能源轉型時代的能源網(wǎng)絡-Energy Networks in the Energy Transition Era

May2022

EnergyNetworksintheEnergyTransitionEra

OIESPaper:EL48RahmatallahPoudineh,SeniorResearchFellow,OIES

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Copyright?2022

OxfordInstituteforEnergyStudies

(RegisteredCharity,No.286084)

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ISBN978-1-78467-199-0

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Abstract

Asinfrastructuresthatconnecttheenergysourcewiththeenergyuse,energynetworksconstituteacrucialelementofnationalandglobalenergysystems.Theyalsoplayakeyroleinhelpingwithbalancingsupplyanddemand,thusensuringthatenergyisnotonlyavailableintherightplacesbutalsoattherighttime.Energytransitionwillhavesignificantimpacts,thoughnotnecessarilyinthesameway,onexistingenergynetworks,forexample,electricityandnaturalgasgrids,andmightleadtothegrowthofnewenergycarriersystems,suchasdistrictheatingandcoolingandthedeploymentofnewinfrastructurestosupporttheuseofhydrogen.Understandingtheimplicationsofenergytransitionforenergynetworks,andthewaysinwhichtheseinfrastructuresshouldadapttothechallengesofdecarbonization,isimportanttoachievenet-zerocarbonobjectives.Thispaperexploressomeofthekeyissuesfacedbyelectricitytransmissionanddistributionnetworks;naturalgasnetworks;andfuturehydrogen,heating,andcoolingnetworksinthetransitionofenergysystems.Also,asfuturedecarbonizedenergysystemsarelikelytoexhibitsignificantlymoreinteractionbetweendifferentpartsofthesystem,thispaperexplorespossibleapproachestoutilizingthesynergiesbetweenenergynetworksandbenefitingfromtheirintegratedoperationtolowerthecostsandchallengesofdecarbonization.

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Contents

Abstract ii

Figures iii

Tables iii

1.Introduction 1

2.Energynetworks 2

2.1Electricitytransmissionnetworks 2

2.1.1Theeffectofmarketdesign 5

2.1.2Electricitydistributionnetworks 5

2.2Naturalgasnetworks 8

2.3Hydrogennetwork 11

2.4Heatingandcoolingnetworks 12

3.Integratedenergynetworks 16

4.Summaryandconclusions 19

References 22

Figures

Figure1:Naturalgasinprimaryenergyinglobalwholeenergysystemscenariosthatmeeta1.5°C

warmingtarget 9

Figure2:YearlyheatdemandintheUKacrosssectors(2019) 13

Figure3:Globalenergyconsumptionforspacecoolinginbuildings 15

Figure4:Shareofheating/coolingdemandmetthroughdistrictenergysystemsinselectedcountries 15

Figure5:Threelayersofanintegratedapproachtonetworkplanningandoperation 17

Figure6:IllustrativepossibleinteractionsbetweendifferentenergynetworksintheUK 18

Tables

Table1:Transformationoftheelectricitysystemanditsimplications 3

Table2:Anexampleofatransmissionconstraintandtherangeofpossiblesolutions 4

1

Thecontentsofthispaperaretheauthor’ssoleresponsibility.Theydonotnecessarilyrepresenttheviews

oftheOxfordInstituteforEnergyStudiesoranyofitsMembers.

1.Introduction

Energynetworksareinfrastructuresthatconnecttheenergysourcewiththeenergyuseandthusconstituteacrucialelementofnationalandglobalenergysystems.Overthelasthundredyears,thenetworks(especiallyelectricityandgas)haveevolvedfromlocalsimplegridsintocomplexinfrastructuresthattransferenergynotonlywithinnationalboundariesbutalsoacrossbordersinareliableandefficientmanner.

Thenet-zerocarbontargetwillresultinasignificantchangeinenergysystemswithsignificantimplicationsforexistingenergynetworks.Itmayalsoleadtothegrowthofnewenergycarriersystems,suchasdistrictheatingandcooling,andpotentiallygiverisetonewinfrastructuretosupportthedeliveryanduseofhydrogen.

