For railway traction power, a hydrogen fuelcell powerplant provides the advantages of its competitors, namely electric and diesel-electric power, while avoiding their disadvantages. It possesses the environmental benefits at the vehicle of an electric locomotive but the lower infrastructure cost of a diesel. Electric (catenary) locomotives – when viewed as only one component of a distributed machine that includes an electricity-generation plant, transformers, and transmission lines – are the least energy-efficient and most costly of conventional locomotive types. Elimination of high catenary-wire infrastructure costs by fuelcell locomotives is the key to economic viability of zero-emission, low-noise electric trains in low population density regions. Diesel-electric locomotives, while collectively worse as sources of air pollution than an equal number of electric locomotives driven by a coal-fired powerplant, are more energy efficient and have a less expensive energy infrastructure. The natural fuel for a fuelcell is hydrogen, which is manufactured like the electricity of the electric locomotive, and therefore hydrogen may be cyclically and indefinitely produced from water. If its hydrogen fuel is produced from renewable or nuclear primary energy, operation of the locomotive will not depend on imported oil and will not emit carbon in the energy cycle. For the purpose of commercialization, an advantage of the railway application is that the fueling infrastructure constitutes a one-dimensional space, vis-à-vis the two-dimensional space of road vehicles.
Fuelcell locomotives can help resolve the joined international issues of urban air quality and energy security affecting the rail industry and transportation sector as a whole. The issues are related by the fact that about 97% of the energy for the transport sector (in the US) is based on oil, and more than 60% is imported. Because its primary energy is based largely on combustion of fossil fuels, the transportation sector is one of the largest sources of air pollution. Beyond local air quality, a consensus has been reached that the burning of fossil fuels is a significant factor in global climate change. Energy security is low because world oil reserves are diminishing, demand is increasing, and political instability threatens supply disruptions.
Furthermore, a need exists for large vehicles that serve, in addition to conveyance, as mobile backup power sources (“vehicle-to-grid”) for critical infrastructure. Vehicle-to-grid applications include military bases and civilian disaster-relief operations.
A North American public-private project partnership comprised of Vehicle Projects Inc, BNSF Railway Company, and the U.S. Army Corps of Engineers (through the Engineer Research and Development Center Construction Engineering Research Laboratory, ERDC-CERL) has developed a prototype fuelcell-powered shunt (switch) locomotive (see Fig. 1) for urban rail applications. This prototype is intended to lead to commercial locomotives that will (1) reduce air and noise pollution in urban railyards, including seaports, (2) increase energy security of the rail transport system by using a fuel independent of imported oil, (3) reduce atmospheric greenhouse-gas emissions, and (4) serve as a mobile backup power source (“vehicle-to-grid” or “power-to-grid”) for critical infrastructure on military bases and for civilian disaster relief efforts. The railyard demonstrations will be executed at the BNSF Commerce and Hobart yards in the Los Angeles, California, metro area.
This document focuses on the locomotive’s potential to reduce chemical (primarily diesel particulates and nitrogen oxides) and acoustic noise emissions in the Los Angeles Basin.
This fast-paced project commenced in May 2006, and the vehicle has now completed exhaustive impact testing at the US Department of Transportation railway proving grounds operated by TTCI in Pueblo, Colorado, and has arrived in Los Angeles (LA) for testing under working conditions.
At 130 tonne (287 thousand lb), continuous net power of approximately 240 kW from its PEM (proton exchange membrane) fuelcell powerplant, and transient power well in excess of 1 MW, the hybrid locomotive is the heaviest and most powerful fuelcell land vehicle yet. Its prime mover is a modular design based on Ballard P5TM stacks. For energy storage, fourteen lightweight carbon-fiber composite tanks are located above the traction battery. Fig. 2 shows the fuelcell prime mover installed in the locomotive.
Based on engineering design by Vehicle Projects Inc, the BNSF Topeka System Maintenance Terminal in Topeka, Kansas, fabricated most of the fuelcell powerplant which replaced the diesel engine-alternator and installed the prime mover in the vehicle. Subsystem and complete powerplant testing was executed by Vehicle Projects Inc. Because the combined weights of fuelcell powerplant and carbon-fiber hydrogen storage system are substantially lighter than the diesel engine-alternator and diesel fuel tank they replace, a steel-plate ballast of approximately 9000 kg is placed in the undercarriage bay. A locomotive has a fixed operating weight in order to maintain wheel adhesion to the rails.
