Led by Vehicle Projects LLC, an industry-government partnership is developing a prototype fuelcell-hybrid switcher locomotive for demonstration of (1) railyard applications in the Los Angeles basin and (2) power-to-grid at Hill Air Force Base, Utah. “Switchers” are captive vehicles that operate only in rail yards. Both demonstrations will be completed by 31 December 2008.

The 127 tonne fuelcell-hybrid switcher will be derived from the Green GoatTM, a commercially available diesel-battery hybrid switcher with a 200-kW diesel prime mover, by replacing its diesel-generator with a 250-kW fuelcell powerplant based on the powerplant of the Citaro fuelcell transit bus (see illustration). Unlike our fuelcell-hybrid locomotive, the buses are not hybrids. The 250-kW fuelcell powerplant will be comprised of two 125-kW power modules, or power building blocks. The electrically driven rear traction-motor cooling fan and brake air compressor of the Green Goat will remain in place beside the prime mover.

In yard-switching, the hybrid’s peak power is required only during acceleration of trains from rest. The critical power requirement is that the continuous rating of the prime mover equals or exceeds the mean power of the vehicle’s duty cycle. Mathematical analysis of switcher duty cycles demonstrates that 250 kW is sufficient for even heavily trafficked seaport railyards. The lead-acid traction battery allows transient power well in excess of 1 MW.

For the power-to-grid application, an offboard power converter will convert the 600-850 VDC output of the fuelcell powerplant to the three-phase AC power of the military-base grid. The hybrid locomotive can provide 250 kW of power on a continuous basis but can provide power surges in excess of 1 MW. Its low acoustic noise and vibration are essential features of its practicality in power-to-grid applications.

As part of the feasibility study for our locomotive program, we have analyzed the potential benefits of a hybrid powerplant in which fuelcells comprise the prime mover and a battery or flywheel comprises the rechargeable auxiliary power/energy device. Potential benefits of a hybrid powertrain are (1) enhancement of transient power and hence tractive effort, (2) regenerative braking, and (3) reduction of capital or recurring costs. Generally, tractive effort of a locomotive at low speed is limited by wheel adhesion and not by available power. The benefits of regenerative braking in locomotives are limited: For low-speed applications such as switchers, both the available kinetic energy and the effectiveness of traction motors as generators are low; for high-speed, heavy applications such as freight, the ability of the auxiliary power/energy device to absorb a significant portion of the available kinetic energy is low. However, total cost (capital plus recurring costs) may be reduced in fuelcell-hybrid switchers, and this is the rationale for our developing a hybrid powertrain for the locomotive.

Fourteen carbon-fiber composite tanks, located above the traction battery, store a total of 70 kg of compressed hydrogen at 350 bar. The Citaro buses use the same type of tank, located on the roof. The light weight of the carbon-fiber tanks allows the roof location without adversely affecting the vehicle’s center of gravity. We have conducted a safety analysis showing that compressed hydrogen on the roof is essentially as safe as reversible metal-hydride storage in the undercarriage bay (i.e., replacing the diesel fuel tank); the high weight of metal-hydride storage precludes the roof location. Although, with all other factors equal, reversible metal-hydride storage should be substantially safer than compressed hydrogen, the roof location improves the safety of the compressed hydrogen option: it places the tanks out of harm’s way and the buoyancy of hydrogen should allow its harmless dissipation in the event, for example, of the opening of a pressure-relief valve. In contrast, metal-hydride storage in the undercarriage bay, could allow pockets of escaped hydrogen to accumulate and thence the possibility of detonation. Based on experiments involving the burning of automobiles, a hydrogen fire in open space above the vehicle, without detonation, is expected to be safer than a diesel-fuel fire below the vehicle

Locomotives require a fixed operating weight. Because the combined weights of the fuelcell powerplant and carbon-fiber hydrogen storage system are substantially lighter than the diesel genset and diesel fuel tank they replace, a steel-plate ballast of approximately 1.0 m3 volume will be placed in the undercarriage bay.

