Guidelines for the Use of Metocean Data Through the Life Cycle of A
© COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED P Hodgetts A Saulter W Cooper development renewable energy life cycle ofamarine London,2008 throughthe metocean data Guidelines for theuseof CIRIA C666 WEBSITE www.ciria.org FAXEMAIL [email protected] 02072530523 TELEPHONE 02075493300 Classic House,174–180 OldStreet,LondonEC1V9BP SeaRoc UKLtd Met Office ABP MarineEnvironmental Research Ltd © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED ii Published by CIRIA, Classic House, 174–180 Old Street, London, EC1V9BP Published byCIRIA,ClassicHouse,174–180OldStreet,London, ISBN-13: 978-0-86017-666-4 RP742 A cataloguerecordforthisbookisavailablefromtheBritishLibrary. ©CIRIA2008 British LibraryCataloguinginPublicationData C666 CIRIA Cooper, W, Saulter, A,HodgettsP energy development Guidelines fortheuseofmetoceandatathroughlifecycleamarinerenewable and identifiestheimportanceforgooddatamanagement. metocean issues.Thedocumentincludesareviewofdatatypes,sources consultants andotherkey stakeholders whowillbenefit fromawiderappreciationof reference toinformprojectdevelopers,engineers,marinesurveyors,environmental through thelifecycleofamarinerenewableenergy developmentandserveasahelpful This guidehasbeendevelopedtoidentifyandrecommendusesofmetoceandata for survivabilityoftheprojectandstrategymaintenanceaccessibility. serve tocharacterisetheavailableresourceforenergy yield,thedesignrequirements fundamental tothesuccessofallmarinerenewableprojectsasthisinformationwill A goodunderstandingofmetocean(meteorologicalandoceanographic)datais Summary for moredetailsoncopyrightterms andcharges at: CIRIA publicationforuseinother documentsorpublications,pleasecontactthePublishingDepartment ortechnicalinformationfromthisanyother If youwouldlike toreproduceanyofthefigures,text obtained beforeanypartofthispublication isstoredinaretrievalsystemofanynature. application forwhichshouldbeaddressed tothepublisher. Suchwrittenpermissionmustalsobe means, includingphotocopyingandrecording,withoutthewrittenpermission ofthecopyrightholder, All rightsreserved.Nopartofthispublicationmaybereproducedor transmittedinanyformorby person orentitywithrespecttoanylossdamagearisingfromitsuse. provided orimplied,andtheauthorspublishershallhaveneither liabilitynorresponsibilitytoany orfitnessis been madetoensuretheaccuracyandcompletenessofpublication, nowarranty thereby engagedinrenderingaspecificlegaloranyotherprofessional service.Whileeveryefforthas covered. Itissoldand/ordistributedwiththeunderstandingthatneither theauthorsnorpublisheris This publicationisdesignedtoprovideaccurateandauthoritativeinformation onthesubjectmatter technology marine renewable Oceanographic data, Meteorological data, Reader interest Coastal andmarine,healthsafety, climatechange,energy Keywords SRClients,contractors,consultants,planners, Committee-guided,establishedknowledge USER Advice/guidance STATUS CONTENT Unrestricted AVAILABILITY Classification [email protected] stakeholders Tel: 020 75493300 CIRIA C666 . © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 ei ebSeaRocUKLtd RenewableEnergy Systems Scottish&Southern Energy E.ON Nick Bean DONGEnergy CIRIA project manager Genie Webb Ed Frost Mathilde Damsgaard TheCrownEstate Robin Burnett James Doyle Steering group Professor Mike Cowling Steering group chair Safety SteeringGroup. have beeninmarinerenewableenergy. Peter isamemberoftheBWEA Health and inoffshoreconstruction;eightofwhich mechanical engineerwith30yearsexperience Peter HodgettsisdirectorofSeaRocUKLtdandbothamastermariner Captain Peter Hodgetts member organisation oftheNationalCentreforOceanForecasting (NCOF). inoperationaloceanographyandmarineforecastingisa Office provideexpertise specialisingincoastalwaveprocesses.TheMet marine surveyandresearchexperience, Andy SaulterisanoceanographicconsultantfortheMetOffice.has15years Dr AndrewSaulter standards. Environmental Forum andtheAdHocWorking Group(AHWG)onmarinerenewable Management Technical Working Group,theOffshoreRenewableEnergy BillisalsoamemberoftheCOWRIEDataandInformation of practicalexperience. Bill CooperismanagingdirectorofABPmerandanoceanographerwithover20years Bill CooperBSc(Hons) Authors with theMetOfficeandSeaRocUKLtd. under contracttoCIRIAbyABPMarineEnvironmentalResearchLtdinpartnership metocean datathrough thelifecycleofamarinerenewables development This guidewasproducedasaresultofResearchProject742 Research contractor Acknowledgements Guidelines intheuseof , which was carried out , whichwascarried iii © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED iv h rw saeE.ON DONGEnergy Photographs Scottish &SouthernEnergy The CrownEstate This projectwasfundedby: Project funders Power Ltd. Front coverphotographskindlysuppliedbyOpenHydro GroupLtdandPelamis Wave Unattributed photographshavekindlybeenprovidedbytheauthors’organisations. CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 eoendt ..10 data Metocean 3 . .4 projects renewable marine of status Current 2 ..1 Introduction 1 . Symbols . acronyms and Abbreviations . Glossary . Tables . Figures . Boxes . Acknowledgements . . Summary Contents 3.6 Data management . .38 management Data . ..37 variability Climate 3.6 3.5 ..31 products Data 3.4 ..23 sources Data 3.3 . . .18 provenance Data 3.2 ..10 Terminologies 3.1 ..9 Summary ..7 stream Wavetidal and 2.5 . . .5 wind Offshore 2.4 ..4 standards Present 2.3 ..4 Overview 2.2 2.1 ..3 guidelines these use to How ..2 guidelines these of Structure 1.3 . . .1 limitations and Purpose 1.2 1.1 .. oeatpout . . .33 Forecastproducts 3.4.5 . ..33 atlases Metocean . . .32 3.4.4 analyses planning and Design 3.4.3 ..31 post-processing specific Site 3.4.2 . ..31 Definition 3.4.1 . . .29 Waves 3.3.3 ..27 wind Offshore 3.3.2 ..24 Watermovements 3.3.1 ..21 Origin 3.2.5 ..20 reference Spatial 3.2.4 Temporal . ..20 reference 3.2.3 ..19 Quality 3.2.2 . ..19 Ownership 3.2.1 ..13 state Sea 3.1.3 ..12 wind Offshore 3.1.2 ..10 Watermovements 3.1.1 ..vii ..vii . .viii . .ix ..xiv ..ii . .iii . .xi v © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED vi 6 Pre-consent issues ..50 issues Pre-consent 6 ..44 issues Pre-lease 5 . cycle life Project 4 1Smayrmrs. ..112 remarks Summary 11 . . .109 issues Decommissioning 10 ..103 issues Post-construction 9 ..90 issues Construction 8 ..64 issues Pre-construction 7 . eorevldto ..59 validation Resource ..58 design Conceptual 6.6 . .55 assessment impact Environmental 6.5 ..52 investigations site Initial 6.4 ..52 analysis Gap 6.3 ..50 Overview 6.2 6.1 ..49 feasibility Project ..46 selection Site 5.3 ..44 Overview 5.2 5.1 ..42 risks Project ..40 development of Phase 4.3 ..40 Technical4.2 elements 4.1 02Dcmisoig..111 Decommissioning 10.2 . . .109 Overview 10.1 ..108 Post-constructionmonitoring Performancevalidation ..107 9.4 ..105 maintenance and Operation 9.3 . ..103 Overview 9.2 9.1 ..102 monitoring Construction ..97 forecasts Marine 8.4 ..92 Construction 8.3 ..90 Overview 8.2 8.1 ..89 monitoring Pre-construction ..88 procurement and Planning 7.7 7.6 ..80 strategy maintenance and Operation 7.5 ..67 design Detailed . . .66 investigations site Detailed 7.4 . .66 conditions Consent 7.3 . .64 Overview 7.2 7.1 .. ia tem. . .63 stream Tidal 6.6.3 ..61 Waves 6.6.2 ..59 wind Offshore 6.6.1 .. ieacsiiiy. . .83 accessibility Site 7.5.3 ..81 Maintenance 7.5.2 ..80 Operations 7.5.1 ..78 analysis Downtime 7.4.3 ..74 Fatigueloads 7.4.2 . ..70 conditions Extreme 7.4.1 CIRIA C666 40 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 7.5 Example of assessing threshold conditions from wave data ..78 data wave from conditions threshold assessing of Example 7.5 Figure ..77 rose wave Example . .76 7.4 Figure diagram scatter wave Example 7.3 Figure returnperiodsignificantwaveheightscompared Predicted extreme ..65 Figure 7.2 linkages and activities Pre-construction 7.1 Figure WaveHubof ..62 concept Illustration ..60 6.4 Figure installation mast Met ..57 6.3 modelling Figure transformation wave from results Downscaling . ..51 6.2 Figure linkages and activities Pre-consent 6.1 Figure Exampleresourcemapsfromthe ..45 Figure 5.2 linkages and activities Pre-lease 5.1 Figure Schematicofworkprogrammeandknowledgetransferthrough Figure 4.1 ..30 WaveNetsites measurement 3.10 ..28 Figure Weather(MAWS)Marine Station network Automatic Marine ..25 3.9 Figure Network Gauge Tide UK The ..23 3.8 Figure Wave European Model 3.7 Figure Figure 3.6 Representationofawavefieldusingtheoneandtwodimensional ..14 heights wave individual Figure 3.5 of distribution Rayleigh Normalised ..13 3.4 Figure series time speed wind Example 3.3 Figure Illustrationofanidealisedlogarithmicwindprofilethroughthe ..11 Figure 3.2 depth over profile velocity Theoretical ..6 projects wind offshore 2 3.1 Round Figure and 1 Round of Map ..2 cycle life 2.1 project Figure against structure document of Schematic 1.1 Figure Figures . .101 Casestudy: Forecast servicesforBeatricewindturbineinstallation ..77 tables frequency and rose wave of Example Box 8.1 ..76 tables frequency and diagram scatter wave of Example 7.2 Box ..62 WaveHub study: Case 7.1 Box ..60 mast met a of Installation study: Case 6.3 Box 6.2 Box Casestudy: Exampleofdownscalingusingwavetransformation . . .35 forecast marine typical a of Example study: Case Box 6.1 ..23 WaveEuropean study:Model Case 3.2 Box 3.1 Box Boxes ..11 standards present of Bibliography . References ihteudryn aafrtedrcinsco 8 o29N...... 73 with theunderlyingdatafordirectionsector180to209°N resource ..41 project renewables marine idealised an of cycle life the . . .15 spectra wave ..12 layer boundary ..57 modelling xml fwv ouainefcsdet hlo ae nlecs . . .16 Example ofwavemodulationeffectsduetoshallowwaterinfluences ..47 s Atlas ofUKmarinerenewable energy . .113 9 vii © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED viii Figure 10.1 Decommissioning activities and linkages ..110 linkages and activities Decommissioning ..104 10.1 Figure linkages and activities Construction 9.1 Figure ..98 process Figure 8.6 forecast weather the of Schematic ..95 8.5 Figure Typical(right) vessel jack-up and barge(left) jack-up 8.4 Figure Installationofturbineblades(left)aborted operationsduringhigh ..93 Figure 8.3 Wavetow under energydevice ..91 8.2 Figure linkages and activities Construction 8.1 Figure ..88 Vesselprocess planning operations 7.8 Figure Restrictedlineofsightforsmallservicevessels inraised . . . . . Figure 7.7 .85 Illustrationofthechallenge ofvesselaccesstoafixed platform Figure 7.6 al . Exampleprovidersofforecastservicesto the UKsectorof ..96 vessel jack-up Typicala for conditions operating maximum Table 8.3 ..95 barge jack-up Typicala for conditions operating maximum Table8.2 ..79 statistics persistence of table Example Table8.1 ..78 direction) versus period (wave Wavetable frequency Table7.7 ..77 direction) versus height (wave Wavetable frequency Table7.6 ..76 period) versus height (wave table frequency wave Example Table7.5 ..75 analysis frequency in use for increments Recommended Table7.4 Table7.3 values. Exampleoftabularpresentationfordirectionalwaveextreme . . .69 Designchoicesthatwillbeinfluencedbymetoceanconsiderations Table 7.2 ..62 WaveHub for derived Waveestimates resource Table 7.1 Typical . . . . metoceanoperatinglimitsforsiteinvestigationvessels . . .55 Table6.2 . . .48 measurements metocean of Sources Table 6.1 ..48 selection site inform to data metocean Broadscale Table5.2 ...... 34 Forecast productsrelevanttomarinerenewablesapplications Table5.1 ..30 sources data wave of Summary Table 3.7 . . .29 sources data wind offshore of Summary Table3.6 ..27 sources data current of Summary Table3.5 ..26 sources data level water of Summary Table3.4 ..24 data metocean for centres archive data UK Table3.3 Table3.2 Genericstrengthsandlimitationsofdatasourcesclassifiedas: . ..8 developments UK TEC and WEC known of Schedule Table 3.1 Table2.1 Tables id,(ih)fvual odtos..95 conditions favourable (right) winds, ..87 conditions sea ot e i n a nuty..99 industry gas and oil Sea North ..72 degree 30 on Based ..22 forecasts modelling, In situ ntlainoeain tteBarc idfr eosrtrst . . Installation operationsattheBeatricewindfarmdemonstratorsite measurements, remotesensing,re-analysis/hind-cast CIRIA C666 .101 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 eunpro Average ofthatvalue. periodoftimebetween exceedances which flowsalternatelyinapproximately Atidalcurrent Activitiesassociated withday-to-dayproduction. Return period conditionsin Ashort-termweather forecastforexpected From manydirections. Theperiodofthetidewhen thesunandmoonareoutof Rectilinear Operations Omni-directional Statisticalconsiderationofmorethanonevariableata Nowcast Thecombinationof oceanographicandmeteorological Informationthatdescribesadataset. Neap Alongameridianoftheglobeorinnorth-south Multi-variate Metocean Aforecastpredictingweatherconditionsfromthreeto Metadata Meridional ofpeakeventswhichoccuratlow Anexpression Anyactivityassociatedwithensuringplantandequipment Medium-range Aforecastpredictingweatherconditionstypicallyupto30 Marginal extremes Aperiodtypicallyspanningseveralyears,andwherethe Maintenance Theassessmentofpastweatherconditions. Long-range Theassessmentoffutureweatherconditions. Long-term In situ Components of thetide. Astatisticalvaluerepresentingarareevent. Hind-cast Aperiodoftimewhen weatherpreventssafeaccesstosite Harmonic constituents Forecast Aneventthatoccurstwicedaily. Ananalyticaltechniquetointroducehigherlevelsof Extreme value Downtime Deterministicwaveusedfordesignofanoffshore Downscaling Diurnal Anancillarycostthatrepresentsliquidateddamagesfor Design wave Theinterfacebetweentwofluids(air-seaorsea-seafloor). Adescriptionofwaterdepthsacrosstheseafloor. Demurrage Boundary layer Bathymetry Glossary opposite directions. fewhours. the next phase. time. data. direction. seven days(ieoneweek)ahead. frequencies. remain in,orarereturnedto,properworkingorder. days (onemonth)ahead. thedurationofonecycleevents. timescale exceeds or operationsonsite. spatial detail. structure. laytime. loading ordischarging ofcargo withinthestipulated delays, occurswhenavesselatberthispreventedfromthe In theplaceoforigin. ix © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED x cte iga Thegraphicalpresentationoftwoormoremetocean Scatter diagram oa Alongalatitudecircleor intheeast-west direction. Thetendencyofavesseltomovesidewaysawayfromthe Zonal asetof Aneventwhenweatherconditionsexceed ofwaveheighttowavelength. Windage Ratio Thehorizontaldistancebetweentwoidenticalpointson Statisticalconsideration ofasinglevariable. Weather day Wave steepness vectorinarotary Thepathtracedoutbyatidalcurrent Asummaryofrepresentativeconditions. Wind-waves remotefromtheareaofgeneration. Wavelength Alarge changeinsealevel (eitherpositiveornegative) Uni-variate Tidal ellipse Theperiodoftidewhenthesunandmoonareinphase. Synoptic oftheuncertaintyinavalue,beingan Anexpression Swell Amathematicaldescriptionofaserieswindsorwaves Surge Standard error Spring Spectrum Period attheendofbuildprocesswhenalistany Aperiodtypicallyspanningseveraldaysormonths,and Aforecastpredictingweatherconditionsoverthenext Snagging phase lifetime,ortheacceptableperiodofusein Theexpected Short-term Havingaperiodorcycleofapproximatelyone-half Short range Service life Thelong-termupwardordownwardtrendinatime Semi-diurnal Secular trend wave period(T variables, egsignificantwaveheightversesarepresentative above-deck structures. wind becauseoftheforcesontopsidesand contracturaldowntime. incurring predetermined criteriaandpreventsafesiteaccess two successivewavecrestsortroughs. flow regime. meteorologicalevents. generated byextreme estimate ofthestandarddeviationsamplemean. infrequencyspaceand/ordirectionalspace. expressed target completiondate. rectify thedefect,partyresponsibleforworkanda accompanied byadescriptionoftheworkrequiredto quality defectsinthebuildisproduced.Itusually where thetimescaleislessthanonecycleofevents. three days(day). service, foranoffshoreinstallation. tidal day. periodic andshort-termduration. series, asopposedtoasmallercyclicalvariationwith z or T p ). CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 GW GreaterGabbardOffshore WindLimited on technicalaspectsofdataexchange Groupofexperts Failure modesandeffects andcriticalityanalysis Food andEnvironment ProtectionAct1985 EuropeanSpaceAgency Environmentalstatement GGOWL Emergency rescueand recoveryvessel Earthobservation GETADE FMECA EuropeanMarineEnergy Centre FEPA EnvironmentalImpactAssessment Emergency Monitoring AndResponseCentre ESA ES ERRV EuropeanDirectory of MarineEnvironmentalData EO Weather EuropeanCentrefor MediumRange Prediction DepartmentofTrade and Industry(nowintegratedinto EMEC Dynamicpositioning EMARC DetNorske Veritas EIA EDMED DataManagementTechnical Dataandinformationstewardshipplan Working Group ECMWF Dataandinformationmanagementplan DTI DepartmentforEnvironment, Food andRural Affairs DP Government DepartmentforCommunities andLocal DNV DataArchiveCentre DMTWG CoastProtectionAct1949 DISP DIMP CommissionoftheEuropean CollaborativeOffshoreWindResearchIntothe DEFRA Construction(Designand Maintenance)Regulations2007 DCLG Chartdatum DAC CountrysideCouncilfor Wales CPA ChannelCoastalObservatory COWRIE BritishWindEnergy Association CEC BritishOceanographicDataCentre CDM CD DepartmentforBusiness,Enterprise&RegulatoryReform CCW BritishAtmospheric DataCentre CCO AdHocWorking Grouponmarinerenewablestandards AssociationforGeographic Information BWEA BODC profiler Acousticdopplercurrent BERR BADC AHWG AGI ADCP Abbreviations andacronyms BERR) Environment (formerly DTI) xi © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED xii E Tidalenergy converter SouthWest Regional DevelopmentAgency Safetyoflifeatsea Strategicenvironmentalassessment SystemofIndustry Metocean datafortheOffshoreand TEC SupervisoryControlAnd DataAcquisition Syntheticapertureradar SWRDA Remotelyoperatedvehicle SOLAS Rootmeansquare SIMORC Renewableenergy zone SEA Reliabilitycentredmaintenance SCADA ResearchAdvisoryGroup SAR Projectdesignstatement ROV ProudmanOceanographicLaboratory RMS Probabilitydensityfunction REZ InternationalAssociationofOil&GasProducers RCM Operationsandmaintenance RAG Numericalweatherprediction PDS Nauticalmile Nationaltidalandsealevelfacility POL PDF NorthEuropeanStormStudy OGP NorthAtlantic Oscillation O&M Marinerenewabledeploymentfund NWP MarineandFisheriesAgency Meteorological NTSLF nm MarineDataandInformationPartnership NESS predict Measurecorrelate NAO MRDF MarineConsentsand Environment Unit(nowintegrated MaritimeandCoastguardAgency MFA Met Marineautomaticweatherstation astronomicaltide Lowest MDIP InternationalStandardsOrganisation MCP Intergovernmental OceanographicCommittee(UNESCO) InternationalElectrotechnicalCommission MCEU MCA InternationalAssociationofmarineaidstonavigationand MAWS Health&SafetyExecutive LAT Globalsystemformobilecommunications ISO IOC GeneralPacket Service Radio IEC GeographicalInformationSystem GermanischerLloydWindEnergie IALA HSE GSM GPRS GL Wind GIS Research Communities into MFA) Lighthouse Authorities CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 M eXtensibleMark-upLanguage World MeterologicalOrganization Wave energy converter Working GrouponMarineDataManagement Vessel Traffic Services XML UnitedNationsEducational,ScientificandCultural WMO UnitedKingdomOffshoreOperatorsAssociation WGMDM UnitedKingdomHydrographicOffice WEC UnitedKingdom VTS UKGEo-spatialMetadataINteroperabilityInitiative UNESCO UKOOA UKHO UK Gemini UK Organisation xiii © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED xiv U T T T frequency(Hz) waterdepth(m) m H H H f d θ θ δ U λ λ CO ()representsthespectrumin frequency(f)space T S(f) Symbols standarddeviationofthemeanwindspeed(m/s) U c p n z s p e c 10 s rms max or H 2 sig winds and waves are expressed astravellingfrom winds andwavesareexpressed mean wave(orwind)direction(degreesNorth),noting period (m/s) mean windspeedaveragedovera10minutesampling are expressed astravellingto are expressed direction(degreesNorth),notingcurrents mean current zero crossingperiod(s) duration oftheseastate(s) peak periodinthespectralrecord(s) energy period(s) n significant waveheight(m) root meansquarewaveheight(m) maximum waveheight(m) carbon dioxide wavelength atpeakperiod(m) speed(m/s) current wavelength (m) th moment ofthespectrum CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Introduction 1 1 . 