EPSS 101 - Lectures 9&10
EPSS 101 - Lectures 9&10
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r Photovolataics Conversion of photons directly into flowing electrons GHQ fin to C V Semicondluctor technolo gy Lecture 9 Selim Volltciic Energy lvletals NonMetals and Semiconductors Free Electrons Perimlic Tizihle at the Elements if MI K7 The presence of free electrons quotquotquotquot1qt l explains the differences in 3 T 0 properties between metals and WJBC1 nonmetals Qt TT l 3 r r Metals 1 P gt E39lri l39taIlct1C ttISLM39 quot High electrical and thermal Meta i conductivilty V Ductile opaque solids with I 39 lT39et3lllClUSterlf E EM 2 T T quot quotJ i NonMetals V0d39 Q HM 51 I 1 39Equot g 39 nt is wu s39 mgan Elements with la 3 Low electrical and thermal A Elements with Ilargely or completely lled valence electron so lets are nonmetals andl noble G039WUCllVlW fmm gases 39 Solids liquids or gases Brittle i Elements on the boundary such as Si Ge have a limited number offree electrons and are it sollld not metallllic luster N ll39Meta39 called metaloids OF semiconductors lilllwlg 39eteI im S to tlmw lrhtet glh 39quot W 3quotl Late iquot3CLW E 339 L W I Reset 39 W6 33 titg H tgim an eiletm A in 1D TquotIt Semiconductors H overlap 397 6 39u 5 w g 1 1 l39 I H I1 A E 073 to tr E An I7 43 L1 1 in 1 1 27 a age 212 E IInJ I I2 ill Ei asst D at a 0 C43950 I M OJTII i ti 7 lI 2l3939 3 N 3 739 T metal serniconductor insulate W 35 Whether an electron can befree de nds on its energy level Electron energy levels are iuantizediand separated into energy bandsquot In a metal the valance band boundto the atom or molecule overlaps the conduction band free electrons in an insulatorj there is a large gap in energy between the valence band and the COli39 i dUCiiQll39i iband that almost no electrons can 0VeFC Ol Tle in a semiconductor the band gap is small enough that a usetul numtzier ol electrons can become free depending on their degree of excitation Semiconductor band gaps decrease with in fSmrilill tiot39iclcJctjn oil SEVt ttUTtitJ tDtSl ctgililomil us to Wtltt tiijruidiiE CU1 Iquoti 1t i3LhV W if it lZquot ItlJDiiE to 1 39i39E i rorit ltiiiioi til 39llT i3ui1391i 1 tquot pn Junctions At the interface between p and n semiconductor materials excess electrons from the n side diffuse across the junction into the p side and excess holes from the p side diffuse across the junction to the n side The result is a strong permanent electrostatic eld 06 volts for silicon The unique properties of the pn junction eke it the key building block of modern solidsate electronics inc u 7 g A P is ii iii 3 5 7 IvTI I Dil na hr1quot on luau 39 quotE139Tunno lquotunu pm urn El1a it It i I Ch EH1 II L211 11 39 r E l lggil 511139 39I am 1 l39r39I Elif tJllie3 eli ilquotiii iiilld Semiconductor Charge Carriers Silicon is a s emiconductolr with tour valence electrons that are shared between tour silicon atoms r Adding small arnitsof 10quot39 contaminants to the pure silioon structure is called gpg Adding doping maierlials with more valance electrons trarlstorms silicon into an ntype negative semiconductor with an excess of ellectron charge carriers A Adding doping materials with less valence electrons transforms silicon into a semiconductor where quotelectron holesquot are the charge carriers I ca It in n is i 3 I EDIEIli3 u IIHEI i iitl i GI ii I on ing no it onwI quot39lttntlIIi tit tig trtti tu til it ii it ii I9 no on Jul tilttillints 