Preparing for the Hydrogen Economy by Usingthe Existing Natural Gas System as a Catalyst

Project Contract No.: SES6/CT/2004/502661

Using the Existing Natural Gas System for Hydrogen

www.naturalhy.net

Welder inside Two Sections of 48" Pipe, Welding the Seam to Create One Continous Section of Pipe

Published October 2009

table of contents

1. Executive Summary | page4

2. Introduction |page6

3. Background: the role of hydrogen

in the transition towards a sustainable energy society | page8

4. The NATURALHY-approach: what can the natural gas

system offer for the delivery of hydrogen? | page10

5. What is the impact of adding hydrogen to natural gas

on the durability of the network? | page12

6. What measures should be taken to control and monitor

the condition of the network? |page14

7. What is the impact of adding hydrogen to natural gas on

the safety aspects? | page16

8. What is the impact of adding hydrogen to natural gas on

end user aspects? | page18

9. Separation of hydrogen from a hydrogen/natural gas mixture

and its impact on the quality of the remaining gas | page20

10. How to assess a specific network for the NATURALHY-concept:

the Decision Support Tool | page22

11. What are the overall benefits of adding hydrogen to natural gas? | page24

12. Concluding remarks | page27

Preparing for the Hydrogen Economy by Usingthe Existing Natural Gas System as a Catalyst

Project Contract No.: SES6/CT/2004/502661

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The European Commission-supportedNATURALHYprojectwassetuptoinves-tigatewhetherhydrogencouldbedeliveredsafelyviatheexistingEuropeannaturalgasnetwork.Thishasinvolvedmappingoutthefeasibility, the consequences and the ben-efits of using the natural gas network forthesafeandefficienttransportofmixturesofhydrogenandnaturalgasacrossEurope.As such, the project has demonstrated thecapabilities of the natural gas network forhydrogendelivery,whichcanbe,potentiallyamajorcontributiontowardssustainability.

Hydrogenisexpectedtobecomeanim-portantfutureenergycarrierbecauseitcansignificantly improvethesecurityofenergysupplyandreduce/avoidemissionsofgreen-housegases.Arangeofsustainablesources,includingbiomass,canbeusedforthepro-ductionofhydrogen.Itcanbeproducedfromthegasificationofcoal,withorwithoutCar-bonCaptureandStorage(CCS)andisalsoaby-product inmany chemical processes.Ofcourse, the combustionofnaturalgaswithadded hydrogen emits less carbon dioxideperenergyunitthanthecombustionofpurenaturalgas,asthecombustionofhydrogenis"carbonfree".

The objective of the NATURALHY proj-ecthasbeentodefinetheconditionsunderwhichhydrogencouldbeaddedtothenatu-ralgastransportnetworkwithoutunaccept-ableimpactontheintegrityofthenetwork,safety,and theperformanceofnaturalgasappliances.Theprojecthasprovedthat:

dependingon the steel fromwhichhigh pressure pipelines are constructed,these pipelines could be used for gasmix-turesthatcontainupto50%ofhydrogen

safety related to the transmission,distributionanduseofnaturalgasisnotsig-nificantlycompromisedcomparedtothecur-rentsituationwithnaturalgasifupto20%of hydrogen is added to natural gas. Addi-tionsupto50%mightbefeasiblebutmustbeassessedcasebycase

1 ExecutiveSummary

5

themaximumpercentageofhydrogenthatcanbeallowedtoensureproperend-useper-formancedependsonappliancetypeandconditionaswellasonlocalnaturalgasdistributionconditions.Fordomesticappliances,amethodhasbeenderivedtoaddressthesequestionsonthelevelofadistributionregion(country)

There isnodoubt that theNATURALHYprojecthasbeenan importantstep inprovidinghithertounavailableinformationwhichcouldmakeasignificantcontributiontothe‘greening’andde-carbonisationofnaturalgaswithhydrogen.

However,therearetwoveryimportantpointstonote:

therearenosimpleanswers.EachpotentialadditionofhydrogentoaparticularpartoftheEuropeangasnetwork

mustbeconsideredindividuallyinconjunctionwiththeproject’sDecisionSupportTool;(seechapter10)

therearesomeaspectsofthegasnetworkthathavenotbeeninvestigatedinfulldetail,astheywerebeyondthescopeoftheNATURALHYproject.

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It is important to begin by stating thattheuseofhydrogencanberegardedascontroversialand,contrarytomuchpopu-larbelief,itisnotthenewwondersourceofenergythatwillsolveallofourenergyproblems;itissimplyanenergycarrier,itsmethodofproductionbeingofcriticalim-portanceindeterminingitscontributiontosustainability. Nevertheless, there is con-siderable interest in the ‘HydrogenEcon-omy’ which means that some way mustbefoundformovinghydrogenaroundbe-tweensourcesandpointsofuseinEurope.Ifwewanttoavoidclogginguptheroadswith hydrogen tankers, an alternativemeans of shipping hydrogen safely andeconomicallyhastobefound.AnobviousoptionwastoconsiderusingtheexistingEuropeannaturalgassystemtotransportnaturalgas/hydrogenmixturesand,withafewlabourpains,theNATURALHYprojectwasborn.Thebasicvisionisthatthemix-ture of hydrogen/natural gas should besuitable for use as such. In addition, theoption of separating hydrogen from themixturebymeansofmembranefiltershasbeeninvestigated.Boththesepossibilitiesareinterestingoptionsforde-carbonisingcurrentenergysystems.

Thisbrochurepresentstheresultsob-tained in this ground-breaking researchprojectwhichhasbeendesignedto iden-tifythepotentialoftheexistingEuropeannaturalgasnetwork for thesafedeliveryof hydrogen. The NATURALHY project isa unique, international research effort,which has been supported throughout bytheEuropeanCommission’sSixthResearchandDevelopmentFrameworkProgramme,FP6.

Results are presented here, in sum-maryform,forthoseinterestedinenergyanditstransitiontowardsamoresustain-ableenergyfuture.Ourintentionistoraiseawarenessoftheissuesrelatedtoaddinghydrogen to natural gas, to highlight the

2 Introduction

7

possibleconsequences,andtogivebothevidenceandaflavourofwhatmightberealisti-callyachievable. Inparticular, theresultsaredirectedatdecisionmakersatthepoliticallevel, industryprofessionals, includingthosefromnetworkcompanies, researchers in thefieldofhydrogenandsustainableenergyandinterestedmembersofthepublic.

TheNATURALHYprojecthasinvestigatedhowandtowhatextentnaturalgasnetworkscouldfurthersupporttheintroductionofhydrogen.Thefollowingchapterssummarisetheconsequencesofaddinghydrogentonaturalgas,forthewholedeliverychain,fromhydro-geninjectionpointinthehighpressuretransmissiongriduptoandincludingenduserap-pliances.Crucially,assessmentoftheoverallenvironmentalandsocio-economicbenefitsoftheNATURALHYapproachhasbeenanintegralpartoftheproject.However,benefitscanonlyberealisedifoptionsaretechnicallyfeasible.Hence,theprojecthasfocussedonpoten-tial"showstoppers",sothatonlythemostimportantissueshavebeeninvestigated,leavingoutsubsequentconsiderationswhichareexpectedtobesolvable,althoughsometimeswithsubstantialcosts.Itisveryimportanttonotethattheresearchanddevelopmentofsourcesofhydrogenwasoutsidethescopeofthisproject.