1 renewable schemes.Theguidelines drawfromestablishedpracticesacrossmoremature developments, includingboth oilandgasprojectsthepresentphaseofmarine insupportingavarietyofoffshore who collectivelybringtogether provenexperience These guidelineshavebeendeveloped byaninformedgroupofmarinepractitioners for alltypesofmarinerenewableschemesandthrough stages ofprojectlifecycle. metocean conditions.Itisnotedthatconsiderationof dataisakey requirement development aswindprojects,butwilldeliberatelyselectsites thatoffermoreenergetic technologies. to assistthedemonstrationphaseforalimitednumberof themoreadvanced Reform (formerlyDTI)announcedtheMarineRenewables DeploymentFund (MRDF) projects. Intheinterim,DepartmentforBusinessEnterprise andRegulatory The UKGovernmentisyettoinviteacommercialround for waveandtidalenergy 2 projectspresentsadditionalchallengestotheindustrywhichareyetbefullytested. greater. Design,construction,operationandeventualdecommissioningoftheseRound further offshoreandindeeperwater, targeting areaswherethewindresourceis is upto25timeslarger infootprint.Inaddition,thesenewprojectstendtobesited scale ofthesenewprojectshasnotbeenaslimitedwithRound1,andinsomecases provide asignificantcontributiontomeetingUKrenewableenergy targets. Assuch,the progressing throughtheconsentsphaseandinvolveslarger projectsdesignedto fortheindustry.experience Thesecondcommercialround(Round2)isalready demonstration phaseforoffshorewindtechnologyandwiththeobjectivetobuild wind farmsaroundtheUKcoast.Thisactivityhasgenerallybeenregardedasa thisoffshoreresourcehasseentheconstructionofsize-limited (Round 1)toexploit Presently theleadingtechnologyiswindenergy, andthefirstcommercialround in offshoreenvironments. thatanincreasingemphasiswillbeplacedonproductionfromsiteslocated it isexpected renewable sourcesby2010,risingto40percent2020.Inorderreachthesetargets electricity generatedinScotland(asaproportionofdemand)shouldcomefrom Government (formerlytheScottishExecutive) hassetatarget that18percentofthe per centofelectricitysupplyfromrenewableenergy by2010(DTI,2007).TheScottish CO Renewable energy isanintegralpartoftheUKGovernment’slong-termaimreducing water thanthepresentphaseofmarinerenewabledevelopments. are establishedforoffshoreinstallationswhichmorelikely tobefoundindeeper metoceanstandards identifying theirrelevantusage.Notethatthemajorityofexisting established literature,moreover, texts, itprovidesaroutemaptotheseexisting a widerappreciationofmetoceanissues.Theguideisnotintendedassubstitutefor surveyors, environmentalconsultantsandotherkey stakeholders whowillbenefitfrom This documentservesasareferencesourceforprojectdevelopers,engineers,marine renewables industryonthesubjectofmetoceandata. The aimofthisdocumentistoofferguidanceandidentifygoodpracticethemarine PURPOSE ANDL 2 emissions by60percentof1990levels2050,andwithaninterimtarget setfor10 These newwaveandtidalprojectsfacesimilarchallengesfor offshore I M I TAT I ONS 1 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Figure 1.1 2 1 2STRUCTUREOFTHESEGU .2 Schematic ofdocumentstructure againstprojectlifecycle (adaptedfromFigure4.1) points isgiveninChapter11. depth, thespecificmetoceanissuesforeachstageoflifecycle.Asummarykey details ofthisprojectlifecycle(Figure1.1),withChapter5to10developingin through thelifecycleofagenericmarinerenewablesproject.Chapter4provides providing guidanceinthepotentialuseofmetoceandatatosupportsequentialstages project development(Chapter3).Thefurtherstructureoftheguideisbasedupon 2) andisthenfollowedbyanintroductiontothesubjectofmetoceandatarelevant This guideinitiallyidentifiestherangeofpresentmarinerenewableinterests(Chapter renewables sector. fromthemarine offshore industriesandarecombinedwiththepresentexperience I DEL I NES CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 1 3HOWTOUSETHESEGU .3 available from this exercise tosupport asubsequentstageofprojectdevelopment. available fromthisexercise potential linkagesbetweenactivities,andwhatdataunderstandingshouldbecome project development,whatusesshouldbemadeofthedatatosupportkey activities,the project lifecycle,identifywhatmetoceandatashouldbeavailableatthispointinthe In industry. representsgoodpracticewithinthemarinerenewables recognition towhatcurrently the furtherrequirementsofusingmetoceandataarereadilyidentified,alongwith The guidelinesarestructuredsothataseachphaseofprojectdevelopmentisadvanced usage. identifyingtheirrelevant texts, more importantlytheyarearoutemaptotheseexisting development. Theguidelinesarenotintendedasasubstituteforestablishedstandards, who willbenefitfromawiderappreciationofmetoceanissuestosupportproject engineers, marinesurveyors,environmentalconsultantsandotherkey stakeholders These metoceanguidelinesareintendedtoserveasareferencetoolfordevelopers, this manner, theguidelinesprovideanentrypointtoeachstagein I DEL I NES 3 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 4 . PRESENTSTANDARDS 2.2 2. 2C 1 and gasindustries. The bibliographyprovidesalistofpresentstandardsacross marinerenewableandoil highlighting emerging goodpractice. document formspartofthisoverallstrategy, andwiththedeliberateaimof safety) tounderpindevelopmentofthemarinerenewables industry. Thepresent across therangeofdisciplines(egmetocean,engineering, riskmanagement,healthand Additionally, notethatthere isactiveinterestindevelopingasetofbespoke standards present limitationsintheirapplicationwherethesemightexist. potential roleinassistingmarinerenewabledevelopment,butalsotohighlightany literaturethatisconsideredrelevantandtoillustratetheir attention toexisting or guidelinesrelatingtooffshoredevelopment.Rather, theaimistoidentifyanddraw codes,regulations,standards This guidedoesnotattempttosubstituteforanyexisting metocean issuesrelatedtothesetypesofnewprojects. maintenance. Thesecontrastingissuesamplifytheneedforafocusedconsiderationof high energy metoceanconditionsandwillbeunmannedapartfromperiodsof ofsmallerinstallations,targetingbe inadispersedarrangement areaswhichprovide are presentlybeingconsideredatsitesclosertoshore,inshallowerwater, arelikely to generally compriseofsinglemannedplatforms.Incontrast,marinerenewableprojects gas interestsmaytarget deeperwaterlocationsworldwideandinstallationswill offshoreoiland immediately transferabletomarinerenewableprojects.Asanexample, maynotalwaysbe engineering, andoffshoreoilgasindustries,howeverthesetexts Separately, therearemanyfamiliarandestablishedstandardsinuseforcoastal to eachtypeofdevelopment. testing, consenting,designanddecommissioning,maynotnecessarilybeapplicable documents havealsotendedtofocusondiscretestagesinthedevelopmentpathfrom been writtenforspecificaspectsofoffshorewind,waveandtidaldevelopment.These to theuseofmetoceandataformarinerenewablestudiesarefragmentedandhave standardsandguidancewhichrefer At thetimeofpublishingtheseguidelines,existing between thestagesofdevelopmentandvariousongoingsupportactivities. statusofthesetechnologiesisofferedtodrawcontrast brief reviewofthecurrent and tidalstreamdevelopments,withspecificinteresttoissuesrelatedtheUK.A Marine renewableprojectsconsideredinthisdocumentfocusonoffshorewind,wave OVERV projects urrent I EW
status
of
marine
renewable CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 . OFFSHOREW 2.3 oe * Note: offshore andintodeeperwater. To datethreeRound2projects zonesalsotendtopushtheseprojectsfurther km² oftheseabed.Thecoastalexclusion from Round1,withsomeofthebiggestprojectsseekingtodevelopasmuch250 those and recreationalactivities.ThesizeofRound2projectsgenerallyfarexceeds disturbance tobirds,visualimpact,aswellthepotentialimpactoninshorefishing sensitivity ofshallowcoastalwaterstowindfarmdevelopment,inparticularthepossible zonesrecognisethepotentiallyhigher around 8to13kmoffthecoast.Theexclusion from zoneswhichgenerallyextend area throughthespecificationofcoastalexclusion Within eachSEAareaplanneddevelopmentshavebeenlimitedfromthenearshore NorthWest. 3 Thames. 2 GreaterWash. 1 considered: round ofdevelopments(Round2)forEnglandandWales. Threeinterestareaswere commissioned astrategicenvironmentalassessment(SEA)forsecondcommercial With acontinuedinterestfromthewindindustryforlarger scaleprojectsDTI construction offurtherprojectsscheduledin2007andonwards. andBurboBank,with construction: NorthHoyle,ScrobySands,KentishFlats,Barrow shallow depths(<20m).To date,fiveRound1projectshaveproceededthrough water. Nominally, themajorityofsitesremainedclosetoshore(<10km)andin good windresource,proximitytogridandviabilityofconstructioninrelativelyshallow fortheindustry.was tobuildexperience Sitesweregenerallyselectedonthebasisof turbines andforanareaofseabednolarger than10km².TheprimaryaimofRound1 offshore windprojects(Round1).Thesewererestrictedtoamaximumof30 From thesuccessofBlythUKGovernmentinvited afirstcommercialroundof Blyth Harbour. starting in2000withthefirst The UKisalreadyadvancingthedevelopmentofseveraloffshorewindfarmprojects, 1 andRound2sitesaroundtheUK. and arenowplanningforconstruction.Figure2.1providesanoverviewmapofRound Thanet GreaterGabbard 3 Array London 2 1 At thetimeofpublication: I ND proof ofconcept installation oftwooffshoreturbinesoff * have securedconsents 5 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 6 Figure 2.1 Map of Round 1 and Round 2 offshore wind projects (courtesy TheCrown Estate) windprojects(courtesy Map ofRound 1andRound 2offshore although someearlymetmast structuresmaysoonberemoved. and operation.Projectsremain toonewfordecommissioningtobeconsidered, industry inareasofprojectplanning, environmentalassessment,design,construction nearly 9GW andfrom over2500turbines.Experienceisdevelopingrapidlyfor the plannedoffshorewindprojectsamountsto The totalinstalledcapacityfromcurrently targeting areasfurtheroffshorewherethewindresourceimproves awayfromthecoast. development ofcommercialscaleprojectsisnowbeingadvanced bymajorutilitiesand In summary, theoffshore windindustryhasachievedapositionwherethe tohighwavesfrom theNorthSea. 25 kmoffshore,in45mwaterandisexposed two turbinesadjacenttotheBeatriceOilfieldinMoray Firth,asitewhichisaround offshore windprojectsintothedeepestwatersofar. Constructionstartedin2006for In Scotland,theBeatricewindfarmdemonstratorproject hastaken theinstallation of CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 . WAVEANDT 2.4 around 64unitsandninedevicetypes. TEC deviceswhichpresentlyamountstoaround120MWofinstalledcapacityfrom Table 2.1identifiestherangeofplanneddeploymentsaroundUKforWECand technology. consented WaveHub project,offHayleinCornwall, fordemonstratingWEC which providetestingbaysforprototypeWECandTECdesigns,therecently initiatives suchastheEuropeanMarineEnergy Centre(EMEC),basedinOrkney, respective technologies.Thisphaseintechnologyprovingisassistedbyanumberof Wave andtidalstreamdevicesarepresently enteringthedemonstrationphaseoftheir to harnesstheresourcefromdifferentlocations. partly duetothenatureofresourceandvarietytechnologydesignsneeded probable thatmorethanonetypeofWECorTECwillemerge asmarket leader. Thisis wave energy converters(WEC)ortidalstreamenergy converters(TEC),anditremains Unlike offshorewindthereispresentlynoconvergence intechnologytypeforeither developments induecourse.Theseinclude: design thatareanticipatedtobereadilytransferablesupportwaveandtidal The industryhasbeenassistedwithvariousformsofguidanceforconsentingand and CPA requirements Offshore windfarms.GuidanceforEnvironmental ImpactAssessmentinrespect ofFEPA navigational safetyissues Proposed UKOffshore RenewableEnergyInstallations(OREI)–guidancenoteon Guidelines forthecertificationofoffshore windturbines.IV–Part 2 guidance notesforindustry Decommissioning ofoffshore renewable energyinstallationsundertheEnergyAct 2004, Offshore windfarmconsentsprocess Design ofoffshore windturbinestructures I DAL STREAM (MCEU, 2004). (MCA, 2004) (DTI, 2006) (DTI, 2004) (DNV, 2004) (GL Wind,2004) 7 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 2.1 8 Schedule ofknown WECandTECUKdevelopments (correctatdateofpublication) includes: The emerging informationresourcetoassistwaveandtidalstream projectspresently
I mo NOLOG v ements I
ES data CIRIA C666 surge © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 3.1 Theoretical velocityABPmer, profileover depth(after 2006) such aspeakflowsandtimes of highandlowwater, canbefullyresolved. recorded usingasamplingrate of15minutes,orless,sothatkey featuresofthetide, measurementswhichhavebeen toobtainwaterlevelandcurrent It ispreferred The commonparametersusedtodescribewatermovementsareasfollows: headlands characteristicallyprovidinglocationswithstrongestflows. influenced bythelocalbathymetryandcoastlineorientation,withchannels lowwater.towards thenext Inshallowwaterthepatternoftidalflowsisgreatly flood tidegeneratesflowsintoanareauptohighwater, afterwhichflowsebbaway during eachtide.FromLarge volumesofwaterareexchanged lowwatertherising toward (referencedasdegreesnorth),theresultantof uandvvectors. current direction current speed, datum) orordnancedatum(Newlyn) referenced tosomeagreeddatumegmeansealevel,lowestastronomictide(chart sea-surface elevation turbulence likely towardstheseasurface. be atmid-depthstoavoidvelocitysheartowardstheseabedandincreased interest toanyTECdeveloper, astheidealpositionforenergy captureislikely to towards theseabed(Figure3.1).Theshapeofthisverticalprofileisprimary a variablevelocityprofileoverthewatercolumnandonewhichdiminishesrapidly friction whichcreatesdragforcesinaboundarylayer, theconsequenceofwhichis continuallyinteractwiththeseabedthrough vertical (w)components.Currents further resolvedintozonal(u,westtoeast),meridional(v, southtonorth)and speedcanbe interval andrepresentativeofapointinthewatercolumn.Current U , Ø c , therateofhorizontalflowwater(m/s)averagedoverasample c , the vertical rise and fall of the tide expressed inmetresand , theverticalriseandfalloftideexpressed , the direction in which horizontal current flowsareheading , thedirectioninwhichhorizontalcurrent 11 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 12 Figure 3.2 3. 1 2O .2 Met Office) layer (courtesy Illustration ofanidealisedlogarithmicwindprofilethrough theboundary Note: level measurements andinterpretation axes ofa asthesemi-majorandsemi-minor the onedimensionalwavespectrum),orforcurrents intermsofharmonicconstituentsforsea-surfaceelevation(anequivalent expressed The inherentregularityofthetidalcomponentwatermovementscanalsobe wind climateatthehubheightasverticalreference. consequence oftheseverticalvariationsoffshorewindfarmsrequiredefinitionthe as afunctionofseatemperature,andthetemperatureoverlyingairmass.As stability oftheatmosphere(iepotentialforairtorise),whichisusuallydetermined level (Figure3.2).Windmaybesubjecttofurtherverticalvariabilitydependingonthe of thewindisgenerallyassumedtodecreasethroughverticaltowardstillwater layer effects,causedbythedragassociatedwithwindflowingoversea,strength Offshore windstendtofluctuaterapidlyinspeedanddirection.Asaresultofboundary and theleveloffrictionaffectingwindboundarylayer. on surfacewinds,sincechangingwaveconditionsimplya changeinsurfaceroughness the seasurface(seealsoSection3.1.3).Thewavefieldwill alsohaveafeedbackeffect a majorcomponentofthewaveclimatewillbelinked towindconditionsblowingacross create waves.Sincewaveheightwillincreaseinlinewithincreased forcingbythewind, At theseasurfacewindfieldwillinteractwithwaterthroughfriction to ffs h ore measurements atthislevelduetoshadowing indicates thatinhighseastates,waveswillpotentiallyhaveanadverseeffectonwind significant, andthe95thpercentilesignificantwaveheightrelativetobuoyanemometer byawavebuoyandthatathubheightis speed betweenthenearsurfacewindexperienced height fortheNorthSea,andanassumedwindturbinehubheight.Theincreasein wind speedfroman Dashed linesmarked onthediagramindicaterepresentativeheightsformeasurementof tidal ellipse
wind . Further detailsonthesedescriptorsareavailablein in situ meteorological buoy(approximate)95thpercentilesignificantwave (UNESCO, 2006)orinPugh(1987). Manual onsea CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 3.3 3. 1 3S .3 Example wind speed time series (courtesy MetOffice) Example windspeedtimeseries(courtesy Note: one direction. generating area.Itispossible thatforagivenseastate,swellmaycomefrommorethan which theyweregenerated,or cannolongerbesustainedbythewindsin of theocean. swell Sea statedescribesthewavefieldresultingfromcombined contributionsof spectral densityfunctionofthewindspeedprocess,S(f),which isafunctionofU for engineeringdesign)thewindspectrumcanbedescribedintermsofapower For cases whereamoredetailedconsiderationisrequiredofthewindconditions(eg The behaviourofwindsiscommonlydefinedbythefollowingterms: 19901-1 (2006)andSection3ofDNV-OS-J101 (2004). Further detailsrelatingtoderivingwindspectrumaregiven inAppendixAofISO- frequencies. Thismethodofdescribingwindisanalogous tothewavespectrum. δ U, and expresses howtheenergyU, andexpresses ofthewindspeedisdistributedbetween different ea mean istaken overastandardmeasurementperiod,suchas10minutes(Figure3.3) such as10minutes(degreesnorth). given elevation,wherethemeanisderivedoverastandardmeasurementperiod, mean winddirection turbulent intensity the WMO, succeedingthemaximumwindvaluefromobservedrecord) mean ofwindspeed(m/s)(thethreesecondgustisarecentstandardadoptedby taken asthemaximumthreeseconds fluctuations aboutthemean,forexample gust windspeed standard deviation mean windspeed
components. state and themaximumthreesecondaveragegustvaluefor10minutesample(yellowtriangles) This iscomparedwithstandardmeasuresof10minuteaveragewindspeed,U10(redsquares), The bluetraceshowsvariabilityinrawwindspeedandindicatesstrongshort-termfluctuations. Swell Wind-sea , referencedtoagivenelevation,asanindicatorofthemaximum represents windwavesthathave eithertravelledoutoftheareain (U , definedastheratioof ( 10 δ , thedirectionthatwindiscomingfrom,referencedtoa U), measureofvariabilitywindspeedaroundthemean(m/s) ), expressed inm/sandreferencedtoagivenelevation,wherethe ), expressed waves aregeneratedbylocalwindsblowingoverthesurface δ U/U 10 (dimensionless) wind-sea 10 and and 13 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Figure 3.4 14 showing positionsinthedistributionofrootmeansquarewave height(H Normalised Rayleigh distributionofindividualwave heights(Longuet-Higgins,1952)and significant wave height(H waves) following Abramowitz andStegun(1965) and Fisher-Tippett distributions,amongothers(seeSection7.4.1). of 100years),commonlyusedprobabilitydensityfunctions(PDF)includetheWeibull significantwaveheightvalue(egwithareturnperiod heights tocalculateanextreme distribution thatrepresentstheuppertailofalong-termsamplesignificantwave Groenendijk andBattjes(1999)orThorntonGuza(1983).Whenconsideringa water (egwherewavebreakingconstrainshigherwaves)suchasproposedby 1952),oramodifiedformforshallow Figure 3.4)indeepwater(Longuet-Higgins, of wavesislikelydistribution(see tobederivedfollowingaformsuchastheRayleigh whether thewavesareindeeporshallowwater. For ashort-termdistribution example, which touseaccordingthetimescaleonwavesarebeanalysed,and consultantwillchoose distributions areusedinengineeringpractice,andanexpert period ofyears(climateorlong-termdistribution).For eithertimescale,anumberof represent thevariabilityofastatisticalparameter, suchassignificantwaveheightovera persisting overtheorderofhours(short-termdistribution)anddistributionsusedto distributions usedtorepresentthevariabilityofindividualwavesinaseastate When discussingstatisticalwavedistributionsitisnecessarytodistinguishbetween design purposestopropertiesofaparticularwavespectrumandstatisticaldistribution. variations providesstandardsummaryparameterswhicharecommonlyrelatedfor groups ofwaveswithvaryingheight,periodanddirection.Statisticalanalysisthese During theperiodinwhichwaveobservationsaremade,seastatewillcomprise The propertiesofindividualwaveswithinagivenseastatecanbedefinedaccordingto: given amplitude(energy), period (or frequency)anddirection.Two forms ofthewave described asasummationof a pre-definednumberofsinusoidalwaves,eachwith The wavespectrumisdefined ontheassumptionthatagivenwavefieldcanbe wave direction wave period wave height , verticaldifferenceinelevationbetweenwavecrestandtrough(m) , timebetweensuccessivewavecrests(s) , direction that waves arrive from( , directionthatwavesarrive sig ) andmaximumwave height(H ° N). max based onasampleof1000 rms CIRIA C666 ), © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 3.5 Representation ofawave fieldusingtheoneandtwo dimensionalwave spectra Note: < 0.5. relationship betweenwaterdepth (d)andwavelength( Intermediate wavesarethose thatarebeginningtofeeltheseabedandhere wavelength ( and ingeneralthewaterdepth(d)canbeconsideredsmall incomparisontothe Wave conditionsheavilyinfluencedbytheseabedaredescribedasshallowwaterwaves, wavelength ( waves, andingeneralthewaterdepth(d)canbeconsidered large incomparisontothe When wavesarenotbeingaffectedbytheseabedthey describedasdeepwater Figure 3.6). profile oflarge sandbankscreatesadditionalshelteringaroundtimesoflowwater(see largerexamining wavesmeasuredwithintheOuterThamesandwhereshallow suited toresolvesucheffects.Thispatternofwavemodulationcanbedemonstratedby to modulatethewaveregimeandasampleintervalof30or60minutesmaybemore shallow watertheseintervalsmaynolongerbesuitablesincetidalvariationsbegin and thatwavesoscillatearoundthisfixed level.Instronglytidallocationsandareasof measurement intervalitispresumedthatthemeanstillwaterlevelremainsconstant longer) tocaptureandresolvesufficientdetailinthemovingwaveform.Over and overaduration(burstperiod)ofseveralminutes(theoretically30or In deepwateritisfairlycommontosamplewaveconditionsatintervalsofthreehours space only(ienodirectionalinformationisavailable). dimensional spectrumgenerallyreferstoenergy forsinusoidsdefinedinfrequency spectrum definesenergy forsinusoidsinfrequency-directionspace;theone spectrum arecommonlyusedbyoceanographers(Figure3.5).Thetwodimensional wind-sea energy directionalspreadofswell energy comparedto themorenarrow travel) anddirectionalspreadofenergy, andshowsthetypicallyhighdirectionalspreadof spectrum (righthandplot)providesfurtherinformationondirection(towardwhichthewaves frequency space(theinverseofperiod)astwodistinctpeaksinenergy. Thetwodimensional On theonedimensionalspectrum(lefthandplot)twocomponentsarerepresentedin six seconds,andanobliquenorthwesterlyswellwithaperiodofapproximately13seconds. The seastateshowncomprisesasouthwesterlywind-seawithpeakperiodofapproximately λ λ ), ied/ ), ied/ λ λ < 0.05. > 0.5. λ ) fallsintherange0.05