39llIj3Hm toilitt B in II g at I I tr I lleutaral n type patype 1739t lllt lf3 r cliliti n tonliii I ill l ill l ti5 to j139u1Gi SiiJlt39pt quotl quot i IquotJiltj1lquotZ quot s tZ1ddillquot39lij iiiorizi U lif ii39i 39 E P39il iEii actigiimj its utilenrse en t ij i39E39 t lltquott l iiiti39 Z 4 i tl l lt toiltl Tmiii1 it 3 e Semiconductors At Work tjin elevn liar fquot A itt iJ ll 3 Wm we tarhg Ptylpi 3 Nmtypi tragmlrur o r p mm Lil crmioa you13 he Frdnzi TH pIt39n39uem I birlim l3i iIiIquotg nfmga than J c c Lmi mi ii iampK N side P side Diode Electrical current flows from P to N side but not from N to P side Note current flow is in the direction of the positive charge carriers 70 g igjFDV Photovoltajg Cells 0 c P l h iiill39ItHhbL lEmiquot J it out G l A M I 3 quotWEI is from of E 39 in photovoltaic cells photons with sufficient energy to eject electrons from the semiconductor structure creating electronhole pairs The electrostatic eld created at the pn junction causes electrons to flow towards the n side and causes holes to flow toward the p side Solar cells consist of a pn jUlNlCtl DiW sandwliched between metal contacts to The n material is thinned to allow penetration of photons into the pn junction The accumulation of electrons and holes in the p and n material causes metal contacts become negatively and positively charged ejust like a battery Current flows through the cell driven by the absorption of photon energy LlED s lLig ht lEmitting Diodes work the opposite oil solar cells l U39iiiwl win HquotltutJtjh can i39ll tfl ihohgtn Precinct ct 39I 1quot Metal d Solar Cell Efficiency Imrfua Solar cell efliciencies are also M reduced by a variety oi optical eff 1 losses xi 39 A l I ll Reflection from top 3 f 39 0 surface f 39 I 4 f sllpitllnj by top 5 39 canhct oawngn 1 A 2 Absorption and reflection by top metal contacts 3 Absorption within pn material 4 Fteilection from rear surface T l These various factors reduce the realworld pealt etticiency of standard single junction silicon solar cells to 13 T The f ClEFlCY of a solar panel consisting of multiple solar cells is llurtlner reduced by the ll fraction the fraction of the area of the solar panel actually covered by solar cells a As with any electrical system there are additional losses due to electri quotl resistance E1 0 9 l etcquot etc etc Mostlsolar panels have a realworld ef ciencies of Dl e rCM Crystal line i i i 9 7 391 W A I By 39f FII riuPqF mtquot PFK l i P rgt p aiimorioe witwmapm 7 is llnmnuz2 moms cilurirq sits idol tethcleivlr l Thin Film 0 8 quot 39v139 Ilaintatam 39 39UquotlItquot39l ampt unumarrnIl r Inain 39 item B h 9 7 Iraq 7 7 r mardpzsgrniprrattasi Eigrgl igml not 9 ti ct elnlr B Multi julnctioln cells use multiple semi conductors to absorb solar photons at multi Tiewaveien the to iincrease ef cliency Lnytjr5 tllrL39Ct39Jtb usitlelr39 ll0 ll39quotlf T pnaen fl iign t ilip tflJ39i 5 l WE Solar Cellll Efficiency The quantum nature of light and electron energy states and the solar spectrum place fundamental limits on the ef ciency of solar cells quotlIF9 i 9w39a391 F9 I39I39V39 UIUIITJI rtvl i y 39 W l i tr no tw l ll quot quot 7 l 2 hquot 39 E y V V I x K I oc iv 39 1 if L Mr I I E 39 A l a K I XE V 1 a J I i 39 l quotV E l K 39 I K u ev P9z I e n a l 39 V 39 quot f I I u q 4 quot E quot Ii A l l l 392quot l 39 I it I l 7 I I quotX r L 39 J Ls 1 k r 111 7 I u n I 2 Recl 39solar spectrum Elmn39uavIrnurri current