Gabatarwar Samfur

Inuwa na ɗaya daga cikin matsalolin da suka fi yawa a cikin shigarwar PV na ainihi.

Inuwar bishiya, sandunan wutar lantarki, ƙura, najasar tsuntsaye, dusar ƙanƙara, har ma da kusurwoyin hawa marasa daidaituwa na iya haifar da inuwa ɓangare. Inuwa ba kawai tana rage fitar da module ba, tana iya haifar da matsala mafi tsanani: wuraren zafi.

Kwanan nan BC cells hasken rana sun jawo hankali sosai a cikin rufin rufin da aka rarraba, PV baranda, da manyan modules. Babban dalili: Kwayoyin BC yawanci suna iya ɗaukar inuwa da kyau, kuma suna aiki a ƙananan zafin jiki a ƙarƙashin inuwa.

A SNEC, sau da yawa kuna ganin masu siyarwa suna inuwa wani ɓangare na tantanin halitta sannan su nuna juriyar inuwa na samfuran BC ta hanyar kallon yadda famfon ruwa zai iya fesa.

Don haka me yasa kwayoyin BC suke da wannan fa'ida? Menene ilimin kimiyyar lissafi a bayansa?

Bari mu gwada bayyana shi da harshe mai sauƙi.

Me yasa inuwa ke haifar da wuraren zafi?

Cells in a PV module are usually wired in series.

Da'irori na jere suna da mahimmin hali: wutar lantarki dole ta kasance iri ɗaya a ko'ina.

Wannan yana nufin cewa wutar lantarki ta dukan layin tana ƙayyade ta hanyar madauki na jere tare. Lokacin da kowane tantanin halitta ya sami cikakken haske, kowannensu yana samar da wutar lantarki kuma duk suna aiki daidai.

Amma idan tantanin halitta ɗaya ya sami inuwa, wutar lantarki da zai iya samarwa tana raguwa. Idan har yanzu layin yana buƙatar tura wutar lantarki mai girma ta ciki, wannan tantanin halitta mai inuwa na iya zama tilas ya koma baya ta hanyar sauran kwayoyin da ba su da inuwa. A wannan lokacin ya daina zama mai samarwa kuma ya zama abin da ke cinye wutar lantarki.

Don inuwa, tantin da ke cikin inuwa ba ta mutu gaba ɗaya ba. Sashen da ba a rufe ba har yanzu yana samar da wani ɗan ƙaramin wutar lantarki. Don haka abin da ya kamata ya bi ta hanyar rushewar baya, hanyar zubewa, ko hanyar kewayawa ba shine cikakken wutar layin ba, amma bambancin da ke tsakanin wutar layin da wutar da tantin zai iya samarwa.

Za mu iya kiran wannan bambancin da rashin daidaiton wutar lantarki:

Imismatch = Istring - Igenerate

Don haka ƙarfin zafi na hot-spot za a iya rubuta shi a takaice:

Photspot ≈ ∣Vrev∣ × Imismatch

wanda shine:

Photspot ≈ ∣Vrev∣ × (Istring - Igenerate)

Wannan dabara tana nuna wani muhimmin batu: a daidai wutar layin, idan wutar baya ta yi girma, to ƙarfin da tantin da ke cikin inuwa ke ƙonewa yana ƙaruwa, kuma hot-spot yana ƙara zafi.

Don haka wata mabuɗin yaƙi da hot-spots ita ce:

yadda za a rage wutar baya a kan tantin da ke cikin inuwa, kuma a baza zafin daidai.

Wannan shi ne ainihin inda BC cells suke haskakawa.

Yaya tantin BC ya bambanta da tantin yau da kullum a tsari?

Tantin siliki na yau da kullum yawanci suna da tsarin haɗin gaba da baya.

A taƙaice:

• gaba yana da ƙananan layuka da busbars, kuma haske yana shigowa daga gaba;

• halin yanzu, da zarar an samar da shi a cikin tantanin halitta, ana tattara shi ta hanyar lantarki na gaba da na baya.

Tantanin halitta BC, ma'ana Back Contact, yana da siffa guda ɗaya:

duka lantarki masu kyau da marasa kyau suna kan bayan tantanin halitta, kuma gaba ba shi da layukan grid na ƙarfe.