First,a fewfactsaboutthe NATURALHY project; Itstartedon1stMay2004,andwascompletedon31stOctober2009.Theprojectcomprised39partners,listedinthelastchapter in thisbrochure.Theprojectmanagement teamconsistedof theUniversitiesofLoughboroughandOxford,GDFSUEZ(formerlyGazdeFrance), InstitutodeSoldaduraeQualidade(ISQ),DBIGas-undUmwelttechnik,EXERGIAEnergyandEnvironmentConsult-antsS.A.,andEUROGAS–GERG(TheEuropeanGasResearchGroup).

TheprojectwascoordinatedbyN.V.NederlandseGasunie.Theprojectbudgetamountedto€17million,includingaEuropeanCommissiongrantfor€11million.Furtherinformationisavailableontheprojectwebsitewww.naturalhy.net

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Importantenergy issuesthat theworld is facingnowconcernthesecurityofsupplyandpollutingemissions,particularlygreenhousegases.Thecur-rent transition towards more sustainable energysourcesaimstodealwiththeseissues.Thetran-sitional changes being implemented involve bothtechnicalandnon-technicalaspects,including,forinstance,developingnewenergycarriersandappli-cationsandreducingenergydemand.Forthefol-lowingthreereasonsanimportantroleisforeseenforhydrogenasanenergycarrierinasustainableenergysociety:

1. Hydrogen can be produced in many waysfrom locally available energy sources includingelectrolysis of water using electricity producedfromwindorsolarenergy,orfromgasificationofbiomass. Using such sustainable energy sourcesfor hydrogen production can improve security ofenergysupply.

2.Thelevelsofpollutionfromcontrolledhydro-gencombustionarerelativelylowand,ifproducedfrom sources with low emissions, hydrogen is arelatively clean fuel. Mobile applications fuelledwithpurehydrogencanimprovelocalairqualitybyreplacingpetrolanddieselincarsandbuses.

3.Aspurehydrogencanbeconvertedbyfuelcellsintoelectricity andvice-versawithhigheffi-ciency, ithaspotentialforstorageofelectricalen-ergy(suchasinthecaseofelectricitygenerationfromwindenergywhensupplyexceedsdemand).

Background:theroleofhydrogenin

thetransitiontowardsasustainable

energysociety

3

9

Althoughresearchactivitiesoncrucialtopicssuchasthesustainableproductionofhy-drogen,hydrogenstorage,andfuelcellsarestillongoing,itisbroadlyexpectedthathydro-genwillbeanenergycarrierofincreasingimportanceinourenergymix.Thisexpectationisbasedontheconclusionthatinthenearfuture,sayafter2015,significantvolumesofhydrogencanbeproducedfromthegasificationofcoalorbiomass:thegasificationofbio-massisalmost"carbon-neutral"andwithcarboncaptureandstorage(CCS),carbondioxideemissionsrelatedtocoalgasificationcanberelativelylow.Potentialsuppliesofbiomassaresubstantialandglobalcoalreservesareimmense.Reductionofcarbondioxideemis-sionsbyreplacementoffossilfuelswithhydrogenproducedfrom"lowcarbon"sourcesofenergycouldcontributetode-carbonisationand'greening'ofourenergyeconomy.

10 11

Thefirst logical step towardsa transitionaldelivery system suitable for hydrogen andhydrogen-containinggasesmustbeaninvesti-gationoftheextenttowhich existingassets,includingtheexistingnaturalgaspipelineinfra-structure,canbeusedforhydrogendelivery.

In principle, the existing European naturalgassystemoffersthefollowingopportunities:

in place, so potentially cost-effectiveandavailableintheshortterm

well-establishedgridmanagementandoperationstrategies

widelyspreadandinterconnected

veryhighcapacity

well-establishedsafetyproceduresandanexcellentsafetyrecord,basedonawell-de-velopedmaintenanceandcontrolstructure

broadacceptancebythepublic.

Generallyspeaking,anetworkdesignedfornaturalgascannotbeused forpurehydrogenfor a number of reasons, without modifica-tions to network components or theway it isoperatedandmaintained.Thepointisthatthephysical and chemical properties of hydrogendiffer significantly from those of natural gas.Thedifferencesconcern,amongstotherconsid-erations,density,calorificvalue,ignitionenergy,flammablelimitsandburningvelocity.Eventheadditionofacertainpercentageofhydrogentonaturalgaswillhaveadirectimpacton;

combustionproperties

diffusion into materials and effect ontheirmechanicalproperties

behaviourofthegasmixtureinair.

Asaresultofthesecontrastingproperties,asystemdesignedfornaturalgascannotbeusedwithoutappropriatemodificationsforpurehy-drogen,andvice-versa.

However,theexistingnaturalgastransmis-sion,distributionandend-usesystemscouldbeused, with suitable adjustments, for mixturesof natural gasandhydrogen. In this case, thehydrogen/natural gasmixture can be used di-rectlyor,ifrequired,hydrogenappliancescouldbe fuelledwith “pure” hydrogen by developingdevicestoextracthydrogenselectivelyfromtheSummary of the Existing Natural Gas System

TheNATURALHY

approach:whatcanthenaturalgas

systemofferforthedeliveryofhydrogen?

4

11

mixture.Thedefinitionoftheconditionsunderwhichhydrogencanbeaddedwithoutunaccept-ableconsequencestonaturalgas,andthedevelopmentofdevicesforhydrogenseparationfromamixture,hasbeenanimportantpartoftheNATURALHYproject.

Inprinciple,hydrogencanbeaddedtonaturalgasinthehigh-pressuregrid,inthemediumpressuregrid,orinthelowpressuredistributiongrid,butitmustberememberedthattheexist-ingsystemwasdesignedandconstructedspecificallyfornaturalgasand,asexplainedabove,thephysicalandchemicalpropertiesofhydrogendiffersignificantlyfromthoseofnaturalgas.Inparticular,theadditionofhydrogentonaturalgasmayhaveanimpactonnumerousaspectsoftheexistingsystem.TheworkdoneintheframeworkoftheNATURALHY-projecttoquantifythisimpactfurtherisdescribedindetailinthefollowingchapters:

safetyrelatedtothetransmission,distributionanduseofgas

integrityofpipelines

gasqualitymanagement

performanceofenduserappliances

energycapacityofthedeliverysystem

gaseous(andenergy)losses.

12 13

Gas transportation and distribution net-works are very complex and inhomo-

geneous infrastructures. Adding hydrogento natural gaswill lead to direct contact ofgaseoushydrogenwiththenetworksandtheassociated installations that have been de-signedspecificallyfornaturalgas.