Previous papers have discussed the theory [2-4] and engineering design [1, 5-6] of the hybrid locomotive. While the BNSF locomotive is the largest and possibly the most sophisticated fuelcell land vehicle to-date, it is not the first fuelcell locomotive. The first fuelcell-powered locomotive was an underground mine locomotive successfully completed and demonstrated in a working gold mine by Vehicle Projects Inc in 2002 [7, 8].
Locomotive Fuelcell Power
The rational starting point for engineering design of a fuelcell-hybrid vehicle is the duty cycle . Figure 3 shows a typical duty cycle – that is, the function P(t), where P is vehicle power and t is time – recorded from an in-service yard-switching locomotive. The vehicle’s required mean power, maximum power, power response time, and power duration may be calculated from function P; its energy storage requirements are calculated from the integral of P. As shown, peak power commonly reaches 600-1000 kW for durations of no more than several minutes – usually corresponding to acceleration of train cars or uphill movement. However, between the peaks, the power requirements are minimal, as when coasting a load, or zero when idling between move operations. The idle time, varying from minutes to hours between operations, usually accounts for 50-90% of the overall operation schedule. Our analysis of multiple duty-cycle data sets from various railyards shows that the short duration of peak power and long periods of idle time result in mean power usage in the range of only 40-100 kW. The sharp peaks, low mean power, and long idle intervals of the duty cycle are ideal for a hybrid powertrain [4, 9].
For a hybrid vehicle to be self-sustaining, the prime mover, a hydrogen PEM fuelcell in this case, must provide continuously at least the mean power of the duty cycle. The auxiliary energy storage device, lead acid batteries in this hybrid, must store sufficient energy to provide power in excess of the continuous power rating of the fuelcell and must do so continuously under operation of the duty cycle. This energy must be available while not exceeding a rather shallow depth of discharge, which significantly increases the size of the battery. Allowable depth of discharge is a function of acceptable battery cycle life and recharge rate. With lead-acid batteries, depth of discharge is limited to approximately 80% of full capacity. Because the battery capacity of this vehicle is based on the 200 kW prime mover of the Railpower diesel-hybrid locomotive, it will easily provide the storage required for our 240 kW fuelcell prime mover. The Railpower lead-acid traction battery, in parallel with our fuelcell prime mover, allows transient power well in excess of 1 MW. For the power-to-grid application, the hybrid locomotive can provide only 240 kW of net power on a continuous basis but can provide power surges in excess of 1 MW.
The fuelcell powerplant consists of three primary subsystems; fuelcell stack modules, air delivery, and cooling. At the heart of the power module are two Ballard Power Systems P5 TM fuelcell stack modules. The fuelcell stack modules contain Ballard Mk902 stacks; each rated at 150 kW gross power at 624 V, for a total of 300 kW gross power at 624 V. Each fuelcell stack module includes the auxiliary components for air and hydrogen humidification, water recovery, hydrogen recirculation, and hydrogen purge. For the fuelcell stack modules to produce power, they require both oxygen (cathode) and hydrogen (anode) reactants. The systems that provide these reactants as well as support operation of the stack modules are referred to as the balance of plant (BOP). The air delivery system provides air at a specified mass flow and pressure. Hydrogen is supplied to the stack modules at nominally 12 bara and is pressure-regulated and recirculated inside the stack module. The cooling system rejects waste heat from the fuelcell stacks as well as auxiliary motors and electronics. The electrical distribution and control systems regulate power output, control various electrical devices, and monitor system parameters for faults.
