22/09/2014School of MarineNewcastleJniversityScience&TechnologyTidal EnergyVisit to Wuhan University of TechnologyDr Rose NormanSeptember2014www.ncl.ac.uk/marineSchoolofMarineNewcastleScience&TechnologyUniversityAContentsOriginof tidal energy：Tidalenergyconversionprocesses：Tidalresource.Tidalbarragesandlagoons。Tidal currentturbinesEnvironmental impact.Summaryann1
22/09/2014 1 Tidal Energy Visit to Wuhan University of Technology Dr Rose Norman September 2014 Contents • Origin of tidal energy • Tidal energy conversion processes • Tidal resource • Tidal barrages and lagoons • Tidal current turbines • Environmental impact • Summary
22/09/2014Schoolof MarineNewcastleScience&TechnologyUniversittNew.MoonSolar TideEarnOrigin of TidaliunSprng TideMoon福Energy?Earthrotatesabout polarFicstQuateCaxisonceevery24hoursNeap TideEarthrotatesaboutSunonceevery365daysMoon rotates about its ownaxisonceevery29.5daysFullMognMoonrotatesaboutEarthSpring Tideonceevery29daysSo Sun, Moon and EarthThird.Ouartetalignedonce every14.5Neap TidedaysEffectofmoon=2.15timesthat of sunCwww.ncl.ac.uk/marineSchoolofMarineNewcastleScience&TechnologyniversitTidal Energy Conversion Process-BarragesAveragepowerperArea,Atide for ebb-onlygeneration:BarrageHigh Tide LevepAR'gPRange,R2TT=tidal periodLowTideLevelp=densityofseawaterTurbineg=accelerationduetogravityCmann2
22/09/2014 2 Origin of Tidal Energy • Earth rotates about polar axis once every 24 hours • Earth rotates about Sun once every 365 days • Moon rotates about its own axis once every 29.5 days • Moon rotates about Earth once every 29 days • So Sun, Moon and Earth aligned once every 14.5 days • Effect of moon ≈ 2.15 times that of sun Tidal Energy Conversion Process - Barrages Range, R Area, A Low Tide Level High Tide Level Barrage Turbine Average power per tide for ebb-only generation: 2T AR g P 2 T T = tidal period ρ = density of seawater g = acceleration due to gravity
22/09/2014School of MarineNewcastleScience&TechnologyUniversityTidal Energy Conversion Process-CurrentPowerproduced perturbine:pAu'cP=-A=turbinesweptareap=densityofseawateru=velocity ofwaterC,=power coefficientwww.ncl.ac.uk/marineSchoolofMarineNewcastleScience&TechnologyOniversitTidal Resource-Tidal Range3DV920609m57GW(ap)a29GW30n6GW50HLLongifude ( deg)man3
22/09/2014 3 Tidal Energy Conversion Process - Current Power produced per turbine: p 3 Au C 2 1 P A = turbine swept area ρ = density of seawater u = velocity of water Cp = power coefficient Tidal Resource – Tidal Range
22/09/2014SchoolofMarineewcastleScience&TechnologyUniversinTidal Resource-Tidal CurrentHighPotential Areas forTidal ResourcesPentlandFirthandOrkneyWatersRound1DevelopmentSitesmaatSTieaw7Base MaSintegieArelUntedKingdotMaRSHECROWNPESTATEA
22/09/2014 4 Tidal Resource – Tidal Current
22/09/2014School of MarineNewcastleScience&TechnologyUniversityTidal BarragesSluiceGateWaterMarGenerationofelectricityBarragefromtidesisverysimilartoBasinhydroelectricgenerationexceptthatwaterisabletoflowinbothdirectionsLowWatMarkTurbineSimplestgeneratingsystemEstuaryFloorfortidalplantsisebbgenerating,involves adamorbarrageacrossanestuary.Sluicegates on the barrageallowthetidalbasintofillontheincominghightidesandtoexit through theturbinesystemontheoutgoingtidewww.ncl.ac.uk/marineNewcastleSchoolofMarineUniversityScience&TechnologyTidal Barrages95LeveBasinananeMSerLeveanoawodTime of DayTime of DayEbbGenerationFloodGenerationRVTwoWayGenerationTime of Daywww.ncl.ac.uk/marine5
22/09/2014 5 Tidal Barrages • Generation of electricity from tides is very similar to hydroelectric generation, except that water is able to flow in both directions. • Simplest generating system for tidal plants is ebb generating, involves a dam or barrage across an estuary. • Sluice gates on the barrage allow the tidal basin to fill on the incoming high tides and to exit through the turbine system on the outgoing tide Tidal Barrages Ebb Generation Flood Generation Two Way Generation
22/09/2014School of MarineNewcastleScience&TechnologyniversitTidal BarragesTheadvantagesoftidalbarragesinclude:theyproduceelectricityreliably;.theyarenotexpensivetomaintain;tidesaretotallypredictable.Disadvantages include:Veryexpensivetobuild;Affectaverywidearea-the environment ischanged formanymilesupstreamanddownstream.Manybirdsrelyonthetideuncoveringthemud flats so that they can feed;Onlyprovidespowerforaround10hourseachday,whenthetide isactuallymoving inorout;ThereareveryfewsuitablesitesfortidalpowerstationsPoweravailabilityisnotsynchronisedwithpowerdemandwww.ncl.ac.uk/marineSchoolofMarineNewcastleUniversityScience&TechnologyTidal LagoonsBuilt in shallow water,acompleteenclosureMultiplebasinsallowgreatercontrol ofpowergeneration timing850MprojectplannedforSwanseaBayinUKCapable of generating320MW,14hrsgeneration/day6
