raising standards worldwide™ NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication Photovoltaic devices — Part 4 Reference solar devices — Procedures for est[.]
BS EN 60904-4:2009 BSI Standards Publication Photovoltaic devices — Part 4: Reference solar devices — Procedures for establishing calibration traceability NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW raising standards worldwide ™ BS EN 60904-4:2009 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 60904-4:2009 It is identical to IEC 60904-4:2009 The UK participation in its preparation was entrusted to Technical Committee GEL/82, Solar photovoltaic energy systems A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © BSI 201 ISBN 978 580 64261 ICS 27.1 60 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 201 Amendments issued since publication Amd No Date Text affected BS EN 60904-4:2009 EN 60904-4 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM November 2009 ICS 27.1 60 English version Photovoltaic devices Part 4: Reference solar devices Procedures for establishing calibration traceability (IEC 60904-4:2009) Dispositifs photovoltaïques Partie 4: Dispositifs solaires de rộfộrence Procộdures pour ộtablir la traỗabilitộ de l'étalonnage (CEI 60904-4:2009) Photovoltaische Einrichtungen Teil 4: Referenz-Solarelemente Verfahren zur Feststellung der Rückverfolgbarkeit der Kalibrierung (IEC 60904-4:2009) This European Standard was approved by CENELEC on 2009-09-01 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: Avenue Marnix 7, B - 000 Brussels © 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members Ref No EN 60904-4:2009 E BS EN 60904-4:2009 EN 60904-4:2009 -2- Foreword The text of document 82/533/CDV, future edition of IEC 60904-4, prepared by IEC TC 82, Solar photovoltaic energy systems, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60904-4 on 2009-09-01 The following dates were fixed: – latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 201 0-06-01 – latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 201 2-09-01 Annex ZA has been added by CENELEC Endorsement notice The text of the International Standard IEC 60904-4:2009 was approved by CENELEC as a European Standard without any modification In the official version, for Bibliography, the following notes have to be added for the standards indicated: IEC 60891 NOTE Harmonized as EN 60891 :1 994 (not modified) IEC 60904-1 NOTE Harmonized as EN 60904-1 :2006 (not modified) IEC 60904-3 NOTE Harmonized as EN 60904-3:2008 (not modified) IEC 60904-7 NOTE Harmonized as EN 60904-7:2009 (not modified) IEC 60904-8 NOTE Harmonized as EN 60904-8:1 998 (not modified) IEC 60904-9 NOTE Harmonized as EN 60904-9:2007 (not modified) IEC 61 836 NOTE Harmonized as CLC/TS 61 836:2009 (not modified) BS EN 60904-4:2009 EN 60904-4:2009 -3- Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies Publication Year Title EN/HD Year IEC 60904-2 -1 ) Photovoltaic devices Part 2: Requirements for reference solar devices EN 60904-2 2007 2) ISO/IEC 7025 -1 ) General requirements for the competence of EN ISO/IEC 7025 2005 2) testing and calibration laboratories ISO/IEC Guide 98-3 2008 Uncertainty of measurement Part 3: Guide to the expression of uncertainty in measurement (GUM:1 995) - ISO 9059 -1 ) Solar energy - Calibration of field pyrheliometers by comparison to a reference pyrheliometer - ISO 9846 -1 ) Solar energy - Calibration of a pyranometer using a pyrheliometer - 1) 2) Undated reference Valid edition at date of issue - BS EN 60904-4:2009 –2– 60904-4 © I EC: 2009 CON TENTS Scope an d obj ect N orm ati ve references Term s and d efi n i ti ons 5 Req uirem en ts for traceabl e calibration proced ures of PV reference sol ar d evices U ncertai nty an al ysis Cal i bration report Markin