aaisthearchiveddatawhichmayoriginatefromeithermodelor data reference aaprovidesomeformofprediction,commonlybasedonasuitable data
aarelatestorealtimeobservationsandaredesirablesupport data reference sea area,aspecificlocation(xandy) (UNESCO, CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 .. O 3.2.5 which aresummarisedinTable 3.1. These datatypeseachhavedifferentstrengths,limitations andrangeofapplication 4 3 2 1 Metocean datawilloriginatefromoneofthefollowingsources: ri g height), therangeofforecastmayberestrictedtoseveral days atthemost. obtain aprecisequantitativepredictionofgivenparameter(egwindspeed,wave fewdays)toseasonal.However,variety oftimescales,fromshortrange(next to specific siteoroperation.Forecasts relevanttomarineoperationsareavailablefora sophistication andcost,withthetrade-offbeingaccuracyand/orapplicabilitytoa Forecast products remain onabroadscale. and forreasonablylongperiods.Thecompromiseisthatspatialresolutionmay and havetheadvantageofcoveringbothawidespatialarea(egUKwide,global) Re-analysis/hind-cast modelling that dataqualityisassuredforsiteswheredownscalingissuesmayarise. lines. Dataarchivesofferthepotentialtosupportdesignandplanning,provided orbits remainalimitingissue,asdoesthecoarsenessinintervalsbetweentrack to marinewindsandseastate.However, repeatcoverageandresolutionofsatellite microwave basedsystemshasledtothegenerationofsubstantialdatasetsrelating systems. Overpastdecadessatelliteremotesensingoftheseasurfaceutilising radar meansthatthesetechniquesalsohavemarineapplicationsegwave satellite earthobservation(EO),althoughrecentdevelopmentsingroundbased from alocationotherthan Remote sensing project specificmeasurementdataascosteffectiveandusefulpossible. integration ofthesedatawithothersourcesshouldbeplannedinordertomake In addition,carefulstewardshipofnew what theacquireddatashouldachieve(egthroughgapanalysis,seeSection6.2). measurement programshouldbecarefullydrawnupwithafullunderstandingof ishigh.Thespecificationfora of theprojectwherefinancialexposure mitigating riskinvolvedwhenusingotherdatasources–particularlyforelements Nonetheless asagroundtruththedataobtainedshouldbeconsideredessentialin measurement platformorbuoy)arehighcomparedwithotherdatasources. (eginstallationofamet mast,ongoingservicingofanoffshore exercise the aimofprovidingimprovedanalysis,forecastsandnowcasts.Costsforsuchan should consideracquisitionofsufficient in suitabilityandapplicationaproject.Wheneverpossible,projectdevelopment data islikely tobesparse,sothedistancedevelopmentsitewillplayafactor deployments orarchivesofpreviousmeasurements(past).Coverageexisting description ofmetoceanconditions.Datamaybeavailablefromrealtime(present) In situ in measurements for thepurposeoftheseguidelines,referstomeasurementsmade are availablefromspecialistprovidersatvaryinglevelsof generally regardedasthemostaccurateandreliable in situ . Remotelysenseddatacommonlyrefersto datasets areavailablefromanumberofproviders in situ in situ measurements andeffective measurements acrossthesitewith 21 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 3.1 22 remote sensing, re-analysis/hind-cast modelling,forecasts remote sensing,re-analysis/hind-cast Generic strengthsandlimitationsofdatasourcesclassifiedas:insitumeasurements, to dataprovenance(Box3.1). The caseoftheEuropeanWave Modelisusedheretoillustratepertinentissuesrelated study outputs. confidence limitcanbetaken intoconsiderationwhendecisionsarebeingbasedon throughout theprocessofdataanalysisandinterpretationsothatsomeform shouldalsobeacknowledged Recognised datalimitationsandin-builterrors/accuracies broadscale data. purpose andsuitableforthetask.For initialsiteappraisalsmayonlyrequire example, should alsoconsidertheprojectrequirementsateachstagesothatdataremainsfit-for- values whichareaderivativeofthesourcedata.Theselectionanyparticulardataset A metoceanstudymaycombineanumberofthesedatatypesleadingtointerpreted measurements In situ Forecasts modelling hind-cast Re-analysis/ sensing Remote Data source Can supplyrealtimedatafor nowcast allanalysistypes fit Data provided asatimeseriesshould metocean conditions Most accurate representationof specific operations specific Numerous products canbetailoredto Allow planningfor futureevents allanalysistypes fit Data provided asatime-seriesshould area Good coverage both intimeandspatial processing appliedto raw instrumentdata Errors expected dueto highlevel of processed data quality control andprovide pre- Specialist providers ensurealevel of coverage Measured datawithwidespatial Strengths benefit (egthroughbenefit validation) Need to ensureforecast delivers Spatial detailmay becoarse increasing forecast horizon Risk ofhigherlevel oferror with scale gridpoints are represented by broader spatial Subject to errors wherecomplex sites processes representation ofcomplex physical Errors expected dueto model spatial gridpoints are represented by broader scale Subject to errors wherecomplex sites inappropriate for someanalysistypes Poor temporal sampling makes data communications withrealtime particularly Expensive to deploy andmaintain, to avoidservicing datagaps Need to carefullyplandeployment and area ofinterest Site-specific, may not representwhole Limitations CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Box 3.1 . DATASOURCES 3.3 Case study:EuropeanWave Model archive centres (DAC) that exist with aremittomaintainanddeveloptheirarchivesfor archive centres(DAC)thatexist and otherstandarddatasources. Someoftheseservicesrepresentestablisheddata services (egmetadatadiscovery websiteswhichincludeEDMED,SeaDataNet,SIMORC) for UKseascannowbeidentified, andinsomecasesaccessed,fromavarietyofonline responsible. However, thestate-of-the-artissuchthatalarge amountofmetoceandata with dataaccessibility, cost andsupportallvariabledependentontheorganisations variety ofmetoceanandotheroceanographicdatasources remainsaworkinprogress and raisingthegeneralprofileofmarinedata.At present,fullco-ordinationofthe formation ofanumberprogramsaimedatstandardising, cataloguing,exchanging identified aneedtomake morecosteffectiveuseoftheseresources,leadingtothe operators, coastalmonitoringprogramsandacademicresearch groups.TheUKhas for disparatepurposessuchasnationalmeteorologicalservices, offshoreoilandgas Traditionally, metoceandatahasbeengatheredandappliedbydisparategroups, Figure 3.7 Limitations: Origin: Spatial reference: Temporal reference: Quality: Ownership: locations. water influences limitthevalue andaccuracyofthemodelinnearshore also remote from thecoast.Themodelresolutionandtreatmentofshallow not resolved. longitude (approximately 35km).Features thataresmallerthan35km years ofdata. 18 hind-cast archive inJune1988,whichnow started provides accessto over ofqualityandaccuracy.the majorpart physical descriptionofwave processes includedinthemodeldetermines comparison withwave parameters measuredfrom anetwork ofbuoys. The formulation in1986.Modelpredictionsarecontinuallyvalidated by data underlicencefor forecast andhind-cast. The modelisbestsuited to describingadeepwater wave conditionthatis onagridschemebased1/4ºlatitudeand2/5º Predictions areoffered The modelisoperated inforecast modelto Athreehourlydata T+48hours. ofdevelopmentThe modelhasahistory andimprovements sinceitsinitial own andoperateThe Met Office theEuropean Wave Modelandcansupply European Wave Met Office) Model(courtesy Data products arebasedonmodeloutput(hind-cast). 23 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 3.2 24 3.3. 1 UK dataarchive centresformetoceandata requirement. formatwhichmaynotalwaysbeimmediatelysuitableforaspecificproject preferred further scientificinterest(seeTable 3.2).Datafromsuchsourcesmaybeheldina following genericcategoriesshouldbeconsidered: water movements,windsandwaves.Inassessingthesuitabilityofanydataset The followingsectionsgiveabriefdescriptionofcommonlyusedUKdatasourcesin
mo v ements – toensurethedataisappropriatedesignandplanninganalyses – relativetodeviceheight – toensurethatthisisrepresentativefortheprojectsite – toensurethesensorisappropriateformeasurements other oceanographicparameters Wave, water levels, currentsand parameters Wind andother atmospheric – toensurethedataisappropriatefordesignand/or Data type
wind TotalTide Admiralty Charts DTI Atlas Numerical Model Current meters Example UKHO DTI Met Office POL CEFAS iSEA Moored CurrentMeter Data) BODC (UKInventory of Source alTideSDK.asp>
specific measured, remotesensedormodelleddatasourceswillhaveoftenbeen
post - processin g 31 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 32 .. D 3.4.3 method. contractors regardingtheapplicationandlimitationsoftheirchosenpost-processing soitisrecommendedthatappropriateinformationbesoughtfromspecialist exists, At present,nosinglesourceofstandardsforsitespecificmetoceandatapost-processing the techniqueatalaterprojectstage. validate anydataanalysisproductfromspecialistcontractors,butwithaviewtore-use add toforecasts)andasaresultshouldbewelldocumentedinordernotonly The techniquesmayalsobeapplicableinfuturedatausage(egmodificationorvalue predict(MCP)methodologies. measure correlate The validation,statisticalandblackboxmodellingtechniquesprovidethebasictoolsof simple and robust enough to exist as simple androbustenoughtoexist resource estimatesremainunderdevelopment,theunderlyingmethodsarerelatively the abilityforagivenenergy power. convertertoextract Whilestandardsformaking potential (usuallygivenasaheadlineaveragefigure)and,onmoredetailedinspection, acandidatesite’srawresource Resource analysiswill,inthefirstinstance,examine Downtime (riskofweatherpreventingsafeaccesstosite). 4 Fatigue (riskduetogeneralmetoceanclimate). 3 Extremes (risk oflowprobabilityhighimpactevents). 2 Resource (what canbecommerciallyexploited). 1 are: The fourmostcommonanalysisproceduresrequiredbyamarinerenewablesproject metocean climate. opportunities andriskstoaprojectoroperationspresentedbythesite’s Design andplanninganalysesprovidethemaindecisionmakingtoolsforassessing minutes ratherthanyears,see Section7.4.2. loads,thecyclicalloadsoperate atamuchhigherfrequencyofsecondsto to extreme operational conditions,andtaking intoaccountissuessuchaswake effects.Incontrast considering theloadscausedbyvariouscombinationsofmetocean factorsduring Design forfatiguelimitsisrequiredtoassessthecyclicalloading onstructuresby details arediscussedinSection7.4.1. total distributionofindividualevents(egpopulation waves).Further eventdirectlyfromaprobabilitydistribution representingthe determine anextreme the highestevent(iewindgust,maximumwaveheight) canbedetermined,or mean windspeed,significantwaveheightataoneinNyear returnperiod)fromwhich meancondition(ie procedures eitheradoptanapproachthatascertainstheextreme windorwaveloads, engineering loadcalculations.Inordertoassessextreme conditions (usuallyatareturnperiodof50or100years)isappliedasinputfor metocean ofdesign,anassessmentextreme marine structures.Inthecontext Extreme eventshave,bydefinition,alowprobability, butpotentiallyahighimpact on drawn from willbesufficientforinitialassessments,allowingthesourcedatasetto current) distribution representingtheclimateofagivenresourceparameter(wind,wave, esi g n
and in situ
plannin measured, remotesensedormodelleddatasets(seeSection3.2.5). g anal y ses de facto standards. Ingeneralafrequency CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 .. F 3.4.5 M 3.4.4 a furtherversiondueforreleasein2008.
products
atlases Typical forecastproductsthatarereadily availablefor (Cooper et al , 2006).Thisatlasprovides 33 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 3.7 34 Note: Forecast productsrelevant tomarinerenewables applications confidence insuchforecastingcanvaryovertime. ofthekey featuresoftheforecastalongwithconsiderationshow explanation ofatypicalmarineforecastschedule andincludesan Box 3.2providesanexample 7 6 5 4 3 2 1 forecast (raw modeldata) Automated deterministic method 1or2) wave spectrum,usually (calculated fromlift the Vessel responsefor heavy any of1to 4for seastate) method 1for currentsand (threshold basedusing Subsea operations of methodologies1to 4) (threshold basedusingany Towing operations exceedance probability ofthreshold forecast (modeldata)eg Ensemble probabilistic threshold exceedance forecast egprobability of Forecaster probabilistic deterministic forecast Forecaster intervened Forecast product * Forecasts anomalieswithrespecttoclimatologyeglikelihood ofbeingwindier/lesswindy than usualforagivenmonth. Visibility Sea state (wave height) Wind speed Temperature Pressure Visibility Sea state (wave height) Wind speed Temperature Visibility Sea state (waves) Wind Temperature Pressure sub-surface) and Currents (surface Sea state (waves) Wind Temperature Pressure spectrum) Sea state (wave Currents Sea state Currents Sea state Wind Parameters (7 days to 1month) Long-range* (3–7 days) Medium range (0–3 days) Short-range (0–3 days) Short-range (0–3 days) Short-range (3–7 days) Medium-range (0–3 days) Short-range (0–3 days) Short-range (3–7 days) Medium-range (0–3 days) Short-range (3–7 days) Medium-range (0–3 days) Short-range Timescales Graph Map Table Text Graph/Table Map Text Graph/Table Map User specific Graph/Table Map Text warnings Graph/Table Map CIRIA C666 Format © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Box 3.2 Case study:Example ofatypicalmarineforecast Long-range forecasts: Forecast confidence: Forecast features: Forecast example: Requirement: Project: parameters hasbeenlimited to date. weather bewarmer orcolderthanaverage? Applicationfor windandwave forecast ofconditionsrelative to climatology, abackground for example will seasonal forecasts areamorerecentdevelopment aprobabilistic andoffer 5 to 10 day ensembleforecast to openseabasinsites). Monthlyand to behave appropriately (egpresentlyfor waves thiswillmostlyrestrictthe can beprovided resolutionmodelgridisdeemed for areaswherethecoarse subsequent days (plusday 5to day 10) anensembleprobabilistic forecast wind speedsat100 mabove sealevel (hubheight). Further parameters canbeaddedto theforecast onrequest,for example example, accompanying graphsofforecast parameters areprovided. ontheNWPdata.Inadditiontoand intervention thetext items inthis forecast isgenerated by ahumanforecaster whoprovides qualitycontrol and graphforecast issuedby marineforecasting theMetcentre.The Office Two typesofforecast areavailable beyond thefive day range.Over Confidence inthistypeofforecast isbasedupontwo factors: The forecast example isanextract from atypicaltabulated sectionofatab Thesecondfactor forecaster istheabilityofexpert to successfully 2 Theraw NWPforecast willbeexpected to diminishinqualityover the 1 The forecast containsthefollowing features: Provision ofafive day forecast ofmetocean conditionsattheBarrow site. WindFarmConstruction operationsatBarrow Offshore quantitative error expected. qualitative guideasto changesinconditions,butwithahigher the following two days theNWPdataisexpected to a good offer quantitative forecast threedays duringthefirst (shadeddarkblue).In the forecaster to willgenerallyonlyapplytheirexpertise improve the speed andwave heightareforecast to the longerfive day period,but maximum timefor whichtheforecast isissuedwithconfidence. Wind as visibilityandcloudbasethiscombinationleadsto asa 36hours quality control theNWPforecast. andintervene For parameters such model withhigherresolutionthanisusedfor successive days. areforecastanalysis state. usinga 36hours Inthiscase,thefirst five day forecast periodastheforecast moves away from theinitial parameters for detailed planningwork. tables give aquantitative five day forecast ofwindandwave issue. visibility andcloudbaseareforecast after for 36hours thefirst detailed inspectionoflater tables oftheforecast to 36hours in thefirst beidentified before making at aglancedataallows thepotential for onoperations weather effects required up-to-dateahead. Asconfidence diminishesfurther forecasts willbe confidence ratingjudgesthereliabilityofforecast for thedays meteorological thesite’s forecast affecting seaarea general situationprovides information asto theevolving lightning risk) operationshealthandsafetymight affect on-site (eggalewarnings, headline statements give information regardinggeneralwarnings that the latest information forecast areassuredofusing issuetimeshouldbegiven sothatusers designated site nameshouldbeprovided to identifyforecast location 35 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Box 3.2 36 Case study:Example ofatypicalmarineforecast(contd) F vi)Windspeed inknots,waves andswell heightsinmetres, wave andswell periodsinseconds (viii) Cloudheight(FT)above sealevel =3/8coverage ormore below 5000ft (vii) valid until0600Fri 3August 2007 (vi) At aglance– Headline (iii) Barrow (ii) Swell prd Swell hgt Swell dirn Sig wav prd Max wav hgt Sig wav hgt 50 mgust 50 mwndspd 10 mgus 10 mWndspd Wind dir Cloud Temp Visibility Weather Min Max Phase Sea temp (Celsius) Gale warning inforce Swell prd Swell hgt Swell dirn Sig wav prd Max wav hgt Sig wav hgt 50 mgust 50 mwndspd 10 mgus 10 mWndspd Wind dir orecast Confidence (v):HighbecomingmediumSaturdayConfidence thenlow onMonday. SeaduringFridayNorth andtheweekend. Highpressurewillbuildover Denmarkby Sunday. Atlantic low willbecomeestablishedsouth-west ofIcelandby Friday thispushingassociated frontal systems across theUKand pressured extends Seabefore eastacross sinkingsouthinto EnglandandtheNorth thenearcontinentonFriday. Adeep General situation(iv):Areaoflow pressurewillremainslow moving SeaduringThursday intheNorwegian whilearideofhigh
issued Thur 02August2007 10 KM+ NIL SIG DRY WSW SSW 00 15 Thur 02 August 2007Thur 02August 1.3 0.1 2.1 15 28 20 22 15 WSW 8 5