density TlquotB l39El5 a39 l39lquot39EWl39 U39 1 5 quot3lquotl C quot 39 39 39quotquotl1quot39 lt Longer wavelength photons with energies less than the energy of the semiconductor band gap can39t dislodge electrons and are lost to heat Shorter wavelength photons with energies greater than the energy of the semiconductor band gap can dislodge electrons but the l raction or photon energy above and beyond the band gap energy is also lost to heat a The above considerations limit the theoretical ef cien for single Junction solar cells to less than 35 7 Cm W i g it rnry Qvrei quot lquot lmlrUt tEr flC 1Utquot cliG Ereilt i39lelgiE5 OW l j tquotl ill t39llI y iP t bL yjH l llniquoti EXCTVE lill39i ClquotI39iCll iS Cmgp5 i mienll39 3 Tltjlo ll f i39cl7lTt t rquot RI HM FhgtiffgkJ 39f39eE393l d Q5 hC Clt Types of Solar Cells tumor by the supply l l IC jjiil minn A39 2i39di5l39 riinlurn139 Ave mior i Cquotiiquotltl tZlllllrlE rljlfiril lquott llt39l tilllm ltquotltll l39VfIu 5lWli0l in trt5t lnlnylle 39 l cplgl Ei lllquotlcll jln Lll393tlI l ll Seller Ell I lmC1U lquotl OH PFOQFGSS ill 30l3F Cell Efficiency Solar Cell Production and Costs 4 quot39Ter1y ll Jr k Bast Rnnaarchacnllll lEf rIamien EINlREL rlri cl 1 so 1 F 0 E i I l 9 E 7 T l E 250 W 39 E 1 E still L E150 5 i pr 4 lllll T 39e quot mtmga 1 is Q L 5 ill Gitr il39739Ill 1 Jan Line at 1391 E1 I an lJE l lquotl39l l 5 I rig anal 5 a Solar cell production has recently been increasing exponentially at a rate of 30 per year Solar cell prices have been decreasing exponentially at an average rate of 6 per year i4 J 0 i r l 5 ll llll t39l l I963 lfl ill llll l llllEl 39llll39 VbII ll nlI 1J41 m1I 4 1 FIG NH WE 2 N16 1135 Zinlgr etis ii lg o Fllrl9nl lrxllh ffl ulll l39l germ celli liefarrve Chettpei than ful ll illalfl 7 fl Site as crulcuf EH5 to pnlvvl lii Qlnlu9h elelll1tllCLll enlerlcjql elm EnlWe US T Photovo taic Energy lmpact First Solar Antelope Valley Solar Ranch One Project 2013 37 million cadmium telluride panels Previously disturbed agricultural land US Electric Power lnduntnr Nat Gernnnl Tbtel 4 billion klloulattlwours Lip 1 Ell ll Solar photovoltaics currently amount to a negligible fraction current US 5 ji l electrical power generation Callecn researchers have estimated that the entire electrical power needs Q of the country coullcl be suppliedl by a single giant solar panel with an area or if 6l1ailll square miles n 7 I Grid Parity and Net Metering As Ilia cost per watt ol photovottair energy do ereiisnes it will Laricoma equal to or less than the cost of grid power in more and more areas Soca oeul Grid P l39t lr39l51ill iIrL39triialgw39Irrti1on cost equal lo or less than that ol lirie itlllll f provided El39E39E1fEiIl grad has akready been sigiriiaaa a EJlnFly rsaari arras soars as Hawaiii Neat Fl9 IW E lng allows henioowj 2 to plug their Net Energy and Energy Payback Ratio The amount of energy required to obtain an energy resource is a signi cant issue for renewable and non renewable energy technologies It currently requires 1 barrel of oil to extract and re ne 5 barrels of oil this gure used to be 1 per 50 in the 192039s The increasingly high energy cost of oil extraction will eventually make the extraction of fossil fuel uneconomic makes the vast majority of fossil fuel deposits uneconomic Energy Payback Ratio EPR is the total energy produced divided by the energy required to build operate fuel and decommission sririr an ays garter suitable