The influenceofhydrogenon thediffer-entmaterials isdiverse.Steelmaterialscanchangetheirmaterialpropertiesinthepres-enceofhydrogenifthereisdirectcontactofhydrogen with clean metal surfaces. In thiscase,thefatiguepropertiesandtoughnessofsteels,usedforthegastransportationpipe-lines,areinfluencedinadetrimentalway.Thismaterial degradation results in higher crackgrowth rates and can lead to the initiationofnewcracks.Consequently, theservice lifeof pipelines can be decreased in compari-sontoservicewithnaturalgas.Furthermore,the pipeline integrity management strategyneeds to be adapted as the systems in usefocusoncorrosiondefectsandnotoncracksorcrack-likedefects.Onthepositiveside,theriskoffast, long-distancecrackpropagationinthepipelineisreduced,ashydrogenaddi-tionwillhaveabeneficialeffect,dueto themore rapid decompression behaviour com-paredwithnaturalgas.Therefore,propagat-ingruptureswillbestoppedmoreeasilyandrapidly.

Atthedownstreamendofthegasgrids,Effect of gaseous hydrogen on resistance of pipe steel

to crack growth in fatigue loading

Whatistheimpactofaddinghydrogentonaturalgasonthedurability

ofthenetwork?

5

13

DBI test bench with controlled space and casing according to EG 97/23

distributionnetworksare inplace to supplynatural gas safely and reliably to the enduser. Since the late 1980’s polymers havebeenheavilyusedfortheconstructionofdis-tributionnetworksbecauseoftheirbeneficialproperties for the purpose of low pressuregas distribution. Polymer pipes do not suf-ferfromconventionalcorrosioneventhoughtheyundergodegradationovertheirlifetime.Beyondthistheyhaveamuchbetterperfor-mance concerning the gas tightness of theconnections in comparison to oldermateri-alssuchascastiron.Ontheotherhandtheyarelessgastightregardingthelossofgasesthrough their pipe wall (permeation) drivenbytheconcentrationgradient.

The amount of natural gas, which can-notbedeliveredtothecustomerbecauseofpermeationlossesisverysmallandacceptedfroma safety, economicandenvironmentalpointofview.Addinghydrogentothenaturalgaswillleadtoachangeingaslossesthroughpermeation, as the transport of hydrogenthroughthewallofpolymerpipes (from in-sidethepipetotheenvironment) isquickerthanfornaturalgas.Thisappliestopolyeth-ylene(PE)andalsotopolyvinylchloride(PVC).Withintheframeworkoftheprojectvariousinvestigationshavebeenperformedinordertodeterminethepermeationpropertiesandthe correspondingeffect on thegas losses.The change in permeation losses has beenevaluated from a safety perspective. Apartfrompermeation, ageingeffects havebeeninvestigated in order to ensure that addinghydrogentothedistributionnetworkwillnotaffectthelifetimeofthisinfrastructureinasignificantway.

Theresultsshowthateffectsonpipema-terialsusedinthenaturalgasgrids,causedbyhydrogen, canbemitigatedbyappropri-ate measures. Modifications to maintain asafe and reliable supply of customers withnaturalgas / hydrogenmixtureswillmainlybenecessaryforpipelinesmadeofsteel,butimportantly, no "show-stoppers" have beenidentified.

Critical initial axial crack depths for 50% and 100% natural mixtures (required lifespan: 60 years; pipeline steel: X70; Environment: 100% hydrogen; no residual stresses)

IFP test bench (2 permeation cells)

345

6

789

10

23

45

6

Pressure (MPa)50 100 150 200 250 300

Crack length (mm)

X70 in 50%NG - 50%H2 mixture

X70 In 100%H2

X70 In 100% H2 and X70 In 50%NG - 50%H2 mixture

14 15

Thematerialinvestigationsidentifiedthatadditionalmeasureswill be required toensuretheintegrityofsteelpipelines,whenhydrogenistransportedbytheexistingnat-ural gas system. Consequently the pipelineintegrity management systems (PIMS) inplaceneedtobeadapted.Modificationswillbenecessaryforwidepartsof theexistingPIMSasdefects,thatarecurrentlynotinthefocus,needtobeconsidered,whenhydrogenistransported.Furthermoretheextentofthemodifications will depend on the hydrogenconcentrationinthenaturalgas.

Thecriticaldefectsregardingthehydro-gentransportationaresharpdefects(cracksandcrack-likedefects),as they introduceasignificant stress into the pipeline and canlead to interactions between hydrogenandthepipelinematerial.Aswellas thedefecttype, it isvery important toknowthecriti-cal size of defects. Cracks can grow overtime(cracksaretimedependentdefects)soknowledgeofthecrackgrowthrateinacer-taintimeframecanprovidethecriticalinitialdefectsizebybackcalculation,assumingaparticulardesign life.Thecritical initialde-fectsizeshouldnotbeexceededatthebegin-ningoftheperiodunderreview.Thecriticalsizeofcracksandcrack-likedefectsprovidesimportant information for the specificationof pipeline inspection tools, which need todetectand identify thedefects, (whentheyhaveachievedacriticalsize),withahighre-liability.

Within the NATURALHY project, criticaldefect sizes for typical caseswere investi-gated in sensitivity studies. Furthermore, atoolabletocalculatetheprobabilitythatapipelineoradefect(crackandcorrosion)willfailorleadtofailurewasdeveloped.BasedontheresultsofthesensitivitystudiesandtheProbablilityOfFailure(POF)calculations,requirementsforin-lineinspectiontoolsweresummarised. In a large scale test adaptedtoolswereexaminedtoprovewhethertheymet the more stringent requirements. The

Pipeline Integrity Assessment Tool

Clock Spring repair of a steel pipeline

6 Whatmeasuresshouldbetakento

controlandmonitortheconditionofthenetwork?

1MagneticFluxLeakage(MFL)2TRIAXsensorsareusedintheMagneScanTMtool(abletodetectcorrosionandlongaxialdefects)3ElectroMagneticAcousticTransducer(EMAT)

15

resultssuggestedthatmodifiedinspectiontoolssuchasMFL1,TRIAX2andEMAT3canbeappliedinorderto inspectgaspipelinescontainingnaturalgas/hydrogenmixturesandfindcriticaldefects.Byusingin-lineinspectionandPOFcalculationresults,theintervalsforpipelineinspec-tionactivitiescanbedeterminedfordifferenthydrogenconcentrations,loadsandgeometriesofpipelinesanddefects.Itisexpectedthatinspectionintervalswillbeshortenedincomparisontothenaturalgasservice,especiallyforhigherhydrogenconcentrations.Asacountermeasuretheimprovementofinspectiontoolperformancecanoffermitigation,asearlydetectionandreliablesizingofdefectsisbeneficialforloweringtheprobabilityoffailure.

Afterhaving identifieddefects,anoptimisationprocessofactionshasbeenproposed inordertoreducethecostsbutstillmeettherequiredsafetylevels.Calculationsofnetpresentvaluehaveshownthat,dependingontheamountanddistributionofdefects,thecostsforrepairand renewal can be reducedsignificantly by grouping ac-tivitiestogether.