NW 0.6 0.6 1.0 00 on 4 4 7 5 6 4 W WSW SSW 04 11 Wind (mean) 0.2 1.3 2.1 18 20 15 21 27 ednesda 8 5 NNW SWS 10 KM+ 0.5 0.9 0.6 03 4 4 7 5 6 5 4400 DRY 03 15 Sat 4 August 2007Sat 4August WSW SSW 0.2 2.9 1.8 32 23 22 00 16 8 5 NNW 0.4 0.7 0.5 06 W 4 4 7 5 6 4 y 1 10 KM+ WSW SSW A 2700 0.2 3.0 1.9 34 23 06 24 17 DRY 8 5 14 No 06 15 WNW u 0.3 0.5 0.3 09 11 W 5 4 8 9 6 g ust WSW SSW 0.4 2.7 1.7 12 30 22 15 21 9 5 02/0000 02/1100 Time (UTC) 2007 10 KM+ 0.2 0.8 0.5 12 12 15 11 17 W W 7 4 4200 DRY 09 15 WSW SSW 0.3 2.5 1.5 18 28 20 19 14 8 5 at 0.3 0.7 1.2 15 12 14 10 17 W W 6 4 22.02UTC( Sun 5 August 2007Sun 5August WSW 0.9 1.3 2.1 SW 10 KM+ 00 18 13 13 NIL SIG 6 4 9 DRY 12 15 0.4 0.8 1.3 18 12 14 10 W W 6 4 9 WNW WSW 0.8 0.9 1.4 06 5 4 4 3 3 2 0.3 1.0 Sea (Sig) WSW 10 KM+ 0.3 0.6 1.0 NIL SIG i 13 21 10 W 6 4 9 7 ) DRY WSW NNE 15 15 0.6 0.9 0.6 12 5 5 1 1 1 1 Lightning risk:4(low) Fri 2007 03August SSW 0.2 0.7 1.2 12 00 13 16 W 7 4 9 NNE 0.4 0.8 0.5 SW 18 5 5 5 3 3 2 10 KM+ NIL SIG DRY 18 15 WSW SSW 0.3 0.9 1.5 03 13 19 14 10 Mon 6 August 2007Mon 6August 7 4 0.4 0.7 0.4 SW 00 N 6 5 8 5 5 4 02/0900 03/0400 Time (UTC) WSW SSW 10 KM+ 0.3 1.6 1.0 NIL SIG 20 06 15 11 16 NNW 6 4 0.4 0.7 0.5 SW 06 DRY 7 4 7 5 5 4 21 6 WSW SSW NNW 1.7 0.1 1.1 25 20 09 18 14 0.4 0.8 0.5 CIRIA C666 SW 7 4 12 12 6 4 8 8 6 Fri 03 10 KM+ NIL SIG DRY 00 16 8 W 4 0.9 0.6 15 10 10 7 WNW WSW SSW 2.0 1.2 0.1 0.2 12 26 20 19 15 18 7 4 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 . C 3.5 The scalesuponwhichclimatewillvaryandimpactonamarine renewablesprojectare: thelifetime ofthesite. sites wherere-poweringmaybeconsidered,extending of timescalesandeffectsclimatechange.Thisrequirement willbemostimportantfor whatarefluctuatingresources,marinerenewableprojectsneedtobeaware in exploiting With commercialscaleprojectssecuringleaseperiodsofbetween25and50years, may affectoperationsovertheshort-term. ordinator, vesselmasters)ininstanceswhenchangingormarginal metoceanconditions informationtokey decisionmakers (egsiteco- an interpretiverole,providingexplicit forecastdata.Thesepersonnelfulfil indealingwithcomplex istheirexperience expert One oftheimportantbenefitsemployinganon-siteforecasterormarineoperations investigated. methods forreceivingthewidestproductsuite(egthroughinternet)shouldbe operations, weathersensitiveandexpensive involving ahighnumberofextremely ability toreceiveforecastdataoffshoreisoftenalimitingfactor, andforaproject the datatobereceivedanddisseminatedbyashoreand/orsitebasedcontroller. The The actualformatinwhichdataisgivendependsonbothprovider, andtheabilityfor Formats (1997). andproductsarealsodiscussedinmoredetailWMO/TD-850 Operation specificproduct(egwavespectraforheavylift). 4 Sitespecificgraphical/tabularproduct(egtime-seriesplots). 3 Map-basedformats. 2 forecastsand warningsforadesignatedarea. Generaltext 1 Forecast formatsgenerallyfallintooneoffourcategories: of forecastperformanceusedasabasisfordecisionmaking. improve riskmanagement,withshort-term(fewhoursahead)nowcastsandverification Observations madeon-sitecanalsopotentiallybeintegratedwithforecaststofurther forecasts totheoffshoreoilandgasindustry. (WMO, 1997)givesdetailsofservicesandgoodpracticeforspecialistsofferingmarine As guidancetheOffshoreWeather Panel TD-850 operations associatedwithreceivingapoorforecast. the basisofconsultationthatassessservicecostandsupportagainstriskto highly variable,usuallyonacostbasis.Itisrecommendedthatservicesareobtained operation, andthesupportavailable(egthroughuseofaspecialistforecaster)are The levelsatwhichforecastscanbedeemedrepresentativeforagivensiteor limate net sealevelrise. multi-decadal –scenariosassociated withbroadscaleclimatechange,forexample representedbyindices suchastheNorthAtlantic Oscillation(NAO) for example, difficult accessperiods.These variationsareknowntooccurindecadalcyclesas, decadal –generalvariationinstormtracksimpactingfrequency ofhighenergy or operations andmaintenance(O&M)accessonayear-on-year basis annual –sustainedperiodsofstormandcalmaffectingsite performance,and seasonal –fluctuationsinperformanceandaccessibilitydue tostormfrequency v ariabilit y Handbook ofoffshore forecasting services 37 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 38 . D 3.6 UK
mana g ement (Hulme CIRIA C666 et al , © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666
life
c y cle CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 4.1 idealised marinerenewables project Schematic ofwork programmeandknowledge transferthrough thelifecycle ofan throughout theproject. continued managementoftheinformationandknowledgebasebeingdeveloped related issuesisfundamentaltothesuccessofeachphase,alongwitheffectiveand It isstressedthatadequateconsiderationtothemarineenvironmentandmetocean when leaseawardandconsentsareawaited. amounts oftime.Furthermore, significantlagsmayoccurinthetimelineatpoints for eachphase,notingthatdifferenttypesandsizesofdevelopmentwilltake different Figure 4.1alsoincludesanindicationofaprojecttimelinealongthedevelopmentpath 41 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 42 . PROJECTR 4.3 measures include: Project riskscanbemitigatedandmanagedbyfollowinggoodpractice.Riskmitigation sufficient riskassessments. should alsobeinplace,andproceduresestablishedbasedonsuitable Construction (Design&Management)Regulations2007.Emergency arrangements Health andSafetyatWork Regulations1999 aswellarequirementofthe safety, anditisalegalrequirementforeveryemployerundertheManagementof safety guidelines.Riskassessmentisakey activityinthemanagementofhealthand manner, sotheover-archingrequirementsformetoceandataaredrivenbyhealthand Construction activitiesshouldbecompletedinasafeandenvironmentallysensitive add anunacceptablefinancialrisktotheproject. consent purposesordesign,constructionandoperationmaintenancephasescould modelling maybeofsufficientqualitytosupportsiteselection,itsfurtherusefor been performedonthatdata.For whilehistoricaldataandhind-cast example, accuracy andlimitationsremainingwiththedataalonganyanalysiswhichhas When anysuchdecisionisbeingbasedonmetoceandataitnecessarytoconsiderthe associated plannedO&Mshouldbeundertaken tominimisecosts(Section7.4.3). approaches throughthoroughappraisalofdowntimeandweatherlimitsonvessels Weather riskisamajorfactorinalloffshoreoperations.Knowledgeofthesiteandits terms forinsurancecover. Certification ofengineeringrepresentsgoodpracticeandshouldhelpsecurebetter Risk offailureindesignundermetoceanloadsmaybecatastrophicforaproject. toolbox talkspriortomobilisation. documented usingriskassessmentpractices.Theseshouldincludevesselauditsand For healthandsafety, allon-siteoperationsshouldbecarefullyplannedand engineering, financialandenvironmental. tohealthandsafety,The areasofriskwheremetoceanissuesarerelevantextend projects that,ifunderestimated,mayleadtoincreasedprojectrisk. needed. However, metoceanissuespresentsignificantchallengestomarinerenewable consideration ofamultitudeissuesbeyondthoserelatedtometoceanconditionsis The subjectofriskmanagementisrelevanttoanyoffshoredevelopmentandcareful between AprilandOctoberin UKwaters,buttherearelikely toberefinementswithin construction activitiesaspossible duringthesummermonths.Thiswillusuallyfall The mostobviousmitigation of metoceanriskistoscheduleasmanycritical scheduling ofcriticalconstructioninthesummermonths accurate forecastingtodirectactivitiesappropriatethe conditions. construction vesselsandequipment capabilities, andtomaximisetheefficientuseofspecialist and expensive appropriate activitiestotake placeaccordingtotheconditionsandvessel allowing for construction planningmethodologythatbuildsinflexibility minimised maximising useofonshoreconstructionsothatoffshore activityis I SKS CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Key referencesrelatedtoriskmanagementare: fog. considered, includinglikelihood ofnumberdayswhenvisibilityisreduceddueto this windowaccordingtothesitelocation.Itisimportantthatallweatherfactorsare Risk managementinmarineandsubseaoperations Marine riskassessment (DNV, 2001) (DNV, 2003). 43 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 44 5. 5P 1 contribute toEIA,gapanalysis,conceptualdesignandresourcevalidationexercises. feed intosubsequentstagesofdevelopment,especiallyinthepre-consentstageto managed usingadatamanagementplan(seeSection3.2).Thisshouldbeavailableto that anyinformationcollatedfromthisstageofprojectdevelopmentshouldbe project tobesufficientlyinformedapplyforalease(Figure5.1).Itisrecommended conduct initialanalysisofmetoceandatatosupporttheseactivitiesandenablethe It isanticipatedthataperiodofbetweenoneandtwomonthswouldberequiredto development whichincludes: ofthepresentguidelinespre-leaseissuescoverinitialstageinproject In thecontext OVERV re project feasibility. site selection - lease I EW
issues CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 5.1 Pre-lease activitiesandlinkages 45 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 46 . S 5.2 per unitareatoensurethebestuseofseabedforpoweroutput. totheamountofinstalledcapacity area thenthedecisiontoprovidealeasemayextend sustainable useoftheseabed.For caseswheremultipleinterestsaretargeting asingle financial considerations,andaregardastowhetherthedevelopmentpresentsmost Decisions onawardingaleasewillinvolvenumberofcriteria,includingtechnicaland support anapplicationtotheownerofseabed. lastingaboutonetotwo months,isadequatetodevelopsufficientdetail exercise, At thisinitialstageofprojectdevelopmentitisanticipatedthatarelativelylow-cost determine outlineprojectfeasibility. to determineoptionsforfavourablesitesdevelopmentthatcanthenbescreened project lifecyclerelatestopre-leaseissuesthatarelargely basedondesk-basedreviews development rightsfromtherespectiveownerofseabed.Soinitialstagein The firstmilestoneforaprojectistosecureanagreementleasewithexclusive structures ontheseabed,includingcables. developments inUKwaterswillrequirealeasefromTheCrownEstatetoinstall resourcesinthewatercolumn.Inmostcasesmarinerenewable rights toexploit oftheUKContinentalShelf.However,the extent TheCrownEstatedoesnotownthe continental shelfwithinarenewableenergy outto200nm, zone(REZ)whichextends vested rightstoTheCrownEstatelicencethegenerationofrenewableenergy onthe oil,gasandcoal).MorerecentlytheEnergyUK ContinentalShelf(excluding Act2004 andutilisethenaturalresourcesof limit,includingtherightstoexplore territorial The CrownEstateownsvirtuallytheentireseabedoutto12nauticalmile(nm) Atlas ofUKmarinerenewable energy resources inter-annual variations.Aprimary tooldesignedtoassistthesiteselectionprocessis comparative assessment,but by itselfmaynotrevealsufficientdetailofseasonaland High-level screeningusingdata providingbroadscalesynopticcoverageishelpfulfor the synopticvariationinresourceoverlong-term. data archivesofwind,waveortidalstreamthataresufficient durationtocharacterise suited tothespecificdevicecharacteristics.Inherently, thiswillbebasedonmetocean The primarycriterioninsiteselectionisaminimumlevel ofpotentialresourcemost detailed activitiesarelikely tobeprohibitiveintimeandcost. information andmovetositeinvestigation,butatthe selection stagethesemore on development.Subsequentphasesarelikely toneedrefinementofthisbase published dataandreportstoestablishcriteriaforpotential resourceandconstraints The processofsiteselectionisessentiallydesk-basedandwilldrawfromexisting wave andtidaldemonstrationscaleprojectsarenotthesubjectofSEA(DTI,2005). responsibility ofdevelopingaSEApresentlyrestswithDTI.Notethatthepresentphase further commercialroundwhichinvitesinterestinmarinerenewabledevelopment.The Round 2offshorewindfarmprojectsanditisanticipatedtobethecaseagainaheadofany completion ofastrategicenvironmentalassessment(SEA). For full-scale commercialdevelopmentsthisactivityisnormallypromptedbythe sitebasedonprojectfeasibility.a preferred developer mayconsideroneormoresitesatthisstage,withtheprospectofidentifying The firstactivityforanymarinerenewableenergy projectistheinitialsiteselection.A I TE SELECT I ON (DTI, 2004),andtheaccompanying freeview This hasbeenthecasefor CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 5.2 height. Bottom right: Annual mean wind speed (courtesy DTI)height. Bottomright:Annualmean windspeed(courtesy Peak meanspringflow. Top Annualmeanwave right:Meanspringtiderange.Bottomleft: Example resourcemapsfromtheAtlasofUK marinerenewable energyresources.Top left: and offshorewindavailablefromtheatlas. GIS. Figure5.2illustratessomeoftheprimaryresourcemapsfortidalstream,wave 47 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 5.2 Table 5.1 48 Notes: Sources ofmetoceanmeasurements Broadscale metoceandatatoinformsiteselection with suggestedsourcesforsuchinformation. broadscale metoceandataandTable 5.2site-specificmetoceanmeasurements,along ofthepotentialresource.Tablemore robustexamination of 5.1summarisesexamples The combinationofbroadscaleandsite-specificmeasurementsshouldprovidefora prudent tounderstandanysuchlimitationsifusedvalidatethebroadscaledata. sea surfaceandwillnotprovideadirectindicatorofwindspeedsathubheights.Itis For offshorewindmeasurementsfromMAWS example, mayberelativelyclosetothe fulfilled aspecificdatarequirementthatisseparatetoanymarinerenewableinterest. metoceanmeasurementswillhave obtain. Itisalsolikely thatthemajorityofexisting patterns, butdatacoveragemaybesparse,highlysite-specificanddifficultorcostlyto Existing fieldmeasurementsmayprovideimprovedlevelsofdetailintemporal Other usefulreferencesforsiteselectioninclude: typical questionsrelevanttothe siteselectionphase: throughout aprojectlifecycle. Thisinformationcanthenbeusedtoanswersome database. Itwouldbetheintention tomaintainthisdataandknowledgebase to supportsiteselectionand document thesedetailsintheformofametocean It isgoodpracticetorecordthecombinationofmetocean dataandreportsassembled Offshore wind Offshore Waves Tidal flows Tide level wind Offshore Waves Tidal flows Tide level Water depth Potential resource UK tidalstream energyresource assessment Quantification ofexploitabletidalenergyresources inUKwaters Change Institute,2005) tidal powerandtheirimplicationsforlarge-scaledevelopmentscenarios anassessmentofthevariabilityUK’swaveand Variability ofUKmarineresources – Tidal stream resource andtechnologysummary Broadscale metoceandata Metocean measurement data areavailablefrom
issues CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 6.1 Pre-consent activitiesandlinkages EIA and achieving consent is likely to exceed aperiodoftwoyears. EIA andachievingconsentis likely toexceed required forbirds,maytake uptotwoyears.Overall the timescaleforcompletingan parameters, suchaswindsand waves.Otherenvironmentalstudies,suchasthose investigations targeted onsecuring sufficientknowledgeofseasonalvariabilityinkey activities maybebetween6and18months,linked tocompletinganyinitial site As anoutlineestimate,thetimescalerequiredtoundertake pre-consentmetocean pre-lease stage.Inaddition,thenatureofsuchtasksmay also requirespecialistinput. therequirementsin require asubstantialinvestmentinfurtherdatawhichexceeds These moredetailedactivitiesinherentlyrepresentagreater costandarelikely to 51 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 52 6.3 GAPANALYS 6.2 consider issuessuchas: further datamightberequiredtofillanygaps.Thegapanalysiswillalsoneed the projectlifecycle,confirmonsufficiencyofpresentdataholdingsandidentifywhat The gapanalysisprocesswillseektoconfirmtheoverallinformationrequirementsfor to mitigateorremovethatrisk. significant issueassociatedwithadataset,gapanalysiswilldeterminewhatisneeded environmental issueswhichrequirefurtherdata.Whereriskprofilinghasidentifieda Note thattheEIAscopingphaseandconsultationprocessmayraiseanumberof specialists. betweensuch identify andplanforopportunitiesofdatainformationexchange gap analysistoenableabetterunderstandingofrespectivedatarequirements,and strategy. Itisrecommendedasgoodpracticetoinvolveallspecialistsintheprocessof and resourcevalidation,butalsootheractivitiessuchasdevelopmentofanO&M support subsequentstagesoftheprojectlifecycle,especiallyEIA,conceptualdesign A gapanalysisisrequiredtounderstandthecontinuedsufficiencyofusingthisdata initiated duringthepre-leasestage(seeSection5.1). information needstobemanagedandmaintainedintheformofaprojectdatabase, the immediaterequirementsofsiteselectionandprojectfeasibilityactivities.This project atthestartofpre-consentactivitiesandwillhavebeenassembledtomeet It ismostlikely thatonlyalimitedamountofmetoceandatawillbeavailabletothe not practicalineverycase,the opportunitytocombineinitialanddetailedsite stated objectivetodetermine fulfilmentofthesefurtherdatarequirements.Although further projectrequirements reliantongoodmetoceandata.Thesurveyalsorequires a specific metoceansurvey. Thescopeofthemetocean survey needstoconsiderall Initial siteinvestigationsmayincludearangeoffield amongwhichisa available tosupporteitheractivity, asdeterminedfromgapanalysis. decommissioning stages).Siteinvestigationswillberequired ifthereisinsufficientdata affected bythedevelopmentduringitsdeploymentperiod (construction,operationand whereastheEIAaims toassesshowtypicalmetoceanconditionsmaybe occurrence), eventswith a lowprobabilityof engineered towithstandsevereconditions(extreme issues, thedesignprocesswilltypicallyconsiderhowscheme needstobe ofmetocean is requiredtomitigateasignificantenvironmentalimpact). Inthecontext to overlapinprogrammeandattimesmayrequireiteration (egadesignmodification respective activities.Theseactivitiesarephasesofworkthatcloselylinked, arelikely Both EIAandengineeringdesignrequirerobustmetoceandatatounderpintheir collect newdata). the formofadditionaldatapurchase(whereisavailable)orsiteinvestigations(to to meettherequirementsoffurtherprojectactivities.Suchdataacquisitionmaybein From thegapanalysis,specificationsforadditionaldataacquisitionwillbeestablished I N I T frequency). data quantity(coverage/resolutionacrossadevelopmentsiteandinduration/ data quality(accuracyanderror) I AL S I TE I I NVEST S I GAT I ONS CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 physical oceanographicdata,including: ofvarioustypes(mainly) collection, processing,qualitycontrolandexchange guidelines (availablefrom
wind I DAT I ON 59 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Box 6.2 60 Case study:Installationofametmast assessment include: direction andthreesecondgusts(Figure3.3).Usefulreferencesforwindresource Standard resourcemeasurementswouldinclude10minuteaveragewindspeedand turbines thoughthepost-constructionperiod. conditions tobemonitoredthatcanassistinperformancevalidationoftheinstalled the finalwindarray, anup-wind metmastmaybeinstalledtoenableincidentwind construction, andO&Mstrategiesactivities.Dependingonthelocationrelativeto years andthroughconstructiontodeliveradditionaldatasupportdesign, secure investmentinprojectconstruction.Themetmastmayremainonsiteforseveral as afundamentalstageindemonstratingthecommercialviabilityofprojectandto remains represents amajorcosttotheproject,butvalueofvalidationexercise including atmosphericpressure,temperature,humidityetc.Suchaninstallation The mastisalsolikely tobeequippedmonitorastandardsuiteofmetparameters, Figure 6.3 Installation: Mitigation: Instruments: Location: Justification: Project: turbines Wind turbinesPart 12-1:powerperformancemeasurements ofelectricityproducing wind programme Wind resource assessmenthandbook.Fundamentals forconductingasuccessfulmonitoring (IEC, 2005). (AWS ScientificInc,1997) completed inlessthan20hours. a carefullyselected weather window theoperationwas successfully the water capacity. depthsandhaving thedeckspace,loadingandlift With jack-up bargeExcalibur was selected for theoperationsasbeingsuitablefor weather andsignificant wave heightfor thedurationofinstallation.The minimise downtime. vessel operatingthresholdsandoptimisationofinstallationschedulesto to theinstallationsite alsoallowed for definition ofinstallationandservice andboatlandingsites.ladders Knowledge ofthemetocean conditionslocal mast. Theseincludedthelocationitself,aswell astheorientationofaccess decisions includingdesign,accessandinstallationmethodology for the met atmospheric pressureandfog. for GPRStelemetry datatransfer. above meansealevel. Inadditionthemet suite logstemperature, engineering analysesanddecisions,includingthelocationofmet mast. campaign was carriedoutto inform boththeenvironmental and GIS databaseofdatathrough theexecution oftheEIAprocess. Ametocean significant inthecontext ofresourcevalidation requirements. mast was installedsincesite variations were consideredunlikely to be making duringtheconstructionandpost-constructionphases.Asinglemet decisions, andlive feed information likely to inform operationaldecision purposes, withthedataalsobenefiting detailed designandengineering Specialist services were employedSpecialist services to provide site-specific forecasts for wind, The detailed metocean andgeophysical surveys informed awiderangeof The met mastincludesatotal ofnineanemometers placedat40mto 85m WindLimited (GGOWL)Greater compiledanextensive GabbardOffshore Installation ofthemet mastwas primarilyjustified for resourcevalidation Met mast installation (courtesy GGOWL) (courtesy Met installation mast WindFarm,Greater ThamesEstuary GabbardOffshore CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 .. W 6.6.2 WEC deviceperformanceprotocol: although commentonconductingwaveresourcemeasurements isincludedinthedraft At presentthereisnostandardinplaceforresourcevalidationmethodologies, Standards quality. The dataprovidershouldbeabletocapturetheseissuesin statementsregardingdata this potentialforunder-predictiontoaroundsevenpercent. determination ofwavepower. Increasingthesamplingperiodto60minutesreduces (95percentconfidence)ofabout10inthe duration couldresultinanerror consideration. Pitt(2005)reportedthatasamplingregimebasedon30minutes In aseparatestudyforEMEC,theissueofsamplingintervalswasgivendetailed oil andgasapplications. regime canberelaxed to three hourlyintervals,whichisamorestandardintervalfor WaveNet), whereasfordeeperwatersiteswhere tidaleffectsareminimal,thesampling regime. For thesesitesanintervalof30minutesisrecommended(comparableto measurement intervalisrequiredtoresolveeffectswhichmaymodulatethewave For areas pronetoshallowwaterinfluencesandstrongtidalvariationasuitable Sampling regime those considered,especiallyfordeepwatersites. work wasthatthewavebuoysremainmostreliableandwell-proventechnologyof satellite observationsandthemoretraditionalwavebuoy. Theconclusionfromthis studies atWaveHub, includingHFRadar, dopplerprofiler(ADCP), acousticcurrent Pitt (2006)reviewedanumberofwavemeasurementdevicesforresourcevalidation option, withWaveNet ofaneffective approach. beinganexample Directional wavebuoysequippedwithtelemetrylinksarelikely tobethemostpractical Measurement device Validation ofthewaveresourcerequires Duration andlocation WaveHub. resource validationstudiesintheUKtodateapartfromeffortsatEMECand Given thepresentstatusofWECprojectstherehavebeenveryfewcaseswave period mayberequiredifsignificantdatalossisexperienced. overthefootprintofdevelopmentsite.Extensionstodeployment expected months andforasufficientnumberofsitestodescribemajorvariabilitywhichmightbe a v Preliminary waveenergydeviceperformance protocol supportingcommentary Preliminary waveenergy:deviceperformance protocol es in situ monitoring foraminimumperiodof12 (DTI, 2007) (DTI, 2007). 61 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Box 6.3 62 Case study:WaveHub available from
