2015 ISO New England Generator Air Emissions2015 Air Emissions Report Page 2 ISO‐NE PUBLIC Figure...
Transcript of 2015 ISO New England Generator Air Emissions2015 Air Emissions Report Page 2 ISO‐NE PUBLIC Figure...
2015 ISO New England Electric Generator Air Emissions Report
© ISO New England Inc. System Planning JANUARY 2017
ISO‐NE PUBLIC
2015AirEmissionsReport PageiISO‐NEPUBLIC
Contents
Section 1 Executive Summary .............................................................................................................................. 1
Section 2 Background .......................................................................................................................................... 4
2.1 History of Marginal Emissions Methodologies .................................................................................................... 5
2.2 History of Heat Rate Methodologies ................................................................................................................... 5
Section 3 Data Sources and Methodologies ......................................................................................................... 7
3.1 Data Sources ........................................................................................................................................................ 7
3.2 Total System Emission Rate Calculation .............................................................................................................. 7
3.3 Marginal Emission Rate Calculation .................................................................................................................... 8
3.4 Marginal Heat Rate Calculation ........................................................................................................................... 9
3.5 Time Periods Analyzed ........................................................................................................................................ 9
Section 4 Data and Assumptions ....................................................................................................................... 10
4.1 2014 New England Weather .............................................................................................................................. 10
4.2 Emissions Data................................................................................................................................................... 10
4.3 ISO New England System Installed Capacity ..................................................................................................... 10
4.4 ISO New England System Energy Production .................................................................................................... 13
4.5 Locational Marginal Unit Scenarios ................................................................................................................... 14
4.5.1 All LMUs ..................................................................................................................................................... 14
4.5.2 Emitting LMUs ............................................................................................................................................ 16
4.6 High Electric Demand Days ................................................................................................................................ 17
Section 5 Results and Observations ................................................................................................................... 18
5.1 2015 New England System Emissions ............................................................................................................... 18
5.1.1 Results ........................................................................................................................................................ 18
5.1.2 Additional Observations ............................................................................................................................. 22
5.2 2015 New England Marginal Heat Rate ............................................................................................................. 22
5.3 2015 New England Marginal Emission Rates .................................................................................................... 24
5.3.1 Marginal Emission Rates for the All‐LMU Scenario .................................................................................... 24
5.3.2 Marginal Emission Rates for the Emitting‐LMU Scenario .......................................................................... 25
5.3.3 2009 to 2015 LMU Marginal Emission Rates ............................................................................................. 26
5.3.4 Marginal Emission Rates for High Electric Demand Days........................................................................... 27
5.3.5 Observations .............................................................................................................................................. 28
Section 6 Appendix ........................................................................................................................................... 29
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Figures
Figure 1‐1: Percentage energy generation by fuel type, 2006 compared with 2015. ................................................ 2
Figure 1‐2: Comparison of 2015 New England emission rates (lb/MWh). ................................................................. 3
Figure 4‐1: 2015 New England summer capacity by state (MW). ............................................................................ 11
Figure 4‐2 : ISO New England generator additions, 2006 to 2015 (MW). ................................................................. 12
Figure 4‐3: Major retirements in ISO New England, 2006 to 2015 (MW). ............................................................... 12
Figure 4‐4: 2015 ISO New England monthly generation by fuel type (% MWh, GWh). ........................................... 13
Figure 4‐5: ISO New England annual generation by fuel type, 2011 to 2015 (million MWh). ................................. 14
Figure 4‐6: 2015 percentage of time various fuel types were marginal—all LMUs. ................................................ 15
Figure 4‐7: Annual percentage of time various fuel types were marginal—all LMUs, 2011 to 2015. ...................... 15
Figure 4‐8: 2015 percentage of time various fuel types were marginal—emitting LMUs. ...................................... 16
Figure 4‐9: Annual percentage of time various fuel types were marginal—emitting LMUs, 2011 to 2015. ............ 16
Figure 5‐1: 2015 New England system annual emissions of NOX, SO2, and CO2 (ktons). ......................................... 19
Figure 5‐2: New England system annual emissions of NOX, SO2, and CO2, 2006 to 2015 (ktons). ........................... 20
Figure 5‐3: 2015 New England system monthly average NOX, SO2, and CO2 emission rates (lb/MWh). ................. 21
Figure 5‐4: New England system annual average NOX, SO2, and CO2 emission rates, 2006 to 2015 (lb/MWh). ..... 21
Figure 5‐5: 2015 LMU monthly marginal heat rate (MMBtu/MWh). ....................................................................... 23
Figure 5‐6: LMU annual marginal heat rate, 2009‐2015 (MMBtu/MWh). ............................................................... 23
Figure 5‐7: 2015 monthly LMU marginal emission rates—all LMUs (lb/MWh). ...................................................... 25
Figure 5‐8: 2015 monthly LMU marginal emission rates—emitting LMUs (lb/MWh). ............................................ 26
Figure 5‐9: LMU marginal emission rates, 2009 to 2015—all LMUs (lb/MWh). ...................................................... 27
Figure 5‐10: LMU marginal emission rates, 2009 to 2015—emitting LMUs (lb/MWh). ............................................ 27
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Tables
Table 1‐1: 2014 and 2015 New England System Emissions (ktons) and Emission Rates (lb/MWh) ......................... 2
Table 1‐2: 2014 and 2015 Average LMU Marginal Emission Rates (lb/MWh) .......................................................... 3
Table 5‐1: 2015 New England System Annual Average NOX, SO2, and CO2 Emission Rates (lb/MWh) .................. 20
Table 5‐2: 2014 and 2015 New England System Emissions (ktons) and Emission Rates (lb/MWh) ....................... 22
Table 5‐3: 2015 LMU Marginal Emission Rates—All LMUs (lb/MWh)(a, b) ............................................................... 24
Table 5‐4: 2015 LMU Marginal Emission Rates—Emitting LMUs (lb/MWh) ........................................................... 25
Table 5‐5: High Electric Demand Day LMU Marginal Emission Rates (lb/MWh) .................................................... 28
Appendix Table 1: New England Total Cooling and Heating Degree Days, 1994 to 2015 ......................................... 29
Appendix Table 2: 2015 New England Summer Capacity (MW, %)(a. b) ..................................................................... 29
Appendix Table 3: 2015 New England Winter Capacity (MW, %)(a. b) ........................................................................ 30
Appendix Table 4: ISO New England System Annual Emissions of NOX, SO2, and CO2, 2001 to 2015 (ktons) ......... 30
Appendix Table 5: 2015 Monthly System Emission Rates of NOX, SO2, and CO2 (lb/MWh) ...................................... 31
Appendix Table 6: New England System Annual Average NOX, SO2, and CO2 Emission Rates,
1999 to 2015 (lb/MWh) ............................................................................................................... 31
Appendix Table 7: LMU Marginal Heat Rate, 2009 to 2015 (MMBtu/MWh) ............................................................ 32
Appendix Table 8: 2015 LMU Marginal Emission Rates—All LMUs (lb/MMBtu) ...................................................... 32
Appendix Table 9: 2015 Monthly LMU Marginal Emission Rates—All LMUs (lb/MWh) ........................................... 32
Appendix Table 10: 2015 LMU Marginal Emission Rates—Emitting LMUs (lb/MMBtu) ............................................. 33
Appendix Table 11: 2015 Monthly LMU Marginal Emission Rates—Emitting LMUs (lb/MWh) ................................. 33
Appendix Table 12: NOX LMU Marginal Emission Rates, 2009 to 2015 —All LMUs (lb/MWh) ................................... 34
Appendix Table 13: NOX LMU Marginal Emission Rates, 2009 to 2015—Emitting LMUs (lb/MWh) .......................... 34
Appendix Table 14: SO2 LMU Marginal Emission Rates, 2009 to 2015—All LMUs (lb/MWh) ..................................... 35
Appendix Table 15: SO2 LMU Marginal Emission Rates, 2009 to 2015—Emitting LMUs (lb/MWh) ........................... 35
Appendix Table 16: CO2 LMU Marginal Emission Rates, 2009 to 2015—All LMUs (lb/MWh) .................................... 36
Appendix Table 17: CO2 LMU Marginal Emission Rates, 2009 to 2015—Emitting LMUs (lb/MWh) ........................... 36
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Section 1 Executive Summary
ThisISONewEngland(ISO)ElectricGeneratorAirEmissionsReport(EmissionsReport)providesacomprehensiveanalysisofNewEnglandelectricgeneratorairemissions(nitrogenoxides[NOX],sulfurdioxide[SO2],andcarbondioxide[CO2])andareviewofrelevantsystemconditions.Themainfactorsanalyzedareasfollows:
Systemandmarginalemissions(kilotons[ktons])1
Systemandmarginalemissionrates(poundspermegawatt‐hour[lb/MWh]andpoundspermillionBritishthermalunit[lb/MMBtu])
Systemandmarginalheatrate(MMBtu/MWh)
Thereportpresentsinformationfordifferenttimeperiodsofinterest:
On‐peakcomparedwithoff‐peakhours
Ozoneseasoncomparedwithnon‐ozoneseason
Monthlyvariations
Highelectricdemanddays(HEDDs)
TheEmissionsReport,firstdevelopedin1993,hasevolvedinresponsetostakeholderneeds.ItwasinitiallymotivatedbytheneedtodeterminethereductionsofNewEngland’saggregateNOX,SO2,andCO2generatingunitairemissionsresultingfromdemand‐sidemanagement(DSM)programs.Theuseoftheseemissionrateswassubsequentlybroadenedtoreflecttheemission‐reductionbenefitsofenergy‐efficiencyprogramsandrenewableresourceprojectswithintheregion.
