Foryears,theautomobileindustryhasbeentestingvehiclesthatusehydrogenasfuel.Now,peopleacrosstheUnitedStateshavehadachancetoseeandevendrivecarsthatgetpowerfromhydrogenfuelcells(燃料电池). Butthehydrogenfuelcellisnotanewidea.ThefuelcellwasfirstinventedbySirWilliamGroveofBritainin1839.Sincethen,manydifferentdesigns,havebeeninvented.Thereisoneplacewherefuelcellsareaproventechnology:inspace.TheAmericanspaceagencyusedfuelcellsinitsApollospaceshipsinthetwentiethcentury. ThemostusefulfuelcellfortransportationpurposesisthePolymerElectrolyteMembrane,orP.E.M.fuelcell.ItissimpleandcanoperateattemperaturesofsixtytoeightydegreesCelsius.Thatismuchlowerthanotherfuelcelldesigns.AP.E.M.fuelcellhastwosidesdividedbyathinmembrane(膜).Hydrogengasisforcedthroughonesidewhereitcomesincontactwithareactivematerialcontainingthemetalplatinum(铂).Themembraneseparatestheelectrons(电子)fromtheprotons(质子)inthehydrogenatoms.Theprotonspassthroughittotheothersideofthefuelcell.Buttheelectronsarecapturedtodowork;likepoweringamotor.Oxygenfromtheairisforcedintotheothersideofthefuelcell.There,thegasmeetstheprotonsthathavepassedthroughthemembrane.Theycombinetoformwaterandheat.Asinglefuelcelldoesnotproducealotofelectricity.Butwhenmanyfuelcellsarecombined,theycanproduceenoughelectricitytopoweravehicle.Theproductofthechemicalreactionthatpowersfuelcellsiswater.Thismakesfuelcellsaverycleantechnology. Hydrogenfuelcellcarshavebeenslowtodevelopbecauseofmanytechnicalproblemsthathavetobesolved.Forexample,itisunclearhowlongthemembranesinP.E.M.fuelcellswilllast.Also,fuelcellsneedwaterfortheirchemicalreactions.Theymustbedesignedtostarteasilyatlowtemperaturesandindryclimates.Andsmaller,lesscostlyfuelcellsmustbedesignedbeforetheycantrulytaketheplaceofgasolineengines.Nowmoremodelsoffuelcellvehiclesarebeingtestedthaneverbefore.Thethreatofclimatechangeandthehighcostofoilhaveincreasedinterestinthesevehiclesthatdonotcausepollution. |