Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit

Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit
Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit
Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit
Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit
Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit
download Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit

of 5

  • date post

    12-May-2017
  • Category

    Documents

  • view

    213
  • download

    1

Embed Size (px)

Transcript of Reciprocating Engine vs Gas Turbine_ Pulse Load Efficiency and Profit

  • ReciprocatingEnginevs.GasTurbine:PulseLoadEfficiencyandProfit

    Naturalgasfiredpowerplantsarethemostresponsiveandflexiblepowergeneratingassetsinelectricitymarkets.Naturalgaspowerplantsaredispatchableandcanadjustloaddaily,rampingupanddownwithdemandandbalancingtheintermittentproductionofrenewableenergysources.Forshortdurationpulseloadneededtobalancesolarandwindoutput,gasturbinesarenotprofitable.Wrtsilreciprocatingenginepowerplantsoffersignificantadvantagesovergasturbines,withhigherpulseloadefficiencyandthecapabilitytoprovideultraflexibleandcostefficientoutput.

    Gaspowerplantsareoftenrampedupanddown,orcycled,inresponsetochangesindemandandload.Thetimerequiredtorampupanddown,efficiencyatpartloadandoveralldurationorplantoutputdeterminethefuelconsumptionandeconomicperformanceofthepowerplant.Unlikebaseloadplantsthatoperatecontinuously,flexiblepowerplantscanprovideshortdurationload,orpulseload.Pulsedloadsareproducedinresponsetothesuddenlossofapowergenerator,reducedoutputfromwindandsolarsources,orspikesindemand.Pulsegenerationimprovesreliabilityandpowerqualitybystabilizingtheelectricgrid.

    ArecentassessmentbytheCaliforniaIndependentSystemOperator(CAISO)demonstratedtheneedforsignificantpulsegenerationovertwohoursduringthemorningpeak(8,000MW)andtheendoftheworkday(13,500MW)tomeetdemandwhensolarandwindarenotproducing,asshowninFigure1.ThischallengeisnotuniquetoCalifornia.Manycountriesareadoptingenergypoliciestoachieve20percentormorefromrenewablesources.SurgesinwindandsolaroutputinGermanyrecentlypeakedat59percentofelectricgenerationduringasingleday,causingconventionalpowerplantstorampdownsignificantly.

    Figure1:CAISOLoadProfileDemonstratesNeedforPulsedLoadsImage:CombinedCycleJournal

    PulseOperationandEnergyConsumptionPowerplantownerswanttooptimizeoperationtominimizefuelconsumptionandmaximizerevenue.Thestartuptime,timetorampupoutputtofullload,operatingataminimumload,andtheefficiencyatpartloaddeterminetheamountoffuelconsumed(energyinput)andthelengthoftimetheplantoperateseachday.Byproducingoutputduringpeakdemandtimes,thepowerplantearnsrevenuefromhighelectrictariffs.Rampingupanddownshouldbeasfastaspossiblewithoutriskingdamagetothepowerplantequipment.

    Combinedcyclegasturbine(CCGT)plantshavetechnicalconstraintsthataffecttheirstartuptime,ramprate,andminimumloadformaintaininghotconditions.Hotstartconditionsmaintaintemperatureandpressureinthesteamportionofthecombinedcycletoallowquickrampingofthegasturbine.CyclingraisesconcernsaboutincreasedairemissionsandthermomechanicalstressonCCGTplantequipment.Wrtsilengineshavelowerexhaustgastemperatures(360C)comparedwithagasturbine(600C)andthuslowersteamtemperatures,enablingquickerstartupandrampingtofullload.

    Typically,aloadfollowingCCGTrampsupslowlyduringearlymorninghours,operatesatfullloadduringmorningpeakdemand,curtailsoutputduringmiddayhourstoaminimumoperatingloadatwhichhotconditionsaremaintained(40to50percentoffullload),thenrampsbackupagaintofullloadfortheeveningpeak.Theplantisshutdownatnightandthenrampedupagainintheearlymorninghoursthenextday.Thisdoublepulseloadprofile,alsocalledtwoshiftingortwocyclingforatypicalCCGTcomparedwithaWrtsilFlexicycle

    http://www.wartsila.com/en/reciprocating-engine-vs-gas-turbine-part-load-efficiencyhttp://www.ccj-online.com/integrating-renewables-may-call-for-some-combined-cycles-to-start-twice-daily-increasing-emissions/http://ec.europa.eu/energy/renewables/index_en.htmhttp://www.greentechmedia.com/articles/read/Germany-Hits-59-Renewable-Peak-Grid-Does-Not-Explodehttp://www.wartsila.com/en/combined-cycle-plant-for-power-generationhttp://www.nrel.gov/docs/fy12osti/55433.pdfhttp://www.wartsila.com/en/power-plants/power-generation/applications/flexicycle

  • reciprocatingenginepowerplantisshowninFigure2.Thedurationofeachpulseis4hours,withacurtailmentinbetweenpulsesof2hours(424pulseproduction).TheshadedareainFigure2showswhenthepowerplantwouldbereceivingrevenuefrompulseproduction.