The largest of the fuelcell system modules are the two hydrogen storage modules. Each module consists of seven carbon-fiber composite cylinders that collectively store approximately 35 kg (70 kg for the vehicle as a whole) of compressed hydrogen at 350 bar (5,100 psi). Given the physical space required for the cylinders, the only packaging options were to mount the hydrogen modules (1) under the chassis or (2) above the existing traction battery. A thorough safety analysis highlighted two factors that led to packaging of the hydrogen system above the battery. First, because of the buoyancy of hydrogen, storing hydrogen below void volumes in the locomotive platform, battery rack, and rear hood could lead to confinement of leaked hydrogen and increase the possibility of detonation. In contrast, roof-line storage allows for harmless upward dissipation of hydrogen in the event of a leak. Second, locating the hydrogen tanks at the roofline minimizes the likelihood of damage from common events such as derailment, track debris, and impact from yard traffic such as fueling trucks. Because of the relatively light weight of the hydrogen storage tanks (empty, 95 kg each), the roof location has minimal effect on vehicle center of gravity. Indeed, after conversion to hydrogen-fuelcell power, a ballast of approximately 9000 kg was placed in the undercarriage to bring the locomotive weight to its specified value of 130 t.
Extensive impact testing was performed to validate shock isolation design. The new equipment isolation systems were designed with low natural frequencies, in the range of 3-7 Hz. This minimizes the potential of resonance with on-board equipment and track input frequencies. Relatively “soft” mounts provide dynamic deflections up to 25 mm which enables maximum energy dissipation.
Impact tests up to 5.1 mph were performed repeatedly to measure shock loads at critical equipment, as well as validate robustness of the system hardware and connections when experiencing dynamic motion. The maximum allowable acceleration in longitudinal, lateral, and vertical directions for the fuelcell hardware is 3 G. This 3 G maximum applies only at or below the system natural frequency. At the maximum impact speed of 5.1 mph into a braked consist weighing approximately 364 t, the maximum measured acceleration of any of the isolated fuelcell equipment was 2.5 G, filtered at 10 Hz. The corresponding structures that were mounted to the locomotive frame exceeded 7 G, filtered at 30 Hz. As expected, maximum accelerations were dominant in the longitudinal direction. The actual measured coupler force was 270 t, slightly greater than 2 G at the coupler input.
The operating time of the fuelcell-hybrid switcher between fueling operations depends on the duty cycle. Under the most demanding duty cycles, one could expect an operating interval as short as one day, i.e., refueling on a daily basis; in less demanding yards, the interval may be 3-5 days. A major factor in the operating interval is the amount of idle time in the duty cycle. Refueling time from a 160 bar tube trailer, using a hydrogen pump, should be between 10 and 45 minutes and depends largely on the throughput of the high-pressure hydrogen pump. Because of the long idle periods in the shunt locomotive duty cycle, we have used a relatively small pump and the refueling time is around 45 minutes.
Emissions and the Los Angeles Basin
Population of the Los Angeles metro area is 13 million, and the city measures about 130 km from east to west and 60 km north to south. Because of the low population density, and consequent reliance on the automobile for transportation, and location in a basin partly surrounded by mountains, it has historically had air-quality problems. It is also the site of the adjacent ports of Long Beach and Los Angeles, the largest seaports in the United States, which contribute to air pollution from trucks, trains, and ships. In part, because the economy of the State of California exceeds that of many nations, the state has substantial national influence and has taken a leadership role in setting US Government air-quality regulations. Planned regulations in California are far more stringent than federal air-quality regulations; for example, California intends to regulate carbon dioxide as an air pollutant, whereas the federal government has resisted such a classification. The State of Massachusetts sued the US Government over the issue and won in a 2007 US Supreme Court ruling, and accordingly the US Environmental Protection Agency (EPA) has in April 2009 declared carbon dioxide to be a harmful air pollutant.
The driving force of the fuelcell-hybrid shunt locomotive project is to demonstrate that fuelcell locomotives are practical solutions to reducing chemical and noise emissions in the LA Basin. Shunt locomotives, which assemble and disassemble trains in railyards, account for about five percent of all rail emissions, but they have a disproportionate impact on air quality and health risks in the communities surrounding large urban railyards. The California Air Resource Board’s (CARB) 2004 assessment of diesel particulate matter (PM) risk levels near the Roseville, California railyard revealed localized risks in excess of 500 potential cancer cases per million people exposed and that over 155 thousand people living in the vicinity of the railyard faced an elevated cancer risk due to rail operations . In contrast, line-haul locomotives, which travel throughout California, emit over 95 percent of rail emissions but distribute their emissions over a much larger area.