Duringtheten‐yearperiodfrom2006through2015,totalsystememissionshavedecreasedoverall:NOXby56%,SO2by91%,andCO2by22%.Thedeclineinemissionsduringthisperiodreflectsshiftsintheregionalfuelmix,withincreasingnaturalgasgenerationoffsettingdecreasesincoal‐andoil‐firedgeneration(seeFigure1‐1).
1Themassvalueof“tons”isequivalenttoaUSshortton,or2,000lb,and“ktons”isequivalentto2,000,000lb.
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Figure 1‐1: Percentage energy generation by fuel type, 2006 compared with 2015.
Comparedwiththe20‐yearaverageforheatingandcoolingdays(i.e.,anindicatorofweather),2015hada6%warmersummerandanaveragewinter.From2014to2015,therewaslittlechangeinthenetenergyforloadorsystemgeneration,whichdecreasedby0.2%and0.4%,respectively.TheamountofenergythatNewEnglandreceivedfromneighboringareasin2015wasalsoapproximatelythesameasthepreviousyear.Theenergygenerationbynon‐emittinggenerators(notincludingbehind‐the‐metergenerators)(e.g.,pumpedstoragehydroelectricgeneration,nuclear,andwindandsolarrenewables)decreasedfrom44%to39%ofthetotal.Additionally,coal‐firedgenerationdecreased23%andnaturalgas‐firedgenerationincreased12%from2014to2015.
Table1‐1showsthetotal2014and2015NewEnglandsystememissions(ktons)andaveragesystememissionrates(lb/MWh)ofNOX,SO2andCO2.EmissionratesdecreasedforNOXandSO2,andincreasedforCO2from2014to2015.
Table 1‐1 2014 and 2015 New England System Emissions (ktons)
and Emission Rates (lb/MWh)
Annual System Emissions
2014
Emissions (kTons)
2015 Emissions
(kTons)
Total Emissions % Change
2014 Emission Rate (lb/MWh)
2015Emission Rate (lb/MWh)
Emission Rate
% Change
NOX 20.49 18.86 -8.0 0.38 0.35 -7.9
SO2 11.68 9.11 -21.9 0.22 0.17 -22.7
CO2 39,317 40,312 2.5 726 747 2.9
Table1‐2showsthe2014and2015annualaveragemarginalemissionratesascalculatedbythelocationalmarginalunit(LMU)marginalemissionanalysis.ThisanalysisusestheemissionratesfromtheISO’sidentifiedmarginalunit(s)thatsettheenergymarkethourlylocationalmarginal
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
2006 2015
Sources of Energy
Wind
Other Renewables
Pumped Storage
Hydro
Coal
Nuclear
Oil
Natural Gas
39%
29%30%
48%
15% 4%
4%
6%
7%6%
6%
2%
2%
1%
1%
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price(s)(LMP).TheLMPresultsfromeconomicdispatch,whichminimizestotalenergycostsfortheentireNewEnglandregion,subjecttoasetofconstraintsreflectingphysicallimitationsofthepowersystem.Thisreportpresentstheresultsfortwoscenariosofemissionratescalculatedusingthismethodology:1)allLMUs;and2)emittingLMUs.
Table 1‐2 2014 and 2015 Average LMU Marginal Emission Rates (lb/MWh)
LMU Marginal Emissions
All LMUs Emitting LMUs
2014 Annual
Rate (lb/MWh)
2015 Annual Rate
(lb/MWh)
Percent Change 2014 to 2015 (%)
2014 Annual Rate
(lb/MWh)
2015 Annual Rate
(lb/MWh)
Percent Change 2014 to 2015 (%)
NOX 0.38 0.28 -26.2 0.47 0.36 -24.0
SO2 0.45 0.33 -25.8 0.55 0.41 -25.2
CO2 941 857 -9.0 1,107 1,036 -6.4
Figure1‐2summarizesthe2015emissionratesinNewEngland.Theall‐LMUandemitting‐LMUmarginalemissionratesforthetop‐fivehighelectricdemanddays(HEDDs)characterizetheemissionsprofilesofthemarginalunitsrespondingtosystemdemandduringthesedays.OnthoseHEDDdays,thepercentageofcoalandoilunitsonthemarginwassignificantlyhigherthanonaverageduringtheyear.
Figure 1‐2: Comparison of 2015 New England emission rates (lb/MWh).
Agenerator’sheatrate(MMBtu/MWh)isameasurementofitsefficiencyinconvertingfuelintoelectricity.The2015calculatedall‐LMUmarginalheatrateof6.707MMBtu/MWhwas13%lowerthanthe2014valueof7.692MMBtu/MWh.Whenconsideringtheemittingunitsonly,theLMUmarginalheatratedecreased10%,from9.034MMBtu/MWhin2014to8.096MMBtu/MWhin2015.
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Section 2 Background
In1994,theNewEnglandPowerPool(NEPOOL)EnvironmentalPlanningCommittee(EPC)analyzedtheimpactthatdemand‐sidemanagement(DSM)programshadon1992nitrogenoxide(NOX)airemissionsofNEPOOLgeneratingunits.Theresultswerepresentedinareport,1992MarginalNOXEmissionRateAnalysis.ThisreportwasusedtosupportapplicationstoobtainNOXEmission‐ReductionCredits(ERC)inMassachusettsresultingfromtheimpactsofDSMprograms.2SuchapplicationswerefiledundertheMassachusettsERCbankingandtradingprogram,whichbecameeffectiveonJanuary1,1994.TheERCprogramallowsinventoriedsourcesofNOX,volatileorganiccompounds(VOC),andcarbonmonoxide(CO)inMassachusettstoearnbankableandtradableemissioncreditsbyreducingactualpowerplantemissionsbelowregulatoryrequirements.
Alsoin1994,the1993MarginalEmissionRateAnalysis(1993MEAReport)waspublished,whichprovidedexpandedanalysisoftheimpactofDSMprogramsonpowerplantNOX,sulfurdioxide(SO2),andcarbondioxide(CO2)airemissionsfor1993.MEAreportswerepublishedannuallyfrom1994to2007toprovidesimilarannualenvironmentalanalysesfortheseyears.3Forthe2008emissionsanalysis,membersofISONewEngland’sEnvironmentalAdvisoryGroup(EAG)requestedthattheMEAReportberestructuredtoincludecalculatedsystemandmarginalemissionsfortheentireISONewEnglandgenerationsystem,ratherthanfocusingprimarilyonmarginalemissions.4TherevisedreportwasrenamedtheISONewEnglandElectricGeneratorAirEmissionsReport(EmissionsReport),toreflecttheimportanceofemissionsfromtheentireNewEnglandelectricgenerationsystem.
TheEmissionsReportincludesamarginalemissionsanalysisthatisbasedontheLocationalMarginalUnit(LMU)methodology.Thismethodology,whichwasbegunasapilotprogramin2011,usesmarginalunitsidentifiedbytheLocationalMarginalPrice(LMP)tocalculatethemarginalemissionsforLMUs.
StakeholderscanusethecalculatedmarginalemissionstotrackairemissionsfromNewEngland’selectricgenerationsystemandtoestimatetheimpactthatDSMprogramsandnon‐emittingrenewableenergyprojects(i.e.,windandsolarunits)haveonreducingNewEngland’sNOX,SO2,andCO2powerplantairemissions.The2015EmissionsReportfocusesonanalysisandobservationsoverthepastdecade(2006to2015).TheAppendixincludesdataforyearsbefore2006andvaluesforthefigurespresented.
2MassachusettsExecutiveOfficeofEnergyandEnvironmentalAffairs,“BWPAQ[BureauofWastePrevention—AirQuality]18—CreationofEmissionReductionCredits,”webpage(2016),http://www.mass.gov/eea/agencies/massdep/service/approvals/bwp‐aq‐18.html.3ISONewEnglandemissionsanalysesandreportsfrom1999tothepresentareavailableathttp://www.iso‐ne.com/system‐planning/system‐plans‐studies/emissions.4TheEAGisastakeholderworkinggroupthatassiststheISO’sPlanningAdvisoryCommittee(PAC),theReliabilityCommittee(RC),andtheassociatedPowerSupplyPlanningCommittee(PSPC);http://www.iso‐ne.com/eag.