Theelectricitynetworks,inparticular,arefacingsignificantchangesasaresultofthetransformationcurrentlyunderwayintheenergysystem.Electricityisthefastestgrowingconsumerenergybecauseoftherolethatitisexpectedtoplayinthedecarbonizationofthetransport,buildingandindustrialsectors.Traditionally,electricitywasgeneratedinlargecentralizedthermalorhydropowerplants,whichfeedintoatransmissiongridthatconnectsindustrialloadsandsuppliessmallerconsumersthroughdistributiongrids(IEA,2021).Thedesignoftransmissiongridswassuchthatpowerflowsbetweenpowerplantsandmainconsumptioncentreswithinaspecificregionwereeasilyaccommodatedwithoutstructuralcongestion.However,renewableenergyresourcessuchasonshorewindfarms,utility-scalesolarfacilities,andoffshorewindfarmsareoftenlocatedfarfromloadcentres,whilethermalgenerationplantsareeitherbeingphasedoutorforcedoutofthemarketbycheaprenewables.Atthesametime,thereisahugegrowthinsmallerdistributedenergyresources(DERs)onthedistributiongrid.Thesedevelopmentswillchangetheflowpatternwithintheelectricitynetworksandmaycreatenewconstraints,andthusnecessitatemoreefficientutilizationofexistinggridassets,newgridinvestments,andinsomecasesevennewoverallgridandelectricitymarketdesigns.

TheriseofDERs,andthedecentralizationparadigminparticularisupendingthebalancebetweentheelectricitytransmissionanddistributionsectors.Distributiongrids,whichhavehistoricallybeenpassiveandaddressedgridconstraintsthroughoverengineering,arenowbecomingmoreactive.Alongwiththeneedfornewrules,thisalsomeansnewrolesfordistributionsystemoperators(DSOs)tofacilitateefficientintegrationofDERswhileachievingahigherlevelofcoordinationwiththetransmissionsystemoperator(TSO).ThisistoimprovevisibilityandcontroloverDERsandavoidpotentialconflictbetweenDSOsandtheTSO.

Apartfromelectricity,naturalgasisanothermajorenergynetworkinmanycountries.However,thefutureofthenaturalgasgridisuncertain,especiallyatthelow-pressuredistributionlevel.Itpartlydependsonfutureenergyservicescenariosinwhichnaturalgasisprimarilyused,forexample,forheating,andpartlyonthetechnologicalprogressmadetolowerthecostsofcarboncaptureandstorage.Theuseofnaturalgasnetworksmustchangeifthesenetworksaretoplayaroleunderthenet-zerocarbonobjective.Low-carbonalternativessuchashydrogenareapotentialreplacementfornaturalgasbutarangeofchallengesexists.Forexample,astheshareofnaturalgasdeclines,availablevolumesofhydrogenmaynotbesufficienttojustifyadjustingtheexistingnaturalgasinfrastructures.Also,hydrogencanbetransportednotonlyviaarepurposedgasnetwork(ornewpipeline),butalsoviaavailablepowerandtransportationnetworks,suchasbyrail,road,andonwaterways.Thismeansthat,despitetheefficiencyofpipelines,repurposingthegasnetworkmightnotalwaysbetheoptimalsolution.

Thereareotherenergynetworksemergingtoaddressthechallengesofdecarbonizingtheheatingandcoolingsectors.Heatnetworkscurrentlyhavelittleenergydemandmarketsharegloballybut,giventheiradvantageoverindividualheatingsystemsandalsothegrowingurgencyofdecarbonizingheatinginthebuildingsector,theirshareisexpectedtoincrease.IntheUK,forexample,theenergydemand

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forheatingaccountsformorethan40percentofallenergyuseandcontributestoaroundone-thirdofcarbonemissions.Underfavourableregulatoryandpolicyconditions,districtheatingcouldbecomethemainmethodofprovidingheattobuildingsinhigh-densitybuiltenvironments,suchascitycentresandcampuses,aswellassomeruraloff-gasgridcommunitiesinthiscountry.