In March 2008, although not yet addressing carbon-dioxide emissions, the US EPA finalized a three-part national program that will reduce emissions from diesel locomotives of all types – line-haul freight, shunt, and passenger rail . The standards for locomotives are divided into Tier Groups based on their date of original manufacture and apply to rebuilt as well as new locomotives. The rule will reduce PM emissions by as much as 90 percent and nitrogen oxide (NOx) emissions by as much as 80 percent when fully implemented. The EPA projects that by 2030, the program will reduce annual emissions of PM and NOx by 27 thousand tons and 800 thousand tons, respectively. EPA projects that these reductions will annually prevent up to 1,100 PM-related premature deaths, 280 ozone-related premature deaths, 120 thousand lost work days, 120 thousand school-day absences, and 1.1 million minor restricted-activity days. The annual monetized health benefits of this rule in 2030, or conversely the annual social cost of not implementing the program, will range from $9.2 billion to $11 billion.
Diesel engines may be able to meet the EPA standards by employing after-treatment technologies such as high-temperature or catalytic exhaust filters for PM emissions and urea injection, followed by ammonia scrubbing, for NOx emissions. However, these technologies increase capital cost, lower reliability, and lower availability due to their complexity or nature of operation. The State of California’s program is more stringent and includes regulation of green-house gases (GHGs), and accordingly its savings in social costs of diesel-engine use is much higher than the EPA program. Because California’s standards include regulation of GHGs, they could spell the demise of the diesel engine in low-attainment areas such as the LA Basin. Diesel-powered trains conceivably could be stopped at the edge of the metro area, and a non-diesel locomotive – for example, battery-electric, fuelcell, or catenary-electric locomotive – would pull the train through the city. If (1) the residual social costs of diesel locomotives (with after-treatment), (2) the higher costs and lower reliability of diesels with after-treatment, and (3) the high infrastructure cost (estimated at $6 million/km in the city) for catenary-electric locomotives are considered, we hypothesize that fuelcell power is cost competitive with other urban-rail technologies.
California was chosen for this demonstration, in part, because of available emissions data from studies initiated by CARB to quantify the emissions impact from rail. In the demonstration, we will compare existing emissions data from CARB and projected improvements to air quality through implementation of fuelcell-powered rail transportation. Data collected during the demonstration will include acoustic noise data during standard work operations in the railyards. We have already measured the locomotive’s powerplant noise during testing, without any noise absorption facilities in place, and it lies in the range of 70-80 db, depending on where the measurement is taken on the vehicle. The locomotive powerplant is virtually silent in the cab, and the main noise is track noise.
It is apparent – through increasing regulation, public demand for cleaner transportation, concerns over national energy security, energy independence, and global environment and health concerns – that fuelcell rail technology has a potentially significant role in the future of the rail industry. The “real-world” operational data collected during the demonstration in the LA Basin will be invaluable in the development of future fuelcell hybrid locomotives. It will assist in modeling their performance in order to optimize their hybridization and maximize fuel economy. In addition, this data will be useful in modeling subsequent fuelcell powerplants for use in line haul and commuter locomotives.
The fuelcell-hybrid shunt locomotive for operation in the LA metro area combines the environmental advantages of an electric locomotive with the lower infrastructure costs of a diesel-electric locomotive. Its energy source is hydrogen, which can be produced from many renewable energies and nuclear energy and thus does not depend on imported oil. Depending on the primary energy source, it can be a totally zero-emissions vehicle, that is, with zero carbon in the energy cycle. Our studies to-date show that acoustic noise is very low. Utilization of fuelcell shunt locomotives in urban railyards can prevent many cases of diesel emissions-based illnesses because such yards are frequently surrounded by residential housing that receives a high concentration of diesel particulates and nitrogen oxides; line-haul locomotives, in contrast, tend to disperse their emissions over much broader geographic areas.