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2.1 History of Marginal Emissions Methodologies
MEAstudiesperformedbefore2004usedproductionsimulationmodelstoreplicate,ascloselyaspossible,theactualsystemoperationsforthestudyyear(referencecase).Anincrementalloadscenariowasthenmodeledinwhichthesystemloadwasincreasedby500MWineachhour(marginalcase).Thecalculationforthemarginalairemissionrateswasbasedonthedifferencesingeneratorairemissionsbetweenthereferenceandmarginalscenarios.However,thereferencecasesimulationcouldnotexactlymatchtheactualunit‐specificenergyproductionlevelsofthestudyyearbecausetheproductionsimulationmodelhadanumberoflimitations.Forexample,themodelcouldnotaccuratelyrepresentthehistoricaloveralldynamicsoftheenergydispatch,out‐of‐meritandreliability‐baseddispatches,unit‐specificoutagesandderatings,andtheeffectsofthedailyvolatilityofregional(powerplant)fuelprices.
From2004to2013,theFuelTypeAssumed(FTA)methodologywasusedtocalculatetheaveragemarginalemissionrates.Thismethodwasbasedontheassumptionthatallnatural‐gas‐firedandoil‐firedgeneratorsrespondedtochangingsystemloadbyincreasingordecreasingtheirloading.Unitsfueledwithothersources,suchascoal,wood,biomass,refuse,orlandfillgas,wereexcludedfromthecalculation;historically(inthe2000s),thesetypesofunitsoperatedasbaseloadorwerenon‐dispatchableandnottypicallydispatchedtobalancesupplywithdemandonthesystem.5Othernon‐emittingresources,suchashydroelectric,pumpedstorage,wind,solar,andnuclearunitsthatdonotvaryinoutputtofollowloadwerealsoassumednottobemarginalunitsandwereexcludedfromtheFTAcalculationofmarginalemissionrates.
In2011,theISObegandevelopingamethodologyforcalculatingthemarginalemissionratebasedonthelocationalmarginalunit,whichstemmedfromrecommendationsoftheEnvironmentalAdvisoryGroup.Thismethodologyidentifiesmarginalunitsusingthelocationalmarginalprice(LMP),aprocessthatminimizestotalcostofenergyproductionfortheentireNewEnglandregionwhileaccountingfortransmissionandotherconstraintsreflectingphysicallimitationsofthepowersystem.Thismethodidentifiesthelastunitdispatchedtobalancethesystem,calledthelocationalmarginalunit(refertoSection3.3).Resultsarepresentedstartingin2009,theearliestyearofavailabledata.
2.2 History of Heat Rate Methodologies
Athermalpowerplant’sheatrateisameasureofitsefficiencyinconvertingfuel(Britishthermalunits,Btus)toelectricity(kWh);thelowertheheatrate,themoreefficientthefacility.Aplant’sheatratedependsontheindividualplantdesign,itsoperatingconditions,anditslevelofelectricalpoweroutput.
Before1999,MEAstudiesassumedafixedmarginalheatrateof10.0millionBTUspermegawatt‐hour(MMBtu/MWh),whichwasusedtoconvertfrompounds(lb)/MWhtolb/MMBtu.6Inthe1999to2003MEAstudies,themarginalheatratewascalculatedusingtheresultsofproduction
5Oneobservationfordeterminingwhethertoconsidercoalunitsasmarginalunitswasthathigherorlowerloadschangethenumberofcommittednaturalgasandoilunits,whilecoalunitswouldbedispatchedwhenavailable.Duringthelow‐loadtroughsofthedailycycle,coalunitswereloadfollowing.Itisreasonabletoexpectthatthecoalunitswouldcontinuetobeavailableforloadfollowingduringsuchlow‐loadperiodsofthenightandwouldlikelycontinuetobemarginalforestablishingLMPsduringtheseoff‐peakhours.610MMBtu/MWhisequivalentto10,000,000Btu/kWh.
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simulationruns.Beginningwiththe2004MEAstudy,themarginalheatratewasbasedontheactualgenerationofmarginalfossilunitsonly.
Beginningwiththe2007MEAReport,themarginalheatratehasbeencalculatedusingacombinationofbothUSEnvironmentalProtectionAgency(EPA)heatinputdataandtheheat‐rateinformationcollectedandmaintainedbytheISO.ForthemarginalfossilunitswithEPAdata,theheatinputsreportedtoEPAwereused.ForunitswithoutEPAdata,theheatinputswerecalculatedbymultiplyingeachunit’smonthlygenerationbytheISO’sheat‐ratedata.Theindividualheatinputvalues(inMMBtu)usingthetwomethodswerethenaddedandthesumdividedbythetotalgenerationofthemarginalfossilunits.
Inthecurrentmethodology(seeSection3.4),thecalculationforthemarginalheatrateisbasedontheheatratesforeachindividualLMU.Thepercentageoftimeeachgeneratorismarginalperyearleadstothecontributionofthatunit’sheatratetotheLMUmarginalheatrate.
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Section 3 Data Sources and Methodologies
Thissectiondiscussesthedatasourcesandmethodologiesusedfortheemissionsanalysis.Thecalculationsfortotalsystememissionrate,marginalemissionrate,andmarginalheatrateareshown.Thetimeperiodsstudiedarealsodescribed.
3.1 Data Sources
TheNewEnglandpowersystememissionsandmarginalemissionratecalculationsforNOx,SO2,andCO2wereprimarilybasedonthe2015actualairemissions(tons)reportedbygeneratorstotheUSEPACleanAirMarketsDivision(CAMD)database7underEPA’sAcidRainProgramandNOXCleanAirInterstateRule(CAIR)andtheRegionalGreenhouseGasInitiative(RGGI).8
ForthoseunitsnotrequiredtofileemissionsdataundertheAcidRainProgram,CAIR,orRGGI,monthlyemissionrates(lb/MWh)fromtheNewEnglandPowerPoolGenerationInformationSystem(NEPOOLGIS)wereused.Ifthisinformationwasnotavailable,annualemissionrates(lb/MWh)fromEPA’seGRID2012wereused.9Inthecaseofnoothersourcesofdata,emissionratesbasedoneGRIDdatawereobtainedforsimilartypeunits.Theseunit‐specificemissionrateswereusedinconjunctionwiththeactualmegawatt‐hoursofgeneration,fromtheISO’sdatabaseusedforenergymarketsettlementpurposes,tocalculatetonsofemissions.
AllelectricgeneratorsdispatchedbyISONewEnglandareincludedintheemissionscalculations.Emissionsfrom“behind‐the‐meter”generatorsorthosegeneratorsnotwithintheISONewEnglandbalancingauthorityareaarenotpartofthisanalysis.
3.2 Total System Emission Rate Calculation
ThetotalannualsystememissionrateisbasedontheemissionsproducedbyallISONewEnglandgeneratorsduringacalendaryear.Theratesarecalculatedbydividingthetotalairemissionsbythetotalgenerationfromallunits.Theformulaforcalculatingthetotalannualsystememissionrateis:
AnnualSystemEmissionRate lb MWh TotalAnnualEmissions lb AllGenerators
TotalAnnualEnergy MWh AllGenerators
7EPA’sCleanAirMarketsProgramdata(2016)areavailableathttp://ampd.epa.gov/ampd/,andtheCleanAirMarketsemissionsdata(2015)areavailableathttp://www.epa.gov/airmarkets/.GeneratorsreportemissionstoEPAundertheAcidRainProgram,whichcoversgenerators25MWorlarger,aswellasCAIR,whichincludesgenerators15MWorlargerintheaffectedstatesofConnecticutandMassachusetts(thepredecessorsofCAIRwerethe1999‐2002OzoneTransportCommissionNOxBudgetProgram,andEPA’s2003‐2008NOXBudgetTradingProgram).GeneratorssubjecttoRGGIalsoreportCO2emissionstoEPA.8Before2005,theMEAreportsusedannualdataobtainedprimarilyfromtheEPAEmissionsScorecard.Inthe2005and2006MEAReports,monthlyEPAdata,ratherthanhourlydata,wereusedforcalculatingmarginalrates.9TheU.S.EPA’seGRID2012database(2016)isavailableathttp://www.epa.gov/cleanenergy/energy‐resources/egrid/index.html.
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3.3 Marginal Emission Rate Calculation
Thecostofthegenerationdispatchedtomeetthenextincrementofloadatapricinglocationiscalledthemarginalunit,whichsetsthelocationalmarginalprice.LMPsminimizetotalenergycostsfortheentireNewEnglandregion,subjecttoasetofconstraintsreflectingphysicallimitationsofthepowersystem.
TheprocesstodeterminetheLMPidentifiesatleastonelocationalmarginalunitforeachfive‐minuteperiod,whichisassociatedwithmeetingtheenergyrequirementsonthesystemduringthatpricinginterval.Whentransmissionisnotconstrained,themarginalunitisclassifiedastheunconstrainedmarginalunit.Eachbindingtransmissionconstraintaddsanadditionalmarginalunit,resultinginn+1marginalunits(LMUs)foreverynbindingconstraint,ineachfive‐minuteperiod.Tocalculatethemarginalemissionrates,thehourlyemissions(lb)forthoseunitsintheEPACAMDdatabaseweregroupedintoon‐peakandoff‐peakperiods(definedinSection3.5)foreachmonth.WhenonlymonthlyNEPOOLGISorannualeGRIDdatawereavailable,theseemissionratesweremultipliedbytheassociatedmonthlyon‐peakandoff‐peakgeneration.Theamountofmonthlyemissions(lb)fromeachindividualmarginalfossilgeneratorwasthendividedbythatgenerator’smonthlyon‐peakoroff‐peakgenerationtogetthecorrespondingemissionrate(lb/MWh)forthattimeperiod.ForNOXemissionrates,themonthlytotals(lb)foreachgeneratorweregroupedintoozoneandnon‐ozoneseasonemissionsanddividedbytherespectiveozoneandnon‐ozoneseasongeneration.