g Ann ex A (inform ati ve) Exam ples of val i d ated cal ibration proced ures Bibl i ograph y 24 Fi gu re – Schem atic of m ost com m on reference i nstrum en ts an d transfer m ethods used in the traceabi l ity chai ns for solar irrad i ance d etectors Fi gu re A – Block d iagram of differential spectral responsi vity cal i bration superim posi ng ch opped m onoch rom atic rad i ati on DE( l) an d DC bias rad iati on Eb Fi gu re A – Optical arrangem en t of d ifferen tial spectral responsi vity cal i brati on Fi gu re A – Sch em atic apparatus of th e sol ar sim u lator m ethod 21 Table – Exam pl es of reference instrum ents, used i n a traceabil i ty ch ain of tim e an d solar irrad i ance Tabl e A – Typical u ncertai nty com pon ents ( k = 2) of global su nl i g ht m eth od Tabl e A – Typical u ncertai nty com pon ents ( k = 2) of a differential spectral responsivity cal ibration Tabl e A – Exam pl e of u ncertai n ty com ponents ( k = 2) of a solar sim ul ator m eth od cali bration 21 Tabl e A – Typical uncertai nty com pon ents ( k = 2) of a sol ar sim ul ator m ethod calibrati on wh en WRR traceable cavi ty radiom eter is used 21 Tabl e A – Typical u ncertai nty com pon ents ( k = 2) of a d irect su n l igh t m ethod 23 BS EN 60904-4:2009 60904-4 © I EC: 2009 –5– PHOTOVOLTAIC DEVICES – Part 4: Reference solar devices – Procedures for establishing calibration traceability Scope and object This part of I EC 60904 sets th e requ irem ents for calibrati on proced ures in ten ded to establish th e traceabi l i ty of ph otovoltaic reference sol ar d evices to SI u n its as req u ired by I EC 60904-2 This stand ard appl ies to ph otovoltaic (PV) referen ce sol ar d evices th at are used to m easu re th e irrad i ance of natural or sim ulated su n li ght for th e purpose of q uan tifyin g the perform ance of PV d evices The use of a PV reference sol ar d evice is req u ired in th e appl icati on of I EC 60904-1 an d I EC 60904-3 This stan dard h as been written wi th sin gle j u ncti on PV reference sol ar devices i n m i nd , i n particu l ar crystal l i n e Sil icon H owever, th e m n part of th e stan dard is suffici entl y gen eral to i ncl u de other tech n ologi es The m eth ods d escri bed in An n ex A, h owever, are l im ited to sin gl e j unction tech n ol og ies Normative references The fol l owi ng referenced docum ents are i n d ispen sabl e for th e appl icati on of this d ocum ent For d ated references, on l y the ed i tion ci ted appli es For u n dated references, th e l atest edi tion of th e referenced d ocum en t (i nclu d i ng an y am end m ents) appli es I EC 60904-2, Ph otovo lta ic de vice s – Pa rt 2: Re quire m e n ts for re fe re n ce s o la r de vice s I SO/I EC 7025, G e n e l re quire m e n ts for th e co m p e te n ce of te stin g and ca lib tio n la b ora to rie s I SO 9059, So la r e n e rgy – Ca lib tion o f fie ld p yrh e lio m e te rs b y com p a ris on to a re fe re n ce p yrh e lio m e te r I SO 9846, So la r e n e rgy – Ca lib tio n of a p yra n om e te r us in g a p yrh e lio m e te r I SO/I EC Gu i de 98-3: 2008, Un ce rta in ty of m e a s ure m e n t – Pa rt 3: G uide to th e e xp re ssio n o f un ce rta in ty in m e a s ure m e n t (GUM: 995) Terms and definitions For the purposes of th is docum en t, the foll owing term s an d d efin itions appl y N OTE Th e d i fferent referen ce i nstrum en ts for th e traceabil i ty ch n of solar i rradi ance are defi n ed i n thi s Clau se Tabl e l ists and com pares them wi th th ose i n use for ti m e Fi gure sh ows sch em ati cal l y th e m ost com m on traceabil ity ch n s, based on th e m eth od s d escri bed i n An n ex A 3.1 primary standard a device, wh ich im plem ents ph ysical l y one of th e SI un i ts or d irectl y rel ated q u an titi