Wannan yana kawo fa'idodi kai tsaye guda biyu:

1. babu inuwar layin grid a gaba, don haka yanki mai karɓar haske ya fi girma;

2. lantarki na baya za a iya yin su interdigitated, don haka tattara halin yanzu ya fi daidaito.

Hoto 1 Tsarin tsarin tantanin halitta BC

Tushen: Calcabrini, A., Procel Moya, P., Huang, B., Kambhampati, V., Manganiello, P., Muttillo, M., Zeman, M., & Isabella, O. (2022). Low-breakdown-voltage solar cells for shading-tolerant photovoltaic modules. Cell Reports Physical Science, 3(12), 101155. https://doi.org/10.1016/j.xcrp.2022.101155

Bayan tantanin halitta BC yana da yawancin yankuna p da n masu haɗe-haɗe. Tsakanin waɗannan yankuna akwai gajerun PN junctions masu yawa da aka yi da ƙarfi. Daga ra'ayi na kewayawa, ba ya zama kamar babban diode guda ɗaya, amma kamar ƙananan diodes da yawa a layi daya. A ƙarƙashin juyar da baya, waɗannan PN junctions da aka rarraba za su iya samar da hanyar juyar da baya mafi daidaituwa.

A lokaci guda, saboda waɗannan PN junctions na baya gajeru ne kuma an yi su da ƙarfi a cikin gida, za su iya shiga rushewar juyar da baya a ƙaramin ƙarfin juyar da baya.

Tabbas, wannan ya dogara da takamaiman sigogin ƙira na BC cell.

Misali, ƙaramin tazarar da ke tsakanin yankunan p da n, mafi ƙarfin filin gida, kuma yawanci yana da sauƙi a sami ƙaramin ƙarfin juyawa baya. Amma hakan na iya haifar da musanya a cikin leakage da shunt resistance. Don haka juriyar inuwa ta tantanin BC ba lamba ce tsayayyiya ba, tana da alaƙa sosai da tsarin tantanin, ƙirar bayan fage, girman tazara, yawan doping, ingancin passivation, da tsarin masana'anta.

Me yasa BC modules ke rasa ƙarancin wuta bayan inuwa?

Lokacin da module ya sami inuwa a wani ɓangare, tantanin da ke cikin inuwa yana tura zuwa reverse bias ta hanyar string current. Yayin da inuwa ta yi muni, jimillar wutar lantarki na wannan ɓangaren string yana ci gaba da raguwa.

A cikin modules na gargajiya, ana haɗa bypass diode a layi daya a kan wani ɓangare na string. Bypass diode ba a kunna shi da controller ba. Na'urar ce mai passive. Ko tana gudana ya dogara ne kawai da wutar lantarki a kanta. Lokacin da jimillar wutar lantarki na wannan ɓangaren string ta zama mara kyau sosai, bypass diode yana samun forward-biased kuma yana kunna kansa.

Yanayin kunnawa ana iya rubuta shi kamar:

Vsubstring ≤ -Vf

Vsubstring shine jimillar wutar lantarki na ɓangaren string da bypass diode ke karewa;

Vf shine faɗuwar wutar lantarki ta gaba na bypass diode.

Ga wani ɓangaren string, ana iya fahimtar jimillar wutar lantarki a matsayin:

Vsubstring = ∑Vunshaded + ∑Vshaded

inda:

• ƙwayoyin da ba a inuwa ba har yanzu suna samar da ingantaccen ƙarfin lantarki;

• ƙwayoyin da aka inuwa suna juyawa-baya kuma suna samar da ƙarfin lantarki mara kyau.

Yanayin kunna bypass diode za a iya karanta shi kamar:

∣∑Vshaded∣ ≥ ∑Vunshaded + Vf

A wasu kalmomi:

jimlar ƙarfin lantarki na juyawa na ƙwayoyin da aka inuwa dole ne ya wuce jimlar ƙarfin lantarki na gaba na sauran ƙwayoyin da ba a inuwa ba, tare da faɗuwar kunna bypass diode, kafin bypass diode ya shiga.

Amfanin tsarin BC shine, kafin ma bypass diode na waje ya kunna, tsarin PN junction na baya na ƙwayar BC yana ba da wasu rarraba gudanarwa na juyawa. Wannan yana kama da zener diode da aka gina a cikin ƙwayar.