Thepercentageoftimeeachgeneratorwasmarginalineachmonthwascalculatedandthenmultipliedbythegenerator’smonth‐specificon‐peakoroff‐peakaverageemissionsratedescribedabove.Thatamountwassummedforeachmarginalunitandthendividedbythetotalon‐peakoroff‐peakhoursintheyear.TheLMUmarginalemissionratecalculationsareasfollows,wheregeneratorkisidentifiedtobemarginalduringhourhandhasaspecificmonthlyemissionrateduringmonthm:
LMUOn‐PeakMarginalEmissionRate
∑ ∑ %ofLMPUnitMarginalk,h On‐PeakEmissionRatek,m on‐peakhoursinyear
h 1LMPmarginalunitsk 1
On‐PeakHoursinYear
LMUOff‐PeakMarginalEmissionRate
∑ ∑ %ofLMPUnitMarginalk,h Off‐PeakEmissionRatek,m off‐peakhoursinyear
h 1LMPmarginalunitsk 1
Off‐PeakHoursinYear
TheannualLMUmarginalemissionratewasthencalculatedbycombiningtheon‐peakandoff‐peakratesinaweightedcalculation.
TheanalysisofLMUmarginalemissionrateswasconductedfortwodifferentscenarios.Eachscenarioincludesorexcludescertaingeneratorsdependingontheircharacteristics.Thetwoscenariosareasfollows:
AllLMUs—includesalllocationalmarginalunitsidentifiedbytheLMP
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EmittingLMUs—excludesallnon‐emittingunitswithnoassociatedairemissions,suchaspumpedstorage,hydroelectricgeneration,nuclear,externaltransactions,andwindandsolarrenewables
3.4 Marginal Heat Rate Calculation
Themarginalheatratewascalculatedbyfirstcalculatingaheatrateforeachindividualgenerator.TheheatinputvaluesfortheindividualLMUswerethenmultipliedbythepercentageoftimeeachgeneratorwasmarginalduringtheyear.Thesevalueswerethenaddedtogetheranddividedbythetotalgenerationofthemarginalunits.
Sinceaunit’sheatrateisequaltoitsheatinput,orfuelconsumption,dividedbyitsgeneration,thecalculatedmarginalheatrateisdefinedasfollows:
CalculatedMarginalHeatRate CalculatedFuelConsumptionof Units MBtu
ActualGenerationofMarginalFossilUnits MWh
3.5 Time Periods Analyzed
The2015marginalairemissionratesforon‐andoff‐peakperiodsforNewEnglandwerecalculatedforthisreport.Datafortheon‐peakperiodarepresentedsothatatypicalindustrialandcommercialuserthatcanprovideloadresponseduringatraditionalweekdaycanexplicitlyaccountforitsemissionsreductionsduringtheon‐peakhours.ThemarginalemissionratesforNOXwerecalculatedforfivetimeperiods:10
On‐peakozoneseason,consistingofallweekdaysbetween8:00a.m.and10:00p.m.fromMay1toSeptember30
Off‐peakozoneseason,consistingofallweekdaysbetween10:00p.m.and8:00a.m.andallweekendhoursfromMay1toSeptember30
On‐peaknon‐ozoneseason,consistingofallweekdaysbetween8:00a.m.and10:00p.m.fromJanuary1toApril30andfromOctober1toDecember31
Off‐peaknon‐ozoneseason,consistingofallweekdaysbetween10:00p.m.and8:00a.m.andallweekendhoursfromJanuary1toApril30andfromOctober1toDecember31
Annualaverage
Becausetheozoneandnon‐ozoneseasonsareonlyrelevanttoNOXemissions,theSO2andCO2emissionrateswereonlycalculatedforthefollowingtimeperiods:
On‐peakannual,consistingofallweekdaysbetween8:00a.m.and10:00p.m.
Off‐peakannual,consistingofallweekdaysbetween10:00p.m.and8:00a.m.andallweekendhours
Annualaverage
10TheISOdevelopedaspecialreport,AnalysisofNewEnglandElectricGenerators’NOXEmissionson25Peak‐LoadDaysin2005–2009,releasedSeptember23,2011,whichsummarizeditsanalysisofNOXemissionsduringpeakdays(http://www.iso‐ne.com/genrtion_resrcs/reports/emission/peak_nox_analysis.pdf).
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Section 4 Data and Assumptions
Thissectionhighlightsthekeyparametersandassumptionsmodeledinthe2015ISONewEnglandEmissionsReport,includingweather,emissionsdata,installedcapacity,andsystemgeneration.
4.1 2015 New England Weather
Becausetheweathersignificantlyaffectsthedemandforenergyandpeakloads,comparing2015temperatures,totalenergyuseandbothcoolingandheatingdegreedaystopreviousyearscanprovidesomeperspective.
TemperaturesinJanuarywereaboutaverage,butFebruary2015,withanaveragemonthlytemperatureof16.9°FinNewEngland,wasthecoldestmonthonrecord,basedonISONewEnglandhistoricalstatisticsdatingbackto1960.Incontrast,the2015summerwasrelativelymild,andthetemperaturesinDecemberwereaboveaverage.
The2015summerpeakelectricitydemandof24,437MWwasessentiallythesameasthe2014summerpeakof24,443MW.Therewere337coolingdegreedaysin2015,whichis7%higherthanthe20‐yearaverage.11Thenetenergyforloadwas0.2%lowerin2015than2014.Withrespecttothewintermonths,therewere6,100heatingdegreedays,whichis0.7%higherthanthe20‐yearaverage.
NewEngland’shistoricalcoolingdegreedaysandheatingdegreedaysfor1996through2015areshowninAppendixTable1.Thedifferencebetweenthecoolingandheatingdegreedaysforaparticularyearandtheaverageisalsoprovided.
4.2 Emissions Data
Forcalculatingtotalsystememissions,approximately82%oftheSO2emissionsand76%oftheCO2emissionswerebasedonEPA’sCleanAirMarketsdata.ForNOX,CleanAirMarketsdatawereusedfor46%oftotalemissions.
Theemissionratesweremultipliedbythe2015energygenerationreportedtotheISOtoobtaintheemissions(tons)byeachgenerator.
4.3 ISO New England System Installed Capacity
TheISONewEnglandpowergridoperatesasaunifiedsystemservingallloadsintheregion.Theamountofgenerationbyfueltypeanditsassociatedemissionsareaffectedbyanumberoffactors,includingthefollowing:
Forcedandscheduledmaintenanceoutagesofresourcesandtransmissionsystemelements
Fuelandemissionallowancecosts
11Overthe20‐yearspanfrom1996to2015,theaveragenumberofcoolingdegreedayswas316,andtheaveragenumberofheatingdegreedayswas6,055.
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Importsfromandexportstoneighboringregions
Systempeakloadandenergyconsumption
Wateravailabilitytohydrofacilitiesandforthermalsystemcooling
Avarietyofotherfactors
Figure4‐1showsthetotal2015summercapacityforISONewEnglandgenerationasobtainedfromISONewEngland’s2016–2025ForecastReportofCapacity,Energy,LoadsandTransmission(CELT).12AppendixTable2andAppendixTable3summarizethetotalsummerandwintercapacityforISONewEnglandgenerationbystateandfueltype.
Figure 4‐1: 2015 New England summer capacity by state (MW).
Figure4‐2illustratesthenewgeneratingcapacityaddedtotheISONewEnglandsystemfrom2006through2015.Atotalof2,626MWwasadded,withcombustionturbinesandcombined‐cycleplantscapableofburningnaturalgasordistillateoilmakingupabout60%ofthisnewcapacity.Theremainingadditionsconsistprimarilyofnuclearupratesandrenewablegeneration.
12TheISONewEnglandCELTReportistypicallyissuedinAprilofeachyear.The2016CELTReport(usingtheJanuary1,2016ratings)wasusedtocompletelycaptureallthenewcapacityadditionsthatoccurredduringthepriorcalendaryear,2015.Thecapacityalsoincludesgeneratorsthatretiredin2015.TheCELTreportsareavailableathttp://www.iso‐ne.com/system‐planning/system‐plans‐studies/celt.
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Figure 4‐2 : ISO New England generator additions, 2006 to 2015 (MW). Note: The generator additions and uprate values are based on the Seasonal Claimed Capabilities, as reported in the 2016 CELT Report.
