Tidal energy systems design optimization and control vikas khare

Tidal Energy Systems: Design, Optimization and Control Vikas Khare

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TIDALENERGY SYSTEMS

TIDALENERGY SYSTEMS

Design,Optimization andControl

VIKASKHARE

AssociateProfessor,ElectricalSchoolofTechnology,Management andEngineering,NMIMS,Indore,India

CHESHTAKHARE

DepartmentofElectricalEngineering,SGSITS,Indore,India

SAVITANEMA

DepartmentofElectricalEngineering,MANIT,Bhopal,India

PRASHANTBAREDAR

EnergyCentre,MANIT,Bhopal,India

Radarweg29,POBox211,1000AEAmsterdam,Netherlands

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ABOUTTHEAUTHORS

VikasKhare isanassociateprofessorinSchoolofTechnology,Management,andEngineering,NMIMS,IndoreM.P.,India.HeobtainedhisMTech(Honors)inenergymanagementfromDAVVIndore,India,andhisPhDfromNationalInstituteofTechnology inBhopal,India.Hismainresearchinterestsarerenewableenergysystems,optimization techniques,andgametheory.HeisalsoacertifiedenergymanagerundertheBureauof EnergyEfficiencyinIndia.Dr.KharehaspublishedvariousresearchpapersinInternationalrepudiatedjournalsandpublishedbooksonthetitlesof“RenewableEnergy”and the“FundamentalsofElectricalandElectronicsEngineering”.

CheshtaKhare obtainedherME(Honors)inpowerelectronicsatSGSITS,India, wheresheisalsopursuingherPhDinpowersystems.Mrs.Khareisanassistantprofessor intheDepartmentofElectricalEngineeringatSGSITSinIndore,India.

SavitaNema hasover20yearsofexperienceinresearchinrenewableenergyandcontrolsystems,andholdsbothanMEincontrolsystemsandaPhDinsolarphotovoltaics. Dr.Nemahasledseveralresearchprojectsandhaspublishedover40journalandconferencepapers.SheiscurrentlyaprofessorandheadattheDepartmentofElectricalEngineeringatMANITinBhopal,India.

PrashantBaredar isanassociateprofessorintheenergydepartmentatMANITinIndia. HereceivedhisPhDinhybridenergysystemsfromRajivGandhiTechnologicalUniversityinBhopal.Dr.Baredarhas20yearsofexperienceinmechanicalengineering.Heison theeditorialboardofmanyinternationaljournals,includingBLBIJESTandNational JournalofEngineeringScience,andisareviewerforfourinternationaljournals.Hehas successfullyorganizedfivenationalseminarsandconferencesonenergytopicsandhas delivered25expertlecturesandinvitedtalks.Hehasguided6PhDthesesand42MTech theses.Hehaspublishedonepatentonareconfigurablemechanismforwindturbine blades.Dr.Baredarhaspublished102researchpapersinnational/internationaljournals andatconferences,andhascontributedtothebooksentitled BasicMechanicalEngineering, PracticalJournalofBasicMechanicalEngineering,RenewableEnergySources and PracticalJournalof BasicCivilEngineering&EngineeringMechanics.Hehasservedasaconsultantonprojectssuch astheinvestmentgradeenergyauditoftheRajgarhCollectorateBuildingandfindinga solutiontoreducingbearingtemperatureinhydroturbinesintheIndiraSagarHydro Powerplant.Anumberofhighlevelresearchprojectsfundedbybothstateandcentral governmentaretohiscredit,andheisworkingonaprojectconcerningthesensitivity analysisandoptimizationofahybridsystemcombiningsolar,wind,andbiomasspower (Rs.452,000),fundedbyMadhyaPradeshCouncilofScience&TechnologyinBhopal.

IntroductiontoEnergySources

1.1ENERGYANDITSTRANSFORMATION

In physics andthefieldofengineering,energyisaversatilepropertyofageneroussystem thatcannotbedirectlypragmaticbutcanbeevaluatedfromonecircumstancetoanother withcertainperformanceparameters.Energyplaysanimportantroleinanyphysicalsystemandindifferentengineeringapplications,butitisdifficulttogiveadefinitionof energyinabroadwaybecauseoneformofenergyconvertsintodifferentformsof energy.However,themostfrequentdefinitionisthatitisthecapabilityofasystem toperformdesired work. Arunningpersonissaidtobemoreenergeticcomparedto asleepingperson.Inphysics,amovingparticleissaidtohavemoreenergythananidenticalparticleatrest.

Thecharacterizationofworkinengineeringphysicsisthefactionofa force throughoutadistanceandenergyisdeliberateintheidenticalunitsaswork.Ifanyhumanbeing pushesanentity n meters besideaconflictingforceof f newton, fn joules(Newton-meters) ofworkhasbeendoneonthegivenentity;thepersonnelbodyhaslost fn joulesofenergy andtheentityhasgained Fx joulesofenergy.In Fig.1.1,apersonemittedradiation energyfromhisorherowneyes,whichshowshowthepoweroftheeyecanbeconvertedintoradiationenergy.The SI unitofenergyisgivenbythe joule (J)(theequivalent

Fig.1.1 Radiationenergyfromeyes.

toanewton-meterora watt-second),the CGS unitisthe erg, andthe Imperial unitisthe footpound. Otherenergyunitssuchasthe electronvolt,calorie,BTU,and kilowatt-hour (1kWh ¼ 3600kJ)areusedinspecificareasofscienceandcommerce.Duetotheconservedproperty,thereisamajorsignificanceofenergyinengineeringbecauseitdepends onthe lawofconservationofenergy, whichstatesthatenergycanneitherbecreatednor destroyedbutcanbechangedintodifferentforms.Forexample,inamixergrinder,electricalenergyconvertsintomechanicalandsoundenergy.Ahairdryerisoneofthebest examplesthatshowshowoneformofenergyconvertsintoadifferentformofenergy. That’sbecause,inahairdryer,electricalenergyisconvertedintomechanicalenergy, thermalenergy,andsoundenergy.Bothexamplesshowthephenomenonof energy transformation becauseenergytransformationisthechangeofenergyfromoneformto another.

Energytransformationoccurseverywhereeverysecondoftheday.Energyisconvertedfromoneformtoanotherform;thisconversionisalsopartofenergytransformation,suchasthroughfuelcell chemicalenergy conversionintouseful electricenergy. For electricitygenerationthroughhydroenergy,first gravitationalpotentialenergyis convertedinto kineticenergy andthenthekineticenergyisconvertedintouseful electric energy throughaDCorACgenerator. Carnot’stheorem andthe secondlawof thermodynamics presentedsomedifficultiesregardingwhenenergycanbetransformed intootherformsofenergyby work and heat. Energyisascalaraswellasvectorquantity becausethedirectionofconversionandtransformationofenergyiselaboratedby entropy considerations.Mostenergytransformationsaredoneonasmallscale,butcertainlarger transformations,suchasthetransformationofelectricalenergy,arepossiblewiththehelp ofadditionalequipment. Fig.1.2 showsenergytransformationinwhichelectrical energy,mechanicalenergy,thermalenergy,soundenergy,chemicalenergy,andlight energyareconvertedfromoneformintoanother.

Fig.1.3 showstypesofenergytransformationintheformofrenewableandnonrenewableenergysources.Transformationofenergyintoconstructiveworkisaninnermostandprimarypartofthermodynamics.Attheprimarylevel,thetransformationof

Fig.1.2 Two-waypathofenergytransformation.

Energy transformation

Reversible transformation

Renewable energy source

Nonreversible transformation

Nonrenewable energy source

Fig.1.3 Typesofenergytransformation.

energyisdoneintwoways: reversible thermodynamicsand irreversible thermodynamics.Inthemechanical-to-electricalanalogy,thermodynamicallyreversibleisrelatedto renewableenergysourcesandthermodynamicallyirreversibleisrelatedtononrenewable energysources.Areversibleprocessisoneinwhichthiskindofindulgencedoesnot occur.Inthiscase,theenergymustpartiallycontinueasheatandcannotbeentirely recoveredasausefulformofenergy.

1.2TYPESOFENERGYSOURCES

Electricitythroughelectricalenergyisproducedbytheconversionandtransformationof availableenergy,whichisavailableindiverseformssuchasseveralnaturalsourcesthat includewindenergy,kineticenergyofwater,chemicalenergyoffuels,andnuclear energyofradioactivesubstances.Differentnaturalenergysourcesareoneofthemajor inputsforthemonetaryandfinancialgrowthofanynation.Indifferentdevelopingcountries,conventionalandnonconventionalenergysectorsareconsideredtobecritically importantforever-increasingenergyconsumption,whichrequiredenormousinvestmentstomeetsuchdemand.Besidesnonconventionalmethodsofelectricitygeneration,

conventionalmethodsofpowergenerationproduceelectricalenergythroughtheuseof primemoverssuchasdieselengines,petrolengines,andsteamengines,whicharealso usedfordrivingelectricalmachinesfortheconversionofelectricaltomechanicaland mechanicaltoelectricalenergy.Theothermethodsofproducingelectricalenergywithouttheuseofprimemoversarecallednonconventionalmethodsofelectricity generation.