oonwsrsion to Are C39lJquotlE3913939 d3rMtly into l39I39ia39r riilotrminity rrtrrler Wl39llI Equotl will run eackwares and run up negative alerts usity char as 39j was rnesering arei1ea an eaiireeIJant39 way for hCt393939tl i239o n39l39jE395395 to balance rzut daily orr itirgy needs w lirmt seating to buy barteres to ssore erargy on site by alddeng power to the grid Ii iirig daylg it air39d taking power from lite grid during ii a 39 s 2T39iE ngrit p l Ctllquotr III1ID and other olirles are o ui1g slgnilanant tax iimeri1r39ires for home and business E r owners to install soar Celia StJlt39JfcI39Ir1 pEI iI3S such as Solar City o er solar kl Lik ti l39quot39tquotquot 1 Iit r the upfront costs 01 insta ing solar power by selling the power you generate over lease optirzris to homeowners to riiiLice or D yt 39lirnrr back to the i39lI39I39rIS Al of Use Mtr tl Grist l iri tj39 t i Uliiii1i Et li iin l iirefol in ElE t l rlr at Cairn r1iil E l LitlDl l39t lltE lr jiquot39s39quotquot la nefj ltUf l l39lquotlquot lll r Q it39lEl lira ii1 hi iiiLl trfiiimEl gar ri t rrrtnio r or lgor n oh l i l qr C r W ll will it t 3995 Projected Solar Photovolatic Energy Production Energy Payback Period EPP is the amount of time an energy source needs to operate to pay back the energy required to im build operate fuel and decommission it y I t For solar panels the EPP is currently 25 P A to 5 years EPP will decrease as production rates of s Piv q photovoltaics increase due to the mda v economies of scale g r r s 1 Photovolatics could be providing half of 1 squot c39 TT 39 quotquot 7 39 quot 1 quot f quotquot u r 1quotquot r39quot39 39 3 our electrical power needs by 2055 Hol iv39E39iiHurlr11rrIFV C 0l39lFl Hiuqr Lls Ii1ai P5 Pmducnon Energy Puyanct lrIrrttrIl39ry Groin Raw amp Frcieerilon of CA Enorgy all our Him E Iquot F o mrii as 39 mm l39 I 3V use in o n in p on an cin EFF reA r39ni39i39 39 rimIii39ii391 iilt T i all 39ricmI3939m39i iinPub 393aeif l5 a m 311I J igiu l 39 3539 39 quot iiiquot quot39 rquot 5 139iiF 394i 3bquotut 1 quot39at l7 lr ttJ lTJ tlCllili iELll iJ3 iilizi Wt ltril lquotll t il39rl39t TquotquotEt ill nlt flllj neiienerg 1 1 Je A r r criiE quotlltfUtil f lrrirrii lrtLr E FllE395W lat F V irimm i1em ilL3Ej g FT l39Wrl39Elld T l F39 tquoti lri397Il ti r iEl iiiquotf 7 lririE t oilir2rij rliti 539ireneilrilf Examples of Energy Payback Ratios EPR Hydroelectric 205267 lNnd 1180 Coal 511 Natural Gas 5 Nuclear 711 Sawmill waste 27 Solar photovoltaic 510 EPR for renewable energy is a strong functionquot of the pro39ected Ion evi ofthe energy system Lifetimes for solar photovoltaic systems have high uncertainties 1 wt or re til it it quotit l 3 ll El frigige ti39tquotlL39lilE rltirlrtg hlkj glfg rI39ilquot1i39IjhiJ i fr l E National Air Conditioner Addressing Climate Crisis Bush Calls For Development Of National Air Conditioner The ONION June 20 2007 gI39 StJ Egt3 2g5 LFJHI an Luau i u nu Dn39niuy by rain ig ip ll I r liJ JJ39lI1 rd I ulEli iraiuidmr ClI39fquotLIIilLII39H by llm your IIJII5 Tliu Miiuivrrim Ait GriruiilsiiiilzI II iLamp1wq Iv nDi ViU so 39eill riisli Jlegitt prim awrlri maidi 39 in llm riunmiri lli39ll Ff BGFl391 ca2tilnit cirlillitin 4 rm canal vI thin man l ta ll III crawl rug5 til i IIi 39l39BFlt urII1 E ifau Illjt ll uul utlsjliligi innliglhy p G C true FHEQTZH I7IIli391l 39Hr1l1I3939IlrliJtrIt li and IaiqpcuiI mt limit Itlf llama lI boilh ldgnvl and xiwmirla acezrmi llmli 39Ttv39g