    Figure2:Twoshifting(424pulseproduction)forWrtsilFlexicycleplantcomparedwithCCGT.ThefaststartupandshutdownoftheFlexicycleplantreducesfuelconsumptionandminimizesnonproductiveoperatinghours.

    AscanbeseeninFigure2,thestartuptimeandtheminimumoperatingloadincreasethetotaltimetheCCGTplantisoperatingandthusitsoverallenergy(fuel)consumptionandoperatingexpenses.WhileatypicalCCGTrequiresabout60minutestoreachfullloadinthemorning,aWrtsilpowerplantstartwithinafewminutes.

    Thecumulativeenergyinputofa200MWWrtsilpowerplantcomparedwithasimilarlysizedCCGTfortwoshiftingoperation(424pulseproduction)isshowninFigure3.Theamountofenergyinputisafunctionoftheefficiencyofthepowerplantandthetotaloperatingtime.TherapidWrtsilstarteliminatestheneedforaloadholdpointtomaintainhotconditions,reducingtheoveralloperatingtime.Thisinturnreducestheamountofenergy(fuel)inputtogeneraterevenueproducingload.ThecumulativeenergyinputofaFlexicycleplantisfivepercentlessthanaCCGToverthesameoperatingperiod.

    Figure3:Twoshifting(424pulseproduction)cumulativeenergyinputforWrtsilFlexicycleplantcomparedwithCCGT.ThefaststartofaWrtsilpowerplantreducestotalfuelconsumption.

    Thecashflowfor424pulseproductionisshowninFigure4fora200MWplant.Thecashflowprojectiontakesintoaccountstartupcosts,fuelcosts,andO&McostsgiveninTable1.Theshadedareaindicatesnegativecashflowthepowerplantiscostingmoremoneytooperatethanrevenueearned.AscanbeseeninFigure4,aCCGTdoesnotbecomeprofitableuntiltheendofthesecondfourhourpulse.Thedeclineincashflowafterthefirstpulseisbecausethegasturbinecontinuestorunattheminimumholdpointandburnfuellessefficientlyuntilitrampsbackupagainforthesecondpulseduringtheeveningpeak.

    http://www.wartsila.com/en/reciprocating-engine-vs-gas-turbine-startup-time

  • Figure4:Twoshifting(424pulseproduction)cashflowforWrtsilFlexicycleplantcomparedwithCCGTbasedonstartupcosts,fuelcostsandO&Mcosts(seeTable1).

    Table1.CostInputsforCalculationofPulseCashFlowandIncome

    Theremaybeseveraltypesofpulseloadoutputthatapowerplantproducesoverthecourseofayearincludingonehour,twohour,fourhour,andeighthoursinglepulses,aswellas222pulseoperation.ShorterpulsesandmorecyclingdecreasetheefficiencyofCCGTsandincreasetheamountofenergyinput(fuel)perMWhofelectricityproduced.Thisimpactstheplantsprofitabilitybyincreasingoperatingandfuelcosts.Figure5illustratesthedisparityinincomeperpulsefora200MWFlexicyclepowerplantcomparedwithaCCGTofsimilarsizeforthemostcommonpulseoutputs.WhiletheWrtsilpowerplantisprofitableforanypulsedurationorcycling,aCCGTplantisnotprofitableforshortdurationpulseoperation.

  • Figure5:Incomeperpulsedoperationfora200MWpowerplant.TheWrtsilFlexicycleplantisprofitableforawiderangeofpulseoperationwhiletheCCGTplantisnotprofitable.

    PulseEfficiencyAsdiscussedabove,theefficiencyofaplantproducingpulseloadscanbedramaticallydifferentthantheefficiencyatbaseload.Thepulseefficiencyisthenetefficiencyforthedurationoftheoperatingperiod,includingstartup,shutdownandpartloadoperation.Reciprocatingenginescanreachfullloadandcurtailoutputtozerowithinminutes.Inaddition,becausetheyarebasedonmodulararchitecture,Wrtsilpowerplantscanoperateatpartloadbyrunningonlyasubsetoftheenginesatfullloadandmaintainfullefficiency.

    Theefficiencyofgasturbinepowerplantshoweverdegradesatpartload.Gasturbinesreducepoweroutputbyreducingtheflowthroughtheturbine,whichalsoreducesthecombustiontemperatureandthusefficiency.FrequentstartsandstopswillfurtherreducetheoverallpulseefficiencyofCCGTs.TheimpactofcyclingonefficiencyisseeninFigure6.WhiletheCCGThashigherefficiencyduringbaseloadoperationatfulloutput,theFlexicycleplantachieveshigheroverallefficiencyforallpulseslessthan8hourslong.ImpactsofpulseoperationonCCGTefficiencyismostpronouncedforpulsedurationoftwohoursorless.Wrtsilpowerplantsareefficientandeconomicoverawiderangeofpulsedloads,providingultraflexiblecapacityformeetingthechallengesofrenewablesintegrationandchangingdemand.

    http://www.wartsila.com/en/reciprocating-engine-vs-gas-turbine-advantages-of-modularity

  • Figure6:NetefficiencyoverpulsedurationforWrtsilFlexicycleplantcomparedwithCCGT.WrtsilplantsaremoreefficientthanCCGTsforshortdurationpulseoperation.

    2014Wrtsil