Energycanbeclassifiedintoseveraltypesbasedonthefollowingcriteria:

•Primaryandsecondaryenergy.

•Commercialandnoncommercialenergy.

•Renewableandnonrenewableenergy.

1.2.1PrimaryandSecondaryEnergy

Primaryandsecondaryenergysourcesarethefirststageofclassificationofdifferent energysourcesforelectricitygeneration.Primaryenergyistheonethatthosesources thatonlyengrossinsertionorexertionwithorwithoutpartitionfromcontiguousmaterial,cleaningorgrading,beforetheinputenergypersonifiedinthatsourcewhichcanbe convertedortransformedintoheatormechanicalworkorthermalenergy.Secondary energyisalwaysthefinalandfinishingtouchoftheprimaryenergysourceandalsoresults fromconversionandtransformationofdifferenttypesofprimaryenergysources.The bestprimarysourceisonethatcanbeuseddirectlyaswellasappearinthenaturalenvironment,suchascoal,oil,naturalgas,wood,nuclearfuels,thesun,thewind,tides, mountainlakes,therivers,andtheearth’sheatthatsuppliesgeothermalenergy.There areseveralexamplesinwhichsecondaryenergysourcesderivefromthetransformation andconversionofprimaryenergysourcessuchaspetrolthatisderivedthroughthetreatmentofcrudeoilthenelectricenergyobtainedfromtheconversionofmechanical energyinhydroelectricplantsandeolianplants. Fig.1.4 showsthetransformationof primaryenergyintosecondaryenergy,inwhichwaste,nonconventional,andconventionalsourcesofenergyareconvertedintoelectricity,bioproduct,andpetroleum products.

1.2.2CommercialEnergyandNoncommercialEnergy

Theenergysourcesthatareusedtogenerateelectricityandthatareavailableinthemarketplacewithaspecificpriceareknownas commercialenergysources.Themostcommercializedformsofcommercialenergysourcesareelectricity,coal,andadvancedpetroleum products.Theyareusedforelectricitygenerationonthebasisofindustrial,agricultural, transportation,andcommercialdevelopmentofthedifferentcountriesofthemodern world.Inthewell-stabilizedindustrializedcountries,commercializedfuelsarethemajor sourcenotonlyforfinancialbenefit,butalsoforthemanydomesticresponsibilitiesofthe generalpopulation.

Primary energy

Biomass, wind, hydro, tide,sun

Waste

Secondary energy

Petroleum product, solid fuels and gases

Transformation

Crude oil, hard coal, natural gas, nuclear,etc.

Electricity & heat

Biofuels,etc.

Ontheotherhand,thedifferentenergysourcesthatarenotaccessibleintheprofitable marketwithapricetagareclassifiedas noncommercialenergysources.Noncommercial energysources,whichincludefuelssuchaslogs,cattledung,andagriculturalandurban waste,areconventionallygatheredandnotboughtatapriceusedparticularlyinrural areas.Thesearealsocalledtraditionalfuelsandareoftenignoredinenergyaccounting. Fig.1.5 showstypesofcommercialandnoncommercialenergysourcesinwhichrenewableandnonrenewableenergyisrelatedtothecommercialenergysources.

1.3NonrenewableENERGYRESOURCE

Anelectricity-generatedenergysourcethatisnotreplacedorrarelyreplacedveryslowly bynaturalprocessesiscalledanonrenewableenergysource.Fossilfuels,oil,naturalgas, andcoalaretheprimeexamplesofnonrenewableenergyresourcesinwhichfossilfuels arefrequentlytwistedbythedecompositionofplantandanimalwaste;however,therate oftheirproductionisextremelyslow.A nonrenewablesource isalsoknownasafinitesource andtheydonotrenewthemselvesforsustainablefinancialextractionwithinsignificant humantimeframes.Forexample,anonrenewableenergysourceiscreatedwhenoriginal organicmaterial,withtheadditionofheatandpressure,becomesafuelsuchasoilorgas thatisusedforelectricitygeneration. Metalores areanotherexampleofnonrenewable resourcesinwhichthemetalsthemselvesarepresentinenormousamountsintheearth’s crust.Theycanneverbefatigued,continuallybeingintenseandreplenishedovertime scalesofmillionsofyears.Inotherwords,metaloresarenonrenewablebutgenerally

Fig.1.4 Transformationofprimaryenergyintosecondaryenergy.

Fig.1.5 Typesofcommercialandnoncommercialenergysources.

Energy sources

Renewable energy source

Solar system

Wind system

Biomass system

Geothermal

Ocean system

Hydro system

Fig.1.6 Typesofenergysources.

inexhaustible.Inthisrespect,metaloresareconsideredtobeinvastlygreatersupplyto fossilfuelsbecausemetaloresareshapedbycrustalscaleprocessesthatmakeupamuch largerportionoftheearth’snear-surfaceenvironmentthanthosethatformfossilfuels. Thisisalsodonewithouttheneedforspecializedconditionswherecarbon-basedlife flourishesandfossilfuelscanform. Fig.1.6 showstypesofenergysourcesinwhichsolar, wind,etc.,fallintothecategoryofrenewableenergysourcesandnonrenewableenergy sourcearedividedintotwotype’s,traditionalandalternative.Traditionalenergysources areusedasaninputinalternativeenergysourcesforthegenerationofelectricity.

Table1.1 presentstypesofenergysources,theirconversion,andapplication.

Table1.1 Typesofenergysourcesandtheirapplication

EnergysourcesEnergyconversionandusageform

HydroEnergySystemPowergenerationorelectricitygenerationneartodamarea

BiomassEnergysystemHeatandpowergeneration

GeothermalEnergy system Urbanheating,powergeneration,hydrothermal

SolarEnergysystemSolarhomesystem,standaloneorhybridizedelectricitygeneration DirectsolarEnergysystemPhotovoltaic,thermalpowergenerationaswaterheatingsystem WindEnergysystemPowergeneration,windgenerators,windmills,waterpumps WaveEnergysystemNumerousdesignsofwavelagoonandwavedragon

TidalEnergysystemBarrages,singleanddoublebasintidalstream

1.3.1CategoriesofNonrenewableResourcesforElectricityGeneration

Nonrenewableresourcescangenerallybeseparatedintotwomaincategories:fossilfuels andnuclearfuels.

• Fossilfuels:

Fossilfuelsarethepartsoforganicmatter,sometimesplants,thathavedecomposedand compressedovertime.Theyhavebeencompressedbetweendifferentlayersofthe Earth’ssedimentsforbillionsofyears.Thesedepositsandthematerialstwistedfromthem tendtobehighlyexplosive,makingthemanidealnonrenewableenergysource.Theyare difficulttoobtainastheyarenaturallyretrievedthroughdrillingormining,butfossilfuels aresignificantfortheeffortfortheabsoluteamountofenergytheyproduce.

• Crudeoil/petroleum:

Crudeoilisanonrenewableorconventionalenergyresourcethatbuildsupinfluidform betweenthelayersoftheEarth’scrust.Itisretrievedbydrillingintothegroundandby pumpingtheliquidout.Theliquidproductisthenrefinedandusedtogeneratemany differentelectricity-generatedproducts.Crudeoilisaveryresourcefulfuelandisusedto createplastics,artificialfoodflavorings,heatingoil,petrol,diesel,jetfuel,andpropane, amongothers.Theworldwidetopthreeoil-producingcountriesareRussia,Saudi Arabia,andtheUnitedStates.

• Naturalgas: NaturalgasescongregateunderneaththeEarth’scrustand,likecrudeoil,theymustbe drilledandpumpedout.Methaneandethanearethemostfrequenttypesofnaturalgases obtainedthroughsuchprocesses,andthesegasesaremostusuallyusedinhouseholdheatingaswellasgasovensandgrills.Russia,Iran,andQatararethecountrieswiththelargest recordednaturalgasreservesworldwide.

• Coal: Coal,oneofthemajorfossilfuels,iscreatedbycompactedorganicmattersimilartosolid rockanditisobtainedbymining.Outofallthedevelopingcountries,accordingtothe StatisticalReviewofWorldEnergypublishedin2014byBP,Chinaproducedanoutstanding48.3%(3240milliontons)oftheworld’scoalin2014,followedbytheUnitedStates,

whichproducedamere14.8%.Coalisthemostcommercialandconventionalenergy sourceusedtypicallyinhomeheatingandtherunningofpowerplantsforelectricity generation.