dniiltiourspiz39aiilIqiu i winI397ilJ1394 aEtll3n39i1lMr l I7Ciil1t vi hi niigrniriieslas hi1 Ii39II 1I1 Frssfvlgill Elm 5an miirIini Ft lllh 7 39I it i39Is39m39lII I1rIII ltheEri Ithiclrnm in393939 cut Iaquotidnr391I TiI39rE39i vnn int P511 fPHH 39lVP F39Ii l g39iIJ4quot39Il39i39t39iquotI 1I 39It iiril Ih n39 iI lift G t1l1Qll39ii sllrlrlii 3 In Irrrai i39iil39iLisi Quilwi rinipolfiIiiu1niI ie39iinn inIii onnnramiair1uur1 Ili1I39ui9isiii Itm ocuuluuoh i39iUcilng 1eltlan weand on imlist tedmalv r 3115 maclxin 1iiiWI cmrgmubwl t39iwi39Ir139Ir1i uiquotE RrI39uuIlt 39iI Hui lmwlfl lIr39lI f 0y5 39l39 gppiczd iiu a mri mtml Ior t39mnJ1t1 IJ39ru lllrl ISIAH anrlmiity Hung agella ihmry Fnlun III quotSu 1 ailr39n ni1lLmi n39l539n i39aHI l1139nnvIi rIin1 HE iilinlgh rlllq rml u39I39 3915 miiIl39P4 Jami IlTiigi Hi hi Lt1H39Dquot1 li l 1F fIquot39 1I1iE F 1 liE39 El tequotIl2riIuiIJ Fimi 1 MI 5 llquot I n llvEh l iTFEJr39 Hui ea rpwwmu lLl inane mi FF HJo ran all re1392u quotlquotEh or IJmun irlra oi Iriimziiiul 39Iil3Il liIl FaIii39relrm14 inn r39I Esqjgup main nfrlif rnpgitl cal Ilu phu391 iuin39iI mimaalmi rumlgirir iicpIctiaben ruin pinrgttmo Ell and gmzta mils Ina rImtu3usI IIiInq warm fiiilfliit TIII njmrrnri 0 tr 3955 rL4331 llvrn Jgt I1paling lllg I Mitreat AH mhlfl t rquot ud 0 Ii EIII prwilian lnl llm i1tuiVl39r39iDFJI 39ElltLih 1IliEilIrIilrir39tl l Ila U 393 1 quoti3939Isrrr aiubber 39I I0lill be rlraeltia Ii Ila iiIlh of uriuliri ilrii I leiaideil 39lI39IvH39i J39 uv rimsliii939 u i39iiiJu wins 39ruryli Prim PIJIEBIKI Siniplwin Iampor uizllirrn ls39lilIlLl1E39 i39li nrviu39i1n CI h 39ZIrlE and rlara3ii1h5 E i III1uLi W331 lzahui Cu1 iIi a2l39lIIa 39adtciPu Elulriru History of Wind Energy itecture 10 Wind Energy Arab Sailboat a goon so Persian Verticslt Axis D 39T l Z l 339 ls i39i39rtA EF 5 5 l l Eiirlquot rt s Er1Ergy Etirriinishing fossil reseerrzes Ct 1quotlZiquot porvospects fer ct tJ5T i1tl3912l39i3lliE future Amencan steelbladed vvater pumping windmill 1560 AD jqmundhhll gnmwuixu1m5 L 395 anr39qI I39 ii niihdu1 iFre39fessor Dewid Pciige C3lEJ391 l39HI 39i n1Clii39J 3C iU Greek Sailing Ship 500 EC Tall Ship 1300 AD Wind energy has been a key enabler of human civiItization through time T p5z 311 I D p T it icttJC H OUigt t tie Va E5 tii quot S df rtk i until 0 Atmospheric Circuilation Inna mast lurmmzzwr lquotC Atmospheric Structure Atmospheric circulation is driven quotquotquot39tlFlquot quot l o f m M primarily by latitudinaL A erature gm 1 squot hgracien7tstc used by enhpncedtscillqar p ea ing a e equal or re a ive o e gm R 7 T poles 1 es PZN 7 1 of abserbed solar radiation is rm Mi am ggwmw an an an converted into wind energy Earth is a low ef ciency heat engine The net effect ofwinds is to transport 92 i Wind patterns are strongly in uenced by the Earth39s rotation Eastwest winds are 10 taster than north south winds Warm air rises at the equator rains out moiisttire then descends at 30 latitude Tropical equiatoirial surface trade winds are part of equatorial Hadlley cells A Poleward of the tropics circulation is dominated by irregular westerly winds Eiu h jplrt re t Etttuiujh 0 CU39I 39iTrl33939i ttnr jlzf 0 Htttlej tell5 not Ct 30 n ii 3QegDpOio A cl 1til E a Que a Cltt A Equation of State ideal Gas Law P p R T where F is pressure N m3 p is density kg m393 Ft is the ideal gas cons ant 28 J kgquot Kquotand T is temperature K 7 The density of dry air is E 12 kg m3 at sea level nid