Coolingnetworksarelesscommoncomparedwithdistrictheating,butwiththeriseindemandforspacecoolingintheGlobalSouththesenetworksmayalsogainmoreimportance.IntheUnitedArabEmirates,districtcoolingcurrentlyprovidesmorethanone-fifthofthecoolingload(IRENA,2017b).Theeconomiesofscaleandincreasedefficiencyofprovidingcentralizedspacecooling,comparedwithindividualair-conditioningsystems,canreducetheircostssignificantly.Similartodistrictheating,districtcoolingalsorequiresappropriatepoliciesandregulationstofacilitateitsdeploymentinplaceswithhigh-loaddensity.

Asenergysystemsbecomemorecomplexduetodecarbonization,decentralizationanddigitalizationtrends,theimportanceofenergynetworksascriticalinfrastructuresthatexploitandfacilitatetemporalandspatialdiversityinenergyproductionandconsumptionincreases.Itisthusnecessarytounderstandhowbesttodesign,regulate,integrateandoperateexistingandemergingenergynetworksinordertobenefittheentireenergysystem.Currently,energynetworks,whethertheybeelectricity,gas,heatingorcooling,arecommonlyplannedandoperatedindependently,whichresultsinalossofsynergiesandefficiency(Hosseini,2020).Theseseparateinfrastructuresarenowincreasinglybecominginterconnectedthroughnetworkcouplingtechnologies,suchascombinedcyclegasturbines(CCGT);combinedheatandpowerunits(CHP);andpower-to-Xtechnologies,suchashydrogen,ammonia,heating,cooling,andheatpumps.Anintegratedapproachtotheplanningandoperationofthesenetworkscanlowertheuseofprimaryenergy,provideflexibilitytointegratevariablerenewableenergyresourcesandlowerthecostofachievinganet-zerotarget.Thishoweverentailsaddressingarangeofoperational,regulatory,andgovernanceissues.1

Theoutlineofthispaperisasfollows:Section2discussesissueswhichindividualenergynetworksarefacingduringtheenergytransition,startingwithelectricitytransmissionanddistributiongridsthengoingontonaturalgasandhydrogengridsandfinishingwithheatingandcoolingnetworks.Section3discussestheideaofanintegratedenergynetwork.Finally,Section4providesasummaryandconclusions.

2.Energynetworks

Energynetworksareinfrastructuresthattransferenergyfromtheproductionsourcetotheconsumers’premises.Theyconstitutevariousformsoftechnologiesrangingfromestablishednetworks,suchaselectricityandnaturalgas,toemerginggrids,suchashydrogen,heating,andcooling.Inthissection,webrieflyrevieweachofthesenetworksandhighlightthechallengesandopportunitiestheyfaceasaresultoftheenergytransition.

2.1Electricitytransmissionnetworks

Aswemovetowardsanet-zerocarboneconomy,theelectricitysectorisexperiencingaprofoundtransformation(BEIS,2021a).Onthesupplyside,theriseofrenewableenergyresourceshasledtopowergenerationbecomingincreasinglyvariableanduncertainwhilethepenetrationofDERsimpliesashiftofvaluefromtransmissiontothedistributionlevelduetodecentralization.Onthedemandside,electricitydemandisnotonlyexpectedtorise,duetotheincreasedelectrificationofactivitiesandprocesses,butmayalsobecomemoreuncertainbecauseofthenatureofnewlyelectrifiedactivities

1Theseincludeeconomicissues,suchascoordinationinthepresenceoffragmentedinstitutionalandmarketstructuresofdifferentenergysystems,aswelltechnicalchallenges,suchaspreventingcascadingfailures,loweringvulnerability,andimprovingtheresilienceofintegratedenergynetworks(Tayloretal.,2022).

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(forexample,electricvehiclescanpotentiallychargeatanytimeandatanylocationonthenetwork).Inaddition,networkusersarebecomingmoreactiveasdigitalizationandautomationlowerthetransactioncostsofinteractingwiththeelectricitysystem.Theseallhaveimplicationsfortheentireelectricitysystem,includingthenetworkinfrastructure(seeTable1).

