1ABattery
Battery powered car
No polluting gases
There’snothingnewabout electricvehicles.Foralong timeithasbeenpossibleto buildavehiclewithalarge batteryinsideit,thatmakes itgo.
Thebatteryisn’tthesame sortthatyouwouldputin atorch,althoughitdoes thesamejob.Thebattery needschargingupby pluggingitintothemains.
Then,asthevehicleisdriven, thebatteryrunsdown.
Batterypowered vehicleshaveanumberof advantagesoverpetrolordiesel poweredvehicles; theyaremuchquieteranddon’treleasepolluting gases(althoughofcoursethepowerstations
thatprovideelectricitytochargethemupmay have).Theydohoweverhavealimitedrange;and canonlygosofarbefore theyneedchargingagain. Thismeansthattheyareoftenusedincities,
wherethelackofnoiseandpollutionisparticularly important.Thelowerspeedsandlimitedrangemay wellbeless ofanissue,asdistancestravelled may beless andspeedlimitsarelower.
Thecostofelectricitytorunanelectricvehicleis muchless thanthecostofthefuelforasimilarly sizedpetrolor dieselvehicle.However,the batteriesareveryexpensiveandcanonly
berechargedacertainnumberoftimes.
1BFuel cell powered vehicles
Afuelcellpoweredvehicle hasanelectricmotorbutit isn’tpoweredbyabattery. Insteadtheelectricity comesfromafuelcell.
Typical fuel cell batteries
Electricity
Hydrogen
_
_
_
_
O O
_+O O
+O
_
Oxygen
+O
Howa fuel cell works
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+O
O
HeatWater
Youmayknowthatwaterisacompoundof hydrogenandoxygen(HO)andyoumayhave seenor readaboutanexperimentinwhich electricityispassedthroughwater,splittingit upintothesetwogases.Afuelcellworksthe otherwayaround,insteadofusingelectricity andreleasingthegases,ituses thegasesand releaseselectricity.Ituses hydrogenfroma storagetankandoxygenfromtheatmosphere.
Fuelcellsareamoreexpensivewayofpowering motorsthanusingbatteriesbutthevehiclescan haveagreaterrange.
Howa fuel cell works
•Afuelcelltakesenergyfromchemicals, usuallyhydrogenandoxygen,andreleases itaselectricity.Theoxygensupplyiseasy
toarrangeasitcanbetakenfromthe atmospherebutthehydrogenneedsto bestoredinatank.Hydrogenishighly flammablesoithastobeusedcarefully.
•Atthecentreofthecellisamembranewhich isoftencoatedwithplatinum;this actsasa catalystandspeedsup thereaction.
•Fuelcellshavebeenextensivelyusedinspace craft,suchastheApollo moonmissions.
Theircostsarestillhighbutarecomingdown.
1CDiesel
Dieselengine vehicles
Diesel-electric railway locomotive
Dieselengineshavelong beenusedinlargeroad vehiclesandincreasinglyin cars.Aroundhalfofallnew carssoldinEuropearenow dieselpowered.
Howa diesel engine works
Dieselenginesareatypeofinternalcombustion engine,meaningthattheburningofthefuel takesplaceinsidetheengine.Dieselfuel(unlike petrol)doesn’tneedasparktoigniteit;amixture ofdieselfuelvapourandairwillignitesimply
bybeingcompressed.
Dieselenginesarereliableandlonglived.However
dieselfuelenters airenters
here
airin cylinder
crankshaft
exhaust gases leavehere
cylinder
piston connecting
rod
theyreleasearangeofpollutinggases.Theyrelease less carbondioxide thanapetrolenginedoingthe samework,buttheexhaustgasesarecarcinogenic (theycausecancer).
Certainvehiclessuchassomerailway locomotives andsomebuseswhichhavedieselenginesare actually`diesel-electric’.Insteadofthedieselengine directlydrivingthewheels,asinacar,theengine drivesagenerator whichproduceselectricity. The electricitythendriveselectricmotors,whichturn
thewheels.
Intheengine,fuelisdrawnin,mixed
andcompressed.It ignites,forcingthepistondownthecylinder,makingthe connectingrod turnthecrankshaft. Therewillbeseveralcylindersdriving thesamecrankshaft.
Schemeofwork1-episode3