SeveralrecentlargegeneratorsinNewEnglandhaveretiredinrecentyears.Theretirements,asshowninFigure4‐3,total1,050MWofcoal,567MWofresidualoil,and604MWofnuclear‐firedgenerationsincelate2011.
Figure 4‐3: Major retirements in ISO New England, 2006 to 2015 (MW). Note: The retirement date shown is not necessarily the year in which the retirement occurred. In the case of units that retired late in the year, the retirement is included in the following year because this is when the impact would primarily have been observed.
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4.4 ISO New England System Energy Production
TheISOreliesongeneratingunitsofalloperatingcharacteristicsandfueltypes,andagenerator’sfueltypedirectlycorrelateswiththemagnitudeandcharacteristicsoftheunit’semissions.
Figure4‐4showsthe2015monthlygenerationbyfueltype.Theoverlaidblacklinerepresentsthetotalgenerationineachmonthandcorrespondswiththerightaxis.Throughouttheyear,natural‐gas‐firedgenerationaccountsfor29%to60%ofthetotalgeneration.Inthepastfewyearsingeneral,theoveralllowerpricesofnaturalgas,combinedwiththeuseofhighlyefficientgeneratingunits,haveledtothegrowingcontributionofnaturalgastogenerateelectricenergyinNewEngland.However,duringmonthswithhigherenergydemandandcoupledwithlimitationsinnaturalgasavailability,otherfueltypeshaveincreasedtheircontributiontosupporttheNewEnglandsystem.Duringthewintermonths,theuseofnaturalgassuppliesandtransportationbytheregionalgassector’sfirmlocaldistributioncompany(LDC)customerstakepriorityovertheuseofgastogenerateelectricity.13Manynatural‐gas‐firedgeneratingunitslackbothfirmsupplyandtransportationcontracts.
Thelowestmonthlypercentagesofnatural‐gas‐firedgenerationin2015wereinJanuary,February,andMarch.Correspondingly,thesearealsothemonthsduringwhichcoal‐andoil‐firedgenerationhadalargercontribution.Oilpricesin2015wereapproximatelyhalfofwhattheywerethepreviouswinter,whichdramaticallyreducedthecostofoperatingoil‐firedpowerplants.Whilenuclearandnaturalgaswerethedominantfuelsusedtoproducepowerinwinter2014/2015,oilandcoalresourceswerecompetitivelypricedand,attimes,werealargepartofthefuelmix.ThiswasespeciallytrueduringFebruary,thecoldestmonth.
Hydroelectricandwindgenerationexhibitseasonaldifferencesintheirgenerationduetofuelavailability;thereislessrain(water)andonshorewindduringthesummermonths.
Figure 4‐4: 2015 ISO New England monthly generation by fuel type (% MWh, MWh).
13FirmcustomersofregionalgasLDCsincluderesidential,commercial,andindustrial(RCI)customers.
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Figure4‐5showsthegeneration(MWh)byfueltypefrom2011to2015basedontheresource’sprimaryfueltypelistedinthe2016CELTReport.In2015,coal‐firedgenerationwasabout1,171GWhlowerthanin2014,whileoil‐firedgenerationwas174GWhhigher.Thedecreaseincoal‐firedgenerationfrom2014to2015isconsistentwiththeapproximately270MWofcoalcapacitythatretiredin2014(Figure4‐3).Natural‐gas‐firedgenerationincreasedbyabout5,750GWh,orabout12%from2014to2015.Theoverallsystemgenerationof107,917GWhin2015wasjustslightlybelowthe2014level(by439GWh).
Figure 4‐5: ISO New England annual generation by fuel type, 2011 to 2015 (million MWh).
4.5 Locational Marginal Unit Scenarios
Thedataandassumptionsappliedfortheall‐LMUandemitting‐LMUscenariosarepresentedinthissection,includingthepercentageoftimevariousfueltypesweremarginal.Becausethepriceofthemarginalunit(andthusthepriceofelectricity)islargelydeterminedbytheunit’sfueltypeandheatrate,examiningthemarginalunitsbyfueltypecanexplainchangesinelectricityprices.
4.5.1 All LMUs
Inthisscenario,allidentifiedlocationalmarginalunitswereusedtodevelopthemarginalemissionrates.Non‐emittinggeneratorswereassociatedwithazeroemissionrate.Figure4‐6showseachfueltype’stimeonthemarginandmonth‐to‐monthvariations.Naturalgasismarginal39%to85%ofthetime.MorenaturalgasunitswereoninthemarginfromAprilthroughtheendoftheyear,inthe78%to85%range,whilefewerwereoninthemarginfromJanuarythroughMarch,atalowerrangeof39%to68%.DuringJanuaryandMarch,coal‐firedgenerationwasonthemarginmorethanothermonths,at13%and9%,respectively.Oil‐firedgenerationwasalsoonthemarginmoreinthefirsttwomonthsoftheyearthanduringtherestoftheyear.However,Februaryinparticularstoodout,withoilunitsonthemargin38%ofthetimeduringthatmonth.
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Figure 4‐6: 2015 percentage of time various fuel types were marginal—all LMUs.
Figure4‐7showsthehistoricalpercentageoftimethateachfueltypewasmarginalwithinacalendaryear.Naturalgashasbeentheprimarymarginalfueltypeinthepastfiveyears.From2014to2015,thepercentageoftimethatnaturalgaswasmarginalincreased,whilethetimethatcoalwasthemarginalfueldecreasedbymorethanhalf.Oilwasthemarginalfuelapproximatelythesameamountoftimeinbothyears.
Figure 4‐7: Annual percentage of time various fuel types were marginal—all LMUs, 2011 to 2015.
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% of Time M
arginal
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2015
2011: 0.06%2012: 0.04%2013: 0.10%2014: 0.04%2015: 0.07%
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4.5.2 Emitting LMUs
Marginalgeneratingresourceswithnoairemissionswereexcludedinthisscenario.Therefore,hydro,pumpedstorage,externaltransactions,andotherrenewableswithnoairemissionswerenottakenintoaccount,whileallotherLMUswere.
Figure 4‐8: 2015 percentage of time various fuel types were marginal—emitting LMUs.
Figure 4‐9: Annual percentage of time various fuel types were marginal—emitting LMUs, 2011 to 2015.
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4.6 High Electric Demand Days
InNewEngland,highelectricdemanddays(HEDDs)aretypicallycharacterizedwithhightemperaturesleadingtoelevatedcooling(energy)demand.Duringpeakenergydemandperiods,suchasHEDDs,theISOreliesonpeakingunits,whicharelessutilizedduringtherestoftheyearbutrespondquicklytomeetsystemdemand.Thesepeakingunitsareoftenjet(aero‐derivative)orcombustionturbineswithhigheremissionrates.Therefore,examiningthemarginalemissionratesonHEDDsshowstheunitsrespondingtosystemdemandandtheassociatedemissionrate.
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Section 5 Results and Observations
ThissectionpresentstheresultsforISONewEngland’s2015systememissionsrepresentingallgenerators.Italsoprovidestheresultsfortheannualmarginalheatratesandthelocationalmarginalunitemissionratesfortheall‐LMUandemitting‐LMUscenarios.
5.1 2015 New England System Emissions
Resultsarepresentedforthefollowingmetrics:
AggregateNOX,SO2,andCO2emissionsforeachstatefor2015
AcomparisonofaggregateNOX,SO2,andCO2emissionsfor2006to2015
2015annualaverageNOX,SO2,andCO2emissionrates,bystateandforNewEngland
Monthlyvariationsintheemissionratesfor2015
AcomparisonofannualaverageNOX,SO2,andCO2emissionratesfor2006to2015
5.1.1 Results
Figure5‐1showstheannualaggregate2015NOX,SO2,andCO2airemissionsforeachstate.TheNewEnglandsystemtotalemissionsforNOX,SO2,andCO2were18.86ktons,9.11ktons,and40,312ktons,respectively.ThecalculationsfortheseemissionlevelswerebasedontheactualgenerationofallgeneratingunitsinISONewEngland’sbalancingauthorityareaandtheactualorassumedunit‐specificemissionrates.14Thereasonforthedivergenttotalemissionsforeachstateisthattheemissionsarebasedonthephysicallocationsofthegeneratingunitsineachstate(refertoFigure4‐1showingsummercapacitybystate).BecauseISONewEnglandoperatestheNewEnglandpowersystemasoneunifiedgrid,itdispatchesaunitphysicallylocatedinonestatetoservetheentiresystem,notonlytheunit’sownstate.
14ThisdoesnotincludenorthernMaineandtheCitizensBlockLoad(inNorthernVermont),whichistypicallyservedbyNewBrunswickandQuebec.TheseareasarenotelectricallyconnectedtotheISONewEnglandControlArea.
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Figure 5‐1: 2015 New England system annual emissions of NOX, SO2, and CO2 (ktons). Note: Sum may not equal New England system total due to rounding.
Figure5‐2showstheannualaggregateNOX,SO2,andCO2airemissionsfor2006through2015.Since2006,NOXemissionshavedroppedby56%andSO2by91%,whileCO2hasdecreasedbyabout22%.RefertoAppendixTable4forhistoricalsystememissionsbyktons.