• Nuclearfuels: Theotherformofnonrenewableresourceusedtoproduceenergy,nuclearfuels,isprimarily obtainedthroughtheminingandrefiningofuraniumore.Uraniumisanaturallyoccurring elementfoundwithintheEarth’score.Mosturaniumdepositsoccurinsmallquantities, whichminersgathertogether,refine,andpurify.Oncegathered,theuraniumisbrought togetherandcompoundedintorods.Therodsarethensubmersedintotanksofwater.When itreachescriticalmass,uraniumbeginstobreakdownandreleaseenergythatheatsthiswater. Thisisknownas“fission.”Theheatedwaterthencreatespressureanditisthispressurethat drivestheturbinesthatgeneratetheelectricityweuseeveryday.Nuclearfuelsare key tomaintainingtheEarth’senvironmentbecausetheyarethecleanestofallnonrenewableresource.

1.4RENEWABLEENERGYSOURCESFORELECTRICITYGENERATION

Renewableenergysourcesarealsononconventionalenergysourcesthatcomefromnaturalresourcesthatarerepeatedlyreplenished,suchassunrays,windvelocity,natural waterresources,upanddowntides,waves,andgeothermalandthermalheat.Inrecent decades,about16%ofworldwidefinalenergyconsumptionandelectricityproduction wasdonebydifferentrenewableenergyresources.About10%oftheelectricityproductioncomesfromtraditionalbiomassand3.8%fromhydroelectricityorbyhydroelectric powerplants.Newrenewableenergysourcessuchasoffshorewindenergysystemsand hydrogenenergyaccountedforanother3%andthesetechniquesaregrowingveryrapidlyindifferentdevelopingcountries.Nowadays,thepercentageofnonconventional resourcesinelectricityproductionisaround20%with15.8%ofelectricitycomingfrom hydropowerplantsand3%fromotherrenewableenergysources.Renewableenergy sourcessuchassolarradiation,windvelocity,andthekineticenergyofwatereither directlyorindirectlyarelikelytosupplyenergyforalmostanother1billionyears,at whichpointthepredictedincreaseinheatfromthesunisexpectedtomakethesurface oftheEarthtoohotforliquidwatertoexist.

Renewableenergyresourcesprovidesignificantopportunitiesfor energy conservationwhileimprovingenergyefficiency andprovidingapollution-freeenvironment.Thisispartofsustainabledevelopmentbut,incontrasttootherenergysources,itis concentratedinalimitednumberofcountries.Rapidexploitationofrenewableenergy, energyefficiency,andscientificdiversificationofenergysourceswouldleadtoimportant energysecurity andfinancialbenefits.

Nowadays,renewableenergyisreplacingnonrenewableenergyinfourdistinctareas: electricitygeneration,hot water/space heating,motorfuels, andrural(off-grid)energy services:

• Powergeneration:Worldwiderenewableenergysourcesprovide19%ofelectricitygeneration.Renewablepowergeneratorsareincreasinginmanydifferentcountriesand

unaccompaniedwindenergysystemsareprovidingamajorsourceofelectricityindifferentcountries,forexample,14%inoneoftheUnitedStates,40%intheGerman stateofSchleswig-Holstein,and49%inDenmark.Somedevelopedanddeveloping countriesgetmostoftheirelectricitygenerationthroughrenewableenergy,suchas Iceland(100%),Norway(98%),Brazil(86%),Austria(62%),NewZealand(65%),and Sweden(54%).

• Heating:Solarheatingsystemsaresignificantlyinvolvedin nonconventionalheat in differentcountries,includingChina,whichproduced70%ofitsheatgeneration throughsuchtypesofheat-generatingresources.Mostoftheseheatingsystemsare installedinmultistoryfamilyunitapartmentbuildings,providingthehotwaterneeds ofanestimated50–60millionhouseholdsinChina.Worldwide,thetotalinstalled solarwaterheating systemsmeetaportionofthewaterheatingneedsofmorethan 70millionhouseholds.Theuseofbiomassforheatingcontinuestogrowaswell andinSweden,thenationaluseofbiomassenergyhassurpassedthatofoil.

• Transportfuels:Efficientrenewable biofuels havecontributedtoasignificantdeclinein oilconsumptionintheUnitedStatessince2006.The93billionlitersofbiofuelproducedworldwidein2009displacedtheequivalentofanestimated68billionlitersof gasoline,equaltoabout5%ofworldgasolineproduction.

Atthenationallevel,atleast30nationsaroundtheworldalreadyhaverenewable energycontributingmorethan20%ofenergysupply.Nationalrenewableenergymarketsareprojectedtocontinuetogrowstronglyinthecomingdecadeandbeyond,and some120countrieshavevariouspolicytargetsforlonger-termsharesofrenewable energy,includinga20%targetofallelectricitygeneratedfortheEuropeanUnion by2020.Somecountrieshavemuchhigherlong-termpolicytargetsofupto100% renewableenergy.OutsideEurope,adiversegroupof20ormoreothercountriestarget renewableenergysharesinthe2020–2030timeframethatrangefrom10%to50%. Fig.1.7 showsdifferenttypesofrenewableenergysourcesthatareusedworldwide forelectricitygeneration.

1.4.1MainstreamRenewableTechnologies

SolarEnergySystem

Solarenergyorenergygatheredthroughsolarradiationisthemosteasilyavailableand freesourceofelectricitygenerationsinceprimitivetimes.Energyfromthesuncomparabletomorethan16,000timestheworld’sannualcommercialenergyutilizationreaches thegroundeveryyear.Solarenergycanbeusedintwoways:solarelectricenergyand solarthermalenergy.Asolarthermalsystemproduceshotwaterorair,cooksfood,dries materials,etc.,withthehelpofthesun’sheat.Inasolarelectricenergysystem,solarphotovoltaicusessolarradiationtoproduceelectricityforhouseholdappliancesaswellas commercialandindustrialbuildings.

Thesolarelectricenergysystembasicallydependsonthephotovoltaiceffectand wherethephotovoltaiceffectiscreatedbythebeamanddiffusedsolarradiation.When

thephotovoltaicorsolarcellabsorbtheglobalsolarradiationwhichisthecombinationof photonsthenelectronsarestimulatedfurtherelectronscreatemovingveryquicklyand jumpintotheconductionbandandtheydepartholesinthevalenceband.Onthebasisof thefundamentalofp-njunction,someelectronsareattractedtowardthen-sidetomerge withholesonthenearbyp-side.Similarly,holesonthenearp-sideareconcernedto

Fig.1.7 Typesofrenewableenergysources.

Fig.1.8 Typicalsolarsystem.

mergewiththeelectronsonthenearbyn-side.Fig.1.8 presentsaphotovoltaicsystem consistingofdifferentdevices.

Asolarcelldoesnotproduceelectricityregularlyfor24h,meaningthatbatteriesare anessentialpartofasolarenergysystemastheystoretheenergygeneratedbysolarcells. Anothergroupofbatteriesprovidesthatenergyinintervalstothedemandsideduring cloudydays,nights,anddayswheretheloaddemandsareveryhigh.Thenumberofbatteriesisalwaysconsideredwiththeconceptofbatteryautonomy.Themostordinarytype ofbatteriesusedinasolarenergysystemisthedeep-cyclebatteries,whicharethecombinationoflead-acidandnickel-cadmium.Theyaremorecostlybuttheyhavealonglife andcanbedischargedatahigherlevel.

Thechargecontrollerisanimportantdevicefromthebatterypointofviewbecauseit increasesthelifecycleofthebattery.Whenthebatteryisfullycharged,itslifeisreduced atagiventimeinterval.Then,thechargecontrollerdoesn’tallowtheelectricalloadto prolongtheflowintothebatteries,whichincreasesthelifecycleofthebattery.Inhousehold,commercial,andindustrialapplications,theloadmaybealternatingcurrent(AC)or directcurrent(DC).IftheoutputofthesolarsystemisDC,thentheinverterisconnected withthewholesystembecauseitisadevicethatconvertsDCintoAC.TheusageofAC isessentialbecauseithasbeenmostlyusedforallkindsofdomesticappliancesaswell asindustrialsectors.Aninverterisusedwhereasourceofincessantelectricvoltageis allocatedandwhereanalternativeelectricvoltageisused,ashappenswithinstalled solarcellsonbuildings.Theefficiencyoftheinverterisquitehighandvariesbetween 94%and96%.

TherearefourmajorapplicationsforPVpowersystems: Off-griddomesticphotovoltaicsystems:Off-gridsystemsarepartofastandalonesystem, andsuchasystemprovideselectricalenergyatremotelocationsandvillagesthatare notconnectedtotheauthorizedelectricitygrid.Anumberofthesesystemshavebeen installedworldwideandtheyareoftenthemostappropriatemethodtomeettheelectricitydemandsofoff-gridcommunities.Off-griddomesticsystemsarecharacteristicallyaround2–3kWinsize,andtheyofferacost-savingalternativetoextendingthe electricitydistributiongridatdistancesofmorethan2–3kmfromexistingdistributionandtransmissionlines.

