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Energy&Sustainability
Lecture17:FossilFuels–Cars
AndReview
March10,2009
Newton’s Laws:
1) body in motion stays in motion 2) F = m a
-You are driving at constant 60 mph Q: what is a? A: 0
- then why does engine need to run? A: FRICTION Microscopically: weak bonds are made and broken
- converts KE into thermal energy
Energy usage in transportation
EnergyUsageinTransportation
• Q:whatarekindsoffriction?• A:Rolling,Sliding,Static• Inacar:engine;tires;drag
• Slidingorrollingfriction:F=µmg:coeff.offrictionxweight
– Ifma=F=µmgthenthemaxa=µg
• Aerodynamicdrag:F=ρCdAv2:ρisfluiddensity;Cdiscoeff.ofdrag;Aisarea;
Cd=1.17forflatplate,0.3forgoodaerocar,0.9ofbicyclist
MilesPerGallon
• Power=Fv=A+Bv+Cv3A:enginelosses,idling,accessoriesB:rollingfriction
C:drag• Energy=Powerxtime
• Time=distance/v
• Energy=d(A/v+B+Cv2)• MPG~d/E=1/(A/v+B+Cv2)
• Goesas~v/Aforsmallv,1/(Cv2)forlargev:
• Typicalmaxaround40–60mphdependingonA,C
VWGolfGTI
~v/A for small v 1/Cv2 for high v
Trainsaremuchmoreefficientthancars‐Why?
1) rolling friction << less (metal on metal) 2) A per volume much less ( cars draft each
other)
BacktoAutos• Fourplacesenergyisexpended
1)idling/AC/radioetc.
2)accelerating3)overcomingfriction(rolling,drag)
4)climbinghills
A1300kgcaronasphaltw/regtireswillneedaforceof400Nforrolling.
Thislimitsacarofthiswgttoabout60MPGevenatslowspeedsIfyouuselowresistancetiresyoucanpushthisafactorof2(The
Priushaslowresistancetires)–Thisiswhyitisimportanttokeepyoutiresinflatedproperly
EnergycontentandCO2emission
Review
• Theexamisacombinationofafewsimplecalculationsandshortanswerquestions
• Exampleforshortanswerquestion:– Whyishydroelectricityusedinpeakpowerproduction?
– Becauseitcandeliverelectricalpowerondemandandquicklythroughforexampleapumpedstoragepowerplant.
Formulasonthelastpageoftheexam
Rule#1
• 1stLawofThermodynamics:
Energy can never be created or destroyed
Energy is conserved
Or in other words
Rule#2
• 2ndLawofThermodynamics
A “disordered” Universe is far more probable than an “ordered” one
There is an irreversible tendency toward a disordered Universe full of useless, low-grade energy
ProbabilityandEntropy
• The2ndLawforisolated,randomsystemswithalargenumberofelements(likeourUniverse):– “Disorderismuchmoreprobablethanorder”
– “thedirectionofspontaneouschangeasaresultofrandominfluenceisfromorder(lowprobability)todisorder(highprobability)”
• Entropyistheaquantitativemeasureoftheextentofdisorderinasystem
WhatisEnergy?• PhysicsDefinition‐Thecapacitytodowork• Severaldifferentformsofenergy:
– kinetic,potential,thermal,electromagnetic,chemical,nuclear,andmass
• Energyisconserved– Energycannotbecreatedordestroyed‐onlytransformedfromoneformtoanotherortransferredfromonesystemtoanother
• Workisaforcetimesadistance‐– Exampleraiseanobjectup‐giveitpotentialenergy– Applyaforcetoacar(bythewheelsontheroad)overadistanceanditgains(orloses)Kineticenergy
Page19
EnergyUnits• Joule=1kgm2/s2‐Metricunitofenergy
• calorie=energytoraisetemperatureof1gofwaterbyonedegreeC
• 1calorie=4.186J
• Calorie(food)=1kcal=1,000calories
• 1kcal(Calorie)istheequivalentenergytokeepa100wlightbulbonforabout7minutes
• BTU(BritishThermalUnit)=energytoraisetemperatureof1lbofwaterbyonedegreeF=1,055J=0.25Kcal
Whatisworkagainstgravity?