es Th ey are usu al l y m ain tain ed by n ation al m etrol og y institu tes (N MI s) or si m ilar organ isati ons en trusted with m ain ten an ce of stand ards for ph ysical qu anti ti es Often referred to also just as th e « prim ary» , th e ph ysical im plem en tation is sel ected such th at lon g-term stabil ity, precisi on BS EN 60904-4:2009 –6– 60904-4 © I EC: 2009 an d repeatabi l i ty of m easurem ent of th e q uan ti ty i t represen ts are gu aran teed to th e m axim um extent possibl e by curren t tech nol og y N OTE The World Rad i om etri c Reference (WRR) as real i zed by th e Worl d Stand ard G rou p (WSG) of cavi ty rad i om eters i s the accepted pri m ary stand ard for th e m easurem ent of sol ar i rrad i ance secon dary stan d ard a d evice, wh ich by period ical com parison with a prim ary stan d ard, serves to m aintain conform ity to SI u n its at oth er places th an that of th e prim ary stand ard I t d oes n ot necessaril y use the sam e tech n ical pri nci pl es as the prim ary stan dard, but strives to ach ieve sim ilar l on gterm stabi l ity, precision and repeatabi l i ty N OTE Typi cal secon dary stand ard s for sol ar i rradi an ce are cavi ty radi om eters whi ch parti ci pate peri odi cal l y (norm al l y every years) i n th e I ntern ati onal Pyrh el i om eter Com pari son (I PC) wi th the WSG 3 pri m ary referen ce th e reference i nstrum en t wh ich a laboratory uses to cal i brate secon dary references I t is com pared at periodic i n tervals to a secon dary stan dard Often prim ary references can be realised at m uch lower costs th an second ary stan dards N OTE Typi cal l y a sol ar cel l i s u sed as a reference sol ar d evi ce for the m easurem ent of natural or si m ul ated sol ar i rradi an ce secon d ary referen ce th e m easurem en t device in use for dail y routi ne m easurem ents or to cal ibrate working references, cali brated at peri od ic i ntervals to a pri m ary reference N OTE The m ost com m on second ary referen ces for th e m easurem en t of n atu ral or si m u l ated sol ar i rradi an ce are sol ar cel l s and sol ar m odu l es traceabi li ty th e req u irem ent for an y PV reference solar d evice, to tie its cali brati on value to SI un its in an un broken an d d ocum en ted ch n of cal ibration tran sfers incl ud i n g stated u n certain ties N OTE Th e WRR h as been com pared twi ce to th e SI rad i om etri c scal e an d shown to be wi thi n th ei r m u tu al un certai n ty l evel s Therefore traceabi l i ty to WRR au tom ati cal l y provi d es traceabi l i ty to SI u ni ts H owever, the un certai nty of th e rati o WRR/SI u ni ts n eed s to be taken i nto accoun t Th e Worl d Rad i ati on Center (WRC) recom m end s a rectang u l ar u n certai n ty di stri buti on wi th 0, % h al f-wi d th A thi rd com pari son i s curren tl y un d erway an d sh oul d be publ i sh ed i n the fu tu re J Rom ero, N P Fox, C Fröh li ch m e tro lo gia 28 (1 991 ) 25-8 J Rom ero, N P Fox, C Fröhl i ch m e tro lo gia 32 (1 995/1 996) 523-4 BS EN 60904-4:2009 60904-4 © I EC: 2009 –7– Table – Examples of reference instruments, used in a traceability chain of time and solar irradiance Reference in strument Pri m ary stan dard Time Cesi um atom ic cl ock at N ati onal Metrol og y I nsti tute (N M I ) Solar irradian ce Group of cavi ty radi om eters sti tu ti n g th e Worl d Stan d ard Grou p (WSG) of the Worl d Rad i om etri c Reference (WRR) Cryogeni c trap d etector Stand ard l am p Second ary stand ard Cesi um atom i c cl ock on GPS (Gl obal Posi ti on i n g System ) satel l i tes Com m ercial l y avai l abl e cavity radi om eters com pared every years at the I ntern ati onal Pyrh eli om eter Com pari son (I PC) Stand ard detector cal i brated agai n st a trap d etector Spectrorad i om