We thank the following funders for their generous support of the work, both mining and rail, mentioned in this paper: US Department of Energy (contracts DE-FC36-99GO10458 and DE-FG36-05GO85049); Natural Resources Canada (Emerging Technologies Program contracts 23440-991022-001); US Department of Defense, Defense Logistics Agency (contracts DAAB07-03-D-B006-0073 [ARINC], W9132T-08-C-0045 [CERL], F42620-00-D0036 and F42620-00-D0028); BNSF Railway Company; subcontractors to Vehicle Projects Inc who contributed project cost-share; and the Fuelcell Propulsion Institute. Disclaimer: Funding support from the US Department of Energy, US Department of Defense, Natural Resources Canada, Government of Canada, or BNSF Railway Company does not constitute an endorsement by same of the views expressed in this paper.
About Dr. Arnold Miller
 A. R. Miller, K. S. Hess, D. L. Barnes, and T. L. Erickson, System design of a large fuelcell hybrid locomotive, Journal of Power Sources, 173 (2007), 935-942.  A. R. Miller, J. Peters, B. E. Smith, and O. A. Velev, Analysis of fuelcell hybrid locomotives, Journal of Power Sources, 157 (2006), 855-861.  A. R. Miller and J. Peters, Fuelcell hybrid locomotives: Applications and benefits. Proceedings of the Joint Rail Conference, Atlanta, 6 April 2006.  A. R. Miller, Variable hybridity fuelcell-battery switcher. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 19 September 2006.  A. R. Miller, Fuelcell hybrid switcher locomotive: Engineering design. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 14 September 2007.  K. S. Hess, T. L. Erickson, and A. R. Miller, Maintenance of the BNSF fuelcell-hybrid switch locomotive. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 22 September 2008.  A. R. Miller, Tunneling and mining applications of fuelcell vehicles. Fuelcells Bulletin, May 2000.  A. R. Miller and D. L. Barnes, Fuelcell locomotives. Proceedings of Fuelcell World, Lucerne, Switzerland, 1-5 July 2002.  A. R. Miller, Least-cost Hybridity Analysis of Industrial Vehicles. European Fuelcell News, Vol. 7, January 2001, pp. 15-17.  State of California, California Environmental Protection Agency, Air Resources Board (CARB), “Emission Reduction Plan for Ports and Goods Movement in California,” 2006.  US Environmental Protection Agency, “Control of Emissions of Air Pollution from Locomotive Engines and Marine Compression-Ignition Engines Less Than 30 Liters per Cylinder,” EPA-HQ-OAR-2003-0190, FRL-8545-3, RIN 2060-AM06, 2008.
 A. R. Miller, K. S. Hess, D. L. Barnes, and T. L. Erickson, System design of a large fuelcell hybrid locomotive, Journal of Power Sources, 173 (2007), 935-942.
 A. R. Miller, J. Peters, B. E. Smith, and O. A. Velev, Analysis of fuelcell hybrid locomotives, Journal of Power Sources, 157 (2006), 855-861.
 A. R. Miller and J. Peters, Fuelcell hybrid locomotives: Applications and benefits. Proceedings of the Joint Rail Conference, Atlanta, 6 April 2006.
 A. R. Miller, Variable hybridity fuelcell-battery switcher. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 19 September 2006.
 A. R. Miller, Fuelcell hybrid switcher locomotive: Engineering design. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 14 September 2007.
 K. S. Hess, T. L. Erickson, and A. R. Miller, Maintenance of the BNSF fuelcell-hybrid switch locomotive. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 22 September 2008.
 A. R. Miller, Tunneling and mining applications of fuelcell vehicles. Fuelcells Bulletin, May 2000.
 A. R. Miller and D. L. Barnes, Fuelcell locomotives. Proceedings of Fuelcell World, Lucerne, Switzerland, 1-5 July 2002.
 A. R. Miller, Least-cost Hybridity Analysis of Industrial Vehicles. European Fuelcell News, Vol. 7, January 2001, pp. 15-17.
 State of California, California Environmental Protection Agency, Air Resources Board (CARB), “Emission Reduction Plan for Ports and Goods Movement in California,” 2006.
 US Environmental Protection Agency, “Control of Emissions of Air Pollution from Locomotive Engines and Marine Compression-Ignition Engines Less Than 30 Liters per Cylinder,” EPA-HQ-OAR-2003-0190, FRL-8545-3, RIN 2060-AM06, 2008.