Ƙarƙashin juyawa-baya, tsarin PN junction na baya na ƙwayar BC na iya samar da rarraba gudanarwa na juyawa a ƙaramin ƙarfin lantarki, wanda ke iyakance yadda ƙarfin lantarki na juyawa zai iya hawa. Don haka a ƙarƙashin inuwa ɓangare, tare da bypass diode na waje bai kunna ba, tsarin BC na iya riƙe ƙarfin fitarwa mai girma.

Hoto 2 IV curve na tsarin lokacin da aka inuwa ƙwaya ɗaya.

Source: E. Özkalay, F. Valoti, M. Caccivio, A. Virtuani, G. Friesen, and C. Ballif, "The effect of partial shading on the reliability of photovoltaic modules in the built-environment," EPJ Photovoltaics, vol. 15, p. 7, Jan. 2024, doi: 10.1051/epjpv/2024001. Available: https://doi.org/10.1051/epjpv/2024001

Kyakkyawan juriyar inuwa baya nufin kariya daga inuwa

Akwai wani rashin fahimta gama gari da ke buƙatar sharewa.

Kwayoyin BC suna jure wa inuwa da kyau, amma wannan baya nufin inuwa ba ta da wani tasiri a kansu.

Kowane tantanin PV zai samar da ƙarancin wuta idan ya kasance a inuwa.

Idan yankin da ke cikin inuwa a cikin substring ɗaya ya yi yawa, ko kuma wasu sel suna cikin inuwa gaba ɗaya, to jimillar wutar lantarki ta baya na sel ɗin da ke inuwa na iya ƙetare jimillar wutar lantarki ta gaba na sauran sel ɗin da ba su cikin inuwa ba. A wannan lokacin, diode na waje yana kunnawa.

Da zarar diode na waje ya kunna, wutar lantarki tana kewaya wannan ɓangaren layin gaba ɗaya. Sel ɗin da ba su cikin inuwa a cikin wannan substring ana kewaye su tare da waɗanda ke cikin inuwa, kuma gudummawar su ga fitarwa tana raguwa sosai. Don haka idan yankin inuwa ya yi girma, fa'idar samar da wutar lantarki na BC ma tana raguwa.

Modul ɗin BC suna da fifiko a lokacin:

• sel ɗaya ko ƴan sel suna cikin inuwa kaɗan;

• yankin inuwa a cikin kowane substring yana ƙarami;

• inuwa tana da diagonal, mai kama da layi, ko kuma tartsatsi a cikin gida;

• diode na waje bai kunna gaba ɗaya ba.

Misali, inuwa mai diagonal daga sandar wutar lantarki na iya barin kowane substring da ƙaramin yanki mai inuwa. A wannan yanayin, BC module yawanci yana nuna mafi kyawun juriya ga inuwa.

Me yasa BC modules ke yin sanyi a wuraren zafi?

BC modules suna da ƙananan zafin hot-spot saboda dalilai biyu.

Na farko, reverse current ya fi yaduwa

A cikin sel na yau da kullun, rarraba reverse current sau da yawa ba daidai ba ne. Reverse breakdown yakan faru da farko a wuraren rauni na gida, kamar:

• wuraren lahani na gida;

• gefen sel;

• wuraren da ba a saba gani ba na metallization;

• microcracks ko wuraren da suka gurɓata;

• wuraren da ke da raunin passivation na gida.

Waɗannan wuraren suna aiki kamar maki masu rauni.

Da zarar reverse current ya tattara a kan waɗannan wuraren rauni, ƙarfin wutar lantarki na gida ya yi yawa sosai, zafin jiki ya tashi da sauri, kuma hot spot ya bayyana.

Kamar dumama abubuwa biyu da adadin zafi ɗaya:

• farantin ƙarfe gaba ɗaya;

• digon da yake da girman fil.

Na ƙarshe yana yin zafi da sauri, babu tambaya.

Don haka haɗarin tantanin halitta na yau da kullun a ƙarƙashin inuwa ba shine "zafi daidai a duk faɗin tantanin halitta" ba. zafi ne mai tsanani a wuri ɗaya.

A BC cell has many interdigitated PN junctions on the back. Reverse conduction can spread more easily across many regions instead of piling up on a few defect points.

