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

2015AirEmissionsReport PageiiISO‐NEPUBLIC

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

2015AirEmissionsReport PageiiiISO‐NEPUBLIC

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

2015AirEmissionsReport Page1ISO‐NEPUBLIC

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.


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%


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.


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.


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.


simulationruns.Beginningwiththe2004MEAstudy,themarginalheatratewasbasedontheactualgenerationofmarginalfossilunitsonly.

Beginningwiththe2007MEAReport,themarginalheatratehasbeencalculatedusingacombinationofbothUSEnvironmentalProtectionAgency(EPA)heatinputdataandtheheat‐rateinformationcollectedandmaintainedbytheISO.ForthemarginalfossilunitswithEPAdata,theheatinputsreportedtoEPAwereused.ForunitswithoutEPAdata,theheatinputswerecalculatedbymultiplyingeachunit’smonthlygenerationbytheISO’sheat‐ratedata.Theindividualheatinputvalues(inMMBtu)usingthetwomethodswerethenaddedandthesumdividedbythetotalgenerationofthemarginalfossilunits.

Inthecurrentmethodology(seeSection3.4),thecalculationforthemarginalheatrateisbasedontheheatratesforeachindividualLMU.Thepercentageoftimeeachgeneratorismarginalperyearleadstothecontributionofthatunit’sheatratetotheLMUmarginalheatrate.


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.


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


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).


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.


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.


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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Generation (million M

Wh)

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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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arginal

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2011: 0.06%2012: 0.04%2013: 0.10%2014: 0.04%2015: 0.07%


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.


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.


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.

4.62

2.16

8.12

3.04

0.62 0.310

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CT ME MA NH RI VT

NOXNOX

1.39

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SO2SO2

10,552

3,582

15,689

6,487

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709 0

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CT ME MA NH RI VT

CO2CO2

Annual Emissions of NO

X, SO2, C

O2(kTo

ns)


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.


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.


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)


Air Emission


(All Hours)

On-Peak Off-Peak On-Peak Off-Peak

NOX 0.44 0.19 0.39 0.41 0.36


Air Emission


(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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U M

arginal Emissions Rate (lb/M

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U M


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SO2‐On Peak

SO2‐Off Peak

NOx‐All Hours

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CO2‐All Hours

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CO2‐Off Peak

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NOx‐Ozone Off Peak

NOx‐NonOzone On Peak

NOx‐NonOzone Off Peak

CO2‐All Hours

CO2‐On Peak

CO2‐Off Peak


Table 5‐5 High Electric Demand Day LMU Marginal Emission Rates (lb/MWh)

HEDD LMU Marginal Emission Rate (lb/MWh)


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.


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


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


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


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)


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



Non-Ozone Season Annual Average

(All Hours)

Air Emission


(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)


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)


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


(All Hours)



Air Emission


(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)


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


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


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

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