stream in situ monitoring foraminimum (DTI, 2007). (DTI, 2005). 63 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 64 7. 7P 1 may lastbetween6and18months. As anestimate,theperiodrequiredtoundertake pre-constructionmetoceanactivities in relationtooffshorewindandwaveprojects. During thisstageoftheprojectresourcevalidationislikely tocontinue,especially development include(Figure7.1): construction. Activitiesthatarelikely tobeadvancedduringthisstageofproject milestoneofpreparingfor Projects thatachieveconsentcanmoveforwardstothenext OVERV re planning andprocurement. O&M strategy detailed design detailed siteinvestigations consent conditions - construction I EW
issues CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 7.1 Pre-construction activitiesandlinkages 65 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 66 . DETA 7.3 CONSENTCOND 7.2 Strangford Lough provides the only recent example ofconsentconditionsforaTEC. providestheonlyrecentexample Strangford Lough The FEPA Turbines licensegrantedtoMarineCurrent tooperatetheSeaGendevicein research advisorygroup(RAG)withfurtherprogressawaitinginitialdevicedeployment. this recommendationhasbeenacceptedasaresearchprioritybythepan-government provides recommendationsfor research reportpublishedforCCWandTheCrownEstate(ABPmer, 2006)and ofdevices.Thetopicenergy isreviewedinarecent adopting arrays extraction projects increaseinscalefromsingledemonstratorsthroughtocommercial reduction willbeaddedtothelistofmonitoringrequirementsandremainas For WEC andTECdevicesitisgenerallyantiquatedthattheeffectsofenergy approved theinformation. The CrownEstateaspartoftheleaserequirement,onceconsentingbodyhas anticipated thatnewprojectswillalsoberequiredtosubmitthesedataandreports required tobesubmittedtheconsentingbodyatendofeachyear. Itis annual basisoveraperiodoffewyearswithreview. Monitoringreportsare construction, constructionandpost-construction,thelatterbeingrepeatedonan Monitoring relatedtotheseissueshasgenerallybeenrequiredforperiodsatpre- Morphology. 3 Suspendedsediment. 2 Scour. 1 offshore windhavetendedtobegroupedintothreeheadings: adopting mono-pilefoundations.To datemetoceanrelatedconsentconditionsfor evidencebaserelatedtooffshorewindprojects,especiallythose from anexpanding At thepresenttimeregulatorisdevelopingagoodunderstandinganddrawing to beusedastheprimarytoolforaddingsuchconditions. retained fortheconsentandanysitespecificissues.ItiscommonFEPA licence will haveparticularregardtothetechnologytype,anyremainingdesignoptions the evidencebase).Consentconditionswillbedevelopedonacase-by-casebasisand response totheEIAprocessandlevelofunderstandingavailable(iestatus regulator atthepointofgrantingconsent.Suchconditionsaregenerallyframedasa Consent conditionsnormallyrelatetothedegreeofuncertaintyremainingwith regular forecastsfordailyplanning. should besufficienttocharacterise thelikely working conditions, supplementedby metocean knowledgebase downtime, forecasts)(Section 6.3).At thispointtheexisting metocean conditionsforsafe marine operations(egvesselselection,surveyplanning, As withinitialsiteinvestigations,anysurveymethodology willneedtoconsiderlocal considered, todetaileddesignwherefinalchoicesaremade. conceptual design,whereseveralsolutionsfordifferentaspects oftheprojectmaybe investigation workwillbespecificallytargeted toassistmoving the projectfrom site investigationworkmaybenecessarytoconfirmtheproject design.Suchsite detailed design,andfollowinginitialsiteinvestigations,then furtherandmoredetailed If significantdatagapsremainatthepre-constructionstage requiredtosupport I LED S I TE I NVEST I T I ONS in situ I GAT monitoring arounddevices.It I ONS is understoodthat CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 . DETA 7.4 good practiceforconsideration atanearlystageintheprojectmethodology. This approachisconsistentwith theCDMRegulations2007andisrecommendedas SiteaccessdowntimeanalysisforconstructionandO&M. 3 Operationalthresholds. 2 FMECA(failuremodesandeffectscriticalityanalysis)for: 1 metocean designstudywillincludedetailssuchas: develop aconsistentknowledgebaseforeachcontractor. Itisanticipatedthatsucha substantial savingscanbeachieved.Thisroutetoprocurementofconstructionhelps themselves bycommissioningametoceandesignstudy, ithasbeenfoundthat In caseswherethedeveloperhaschosentoprovidearelevantsetofdesignparameters an inefficientandpossiblyarbitraryprocess. overall buildcosts.Thiscanmake bidcomparisonandsubsequentcontractorselection outcome ofthisapproachmayalsoproduceverydifferentsolutionstodesignaswell investment indataandanalysis)putintodevelopingthecostofconstruction.The contractor whichwillvaryaccordingtothelevelofeffort(includingindependent inevitable thattherewillbedifferentfront-endconsiderationsdevelopedbyeach and attimesresultedinincreasedareasofuncertainty. Withthisapproachitis considerations ofprojectdesignriskshasnotalwaysbeenconsistentbetweenprojects quality ofsite-specificmetoceaninformationreachingthesecontractorstoassisttheir fall toabuildcontractorselectedthroughcompetitivetendering.Thesupplyand For commercial scaleprojectsitislikely thattheresponsibilityfordetaileddesignwill devices foronshoremaintenance. final design,especiallyinrelationtoaccessontostructuresormeansforrecovering data andfurtheron-siteresourcemonitoring.TheO&Mstrategywillalsoinfluence the basisforconsentingproject)alongwithadditionaldetailedsiteinvestigation The maininputstodetaileddesignwillincludetheinitialconceptual(usedas (CDM) Regulations(2007). Design shouldbeinaccordancewiththeConstruction,(DesignandManagement) further justificationforadditionalmetoceandatacollectioneffortatthisstage. devices (suchasmetmasts,wavebuoysorADCP),itisunlikely thattherewillbe issues. Whilethereislikely tobeongoingdatacollectedfromresourcemeasuring routes andwithregardtootherconstraints,suchaswake effectsandnavigational positioningforthestructuresormooringsandcable requirements anddetermineexact The resultsofthesedetailedinvestigationswillbeusedtofinalisethefoundationdesign Typically, detailedsiteinvestigationsarelikely tofocusonmoreintensive: Fatigue considerations. b conditions. Extremeandjointprobabilityextreme a geotechnical surveys(seabedsoilprofile). or obstructions) geophysical surveys(egbathymetry, nearsurfacesoilconditionsanddebris I LED DES I GN 67 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 68 DNV isintheprocessofdraftingcertificationstandardsforWECandTECdevices: by anindependentcertificationbody. The outputfromthisactivityisafinaliseddetailedprojectdesignwhichwillbecertified installation. power, thechoiceofstandardswillbemadeaccordingtomostapplicablefor appropriate ISOandIECstandardswhererelevant.Inthecaseofwavetidal (RP series)giveguidancetothedesignofoffshoreinstallationsaswell onshore shouldbe.DNVoffshorestandards(OSseries)andrecommendedpractices kept toanabsoluteminimumandwhatcanbeconstructedoreconomicallymaintained In allcases,thegeneralphilosophybehinddesignshouldbethatoffshoreactivitiesare metocean conditions. Table 7.1isasummaryofthedesignissueswhichrequiresomeconsideration andfatigueissues: which includesdetailsonenvironmentalloads,extremes HSE haspublishedageneraldiscussiononloadsinanOffshoreTechnology Report, GL haspublishedacertificationguideforTECandoffshorewinddevices: banks andchannelsmayneedseveralsitestocharacteriseeachoftheseenvironments. seabedformedof overacomplex single location,whereasasmallersiteextending large overarelativelyflatseabedtobecharacterisedby openwatersiteextending sites chosentocharacterisedesignconditions.For itmaybepossiblefora example, development area,anissuewhichwillguidedecisionsontheamountandlocationof the potentialforspatialvariabilityofmetoceanconditionsacrossfootprintany wind, waveandtidalstreamprojects.Ineachcasetheanalysisprocessshouldconsider outlinestheprinciplemetoceanissuesforconsiderationinoffshore The followingtext Offshore wind Loads Guidelines forthecertificationofoffshore windturbines (GL Wind,2005) Guidelines forthecertificationofoceanenergyconverters.Part 1:Oceancurrent turbines Certification oftidalandwaveenergyconverters (HSE, 2001). (DNV, 2007). (GL Wind,2004). CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Table 7.1 Design choicesthatwillbeinfluencedby metoceanconsiderations considerations. willneedtobe modelledfordesign conditions onthewavespectrum andcurrents to theseasurfaceandarelikely topresentlittlewindage. However, theeffectofwind Wind itselfwillnotsignificantlyinfluencedesign,sincedevices aregenerallylowlying The dominatingmetoceanissuesforWECdesignare: the availablewaveenergy isatitshighestandcoincidingwithpeak energy demand. the devicedesignwillbeoptimisedforpoweroutputduringwintermonthswhen conditions.Itislikely that prevailing siteconditions,andforsurvivalunderextreme WEC devicedesignwillneedtobeoptimisedformaximumpowerdeliveryunderthe Wave (WEC) A furtherdocumentprovidingdetailsonoffshorewinddesignis: discussed in: Design ofoffshorewindturbinefoundationsandstructuresiscomprehensively interaction and tower Foundation piece design Transition and design selection Foundation: depth and burial Cable route Site layout Design variation aboutmeanwaterdepth. current wave spectrum Part 3:designrequirements foroffshore windturbines Wind turbines– Design ofoffshore windturbinestructures Wake ofadjacent turbines effects Natural frequency structure environmental dynamicforces onthe J-tube design–external tubesincrease extreme sealevels Height ofladderplatforms inrelationto and platforms for prevailing conditions Height andorientationofaccessladders and vessel/crane limitations Instability splash zone Severely aggressive environment in tide, wind,waves andmarinegrowth Environmental ofcurrent, loadeffects water movement duetoErosion andsedimenttransport prevailing conditions Wind-wake for effects therangeof Major metoceanconsideration given site conditions specific (DNV, 2004). operating range Turbulence ofturbinesinnormal effects Wind loads water levels andwave height Extreme andjointprobability analysisof direction Tidal range,waves andcurrents operating thresholds Downtime analysisagainstvessel Upper andlower limitsofsplashzone analysis wind, wave andcurrentloads,fatigue of Extreme analysisandjointeffects waves inthenearshore of steep depthchangesandbreaking especiallyinareas sediment transport, Analysis ofwater movement and operating range Turbulence ofturbinesinnormal effects Data required (IEC, 2005a). 69 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 70 7.4. 1 from pointabsorbers). to anywakeflows(apart effectsandtotheorientationofdevicesanycurrent ofwaveenergyLayout convertersaroundthesitewillneedtobemadewithreference of theriskmarinegrowthondevice,umbilicalsandmooringcomponents. of theriskinmobilisinglocalseabed.Inaddition,considerationneedstobemade asaloadfactorontheanchorchains,butalsointerms forces ofwaveandtidalcurrent wave conditionsforthesite.Mooringdesignneedstotake intoaccountthecombined In allcases,mooringsandumbilicaldesignneedstowithstandthepredictedextreme Further guidanceforWECdesignisfoundin: areas offastflowingwatertheseabedmaybescouredto rocklevelinmanyplaces. cables perpendiculartothetidalflow. Cableburialisunlikely tobeemployedsince in orwherethereisarequirementtolaythe where moreerosiveenvironmentsexist, benign. However, rockdumping,mattingand/orcableprotectorsneedtobeemployed where cablesarelaidinparallelwiththetidalflowandrockstratumisrelatively protection willrequirecarefulconsideration.Cablearmourmaybesufficientatsites cable andexport Due tothenatureofsitesselectedfortidaldevices,interarray flood tides,andgenerallyfavouringthosesiteswhichhaveastronglyrectilinearaxis. normally selectedfortheiruniformityofdirectionflowthroughperiodsebband sitesare Not alldevicesaredesignedtorotatewiththetidalstreamandpreferred tidal streamandfixed to the seabedeitherbypiledfoundationsordynamicmoorings. Most designsmimicthewindmillconceptofahorizontalaxisrotorsecuredtoface Designs forTECdeviceswillbeinfluencedby: consequently areunlikely tofallwithinanysetofmeasured data. atvery lowfrequenciesieonceevery50years,and repeat intheiroccurrence conditions arelikely to survive suchconditions(iewithstandpeakloads).Theextreme accounted forinanyoffshoredesign,ensuringthedevelopment issufficientlyrobustto peak valuesofmetoceanconditionsorcombinations thatmayneedtobe Extreme conditionsrepresentrareevents(nominallystorm conditions)thatdeliver Ex Tidal stream(TEC) treme devices application ofengineeringstandards andrecommended practicesforwaveenergyconversion Guidelines ondesignandoperationofwaveenergyconverters.Aguidetoassessment wake effectsofadjacentunits orlocallandmasses. analysisofsurfacelayerloadeffects extreme surface conditionsforaccess offlowfordefinitionsurvivalconditions extremes variation oftheflowthroughwatercolumnandheightboundarylayer bi-directionality offlowbetweenfloodandebbtides
(DNV, 2005). conditions CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 convention istocentreonstandard compassbearingsasfollows: increments of45°and30°,respectively). Wheneightsectorsareadoptedthen becomes relevant,withthenumberofsectorscommonlybeing either8or12(with For omni-directionalmetoceanparameters,suchaswindandwave, asectoranalysis may increaseforlongerreturnperiods. intheextrapolation standard error eventsuptoreturnperiodsofaround1in30-years. Consequently,extreme the toderive anestimateof a reliablestatisticaldistributionwhichcanbeextrapolated length oftheinputrecord.For a10-year timeseriesshouldbeabletoprovide example, probability distributionreducesforreturnperiodsgreater thantwoorthreetimesthe ofthe It isgenerallyregardedthatthestatisticalconfidencein extrapolation distribution. signature oftheextremes analysisonoccasionswhenkey eventsmaymodifythe prudent torevisitextreme effects maysimilarlyinfluenceothermetoceanparameters.Furthermore, itremains that mayrelatetonon-randomtrendssuchassealevelrise.Otherclimatechange data aroundalong-termmeanvalue.For waterlevels,thisnormallyfiltersoutissues data andfilteroutanyseculartrendtoensurethereisnobiasinthedistributionof Extreme Variate, GeneralisedParteo Distributionetc.Thefirsttaskistopreparethe the marginal usingtechniquessuchasWeibull, extremes, Fisher-Tippett, Generalised reliesonfittingaprobabilitydistributionfunction(PDF)to The meansofextrapolation deep waterwaveconditionsintoshallowsites(seeBox6.1). MCP methodsornumericalmodels,suchaswavetransformationmodelsthatmodify suitable methodsneedtobeemployeddevelopthedatathatsite.Thismayrelyon If thelong-termrecordisnotimmediatelycoincidentwithsiteofinterestthen probability distribution. marginal eventstolowerfrequencyreturnperiodsbasedonafitted extreme the (storm)events,andextrapolate record thatcontainsanadequatesampleofextreme conditionsistoanalysealong-term The standardmethodologyforquantifyingextreme valuestatisticsarerequiredfor: In full,theextreme conditions. sea life, ie50or100yearstoensuresurvivaloftheinstallationunderextreme design processneedstoconsideranupperreturnperiodthatislongerthantheservice upgraded turbineunitsmayhappenonshortertimescales.Overthistimescalethe for foundationunits,notingthatopportunitiesre-poweringtheprojectwith to theservicelifeofscheme,whichforoffshorewindmaybebetween2550years toasareturnperiod.Thechoiceofperiodneedsconsideration period, referred onaverageonceoveraspecifiedtime (event) withaheightthatisonlyexceeded toasthedesignwave.Thewaveisanindividual commonly referred For waveconditions, offshorestructuresthemaininterestislikely tobewithextreme Uni-variate parameters currents (includingsurgecurrents contribution). wave heights water levels(includingsurge contribution) winds (includinggusts) 71 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 72 Table 7.2 Example oftabularpresentationfordirectionalwave extreme values. Basedon30 parameters isgivenin: metocean which wavesmaybreak.Adetaileddiscussiononderivingvariousextreme large wavesthelimitingconditionswouldbewavesteepnessandwaterdepthbeyond anylimitingcondition.Forcondition remainingphysicallyrealisticandnotexceeding valuespredictedatthispoint,inrelationtothederivedmetocean on theextreme thereshouldbejudgement As thePDFispurelyamethodofstatisticalextrapolation valuesalongsidethesepredictions. report thestandarderror return periods,commonly: 1,2,5,10,20,50and100-year. Itisalsoinformativeto Using thebest-fitPDF, valuepredictionscanbereadilyderivedforasetof theextreme including standarderror, thefinaldecisioncanbebasedonwhatfitsdatabest. The choiceofPDFisafairlyarbitraryprocess,andwithconsiderationissues become relevant. although hereitismoreprobablethatonlydirectionsofpeakfloodandebb speeds, In somecasesitmayalsobeappropriatetoprovideasectoranalysisforcurrent extreme waveeventsafterfittingageneralised Pareto distribution PDFtothedata. extreme the levelofagreementbetween themarginal waveeventsandthepredicted extreme ofdata forthe30°sectorbetween180and209°Ntoshow Figure 7.2presentstheextract prediction. of waveheights,broken down intodirectionalsectors,andincludinganon-directional Table estimate tabularpresentationforauni-variateextreme 7.2providesanexample totherequiredhigherreturnperiods. values andthebest-fitPDFextrapolated and tabularform.Thegraphicalpresentationwillincludeboththemarginal extreme analysisresultstobepresentedinbothgraphical It isgoodpracticefortheextreme South-East South South-West West North-West North North-East North-East East Return period (yrs) 100 50 20 10 5 2 1 Environmental considerations 4.68 4.48 4.22 4.02 3.83 3.56 3.36 029 000 to 4.44 4.64 5.09 4.90 4.22 3.93 3.69 059 030 to centred on315ºN, spanning292.5to 337.5ºN centred on270ºN, spanning247.5 to 292.5ºN centred on225ºN,spanning202.5to 247.5ºN centred on180ºN, spanning157.5 to 202.5ºN centred on135ºN, spanning112.5 to 157.5ºN centred on090ºN,spanning067.5 to 122.5ºN centred on045ºN,spanning022.5to 067.5ºN centred on000ºN,spanning337.5 to 022.5ºN 4.26 4.20 3.58 4.01 3.91 4.10 3.74 089 060 to 4.69 4.42 4.06 3.79 2.87 3.15 3.51 119 090 to (HSE, 2001b). 3.84 3.60 2.93 2.70 3.21 4.01 3.41 120 149 Directional sector(°N) to 4.49 4.43 4.34 4.25 3.99 3.85 4.15 150 179 to 5.22 4.59 4.35 4.91 4.76 5.10 4.14 180 209 to 4.95 4.67 4.46 3.70 3.94 4.24 5.15 239 210 to 4.59 3.22 3.91 4.24 5.07 3.51 5.47 269 240 to 3.82 3.52 2.87 4.91 4.57 4.13 3.14 299 270 to 3.85 3.62 3.45 3.26 3.00 2.79 4.01 300 329 to CIRIA C666 4.36 4.23 4.05 3.89 3.72 3.26 3.47 359 330 to ° sectors 4.64 5.73 5.55 4.92 5.12 5.31 4.41 All © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 7.2 with theunderlyingdatafordirectionsector180to209°N Predicted extreme returnperiodsignificantwave heightscompared locations, waterdepthisusually sufficientforwavestobeeffectivelyindependentof of eachotherunlessthereis some formofinteraction.For inoffshore example, Metocean conditionsgenerated bytheseseparatemechanismswillremainindependent Meteorologicalforcing. 2 Astronomicalforcing. 