Concerning pipeline re-pairmethods, three currentlyappliedprocedureshavebeeninvestigated regarding theirsuitability for hydrogen ser-vice.Theworkfocusedontheabililtyoftherepairmeasureto take on the pipeline loadand on the effect of hydro-gen on welding activities.Theinvestigatedrepairmeth-ods (“Clock Spring”, “MetallicSleeve” and “Weld Deposit”)were found to be suitablefor repairing hydrogen-con-tainingpipelineseventhoughperformancewas slightly re-ducedinsomecases.

Finallytheeffectofaddinghydrogenonthecostsof integritymanagementhasbeenin-vestigated.Thecostsarestronglydependentonindividualcircumstances,especiallyregardinghydrogen concentration, defect distribution,material properties, loads and integrity targets.Anexamplewaselaboratedusingmaterialdataondefectdistributionswhichreflectpipesina"mediumcondition",withamaximumoperationpressureof66barsandmeetingaPOFintegritytargetforcorrosionandforcracksafter50yearsofoperationwhichisinlinewithcurrentfailurestatisticsforEuropeannaturalgastransmissionpipelines.Withtheexampleconsidered,itwasconcludedthat,forhighconcentrationsofhydrogen(50%)innaturalgaspipelines,therewereslighteffectsontheinspectionandrepairfrequencyandthereforeincreasedtotalcosts(inspec-tionandrepairforcorrosionandcracks)intheorderoflessthan10%.

Summarisingtheresultsoverall,itcanbestatedthat,basedontherelevantdata,appropri-ateandaffordablepipelineintegritymanagementcanbeputinplaceforthetransportationofnaturalgasandhydrogenmixturesuptoahydrogenconcentrationof50%.

General flow chart of the integrity management cycle (source: Report "Integrity Management and the Naturalhy Project")

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The existing gas pipeline networks are de-signed,constructedandoperatedbasedonthepremisethatnaturalgasisthematerialtobeconveyed.Thesafetyofthepipelinesystemand the riskposed to thepublicby thesupplyanduseofnaturalgasarewellunderstood,andconsideredacceptable,aftermanyyearsofop-erationalexperienceandmuchresearchintotheeffectsofaccidentalescapes.

However, hydrogen has different chemicaland physical properties which may adverselyaffect(increase)theriskpresentedtothepub-lic. Risk is a combination of likelihood of anuntoward event (such as failure frequency ofpipelinesorignitionprobability)andtheconse-quence (hazard) of the event (such as the se-verityofa fireorexplosion).Addinghydrogento the gas infrastructuremay affect both thelikelihoodandseverityofuntowardeventsandhencepotentiallyincreasetherisktothepublic.TheNATURALHYprojecthasfocussedeffortonquantifying this effect in order to establish iftheriskremainsacceptableandtoidentifythemaximumhydrogen concentration that canbeadded to thenaturalgaswithout this riskbe-comingunacceptablyhigh.

Tore-assesstheseverityofthehazardpre-sented by accidental releases of natural gas/hydrogen mixtures, NATURALHY has studiedexperimentally,atlargescale,thebehaviourofgasescapesandexplosionsinbothadomesticand industrial settingandassessed theeffectofincreasinglevelsofhydrogenaddition.Thesestudiesestablishedthatescapesofnaturalgas/hydrogenmixtureswithinbuildingsbehaveinasimilarwaytonaturalgas,intermsofthena-ture of the accumulation produced. However,the gas concentration and volume of the ac-cumulationincreasesashydrogenisaddedbuttheseincreasesareslightforhydrogenadditionup to50%by volume. In theeventof ignitionofagasescapewithinabuilding,theexplosionpresents a hazard to theoccupants.Here, theworkoftheNATURALHYprojecthasshownthattheseverityofexplosionsinbuildingsincreasesif hydrogen is added to natural gas.However,theincreaseisonlyslightforhydrogenadditionof20%.

7 Whatistheimpactofaddinghydrogentonatural

gasonthesafetyaspects?

Thermal image of flame

Working on the test rig

17

Theclosestcontactthatthegeneralpublichaswiththegassupplysystemisintheirhomes,ascustomers,usingthegasforheatingandcooking.Itisimpossibletopreventallgasescapesandcurrently,asmallnumberofexplosionsoccureachyearasaresultofgasescapesindomes-ticproperties.Hence,thefrequencyofsuchexplosionshasbeenre-assessedfornaturalgas/hydrogenmixtures.Thisanalysishassuggestedthattheexplosionfrequencycouldincreasebyuptoafactorof2asaresultofadding20%byvolumehydrogentonaturalgas.However,thecurrentriskisverylowandevenwiththisincreasetheriskremainswithingenerallyacceptablelimits.

From thepoint of viewof thepipelineoperator, themain concern is theassessmentofthe risk that their operations present to the public at large, from the pipeline network andfrom their gasprocessing sites, including compressoror pressure reduction stations.Hence,operatorsneedamethodologywhichwillenablethemtoas-sesstheserisksfollowingtheaddition of hydrogen to thepipeline network. The princi-pal hazard posed by the fail-ure of transmission pipelinesis thatofa large fire.Hence,NATURALHY has re-assessedthishazardfornaturalgas/hy-drogen mixtures by conduct-ing large scale experimentsanddevelopingamathemati-calmodeltoevaluatethefirehazard.Usinginformationob-tainedwithintheNATURALHYprojectoftheeffectofhydrogenonpipelinematerials,thefailurefrequencyoftransmissionpipelinesconveyingnaturalgas/hydrogenmixtureswasre-assessed,anditwasconcludedthat,withappropriateintegritymanagementofthefatiguelife,thefailurefrequencyoftransmissionpipelineswouldnotbeadverselyaffectedtoanygreatextent.

Bycombiningtheworkonfailurefrequency,ignitionprobabilityandtheassessmentoffirehazard,NATURALHYhasdevelopedaneasytousescreeningtool (LURAP4)whichwillenableoperatorstoassesstheriskposedbythetransmissionofnaturalgas/hydrogenmixturesandcompareitwithcurrentrisklevels.LURAPdetermines,theriskposedbyanindividualpipelinetoapersoncloseby,oranentirenetworkofpipelinestothepopulationasawhole.TheresultsfromLURAPsuggestthattheadditionofhydrogenincreasestherisktoanindividualatloca-tionsnearthepipelinebutdecreasestheriskat locationsfurtheraway(astheextentofthehazardousregionisreduced).

Finally,pipelineoperatorsalsoneedtoassessthebackgroundlevelof leakagefromtheirpipelinenetworksaspartoftheirintegritymanagementandenvironmentalassessments,sincemethaneisagreenhousegas.Astudyoftheexpectedbackgroundlevelof‘leakage’fromthegassystem(throughminordefectsinthepipelinesorbypermeationthroughthepipelinematerial)hasshownthatthelevelofleakageoverallisverysmallandposesnohazardfromasafetypointofview. Indeed,theadditionofhydrogenresults inaslightdecreaseinthe levelofmethaneemissionstotheatmospherefromthegasinfrastructure,whichisbeneficialfromanenviron-mentalperspective.