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X, SO2, C
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Figure 5‐2: New England system annual emissions of NOX, SO2, and CO2, 2006 to 2015 (ktons).
Table5‐1showsthe2015annualaverageNOX,SO2,andCO2airemissionrates(lb/MWh),bystateandforNewEngland.TheratecalculationswerebasedontheactualhourlyunitgenerationofISONewEnglandgeneratingunitslocatedwithineachstateandtheactualorassumedunit‐specificemissionrates.
Table 5‐1 2015 New England System
Annual Average NOX, SO2, and CO2 Emission Rates (lb/MWh)
State NOx SO2 CO2
Connecticut 0.25 0.08 576
Maine 0.49 0.51 808
Massachusetts 0.48 0.21 934
New Hampshire 0.30 0.19 649
Rhode Island 0.18 0.01 965
Vermont 0.31 0.03 708
New England 0.35 0.17 747
MonthlyvariationsintheemissionratesshowninFigure5‐3reflectthedifferentsystemfuelmixesshowninFigure4‐4.In2015,emissionrateswereatahighermagnitudeduringJanuary,February,andMarch,whichhadlowernaturalgasgenerationandhighercoal‐andoil‐firedgeneration.AppendixTable5showsthevaluesforthisfigure.
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Figure 5‐3: 2015 New England system monthly average NOX, SO2, and CO2 emission rates (lb/MWh).
Figure5‐4illustratestheannualaverageNOX,SO2,andCO2airemissionrates(lb/MWh)for2006to2015usingthecalculationpresentedinSection3.2.Since2006,theannualaverageNOXemissionratehasdecreasedby48%,SO2by89%,andCO2by8%.AppendixTable6showsallhistoricalemissionrates.
Figure 5‐4: New England system annual average NOX, SO2, and CO2 emission rates, 2006 to 2015 (lb/MWh).
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5.1.2 Additional Observations
Althoughtotalenergygenerationdeclinedbylessthan1%in2015from2014,therewasasignificantshiftinthepercentageofenergygeneratedbyemittingversusnon‐emittinggenerators.In2014,non‐emittingresourcesproduced44.1%oftheenergy,butthatpercentagedecreasedto39.5%in2015.Thatchangeisprimarilyduetotheretirementofnuclear‐firedgeneration.Naturalgas‐firedgenerationwassignificantlyhigherin2015thanin2014,whileoil‐firedgenerationincreasedslightly.Therewasasignificantdecreaseincoal‐firedgenerationin2015,alsoduetoretirements.TheimpactsonsystememissionsresultingfromthesechangesinthegenerationmixcanbeseeninTable5‐2.The23%reductionincoal‐firedgenerationfrom2014to2015contributedtodecreasesof21.9%and8.0%insystememissionsforSO2andNOX,respectively.TotalCO2systememissionsincreasedby2.5%.Thechangesinemissionratesmirrorthechangesintotalemissions:the2015NOXandSO2emissionratesdecreasedby7.9%and22.7%,respectively,from2014values,whiletheCO2systememissionratesfor2015werehigherthanin2014,increasingby2.9%.
Table 5‐2 2014 and 2015 New England System Emissions (ktons)
and Emission Rates (lb/MWh)
Annual System Emissions
2014
Emissions (kTons)
2015 Emissions
(kTons)
Total Emissions %
Change
2014 Emission
Rate (lb/MWh)
2015 Emission
Rate (lb/MWh)
Emission Rate
% Change
NOX 20.49 18.86 -8.0 0.38 0.35 -7.9
SO2 11.68 9.11 -21.9 0.22 0.17 -22.7
CO2 39,317 40,312 2.5 726 747 2.9
Overall,totalsystememissionshavedeclinedoverthelast10years,whichcanbeattributedtoseveralfactors:
Increaseduseofhighlyefficientnatural‐gas‐firedgenerators
Declineinthecostofnaturalgas
Useoflower‐sulfurfuels
Retirementofoilandcoal‐firedgeneration,andretrofitsofNOXandSO2emissioncontrolsonsomeoftheremainingoil‐andcoal‐firedgenerators
5.2 2015 New England Marginal Heat Rate
Thecalculatedannualmarginalheatratereflectstheaverageannualefficiencyofallthemarginalfossilunitsdispatchedthroughout2015.The2015monthlymarginalheatratesforboththeall‐LMUandemitting‐LMUscenariosareshowninFigure5‐5,andthehistoricalmarginalheatratesfor2009to2015arepresentedinFigure5‐6.ThevaluesbehindFigure5‐6areprovidedinAppendixTable7.
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Figure 5‐5: 2015 LMU monthly marginal heat rate (MMBtu/MWh).
Figure 5‐6: LMU annual marginal heat rate, 2009‐2015 (MMBtu/MWh).
Marginalheatratesdeclinedthrough2012butincreasedin2013andthenagainin2014.In2015,themarginalheatratefortheemittingLMUsdecreasedtobelowthe2013level.Thisislikelyduetotheincreasedamountoftimethatgasunitsweremarginalandthedecreasedtimethatcoalunitswereonthemargin.
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5.3 2015 New England Marginal Emission Rates
Thissectionpresentsthe2015calculatedLMU‐basedmarginalemissionratesfortheall‐LMUandemitting‐LMUscenarios,asdefinedinSection4.5.
TheNOXdataforboththesescenariosareprovidedforeachofthefivetimeperiodsstudied.Sincetheozoneandnon‐ozoneseasonsarenotrelevanttoSO2andCO2,onlytheon‐peak,off‐peak,andannualratesareprovidedfortheseemissions.
5.3.1 Marginal Emission Rates for the All‐LMU Scenario
Theall‐LMUmarginalemissionrateswerecalculatedwithallLMUs(unitstheLMPidentifiedasmarginal).Table5‐3showstheratesinlb/MWh.AppendixTable8showstheseratesinlb/MMBtu,withtheassociatedmarginalheatrateof6.707MMBtu/MWhusedastheconversionfactor.ItishelpfultocompareFigure5‐7,whichshowsthemonthlyLMUmarginalemissionrates,withFigure4‐6(showingthe2015percentageoftimevariousfueltypesweremarginalforallLMUs)andFigure5‐3(showingthe2015NewEnglandsystemmonthlyaverageNOX,SO2,andCO2emissionrates).AppendixTable9liststhevaluesbehindFigure5‐7.
Table 5‐3 2015 LMU Marginal Emission Rates—All LMUs (lb/MWh)(a, b)
Ozone / Non-Ozone Season Emissions (NOx)
Air Emission
Ozone Season Non-Ozone Season Annual Average
(All Hours) On-Peak Off-Peak On-Peak Off-Peak
NOX 0.34 0.16 0.32 0.32 0.28
Annual Emissions (SO2 and CO2)
Air Emission
Annual Annual Average
(All Hours) On-Peak Off-Peak
SO2 0.40 0.29 0.33
CO2 891 832 857
(a) The ozone season occurs between May 1 and September 30, while the non‐ozone season occurs from January 1 to April 30 and from October 1 to December 31.
(b) On‐peak hours consist of all weekdays between 8:00 a.m. and 10:00 p.m. Off‐peak hours consist of all weekdays between 10:00 p.m. and 8:00 a.m. and all weekend hours.
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Figure 5‐7: 2015 monthly LMU marginal emission rates—all LMUs (lb/MWh).
5.3.2 Marginal Emission Rates for the Emitting‐LMU Scenario
Table5‐4andAppendixTable10presentthemarginalemissionratesforemittingLMUs.Themarginalheatrateforthisscenariois8.096MMBtu/MWh.ThevaluesforthemonthlyratesshowninFigure5‐8areshowninAppendixTable11.
Table 5‐4 2015 LMU Marginal Emission Rates—Emitting LMUs (lb/MWh)
Ozone / Non-Ozone Season Emissions (NOx)
Air Emission
Ozone Season Non-Ozone Season Annual Average
(All Hours)
On-Peak Off-Peak On-Peak Off-Peak
NOX 0.44 0.19 0.39 0.41 0.36
Annual Emissions (SO2 and CO2)
Air Emission
Annual Annual Average
(All Hours)
On-Peak Off-Peak
SO2 0.48 0.36 0.41
CO2 1,053 1,023 1,036
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Figure 5‐8: 2015 monthly LMU marginal emission rates—emitting LMUs (lb/MWh).
5.3.3 2009 to 2015 LMU Marginal Emission Rates
TheLMUsactivelyexhibitthechangesinNewEngland’senergyproduction.Comparedwiththeemitting‐LMUscenario,theall‐LMUscenariohaslowermarginalemissionratesbecauseitincludeszero‐air‐emissionresourcesthatlowertheaverageemissionrate.Figure5‐9andFigure5‐10summarizetheresultsforthetwoLMUscenariosformarginalemissionrates,whicharedetailedinAppendixTable12throughAppendixTable17inlb/MWh.
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Figure 5‐9: LMU marginal emission rates, 2009 to 2015—all LMUs (lb/MWh).
Figure 5‐10: LMU marginal emission rates, 2009 to 2015—emitting LMUs (lb/MWh).