1 These metoceanconditionsaregeneratedfromtwoindependent physicalmechanisms: following relationships: Typically, theanalysisofjointdistributionmetoceanvariables assumesthe together.occurring conditions (dependency)oftheseextreme by establishingthedegreeofcorrelation design, withcare,byconsideringcombinedprobabilitiesoftwoormorevariables,and occur simultaneously, iethereisareducedprobability. Allowancescanbemadein will conditions(winds,waves,waterlevelsandcurrents) It isunlikely thatallextreme Multi-variate extremes driving physicalprocess). aredependent (representingpropertiesofthesame water levelsandcurrents shallow water areindependent indeepwaterwithincreasingdependency waves andcurrents in shallowwater water levelsandwavesareindependentindeepwithincreasingdependency processes) tides andsurges arepartiallydependent(duetointeractionsbetweenthetwo same physicalprocess) wave height,periodanddirectionaredependent(representingpropertiesofthe generated fromthesamestormconditions) surges, strongwindsandlarge wavesarelikely toshowsomedependency(being 73 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 74 .. F 7.4.2 and isnotsolelylimitedtowaveswaterlevels. called JOIN-SEA(HRW).Themethodologyistransferabletothepresentapplication In 1998,DEFRApublishedajointprobabilitymethodologyforcoastalengineering isstatisticallycorrelated. behaviour ofextremes The formofanydependencecanbeconsideredinrelationtohowwellthejoint conditionstobeassessedonthebasisofdirectionalsectors. extreme As withuni-variateanalysis,thedirectionalvariationofwindsandwavesrequiresthese in areasofstrongcurrent. tide oncetheystarttofeeltheseabed(seeSection3.1.3).Further dependencymayexist tides. Inshallowwater, wavesbecomedependentonthechangesindepthdueto The followingsetoffrequencyanalysisisgenerallyrequired: analysis andfrequencyanalysis. good practiceistostandardiseoneither8or12directionalsectorsinbothextremes tables andgraphs.Theprincipleofgroupingdataintodirectionalbinsalsoapplies,so parameters withconsistentincrementsbetweenrecords,anddevelopedintoaseriesof summaries basedaroundfrequencyanalysisofalong-termtimeseriesmetocean A metoceanstudytosupportengineeringdesignwillcommonlyincludeaseriesofdata seconds ratherthanyears. loads,thecyclicalloadsoperateatmuchhigherfrequenciesfrom contrast toextreme during operationalconditions,andtakingintoaccountissuessuchaswake effects.In considering theloadscausedbyvariouscombinationsofmetoceanfactorswhichoccur Design forfatiguelimitsisrequiredtoassessthecyclicalloadingonstructuresby variate distributions. valuemethodstodetermineuni- document alsoprovidesausefulreviewofextreme may rangefromfullyindependent,partiallydependenttodependent.This The methodconsidersthedegreeofdependencybetweentwosetsvariables,which required, notmeasurements close totheseasurface. Note thatforoffshorewindinstallations theconditionsatequivalenthubheightare further sub-divisionofthesedata toenablefrequencyanalysisonamonth-by-monthbasis. Inter-annual (seasonal)variabilityinwindsandwaveswillalso beofinterest,leadingtoa ati period, T directions andbydirectionsector wave frequencytables(waveheight,H wave scatterdiagramandtables(waveheight,H 1998). (HR, The jointprobability ofwavesandwaterlevels:JOIN-SEA,arigorous butpracticalapproach current speed versus current direction and presented as current roses. directionandpresentedascurrent speedversuscurrent current wave heightversuswindspeed,alldirectionsandbydirection sector roses wind frequencytables(windspeedversusdirection) and presentedaswind g ue
loads p ), andpresentedaswaveroses s , versuswavedirection,andalso s , versuswaveperiod,T CIRIA C666 p ), all © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Recommended incrementsfor useinfrequencyanalysis Table 7.3 followed by an example ofawaveroseinBox7.2. followed byanexample ofawavescatterdiagramandfrequencytableisgiveninBox7.1, A worked example years areusedasinput. to provideanindicationofstatisticalreliability, especiallywhenfractionsofmonths or percentage value.Itishelpfultoreporttheamountofdatausedincreatingeachtable number ofeventsfallingwithineachbinwhichcanalsobenormalisedintoa The reportedunitforfrequencyanalysisrepresentsadimensionlesscountofthe tobelow.probability densityvaluesmightbeexpected records mayleadtounnecessarygapsintheresultingtables,especiallywhere for useinfrequencyanalysis,notingthattheofaverysmallincrementshorter the minimumtomaximumrecordedvalues.Table 7.3offersrecommendedincrements each parameterandtoincrementoverthefullrangeofmeasureddata,iespanning The constructionoffrequencyanalysistablesalsoreliesonpre-selectedbinsizesfor Current direction Current speed Wind direction Wind speed Wave direction Wave period waveSignificant height Parameter Symbol U H Ø U T Ø Ø 10 p c c s (m/s) (m/s) Unit (m) (s) (º) (º) (º) Increment 0.1 to 0.5 30 or45 30 or45 30 or45 0.5 to 1 1 to 5 1 to 2 75 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Box 7.1 76 Example ofwave scatterdiagramandfrequencytables Task: Input: Table 7.4 Wave frequencytable: Wave steepness: Figure 7.3 Scatter diagram: Wave height, Hs (m) 1.0 1.5 0.0 0.5 2.0 2.5 3.0 3.5 >= Total 1.0 1.5 0.5 2.0 2.5 3.0 3.5 4.0 < >= < 0.16 0.16 2 1 0.79 1.97 2.76 3 2 (expressed inpercentoccurrence)adopting0.5mbinsfor H Table 7.4 afrequencytable to quantifytheprobability density offers determine theabsolute contributionofwaves falling into pre-defined bins. frequency tableisusedto complimentthewave scatter diagramand for T wave height(H all months and 4–5saremostfrequentatover 14percentoftheevents. are recordedto aidinterpretation). From Table 7.4 waves between 0.5–1m where wave periodsaremarginallylower. whereas thewind-seacomponentislikely to bethelargergrouping ofwaves density ofcombinationsH of seastates mightbeexpected to follow asimilarlimitingsteepness. estimated, whichinthisexample is the lower amplitudeandlongerperiodwaves (ieH each parameter. From Figure7.3 theswell componentcanbeinterpreted as full distributionofthedataset andto establishupperandlower limitsof Quality checked timeseriesoflong-term wave measurementscontaining xml aefeunytbe(aehih esspro)–alldirections, Example wave frequencytable(wave period)– heightversus On itsown thewave scatter diagramdoesnoteasilyquantifytheprobability The wave scatter diagramallows for alimitingwave steepness to be The raw dataisinitiallyplotted outasH To develop awave scatter diagramandfrequencytable. Example wave scatter diagram 18.67 11.66 6.52 0.50 4 3 p and to spantherangeofdata(note: blanksareusedwhennovalues 14.06 27.66 6.25 6.69 0.62 0.04 5 4 20.98 0.42 2.94 0.01 0.15 5.14 6.16 6.16 s ) andwave period(T 6 5 15.98 3.96 5.04 3.46 0.32 1.06 0.01 2.14 7 6 Wave period,T 9.68 3.52 2.42 0.90 0.72 0.04 1.86 0.21 8 7 s and T 0.89 0.85 0.26 0.02 0.01 0.61 2.91 0.27 9 8 1/16. On this basis, further extrapolation Onthisbasis,further 1/16. p p 0.49 0.34 0.04 0.01 0.11 p 10 (s) ). 9 unless contouring isapplied.Awave s versus T versus 0.30 0.04 0.27 11 10 0.14 0.14 12 11 p (Figure 7.3) to presentthe 0.13 0.13 12 13 s <0.5 andT 0.10 0.10 14 13 0.04 0.04 15 14 s and 1sbins CIRIA C666 0.00 p 16 15 >10 s), 42.26 20.11 27.47 Total 2.52 0.69 0.80 0.00 6.87 100 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Box 7.2 Example ofwave roseandfrequencytables Input: Task: Wave rose: Wave frequencytable: Table 7.5 Wave frequencytable: Figure 7.4
Wave height, Hs (m) 1.0 1.5 2.5 3.0 3.5 0.0 0.5 2.0 >= Total 1.0 1.5 3.0 3.5 4.0 0.5 2.0 2.5 < >= < 21.55 4.58 8.70 5.26 2.05 0.78 0.07 0.11 029 0 wave height(H wave direction). periodversus to south-west. Two prominent wave andsouth directionsarerevealed, to north-east north twelve directionsectors of30ºandusingthe0.5mbinsfor wave height. majority ofthelongerperioddata (events whereT arrived from. Inthisexample, waves between 0to 060ºN accountfor the assist inconfirming whichdirectionthelonger periodswell componenthas wavebinned at1sintervals versus direction.Thisgrouping ofdatacan direction. Table 7.6 summariesthesamedatainterms ofwave period grouped between 0.5to 1minwave height(over 42percent). to 059ºNaremostcommon(over 22percent),withthemajorityofwaves of events. Table 7.5 presentswave direction.Waves heightsversus from 30 direction complementsthewave rose by establishingtheprobability density Quality checked timeseriesoflong-term wave measurementscontaining To develop awave rose andfrequencytable(wave direction, heightversus The raw dataisinitiallyplotted outasH A similarapproach canbetaken whenconsideringwave periodversus A wave frequencytableusingthesamedivisionsinwave heightand Wave frequencytable(wave direction) heightversus Example wave rose 22.03 8.23 9.34 3.52 0.68 0.25 0.01 059 030 10.79 4.59 0.34 0.20 0.04 1.43 4.18 089 060 01.44 3.32 0.05 0.02 1.68 0.12 119 090 s ), wave direction(Ø)andwave period(T 0.69 0.03 1.63 0.91 120 149 Wave direction, 5.43 2.08 2.02 0.91 0.13 0.19 0.10 150 179 20.26 0.67 1.92 3.01 9.01 0.24 5.41 180 209 θ (°N) 4.84 9.95 2.54 0.99 0.23 1.33 0.01 239 210 s versus direction(Figure7.4)versus in 2.36 0.36 0.34 1.03 0.11 0.51 269 240 p > 10 s). 0.28 0.43 0.22 0.03 1.23 0.27 299 270 p ). 0.28 0.08 0.06 0.01 0.81 0.15 0.07 0.16 329 300 0.65 0.25 0.28 0.04 0.02 0.04 0.04 359 330 42.26 20.11 27.47 Total 2.52 0.69 0.80 0.00 6.87 100 77 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Figure 7.5 Box 7.2 78 .. D 7.4.3 Example ofassessingthresholdconditions fromwave data Example ofwave roseandfrequencytables(contd) four periods when the threshold is exceeded forperiodslongerthan24hours. four periodswhenthethresholdisexceeded thereare Inthisexample andgreennon-exceedance. red representingexceedance speed, U Downtime analysisinvolvestheassessmentofametoceanparameter(commonlywind conditions withbuildcontractors(seeSection7.6). establish suitableallowancesfornumbersofweatherdayswhenagreeingcontractual suitable constructionperiods.TheanalysisisalsointegraltoO&Mplanningand limiting weatherconditions,toassistinvesselselection(operability)andplanfor Downtime analysisprovidesameanstoevaluatetheaccessibilityofsiteagainst against athresholdconditionofsignificantwaveheight(H ofwaveconditionsconsidered forashortextract Figure 7.5providesanexample determine durationsofslackwater. speedthresholdsarelikelystream sitescurrent tobeanadditionalrequirement aspecifiedoperationalthreshold.For orbelow(non-exceedance) (exceedance) tidal owntime Table 7.6
Wave period, Tp (m) 12 13 11 14 >= 10 1 2 3 4 5 6 7 8 9 10 Total and waveheight,H 12 13 11 14 15 10
2 3 4 5 6 7 8 9 < anal >= < y 21.55 sis 3.59 6.29 5.85 0.38 0.26 0.03 0.02 1.05 0.01 1.61 0.11 0.11 0.11 2.14 029 0 Wave frequencytable(wave direction) periodversus 22.03 0.02 2.06 2.85 0.70 0.05 0.04 0.06 0.02 4.77 0.01 0.19 5.14 6.14 059 030 10.79 s 3.84 0.02 0.34 2.69 0.50 1.88 1.43 0.01 0.07 089 060 ) toestablishwhenconditionsremainabove 3.32 0.25 0.08 1.42 1.05 0.01 119 0.41 0.10 090 0.68 0.54 0.09 1.63 0.21 0.01 120 149 0.10 Wave direction, 5.43 0.02 0.38 2.02 0.95 0.43 1.46 0.01 0.15 150 179 20.26 0.04 0.67 4.30 0.03 1.96 0.01 0.27 5.15 180 209 7.85 θ (°N) 9.95 0.40 0.34 0.04 0.02 1.75 4.21 0.01 3.19 239 210 s ) setat1m,withperiodsin 2.36 0.03 0.22 0.90 0.60 0.50 0.01 0.10 269 240 0.42 0.39 0.02 1.23 0.01 0.01 0.15 0.07 299 270 0.17 0.25 0.04 0.21 0.01 0.01 0.81 0.19 0.10 329 300 0.65 0.02 0.04 0.04 0.03 0.02 0.02 0.01 0.12 0.11 0.10 0.16 359 330 CIRIA C666 18.50 15.95 21.10 27.60 Total 9.80 2.98 0.48 0.04 0.31 0.13 0.15 0.14 0.10 2.71 100 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 7.7 CIRIA C666 Example table of persistence statistics Example table ofpersistence six hoursthisprobabilityincreasesto69.8percentofthe month. hours isassessedas36.4percentofthemonthforallyears. For ashorterdurationof theprobabilitytoremainbelowthresholdforperiodslongerthan72 this example year variationandanall-year summaryvalueforthemonthlyvariationincluded.In Table ofpersistenceanalysisforamonthperiod,withyear-on- 7.7providesanexample value determinedattheintervalofsourcedata. valueisequivalenttothepersistencepercentage Note thatthepercentageexceedance asapercentage. time intervals,commonly6,12,24,48and72hours,expressed athresholdvalueisestablishedforseriesof orbelow(non-exceedance) (exceedance) For persistence analysis,thelikelihood forconsecutiveperiodsoftimetoremainabove events whicharegreaterthanthethresholdvalue. asthepercentageof For isexpressed analysis,thelikelihood ofexceedance exceedance andpersistenceanalysis,forconsistency.exceedance notionally from2m/s.Itisgoodpracticetoadoptthesamethresholdsforboth from 5m/suptothemaximumwindspeedandatasimilarsuitableincrement, and atasuitableincrement,notionallyfrom0.1m.For windspeeds,thisislikely tobe recorded waveheight(toestablishthefullrangeofconditions)forsiteinquestion operational limit.For wavesthisislikely tobeH limits forvariousactivities,withvaluesselectedbothtowardsandatthenotional Threshold valuesneedtobeselectedwithconsiderationofpre-establishedoperational been filledasthismaydistortthestatistics. generalised monthlystatistics.Specialcareneedstobetaken ifgapsinthedatasethave year andmonthseparatelytoassessinter-annualvariationsaswellprovidingthe time seriesspansseveralyearsitmayalsobeinstructivetoprovidethisanalysisforeach when conditionsarelikely tobefavourableforaselectedactivity. Wherealong-term time seriesdataneedstobegroupedintoindividualmonthlyblocksestablishperiods interval ofaboutonehour. To understandvariationsofdowntimethroughtheyear, the datastreamrecordedwitharegular It ismostusefultoobtainanuninterrupted from along-termtimeseriesofeventsrecordedonsitelocatedintheareainterest. Good practiceistodevelopdowntimeanalysisfortherequiredmetoceanparameter(s) Persistence analysis–ameasureoflikelihood forconsecutivedurationsofdiscrete 2 Percentage –todeterminetheproportionofeventsaboveathreshold exceedance 1 Two formsofassessmentcommonlyusedindowntimeanalysisare: ≥ 72hours ≥ 48hours ≥ 24 hours ≥ 12hours ≥ 6hours Durations time intervals, when the threshold is either exceeded ornot. time intervals,whenthethresholdiseitherexceeded foreventsbelow athreshold). (non-exceedance Month events accessibilit y height oftheloweraccessplatformiscriticalforbothsafe access and s ) forboat/ladder 83 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 84 pushed ontotheaccessladder. Typical limitingconditionsforsuchaccessmay be: ofvesselaccesstoafixedFigure 7.6showsatypicalarrangement platformwiththebow personnel transfers. This methodincreasesthemaximumsignificantwaveheight thresholdforsafe between thetwo,largely reducingtheverticalmotionofvessel atthecontactpoint. power aheadwhileincontactwiththeboatlanding,effectively increasingthefriction vessel andboatlandingcontactpointsshouldbedesigned suchthatthevesselisto relation totheprevailingsiteconditionswhenselectinga suitable vesselorvessels.The personnel transferoperationsanditisthesecharacteristicswhichwillbeconsideredin surge andsway. Theheaveandpitchofthevesselareparticularconcernduring itwillpitchandroll,yawheave, A vesselwillmovewithsixdegreesoffreedom– and speedintransitversusheaveresponseduringtransfer. Vessel designforladderaccessisacompromisebetween boatsizeandlandingstrength, occurrences. to beregularlycleanedpreventslippingandcrushinjuriesormanoverboard susceptible toslipperymarinegrowthinthesplashzone,duewaveaction,andneed are the sitewilldefinemostappropriateorientationforladders.Ladders requirement forunplannedaccess. turbines mayneedtoincludemorerobustdesignoptionsattemptlimitthe placed inareaswhereconditionspreventsafeaccessforlongperiods,thenthese areas ofconsistentdepthmaybetreatedinamoregeneralisedfashion.Ifturbinesare should becollectedandanalysedaroundpointsofsignificantchangesindepth,while have aprofoundeffectonsignificantwaveheightatlocalisedlevel.Inparticular, data variation inthebathymetry, sinceshoaling,wavebreakingandnon-lineareffectscan Again, samplinglocationsforwavedataarekey insiteswherethereisahighdegreeof Round 1windfarmsites. methodofaccessfor accessfromsmallvesselshassofarbeenthepreferred Ladder renewable industry, inuseandarenotconsideredhere. buttheyarenotcurrently dynamically positionedvessels.Intime,suchsolutionsmaybedeployedintheoffshore industry, includingconceptssuchasheavecompensatedgangwaysdeployedfrom inusetheoffshoreoilandgas A numberofinnovativeaccesssolutionsarecurrently maintenance requirementsunderdifferentconditions. installations willuseacombinationofaccessmethodstosuitdifferenttypes it isacceptableinUKwaters.Itlikely thataccessstrategiestolarger offshore the Irishauthoritieswillnotallowrigidinflatablesforpersonneltransferoffshore,while countries andevenkey individualsholddifferentviewsandrestrictions.For example respect tohealthandsafetyrisks.At presentdifferentgovernmentdepartments, It isnotyetclearwhichaccesssystemswillprovethebestormostacceptablewith Personnel accesstostructures Access systems surface currents (dependingonboatlandingorientation) surface currents wind speeds(at10m)lessthan 20to25knots significant waveheightlessthan 2to2.5m(dependingonvesselandplatform) In situ analysis ofprevailingconditionsatdifferentparts CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 7.6 fixed platform (courtesy WindCatWorkboatsfixed platform(courtesy Ltd) Illustration ofthechallengevessel accesstoa be transferred directlytotheturbinestructuresviagangways. be transferred vessels tobejacked upadjacenttotheturbinestructures, inwhichcasepersonnelcan specialist vessels,whicharediscussed inSection8.2.Theseoperationsmayrequire Large campaignbasedmaintenanceprojectsinvolvingheavyliftswill requiretheuseof Options forsuchbasescouldinclude: metocean conditionsandofferameanstoavoidtransitfromdistantshorestation. some ofthelarger morelimiting andmoreremoteRound2projectswhichexperience wind farmprojects.However, theymayofferanefficientandcosteffectivesolutionto Offshore maintenancebaseshavenotbeenjustifiedforthesmallnearshoreRound1 Other accessmethods they impactontheplannedmaintenanceprogrammeforsite. weather downtime.Thesereducedoperatingwindowsbecomeofparticularconcernif considerable operating windowsforsitesfurtheroffshoreandarelikely toexperience forced toquicklyleavethesiteandseekshelter. Sotheywillhavesmallweather weather theoperatingspeeddropssignificantly. Indeterioratingweathertheymay be a comfortabletravelenvironmentfortechniciansinmoderateandbadweather; conditions whereladderaccesstostructuresispossible.Ingeneral,theydonotprovide These smallvesselsareparticularlyweathersensitiveandultimatelyuseislimitedto wave conditions. enhanced bycarefulselectionofthevesselhulldesignwithrespecttodominant shore base.Passenger comfortandsafetyduringbothtransittransferwillbe is dictatedtoadegreebythewaveclimateatsiteandfortransitroutefrom inuse.Thechoice ofbotharecurrently mono-hull orcatamarandesigns,andexamples Presently thereremaindifferingviewsastowhethervesselaccessisbestachievedwith as anintegralpartoftheproject. a dedicatedoffshoreaccommodationandmaintenancebase designedandinstalled a mooredbarge withaccommodationandenduranceasabove and endurancesimilartothemothervessel a jack-upbarge operatingon-siteintheselfelevatedmodewith accommodation for apredeterminedmaintenancecampaignofmultipleworking shifts conditions withlivingaccommodationformaintenanceteamstoremainoffshore a mothervesselcapableofremainingonstationinallbutthemostextreme 85 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 86 Weather Panel Weather-sensitive offshore operations andmetoceandata forecastsmaybefoundin andexample detail inthisdocument,butintroductorytext aviation activitiesarewellestablished.Therequirementswillnotbedealtwithingreat and standardsformetoceandataobservationforecastingspecifictotheseother Helicopter transportofpersonnelisanessentialpartoffshoreoilandgasoperations, helicopter anditscrew. on thetower. Accessconditionswillbedefinedaccordingtothecapabilitiesof are iceboundforperiodsorinanemergency wherepersonnelarestrandedorinjured technician andhelicoptercrew. Thismethodofaccessistypicallyonlyusedonsitesthat be loweredontothehub:aprocedurewhichrequiresspecialisttrainingforboth option.Personnel willneedto Site accessviahelicopterisconsideredaveryexpensive conditions forawavefarmsubseainspectionandmaintenance vesselmaybe: dynamic positioning,anchoringormanualpropulsioncontrol. Typical limiting observation classROV. Operatinglimitswilldepend onwhetherthevesselisusing out usingamulti-purposevesselorbarge capableofholdingstationwhiledeployingan cableswillbecarried Inspection andmaintenanceofmoorings,umbilicalsexport and towingequipment.Typical limitingconditionsforawavefarmtowvesselmaybe: deploying anobservationclassROV andbeequippedwithdedicatedanchorhandling multi-purpose supportvessel(about30to50m).Thesevesselswouldbecapableof outbyasmall The disconnectionandtowingoperationwouldtypicallybecarried for servicemaintenancearethosedefinedbytheoperatinglimitsofvesselsused. transported toanonshorefacilityformaintenance,sothelimitingmetoceanconditions It isanticipatedthatmostwaveenergy