4LURAP:LoughboroughUniversityRiskAssessmentofPipelines.AvailablewithintheDST

VCE Test Rig

18 19

Withincreasinghydrogenadditiontothe natural gas supply, the physi-

calcharacteristicsandbasiccombustionproperties of the fuel will be modified,which, in turn,couldalter theoperation,reliability and safety of appliances. Fordomesticappliances,personalhealthandhomesafetyareatstakeandtensofmil-lions of appliances in anygiven countryare involved. Furthermore, importantdata on appliances (types, years in use,maintenance record etc.) in use in eachhouseisquitelimited.Thus,whileallma-jor classes of end-use equipment havebeenconsideredintheNATURALHYproj-ect,particularattentionhasbeenpaidtodomesticappliances.

Current fundamental understandingofcombustionprocessesopens thewaytoanalysetheconsequencesofintroduc-ing new distribution gases like naturalgas/hydrogen mixtures by performinga limited number of basic combustioncalculations and experiments instead oflarge numbers of appliance tests. Thisfundamental analysis can be performedforthegascompositionsrelevanttoanynational situation, in a straightforwardand quantitative way5. Consequently, ithasbeenpossibletoconsiderthe“essen-tial” consequencesof hydrogenadditioni.e., those causing safety and reliabil-ity issues (such as light-back in domes-tic appliances, overheating of industrialburners, engine knock in gas enginesetc.), fitness-for-purpose (thermal inputto, and efficiency of, combustion equip-ment)andenvironmentalissues(suchasconsequences for emissions of nitrogenoxides).Onepracticalaspectthathasnotbeen considered is the life-long physi-calintegrityofgasutilizationequipmentsince all current end-use equipment hasbeen designed, tested and approved fornaturalgasandnotmixturescontaininghydrogen.

5 Method developed by Gasunie Engineering &Technology,Groningen,TheNetherlands

Whatistheimpactofadding

hydrogentonaturalgasonenduser

aspects?

8

19

There isoneeffectofhydrogenadditionontheperformanceofcombustionequipmentthat must be emphasised. Taking a givennaturalgasand“simply”addinghydrogentoitwill decrease theWobbe indexof thegas,up to hydrogen fractions in excess of 80%.Sincethethermalinput(power)togasutiliza-tionequipmentisdirectlyproportionaltotheWobbeindex,thethermalinputwilldecreasein all combustion equipment, except thosewith power controls (such as power genera-tionequipment).

It isanticipated that, for the timebeing,natural gas distribution will continue withintheexistingdistributionbands,asdefinedbyarangeofWobbeindexvalues.InthecontextoftheeffectofhydrogenadditionontheWobbeindex,thisfactitselfconstrainsthemaximumallowablehydrogenfraction:theWobbeindexofagivennaturalgas/hydrogenmixturemustremainabovethatofthelowerWobbelimitoftheexistingband.

Fromthiswork,thefollowingconclusionsweredrawn:

the maximum hydrogen concentra-tion for thedomesticmarket ina country isdeterminedbythesafeoperationofproperlyadjustedconventionaldomesticappliancesaswellasbythelocalconditionsofnaturalgasquality(rangeandcurrentvalueofWobbeIn-dex)

forproperlyadjustedappliancesandfavourable conditions of natural gas quality,conventionaldomesticappliancescanaccom-modateupto20%ofhydrogen

forpoorlyadjustedappliancesand/orunfavourableconditionsofnaturalgasquality,nohydrogenadmixtureisallowed

stationary gas engines and gas tur-binesneedreadjustmentand/ormodification

feedstock processing and industrialcombustionapplicationsrequirecase-to-caseconsideration.

Concept for a hydrogen household fuel cells. AA (R6) battery with large compartment filled with bubbling water

Blue flames from gas stove burner. Closeup shot of blue flames from a kitchen gas range

20 21

Theuseoftheexistingnaturalgasnetworktodis-tributehydrogenprovidestheopportunitytocre-ate local “hydrogen centres” by developing separa-tion technologies toprovidehydrogenforendusers.Separation of hydrogen is amature technology andinrefineries, isusuallycarriedoutbypressureswingadsorption (PSA) technology.However, thesetendtorequire large scale units which work best with highlevels(greaterthan50%)ofhydrogeninthefeedgas.Thereisarequirementforsmallerscaleseparationofhydrogen,andwhenthemixturecontainslowerlevelsofhydrogeninthefeedgasundertypicalnaturalgaspipelineconditions.Hydrogenqualityisanimportantissue for end-use and hydrogen purity needs to bematchedtothespecificapplication.

TheNATURALHYprojecthasfocussedondevelop-ingadvancedhydrogen-selectivemembranes for theseparation of hydrogen from natural gas/hydrogenmixtures.Membranesareessentiallyselectivemolecu-larfiltersandoperateunderapartialpressuredrivingforce, so that thehigher thepartial pressurediffer-enceandtheconcentrationgradientofhydrogen,themoreefficienttheseparation.Thefocushasbeenon:

laboratorydevelopmentofthinpalladiumbasedmembranesforobtainingpurehydrogen

developingcarbon-basedmembranesthatoper-ateatlowtemperaturesandwithhighselectivity

producing a conceptual design for a “hybrid”membrane separation system comprising a carbonmembrane first stage followed by a palladium alloymembraneforuseina100m3/hrhydrogenrefuellingstation(seefigureonthispage).Thissystemexploitsthe advantageous properties of each type ofmem-branesoastooptimiseoverallperformance

carryingoutacostanalysisof themembranesystem and benchmarking performance and costsagainstcommercialPSAsystems.

Currently commerciallyavailable palladium mem-branes are conventionally“thick” tubular membranesandareveryexpensive.TheNATURALHY approach hasbeen to prepare extremelythinmembranes both to in-crease flux and to reducecosts. Efficient palladiummembranes have been de-

Conceptual membrane separation scheme for NATURALHY

Separationofhydrogen

fromahydrogen/naturalgasmixture,anditsimpactonthequality

oftheremaining

gas

9

21

velopedusingelectrolessplatingtoproduce3µmthickmembranes, while magnetron sputtering has beenusedtodepositthinpalladium/silveralloymembranesonto smooth uniform substrates. These membranesoperateat300oCwithgoodhydrogenflux,highrecov-eryand100%selectivityforhydrogen.Carbonbasedmembraneshavebeenproducedbypyrolysinghemi-cellulose.Thesemembraneshavebeenshowntohavegreaterpermeabilitywithbetterselectivity(upto98%)than conventional polymericmembranes; in additiontheyoperateattemperaturesbetween30oand90oC.

Bycombiningthebestcharacteristicsofeachofthesemembranes intoahybrid scheme, it hasbeenpossibletoobtainanincreaseinefficiencyandflex-ibility together with lower costs for separation. De-pendingonprocessconditionsthecarbonmembranecandeliverup to98%purehydrogen,while thepal-ladiummembrane delivers pure hydrogen. Thus, thesystemcanprovidedifferenthydrogenspecificationsdependingonenduserrequirements.Byusingthecar-bonmembrane,mostoftheseparationiscarriedoutat almost room temperature and, subsequently, thefeedtothepalladiummembranehasveryhighhydro-gencontent,therebyimprovingthedrivingforceandreducing,substantially,thepalladiummembranesur-facearearequired.