decreases exponentiallly with altitude pz pa exp zih where pg is the density at at referenee altitude hRTg is the scale hieight and g is the gravitational acceleration h 9 km Most weather phenomena and human activities take place in the troposphere the lowest 10 km of the atmosphere which is characterized by a signi cant 10 Kkm vertical temperature gradient Wind Turbine Design iran1dl Iii1 12 Ieriigur quotr4 ld1It39iii39iquot fampiquotilI39 r l39 i Wind turbines generaliy consist ofa lower rotors and generator Horizontal axis turbines require a bearing to allow orientation relative to wind direction Blade con gurations vary depending on application Blade noise increases as the 5quot power of blade speedi so the more blades the quieter Wind Farms Because of the pr need for local control infrastructure and site requirements large 1 scale wind power production tends to be concentrated in p wind farms 5 quot3 Wind Turbine Scale ma 1 5 s Generator gearoox and brake assembly Vquot139 1 The scale of wind turbines is increasing rapidity Larger turbines have tower oosll per watt because Wind speeds increase with altitude greater efficiency Parts count per watt towers blades generators Energy Payback Period EPP is roughly independent of size so why not go bigger Current largest wind turbine is the Vestas V164 in Denmark has a rotor diarneter of 164 meters 747 wing span 64 meters rotor tip speed200 mph power levele MW For comparison the 10 MW Solar 2 thermal power plant in the Mojave Desert was 700 meters on a side U53 quot7quot ri 5 Econoniics of Wind Power Ci llilllnj IIiIllJ i wlnil line r nugih U1 IR1 IE1 JG 3 sew Pain M F J ti Euros per lliillwlni The estimated Energy Paybacli Penod EPP for large wind turbines is 33 months The net cost per Joule ofwind energy is approaching 1 that of fossil luels especially if CO1 emissions are E 1 taxed E Market price forwind power in Australia is now less 5 V than fossil fuels 3 Global wind power capacity is doubling every three 5 It years ifop global producers of wind energy are the European Union USA Garmariy China Spainquot indie iltally France FMII Fuel Wind terms can coexist wsth preexisting ifnd use such as cattle and UK rarer U5 39eo39era sii95 iie5 fcrwnd power are 5riquotra 1nr Qlllalln I C39lgen wmd genemtmg capacity 395 10 geolhermal than for tusam Quote in f ltslItquot T39 but rlliihnr F r watt an 3 xi soar lrllii39 li1 1iir uti i dlli395 the radii the enlarged but Jets i39iiirile 4Funiii l3 Wind Power in California Ceztlltmntil AnnualPwii iua 39liVlfE SmiLall at EU m N W d PGWEJ galla apng capad M Ealifomia has 39 1 39 39 dciulzired S39tT39rII E 2 I22 l 0 W1 391 533 l M 0 39 l 3 IE 21 rs Year m M H 2 39ita 235 B o 1 339 mi 3 iI E V 39 0K am am ru39 15 Megawatts Capacity J inraxaimia 39 I me 395 quotaim at High sustained offshore winds are potentially a huge energy resource Cost of offshore wind development is hat of onshore Development may incur signi cant costs risks and environmental impacts saauan Issues With Wind Power 39 Ugly factor Noise Reliability Overproduction Over Subsidized Stress to infrastructure 39 Bird Safety Human Safety NIMBY 1aJJmIu urmd Lrin 1 ill Luziflv fi a I39lfEniw39 an aim amzxhrai Mli39Fuquot539 39quot39Ii AG A Z 6 E North Carolina Outer Banks l l InjzdA Jail 7 Wi39t quot39iltl i fLi ltIlt39ltf Ml lls Hiti ri cilia Eli lsfitllitill 3 Alternative Wind Power Options High Altitude Tethered Air Rotor System Floating Multi turbines