h w=mg
• Workdonetoliftblock=mghThisresultsinpotentialenergy
FormsofEnergy
• Work=f*dinthedirectionofforce• Kineticenergy=1/2mv2
• GravitationalPotentialEnergy=mgh,wherehcanbee.g.inthecaseofpumpedstoragetheeffectivehead;g=9.81m/s2istheaccelerationduetogravitation;misthemass
• Fallingbodyhasspeedv=(2gh)1/2
WhatisPower? Definition- Rateofenergyexchangebetweentwosystems:energy/time
Mayrepresentaflowofwork,heat,orboth
Units:1W=1J/1s
Power• Rateofdoingwork• Icanrunupa3mflightofstairsin~5s
• Mgh=65kg*10m/s2*3m=1950J
• Power=1950J/5s=390Watts
• Averagepower‐2400kcals/day‐~100kcals/hr=418kJ/h=418,000J/3600s=118W
• BasalMetabolic(resting)Rate~0.6kcal/h/kgsoforme
• BMR=65*0.6=39kcals/h~46WSothatishowmuchheatIproducewhiledoingnothing
Units• Largenumbers:
103
106
109
1012
1015
1018
Unitsofpowerandenergy 1TW=1millionmillionW=1012W
Example:we,theworldpopulation,withourconsumptionrateof~16TW,convert16trillionjoulesofprimaryenergyeverysecondintoformsofenergywewant(+wasteheat)
1kWhistheamountofenergyconvertedinonehouratarateofonekilowatt 1kWh=3.6MJ
Page26
U.S.EnergyConsumptionby Source
U.S.EnergyUse
• In1991,theU.S.consumed81.5quads
• Estimatedusefor2000was96.2–100quads• Howmuchisaquad?
– 1quad=1015(1,000,000,000,000,000)BTUs– 1BTU=energyrequiredtowarm1lbwater1oF
– 1quad=1.05x1018J‐>100quads=~1020J
AveragePowerPerPersonintheUS
• 100quads‐howmuchaveragepoweristhat?
– ~πx107seconds/year=3.15x107seconds/year– 1020J/year/3.15x107seconds/year=3x1012W
– 3trillionwattsistheaveragepowerconsumedintheUS– 300Millionpeople
– 3x1012w/3x108people=104w/person=10kW/person• 24hrsperday(includesindustry,travel,heating/AC‐everything
• 10kW*86,400sec/day=864,000J/d=206,000kcal/d• Orabout100timesourbasic/primitiveenergyneeds
Population• Currentlythereare6billionpeopleonearth(6x109)• Therateatwhichpopulationgrowsisproportionaltothe
existingnumberofpeople– Thenumberofpeopleborndependsonthenumberofpotentialparents
– Atthecurrentrateofgrowththepopulationdoublesevery35years(aspeoplelivelongerthisgetsshorter)• Ifyou(andapartner)have2childrenby35andtheydothesamewhenyouare70therewillbesixofyou.
– Thenassumingyoudieoff(whichhavingkidscancause)thepopulationhasgonefrom2whenyouwhere<35to4whenyouaregoneat70…
• Thisisexponentialgrowth
Thelilypad
• Alilypaddoublesinsizeeveryday• Itstartsat1/1,000,000thesizeofthepond• Howlongdoesittaketofillthepond?
– 2n=1,000,000– 210=1024=~1000– 1,000x1,000=1,000,000=106– 210x210=220=~1,000,000– So~20days
ExponetialGrowth•
•
• •
•
ElectricityBasics• Carriersofelectricity:electrons• Current:
– Symbol:I=Q/t– numberofelectronspersecond
– Unit:amporA,1A=1C/s,e≈1.602x10‐19C
1Aisdefinedasthecurrentrequiredtoproduceamagneticforceof2x10‐7N/mbetweentwoinfinitelylong
thinwiresspaced1mapartinthevacuum
• Voltage:- Symbol:V=W/Q
- differenceinelectricalpotentialthatasupplymaintainsbetweenitsterminals,ameasureoftheenergysuppliedtoelectricchargesastheypassthrough
- Unit:1V=1J/1C,energysuppliedis1J
ElectricityBasics(2)
• Resistance:– SymbolR=V/I
– Ohm’slaw:resistanceofacomponentisthevoltageacrossitdividedbythecurrentflowingthroughit
– Resistanceiscomponentdependent
– Maynotbeinpracticeaconstant(e.g.increasingcurrentinawiremaycauseincreasingcomponenttemperatureandusuallycausesincreasingresistance
– V=RxI– Unit:1Ω(ohm)=1V/1A
ElectricityBasics(3)
• ElectricPower:– rateatwhichenergyistransformed
– Proportionaltotheproductofthevoltageandthecurrent:P=VxI=RxI2=V2/R
- Relationshipholdsequallyfortheelectricalpowerprovidedbyasupplyorthepowerbeingdissipatedasheatinacomponent
- Unit:1W=1Vx1A
• Unitofstoredcharge,e.g.inacarbattery:Ampere‐hour:1ampere‐houristheelectricchargetransferredbyasteadycurrentofoneampereforonehour
LossesinPowerTransmission
• V=IR• PowertransmittedisP=VI
• PowerdissipatedbyP=I2R• Ploss=I2R=P2/V2R
• Soforfixedpowertransmittedthehigherthevoltagethelowerthecurrentandthelesstheloss
• ModernTransmissionrunsat380KVto735KV
Transformer
• Transformsvoltagesinanelectricalsystem• Stepuporstepdown• Workonalternatingcurrents(mutualinteractionof
changingelectrical
andmagneticfields)
• Idealtransformer:
• Vp/Vs=Is/Ip(Pp=Ps)
• Vp/Vs=Np/Ns
ElectricityFlow
65 % losses
U.S.vsUtah
Compared to Utah:
Coal: 82%
Hydroelectric Power: 1.2%
CapacityFactorThe amount of energy that a power plant actually generates compared to its maximum rated output, expressed as a percentage.!
