Ultralight Rail and Energy Use Ultralight Rail and Energy Use

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  • 8/2/2019 Ultralight Rail and Energy Use Ultralight Rail and Energy Use



    Ultralight Rail and Energy Use

    Dr. John A. Dearien

    CyberTran International, Inc.

    As Published In: Encyclopedia of Energy, Elsevier Publishing, Cutler J. Cleveland,EditorIn-Chief, March 2004.

    I. IntroductionII. Definition of Ultralight RailIII. A Brief Discussion of Conventional RailIV. Capacity and Energy Consumption of Highways

    V. Ultralight Rail - Operational CharacteristicsVI. Energy Requirements of Ultralight Rail and Conventional RailVII. Energy Saving Opportunities with Ultralight RailVIII. Bibliography


    Guideway The rail, support structure, powerdelivery conductors, and control sensors thatmake up the path on which ultralight vehiclesmove.CONSIST An individual unit or multiplevehicles traveling in a linked setHEADWAY The time period between trainsor individual vehicles passing a particular pointon the guideway.GRADE The slope, or inclination, of theguidewayPPHPD (Passengers per hour per direction)The measure of capacity of a rail transitsystem, in terms of the maximum number ofpassengers the system can move in one

    direction.kWhr (Kilowatt hour) Base energy unit 1kilowatt of power used for one hour

    I. INTRODUCTIONIn order to best describe the relationship

    between ultralight rail and energy, it is

    necessary to establish a basis of understanding.This basis is best defined in terms of the energyrequirements of known and familiar modes oftransportation, since there are so few examplesof ultralight rail in operation at the moment.

    This article establishes this basis in terms ofconventional rail systems, and where applicable,bus, automobile and truck systems. The readeris taken through the basic characteristics of bothconventional and ultralight rail systems,followed by a comparison of the two systems,with an emphasis on the energy aspects of theirdirect operation. The energy aspects ofultralight rail in the overall transportationsystem of the United States is analyzed anddiscussed.


    Ultralight rail (ULR) is at the low end of thespectra of weights of rail vehicles, generallyconsidered as any vehicle with a loaded weightless than 10,000 pounds and with a more

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    personal type of operation (Irving, 1978). Thiscompares with Light Rail Transit (LRT,www.travelportland.com/visitors/transportation.html ) vehicles that can weigh over 100,000pounds loaded and the locomotives that pull

    freight, commuter, and Amtrak trains andweigh over 300,000 pounds. The weight of apassenger vehicle on what is classified as aHeavy Metro Rail, like BART in the SanFrancisco Bay area (www.bart.gov ), the NewYork City subway, etc., can actually weigh less(around 60,000 pounds) than an LRT vehicledue to its construction and propulsion system(Light referring more to total passengercapacity than individual vehicle weight).

    Figure 1 CyberTran Vehicle on Test Track

    in Alameda, California

    In the ultralight range of steel wheeledrail vehicles, there are several technologies indevelopment but none in operation. CyberTran(www.cybertran.com), shown in Figure 1, is anexample at the top of the range (10,000 pounds,loaded) and an Australian technology,Austrans (www.Austrans.com ), is somewhat

    lighter at approximately 6600 pounds, loaded.Futrex (www.futrexinc.com) is between theultralight range and the LRT, or full size railvehicles, weighing approximately 20,000pounds loaded.

    There are several systems with vehiclesin the ultralight category that utilize rubbertired vehicles and channel type guideways,

    such as TAXI 2000 (www.taxi2000.com ) andthe ULTra system (www.atsltd.co.uk) at theUniversity of Bristol in Cardiff, England. TheMorgantown People Mover(www.wvu.edu/~facserv/prt.htm ), shown in

    Figure 2 Morgantown People Mover Vehicle

    Figure 2 at the University of West Virginia,Morgantown, WV is just over the 10,000 poundloaded weight (9000 pounds empty with apassenger capacity of 21), but represents thebest operating example of ultralight typesystems. While these rubber-tired systems sharemany of the energy saving aspects of ultralight

    rail, they have a larger rolling friction than steelwheel on steel rail. The reader should keepthese systems in mind regarding energydiscussions that are functions of size, passengerload, small infrastructure costs due to vehiclesize, and vehicle movement options generatedby small vehicles. An excellent coverage ofultralight systems and innovative transportationconcepts under development can be reviewed atthe website of Professor Jerry Schneider,University of Washington.