Don haka rarraba halin yanzu na juyawa na tantanin BC ya fi daidaito, ƙarfin wutar lantarki na gida ya ragu, kuma zafin wuri mai zafi ma ya ragu.

Na biyu, ƙarfin wutar juyawa yana ƙasa

Kuna iya ganin ta daga tsarin ƙarfin wuri mai zafi:

Photspot ≈ ∣Vrev∣ × Imismatch

A daidai wannan rashin daidaituwa na halin yanzu, ƙarancin wutar lantarki na juyawa, ƙarancin ƙarfin zafi.

Shi ya sa ƙarancin wutar lantarki na juyawa na iya aiki a matsayin hanyar kariya a ƙarƙashin inuwa.

Ga misali mai sauƙi.

Ka ce halin yanzu na igiyar module shine 10A, kuma tantanin halitta ɗaya yana da inuwa sosai.

Idan tantanin halitta na yau da kullun ya kai wutar lantarki na juyawa na 15V bayan inuwa, ƙarfin da yake ƙonewa shine kusan:

P = 15V × 10A = 150W

Idan tantanin BC ya daure saboda tsarin bayansa kuma wutar lantarki na juyawa ya iyakance zuwa kusan 6V, ƙarfin da yake ƙonewa shine kusan:

P = 6V × 10A = 60W

Bambancin yana da ban mamaki.

Tabbas, ainihin zafin wuri mai zafi ya dogara da yankin da aka inuwa, zafin yanayi, saurin iska, rufin module, girman gilashi, ƙirar tantanin halitta, da hanyar gwaji, don haka ba za ku iya tantance shi da lamba ɗaya tsayayye ba.

Duk da haka, a wasu gwaje-gwaje na gaske da gogewar filin, modules na BC yawanci suna aiki da sanyi a wurare masu zafi fiye da na al'ada. Misali, wasu modules na BC na iya kiyaye zafin wuri mai zafi ƙasa da kusan 120 °C, yayin da sauran nau'ikan module na iya kaiwa 160 °C ko ma fiye.

Wasu ƙwayoyin BC na musamman suna samun wani abu kamar "ginannen diode bypass", suna saukar da zafin wuri mai zafi zuwa kusan 90 °C yayin da module na tunani ke kusa da 190 °C, wanda ke nuna wannan rarraba juzu'i na baya na iya rage zafin wuri mai zafi sosai.

Shin ƙananan reverse breakdown voltage koyaushe ya fi kyau?

Ba lallai ba.

Ƙarƙashin ƙarfin wutar lantarki na baya yana taimakawa rage zafin wuri mai zafi a ƙarƙashin inuwa, amma yana iya kawo musayar ƙira kuma.

Idan hanyar reverse conduction ba ta da kyau, tana iya ƙara yawan leakage da rage shunt resistance, wanda ke cutar da aikin samar da wutar lantarki na al'ada na tantanin halitta.

Don haka tantanin BC mai inganci yawanci yana buƙatar daidaita manufofi biyu:

1. a lokacin aiki na yau da kullun, kiyaye inganci mai girma, ƙarancin zubewa, da juriya mai girma;

2. a ƙarƙashin juzu'i na baya daga inuwa, samar da amintaccen juzu'i na baya mai rarraba a ƙarƙashin ƙaramin wutar lantarki.

Wannan kuma shine dalilin da yasa ƙwayoyin BC daban-daban suka bambanta a aikin inuwa.

Wasu ƙwayoyin BC suna karkata zuwa inganci, don haka suna iya warewa da ƙarfi kuma su ƙare da babban juzu'in karyewa. Wasu kuma suna karkata zuwa juriyar inuwa, don haka suna iya tsara ƙananan hanyoyin karyewa masu daidaituwa.

Don haka ba za ku iya cewa "dukkan ƙwayoyin BC suna jure wa inuwa iri ɗaya" ba. Magana mafi inganci ita ce:

ƙwayar BC da aka tsara da kyau na iya samun ƙananan hanyoyin karyewa masu daidaituwa ta hanyar tsarin PN junction ɗin da ke bayanta, wanda ke inganta juriyar inuwa da wuri mai zafi.

Taƙaitaccen fa'idodin ƙwayar BC

Haɗa su, fa'idodin ƙwayar BC a ƙarƙashin inuwa sun haɗa da:

• ƙarancin asarar wutar lantarki a ƙarƙashin ƙaramin inuwa, kafin diode ɗin waje ya kunna;

• ƙarancin yawan wutar lantarki a wuri;

• ƙarancin zafin wuri mai zafi;

• babban iyakar amincin tsarin hasken rana.

