Renewable Energy Sources. Solar Cells SJSU-E10 S John Athanasiou

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1 Rnwabl Enrgy Sourcs. Solar Clls SJSU-E10 S-2008 John Athanasiou 1

2 Rnwabl Enrgy Sourcs Rnwabl: Thy can last indfinitly 1. Wind Turbin: Convrting th wind nrgy into lctricity Wind, Propllr, Elctric Gnrator, Currnt Flow 2. Solar Clls Convrting th Sun s (light) nrgy dirctly into lctricity Intnsity of th sunlight Wavlngth of th sunlight Typ and surfac ara of th solar cll 3. Ful Clls Producing lctricity by combining Hydrogn and Oxygn to produc H 2 O 2

3 Enrgy Usag 3

4 Arizona to bcom 'Prsian Gulf' of solar nrgy (CNN) Abngoa Solar will oprat th $1 billion plant Th solar plant would b abl to powr 70,000 homs Arizona govrnor: No rason w can't b "Prsian Gulf of solar nrgy" Rgulators rquiring 15 prcnt of lctricity from rnwabl sourcs by

5 What ar Solar Clls? Solar clls ar dvics which convrt solar light nrgy dirctly into lctricity Sunlight contains packts of nrgy calld photons that can b convrtd dirctly into lctrical nrgy. This is rfrrd to as th photovoltaic ffct. Photo- mans light and -voltaic mans lctrical currnt; A solar cll provids dirct currnt (DC) lctricity, similar to battris. Battris howvr us lctrochmical raction. 5

6 Atoms Dmocritus c.300 BC An atom is composd of thr diffrnt particls: Nuclus- Cntr of th atom: 1. Protons (P + )-- positivly chargd. -- qual to th numbr of lctrons. 2 Nutrons -- no charg. Protons (P + ) Nutrons 3. Elctrons (-) -- ngativly chargd. -- orbit th nuclus. ( - ) Th outrmost lctrons of an atom dtrmin its chmical and lctrical proprtis 6

7 Matrial Classification (basd on th No of lctrons ( - ) on th outr valnc cll) 1. Conductors: Fw ( - ) Fr to mov and join adjacnt atoms. (with a littl prssur from an nrgy sourc /lctric fild). Thy lt lctricity flow thought thm asily. Coppr (Cu 2,8,18,1 ), aluminum, iron, stl 2. Insulators Many ( - ) Lazy, do not lik to mov, vn with a kick. Rubbr, plastic, glass, wood 3. Smiconductors: (half & half) Numbr of ( - ): somwhr in th middl. Conducting proprtis intrmdiat to thos of insulators and mtals. Silicon (Si 14 ) Addition of impuritis lik Phosphorus (P 15 ) and Boron (B 5 ) can incras thir conductivity. Currnt: th stady flow of lctrons which carry lctric charg (-) 7

8 Silicon Si 14, Boron B 5, Phosphorus P 15 - B ē ēē NSi P - 8

9 Smiconductor Doping How can w chang th lctrical proprtis of th pur Smiconductor matrial? By adding forign matrial to it, calld dopants. (impuritis) Boron, phosphorus, arsnic ar common dopants. Rat of low :1 vry 100,000,000 atoms high: 1 vry 10,000 atoms Silicon (Si) with Phosphorus (P 2,8,5 ) dopant : n-typ (xtra valnc lctrons ar addd) Silicon (Si) with Boron (B 2,3 ) dopant = p-typ (missing fourth valnc lctron, hols) 9

10 Qa. Adding Impuritis Adding impuritis to silicon in ordr to gnrat hols w ar building? matrial. A. N- typ B. P-Typ 10

11 Photon Hits th Atom of a Smi Matrial. Hol is th mpty spac lft bhind as a rsult of th movmnt of th fr lctron. Hols hav + charg. 11

12 Solar Cll Schmatic.. Protctiv Covr-Glass Antirflctiv Layr Elctrical Contact N P-N Junction P currnt Load Elctrical Contact Not to scal 12

13 Th Procss. Sunlight is mad of photons, small particls of nrgy. Ths photons ar absorbd by and pass through th matrial of a solar cll or solar PV panl. Th photons 'agitat' th lctrons found in th matrial of th photovoltaic cll. As thy bgin to mov (or ar dislodgd), ths ar 'routd' into a currnt. This, tchnically, is lctricity - th movmnt of lctrons along a path. 13

14 So, How dos it work? Light braks silicon bonds and crats fr lctrons and hols, missing lctrons Hols ar positiv chargs Built-in fild sparats lctrons and hols Stp 1. Photognration of charg carrirs, lctron (ngativ) and hol (positiv). Stp 2. Sparation of th charg carrirs through th mdium. R. Chang: Solar Cll Tchnology F07 14

15 Qc. Nam th junction that is cratd by doping adjacnt rgions of a smiconductor A n-typ B p-typ C Valnc junction D p-n junction E Silicon 15

16 Q - What is a Sris circuit? A On whr lctricity travls on on path. I=1.7 A V 1 =1.5 V 1 V 2 V 2 =1.5 V = V1 + V2 I = Constant P = (V 1 +V 2 ) (I)= ( ) (1.7) 16

17 Sris Connction: Solar Clls and Eq. Battris (I) (I 2 = I I 1 ) I 1 I 2 I=I 1 +I 2 V = Constant I 2 I 1 = 1.7 A I 2 = 1.7 A I = = 3.4 A. V 1 = V 2 = 1.5 V Powr =? 17

18 Qb. Givn th valus and th st up bllow, what is th total Powr gnratd? I I 1 = 1.0 A I 2 = 1.0 A V = 3.0 V I 1 I 2 V = 3.0 a. P = 3.0 W b. P = 4.0 W c. P= 5.0 W d. P= 6.0 W 18

19 Factors affcting Solar Cll Prformanc Light intnsity (typ of light) Light wavlngth (color of light) Angl of incidnt light Surfac condition of solar clls (clannss) Tmpratur on solar clls R. Chang: Solar Cll Tchnology F07 19

20 IV curv of a solar panl Thr ar thr st of curvs shown, for thr diffrnt sun light intnsitis. P. Hsu s Lctur Nots: lctrical powr sourcs 20

21 Masurmnts I + V _ POT A variabl rsistor (potntiomtr or POT) is usd in xprimntally dtrmining th V vs. I curv of a solar cll. Th sam procdur is usd in th wind turbin xprimnt. P. Hsu s Lctur Nots: lctrical powr sourcs 21

22 Stup in th lab V I W cll #1 cll #3 cll #5 cll #2 cll #4 cll #6 Powr mtr POT 22

23 Voltag Currnt Powr Loading condition Vary rsistanc from 0 to th full rsistanc of th POT. Tak down th voltag, currnt, and powr radings at a small rsistanc incrmnt 23

24 Rviw Qustion 1 A solar cll is dsignatd to captur nrgy from: A. Sunlight B. Whit light C. Incandscnt light D. Halogn light E. All of th abov 24

25 Rviw Qustion 2 A P-typ smiconductor is a? carrir? A. Photon B. Elctron C. Hol D. Ion E. Non of th abov 25

26 Rviw Qustion 3 Which of th following will impair a solar cll s prformanc? A. Thicknss of th cll B. A watr stain C. Shap of th cll D. All of th abov E. Non of th abov 26

27 27

http://www.wwnorton.com/chemistry/tutorials/ch14.htm Repulsive Force

ctivation nrgis http://www.wwnorton.com/chmistry/tutorials/ch14.htm (back to collision thory...) Potntial and Kintic nrgy during a collision + + ngativly chargd lctron cloud Rpulsiv Forc ngativly chargd