BalancingSupplyandDemand:‘MeritOrder’
• Baseload:lowestrunningcosts,usuallynuclearorlargecoalfiredstations(>600MW),thermalefficiencyof~40%,buttakes8hourstorampup
• Middlemeritorderorintermediate:smallercoal‐firedstationswithlowerthermalefficiencies
• Peakingplants:simplegasturbines,thermalefficiencyunder30%,possiblefuels(naturalgasorkerosene)arelikelytobemoreexpensive,butcanberampedupinthematterofminutes
CanadianLoadDurations• UShaslesshydroasafractionandmorenuclearinourbaseload
<- Correlated demand
HydroelectricityandPumpedStorage
BenefitsofHydro‐electricity• NoCO2
• Noparticulatesorchemicalcompoundssuchasdioxinsthatareharmfultohumanhealth
• Noemissionofradioactivity• Nomajorexplosionsorfire• Oftenassociatedwithpositiveenvironmentaleffectssuchasfloodcontrolorirrigation
• Valuedamenityorevenavisualimprovementoflandscape
DeleteriousEffects
• Hydrologicaleffects–waterflows,groundwater,watersupply,irrigationetc.
• InthecaseoftheGabcikovo‐NagymarosProject– fallinthewatertable– Wellsdryingup
– Vegetationdying– Uniqueformsofwild‐lifeindanger
• Socialeffects• CanproduceMethan
Projections
• Hubbertetal.
KeyAssumptions:EIA’sInternationalEnergyForecast
• Potentialimpactsofproposedlegislationorstandardsarenotreflectedintheprojections
• Potentialimpactsoflegislationforwhichimplementingmechanismsarenotsetalsoarenotreflectedintheprojections
• Projectionscomefromanintegratedsetof16regionalmodelsthatreflecteachregion’sexistingenergyusepatterns,energyinfrastructure,andcostsforexistingandalternativeenergytechnologies
• Forfurtherdetailssee:http://www.eia.doe.gov/oiaf/ieo/pdf/0484(2007).pdf
8
AnnualGrowthinElectricityGenerationbyRegion(2004‐2030)
Non-OECD
OECD – Organization for Economic Co-operation and Development
Source: EIA, International Energy Outlook 2007
9
Non-OECD
OECD
AnnualGrowthinLiquidsConsumptionbyRegion(2004‐2030)
Source: EIA, International Energy Outlook 2007
10
0.0
1.9
2.3
2.2
FutureChallengesandOptions
85%ofthatincreaseisintheU.S.,China,India,&otherAsia
U.S.,ChinaandIndiaaccountfor86%oftheincreaseinglobalcoaluse
GlobalCO2emissionsincreaseby60%
90%oftheincreaseinCO2emissionsoccursintheU.S.,China,India,&otherAsia
Coalaccountsfor49%ofglobalCO2emissiongrowth
Oilaccountsfor29% NaturalGasaccountsfor21%
Source: EIA, International Energy Outlook 2007
WorldPrimaryEnergyConsumptionoverNext25YearsWithoutCarbonConstrainingTechnology
17
World primary energy consumption Increases 57%
Thearticles/talks
• Article:4pagesexcludingfigures,doublespacing,withreferences
• Talks:10to15minutes,about10slotsavailable
• ExtraCredit:Youmayhandinanarticleinadditiontoyourtalk
Thearticles/talks
• Introduction:Whatisthequestion/problemdiscussed?Whatisthecontext?
• Scientificbackground• Economicalbackground
• Politicalbackground• Prosandcons• Conclusion• Baseyourargumentationonsolidnumbersforwhichyoucangivereferences
Presentations
• Gradingwillbeonpresentation.– Isyourpresentationclear?– Isitpersuasive?– Didyouusedatatosupportyoursuggestions?– Didyoucoverthekeypoints
Deadline
• Pleasesendmeyourcompletearticlesandcompletepresentationsby
THURSDAY,MARCH272009