Analysis of costs shows that the hybrid system,includingancillaries,ispotentiallycheaperthansepa-rationbyPSA.SmallscalePSAsystemsarecurrentlyunderdevelopment.However,aswithallPSAsystems,separating hydrogen from streamswith a hydrogencontent less than 40% is problematic and requiresadditional facilities; the options are two PSA unitsinseries,or,acarbonmembrane(aswiththehybridconcept)toconcentratethehydrogenlevelinthefeedbeforethefinalPSAunit.

Gasquality issueshavebeenconsidered,both inthecaseofaddinghydrogentothenaturalgasnet-workandalsotheeffectondownstreamgasqualityashydrogeniswithdrawnbyendusers.Inascenariowhere, for example,25%hydrogen isadded, by vol-ume, tonaturalgas,endusersatdifferentpoints inthenetworkmaytakeouthydrogenatdifferentquan-titiesandqualities.Thiswillhaveaneffectonthegasquality of the remaining natural gas/hydrogen mix-ture, although analysis shows that the downstreamgas quality will not be adversely affected since theWobbeindexandheatingvaluewillnotbeoutsidethestatutoryrequirements.

Packaged separator module integrating the membranes & heat-ing system, and showing the internal flow pattern

Pd membrane laboratory test module

Hollow fibre carbon membrane

Pd thin film membrane supported on tubular ceramic substrate

Electron micrograph showing commercial ceramic support with defects and the effect of applying more uniform porous

ceramic layer

22 23

The NATURALHY project deliversa massive amount of informationon the economics, societal and en-vironmental aspects of transportinghydrogenoveranaturalgastransmis-sion network and on awide range ofmaterials’propertiesandbehaviour,onseparation membranes performanceandcostsforseveralenduserapplica-tions,suchasindustrialendusers,fill-ingstations, etc., onpipeline integrityand on gas transport network safetyperformance when carrying amixtureofhydrogenandnaturalgas.

The NATURALHY DST (DecisionSupportTool) hasbeendevised inor-der to enable a natural gas pipelineoperatortoperforma"what-if"analy-sisonwhathappenstoaspecificGasTransportNetwork(GTN)whenspecifichydrogenpercentagesaretransported.TheDST is a PC-based software toolwhichenablesacompanytointroduceaconfigurationlayoutofaspecificgastransportnetworkorsectionofanet-workandevaluatetheconsequencesofadding hydrogen and compare itwithanyotherconfigurationoveranumberofactiveyears.

ItmustbestressedthattheDSTisfocusedonanoverallandgeneraltypeofanalysisandnotonreplacing,forin-stance,commerciallyavailablepipelineintegrity management systems whichcarryout integrityanalysis toamuchgreater levelofdetail. Inaddition,theconsiderableamountofdetailedinfor-mation on actual pipeline conditionsandbehaviourthatisrequiredinordertoenableamorethoroughanalysis iseithersimplynotavailableatgascom-panylevelorrequiresadatacollectioncostthatisnotacceptableforthere-sultingincreaseinaccuracy.

TheDSThastwomainuses:toin-form, through its Information Reposi-tory, theexpectedmaterialanddevicebehaviourwhen certain hydrogen per-

10 Howtoassessaspecificnetworkforthe

NATURALHYconcept:the

DecisionSupportTool

23

centagesareappliedandtosimulate,usingits"what-if"analysiscapabilities,theactualpipelinedegradationbehaviourovercertainperiodsoftimewiththeoptionofapplying,onthepipelinemodel,mitigationmeasures.Thus,theNATURALHYDSTkeygoalsareto;

enableediting,analysisandannotationofapipelinenetwork,sorelevantinformationmaybefoundandextractedatlaterstages

computeacomprehensive"what-if"analysisofapplyingdifferentlevelsofhydrogeninthenetwork.

Theabove-mentionedanalysiscomprisesriskassessment,costassessment,evaluation,andproposalofrules,guidelinesandproceduresthatwillmitigatetheexpectedincreaseofriskand/orcostswhenapplyingthegasmixturetothepipelinenetwork.

TheGTNsub-formisprovidedtoenabletheusertolayoutacompleteGTNusingacompre-hensivetoolboxprovidedbytheDST.

TheDSTisabletodrawamapoftheGTNsotheusermayactuallyseeinthelayoutwheresectionscrosspopulationareasandestablishmoreaccurateriskdistances (e.g.proximitytopopulationdensities).

TheDSTpresentsseveral "dashboards", for lifecycleandsocio-economicassessment, forsafetyandforintegrity.Withtheexceptionofthelifecycleandsocio-economicassessment,allanalysesaretimedependentandshowtheevolutionoftheGTNpropertiesovertime.

EachofthedashboardsdisplaysaspecificanalysisthatiscarriedoutbytheNATURALHYDST.ItisthroughthedashboardsthatcomparisonsbetweenaGTNwithorwithouthydrogencanbeperformed.TheDSTisextremelyflexibleandisabletocarryoutGTNsimulationandcomparisonofanytwoconfigurationsoveraperiodofupto50years,yieldingcost,safetyandintegritycalculationsforallselectedsections.

Typical configuration of a Gas Transport Network (GTN)

24 25

The potential benefits of adding hydrogenhave been addressed in the NATURALHYProject through life cycle and socio-economicassessment. This has involved establishingstandardproceduresforcalculatingvariousen-vironmental impacts, economic costs and em-ployment implicationsofexistingandpossiblefutureenergysystems.Inparticular,thesepro-ceduresdetermineprimaryenergyinputs(asin-dicators of energy resource depletion), carbondioxide, methane and nitrous oxide emissions(asprominentgreenhousegasemissionsasso-ciatedwithglobalclimatechange),sulphurdiox-ide,oxidesofnitrogenandparticulateemissions(aspollutantsaffectingurbanairquality),inter-naleconomiccosts,anddirectandindirectjobsin theEuropeanUnion.Byadoptingasystem-aticandtransparentapproachtothesecalcula-tions, ithasbeenpossibletoquantifybenefitsandcommunicatetheminaconvincingmanner.

The startingpoint for thisworkwasa re-view of life cycle and socio-economic assess-ment studies at the beginning of theNATUR-ALHYProject.Subsequently,astandardformatforcalculationswasdevised,basedonMSExcelworkbooks, and an associated guidewas pre-pared.Fromthis,workbooksforrelevanttech-nologies were assembled both as stand-alonefiles and for incorporation into the DST. Themostimportantworkbooksarethosewhichde-scribetheexistingnaturalgasnetworkanditsoperation with the addition of hydrogen. Theworkbooksfortheexistingnaturalgasnetwork

11 Whataretheoverallbenefitsofadding

hydrogentonaturalgas?