Off-gridnondomesticphotovoltaicsystems:Suchasystemisdesignedforcommercialand industrialbuildingsbecausethesesystemsarethemostappropriatearrangement, whereaminuteamountofelectricityhasahighvalue.Thismakesthesesystemscommerciallycostcompetitivewithothersmallelectricity-producingsources.Off-grid nondomesticsolarsystemsprovidepoweratalowoperationandmaintenancecost forawiderangeofapplications,suchascommunication,waterpumpinginagriculturesectors,vaccinerefrigeration,andnavigationalaids.

Grid-connecteddistributedphotovoltaicsystems:Thesesolarenergysystemsprovide energytoacommercialandindustrialbuildingorotherloadthatisalsoassociated withtheauthorizedutilitygrid.Thesesystemsareusuallyincorporatedintothebuilt locationandsupplyelectricalenergytoresidentialhousesaswellascommercialand industrialbuildings.Thereisnoneedforbatterystorageunitsbecausesuchsystems areconnecteddirectlytotheauthorizedelectricitygrid.Theoverallcostsofthese systemsarelowercomparedtoanoff-gridinstallation.Typicalsystemsarebetween kWandMWinsizeandelectricityisfedbackintotheauthorizedgridwhenthe on-sitegenerationexceedsthedemandoftheload.Grid-connectedsolarsystems nicelymatchtheresidentialloadpatternduringthesummerseason.

Grid-connectedcentralizedphotovoltaicsystems:Thesesystemsareinstalledfortwo mainpurposes:asanalternativetoconventionalcentralizedpowergenerationor forstrengtheningtheutilitydistributionsystem. Table1.2 showsthesummaryof advantagesandlimitationsofsolarenergysystems.

WindEnergySystem

Windissimplyaformofmovingairaswellapartofthesun’sraysbecause,whenthe earthheatsupfrombeamanddiffuseradiation,itreleaseswind.Thisisabalancedreactionbetweensunraysandwindtocooltheearth.Themovingairinflatesandeasily reachesamaximumheightthenfreshandcoolairfallsdownandmovesaswind.Differentialheatingofthegroundsurfacebythesuncausesthemovementoflargeairmasses. Suchatypeofairorwindisusedforelectricitygenerationifthewindspeedisbetween5 and25m/s.Electricitygenerationthroughwindisdonebywindenergyconversion

Solarenergyisacleanandrenewableenergy source Electricitygenerationdependsentirelyona country’sexposuretosunlight;thiscouldbe limitedbyclimate

SolarenergycausesnopollutionAsolarpowerstationdoesnotmatchthe poweroutputofsimilar-sizedconventional powerstations;theycanalsobevery expensivetobuild

Onceasolarpanelisinstalled,solarenergycan beproducedfreeofcharge

Solarenergywilllastforeverwhereasitis estimatedthattheworld’soilreserveswill lastfor30–40years

Verylittlemaintenanceisneededtokeep solarcellrunning

Table1.2 Summaryofbenefitsandchallengesofsolarenergy BenefitsChallenges

systems.Windenergyconversionsystemsconvertthekineticenergyofthewindinto electricityorotherformsofenergy.Windpowergenerationhashadamarvelous expansioninthepastdecade,andhasbeenrecognizedasanenvironmentallyfriendly andeconomicallyspiritedmeansofelectricenergyproduction.

Nowadays,windpowerisacompletelyestablishedandsustainablebranchofelectricitygenerationanditisworkedaccordingly.Theenergygenerationisnottheonlybasisto beconsideredwheninstallingnewwindturbines.Thecostofsystemefficiency,the impactonthesurroundings,andtheimpactontheauthorizedgridaresomeofthesignificantissuesofinterestwhenmakingdecisionsaboutnewwindturbineinstallations. Electricityistradedlikeanyothercommodityonthemarketandtherefore,thereare standardsthatdescribeitsquality.Inthecaseofelectricenergysystems,theyarecommonlyknownasthepowerqualitystandards.Anypieceofequipmentconnectedto theelectricgridmustfulfillthesestandards.Thisismainlyaninterestingandsignificant issuetobeconsideredinthecaseofwindenergysysteminstallationsbecausethestochasticnatureofwindandthestandardizedparametersofelectricityarejoinedtogetherthere.

Fig.1.9 showstheenergychainofelectricitygenerationthroughawindenergysystem, inwhichfirstwindenergyisconvertedintomechanicalenergyandthenfurtherconvert intousableelectricalenergy.

Awindturbineisthemainpartofawindenergysystembecauseawindturbine detainstheforceofwindvelocitywiththehelpofrotorblades.Rotorbladesareused toacceleratewindflowoveronesideoftheblade,whichleadstoalow-pressuresystem atthegivenside.Therotorbladeslifttotheareaoflowerpressurejustlikeanairplane wing,duetothedifferenceinpressurebetweenthetwosidesoftheblade.Whenthe rotorisconnectedtoashaft,duetotherotationoftheshaft,ageneratorproduceselectricalenergy.Theelectricitygeneratedinthegeneratoristransmittedanddistributed throughoverheadlinesfromthewindturbinehubdownthetowertoaninterconnection withthetransmissionsystem.Therearetwotypesofwindturbinesusedinwindenergy conversionsystems:ahorizontalaxiswindturbineandaverticalaxiswindturbine.The powerproducedbyawindturbinedependsontheaveragewindspeedandwindspeed

Fig.1.9 Energychainsofwindenergy.

distribution.Thedesignofwindturbinesandrotorbladesistheimportantcriterionof powergenerationbecauseeachwindturbinedesignisratedtogenerateelectricalenergy ataparticularwindvelocity.Thewindvelocityatwhichawindturbinewillstarttogeneratepowerisreferredtoasthecut-inwindspeed.Oncewindreachesaturbine’scutin speed,thewindturbinegenerateelectricalenergy,althoughverylittleatlowwind speeds.Aswindvelocityincreases,powergenerationincreasesuntilthewindreaches thespeedof25m/s,whichiscalledtheratedwindspeed.Attheratedwindspeed, thewindturbinegeneratesthemaximumamountofpowerforwhichitisrated.Wind turbinesarealsointendedtoshutdownatveryhighwindvelocitymorethan25m/s, referredtoascut-outwindspeeds,forfearofpotentialdamagetothesystem.Thewind turbineischaracterizedbyanondimensionalactasafunctionoftipspeedratio.

Theoutputofmechanicalpowercapturedfromwindbyawindturbinecanbeformulatedas:

Kineticenergy ¼ halfmass velocitysquared (1.1)

Kineticenergy ¼ 0:5mV2 (1.2)

Powerinthewind ¼ Kineticenergyinthewindpersecond

P ¼ 0:5ρmνχ v (1.3)

Where ρ istheairdensityinkilogramspercubicmeter(kg/m3), A isinsquaremeters (m2)and V isinmeterspersecond(m/s).

Thetorquedevelopedbythewindturbinecanbeexpressedas

Tt ¼ P =ωm (1.4)

where Pt istheoutputpower, Tt thetorquedevelopedbywindturbine, CP thepower coefficient, λ isthetipspeedratio, ρ istheairdensityinkg/m3, A isthefrontalareaof windturbine,and V isthewindspeed.

λ ¼ ωR =V (1.5)

where ω istheturbinerotorspeedinrad/s, R istheradiusoftheturbinebladeinm,and V isthewindspeedinm/s.

HorizontalandVerticalAxisWindTurbine

Horizontal-axiswindturbines(HAWT)consistsofarotorshaftandanelectricalgeneratorattheapexofatowerandmustbepointedintothewind.InHAWTssmallturbines areconnectedbyasimplewindvaneandlargeturbinesaregenerallyconnectedwitha windsensorthatisattachedwithanACorDCservomotor.Whenatowergenerates turbulencebehindit,theturbineisusuallylocatedupwindofitssupportingtower.Turbinebladesaremaderigidtoputoffthebladesfrombeingpressedintothetowerbyhigh winds.Additionally,thebladesarelocatedasubstantialdistanceinfrontofthetowerand aresometimestiltedforwardintothewindasmallamount.

