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iot

1. Wearable Technologies & IoT (CHI3005)
Module-5
Energy Harvesting Techniques
Dr.Pratosh Kumar Pal
Assistant Professor, SCSE
VIT Bhopal University
Bhopal-Indore Highway, KothriKalan, Sehore, MP

2. ▪Wearabledeviceshavebecomepopular,andadvancementsbringtheconceptofWireless
BodyAreaNetworks(WBANs)closertoreality.
▪WBANscomposedofseveralsensorsconnectedthroughanetworkcanprovidecontinuous
readingsofpatients'healthwithoutgoingtothehospital.
▪Wearabledevicescanhelpusersindailytasksandencouragephysicalexercisesto
decreasediabeticpatients.
▪Theprimarypowersourceforwearabledeviceshasbeenbatteries,buttheyintroduce
severaldisadvantages,suchasbeingbig,non-biodegradable,andshortlifespan.
▪Energyscavengingfromtheatmospherehasbeenstudiedformanyyearsasanalternative
tobatteries,andenergysourcesincludevibrationalmotions,solarenergy,thermalenergy,
radio-frequency,chemicalenergy,andelectrostaticenergy.
▪Efficientattemptshavebeenmadetouseenergyscavengingforrunningelectronicdevices,
buttheextractedpowerisoftennotsufficienttopowerthesystemindependently,soa
storagemethodmustalsocontinuetowork.
Introduction (1)
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3. Types of Energy Sources
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4. ▪EnergyharvestingisusefulforpoweringremoteIoTsensorslocatedinrugged
conditionswheretraditionalpowersourcesarenotfeasible.
▪Energyharvestershavelimitations,soanamplifyingcircuitandstoragemodulelike
supercapacitorsareusedtopowerupthecircuit.
▪Differenttypesofenergyharvestingarediscussed,includingmechanical,chemical,
solar,RF,andthermalenergy.
▪Piezoelectricandtriboelectricgeneratorsareusedasmechanicalenergyharvesters,
enzymaticglucosebiofuelcellsforchemicalenergy,solarpanelsforsolarenergy,
rectifyingantennasforRFenergy,andthermoelectricgeneratorsforthermalenergy.
▪Energyharvestingsystemcomponentsincludeambientenergysources,AC-DC/DC-
DCconverters,voltageregulators,andenergystoragemoduleslikelithium-ion
batteriesorsupercapacitors.
▪Thecharacteristicsoftheenergystoragemoduledependonthespecificationsofthe
targetedapplication.
Introduction (2)
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5. Block Diagram of Energy Harvesting System
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6. ▪Thermal,solar,andradiofrequency(RF)areconsideredambientenergy
sourcesthatarepresentintheenvironment.
▪Mechanicalandchemicalenergiesareconsideredexternalenergysources
thatneedtobeproducedtostarttheharvestingoperation.
▪TypesofEnergyharvestingtechniques:
▪Piezoelectricity
▪Triboelectricity
▪Enzymaticglucosebiofuelcell
▪Thermoelectricity
▪Solarenergy
▪Radiofrequencyenergy
Introduction (3)
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7. ▪Piezoelectricmaterialstransformvibrationalmotionintoelectricenergy.
▪Leadzirconatetitanate(PZT)isthemostpopularsubstrateforpiezoelectric
harvesters.
▪OthermaterialsusedincludeZnO,PVDF,andBaTiO3.
▪Mechanicalstressappliedtothematerialcontrolsthegeneratedoutput
voltage.
▪Outputpowerofpiezoelectricgeneratorsishighercomparedtoelectrostatic
andelectromagnetic-basedgenerators.
▪Piezoelectricgeneratorscansupplypowerforimplantablemedicaland
wearabledevices.
(a) Piezoelectricity (1)
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8. ▪Typicalconfigurationforpiezoelectricharvestersisacantileverbeam
composedofsingleorseveralpiezoceramiclayers.
▪Microgeneratorsbasedonpiezoelectriccansupplypowerrangingfrom
microwattstomilliwatts.
▪Piezoelectricharvesterscanbeusedforwirelessdatatransfer,pacemakers,
batterycharging,etc.
▪Changingtheproofmass'sdimensionandimprovingthecantileverbeam's
designcanimprovetheharvester'sperformance.
▪Rectangular-shapedcantileversarewidelyusedandeasytoincorporatefor
scavengingenergy.
▪Outputpowercanbeincreasedbyamplifyingtheamplitudeandvibration
frequency.
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(a) Piezoelectricity (2)

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(a) Piezoelectricity (3)

10. ▪Triboelectriceffectoccurswhenmaterialscomeintocontactbyfriction,
movingelectronsfromonesubstancetotheothertoachieveanequalized
electrochemicalpotentialafterbeingpressed.
▪Certainmaterialsholdontotheirelectronswhileothersprefertokeepthem,
resultinginchargesontheirsurfaces.
▪Materialswithasignificanttriboelectriceffectareinsulators.
▪Thechoiceofmaterialsforconstructingtriboelectricnanogenerators(TENGs)
isvastandnotlimitedtoaparticularfrequencylikepiezoelectricharvesters.
▪TENGsproduceACvoltagegeneratedbytouchingandseparatingmaterials
overseveralcycles,requiringarectifyingbridgecircuittodriveelectrical
circuits.
(b) Triboelectricity (1)
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11. ▪KnownTENGconfigurationsareLateralSlidingMode,VerticalSeparation
Mode,StandingLayerFreeTriboelectricMode,andSingleElectrodeMode.
▪Theeffectoftriboelectrificationisdependentonmaterialsandimprovedby
increasingthecontactmaterials'cross-sectionareausingnanostructureslike
nanowiresornanoparticles.
▪TENG'slateralslidingmodeinvolveslockingonematerialandpermitting
anothertoslide,resultinginaccumulatedchargesonthematerials'surfaces.
▪TENG'sverticalseparationmodeoperatesbyseparatingtwomaterialsand
accumulatingchargesontheirsurfaces.
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(b) Triboelectricity (2)

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(b) Triboelectricity (3)
▪InbasicdiagramofTENG’slateral
slidingmode,onematerialis
locked,andanotherispermittedto
slide.