5.3.4 Marginal Emission Rates for High Electric Demand Days
UsingtheLMUmethodology,thetop‐fiveenergydemanddaysin2015wereexamined.In2015,thetop‐fiveHEDDswereJuly20and29,August18,andSeptember8and9. Thetemperaturesin NewEnglandduringthesedaysrangedfrom84°to91°F.Peakdailyloadsrangedfrom24,216MWonTuesday,August18,toahighof24,437MWonMonday,July20.Table5‐5showstheaverageLMUmarginalemissionrateduringthesefivedays.
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arginal Emissions Rate (lb/M
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arginal Emissions Rate (lb/M
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CO2‐All Hours
CO2‐On Peak
CO2‐Off Peak
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Table 5‐5 High Electric Demand Day LMU Marginal Emission Rates (lb/MWh)
HEDD LMU Marginal Emission Rate (lb/MWh)
All LMUs Emitting LMUs
NOX 0.72 0.82
SO2 1.18 1.34
CO2 1,083 1,255
5.3.5 Observations
NewEngland’spowerplantairemissionsaredirectlydependentonthespecificunitsavailableanddispatchedtoserveloadforeachhouroftheyear.Therefore,seasonalemissionscanvarywidely,primarilyduetochangesineconomicandreliabilitydispatch,unitavailability,fuelpriceandconsumption,fuelswitching,transmissiontopology,andloadlevels.Theamountofimports,theuseofpumpedstorage,andsignificantgeneratoroutages,suchasanuclearunitoutage,couldalsoaffectemissions.TheLMUmarginalemissionratesreflectthedynamicsoftheNewEnglandpowersystem.
Comparedwith2009,the2015LMUSO2annualmarginalrateshavedeclinedbyapproximately77%forboththeall‐LMUandemitting‐LMUscenarios.AsillustratedinFigure5‐9andFigure5‐10,mostofthisdeclinetookplacein2012,whenthepercentageoftimethatoilandcoalunitswereonthemarginwaslowest(seeFigure4‐7andFigure4‐9).CO2andNOXLMUshaveremainedfairlysteadyduringthepastsevenyears,withthelowestannualmarginalratesalsooccurringin2012.
Inprioremissionsreports,wherelong‐termtrendsoffuel‐type‐assumed(FTA)marginalemissionrateswerecalculated,theFTAmarginalemissionratesforNOXdecreasednoticeablyin1995.Thiswasprimarilyduetotheimplementationofreasonableavailablecontroltechnology(RACT)regulationsforNOXrequiredunderTitleIofthe1990CleanAirActAmendments.Mostofthedecreaseinemissionratesthattookplacethrough2004canbeattributedtothecommercialinstallationofmanyhighlyefficient,low‐emitting,natural‐gas‐firedcombined‐cycleplantsbeforethattimeinNewEngland,aswellasadecreaseinthepriceofnaturalgas.Meetingtherequirementsofthe1999‐2002OzoneTransportCommissionNOXBudgetProgram,followedbyEPA’sNOXBudgetTradingProgram,reducedemissionsfurther.Becausefewnewnatural‐gas‐firedpowerplantshavebeenaddedsince2004,thedeclineinmarginalNOXemissionrateshastaperedoff.
In2015,theon‐peakmarginalratesforSO2andCO2,aswellasforNOXduringtheozoneseason,werehigherthantheoff‐peakrates.Thisislikelyduetotheoperationofolder,less‐efficientjetsorcombustionturbinesdispatchedtomeetpeakload.
Between2014and2015,theSO2andNOXmarginalemissionratesdecreasedapproximately25%,whiletheCO2ratesdecreasedby9%and6%fortheall‐LMUandemittingLMUscenarios,respectively.ThedecreaseintheSO2marginalemissionrateissimilartothedecreaseinSO2systememissionrates.However,thesystememissionratesforNOXonlydecreased8%andtheCO2rateactuallyincreasedby3%.Thegreaterimpactonmarginalemissionratescanprimarilybeattributedtotheover50%decreaseincoal‐firedunitsthatweremarginalascomparedtothe23%decreaseinannualcoal‐firedgeneration.
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Section 6 Appendix
Appendix Table 1 New England Total Cooling and Heating Degree Days, 1996 to 2015
Appendix Table 2 2015 New England Summer Capacity (MW, %)(a. b)
(a) Sum may not equal total due to rounding. (b) Seasonal Claimed Capability as of January 1, 2016.
Year
Total Cooling Degree Days
Difference from
Average (%)
Total Heating Degree
Days
Difference from
Average (%)
1996 245 -22.5% 6,454 6.6%
1997 211 -33.3% 6,432 6.2%
1998 312 -1.3% 5,483 -9.4%
1999 360 13.9% 5,774 -4.6%
2000 217 -31.4% 6,399 5.7%
2001 323 2.2% 5,895 -2.6%
2002 354 12.0% 5,959 -1.6%
2003 355 12.3% 6,651 9.8%
2004 251 -20.6% 6,354 4.9%
2005 418 32.2% 6,353 4.9%
2006 335 5.9% 5,552 -8.3%
2007 288 -8.9% 6,175 2.0%
2008 281 -11.1% 6,049 -0.1%
2009 224 -29.2% 6,278 3.7%
2010 406 28.4% 5,653 -6.6%
2011 357 12.9% 5,826 -3.8%
2012 409 29.3% 5,235 -13.5%
2013 401 26.8% 6,156 1.7%
2014 240 -24.1% 6,318 4.3%
2015 337 6.6% 6,100 0.7%
Unit Type MW % MW % MW % MW % MW % MW %
Coal 383.4 4.6 1,038.1 8.3 ‐ ‐ 530.9 12.7 ‐ ‐ ‐ ‐
Natural Gas 2,847.2 34.0 6,092.8 48.6 1,584.4 50.5 1,229.2 29.5 1,846.8 98.2 ‐ ‐
Nuclear 2,087.9 24.9 677.3 5.4 ‐ ‐ 1,247.9 29.9 ‐ ‐ ‐ ‐
Oil 2,731.7 32.6 2,413.1 19.2 845.0 26.9 482.7 11.6 ‐ ‐ 131.5 28.1
Hydro 91.5 1.1 160.9 1.3 489.4 15.6 434.2 10.4 0.2 0.0 242.1 51.8
Pumped Storage 28.8 0.3 1,735.3 13.8 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐
Solar 0.9 0.0 165.8 1.3 ‐ ‐ 0.0 0.0 7.3 0.4 ‐ ‐
Wind ‐ ‐ 9.6 0.1 55.1 1.8 20.2 0.5 0.2 0.0 11.7 2.5
Other Renewables 204.0 2.4 253.0 2.0 166.4 5.3 226.6 5.4 26.4 1.4 81.9 17.5
Total 8,375.2 100.0 12,545.9 100.0 3,140.3 100.0 4,171.5 100.0 1,880.9 100.0 467.2 100.0
Connecticut Massachusetts Maine New Hampshire Rhode Island Vermont
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Appendix Table 3 2015 New England Winter Capacity (MW, %)(a. b)
(a) Sum may not equal total due to rounding. (b) Seasonal Claimed Capability as of January 1, 2016.
Appendix Table 4
ISO New England System Annual Emissions of NOX, SO2, and CO2, 2001 to 2015 (kilotons)
(a)
(a) Since greenhouse gas data is often expressed in metric tons, an additional column showing CO2 emissions in metric
kilotons is included in this table. A metric ton is approximately 2,205 lb.
