Introduction
Seawaterisafluidcomposedofcountlessseawaterparticles.Undertheactionofexternalforce,theseawaterparticlesmoveperiodicallyneartheequilibriumpoint,whichformswaves.Wavesareanotherthrillinglarge-scalemacroscopicmovementofseawaterbesidestides.Thefasterthewind,thehigherthewaves.Eventhe10,000-tongiantshipwillflutterwithitwhenthewavesareoverwhelming.Windisthemainexternalfactorthatcauseswatersurfacefluctuations.Whenthewindpassesoverthesea,thesurfaceoftheseaisturbulentduetothefrictionoftheairandatmosphericpressure.Windspeedisthemainfactorthatdeterminesthesizeofwaves.Undernormalcircumstances,whenthewindreacheslevel10orhigher,theheightofthewavecanreach12m,whichisequivalenttotheheightofafour-storybuilding,andevenmoreoftenitishigherthan15m.Sixorsevenwindsarecommoninthesea,andthewavesitraisesare3mto6mhigh.Asmentionedearlier,seawateriscomposedofparticles.Themovementofwindortidalmovementwillcausethedisplacementoftheseawaterparticlesrelativetothesealevel,sothatthewaveshavepotentialenergy,andthemovementoftheseawaterparticleswillcausethewavestohavekineticenergy.Therefore,infact,waveenergyisthesumofkineticenergyandpotentialenergypossessedbytheoceansurface.Theenergyofawaveisproportionaltothesquareofthewaveheight,theperiodofmotionofthewave,andthewidthofthewave-facingsurface.Inaddition,themagnitudeofwaveenergyisalsorelatedtomanyfactorssuchaswindspeed,winddirection,continuousblowingtime,andflowrate.Forexample,thehugewavesgeneratedbytyphoonscanhaveapowerdensityofthousandsofkilowattspermeteroffrontalsurface.
Features
Thewavesintheoceanaremainlywindwaves,andtheenergyofwindcomesfromthesun,sowaveenergyisaverygoodrenewableenergysource.AccordingtothesurveyresultsoftheWorldEnergyCommission,theworld'savailablewaveenergyreaches2billionkW,whichisaconsiderableamount.Atthesametime,waveenergyalsoguaranteesitsgooddevelopabilityduetothefollowingadvantages:
(1)Waveenergyisakindofmechanicalenergy.Itisthehighestqualityenergyinoceanenergy,anditalsomakesenergyTheconversiondeviceisrelativelysimple.
(2)Althoughtheenergyfluxdensityofwaveenergyislow,itsreservesarelarge.Forexample,inthemid-latitude30-40°areaofthePacificOceanandtheeastcoastoftheAtlanticOcean,waveenergycanreach30-70kW/m,andevenupto100kW/minsomeplaces,whichcanguaranteethetotalamountofenergythatcanbedevelopedandutilized.
(3)Thewaveenergyavailableinwinteristhelargest,whichcaneffectivelyalleviatetheproblemofhugeenergyconsumptioninthisseason.
(4)Waveenergyisthemostwidelydistributedrenewableenergyintheocean,sowaveenergycanbecomeanenergysourceinremoteareasonthesea.
Waveenergypowergenerationtechnology
Waveenergypowergenerationcanbedividedintotwoparts:energyharvestingsystemandenergyconversionsystem.
Thefunctionofthecollectionsystemistocapturewaveenergy.Itsmainformsare:oscillatingwatercolumntype,oscillatingfloattype,pendulumtype,ducktype,rafttype,retractableramptype,clamtype,etc.Technologiestoincreasetheamountofwaveenergycaptureinclude:wavegatheringtechnologythroughthediffractionorrefractionofwaveenergy,andinertialwavegatheringtechnologythroughsystemresonancewithwaves.
Thefunctionoftheconversionsystemistoconvertthecapturedwaveenergyintoacertainformofmechanicalenergyorelectricalenergy.Itconsistsofthefollowingmainparts:airimpeller,low-headturbine,hydraulicsystem,mechanicalsystem,generator,etc.Inaddition,methodssuchascontrollableblades,variabledamping,rectification,andconstantpressurecanbeusedtoimprovetheconversionefficiency.
Accordingtotheuseofwaveenergy,wavepowergenerationcanberoughlydividedintoverticalmotionusingwaveenergy,horizontalmotionusingwaveenergy,waterpressureusingwave,andmotionusingwavewaterqualitypoints.Accordingtothestructureofthewaveenergydevice,itcanbedividedintothreetypes:oscillatingwatercolumntype,pendulumtypeandwavegatheringtype.Accordingtothebasicprinciples,itcanbedividedintothreemethods:usingtheoscillationandswayingmotionofanobjectundertheactionofwaves,usingthechangeofwavepressure,andusingthewaterpotentialenergygeneratedwhenthewaveclimbsalongthecoast.Thesethreemethodsarewhatweusuallyreferto.Ofpneumatic,hydraulicandwaterstorage.
Application
mycountryhasconsiderablewaveenergyresources.Thewaveenergycontentofoffshorewatersisabout150millionkW,andtheexploitableamountisabout23~35millionkW.Ingeneral,thereislessinthenorthandmoreinthesouth.Fromthegeographicalpointofview,itismainlyconcentratedintheseasnearGuangdong,FujianandShandong,followedbyJiangsu,Liaoning,ShanghaiandHebei.Thedistributionofwaveenergyisnotonlyrelatedtogeographicallocation,butalsohasobviousseasonalcharacteristics.Generally,waveenergypowerishigherinautumnandwinter,andsmallerinspringandsummer.Thischangeisparticularlysignificantnearislands.
mycountry’sfirstshore-basedwavepowerstationwasbuiltinShanweiin2000,andwasintegratedintothe100kVpowergridthroughatransmissionline.ItenteredtrialpowergenerationinFebruary2001,withamaximumpowergenerationof100kW.Thepowerstationhasavarietyofautomaticprotectionfunctions.Allprotectionfunctionsareautomaticallyexecutedundercomputercontrol,whichgreatlyreducesmanualintervention,makeswaveenergypowergenerationtechnologyclosetopracticality,andhasgoodsocialandenvironmentalbenefits.Atthesametime,the100kWpendulumwavepowerstationdevelopedbytheOceanTechnologyInstituteofTianjinStateOceanicAdministrationhasbeensuccessfullyoperatedinQingdao.