Table1.3 Comparisonbetweenhorizontalandverticalaxiswindturbines

PerformanceHorizontalaxisturbineVerticalaxisturbine

Generatedpowerefficiency(%)50–6070

ElectromagneticinterferenceYesNo

MechanismofthewindsteeringYesNo

GearboxmechanismYesNo

BladerotationspaceQuitelargeQuitesmall WindconfrontationcapabilityWeakStrong Noise(Db)5–600–10

Cutinwindspeed(m/s) 2.5–5 1.5–3

Failurerateofsystem High Low

Operationandmaintenance Complicated Convenient

Revolvingspeed High Low

Cablepositionproblem Yes No

CourtesyofAeoloswindturbine http://www.windturbinestar.com/hawt-vs-vawt.html

Ontheotherhand,vertical-axiswindturbines(orVAWTs)havethemainrotorshaft arrangedverticallyandthemainadvantagesofthistypeofconnectionarethattheturbine doesnotneedtobepointedintothewindtobeeffective.Thisisabenefitofsiteswhere thewinddirectionishighlyuneven,forexamplewhenintegratedintocommercialand industrialbuildings.Themainlimitationsofthistypeofwindturbineincludethelow revolvingspeedwiththesignificanthighertorqueandhencethelargercostofthedrive train,thelowerpowercoefficient,the360-degreerotarymotionoftheaerofoilwithin thewindflowduringeachcycleandhencethehighlydynamicloadingontheblade,the vivacioustorquegeneratedbysomerotordesignsonthedrivetrain,andthecomplexity ofmodelingthewindflowrateaccuratelyandhencetheconfrontsofanalyzingand schemingtherotorpriortofabricatingaprototype. Table1.3 showsacomparativeanalysisbetweenHAWTsandVAWTsundercertainparameters.

Withaverticalaxis,theelectricgeneratorandthemechanicalgearboxcanbelocated nearthegroundusingastraightdrivefromtherotorcongregationtotheland-basedgearbox.Thisimprovesaccessibilityforoperationandmaintenance.Whenaturbineis mountedonarooftop,thebuildinggenerallyredirectswindovertheroofandthis candoublethewindspeedattheturbine.Iftheheightoftherooftop-mountedturbine towerisapproximately50%ofthebuildingheight,thisisneartheoptimumformaximumwindenergyandminimumwindturbulence. Fig.1.10 showsdifferentpartsofthe verticalandhorizontalaxiswindturbines. Table1.4 showsadvantagesandlimitationsof windenergysystems.

BiomassEnergySystem

Electricitygenerationthroughabiomasssystemisarenewableandnonconventional energysourcewherebiomassisabiologicalmaterialthatisderivedfromlivingorrecently

High

Low

Thewindisfreeandwithmoderntechnology, itcanbecapturedefficiency

Itisapollution-freeenergysource

Remoteareasthatarenotconnectedtothe electricitypowergridcanusewindturbines toproducetheirownsupply

Manypeoplefindwindfarmsaninteresting featureofthelandscape

Windturbinesareavailableinarangeofsizes, whichmeansavastrangeofpeopleand businessescanusethem

Thestrengthofthewindisnotconstantandit variesfromzerotostormforce

Awindturbinecannoisy.Eachonecan generatethesamelevelofnoiseasafamily cartravelingat70mph

Whenawindturbineismanufactured,some pollutionisproduced

livingorganisms.Alivingorganismreferstoplantsorplant-derivedsubstancesthatare particularlycalledlingocellulosicbiomass.Asareversibleornonconventionalenergy source,biomasscaneitherbeuseddirectlyorindirectlyafteritisconvertedtodifferent formsofbiofuel.Conversionofbiomasstobiofuelcanbedonebythreesignificant methods:thermal,chemical,andbiochemical.

Worldwide,biomasshasalwaysbeenanimportantenergysourceandoffersdifferent advantages,includingthatitisrenewableorreversible,widelyaccessible,andcarbon neutral.Itcanalsooffermomentousemploymentintheruralareas.Biomassisalsocompetentatprovidingfirmenergy.Worldwide,about32%ofthetotalprimaryenergyuseis

speed shaft rotation

speed shaft rotation Blade Tower Horizontal rotor Vertical rotor

Fig.1.10 Verticalandhorizontalaxiswindturbines.

Table1.4 Summaryofbenefitsandchallengesofwindenergy Benefits Challenges

Municipal organic waste

Food industry waste

Ley crops

Collecting

stillfrombiomassandmorethan65%oftheworld’spopulationdependsuponitforits energyneeds.Biomassmeansallmaterialsthatcomefromlivingorganismssuchasthe wasteofplantsandanimals,wood,agriculturalwastes,anddeadpartsofplantsandanimals.Becausealllivingorganismsholdcarboncompounds,biomasshasenergystoredin theformofchemicalcompounds.Themethodofharnessingenergyfromeachofthem couldbedifferent.Directburningofthesematerialsgenerallycausespollution,butitis themostinexpensiveformofenergy.Usingwoodwasteordriedcowdungasfuelgeneratesalotofpollutionsothatifcowdungisusedinabiogasplant,cleanfuelcanbe generatedanditbecomesapollution-freeenergygeneratingsource.Mostlyinvillages, alltypesofbiomassaretraditionallyburneddirectlytoproduceheat.Andifmodern methodsareused,theycanbeutilizedproperly.

Fig.1.11 showstheprocessofelectricitygenerationthroughabiomassenergysource.

BiomassConversionProcesstoUsefulElectricalEnergy ThermalConversion

Thethermalconversionprocessesuseheatorthermalenergyastheleadingmechanismto convertbiomassenergyintoanotherchemicalenergy.Energycreatedbyburningbiomassispredominantlysuitablefordevelopedcountrieswherethefuelwoodgrowsmore quickly.Thereareanumberofotherlesscommon,moreinvestigationalorproprietary thermalprocessesthatmaypresentsettlementsuchashydrothermalupgrading(HTU) andhydroprocessing.Somehavebeendevelopedforuseonhighmoisturecontentbiomass,includingaqueousslurries,thatallowsthemtobeconvertedintomoreconvenient forms.Someofthefunctionsofthermalconversionarethecombinationofheat,power, andcofiring.Inadistinctivecommittedbiomassenergygeneratingplant,efficiencies rangefrom7%to27%.Biomasscofiringwithcoaltypicallyoccursatefficienciesnear thoseofthecoalcombustor.Thistypeofenergyistechnicallycalleddendrothermal energywhenitisusedinenergy-generatingplantsasafuelforenergyproduction.

Fig.1.11 Step-by-stepprocessofelectricityproductionthroughbiomass.

ChemicalConversion

Adifferentvarietyofchemicalprocessesmaybeusedtoconvertbiomassintootherforms, suchastoproduceafuelthatismoreconvenientlyused,transported,orstoredorto exploitsomepropertyoftheprocessitself.Manyoftheseprocessesarebasedinlargepart onsimilarcoal-basedprocesses,suchasFischer-Tropschsynthesis,methanolproduction, olefins(ethyleneandpropylene),andsimilarchemicalorfuelfeedstocks.Inmostcases, thefirststepinvolvesgasification,whichgenerallyisthemostexpensiveandinvolvesthe greatesttechnicalrisk.Biomassismoredifficulttofeedintoapressurevesselthancoalor anyliquid.Therefore,biomassgasificationisfrequentlydoneatatmosphericpressureand causesincompletecombustionofbiomasstoproduceacombustiblegasconsistingofcarbonmonoxide,hydrogen,andtracesofmethane.Thisgasmixture,calledaproducergas, canprovidefuelforvariousvitalprocessessuchasinternalcombustionenginesaswellas substituteforfurnaceoilindirectheatapplications.Becauseanybiomassmaterialcan undergogasification,thisprocessisfarmoreattractivethanethanolorbiomassproduction whereonlyparticularbiomassmaterialscanbeusedtoproduceafuel.Inaddition,biomass gasificationisadesirableprocessduetotheeasewithwhichitcanconvertsolidwaste (suchaswastesavailableonafarm)intoproducergas,whichisaveryusablefuel.

Table1.5 showstheadvantagesandlimitationofabiomassenergysystem.

GeothermalEnergy

Geothermalenergyisoneoftherenewableenergysourcesusedbyprehistoricpeoplefor heatingandbathingpurposes.Nowadays,geothermalenergyisusedforelectricitygeneration.IntheUnitedStates,60geothermalpowerplantsgenerateelectricityandmany moreareindevelopment.MostofthesegeothermalenergyplantsareinCaliforniawith theremainderinNevada,Hawaii,Idaho,andUtah.ThewordgeothermalisthecombinationofthetwoGreekwords geo (Earth)and therme (heat).GeothermalenergyisproducedintheEarth’s core,whichisalmost4000milesunderneaththeEarth’ssurface.The double-layeredcoreismadeupofveryhot magma surroundingasolidironcenter.Very

Table1.5 Summaryofbenefitsandchallengesofbiomassenergy BenefitsChallenges

Biomassenergyhelpsincleanlinessinvillages andcities

Abiogasplantrequiresspaceandproducesa dirtysmell

ItprovidesmanureforagricultureandgardensTransportationofbiogasthroughpipesover longdistancesisdifficult

It’sgeneratescomparativelylesspollutionItisdifficulttostorebiogasincylinders

Itcanbegeneratedfromeverydayhumanand animalwastes,vegetables,andleft-over agriculture

Cropsusedtoproducebiomassenergyare seasonalandarenotavailableoverthe wholeyear

BiomassenergyisrelativelycheapandreliableAcontinuoussupplyofbiomassisrequiredto generatebiomassenergy

hightemperaturelevelsareincessantlytwistedinsidetheEarthbythedeliberatedecompositionofradioactiveparticles.