Table1:Transformationoftheelectricitysystemanditsimplications

Transformationofthepowersystem

Generation

Variableanduncertainrenewablegeneration

Distributedenergyresources

Energystorage

Electricitydemand

Theriseofelectricityconsumption(e.g.datacentres,

electricvehicles,heatpumps,air-conditioning)

Increaseinuncertaintyofdemand

Networkusers

Activenetworkusers(sumers,energy

communities)

Communicationandcontrol

Digitalizationandautomation

Implicationsforthepowersystem

Initialfocus

Presentfocus

Planning

Renewable

generation

Capacitygrowth

Systeminteraction,integrationcosts

Network

infrastructure

Sufficientcapacitytoaccommodateallusers

Market-basedanddifferentiatedgridaccessregime,competition,costallocation,coordinationwithgeneration

Operation

Reliabilityoperationalsecurity

and

Throughmarket

energy-only

Searchfornewparadigm

Flexibility

Fromconventionalpowerplants

Newsolutions(e.g.DERs,demandresponse,energystorage)andnewincentivesandframeworksforflexibleservices

Source:author

Indeed,adifferentelectricitynetworkisneededcomparedtowhatwehadinthepast.Electricitynetworksrequirehighercapacityandinterconnectionsaswellasmoreefficientapproachestocaterfortheriseintheelectricitydemandandtheincreasedcomplexityandchallengeinasystembalancingsupplyanddemand.

Althoughdecentralizationimpliesthatanincreasinglyhigherproportionofgenerationfacilitiesarelocatedonthedistributionside,significantinvestmentinthetransmissionnetworksisstillrequiredduetothediversegeographicallocationofnewmajorresources,suchasonshoreandoffshorewindfarms,aswellastheincreasedneedforinterconnectivitybetweenelectricitymarkets.

Therearetwoimportantpointswhenitcomestoexpandingthetransmissiongrid.First,thedesignandconstructionofnewtransmissionassetsisacomplexandcostlyprocesswithalongleadtime.Second,thereisstilluncertaintyaboutthetimingandpaceofdecarbonizationofheatingandtransportaswellastheextenttowhichelectrificationcanoutcompetealternativeoptionsinallapplicationsoftheseservices.Thissuggeststhatfuturenetworkinvestmentsneedtoberobustinthefaceofarangeofpossibletransitionpathwayoutcomesforthesetwosectors.

Akeyconcernassociatedwithtraditionalnetworkinvestmentmodelsisrelatedtoeconomicefficiencyandtheirnarrowfocusonasset-basedsolutions,withoutconsideringthefactthatwhilegridexpansioniscrucial,lowercostsandtimelysolutionsmustbeaddressedfirst.Asanexample,consideraregion

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inwhichthereisanexcesssupplyofwindgenerationbutlowdemandduetolowerpopulationdensity,whichresultsinatransmissionconstraint.Thestandardsolutiontothischallengeinthepasthasbeentoaddanewwirethatconnectstheareawherethereisovergenerationtothenearesthighdemandcentre.AsseeninTable2,thedeploymentofanewtransmissionlineisoneoffivepossiblesolutionsforthisproblem.Indeed,thisproblemcanbesolvedbyabattery;anaggregator;avoltageserviceprovider;orasinglelargeindustrialdemand,suchasanelectrolyser,whichcanabsorbtheovergeneration.

Table1:Anexampleofatransmissionconstraintandtherangeofpossiblesolutions

Transmissionconstraintexample:thereisahighlevelofwindpowergenerationinanareawithlowerdemand

Solution1:addingawiretoconnectthehighsupplyareatoanareaofhighdemand

Solution2:deployingabatterythatstoresenergywhensupplyishighandreleasesitbacktothegridwhendemandishigh

Solution3:anaggregatorwhichcanaggregatedemandwiththeabilitytoturnitupordownwhenneededtomatchthesupply

Solution4:avoltageserviceproviderthatcanrespondtotheparticularchallengeofasurgeinelectricitysupplyasresultofasuddenincreaseinwindgeneration

Solution5:asinglelargeindustrialdemand,suchaselectrolysers,whichcanreacttowindpowergenerationsurges

Source:adaptedfromBEIS(2021a)

Theproblemisthatwhennetworkcompaniesarenotincentivizedtoconsiderwidersolutionstogridconstraints,Solution1isalmostalwaysthepreferredchoiceevenifitiseconomicallyinefficient.Thisisbecausenetworkcompanieshaveabiastowardsasset-basedsolutionsasnoneoftheotherapproachesincreasethenetworkcompany’sregulatoryassetbase,thusallowingittoreceiveareturn.Onthecontrary,implementingothersolutionsmayevenresultinlowerrevenueforthenetworkcompanyifthevolumeofenergytransportedinthegriddeclines.