22/09/2014 6 Tidal Barrages The advantages of tidal barrages include: • they produce electricity reliably; • they are not expensive to maintain; • tides are totally predictable. Disadvantages include: • Very expensive to build; • Affect a very wide area - the environment is changed for many miles upstream and downstream. Many birds rely on the tide uncovering the mud flats so that they can feed; • Only provides power for around 10 hours each day, when the tide is actually moving in or out; • There are very few suitable sites for tidal power stations. • Power availability is not synchronised with power demand Tidal Lagoons • Built in shallow water, a complete enclosure. • Multiple basins allow greater control of power generation timing. • £850M project planned for Swansea Bay in UK • Capable of generating 320MW, 14 hrs generation/day
22/09/2014SchoolofMarineNewcastleScience&TechnologyJniversittTidal Current TurbinesMainlybuiltasprototypesBoth lift(rotor)devicesanddrag(likewaterwheel)deviceshavebeentested;Lift based devices can either be reciprocating or rotary (like apropeller);Tidesaretotallypredictableac.uk/marineSchoolofMarineNewcastleUniversityScience&TechnologyATidal CurrentTurbines
22/09/2014 7 Tidal Current Turbines • Mainly built as prototypes • Both lift (rotor) devices and drag (like water wheel) devices have been tested; • Lift based devices can either be reciprocating or rotary (like a propeller); • Tides are totally predictable. Tidal Current Turbines
22/09/2014SchoolofMarineNewcastleScience&TechnologyJniversittTidal Current Turbines1/10thScaleModel1/40thScaleModelwww.ncl.ac.uk/marineSchoolofMarineNewcastleScience&TechnologyUniversityTidal Current Turbines-InstallationInstallationofturbinesinatideraceisproblematicintermsoftimeandvesselstabilitySlacktide2-3hours-Vibrations in legsof jack-upvessel can cause stabilityproblemsStation keeping in tidecanbedifficult8
22/09/2014 8 Tidal Current Turbines 1/10th Scale Model 1/40th Scale Model • Installation of turbines in a tide race is problematic in terms of time and vessel stability – Slack tide 2-3 hours – Vibrations in legs of jack-up vessel can cause stability problems – Station keeping in tide can be difficult Tidal Current Turbines - Installation
22/09/2014School of MarineNewcastleScience&TechnologyJniversittTidal Current Turbines-lnstallationDynamicpositioningvessels suchastheNorthSeaGiantmoreexpensivetohirebut likelytogivewiderinstallationwindow.reducedinstallationtimeandgreatervesselstabilitySomecompanieshavedesignedtheirownvesselsuk/marineSchoolofMarineNewcastleScience&TechnologyHUniversityEnvironmental Impactof Tidal EnergyENERGYATANYPRICE?Valuingthe Severnasaininternationalasset9
22/09/2014 9 Tidal Current Turbines - Installation • Dynamic positioning vessels such as the North Sea Giant more expensive to hire but likely to give wider installation window, reduced installation time and greater vessel stability • Some companies have designed their own vessels Environmental Impact of Tidal Energy
22/09/2014School ofMarineNewcastleScience&TechnologyJniversittSummaryTidalbarragesarewell establishedtechnologyworldwideLa Rancebarrage inFrance operating since1966=Largestbarrage in world at Sihwa Lake,SouthKorea at254MWIssueswithenvironmental impactTidalcurrentturbines-developingtechnology-PrototypesystemsbuilttodateProjectsforarraydevelopments in UK,FranceandNorthAmericaLess environmentallydamaging andmoreflexiblethanbarrageschemeswww.ncl.ac.uk/marineSchoolofMarineNewcastleUniversityScience&TechnologyPThank you!nann10
22/09/2014 10 Summary • Tidal barrages are well established technology worldwide – La Rance barrage in France operating since 1966 – Largest barrage in world at Sihwa Lake, South Korea at 254MW – Issues with environmental impact • Tidal current turbines – developing technology – Prototype systems built to date – Projects for array developments in UK, France and North America – Less environmentally damaging and more flexible than barrage schemes Thank you!