The operating time of the fuelcell-hybrid switcher between refueling 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 and holding tank, should be between 10 and 30 minutes and depends largely on the size and pressure of the holding tank and capacity of the high-pressure hydrogen pump.

Vehicle Projects LLC is executing the engineering design of the fuelcell switcher. Several design and integration challenges arise when developing such a large hydrogen fuelcell vehicle. Weight, center of gravity, packaging, and safety were design factors leading to, among other features, the location of the light-weight compressed hydrogen storage system above the traction battery. Harsh operating conditions, especially shock loads during coupling to railcars, require component mounting systems capable of absorbing high energy. Additionally, system design must address railway industry regulations governing safety and such events as derailment, side impact from yard traffic, refueling, and maintenance. Our fuelcell control system communicates with the existing commercial vehicle controller to interpret operator demand and adjusts fuelcell powerplant parameters to meet the power requirement. This programmable automation controller (PAC) controls and executes all powerplant functions and continuously monitors the performance and safety of the hydrogen-storage and fuelcell-power systems.

Other aspects of vehicle development and demonstration, in particular, hardware fabrication, are executed by a technical consortium (see table) managed by Vehicle Projects LLC.

The overall development and demonstration project consists of six phases, as described in the table “Project Scope,” and will require 29 months for completion. As of 1 May 2006, BNSF Railway Company has committed $1 million toward the project, as an industry-government partnership, and the US Department of Defense has committed $1.950 million for federal Fiscal Year 2007 (FY07). An additional $1.5 million has been requested from DoD in the FY08 budget to execute the demonstration phases. Breakdown of the overall project costs of $4.5 million during 29 months is outlined in the budget table.

In conclusion, this fast-paced project to develop a fuelcell-battery hybrid switcher (shunt) locomotive will be completed by 31 December 2007. It will demonstrate several environmental and energy-security benefits in yard-switching applications in the Los Angeles basin and power-to-grid applications at a US Air Force base in Utah:

• It will offer zero emissions and low acoustic noise, while meeting the performance of diesel locomotives

• Its fuel will be hydrogen, and hydrogen can be produced from many sources, including coal and nuclear energy.

• Fueled by hydrogen, the locomotive itself will emit zero greenhouse gases.

• Under self-power on rails, it can deliver itself as backup power for critical infrastructure during military or civilian grid failures.

Bibliography
H. Crutzen, Compressed Hydrogen Storage, Vehicle and Hydrogen Infrastructure: the short/Medium Term Answer. Joint Research Centre, European Commission, 2003

A. R. Miller, Least-cost Hybridity Analysis of Industrial Vehicles. European Fuel Cell News, Vol. 7, January 2001, pp. 15-17

A. R. Miller, D. L. Barnes, O. Velev, L. Sheppard, P. Chintawar, A. Delfrate, M. Golben, and T. Vencill, “Fuelcell Locomotive for Commercial and Military Railways,” 2004 Fuel Cell Seminar, San Antonio, USA, 1-5 November 2004.

A. R. Miller, J. Peters, B. E. Smith, and O. A. Velev, Analysis of Fuelcell Hybrid Locomotives. Journal of Power Sources, 157, pp. 855-861, 2006

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, Fuelcell Locomotives. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 19 September 2005

A. R. Miller, Variable Hybridity Fuelcell-Battery Switcher. Proceedings of Locomotive Maintenance Officers Association conference, Chicago, 19 September 2006

A. R. Miller, K. S. Hess, D. L. Barnes, and T. L. Erickson, Fuelcell Locomotive for Seaports and Power-to-Grid Applications. Proceedings of the 2007 European Ele-Drive Conference, Brussels, Belgium, 30 May – 1 June 2007 (in press)

Acknowledgements
We thank the following funders for their generous support of this project: US Department of Energy (contract DE-FC36-05GO85049); US Department of Defense (contracts F42620-00-D0036 and F42620-00-D0028); BNSF Railway Company. Disclaimer: Funding support from the US Department of Energy, US Department of Defense, or BNSF Railway Company does not constitute an endorsement by same of the views expressed on this website.

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