Rail Vehicles: Fuel Cells pps

Rail Vehicles: Fuel Cells AR Miller, Vehicle Projects Inc. and, Supersonic Tube Vehicle LLC, Golden, CO, USA & 2009 Elsevier B.V. All rights reserved. Introduction This article concerns the rationale, history, principal issues, and potential of fuel cell-powered rail vehicles. Issues include fuel cell type, hydrogen storage, special factors affect ing fuel cell rail, and the question of which rail applications are appropriate for hybrid powertrains. It concludes with a brief discussion of a supersonic concept vehicle, a cross between a train and an airplane that operates in a hydrogen-filled tube and levitates on a gas film, thereby overcoming an inherent efficiency limitation of aircraft. Why Fuel Cell Rail? Carbon dioxide emissions and energy security are related issues affecting the rail industry and transportation sector as a whole. They are related by the fact that in many nations nearly 100% of the energy for the transport sector is based on oil, and oil is an insecure primary energy and the principal source of carbon dioxide emissions. World oil reserves are diminishing, prices have recently reached unprecedented heights and volatility, and political instability threatens supply disruptions. A consensus has been reached that the burning of fossil fuels and consequent atmospheric release of waste carbon dioxide is a significant factor in global climate change. The greenhouse gas effect is the likely cause of melting of the polar ice caps and the increased severity of storms. Catenary-electric and diesel-electric are the two dominant, conventional types of locomotive, and the for- mer superficially appears to be a solution to both prob- lems. However, a factor potentially affecting both energy security and carbon dioxide emissions is energy efficiency (traction work divided by chemical energy of the fuel), because a more efficient locomotive uses less energy and, for most locomotives, burns less oil. When viewed as only one component of a distributed machine that includes an electricity-generating plant, possibly coal- or oil-fired, catenary-electrics are the least energy-efficient loco- motive type. Diesel-electric locomotives, although col- lectively worse air polluters than an equal number of catenary-electric locomotives driven by coal-fired power plants, are more energy-efficient overall. Moreover, a ca- tenary-electric is much more costly than an equivalent diesel-electric locomotive because of the higher infra- structure costs (US$6–8 million per mile). Relatively low infrastructure cost is the reason that diesel-electrics are almost universally used on large landmasses with dis- persed population centers, such as the USA. The lower energy efficiency of the catenary-electric locomotive is most accurately shown in a ‘well-to-wheels’ analysis. A complete analysis would include the energy consumption of the ‘well’, for example, the energy to pump and refine oil or the energy to mine and process coal. Moreover, the efficiencies depend on the specifics of the applica tion, in particular, the duty cycle. To make a meaningful comparison by using a common primary energy, consider using a diesel engine as the prime mover in the two types of locomotives undergoing the same duty cycle. For a catenary-electric, the following are the midpoints of the typical range of efficiencies for the various processes involved in taking the energy of diesel fuel to traction power in the locomotive: Mitsubishi 8 MW diesel engine-alternator for an electricity-gener- ating plant (43.5%), voltage conversion (97%), copper transmission from power plant to locomotive (80%), and onboard conversion to traction power (85%). The product of these estimates gives the estimated overall efficiency of a catenary-electric locomotive as 29%. Coal-fired steam-generating plants have similar, but probably lower, effici encies compared to the diesel plant. For a diesel-electric with the prime mover onboard, the midpoint efficiencies are as follows: 3 MW onboard diesel engine (37.5%), engine ancillaries (94%), alternator (96.5%), and onboard conversion to traction work (90%). Estimated overall efficiency for a diesel-electric loco- motive is therefore 31%. While the efficiencies of the two conventional types of locomotives are similar, this an- alysis dispels any misconception that a catenary-electric locomotive is a high-efficiency vehicle. However, compared to other common forms of transport, either type of conventional locomotive pulling a train is much more energy efficient: rail freight is 3–4 times more efficient on a tonne–km basis than rubber- tired road trucks and 50 times more efficient than air- freight. The poor efficiency of airfreight is due primarily to the power required to overcome induced drag, the drag caused by the wings diverting the incoming air to downwash and there by providing lift to hold the vehicle aloft. The equation for induced drag is as follows: D i ¼ C i w 2 ð1=2Þb 2 rV 2 ½1 where D i is the induced drag (force), C i is the coefficient of induced drag specific to an airplane, w is the airplane 313 . principal issues, and potential of fuel cell-powered rail vehicles. Issues include fuel cell type, hydrogen storage, special factors affect ing fuel cell rail, and the question of which rail applications are. Rail Vehicles: Fuel Cells AR Miller, Vehicle Projects Inc. and, Supersonic Tube Vehicle LLC, Golden, CO, USA &. an inherent efficiency limitation of aircraft. Why Fuel Cell Rail? Carbon dioxide emissions and energy security are related issues affecting the rail industry and transportation sector as a whole.