13. ▪Biofuelcellsuseglucosefortheconversionofstoredchemicalenergyinto
electricity,andtheyuseselectiveglucoseenzymessuchasGlucoseOxidase
(GOx)togenerateenergyfromcomplexsugar.
▪Biofuelcellsareacost-effective,renewable,andenvironmentallysound
solutionthatcangeneratesufficientpowertosupplysomemedicaldevices.
▪Theelementsofthebiofuelcellincludeananode,acathode,anda
separator.Theanodeandthecathodearenamedbioanodeandbiocathode,
respectively,andoxidoreductaseenzymesspeedupthereduction–oxidation
reactions.
▪Enzymeshavesomedrawbacks,includingbeinglessefficientatoxidation
thanmetals,requiringcentralizationataspecificlocation,andhavingan
estimatedlifespanofroughlydays.
(c) Enzymatic glucose biofuel cell (1)
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14. ▪Themainissuesinbiofuelcellsarethechoiceofbiocatalyst,theincreasein
thesurfaceareaofthetransductioncomponenttoincreaseoveralladsorption
ofthebiocatalyst,andtheincreaseintheworkinglifeofthebiofuelcellsfor
implantapplications.
▪DirectElectronTransfer(DET)andMediatorElectronTransfer(MET)are
methodsusedtotransferelectronsbetweentheelectrodeandtheenzyme's
activecenter,andDETisanexampleofamethodthatcanbeusedto
overcometheelectrontransferobstacle.
▪Glucoseisoxidizedbythebioanode,whilethebiocathodereducesoxygenin
enzymaticglucosebiofuelcells,asseeninFig.7.
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(c) Enzymatic glucose biofuel cell (2)

15. ▪Fig.6showsanexampleofDETmethodandFig.7showsthebiofuelcell.
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(c) Enzymatic glucose biofuel cell (3)

16. ▪Thermoelectricenergyconvertstemperaturedifferenceintoelectricity.
▪Theeffectwasfirstobservedin1821andisknownastheSeebeckeffect.
▪ThebasicconfigurationofathermoelectricgeneratorconsistsofoneN-type
andoneP-typesemiconductorbetweentwometalplates.
▪Severalthermocouplescanbeconnectedinseriesorparalleltomeetthe
necessarycurrentandvoltage.
▪Thevoltageproducedisproportionaltothetemperaturedifferencebetween
theplates.
▪TheSeebeckmaterialcoefficientplaysasignificantroleinraisingthepower
producedbytheheatdifference.
▪SemiconductorshaveamorenoticeableSeebeckeffectthanmetals.
(d) Thermoelectricity (1)
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17. ▪Nanocompositescanbeusedtoboost
thermoelectricmaterials'propertiesi.e.to
obtainhigheroutputvoltageandimproved
electricalconductivity.
▪Themostwidelyusedthermoelectric
materialsarezincantimonite(ZnSb),
silicongermanium(SiGe),andbismuth
telluride(Bi
2Te
3).
▪Thermoelectricgeneratorsareusedto
recyclewasteheat,inremoteareas,
spaceexploration,andpoweringsensors
andelectronics.
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(d) Thermoelectricity (2)

18. ▪Solarenergyisarenewableenergysourcethatcanbeusedtopower
electronics.
▪Photo-voltaic(PV)panelsareusedtoconvertsunlightintoelectricitythrough
aphoto-voltaiceffect.
▪PVcellshavethreelayers:thetopandbottomlayersaremetal,andap-n
junctionlayerisresponsibleforconvertingsunlightintoelectricity.
▪ThematerialsusedinthemanufacturingofPVcellsaremonocrystalline,
polycrystalline,andamorphoussilicon,withpolycrystallinecellshavingan
efficiencyofabout17%,andmonocrystallinecellshavinganefficiency
greaterthan20%.
▪PVsystemsarefoundinsmall,middle,andlargesizesandcanbeusedin
variousapplications,includingpoweringsensorsandelectronics.
(e) Solar energy (1)
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19. ▪Theelectricalmodelofthesolarcellinvolvesincidentlightproducing
electron-holepairsinthejunction,whichgeneratespotentialdifferencesat
thePNjunctionterminal.
▪Maximumpowerpointtracking(MPPT)modulesareassociatedwithsolar
systemstofindtheoptimumoperatingpointtoachievemaximumefficiency.
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(e) Solar energy (2)

20. ▪Electromagneticwavesarepresenteverywhereandcanbeharnessedfor
energy.
▪RFenergycanbeconvertedintousableenergyusingarectenna.
▪Rectennasaredesignedasdual-bandortriple-bandtoincreasethe
harvestedpowerandoperateonfrequenciessuchasGSM900,Wi-Fi,and
millimeterwaves.
▪ThecomponentsofarectennaincludeaDCpassfilter,rectifier,impedance
matchingcircuit,andantenna.
▪Theantennaisresponsibleforscavengingelectromagneticwavesandits
sizeandshapedeterminetheamountofcapturedpower.
(f) Radio Frequency Energy (1)
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21. ▪Printedantennasarecommonlyusedduetobeinglightinweight,lowcost,
andeasytofabricate.
▪ImpedancematchingnetworkplaysapartintheamountofDCpower
producedandisconsideredoneofthedesignchallenges.
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(f) Radio Frequency Energy (2)