Thisisspecificallythecasewhenthenetworkoperatorandnetworkownerarethesameorganizationandwasoneofthereasonsthat,intheUK,theNationalGridElectricitySystemOperator(NGESO)waslegallyseparatedfromthetransmissionowner,NationalGridElectricityTransmission(NGET),althoughtheybothbelongtothesamegroup—theNationalGrid(NG)Group.Therearenowdiscussionstogoevenfurtherandestablishanindependentenergysystemoperatorwhichhasabsolutelynointerestinregulatedelectricityandgasassets.

Therefore,aligningtheincentiveofthenetworkcompaniesiscriticaltoachieveinvestmentefficiency.Althoughthemarketfornon-networksolutionsatthetransmissionlevelmightnotbewell-developedattheoutset,theintroductionofspecificincentivescanencouragethird-partyproviderstoinnovateandgrow,especiallyasthetechnologyadvances.

Theincreaseintherangeofsolutionsalsoallowsforthepossibilityofutilizingmarketmechanismsandcompetitioninasupplychainsegmentthathastraditionallybeenconsideredasanaturalmonopoly.However,giventhatthetypeofnetworkconstraintaffectstherangeofsolutionsavailabletofixthem,anauctionfortheprocurementofsolutionscanbearrangedindifferentways.Sometimesanetworkconstraintmayhaveaclearuniquesolutionandothertimestheremightbearangeofpossiblesolutions.Thus,thecompetitiontoprocurenetworkservicesneedstoaccountfortheseidiosyncrasiesinthetypeofnetworkconstraintsandassociatedsolutions.IntheUK,withdiscussionsaboutintroducingcompetitioninonshoretransmissionnetworks,theregulatoristryingtodesignacompetitionframeworkthataccommodatesthesecomplexities.‘Earlycompetition’issuggestedincaseswhereagridconstraintisidentifiedbutthetenderhappenspriortothesurvey,consent,anddetaileddesignoftheassetbeingdevelopedsothewholeprocessofdesigning,constructing,anddeliveringthesolutionis

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tenderedfor(BEIS,2021).Thisistoallowforthefactthattheelectricitysystemischangingandmoresolutionsmightbecomeavailablebythetimethetenderhappens.The‘latecompetition’modelisproposedwhenthenetworkproblemisidentifiedandthesolutionisdecidedsothecompetitiontakesplacetobuild,own,andoperatetheagreedsolution.

Despitetheappealofacompetitionforatransmissionnetworkinfrastructure,therearesomeimportantissuesthatneedtobeconsideredforthechoiceofsolutionandtheassociatedauction.First,theleadtimeoftransmissionprojectsishigh,whilethechangeinthegenerationanddemandpatternsisveryuncertaingivencurrentdevelopmentsintheelectricitysector.Thissuggeststhattheneedforactualtransmissioninvestmentcanalterbythetimeaprojectisdelivered.Second,thereisahighlevelofuncertaintyinthecostoftransmissionprojectsandtherearemanyfactors,suchasmeetingplanningrequirements,thatcanaffecttheoutturncostbutcannotbefullyaccountedforatthetimeofdecision.Third,theeffectoftheseproceduresonothercompetitionmechanisms,suchasthoserelatedtosystemservices(runbytheelectricitysystemoperator)orflexibilitytenders(runbythedistributionnetworkoperator),needtobecarefullyexamined.Therefore,introducingcompetitionfortheprocurementofnetworkservicesrequirescarefuldesignandimplementation.