deviceswillberemovedfromsiteandtowedor develop strategiesfor: Site accessibilitytowaveenergy sitesrequiresassessmentofmetoceanconditionsto approaching suchdevices(Figure 7.7). bridge ofaservicevesselmaybecomeseverelylimitedand provideanaddedriskto relatively lowprofileinthewatercolumn.Inraisedseas lineofsightfromthe Note thatWECtechnologiesaretypicallysurfacefloating devices whichhavea Helicopter access Wave farms wind speeds(at10m)lessthan20knots. significant waveheightlessthan2m(dependingonvessel) infrastructure. site accessforinspection,andmaintenanceofmooringsthesubseaelectrical maintenance ofthewaveenergy converter wind speeds(at10m)lessthan25knots. significant waveheightlessthan2.5m(dependingonvessel) Handbook ofoffshore forecasting services (HSE, 2001)andintheOffshore (WMO, 1997). CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 7.7 raised seaconditions vesselsRestricted in lineofsightforsmallservice conditions foratidaldevicesubseainspectionandmaintenance vesselarelikely to be: dynamic positioning,anchoringormanualpropulsioncontrol. Typical limiting observation classROV. Operatinglimitswilldepend onwhetherthevesselisusing out usingamulti-purposevesselorbarge capableofholdingstationwhiledeployingan cableswillbecarried Inspection andmaintenanceofmoorings,umbilicalsexport for theworkinadditiontowindandwaveinfluencespreviouslydiscussed. type isused,tidalstreamconditionswillsignificantlyinfluencetheoperatingwindows from ajack-upbarge oravesselholdingpositionwithanchorsDP. Whichevervessel In thesecondscenario,removalofdevicemayinvolvecraneoperationseither water. located intidalraces,maylimitsafepersonnelaccesstoshortperiodsaroundslack complication ofstrongtidalconditions.Theconditions,particularlyfordevices similar tothosewithaccessawindturbinestructure,theadditional maintenance platformsonthestructure.For boatlandingaccess,theconstraintswillbe In thefirstscenario,metoceanlimitswillbedeterminedforsafepersonnelaccessto generally designedformaintenanceby: governed bythestrongtidalconditionsaswellwaveprofile.Tidaldevicesare Site accesstotidalenergy willbe sites,bythenatureofresourcebeingexploited, Tidal streamsites surface current lessthan1.5knots. surface current wind speeds(at10m)lessthan25knots significant waveheightlessthan2.5m(dependingonvessel) maintenance. removing thedevicefromdeploymentstructureormooringforremote raising thedeviceabovesealevelforsurfaceaccess 87 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Figure 7.8 88 . PLANN 7.6 Vessel operationsplanningprocess involved, pilinganddrillingequipmenthavesuitablecranesinstalled. thesignificantpayloads for turbineinstallationthathaveboththeabilitytocarry time ofwritingthereareveryfewpurposebuiltorconvertedspecialistjack-upvessels established andtheyareprocuredasearlypossibletoavoidscheduledelays.At the anticipated, particularlyinconstructionofoffshorewindfarms,vesselavailabilityis vessel availability(Figure7.8).Itisadvisablethatwheretheuseofspecialistvessels required canbeidentified.Thisisaniterativeprocess,whichwilldependnotleaston construction activityplannedforeachwindow, thenthenumberandtypeofvessels specifications. Dependingontheamountofdowntimeanticipatedand weather days).Thesesafelimitswillbedefinedbytheconstructionactivityandvessel downtime waitingonweatherthatislikelytoas tobeencountered(commonlyreferred developer astothethresholdlimitsforsafeworkingandthresholdsamountof April toOctoberinUKwaters).Agreementshouldbereachedbetweencontractorand into accountthelikely metoceanconditionsduringtheconstructionwindow(typically outconstructionplanning.PlanningshouldtakeThe principalcontractorwillcarry judgement, marginal. used toapplypressureonvessel masterstoworkinconditionsthatare,their 2001/022 onoffshoreoperations specificallymentionsthatmetoceandatashouldnotbe for thesafetyofvesselandcrewhasfinaldecision onalloperations.HSEOTR Further, itshouldalwaysbenotedthatthecaptainofavesselisultimatelyresponsible disagreement duringtheconstructionperiodindowntime claims. forecast withrelationtoplannedactivitiesareagreed.This willavoidthepotentialfor method ofmeasurement,timeandinthe caseofforecastdata,time direction, theheightofmeasurementisstated)andequally importantly, thatthe definitions ofwaveheightandsignificantheight,or for windstrengthand contractual purposes,thatthedefinitionsofeachparameter areagreed(forexample, It isparticularlyimportantwhendefiningthedowntimeand thresholdlimitsfor and operatinglimits safe working limits. HSE requirements. vessel availability metocean data Contractor Developer I NG ANDPROCUREMENT Review ofvessel selection Downtime analysis Probable numberofworking days inconstructionwindow Agreed workingAgreed thresholds CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 . PRE-CONSTRUCT 7.7 considered toassistinplanninganyfurthersurveys. engineering designandO&Mplanning.Thisdataknowledgeshouldbe andwithdetailedanalysisdevelopedtosupportboth is likely tobefairlyextensive as describedinSection6.3.At thisstageintheprojectlifecyclemetoceandatabase In termsofmetoceanissues,vesselselectionremainsaprimaryissueforconsideration, activities. evidence ofthebaselineenvironmentalconditionsaheadanymarinedevelopment The purposeofmonitoringatthepre-constructionphaseistoprovideadditional programme tobedevelopedandagreedwiththelicensingauthority. construction phases(Section9.4).Itisgoodpracticefortheoverallmonitoring toconstruction(Section8.4)andpost- monitoring programmewhichwillextend Pre-construction monitoringshouldalsobeseentopartoftheoverallenvironmental be ignored. gaps tosupportdetaileddesign,althoughopportunitiescombinethetwoshouldnot issues aretaken asdistinctfromanydetailedsiteinvestigationworkrequiredtofilldata placed asaconditionofthelicence.For thepurposeofpresentguidelinesthese by theES.Suchrequirementsnormallyarisefromconsentingofprojectandare respond toanyremaininguncertaintiesinpresumedenvironmentaleffectsasdescribed environmental surveysthathavebeenagreedbetweenthedeveloperandregulatorto Pre-construction monitoringactivitiesaredefinedhereasthesetoffurther I ON MON I TOR I NG 89 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 90 8 8 . 1 site. between onetothreeyears,dependingonthescaleofprojectandaccessibility As anestimate,thetimescalerequiredtoundertake constructionactivitiesmaybe wave projects. On-site monitoringislikely tocontinue,especiallyinrelationoffshorewindand development include(Figure8.1): construction phase.Activitiesthatwillbeadvancedduringthisstageofproject From completingallpre-constructionrequirements aprojectwillmoveintoits OVERV C onstruction construction monitoring. forecasting construction I EW issues CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 8.1 Construction activitiesandlinkages 91 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 92 8 2CONSTRUCT .2 Construction activitieswillinvolvesomeorallofthefollowing: Commissioning. 5 Cablelaying. 4 Sub-station installation. 3 Tower andturbineinstallation, includingblades. 2 Foundation installation. 1 five mainconstructionphases: For metoceanconsiderationsforawindfarminstallationshouldsupportthe example, well assomemarked differencesrequiringspecificmetoceaninformation. solutions tocompletetheconstructionphase.Therewillbecommonactivitiesall,as renewable energy development(wind,wavesandtide)willrequirebespoke engineering metocean dataneedstobeeffectivelycommunicatedallsub-contractors.Eachtypeof The projectdeveloperhasresponsibilityforallactivitiescontractedunderthem,so windows assessedaspartofdowntimeanalysis(Section7.4.3). construction windowandwithspecialreferencetotheprobabilityoffavourableweather dataset. Thisinformationwillallowthedeveloperorprincipalcontractortodefine confidence totheaccuracyofpredictingconditionsatsiteforagivenforecast additional confidenceintheaccuracyorvalidityofhistoricaldatasets.Thiswillalsoadd in prevailingconditionsandsitespecificdatacollectedwillenabledeveloperstohave At thispointintheproject,therewillbeagoodunderstandingofseasonalvariation adverse conditionscanleadtocostescalationatacriticaltimeintheprojectlifecycle. Metocean conditionscanhaveasignificantinfluenceonconstructionactivitiesand significant waveheightof2.5 to3.0m. defined bythesafeworkinglimits ofpersonnelontheanchorhandlingdecks,with moorings whileonstationusingmainenginepower. Theworkinglimitsofthetugsare positioning (DP)capabilityandhighloadpullare requiredtopretensionthe maximum significantwaveheightof2to2.5m.Anchorhandling withdynamic the site,connectionandcommissioning.Theseoperations aretypicallyrestrictedtoa construction areconfinedtoinstallationofmooringsand umbilicals, towageofdeviceto Wave deviceconstructionwillbecompletedonshore,sooffshoreconsiderationsforthe personnel transfers cable laying,includingburialandscourprotection diving operations,includingROV crane operations placement ofscourprotection drilling, pilingorseabedlevellingoperationsforfoundations positioning ofconstructionvesselson-site transport ortowtothesite loading ofpartsandequipmentontovessels commissioning andtesting. I ON CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Figure 8.2 Wave Ltd) OceanPower energydevice Delivery undertow (courtesy tows. execution ofmarineoperations investigated fortheirsuitabilitytothespecificproject.The Specialist oceantowforecastproductsarebecomingavailableandshouldbe might be: procedure forgettingadevicefromanonshoreconstructionfacilitytotheoffshoresite of shelteredhavensatthedepartureanddestinationpointsfortow. Atypical weather windowsforcompletingthetow. Apre-requisiteforthetowisavailability The limitingenvironmentalconditionsforthetowroutewilldictateavailabilityof case, thenthereislittlepoint inriskingvesselandequipmentleavingport.Another conditionson-sitewillbefavourableforthestartofinstallation. Ifthisisnotthe arrival, Medium andlong-rangeforecasts willalsoneedtobestudiedensurethat,upon forecasts, includingwindand seastateandvisibilityforthedurationofpassage. and visibility. Timingof all transportationoperationswillbedecidedbyweather All oftheseactivitieswillbeaffectedbythewind,tidalheight, waterflowrates,seastate will berequired. able toholdstationforconstructionactivitiesintheseconditions andanchoredvessels many activitiesmaynotbepossibleduringtimesofpeakflow. DPvesselsmaynotbe largely thoseofwindandwave deviceswiththesignificantcomplicationthat mirror Metocean considerationsforoffshoreconstructionofcommercial scaletidaldeviceswill connect andcommissionthedevice. connection (Figure8.2) tow devicetooffshoresitewhenmetoceanconditionsarewithinlimitsfor conduct toweitherdirectlytotheoffshoresiteorlocalportfacility height, tidalstrength,waveheightandperiod,windstrengthdirection) await weatherwindowwithinlimitingenvironmentalconditionsforthetow(tide environmental limitsforthetow, andthetowroute) survey(detailingmaximum pre tow-outcommissioningworkandtowwarranty major componentassemblyeitheronshoreorafloatinshelteredharbour DNV (1996)isusefulforsingleeventoperationssuchas Rules forplanningand 93 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 94 at theequivalentliftingheight. Nowcast datafromthemetmastshouldbeusedtoassistinevaluatingwindconditions maximum craneoperatingheightsisanimportantinfluenceontheinstallationtiming. addition tothemetoceanfactorsaffectingfoundationinstallation,windspeedat vessels, withthedeckraisedtoprovideastableplatformforcraneoperations.In length. Tower, outusingjack-up nacelleandbladeinstallations(Figure8.3)arecarried of80min challenges thatneedtobemanagedastowersarenowgenerallyinexcess engineering oftheextreme Wind farmtowerandturbineinstallationisanexample the safetyoftheirvesselandcrew. forecast conditions,rememberingthatvesselcaptainshaveultimateresponsibilityfor agreement isreachedonprecisedefinitionsofmeasurementforbothrealtimeand written intoconstructioncontractsandvesselcharterparties.Itisimportantthat hazard riskassessmentswillbecompletedforeachoperation.Theselimits on safety. Thevesselownersandoperatorswilldefinesafeworkinglimits and weatherpre-determined.Metoceanconsiderationswillhaveanimportantbearing Each constructionactivityanditsassociatedequipmentwillhavesafelimitsofseastate projects mayneedupto30kmofcablebelaidinasingleoperation. cables installation,whichisusuallycompletedinonepiece.Round2offshorewind (sitetoshore) that haveverystrictminimumcompletiondurations,suchasexport maybecritical tocertainoperations.For constructiontasks not beexceeded example, Understanding thetimeavailableinwhichsuchamatrixofthresholdconditionswill around thetidalflows,potentiallysavingmanyhoursofwaitingtimeforvessels. swells. Thisknowledgecanbeusedwithsite-specificforecaststoplanoperations working conditionswhencombinedwithstrongcounterdirectionaltidesorlarge will bedetermined.For certainwinddirectionsmaybeknowntocauseunsafe example, understand andpredictthemetoceanconditionson-site,bettersitesafetycontrols importance. Themoreconfidencethattheconstructionteamhaveinabilityto route-to-site conditions,andtheirinfluenceonthedecisionmakingprocessisofhigh substantially. Asaresult,understandingtheaccuracyofforecastsforon-siteand vessels on-siteandoperatingcouldpotentiallyincreasetheoverallprojectcosts project stagearesuchthatpoorlyinformeddecisionmakingwithregardtohaving conditions deteriorate.Inaddition,downtimecostsofspecialistvesselsusedatthis during theconstructionperiodandensurepersonnelequipmentaresafewhen Construction planningshouldtake intoaccountthelikely conditionsthatwillprevail confidence intheforecastaccuracy. fortheirpotentialinmaximisingtheuseofweatherwindows,byincreasing explored Finally,demurrage. developmentsrequiringspecificheavy liftforecastsshouldbe unwanted costthataccuratemetoceandatamanagementcanassistinavoidingis CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Table 8.1 Figure 8.3 favourable conditions (courtesy CentricaRenewablefavourable conditions(courtesy EnergyLimited) operationsduringhighwinds,(right) aborted Installation ofturbineblades(left) Note: Typical maximumoperatingconditionsforajack-upbarge Typical maximumoperatingconditions forajack-upvesselareshowninTable 8.2. Typical maximumoperatingconditionsforajack-upbarge areshowninTable 8.1. specialist jack-upvesselswhichareself-propelled. Foundation andtransitionpiecesarenormallyinstalledusingjack-upbarges or ofwaveandwindoperatinglimitsforfoundationinstallationarepresented. examples Vessel selectionisacriticalcomponentofconstructionplanning.To illustratethissome operations Jacking Under tow Crane operations (non-operational) Jacked survival Operation Figures basedon7.5mairgap Wave height H 10.0 3.7 1.5 1.5 s (m) Wave period T p 6 9 – – (s) Wind speedat10m Limited) Centrica Renewable Energy jack-up vessel (right)(courtesy Typical and jack-upbarge(left) Figure 8.4 (knots) 25 70 20 20 Surface current Dependant on vessel power (knots) 2.5 1.5 – 95 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Table 8.2 96 Typical maximumoperatingconditionsforajack-upvessel co-ordinate with,theMaritime andCoastguardAgencyresponsibleforimplementing 1974andamendments, andtotake noteof, and Safety ofLifeatSea(SOLAS) All offshoreoperationswillneed tocomplywiththeInternationalConventionfor relation tovesselperformance andpersonnelaccess. particular useinfurtherdefiningthresholdlimitsforO&M activities,especiallyin andwillbeof construction phase.Thisdatawilladdtothesite-specificexperience Wherever possible,metoceandatagatheringshouldcontinue throughoutthe with aframeworkofcomprehensivesitemetoceandatafor thesedecisionprocesses. developer canaddmuchtotheprojectconstructionphase byprovidingcontractors personnelandwell-definedprocedures. The taskandrequiresexperienced complex Construction co-ordination,particularlyofwindandtidal projects,isanextremely unsafe levelsduetofoginagivenperiod. electrical activity(lightningstrikes) ornumberofdayswhenvisibilityisreducedto location. Itisimportantthatallweatherfactorsareconsidered,includinglikelihood of UK waters).Notetheremayberefinementswithinthiswindowaccordingtothesite activities aspossibleduringthesummermonths(usuallybetweenAprilandOctoberin The mostobviousmitigationofmetoceanriskistoscheduleasmanyconstruction Risk mitigationmeasuresinclude: also industry For thepurposesofthisdocument assessments (Section4.3). in place,andproceduresshouldbeestablishedbasedonsuitablesufficientrisk Health andSafetyatWork Regulations1999.Emergency shouldalsobe arrangements safety, anditisalegalrequirementforeveryemployerundertheManagementof safety guidelines.Riskassessmentisakey activityinthemanagementofhealthand manner, sotheover-archingrequirementsformetoceandataaredrivenbyhealthand Construction activitiesshouldbecompletedinasafeandenvironmentallysensitive Jacking operations Crane operations (non-operational) Jacked survival accurate forecastingtodirectactivitiesappropriatetheconditions. construction vesselsandequipment capabilities, andtomaximisetheefficiencyofusingspecialistexpensive appropriate activitiestotake placeaccordingtotheconditionsandvessel toallowfor construction planningmethodologythatbuildsinflexibility minimised maximising useofonshoreconstructionsothatoffshoreactivityis scheduling ofcriticalconstructioninthesummermonths Weather-sensitive offshore operationsandmetoceandata Operation (BWEA, 2005)provideinformationthatiscommon totheotherresourcetypes, Wave height H 10.0 3.0 s – (m) Guidelines forhealthandsafetyinthewindenergy Wave period T p – 9 – (HSE, 2001). (s) Wind speedat10m (knots) 30 70 30 CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 8 3MAR .3 follows theschematicpresented inFigure8.5. topography orsmall-scaleweather effects.Asaresulttheidealisedforecastprocess particularly importantwhenandwherethemodeldoesnot sufficientlyresolvecomplex the-minute observationsandadjustingtheforecastasnecessary. Thisrolecanbe human forecasterretainsakey toup-to- roleinassessingmodelperformance,referring For alltherecentadvancesincomputingpowerandNWPmodel sophistication,the To propagatethemodelforwardintimetoproduceforecast. 