Unit Type MW % MW % MW % MW % MW % MW %
Coal 385.0 4.3 1,082.4 8.0 ‐ ‐ 534.5 12.1 ‐ ‐ ‐ ‐
Natural Gas 3,125.5 35.1 6,962.4 51.2 1,750.0 50.9 1,364.8 31.0 2,091.4 98.6 ‐ ‐
Nuclear 2,110.9 23.7 683.4 5.0 ‐ ‐ 1,246.7 28.3 ‐ ‐ ‐ ‐
Oil 2,955.1 33.2 2,643.4 19.4 876.4 25.5 502.1 11.4 ‐ ‐ 168.8 31.2
Hydro 104.6 1.2 209.5 1.5 523.1 15.2 471.7 10.7 1.6 0.1 244.5 45.1
Pumped Storage 28.1 0.3 1,733.4 12.7 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐
Solar ‐ ‐ 0.2 0.0 ‐ ‐ ‐ ‐ 0.0 0.0 ‐ ‐
Wind ‐ ‐ 23.6 0.2 114.6 3.3 55.3 1.3 0.3 0.0 44.5 8.2
Other Renewables 202.7 2.3 258.0 1.9 176.9 5.1 227.6 5.2 27.9 1.3 84.1 15.5
Total 8,911.9 100.0 13,596.4 100.0 3,441.0 100.0 4,402.7 100.0 2,121.2 100.0 542.0 100.0
Connecticut Massachusetts Maine New Hampshire Rhode Island Vermont
NOx SO2
kilotons (short)
kilotons (short)
kilotons (short)
kilotons (metric)
2001 59.73 200.01 52,991 48,073
2002 56.40 161.10 54,497 49,439
2003 54.23 159.41 56,278 51,055
2004 50.64 149.75 56,723 51,458
2005 58.01 150.00 60,580 54,957
2006 42.86 101.78 51,649 46,855
2007 35.00 108.80 59,169 53,677
2008 32.57 94.18 55,427 50,283
2009 27.55 76.85 49,380 44,797
2010 28.79 80.88 52,321 47,465
2011 25.30 57.01 46,959 42,601
2012 20.32 16.61 41,975 38,079
2013 20.32 18.04 40,901 37,105
2014 20.49 11.67 39,319 35,670
2015 18.86 9.11 40,312 36,570
Percent Reduction, 2001-2015
68 95 24 24
CO2
Year
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Appendix Table 5 2015 Monthly System Emission Rates of NOX, SO2, and CO2 (lb/MWh)
Appendix Table 6 New England System
Annual Average NOX, SO2, and CO2 Emission Rates, 1999 to 2015 (lb/MWh)
Month NOX SO2 CO2
1 0.46 0.40 817
2 0.68 0.91 981
3 0.39 0.21 748
4 0.26 0.04 614
5 0.29 0.04 682
6 0.27 0.03 654
7 0.29 0.07 743
8 0.29 0.05 751
9 0.31 0.07 730
10 0.35 0.06 824
11 0.32 0.06 744
12 0.28 0.05 664
Monthly System Emission Rates (lb/MWh)
YearTotal Generation
(GWh)NOx SO2 CO2
1999 104,409 1.36 4.52 1,009
2000 110,199 1.12 3.88 913
2001 114,626 1.05 3.51 930
2002 120,539 0.94 2.69 909
2003 127,195 0.93 2.75 970
2004 129,459 0.78 2.31 876
2005 131,874 0.88 2.27 919
2006 128,046 0.67 1.59 808
2007 130,723 0.54 1.66 905
2008 124,749 0.52 1.51 890
2009 119,282 0.46 1.29 828
2010 126,383 0.46 1.28 829
2011 120,612 0.42 0.95 780
2012 116,942 0.35 0.28 719
2013 112,040 0.36 0.32 730
2014 108,356 0.38 0.22 726
2015 107,916 0.35 0.17 747
Percent Reduction, 1999 - 2015 74 96 26
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Appendix Table 7 LMU Marginal Heat Rate, 2009 to 2015 (MMBtu/MWh)
Appendix Table 8 2015 LMU Marginal Emission Rates—All LMUs (lb/MMBtu)
Appendix Table 9 2015 Monthly LMU Marginal Emission Rates—All LMUs (lb/MWh)
YearAll Marginal
LMUsEmitting
LMUs
2009 8.591 8.507
2010 7.414 8.385
2011 6.907 8.190
2012 6.678 7.870
2013 6.841 8.271
2014 7.692 9.034
2015 6.707 8.096
LMU Marginal Heat Rate (MMBtu/MWh)
On-Peak Off-Peak On-Peak Off-Peak
NOX 0.051 0.023 0.048 0.048 0.042
On-Peak Off-Peak
SO2 0.059 0.043 0.050
CO2 133 124 128
Air Emission
Ozone Season
Ozone / Non-Ozone Season Emissions (NOx)
Annual Emissions (SO2 and CO2)
Non-Ozone Season Annual Average
(All Hours)
Air Emission
Annual Annual Average
(All Hours)
Month NOX SO2 CO2
1 0.46 0.84 968
2 0.96 1.88 1146
3 0.30 0.38 860
4 0.11 0.03 737
5 0.21 0.10 805
6 0.17 0.04 765
7 0.24 0.17 822
8 0.31 0.24 840
9 0.24 0.24 845
10 0.22 0.14 879
11 0.14 0.06 820
12 0.11 0.02 815
LMU Marginal Emission Rates (lb/MWh)
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Appendix Table 10 2015 LMU Marginal Emission Rates—Emitting LMUs (lb/MMBtu)
Appendix Table 11 2015 Monthly LMU Marginal Emission Rates—Emitting LMUs (lb/MWh)
On-Peak Off-Peak On-Peak Off-Peak
NOX 0.054 0.024 0.049 0.051 0.044
On-Peak Off-Peak
SO2 0.059 0.045 0.051
CO2 130 126 128
Air Emission
Ozone Season Non-Ozone Season Annual Average
(All Hours)
Ozone / Non-Ozone Season Emissions (NOx)
Annual Emissions (SO2 and CO2)
Air Emission
Annual Annual Average
(All Hours)
Month NOX SO2 CO2
1 0.58 1.02 1205
2 1.19 2.27 1404
3 0.38 0.48 1088
4 0.16 0.05 914
5 0.25 0.14 946
6 0.22 0.05 934
7 0.30 0.22 992
8 0.41 0.32 1046
9 0.29 0.28 994
10 0.26 0.16 1017
11 0.17 0.07 971
12 0.13 0.03 945
LMU Marginal Emission Rates (lb/MWh)
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Appendix Table 12 NOX LMU Marginal Emission Rates, 2009 to 2015 —All LMUs (lb/MWh)
Appendix Table 13 NOX LMU Marginal Emission Rates, 2009 to 2015—Emitting LMUs (lb/MWh)
Annual Average
(All Hours)
2009 0.36 0.39 0.29 0.45 0.38 -
2010 0.62 0.47 0.33 0.47 0.46 21.7
2011 0.24 0.29 0.14 0.36 0.27 -42.2
2012 0.35 0.21 0.19 0.16 0.22 -18.4
2013 0.32 0.21 0.35 0.43 0.34 56.7
2014 0.21 0.14 0.51 0.56 0.38 13.1
2015 0.34 0.16 0.32 0.32 0.28 -26.2
% Change 2009 - 2015
-4.4 -60.0 11.4 -28.6 -24.9
Year On-Peak Off-Peak On-Peak Off-Peak
Ozone Season Non-Ozone Season
Annual Average
Percentage Change
Annual Average
(All Hours)
2009 0.45 0.53 0.33 0.61 0.49 -
2010 0.69 0.49 0.40 0.62 0.55 11.8
2011 0.32 0.31 0.17 0.46 0.33 -39.8
2012 0.40 0.26 0.23 0.19 0.26 -22.0
2013 0.37 0.26 0.42 0.56 0.42 62.7
2014 0.26 0.17 0.59 0.72 0.47 12.1
2015 0.44 0.19 0.39 0.41 0.36 -24.0
% Change 2009 - 2015
-1.2 -63.7 17.9 -32.5 -27.3
Year On-Peak Off-Peak On-Peak Off-Peak
Ozone Season Non-Ozone Season
Annual Average
Percentage Change
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Appendix Table 14 SO2 LMU Marginal Emission Rates, 2009 to 2015—All LMUs (lb/MWh)
Appendix Table 15 SO2 LMU Marginal Emission Rates, 2009 to 2015—Emitting LMUs (lb/MWh)
2009 1.12 1.72 1.47 -
2010 1.05 1.45 1.29 -12.2
2011 1.34 1.35 1.35 4.7
2012 0.39 0.32 0.35 -73.9
2013 0.51 0.59 0.55 56.0
2014 0.46 0.45 0.45 -18.0
2015 0.40 0.29 0.33 -25.8
% Change 2009 - 2015
-64.4 -83.2 -77.2
Year On-Peak Off-PeakAnnual
Average (All Hours)
Annual Average
Percentage Change
2009 1.40 2.28 1.90 -
2010 1.19 1.76 1.52 -20.0
2011 1.65 1.60 1.62 6.6
2012 0.45 0.39 0.42 -74.3
2013 0.59 0.76 0.69 65.9
2014 0.53 0.56 0.55 -20.2
2015 0.48 0.36 0.41 -25.2
% Change 2009 - 2015
-65.7 -84.1 -78.3
Year On-Peak Off-PeakAnnual
Average (All Hours)
Annual Average
Percentage Change
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Appendix Table 16 CO2 LMU Marginal Emission Rates, 2009 to 2015—All LMUs (lb/MWh)
Appendix Table 17
CO2 LMU Marginal Emission Rates, 2009 to 2015—Emitting LMUs (lb/MWh)
2009 882 946 919 -
2010 1,019 1,036 1,029 12.0
2011 943 908 922 -10.4
2012 876 839 854 -7.4
2013 921 937 930 8.9
2014 931 949 941 1.2
2015 891 832 857 -9.0
% Change 2009 - 2015
1.0 -12.0 -6.8
Year On-Peak Off-Peak Annual Average
(All Hours)
Annual Average
Percentage Change
2009 1,042 1,242 1,157 -
2010 1,138 1,215 1,183 2.2
2011 1,148 1,061 1,097 -7.3
2012 1,019 1,003 1,010 -7.9
2013 1,079 1,163 1,125 11.4
2014 1,064 1,138 1,107 -1.6
2015 1,053 1,023 1,036 -6.4
% Change 2009 - 2015
1.1 -17.6 -10.5
Year On-Peak Off-Peak Annual Average
(All Hours)
Annual Average
Percentage Change