Surroundingtheexternalcoreisthe mantle,whichis1800milesthickandmadeof magmaandrock.Thefarthestlayeroftheearthandthegroundthatformsthecontinents andoceanfloorsiscalledthe crust.Thecrustis3–6milesthickundertheseaand15–35 milesthickonthecontinents.Thecrustisnotasolidpiece.Itisliketheshellofanegg, butitisbrokendownintopiecescalled plates.Magmacomesclosetotheground’ssurface neartheedgesoftheseplates.Thelavathateruptsfromvolcanoesispartlymagma.Deep underground,therocksandwaterabsorbtheheatfromthismagma.Wecandigwellsand pumptheheatedundergroundwatertothesurface.Geothermalenergyiscalleda renewableorreversible energysourcebecausethewaterisreplenishedbyprecipitationandthe heatisincessantlyproduceddeepwithintheEarth.Thereismorethanonetypeofgeothermalenergy,butonlyonekindiswidelyusedtomakeelectricity.Itiscalledhydrothermalenergy. Hydrothermalresources havetwocommoningredients:water(hydro)and heat(thermal).Dependingonthetemperatureofthehydrothermalresource,theheat energycaneitherbeusedformakingelectricityorforheating.

LowTemperatureResources:Heating

Hydrothermalresourcesatlowtemperatures(50–300degreesFahrenheit)arepositioned intheUnitedStatessomefeetunderground.Thistypeoflow-temperaturegeothermal energyisusedforgrowingcropsaswellasdryinglumber,fruits,andvegetables.Inthe UnitedStates,geothermalheatpumpsareusedtoheatandcoolhomesandpublicapartments.Eachyear,about60,000geothermalexchangesystemsareestablishedinthe UnitedStates.

HighTemperatureResources:Electricity

Hydrothermalresourcesathightemperatures(300–700degreesFahrenheit)canbeused togenerateelectricalenergy.Thesehigh-temperatureresourcesgenerateelectricityfrom twotypesofwells:drysteamwellsorhotwaterwells.Geothermalwellsare2–3miles deep.Inadrysteampowerplant,thesteamcomesfromthegeothermalbasin,whichis pipeddirectlyfromawelltoaturbinegeneratorandthentheoutputisintheformof electricalenergy.Inahotwaterplant,hotwateristurnedintosteam,thesteamisusedto generatepower,thenageneratorproduceselectricity.

WorkingofaConventionalGeothermalPowerPlant

Ageothermalsystemrequiresheat,permeability,andwaterforelectricitygeneration. TheheatfromtheEarth’scoreincessantlyflowsoutwardandisusedforelectricitygeneration.Sometimestheheatisfrommagmaandreachesthesurfaceintheformoflava, butitusuallyremainsunderneaththeEarth’scrust,heatingnearbyrocksandwater.

Fig.1.12 showstypesofgeothermalpowerplants.

Therearefourcommercialtypesofgeothermalpowerplants:(a)flashpowerplants, (b)drysteampowerplants,(c)binarypowerplants,and(d)flash/binarycombinedpower plants.

Flashpowerplant:Inaflashpowerplant,geothermal-heatedwaterunderpressureis estrangedinasurfacevessel,whichiscalledasteamseparator.Thesteamisdelivered totheturbineandthenageneratorisusedtogenerateelectricity.Theliquidis injectedbackintothereservoir.

Drysteampowerplant:Inadrysteampowerplant,steamisgenerateddirectlyfromthe geothermalreservoirtoruntheturbinesandthatpowerisusedthroughthegenerator togenerateelectricity.Inthistypeofpowerplant,noseparationisnecessarybecause wellsonlyproducesteam.

Binarypowerplant:Abinarypowerplantisarecentadvancementingeothermaltechnology.Ithasmadepossiblethefinanciallyviableproductionofelectricalenergyfrom geothermalresourceslowerthan150°C(302°F).

Flash/binarycombinedcycle:Thistypeofplantusesanintegrationofflashand binarytechnologyandprovidesbetteradvantagescomparedtotheindividual techniques.Insuchaplant,thegeothermalwaterthatflashessteamundercondensed pressureisfirsttransformedtoelectricitywiththehelpofabackpressuresteamturbine.Then,low-pressuresteamexitingthebackpressureturbineiscondensedina binarysystem. Table1.6 showstheadvantagesandlimitationofgeothermalenergy sources.

Fig.1.12 Typesofgeothermalpowerplants.

Table1.6 Summaryofbenefitsandchallengesofgeothermalenergy BenefitsChallenges

Geothermalpowerplantprovidessteadyand predictablebaseloadpower

Powerplantsaresmall,requirenofuel purchase,andarecompatiblewith agriculturaluses

Geothermalplantsproduceasmallamountof pollutantemissionscomparedtotraditional fossilfuelpowerplants

Althoughcostshavedecreasedinrecentyears, explorationanddrillingforpower productionremainexpensive

Theproductivityofgeothermalwellsmay declineovertime

Thesuccessratefordiscoveringgeothermal resourcesinnewuntappedareasis approximately20%

Usingthebestgeothermalresourcesfor electricityproductionmayrequirean expansionorupgradeofthetransmission system

WaveEnergy

Waveenergyisanotherrenewableorreversibleenergysystemthatisthepartofenergy transformationbecauseitextractsenergydirectlyfromsurfacewaves.Scientistbelieve thatthereisanadequateamountofenergyinoceanwavestoprovideupto3terawatts ofelectricity.Butonemajorlimitationiswaveenergycannotbeharnessedeverywhere andthewesterncoastsofScotland,SouthernCanada,SouthernAfrica,andAustraliaas wellasthenortheasternandnorthwesterncoastsoftheUnitedStatesaretherichareasfor electricitygenerationthroughwaveenergy.ThePacificNorthwestareaaloneiscapable ofproducing40–70kilowatts(kW)per3.3ft(1m).

WaveEnergyResources

Waveenergycanbemeasuredasanintenseformofsolarandwindenergy.Windsare producedbythedifferentialheatingoftheearthandwhenairpassesoveropenbodiesof water,windisconvertedintowaveswiththehelpofprecisemechanisms.Suchamechanismisusedtoproduceelectricalenergywiththehelpofwaveenergy.Three-stepprocessesappearinwhichwavesaregenerated.Initially,windcirculatesovertheseasurface andexertsadivergentstressonthewatersurface,withtheresultingoutputintheformof waves. Table1.7 showstheadvantagesandlimitationsofawaveenergysystem. Inanotherprocess,disorderedairflowsclosetothewatersurface,creatingspeedily unreliableshearstressesandpressurefluctuations.Wherethesefluctuationsareinphase withaccessiblewaves,furtherwaveprogressoccurs.Finally,whencertainwaveshave reachedadefinitesize,thewindcaninfactexertastrongerforceontheupwindface ofthewave.Theprocessismaximizedwhenthespeedsofthewindandwavesareequal. Windenergyconvertedintowaveenergyistheprocessofenergytransformation. Theamountofenergytransferredandthesizeoftheresultingwavesdependonthewind

Table1.7 Summaryofbenefitsandchallengesofwaveenergy BenefitsChallenges

Dependenceonforeigncompaniesforfossil fuelscanbereducedifenergyfromwave powercanbeextracteduptoitsmaximum

Thebiggestadvantagesofwavepoweragainst mostoftheotheralternativeenergysources isthatitiseasilypredictableandcanbeused tocalculatetheamountthatitcanproduce

Alsounlikefossilfuels,creatingpowerfrom wavescreatesnoharmfulbyproductssuchas gas,waste,orpollution

Thebestthingaboutwaveenergyisthatitwill neverrunout.Therewillalwaysbewaves crashingupontheshoresofnationsnearthe populatedcoastalregions

Itissafe,clean,andoneofthepreferred methodstoextractenergyfromtheoceans

Dependsonthewaves—variableenergy supply

Needsasuitablesitewherewavesare consistentlystrong

Mustbeabletowithstandveryroughweather

Wavepowerisintheveryearlystagesof development,whichmakesspeculatingon costsharder

Anotherdownsideisthatitdisturbs commercialandprivatevessels

velocity.Ateachstepintheprocess,energyisconcertedsothatsolarenergylevelsof typicallyabout110W/m2 canbefinallyalteredintowaveswithenergylevelsofover 1000kWpermeterofcrestlength.

PowerAssociatedtoaSeaWave

Oceanwavesconveymechanicalenergy.Thepowerassociatedwithawaveofwavelength λ,height h,andafront B isgivenby

P ¼ 1=2ρgh2 (1.6) where ρ isthespecificweightofwaterand g isthegravityacceleration.Thepower PU acrosseachmeterofwavefrontassociatedwithauniformwavewithheight h (m)and wavelength λ (m)isthen

PU ¼ P =B ¼ 1=2ρgh2 λ (1.7) andisexpressedinW/m.

