0.28 0.34 0.15

 51
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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

February 2007 

2. REPORT TYPE

Technical Report 

3. DATES COVERED (From - To)

 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

4. TITLE AND SUBTITLE

SunLine Transit Agency, Hydrogen-Powered Buses: 

Preliminary Evaluation Results 

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

NREL/TP-560-41001 

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H270.8200 

6. AUTHOR(S)

K. Chandler, Battele 

L. Eudy, NREL 

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National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

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14. ABSTRACT (Maximum 200 Words)

This paper provides preliminary results from an evaluation by DOE's National Renewable Energy Laboratory of 

hydrogen-powered transit buses at SunLine Transit Agency. 

15. SUBJECT TERMS

hydrogen-powered transit buses; hydrogen bus; technology validation; SunLine Transit Agency; hydrogen fuel cell 

bus evaluation 

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