2.1.1Theeffectofmarketdesign

Thediscussionaboutnetworkoperationanddevelopmentcannotbedecoupledfromthedebateonthedesignoftheelectricitymarket.Theriseofvariableanduncertaingeneration,andthefactthattherenewableresourcesareoftenlocatedawayfromtheloadcentre,willchangetheexistingpatternsofflowinelectricitynetworksandthusresultinnewconstraints.Thechallengeisthatlocalcongestion,whetherintransmissionordistribution,isnotreflectedinelectricitymarketpricesinmostplacesaroundtheworldduetothesuboptimaldesignoftheelectricitymarket.Europeanelectricitymarkets,forexample,arestructuredaroundbiddingzones,whichmeansintrazonalcongestioncanbecomeapersistentchallenge.Currently,transmissionsystem’sconstraintsaremanagedbycost-basedormarket-basedregulatedredispatchoftheflexibilityresourcesinthezone.However,thiscanattimesbeverycostly.

Thekeychoicestoaddresstransmissioncongestion,inthecontextoftheEuropeanelectricitymarketdesign,areeithertoexpandthenetworkortoreconfigurebiddingzonessuchthattheyreflecttheactualstructuralcongestion.Networkexpansionisnotalwaysthemostcost-efficientsolution.Furthermore,thereisnoguaranteethatinthefuturenewstructuralcongestionwouldnotariseafterthenetworkhasbeenexpanded.Animprovedzonalmodelwithadequatedemarcationofbiddingzonescanbeacheapersolutionthannetworkreinforcement.However,apartfromthechallengesofimplementingawell-definedbiddingzone,itisalsosusceptibletoso-calledincrease-decrease(inc-dec)gamingopportunities.

Fromamarketdesignperspective,locationalmarginalpricing(LMP),alsocallednodalpricing,istheoptimumapproachtoutilizethegridefficiently.Inthismodel,thepriceateachnodeofthegridrepresentstheactualcostofsupplyingthatparticularnodegiventhenetworkconstraint.Thus,unlikezonalpricing,LMPtakesintoaccountthephysicalcharacteristicsofthegridwhichmeansno‘outofmarket’instrumentsarerequiredtoaddresscongestion,meaningthereisnoneedforredispatchofflexibilityservices.Itisalsolessvulnerableto‘inc-dec’games.Nonetheless,theimplementationofLMPinthecontextoftheEuropeanelectricitymarketisunlikelytobestraightforwardassuchashiftwouldimplymajorchangesformoststakeholdersinthemarket.

2.1.2Electricitydistributionnetworks

Electricitydistributionnetworksareexpectedtobearthebruntoffurtherelectrificationoftransportandheatingservices.Theiroperatingenvironmentisalsofast-changingduetotherapidgrowthofDERsandtheriseofprosumers.Asaresult,thesenetworksneedtooperateunderconditionsofincreasedvariableloadandgenerationaswellasmorefrequentcongestion.Therearethreeregulatory

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instrumentsthatplayacriticalroleinaddressingthechallengesthatdistributionnetworksfaceduringthetransitionera(Gómezetal.,2020).

Thefirstinstrumentisthegridaccessregime.Traditionallygridaccess,forbothconsumersandgenerators,isprovidedonafirmbasis.Thefirmaccessmodelallowsuserstowithdrawand/orinjecttothenetworkuptothemaximumcapacity2oftheinstalledfuseatanytimeorlocation.Despiteitssimplicitygivenlackofneedforreal-timemanagementofinjectionsandwithdrawalbythegridoperator,firmaccessisaninefficientapproach.Thisisbecause,underthisregime,alargepartofthenetworkcapacityisidleasnetworkcomponentsareoftenusedattheirratedvalueonlyforverylimitedtimesoftheyear.Firmaccessalsopreventsnewusersfrombeingconnectedwheneveryuserisgivenagridaccessoptionattheirmaximumratedcapacity.

Anon-firmoraflexibleaccessregime,ontheotherhand,isbetteralignedwiththerequirementforfastandefficientgridconnectioninanelectricitysystemwhichisexperiencingrapidgrowthofrenewableanddistributedenergyresources.Aflexibleconnectionprovidesthenetworkoperatorwiththerighttomanagetheuserfeed-inorconsumptioninexchangeforincentivessuchasdirectrenumeration,arebateongridconnectioncosts,fasterconnection,orsimplytherighttoconnectratherthanrefuseacustomer’sconnectionapplication.Inthisway,theneedforfurthernetworkreinforcementdeclinesandmoreuserscanbeac