Forirregularwavesofheight h (m)andperiod t (s),anequationforpowerperunitof wavefrontcanbederivedas

Pi ¼ 0:42h2 T (1.8)

andisexpressedinkilowattspermeter(kW/m)ofwavefront.Itissignificanttonotethat wavepowervarieswiththesquareofwaveheight.Then,whenwaveheightisdoubled, itgeneratesfourtimesasmuchpower.

HydroEnergySystem

Ahydroenergysystemisconsideredtobearenewableaswellasanonrenewable energysystem.Thecharacterizationofasmallhydroenergysystemchangesbutan electricalenergy-producingcapacityofupto10megawatts(MW)isgenerallyestablishedasthehigherlimitofwhatcanbetermedasmallhydroenergypowerplant.This maybeextendedupto30MWinthe UnitedStates and50MWin Canada. Ahydro powerplantcanbefurthersubdividedintoaminihydro,whichisdefinedas <1000kW,andamicrohydro,whichis <100kW. Amicrohydro isfrequentlythe functionofhydroelectricpowersizedforasmallercommunity,singlefamilies,orsmall enterprises.Smallhydroplantsmaybeassociatedwithnonrenewableelectricaldistributioncircuitsasaresourceofinexpensiverenewableenergy.Ontheotherhand,a smallhydropowerprojectmaybebuiltinremoteareasthatwouldbeunprofitable toservefromacircuit,orinareaswherethereisnoauthorizedelectricaldistribution network.Becausesmallhydroprojectsfrequentlyhavenominalreservoirsandcivil constructionwork,theyareseenashavingarelativelylowenvironmentalimpact comparedtoalargehydro.Thisdecreasedecologicalimpactdependspowerfullyon thebalancebetweenstreamflowandelectricalenergyproduction. Fig.1.13 shows classificationofhydropowerplants.

HydroPowerBasics:HeadandFlow

Hydraulicpowercanbecapturedwhereveraflowofwaterfallsfromahigherleveltoa lowerlevel.Theverticalfallofthewater,knownasthe“head,”isessentialforhydropowergeneration;fast-flowingwateronitsowndoesnotcontainsufficientenergyfor

Fig.1.13 Typesofhydropowerplants.

usefulpowerproductionexceptonaverylargescale,suchasoffshoremarinecurrents. Hencetwoquantitiesarerequired:aflowrateofwater Q,andahead H.Itisgenerally bettertohavemoreheadthanmoreflowbecausethiskeepstheequipmentsmaller.

Thegrosshead(H) isthemaximumavailableverticalfallinthewater,fromthe upstreamleveltothedownstreamlevel.Theactualheadseenbyaturbinewillbeslightly lessthanthegrossheadduetolossesincurredwhentransferringthewaterintoandaway fromthemachine.Thisreducedheadisknownasthenethead.

Flowrate(Q) intheriveristhevolumeofwaterpassingpersecond,measuredinm3/s. Forsmallschemes,theflowratemayalsobeexpressedinliters/sor1m3/s.

PowerandEnergy

Power istheenergyconvertedpersecond,thatis,therateofworkbeingdonemeasuredin watts(where1W ¼ 1J/sand1kW ¼ 1000W).

Inahydropowerplant,thepotentialenergyofwaterisfirstconvertedtothe equivalentamountofkineticenergy.Thus,theheightofthewaterisutilizedtocalculate itspotentialenergyandthisenergyisconvertedtospeedupthewaterattheintakeof theturbine.Itiscalculatedbybalancingthesepotentialandkineticenergiesofwater.

Potentialenergyofwater Ep ¼ m g H (1.9)

Kineticenergyofwater Ek ¼ ½ m c 2(1.10)

Where,

m isthemassofwater(kg)

g istheaccelerationduetogravity(9.81m/s2)

H istheeffectivepressureheadofwateracrosstheturbine(m)

c isthejetvelocityofwaterattheintakeoftheturbineblade(m/s) Thus,jetvelocity c ¼ √ (2gH).

Thepoweravailableisproportionaltotheproductof head and flowrate.Thegeneral formulaforanyhydrosystem’spoweroutputis:

P ¼ ηρgQH (1.11)

Where:

P isthemechanicalpowerproducedattheturbineshaft(W)

η isthehydraulicefficiencyoftheturbine, ρ isthedensityofwater(1000kg/m3)

g istheaccelerationduetogravity(9.81m/s2)

Q isthevolumeflowratepassingthroughtheturbine(m3/s)

H istheeffectivepressureheadofwateracrosstheturbine(m)

Thebestturbinescanhavehydraulicefficienciesintherangeof80%tomorethan 90%,althoughthiswillreducewithsize.Microhydrosystems( <100kW)tendto be60%– 80%efficient. Table1.8 presentsadvantagesandlimitationsofhydroenergy systems.

Table1.8 Summaryofbenefitsandchallengesofhydroenergy BenefitsChallenges

Ahydroenergysystemisfueledbywater,so it’sacleanfuelsource

Onceadamisconstructed,electricitycanbe producedataconstantrate

Damsaredesignedtolastmanydecadesandso cancontributetothegenerationof electricityformanyyears/decades

Wheninuse,electricityproducedbydam systemsdoesnotproducegreenhousegases. Thisdonotpollutetheatmosphere

Damsareextremelyexpensivetobuildand mustbebuilttoaveryhighstandard

Thehighcostofdamconstructionmeansthat theymustoperateformanydecadesto becomeprofitable

Thefloodingoflargeareasoflandmeansthat thenaturalenvironmentisdestroyed

Ashydroelectricdamshavetobebuiltinareas withtheperfectconditions(landscape, precipitationlevels,etc.),themajorityof theseplaceshavealreadybeenusedfor hydroelectricdamconstruction

1.5WORLDWIDECURRENTSCENARIOOFRENEWABLEENERGYSYSTEM

Worldwideinterestforenergykeepsonrisingfromdevelopingnations,extendingthe worldwideeconomy,fastindustrialization,populationdevelopment,urbanization, andenhancedenergyaccess.Inthemeantime,thenegativesocial,monetary,andnatural effectsthatcomefromoverwhelmingdependenceonpetroleumderivativesareconvincinggovernmentstolookformoreeconomicalalternativestotakecareofelectricity demand.Alongtimeofarrangementwithfastinnovativeadvanceimplythatsustainable powersourcehasturnedintoaninexorablyreasonableandnonconventionalorreversible orrenewablealternative.Governmentsaroundtheglobearereevaluatingtheirenergy segmenttechniquesandgraspingatsustainablepowersources.Thus,remarkabledevelopmentinsustainablepowersourcearrangementoverthepreviousdecadehasdrivena temperatecycleofdiminishingcosts,risingspeculation,andinnovationadvancement. Asustainablepowersourceisanessentialanddevelopingpieceoftheworld’scontinuous energychange.Governmentsthroughouttheworldarejoiningthatagreement.Theutilizationofsustainableenergyistheirprimedecisionforupgradingaccesstomoderate, dependable,andcleanerwellspringsofcurrentenergyadministrations.Morethan170 nationshavebuiltupsustainablepowersourcetargetsandabout150havesanctioned strategiestocatalyzeinterestsinsustainableanddifferenttypesofrenewablepower sources.Basedonabouteverymeasure,sustainablepowersourcesaremakingstrides. Today,oneoutofeveryfiveunitsofenergyconveyedtopurchasersoriginatesfrominexhaustibleandrenewableenergysources.

At154gigawatts(GW)energysystem,thelimitfrominexhaustiblespoketo61%of allnewpowercreatinglimitincludedworldwidein2015.Inexhaustiblesourcesarethe topchoiceforgrowing,redesigning,andmodernizingpowerframeworksaroundthe

Table1.9 Annualinvestment/netcapacityadditionbytop5countries

Sources12345

Geothermalenergy system

TurkeyUnited States

MexicoKenyaGermany/ Japan

HydropowerChinaBrazilTurkeyIndiaVietnam

SolarPVcapacityChinaJapanUnited States United Kingdom India

Concentratingsolar thermalpower

MoroccoSouth Africa United States

WindenergysystemChinaUnited States

Solarwaterheating capacity

GermanyBrazilIndia

ChinaTurkeyBrazilIndiaUnited States

BioDieselsystemUnited States

BrazilGermanyArgentinaFrance

globe.Windandsolarpower,whichdirectedaround90%of2015interestsininexhaustiblepower,arepresentlyfocusedwithtraditionalwellspringsofpowerastheirexpenses havedecreasedoflate.Thecostofwindturbineshasfallenbyaboutthreetimessince 2009andthatofsunlight-basedphotovoltaic(PV)modulesby80%. Table1.9 shows theannualinvestmentornetcapacityadditionbythetopfivecountries.Theseimprovementsarereflectedinthelevelizedcostofpowerwithsomesustainableadvancements havingachievednetworkequality.Atpresent,coastalbreeze,biomass,geothermal, andhydropowerareforthemostpartfocusedorlessexpensivethancoal,oil,and gas-firedcontrolstations,evenwithoutfinancialboostsandinspiteofgenerallylow oilcosts.Atpresentscenario,theofferofsustainablepowersourcealtogetherfinalenergy consumptionremainsat18.3%.Theotherhalfcomprisescustomarybiomassutilizedfor warmingandcooking.Ontheoffchancethatallpresentnationaldesignsandapproaches arecompletelyactualizedwithoutextrameasures,theofferofasustainablepowersource intheaggregateworldwidefinalenergyconsumptionwillrisejustmarginallyby2030 from18.3%to21%. Table1.10 presentsthetotalcapacityorgenerationasoftheend of2015forthetopfivecountries.Theworld’sessentialenergyrequirementwillmoderateandpercapitaenergyrequirementwillcrestbefore2030becauseofexceptional efficienciesmadebynewadvancementsandmorestringentenergysources.Since 1970,theinterestinelectricitygenerationhasdramaticallyincreased.Newadvances to2060willkeepelectricalenergydevelopmentdirectinrespecttorecordedpatterns andwillempowerindustrializedeconomiestoprogressallthemorerapidlyintothe administrationandmanageabilityofdevelopment.