Menene wannan ke nufi ga aikace-aikacen module?

A aikace, sau da yawa ba za a iya guje wa inuwa gaba ɗaya ba.

Musamman a yanayin rarraba, kamar:

• rufin gidaje;

• rufin kasuwanci da masana'antu;

• hasken rana na baranda;

• BIPV;

• saka da yawa daga fuskoki daban-daban;

• wuraren da ke da gine-gine masu rikitarwa a kewaye.

A cikin waɗannan aikace-aikace, na'urori na iya samun inuwa a wani ɓangare.

Idan tantanin halitta ya fi jure wa inuwa kuma ya yi sanyi a wurare masu zafi, wannan yana nufin:

• Ingantacciyar amincin na'ura: ƙananan zafin hot-spot yana rage tsufa na encapsulant, lalacewar backsheet, damuwa na gilashin gida, da haɗarin lantarki.

• Ingantacciyar dogaro na dogon lokaci: zafin gida mai girma yana hanzarta tsufan kayan aiki. Mafi raunin wuri mai zafi, mafi kwanciyar hankali na tsarin a tsawon lokaci.

• Ƙarin sarrafa asarar samarwa: lokacin da inuwa ta ɓangare ba ta da makawa, na'urar BC na iya rage ɗan asarar wutar lantarki.

• Tsarin tsarin da ya fi dacewa

Tsarin BC sun fi dacewa da rufin hadaddun, wuraren shigarwa da aka rarraba, da yanayin inuwa da yawa.

Ƙarshe

Tantunan BC sun fi jure wa inuwa kuma suna yin sanyi a wurare masu zafi, ba don 'ba su shafa da inuwa' ba, amma saboda suna da fa'ida a tsari da halayen reverse-bias.

Tare da tantanin halitta na yau da kullun a ƙarƙashin inuwa, rushewar reverse na iya mayar da hankali kan wuraren lahani na gida, yana haifar da babban ƙarfin wutar lantarki na gida da babban zafin hot-spot.

Tsarin PN junction na baya na tantanin BC yana aiki kamar rarraba, ginannen reverse clamp. A ƙarƙashin inuwa, yana iya haifar da gudanarwa na reverse a ƙananan ƙarfin lantarki kuma ya baza wutar reverse daidai, wanda ke rage ƙarfin hot-spot da zafin hot-spot.

Amma ka tuna, ƙwayoyin BC ba su da cikakkiyar kariya daga inuwa. Lokacin da yankin da aka inuwa ya yi girma da yawa, ƙwayoyi da yawa suna cikin inuwa gaba ɗaya, kuma ƙarfin substring ya zama mara kyau sosai, har yanzu diode na waje yana kunna. A wannan lokacin, fitowar substring ɗin da aka kewaya tana raguwa sosai.

Don haka daidai:

Amfanin ƙwayar BC ba shine kawar da tasirin inuwa ba, shine sanya su zama masu iya sarrafawa. A ƙarƙashin inuwa ƙarami, yana iya rage asarar wutar lantarki; a ƙarƙashin inuwa mai nauyi, yana iya rage haɗarin hot-spot.

Wannan shine ainihin dalilin da yasa ƙwayoyin BC suke yin kyau a wuraren inuwa masu rikitarwa.

Ra'ayin Ooitech

Abin da ya ba mu mamaki a nan shine cewa fa'idar inuwa ta BC tana cikin matakin haɗin baya, ba a cikin wani abu na sihiri ba, wanda ke nufin layin module dole ne ya cika ƙa'idodi masu tsauri akan tsarin interdigitated don samun wannan ƙarancin, ko da juyawar karya. A kan layin samarwa mun ga wannan ilimin kimiyya yana faruwa a gwajin EL da hot-spot, inda rashin daidaituwa na baya yake nuna wuraren karya da yawa kafin module ya ga inuwa. Idan kana son irin wannan bincike na abin da ke faruwa tsakanin ƙwayar da module da aka gama, tashar mu ta YouTube a www.youtube.com/ooitech tana da ƙarin daga cikin masana'antun hasken rana na gaske.