Breakdown of Energy, Emissions, Jobs and Costs per Unit Output of Natural Gas Network Operation for Large Users

25

wereneededtoprovideabaselineagainstwhichtheadditionofhydrogencouldbecomparedintermsofrelativechangesinenvironmentalimpacts,economiccostsandemploymentimpli-cations.Outputsaregeneratedinnumericalandgraphicalformats,givingabsolutevaluesandrelativecontributions,forexampletonaturalgasdeliverybythenetworktolargeusers(seethefigureinpage24).

Theworkbooksfortheexistingnaturalgasnetworkcoverthesupplyofnaturalgas,andtheconstruction,operationandmaintenance,anddecommissioningofthenetwork.Theactualde-tailsoftheseworkbooksarebasedonapracticalbalancebetweenappropriaterepresentationofarealnaturalgasnetworkanddemandsonuserdatainputrequirements.Inparticular,thecomponentsofanaturalgasnetworkhavebeensimplifiedintoatransmission(highpressure)system(withheadstations,pipes,compressorsandstoragefacilities),aregionaldistribution(mediumpressure)system(withpipesandlargepressurereductionfacilities),andalocaldis-tribution(lowpressure)system(withpipes).Aspectsofthesesystems,suchasdifferentpipelengths,diameters,wall thicknessesandtypicalmaterials,canbevariedtosimulateexistingnetworks.Bothdesigndetailsanddefaultvalueswereprovidedfortheseworkbooksbygasutili-tieswhichwereNATURALHYProjectpartners.

Theworkbookwhichdescribestheoperationofnaturalgasnetworkswiththeadditionofhydrogenwasassembled using results generated by otherNATURALHYproject activities. In

Total Greenhouse Gas Emissions for Hydrogen Production

Total Greenhouse Gas Emissions for Hydrogen Delivery by Truck, Dedicated Pipeline and the Existing Natural Gas Network (NATURALHY approach)

26 27

particular,theprocedureforadjustingleakagesfortheadditionofhydrogenwasprovidedbystudiesconductedonsafety,incorporatingsomeoftheresultsfromresearchondurability.

Crucialinformationontheeffectsofhydrogenonthefrequencyofinternalpipeinspectionsandsubsequent repairswassupplied fromactivitieson integrity.Thesourceofessentialperformancedataonhydrogenseparationtechnologiesandtheeffectofhydrogenonappli-ancesderivedfromresearchonend-use.

Inordertocompleteanalysisofpotentialbenefits,itwasalsonecessarytoaddevalu-ationofmethodsforproducinghydrogen.Forconvenience,thiswasachievedbycreatingaLibraryofResultswhichincludedavailabledataonavarietyofdifferenthydrogengenerat-ingtechnologies.Thisenablescomparisonofresultssuchastotalgreenhousegasemissions,measuredinequivalentcarbondioxide,forarangeofhydrogenproductiontechnologieswiththeemissionsfactorsfortheconventionalsupply,deliveryandcombustionofnaturalgasbydifferentusers(boundedbythepinkdottedlinesasillustratedinthefirstfigureofpage25).

Specificdetailsofthesourceofhydrogen,whereitisinjectedintotheexistingnaturalgasnetwork,andwhetherandhowitisseparatedfromthesubsequentmixturedeterminetheoccurrenceandmagnitudeofbenefits.

Theadditionofhydrogentonaturalgascanmakeasignificantreductionintotalgreen-housegas emissions if thehydrogen is sourced fromcertain formsof biomass (forestryresidues,strawandmiscanthus),windpower(bothonshoreandoffshore)andnuclearpower.Dependingoncircumstances,hydrogenproductionfromfossilfuelswithcarboncaptureandstoragealsoofferssomeadvantages.However,reductions intotalgreenhousegasemis-sionswiththesesourcesofhydrogenaregenerallylower.Additionally,theremaybenoben-efitsintermsofdecreasedprimaryenergydemandorenergyresourcedepletion,althoughimplicationsforenergysecurityaregovernedbythelocationofthesesourcesoffossilfuels.Potential benefits of extractinghydrogen from themixturedependon theactual perfor-manceoftheseparationtechnologyandthesubsequentuseofthehydrogen(includingitsrequiredpurity)andtheresidualgas(whichstillcontainssomehydrogen).However,overallairqualitybenefits(especiallylowersulphurdioxide,oxidesofnitrogenandparticulateemis-sions)canarise ifhydrogen issubsequentlyused intransportationanddisplacesconven-tionaldieselfuel.Aswiththeso-called“greeningofgas”,therelativebenefitsofdeliveringhydrogen,sayforuseinroadvehicles,dependsonthevariousconsiderations,especiallytheoriginalsourceofhydrogen.

Change in Total Greenhouse Gas Emissions for Natural Gas/Hydrogen Delivery to Large Users

27

Concludingremarks 12

Gas flame inside the gas boiler

NATURALHYhasbeena significant project,withconsiderabletimeandeffortdedicated

totestingandproductionofwhatisavastarrayofdata,muchofitcompletelynew.Itisalmostimpossibletosummarisetheprojectinashortspaceand,infact,unfairtodoso.Indeedcaremust be taken in looking at summary resultsfromthisprojectandjumpingtosimpleconclu-sions.

Thedataareoftencomplex,withmanypro-visos,giventheimmensityofwhathasbeenat-temptedand,ingeneral,successfullyachieved.Thereader is, thereforeurgednot tograspatwhat looks like a favourable or even an unfa-vourableresult,withoutadeeperanalysisofthespecificsystemunderconsideration.

Nevertheless,someattemptmustbemadeto condense the key findings of NATURALHYproject. And, whilst they are presented below,theyshouldbe readwhilebearing inmindthequalifyingremarksoutlinedpreviously:

1. Withregardtopipelinedurability,resultsshowthateffectsonpipematerialsusedinthenaturalgasgrids, causedbyhydrogen, canbemitigated by appropriatemeasures. Modifica-tionstomaintainasafeandreliablesupplyofcustomerswithnaturalgas/hydrogenmixtureswillmainlybenecessaryforthetransportationpipelines made of steel, but importantly, no"show-stoppers"havebeenidentified.

2. Considering integrity, the material in-vestigationsrevealedthatadditionalmeasureswillberequiredtoensuretheintegrityofsteelpipelines,whenhydrogenistransportedbytheexisting natural gas system. Consequently thepipeline integritymanagementsystems(PIMS)inplaceneedtobeadapted.ModificationswillbenecessaryforwideraspectsoftheexistingPIMSasdefectsthatarecurrentlynotthecen-treofattentionneedtobeconsidered,whenhy-drogenistransported.Summarisingtheresultsoverall,appropriatepipeline integritymanage-mentcanbeput inplace topermit the trans-portationofnaturalgasandhydrogenmixtures.