Thesedays,energyconsumptionisdividedintothreecategoriesofmusic:unfinished symphony,modernjazzandhardrock.“Modernjazz”isaboutsparkly,digitallydriven

Table1.10 Totalcapacityorgenerationoftop5countriesatendof2015 Sources12345

BiopowergenerationUnited States

Geothermalpower capacity

ChinaGermanyBrazilJapan

United States PhilippinesIndonesiaMexicoZealand

HydropowercapacityChinaBrazilUnited States CanadaRussian Federation

Hydropower generation

ChinaBrazilCanadaUnited States

SolarpowercapacityChinaGermanyJapanUnited States Italy

SolarPVcapacityper capita

GermanyItalyBelgiumJapanGreece

WindpowercapacityChinaUnited States GermanyIndiaSpain

Windpowercapacity percapita

DenmarkSwedenGermanyIrelandSpain

marketplaces,theslightlylessenthusiastic“unfinishedsymphony”isaboutpromising greenermock-upsforgrowth,and“hardrock”isanopportunityforbothlowandgrimy growth.Basedonnewscenarios,thefinalenergyconsumptionby2050willbe20%in unfinishedsymphony,35%inmodernjazz,and42%inhardrock.Primaryenergy demandthrough2050raisesjust9.5%inunfinishedsymphony,24%inmodernjazz, and32%inhardrock.Percapitaprimaryenergyrequirementpeaksbefore2025with amaximumannualpercapitausageofenergyreaching1.8TOE.Energyconcentration willturndownthreetimesfasterinmodernjazzandunfinishedsymphony.Considerable efficiencieswillbeincreasedthroughthedeploymentofsolar,wind,andbiomasselectricitygenerationcapacity.Transformationratesforthesenonconventionalenergy sourcesaremuchlargerthanthoseforconventionalsources,meaninglessenergywill beneededfromtheprimarysource.

Theworldenergyscenariosanalyzethefateofenergyto2060.Thisisanadequately longstretchtoinvestigatecentralchangesinthebusinessstructureandhowthebusiness behaves.Inthisarea,wetakeaganderattherecordeddriversofworldwideenergyfree marketactivityoveracomparativedayandage,1970–2015.Doingassuchisimperative onthegroundsthatthewaywedecipherhistoryshapesthewayweseethepresentandis abeginningstageforconsideringwhatistocome.Moreover,thisactivitysetsupa benchmarkagainstwhichwecangaugetheextentofprogressworldwideto2060.In spiteofhighmonetarydevelopmentanddevelopingenergyrequests,particularlyin developingcountries,thepartofcoalinessentialenergydecaysatapaceof0.4%p.a. from2014to2030.DecaysareseeneverywherethroughouttheworldasidefromIndia, where288MTOEofcoalareaddedtotheessentialenergysupplyintheperiod.

DevelopmentinIndiaiscounterbalancedbydecaysof350MTOEinNAMandEUR, wherecoaltopsbefore2020.Coaltopsin2020inChinaat2080MTOE,anddecreasesat arateof2.4%from2020to2060.By2060,coalhasdeclinedbymorethan1000MTOE inChineseessentialenergy.This,combinedwithdecreasesinNAM,EUR,andwhateverremainsofAsia,promptaworldwidecoaldecayof2.3%p.a.from2030to2060. Theworldsettlesataround1832MTOEofcoalinTPESin2060.

Overall,newresourcesinnoncustomaryenergysourcesandpowers(excluding hydropowerventuresbiggerthan50MW)was $241.6billionin2016.Itisareduction of23%contrastedwith2015andthedecaygoeswitharecordestablishmentofnonordinarypowerlimitsaroundtheworld.Interestinsustainablepowerbyvarious nationshassurpassed $200billioneveryyearforaslongas7years.Interestsinhydropowerventuresbiggerthan50MWwilladduptonewinterestininexhaustiblepower andenergizeswasinanyeventUSD264.8billionoutof2016.Forthefifthprogressive year,interestinnewnonregularlimit(countingallhydropower)wasgenerallytwofold thatinproducinglimitbytraditionalenergysource.Interestinreversibleenergysource keptonconcentratingonpowererabysunpoweredenergyframework,tookafter nearlybywindenergyframework,despitethefactthatinterestinthetwopartswas downinrespectto2015.Resourcebackofutility-scaleventures,forexample,wind ranchesandsunorientedparks,overwhelmedspeculationamidtheyear,atUSD 187.1billion.Creatingandrisingeconomysurpasscreatedandcreatingnationsinsustainablepowersourcespeculationwithoutprecedentfor2015,yetcreatednations retooktheleadin2016.

Patternsinnonregularenergyspeculationfluctuatedbylocalein2016,withventures upinEuropeandAustralia;downinChina,theUnitedStates,theMiddleEast,Africa, Asia-Oceania(asidefromAustralia),andLatinAmerica;andstableinIndia.Chinarepresented32%ofallfinancingsofsustainablepowersources,trailedbyEurope(25%),the UnitedStates(19%),andAsia-Oceania(barringChinaandIndia;11%);andtheAmericas (barringBrazilandtheUnitedStates),Brazil,andtheMiddleEastandAfricarepresented 3%each.Thereweretwofundamentalexplanationsbehindthedecreaseininterestin sustainablepowersourcesin2016.OnewasthelullininterestinJapan,China,andsome otherrisingnations.Theotherwasthenoteworthycostdecreasesinsun-orientedPVand incoastalandseawardbreezecontrol,whichlikewiseenhancedthecostintensityofthose innovations.

Accordingtothe RenewableCapacityStatistics2017, publishedbytheInternational RenewableEnergyAgency(IRENA),theglobalcumulativerenewablegeneration capacityreached2006GW.In2016,capacitygrewby8.7%,accordingtoIRENA’slatest data,witharecord71GWofnewsolarenergyleadingtheglobalcapacityadditions.For thefirsttimesince2013,solarenergyoutpacedwindenergycapacityadditions.Itwasstill astrongyearforwind,with51GWofnewcapacity,followedbyhydropowerwith 30GW,andbioenergywith9GW.Theworldrenewableenergycapacityhasincreased

Fig.1.14 Worldwiderenewableenergycapacityuntil2015.

impressivelysince2007,whenitwasonly989,213MW,growingto2006,202MWin 2016. Fig.1.14 showsworldwiderenewableenergycapacityuntil2015.Thereport detailstheoverallfiguresforeachrenewableenergytechnologyaswellasfromeachcontinentandcountry.Asiaaccountedfor58%ofallnewrenewableenergycapacityadditionsin2016,increasingitscumulativecapacityto812GW,oraround41%ofthe world’stotalcapacity.Asiaalsocameoutasthefastest-growingregion,witha13.1% increaseinrenewableenergycapacity. Fig.1.15 presentsrenewablepowercapacities until2015.Itwasasyetasolidyearfortwist,with51GWofnewlimit,trailedbyhydropowerwith30GW,andbiovitalitywith9GW. Fig.1.16 showsrenewablepowerpercentageannualgrowthrate2005–2016.Thereportpointsoutthegeneralfiguresforeach sustainablepowersourceinnovationandinadditionfromeverylandmassandnation. Fig.1.17 showsSolarPVGlobalCapacity2005–2015(GW).Asiarepresented58%of allnewsustainablepowersourcelimitaugmentationsin2016,expandingitstotalability to812GW,oraround41%oftheworld’saggregatelimit. Fig.1.18 presentswindpower globalcapacity2005–2016.Asialikewiseturnedoutasthequickestdevelopingarea,with a13.1%expansioninsustainablepowersourcelimits.

Fig.1.15 Renewablepowercapacitiestill2015.