    Regardless of the weight of the vehicle ultralight to heavy metro - a steel wheel on asteel rail is the most energy efficient way to

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    move a load over land. This efficient processwas initiated by placing a iron rimmed wagonwheel on a iron plated beam, allowing draftanimals to pull much heavier wagon loads.With the advent of steam engines to pull the

    wagons and flanges to keep the wagon wheelsfrom slipping off the rails, the essence of themodern railway was born in the early 1800s inthe coal mines of England, and quickly spreadover the rest of the world. The energyefficiency of the basic steel wheel on steel railsystem was further enhanced with the advent ofroller bearings on the axles and propulsionsystems with electric and diesel-electric powerplants.

    A. Energy Efficiency of Steel Wheel on SteelRail

    The primary reason for the energyefficiency of steel wheel on steel rail vehiclesis the extremely low rolling resistance of thewheel, even under very high loads and/orstresses. A typical loaded freight car canweigh as much as 280,000 pounds, beingsupported by 8 wheels, with each wheelsupporting over 35,000 pounds. This wheelload is supported through a contact patchapproximately the size of a dime, resulting in acontact stress between the wheel and the rail ofaround 100,000 pounds per square inch (psi).While this stress actually deforms the steelwheel and the steel rail, the energy lost in thisprocess is small compared to the energy it takesto deform and roll a rubber tire under heavyload. The force required to roll a standardrailroad vehicle on level ground isapproximately 2 4 pounds per ton of vehicleweight. (Armstrong, 1994)

    B. Conventional Systems - Vehicle Weights

    and Capacities

    Conventional transit vehicles typicallyweigh much less than loaded freight cars, butstill represent a heavy load to place on wheelsand rails. A BART car weighing 80,000pounds loaded, and supported by 8 wheels, has

    a per wheel load of 10,000 pounds. ArticulatedLRT vehicles generally have 3 sets of 4 wheeltrucks, and with loaded weights up to 120,000pounds, results in a load of 10,000 pounds perwheel. These vehicles roll even more efficiently

    than heavily loaded freight cars, but stillrepresent a sizable load, with energy absorbingdeformation of the wheel/rail contact area.Rolling friction of typical transit vehicles are onthe order of 3 pounds per ton. Figure 3 shows atypical LRT vehicle, operating at ground levelin Portland, Oregon.

    Figure 3 LRT Vehicle in Portland, Oregon

    Figure 4 shows an example of a HeavyMetro Rail system, BART, operating onelevated track in the San Francisco Bay area.LRT vehicles can transport over 100 passengersper vehicle and a 10 car BART train can carryover 1000.

    Figure 4 BART Train on Elevated Track

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    C, Operation of Conventional Rail Transit


    The operational process of picking uppassengers and moving vehicles around thesystem is an area where ultralight systems

    differ significantly from conventional railtransit systems, resulting in opportunities forenergy and operational cost savings.Conventional rail transit systems generallyoperate as a linear system, i.e., vehicles ortrains proceed down the track in sequence, witheach train stopping at each station andloading/unloading passengers. The NYCsubway system is a rare exception to thisprocess, having express trains that bypasscertain stations in favor of decreasing the travel

    time to just a few stations. The NYC systemrequires an additional set of tracks in order tooperate in this fashion. For most conventionalsystems in the world, however, the trains run insingle file along the system, with the averagespeed of the system governed by the rate atwhich the trains can be cycled through eachstation. For an average station, it takes about30 seconds for a train to approach a station andcome to a complete stop, another 30 45seconds to open the doors, unload/loadpassengers, then close the doors, and another30 seconds or so to clear the station withenough margin for the next train to come in.The smallest delay in any of these functionsslows the entire line of traffic, with subsequentnegative impact on the average speed of thesystem. Minimum headways of 1.5 3minutes are the norm when safety margins areincluded. Ultralight systems use a differentoperational process (explained in Section V)that minimizes the effect of local delays,resulting in a positive effect on average systemspeed.

    D. Passenger Flow Rates of Conventional

    Rail Systems

    Capacities of conventional rail systemsvary substantially, depending on the capacityof each vehicle or train, the headway between

    trains, and the speed of the trains. The LRTsystem in Portland, Oregon (TransportationResearch Board, SR# 221, 19