3. Itwasanticipatedthataddinghydrogento the gas infrastructuremay affect both thelikelihoodandseverityofuntowardeventsand,

28 29

hence,potentiallyincreasetherisktothepub-lic. Inthisregard,theNATURALHYprojecthasestablished:

that escapes of natural gas/hydrogenmixtures within buildings behave in a similarway to natural gas, in terms of the nature ofthegas/airmixtureproduced.However,thegasconcentrationandvolumeoftheaccumulationincreases as hydrogen is added but these in-creasesareslight forhydrogenadditionup to50%byvolume

withinbuildings,severityofexplosionsincreases ifhydrogen isadded tonaturalgas.However, the increase isonlyslight forhydro-genadditionupto20%.Analysishassuggestedthattheexplosionfrequencycould increasebyuptoafactorof2asaresultofaddingupto20%byvolumehydrogentonaturalgas.How-ever,thecurrentriskisverylowandevenwithdoubling the risk remainswithin generally ac-ceptablelimits

fromthepointofviewofthepipelineop-erator,theprincipalhazardposedbythefailureoftransmissionpipelinesisthatofalargefire.Results suggest that theadditionofhydrogenincreasestherisk toan individualat locationsnearthepipelinebutdecreasestheriskatloca-tionsfurtheraway,astheextentofthehazard-ousregionisreduced

pipeline operators need to assess thebackgroundlevelofleakagefromtheirpipelinenetworks,sincemethaneisagreenhousegas.Astudyoftheexpectedbackgroundlevelofleak-agehasshownthatthelevelofleakageoverallisverysmallandposesnohazardfromasafetypointofview.Indeed,theadditionofhydrogenresultsinaslightdecreaseinthelevelofmeth-aneemissionstotheatmospherefromthegasinfrastructure,whichisbeneficialfromanenvi-ronmentalperspective

4. Fordomesticappliances,personalhealthandhomesafetyareatstakeandtensofmil-lions of appliances are involved in any givencountry;asaconsequence,particularattentionhasbeenpaidtodomesticappliancesanditisimportanttonotethat

themaximum hydrogen concentrationforthedomesticmarketinanycountryisdeter-

29

minedbythesafeoperationofproperlyadjustedconventionaldomesticappliancesaswellasbythelocalconditionsofnaturalgasquality(rangeandcurrentvalueofWobbeIndex)

for properly adjusted appliances andfavourable conditions of natural gas quality,conventional domestic appliances can accom-modateupto20%ofhydrogen

forpoorlyadjustedappliancesand/orun-favourableconditionsofnaturalgasquality,nohydrogenadmixtureisallowed

stationarygasenginesandgasturbinesneedreadjustmentand/ormodification

feedstockprocessingandindustrialcom-bustionapplications requirecase-by-casecon-sideration.

5. Gasqualityissueshavebeenconsidered,bothinthecaseofaddinghydrogentothenatu-ralgasnetwork,andalso theeffectondown-stream gas quality as hydrogen is selectivelywithdrawnbyendusers.Inascenariowhereendusersatdifferentpointsinthenetworkmaybetakingouthydrogenatdifferentquantitiesandqualities,therewillbeaneffectonthegasqual-ityoftheremainingmixture.However,analysisshowsthatthedownstreamgasqualitywillnotbe adversely affected since the Wobbe indexandheatingvaluewillnotbeoutsidethestatu-toryrequirements.

6. TheDecisionSupportTool(DST)hastwofunctions:toinformwhatisexpectedinmate-rialanddevicebehaviouratparticularhydrogenpercentages;andtosimulate,usingits"what-if"analysis,theactualpipelinedegradationbehav-iourovercertainperiodsoftime.

The analysis comprises risk assessment,cost assessment, evaluation, and proposal ofrules,guidelinesandproceduresthatwillmiti-gatetheexpectedincreaseofriskand/orcostswhenapplying thegasmixture to thepipelinenetwork.

It also provides a comprehensive toolboxthatenablestheusertosimulateaGasTrans-portNetwork(GTN)toenablecomparisonsbe-tweenaGTNwithorwithouthydrogenaddition.TheDSTisextremelyflexibleandisabletocarryoutGTNsimulationandcomparisonofanytwo

Gas Wellhead

Natural gas pump and distribution station

Silver Gas Plant Towers

Three natural gas burners with bright blue flames inside an operating gas furnace

configurationsoveraperiodofupto50years,yieldingcost,safetyand integritycalculationsforallselectedsections.

7. The potential benefits of addinghydrogentothenaturalgassystemhavebeen addressed by life cycle and socio-economic assessment and it has beenpossible to quantify benefits. However,the following conclusionsare, necessar-ily,qualitative:

theadditionofhydrogentonatu-ralgascanmakeasignificantreductionintotalgreenhousegasemissionsifitissourced from certain forms of biomass(forestry residues, straw and miscan-thus),windpower(bothonshoreandoff-shore)andnuclearpower.Dependingoncircumstances,hydrogenproductionfromfossilfuelswithcarboncaptureandstor-age(CCS)alsoofferssomeadvantages.However,reductionsintotalgreenhousegasemissionswiththesesourcesofhy-drogenaregenerallylower

potentialbenefitsofselectiveex-tractionof hydrogendependon theac-tualperformanceoftheseparationtech-nology and the subsequent use of thehydrogen (including its required purity)andtheresidualgas(whichstillcontainssome hydrogen). However, overall airqualitybenefits(especiallylowersulphurdioxide, oxides of nitrogen and particu-late emissions) can arise if hydrogen issubsequentlyused intransportationanddisplacesconventionaldieselfuel

theadditionofhydrogencanbean effective means of "greening" natu-ral gas so that the mixture is used di-rectly in existing appliances for heatproduction and electricity generation.With this option, the potential benefitsare mainly as a practical measure formitigatingglobalclimatechangeandin-creasing energy security, depending onthe original source of the hydrogen.

30

Project Co-ordinatorN.V. Nederlandse Gasunie

Work Package Leaders:University of Oxford, GDF SUEZ, Loughborough University, DBI-GUT,Instituto de Soldadura e Qualidade (ISQ), GERG - The European Gas Research Group, EXERGIA

Other Project Partners:BP Gas Marketing, Centro Sviluppo Materiali (CSM), Cogen Europe,Commissariat à l’Energie Atomique (CEA), Compagnie Européenne des Technologies de l’Hydrogène (CETH), Computational Mechanics International (CMI), Danish Gas Technology Centre (DGC),TNO Science & Industry, Ecole Nationale d’ingenieur de Metz (ENIM), Energy Research Centre of the Netherlands (ECN), General Electric PII, UCB Högskolan i Borås, Institut Français du Pétrole (IFP), Istanbul Gas Distribution (IDGAS),National Grid, National Technical University of Athens (NTUA),Naturgas Midt-Nord, Nederlands Normalisatie-Instituut (NEN),Norwegian University of Science and Technology (NTNU),Planungsgruppe Energie und Technik (Planet), Hellenic Gas Transmission System Operator (DESFA),SAVIKO Consultants, Shell Hydrogen, SQS Portugal, Statoil,Technical University Berlin, The Health and Safety Executive (HSE), Total,Turkish Scientific and Technical Research Council (TUBITAK), University of Leeds, X/Open Company Ltd

NATURALHYisanIntegratedProjectfundedbytheEuropeanCommission’s

SixthFrameworkProgramme(2002-2006)forresearch,technologicaldevelopment

anddemonstration(RTD)