2 To combineavailableobservationswithabackgroundofhighdensitymodeldatain 1 locations. TheNWPprocesscanbethoughtofashavingtwostages: description ofenvironmentalvariablesoverahighdensityglobalorregionalgrid forward intime(themodelforecast).NWPmodelsaimtoprovideanaccurate Forecasts buildonthecapabilitytorunnumericalweatherprediction(NWP)models will becomeessentialwhenmakingdecisionsforalloffshoreactivities. During construction,post-constructionanddecommissioningphasesmarineforecasts handed over, followedbyasnaggingphase. onto theowners.Therewillbeatestphasebeforerenewabledevelopmentis On completionofconstruction,CDMRegulations2007dictateasafetyfileispassed untenable forthevessel(s)toremainon-site. todeterioratethepointwhereitbecomes change sothatconditionsareexpected Plans shouldalsobemadeforevacuationandreturntosafewaters,forecasts ensure thatthiseventualitydoesnotoccur. information managementsysteminconjunctionwiththesafeofworkshould the safetyofhumanlifeand/orvesselisthreatened.Arobustmetocean of avesseldeterminesthatitisnecessarytodepositthesubstancesorarticlesbecause majeure scenarios includeabandonmentofallconstructionactivitiesinthecasea specific eventsandcompliancewiththeCDMRegulations2007.Operationalworst-case risk. limitsforactivitieswheremanoverboardisapotential will influencethesiteexposure outthat threshold conditionsunderwhichsearchandrescueoperationscanbecarried possible, shouldweatherconditionsdeteriorate.Thiswillincludedefinitionofthe Operations needtobedesignedsotheycanterminatedormadereversiblewherever are likely tobeyachtsandotherpleasurecrafttryinggetacloserlook. from theboundary. outinsummermonths,there Astheconstructionworksarecarried protect againstpersonsfallingintothewater, andtowarnawayapproachingvessels construction activity, tonotifyotherseatraffic.Asafetyboatwillbeonstandby codes giveinternationalguidance.NoticestoMarinerswillbeissuedadvisingof Islands) ortheNorthernLighthouseBoard(ScotlandandIsleofMan),whileIALA configuration willbeagreedwithTrinity House(England,Wales andtheChannel established aroundworkswithboundariesdesignatedbynavigationalmarkswhose zoneswillbe maritime safetypolicyinUKcoastalwaters.Ingeneral,exclusion whole modelgrid(theanalysis),aprocessknownasdataassimilation. order toachieveabestrepresentationofnearpastorpresent conditionsoverthe Rules forplanningandexecutionofmarineoperations . Thismayapplywhen,duetostressofweatheroranyothercause,themaster I NE FORECASTS (DNV, 1996)willassistfor force 97 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED Figure 8.5 98 Schematic of the weather forecast process (courtesy MetOffice) Schematic oftheweather forecastprocess(courtesy oe Realtimeobservationssourcedworldwide arecombinedwithmodelfieldsthroughtheprocess Note: Oceanmodelsuseeithertwodimensiondepthaveragedorfullthree dimension 3 Wave modelsaredrivenbyforcingfromanatmosphericmodelandprovidesea 2 Atmospheric modelssimulatewinds,weatherandclouddetails(whichcanbeused 1 model typesprovidethebasicparametersformetoceanforecasting: The sourcemodelsfromwhichforecastdataareacquiredwilldiffer. Threesource shallow waterapplications. dimension models,butarenonetheless consideredadequateforanumberof representedinthree temperature andsalinityover depth)thatareexplicitly make considerationoftheverticaldensityeffects(due tovariationofseawater such astemperatureandsalinity. Two dimensiondepthaveragedmodelsdonot (flows),plusotherphysicalpropertiesofseawater sea surfaceelevationandcurrent schemes, and,basedontidalharmonicsandatmospheric model forcing,simulate wind-sea growth. calculationusedbythemodel todescribe depending ontheamountofexplicit common operationalusageandaredescribedassecondor thirdgeneration details basedonevolutionofthewavespectrum.Two modelschemesarein state characteristics,includingsignificantwaveheight,period, directionandswell the primitiveequations)toproducepredictionsoffutureatmosphericconditions. running themodelforwardintimeusingmathematicalequations(oftenknownas stateoftheatmosphereintoapreviousmodelforecast,andthen the current to deduceotherparameters,suchaslightningrisk).Incorporatingobservationsof and forecastsovertheshorttomedium-range system, providingqualityassuranceandwherenecessaryinterventiontoimprovebothanalysis to users,butinmajormeteorologicalagenciestheforecasterremainsacriticalpartof conditions forwardintimetoproducethemodelforecast.Modeldatamaybereleasedstraight of dataassimilationinordertoproduceananalysis.NWPmodelspropagatetheanalysis Forecaster intervention Data assimilation Numerical model NWP forecast Observations Forecaster Analysis Users Model data NWP process CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 Table 8.3 Example providers of forecast services to the UK sector of the North Seaoilandgasindustry totheUKsectorofNorth Example offorecastservices providers support (egbyaforecaster)mightberequired. being conducted,theconsequenceofapoorforecastissued,andhowmuch service itisimportanttoconsidertherequirementandimportanceofoperation of qualityassurance,whichisoftendirectlylinked tocost.Whencommissioninga developed forecastproducttypesbeingavailable.Eachwillhaveitsownlevel service theoffshoreoilandgasindustry(Table 8.3),leadingtoarangeofhighly A numberofproviders(bothNationalMetServicesandcommercialcompanies)already The OffshoreWeather Panel forecasts shouldbethat: proposesthebasicrequirementsforaproviderofmarine/coastal WMO/TD-850 forecasting. intooceanographic that itsvalidityforatmosphericforecastingdoesnotyetextend forecasting agencies.ApplicationofWMOstandardsdoeshavealimitationhowever, in up-to-date disseminationmethods)actstronglytodistinguishbetweengoodandbad of observations,runningNWPmodelsinanoperationallyrobustfashion,and addition themodernspecificsofprofessionalweather/oceanforecasting(iecompilation of forecastprovidersapplyWMOstandardsasthebasisforqualitycontrol,andin control systempresentedbyaserviceprovidertopotentialforecastusers.Themajority 1997) offersanumberofguidanceprinciplesthatshouldbeappliedtothequality WNI Weathernews (UK) Nowcasting International)(partners Wilkens Weather Technologies Met Office MeteoGroup UK Aerospace &MarineInternational (UK) adynamic feedbacksystemconnectedtothecustomers d asystemfor informationdistributionandwarnings c numericalprognosticandhind-castmodels b collectedobservationaldata a arrangements forswiftfollow-upofuserrequirements arrangements the contactwithenduser shouldbeinteractiveanddynamic,with emergency responseshouldbewithin 30minutesanytimeofdayornight foremergencyyear round,andarrangements situations.Recommended avoid misinterpretations.Includedshouldbearequirement for24hourservicesall systems ofwarningsandbulletinsshouldfollowWMOstandard requirements,to recommendations andbedocumented shall bedocumentedinopenliterature.Expertiseofstaff shall followWMO stratification, seaiceandtransportofsubstancesobjects. Allnumericalmodels numerical modeltoolsembraceatmosphere,waves,sealevel, oceancirculationand dedicated networks.Networksandsensorsshouldbeadequately documented both fromtheWMOconductedglobalnetwork,aswell fromnationalandlocally observational datashouldflowcontinuouslyintotheservice ona24hourlybasis, the serviceshallbebasedonacoherentproductionline,connecting: Company name Handbook ofoffshore forecasting services issues 103 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 104 Figure 9.1 Construction activitiesandlinkages CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 9 2OPERAT .2 In comparisonKentishFlatsworks,withalowerthreshold ofH 143weather dayswhenthethresholdcriteriawasexceeded. during 2005thisincurred industry For thepurposesofthisdocument assessments. in place,andproceduresshouldbeestablishedbasedonsuitablesufficientrisk Health andSafetyatWork Regulations1999.Emergency shouldalsobe arrangements safety anditisalegalrequirementforeveryemployerundertheManagementof safety guidelines.Riskassessmentisakey activityinthemanagementofhealthand manner, sotheover-archingrequirementsformetoceandataaredrivenbyhealthand the site.O&Mactivitiesshouldbecompletedinasafeandenvironmentallysensitive data availabletoincreaseconfidenceinbeingableaccuratelypredictconditionsat During thepost-constructionphasethereshouldbeasignificantamountofmetocean assist inprovidingcontinuousdatatosupportO&M. placed on-siteforpreviousphasesofaprojectshouldbeleftinplaceandmaintainedto cycles whencomparedtoestablishedtechnology. Wherepossible,measuringdevices relatively younginitsdevelopmentwhichleadstohigherthannormalmaintenance construction activities(Section7.5).At presentallmarinerenewabletechnologyremains The O&Mphaseoftheprojectfeedsfromstrategydevelopedaspartpre- of thesitetowaves. Scroby Sands(albeitinthepreviousyears)isaclearindication ofthegreaterexposure at only 31weatherdaysduring2006.Thegreaternumberof weatherdaysincurred For ScrobySandsa2msignificantwaveheight(H maintenance crews,willdictatethelevelofaccesspossible. ofthe vesseland versus thethresholdlimitsset,togetherwithexperience the day. However, theactualmeasurementofseaconditionsand windstrengthon-site nowcasts willbeusedforschedulerefinementaccordingto thelikely conditionsmet on state, windspeedanddirection,tidalrangevisibility. Short-rangeforecastsand ahead) canbeusedtoconfidentiallyconfirmthestartdate,takingintoaccountsea Forecastsvessel andpersonnelarrangements. atashorterrange(uptosevendays range forecastproductsmayallowadegreeofschedulingforspecificactivities,and work andprovideanestimateofriskduetounfavourableweatherconditions.Long- Downtime analysiswillhelptoidentifythemostappropriatetimesinwhichplanthis when morestableconditionsprevail. will needtobeplannedandthisnaturallytimetabledforthesummermonths seasonal conditions.For apaintingprogrammeforwindfarminstallation example, involve equipmentorderingorspecificleadtimesthatallowforselectionoffavourable Strategic maintenanceincludesallformsofthatcanbeanticipated,or Immediatemaintenance (reactive). 2 Strategicmaintenance (anticipated). 1 Maintenance planningcansplitintotwoareas: 2001) provideinformationwhichisapplicabletoallresourcetypes. (BWEA, 2005)andW I ON ANDMA eather-sensitive offshore operationsandmetoceandata I NTENANCE Guidelines forhealthandsafetyinthewindenergy s ) limitissetfortransfers,and s = 1.5m,incurred (HSE, 105 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 106 Immediate maintenanceisreactive.Itwillbenecessitatedfrom: needed. Thisinformationcanbefedintothemaintenanceprogramme. recorded metoceandatacanhelptopredictthedegreeofmaintenancelikely tobe isgained,licenceholdershavefoundthattheanalysisofsite As siteexperience accessibility. Thisislikely tobeaniterativeprocessthroughthelifecycleof project. lead toimprovedmaintenance vesselselectionforthesitewhichwillmaximiseits Accurate modellingandrecording ofsite-specificmetoceanconditionswillcertainly safely andefficiently. atthesiteandareabletowork access vesselssothatmaintenancepersonnelarrive Consideration shouldalsobegiventoensuringthatsufficient comfortisprovidedin should betaken intoaccountatanearlystagewhenresourceplanningforthesite. discomfortwiththe environment. This environment duetoseasicknessorextreme intheirfieldsonshore,areunabletooperateeffectively themarine expert Experience hasshownthatsomeoperationsandmaintenance personnel,whoare and vesselowner/operators. is likelybetween theinstallationoperators tobereferencedincontractualarrangements consideration. Datareceivedfromrealtimeon-sitemonitoringofmetoceanconditions period, tidalconditionsandtheircombinedlocaleffects,shouldbetaken into Factors thataffectwavesteepnessandboathandling,suchaswindstrength, wave recommended inconditionswithsignificantwaveheightsofgreaterthan2to2.5m. the developmentisgained.Ingeneral,accesstomarinerenewableplatformsnot ofoperatingandmaintaining vessel specificandarelikely tobeadjustedasexperience conditionswillbebothsite-specificand Definition ofappropriatemaximumexposure some leveloftrainingisprovidedtothesestaffbyametoceanspecialist. interpretthemetoceaninformationavailablemaydictatethat appreciate andcorrectly is verysensitivetotheseastates.Theneedforkey operationaldecisionmakers to particularly importantforinstallationsfurtheroffshorewhereaccesstotheequipment also inunderstandingthenowcastdatatermsofitsinfluenceonsiteactivities.Thisis of confidenceinthemodelsusedtomake siteforecastsatthisstageintheprojectand development tobothgatherandanalysesitespecificdatasothatthereisahighdegree decision making.Itisimportantthatopportunitiesaretaken throughouttheproject data ona24-hourbasisandthisinformationwillplaylarge partintheday-to-day It isgoodpracticeforoperationsmanagerstobesuppliedwithnowcastandforecast and emergency rescueandrecoveryvessels(ERRVs). supplyboats,divingsupportvessels mono-hulls andcatamaransdrawingfromexisting conditions. Thetypesofvesselslikely tobeusedforO&Mareanticipatedsmall that theyareabletodirectactivitiesappropriatethevesselsabilitiesgiven Site operationsmanagerswillneedtoknowthethresholdlimitsofallvesselsonsiteso equipment failure activities. deterioration offorecastconditionsforthesite,requiringreviewplanned planned activities deterioration ofweatherconditionsonthesite,requiringimmediatereview personnel emergency withinthevicinityofsiterequiringassistancevesselsand site emergency CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 9 3PERFORMANCEVAL .3 by bladepassingshadowand localturbulenceeffects.Thedatafromthemetmast provide validationofthepower curve,notingthatturbineanemometersareinfluenced least onemetmasttobeplaced immediatelyadjacent(within100m)ofaturbineto continuously gatheredthroughout thelifecycleofproject.Itisgoodpracticeforat An offshorewindsitewillstillmaintainseveralmetmasts from whichdatawillbe anemometers). status (includingwindspeedanddirectiontaken fromtheturbine’s (supervisory controlanddataacquisition),monitoringevery aspectoftheequipment’s through fibreopticdatacommunications,transmittingreal timeSCADAfeeds and shutdownfacility. In thecaseofwindturbinegeneratorsthiswillbeprovided Offshore generatingequipmentwillalwaysneedtoincorporate aremotemonitoring An idealprojectatthisstageofthelifecyclewillhavebenefitof: completed withinagreedsafesystemsofworkandriskassessments. surfaced diverlocationverydifficult.Realtimewavedatawillenableoperationstobe critical, aspoorconditionswillincreaselevelsofrisk.Equally, roughseascanmake information onthiswillberequired.Thewaveheightwhenrecoveringadiveris Diver operationsarealsohighlysensitivetoseastateconditionsandaccurate supporting resourcevalidationandenergy efficiencycalculations(Section9.3). extraction should bepermanentlyinstalledtoverifyconditionsfordivers,withafurthervaluein considered thatrealtimeflowdatathroughoutthewatercolumn(usingADCPdevices) available aroundslackwaterwillbecrucialforplanningsuchmaintenance.Itmight around periodsofslackwaterandpreferablyduringneaptides.Quantifyingthetime more safelyandefficiently. Divingrelatedmaintenancewillneedtobecompleted out willenabletheseoperationstobeplannedandcarried information oncurrents underwater tasks.TECdeviceswillbeplacedinfastflowingwaters,andaccurate flowratesthatdictatetheabilitytocomplete sea level.Divetimesarelimitedbycurrent tidal streamdevices,whenitisnotpossibletoraisethepartsrequiringattentionabove For certaintasksdiversmightberequiredforO&Mactivities,particularlyinthecaseof Diving operations nowcast sitedatawhichcanbeusedto: validated forecastmodelwhichcanbeusedto: improvement. evaluate productionefficiencyallowingidentificationofareasfor maintenance charterparties select operatingwindowsforvesselsworkingon-sitethatcanbewritteninto accurately predictoutputfornationalgridbalancing improve sitesafety direct operationsrealtime accurately predictoutputfornationalgridbalancing. conditions toextreme improve sitesafetybyminimisingexposure optimise maintenancescheduleswithinawindow plan seasonalmaintenancewindows I DAT I ON 107 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 108 9 4POST-CONSTRUCT .4 Guidance forperformancevalidationofwindturbinesisavailablefrom: addition toanymonitoringequipmentbuiltintogeneratingdevices. measurements (fromsitebuoysorothermeasuringdevices)needtobetaken in The sameprinciplesapplyforanywaveortidalscheme.Independentsite influence projectedenergy yieldsfromindividualturbines. anemometer readingsgiveameanstoanalysepossiblewake deficiteffectswhichcould would beconsideredasthedefinitiverecordofenergy turbine yieldatthesite.Local should beconsideredforfurthersurveyplanning. Thisdata andknowledge cycle themetoceandatabaseshouldbefairlyextensive. primary issueforconsideration,describedinSection6.3.At thisstageintheprojectlife As withpre-constructionandconstructionmonitoring,vesselselectionremainsasa continue withfurtherenvironmentalmonitoring. licensing authorityforreview. Thisreviewprocesswillprovidethebasisfordecisionsto collected afterconstruction.Annualmonitoringreportswillrequiresubmissiontothe construction activitiesasthisinitialsetofdatawillformabasiscomparisontoresults It becomesimportantthatthesuiteofmonitoringremainsconsistenttopre- monitoring (Section8.4). through projectdevelopment,frompre-construction(Section7.7)andconstruction by theES.Thismonitoringisacontinuationofactivitiesrequiredatvariousphases respond toanyremaininguncertaintiesinpresumedenvironmentaleffectsasdescribed environmental surveysthathavebeenagreedbetweenthedeveloperandregulatorto Post-construction monitoringactivitiesaredefinedhereasthesetoffurther And similarlyforwaves: For tidalstreamdevicesapreliminaryguidehasrecentlybeenproduced: 2004). Performance assessmentforwaveenergyconversionsystemsinopenseatestfacilities Preliminary tidalcurrent energy:deviceperformanceprotocol Preliminary waveenergydeviceperformanceprotocol Wind turbines (ASME, 1988). (ASME, I ON MON I TOR I NG (DTI, 2007). (DTI, 2007) CIRIA C666 (EMEC, © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 1 1 0. 0D 1 OVERV project, andforlarger developmentsthismayrequireaperiodofuptotwoyears. The timescaleforthedecommissioningphasedependspartlyonscaleof measurement platformsquicklyremoved. On-site monitoringwillalsoceaseastheschemeisdecommissionedwithany Activities thatwillbenecessaryatthisstageofprojectdevelopmentinclude(Figure10.1): development isnolongerrequired,aprocessofdecommissioningwillberequired. itsleaseorthereisapreviouslyagreedpointwhenthe When theschemehasexpired ecommissionin forecasting. decommissioning I EW g issues 109 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 110 Figure 10.1 Decommissioning activitiesandlinkages CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666 1 . DECOMM 0.2 and downtimeanalysis. include issuescommontotheconstructionphasesuchas rig movements,operations rig, whichnecessitatesthere-evaluationofrisksandmetocean datause.Thiswill decommissioning processanduseofspecialistequipment such asadecommissioning bespoke metoceandatarequirementsmightariseduetothenatureof required andcouldbe25to50yearsaftertheconstruction phase.Additionally, Different engineeringsolutionswillprobablybeavailable when decommissioningis O&M phase. monitoring andmaintenanceoftheprojectmetoceandatabasethrough These riskstotheoriginaldatasetsubstantiatepotentialbenefitforongoing estimatesofdowntimedevisedfortheconstructionphasenolongerhold. for example, that, may leadtoagreaterunderstandinginfuturemetoceanconditionstheextent It isalsolikely thatclimate changeandimprovementsinclimatepredictions positions. conditions provideanyremainingrisksufficienttomovestructuresfromtheircharted will needtodrawontheavailablemetoceandataandassessiffutureextreme foreseeable naturalcausessoastocauseahazardnavigation.Suchconsiderations stormsorother seabed andnotmoveundertheinfluenceofwaves,tides,currents, coastal stateshouldbesatisfiedthatanyremainingmaterialswillstayonlocationthe In caseswhereonlypartialremovalofanyinstallationorstructureisconsidered,the Theinstallation weighsmorethan4000tonnesorisstandinginover100mof 5 Entireremoval wouldinvolveunacceptablerisktothemarineenvironment. 4 Entireremoval wouldinvolveunacceptablerisktopersonnel. 3 cost. Entireremoval wouldincurextreme 2 Alternateuseofthestructures. 1 situations whereothersolutionsmaybeconsidered: Alongside thepresumptioninfavouroffullremovalguidanceconsidersfive Present guidanceondecommissioningissuesincludes: scouring aroundresidualstructuresorburiedcablesarenotsignificant. data foroperations.Post-decommissioning surveysmayalsobeneededtoensure construction workswitharequirementforsuitablevesselselectionanduseofforecast Metocean considerationsfordecommissioningaresimilartothosegeneral be removedtoseabedlevelunlessitcanshownenvironmentallyworsedoso. Agreement (OSPAR) 1998andtheEnergy Act2004,whichstatesthatstructuresshould The removalofstructuresinseasaroundEuropeisgovernedbyboththeOslo-Paris water withoutcausingunjustifiableinterferencetootherusesofthesea. guidance notesforindustry Decommissioning ofoffshore renewable energyinstallationsundertheEnergyAct 2004, I SS I ON I NG (DTI, 2006). 111 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED 112 11 information. assist inreducingsomeoftheremainingrisksanduncertainty relatedtometocean greater understandingofissuessuchasclimatechange.Over timetheseadvancesmay introduce newmethods,improvedproductsandservices, aswelldevelopinga It isalsoprudenttocommentthatongoingresearchand development islikely to maintenance ofametoceandatabase. project teamrequirestheuseofagooddatamanagement systemandregular conditions. To ensurethatthisknowledgeisusedandsharedeffectivelythroughouta ofsite through theprojectlifecycleandovertime,aswillknowledgeexperience The amountofdataandunderstandingmetoceanissueswillnaturallyincrease forecasts. requirement forfurtherandothertypesofdata,suchas datasets maynolongerbefit-for-purposeforsubsequenttasks,leadingtoa beyondavailabledata.Initial of metoceanissueswillberequiredwhichextend Importantly, astheprojectmovesthroughitslifecycle,amorerefinedunderstanding when shoalingeffectsbegintodissipatesomeofthedeepwaterwaveenergy. underestimation ofcertainparameters.Waves, maybeoverestimated forexample, data, toinferconditionsatanadjacentshallowwatersite,mayleadbothover-and more immediatelyrelevanttodeepwaterandoffshoreinstallations.Adoptingsuch publicationsprovidecomprehensivedescriptionsofmetoceanconditions Many existing application. developed furthertobecomefit-for-purposefortheareaofinterestandtype study tosupporttheseactivities,asthisinformationwillfrequentlyneedbe engineering relatedactivities.Careneedstobetaken whenselectingsuchdataintoa draw onavailablearchivesofmetoceandatatosupporteconomic,environmentaland Early phasesofprojectdevelopment,throughtopre-constructionactivities,arelikely to data maybetaken intoastudyattheoutset(iefrombroadscalemodels). the generalscarcityoflong-termmarineobservationaldatameansthatothertypes but site-specific fieldmeasurements.Arangeofdatasourcesandprovidersexist, meansofdeterminingmetoceancriteriaisbymakinguselong-term The preferred and access. offering highresourcepotentialarealsolikely toleadincreasedchallengesfordesign Metocean parametershaveaprimaryinfluenceonthefeasibilityofprojectsincesites development. requires anadequateconsiderationofmetoceanissuesthroughoutallstagesproject This documenthassoughttohighlightthatasuccessfulmarinerenewabledevelopment S ummar y remarks in situ monitoring and CIRIA C666 © COPYRIGHT CIRIA 2008 NO UNAUTHORISED COPYING OR DISTRIBUTION PERMITTED CIRIA C666