eter cal i brated agai n st a stan dard l am p Pri m ary reference Second ary reference GPS recei ver, set to sh ow ti m e Qu artz watch N orm al i n ci d en ce pyrh el i om eter (N I P) (I SO 9059) Referen ce sol ar devi ce (I EC 60904-2 an d I EC 60904-4) Pyranom eter (I SO 9846) Referen ce sol ar device (I EC 60904-2) Prim ary stan dard WSG Trap d etector Stan d ard lam p Stan d ard detector Spectrorad i om eter I PC Secon dary stan dard Absol ute rad iom eter I SO 9059 Prim ary reference Secon dary reference NIP I EC 60904-4 Reference solar d evice I SO 9846 I EC 60904-2 Pyran om eter Reference solar d evice IEC 858/09 N OTE Di rect traceabi l i ty of absol u te rad i om eters to SI rad i om etri c scal e m ay al so be avai l abl e Figure – Schematic of most common reference instruments and transfer methods used in the traceability chains for solar irradiance detectors Requirements for traceable calibration procedures of PV reference solar devices A traceabl e cali bration proced ure is necessary to transfer cal i brati on from a stan d ard or reference m easuri n g solar irrad i ance (such as cavity rad iom eter, pyrh el i om eter an d pyran om eter) to a PV reference solar d evice Th e req u irem ents for such proced ures are as fol l ows: BS EN 60904-4:2009 –8– 60904-4 © I EC: 2009 a) An y m easurem en t i nstru m ent req u ired and used i n th e transfer proced u re shal l be an instrum ent wi th an u n broken traceabi lity ch ain b) A d ocum ented uncertai nty an al ysis c) Docum ented repeatabil ity, such as m easurem ent resu lts of laboratory i ntercom parison , or docum en ts of laboratory qu ality trol d) I n h erent absol ute preci si on , gi ven by a lim ited n u m ber of i nterm ed i ate tran sfers N OTE N orm al l y the transfer wou l d be from a secon dary stand ard to a PV reference sol ar cel l consti tuti ng a pri m ary reference N OTE Th e transfer from on e referen ce sol ar d evi ce to an oth er i s covered by I EC 60904-2 Uncertainty analysis An u ncertai n ty estim ate accord i ng to M I SC U N CERT – ED (1 995-01 ) shal l be provi ded for each traceable cal i brati on procedure Th is estim ate sh all provi de in form ati on on the uncertai nty of th e cal i brati on proced ure an d q u an titati ve data on the foll owi n g uncertai nty factors for each instrum ent used i n perform in g the cal i bration proced ure I n particu lar: a) Com pon en t of uncertainty arisi ng from rand om effects (Type A) b) Com pon en t of uncertai nty arisi ng from system atic effects (Type B) N everth eless a full u ncertai nty anal ysis h as to be perform ed for th e im pl em entati on of th e cali brati on m ethod by a particu lar laboratory Calibration report The cal ibrati on report sh all conform to th e req u irem ents of I SO/I EC 7025 and shal l norm all y incl u de at l east th e foll owing inform ati on: a) ti tle (e g ”Cal ibration Certificate”); b) nam e an d ad dress of laboratory, an d location where th e tests an d/or calibrati ons were carried out, if d ifferent from the ad dress of the laboratory; c) un i q ue i d en tification of the report (such as serial num ber) an d of each page, the total num ber of pages an d the d ate of issue; d) nam e and ad dress of th e cli ent pl acin g the ord er; e) descripti on and u n am bi guous i d en tificati on of the item (s) tested or cal ibrated ; f) date of receipt of cali brati on i tem (s) and d ate(s) of perform ance of test or cali brati on , as appropriate; g) calibrati on resu lts incl u d i ng th e tem perature of the device at wh ich th e calibration was perform ed; h) reference to sam pli n g proced ures used by th e laboratory wh ere these are rel evant to the valid ity or appl icati on of the resu l ts; i) th e n am e(s), ti tle(s) and sign ature(s) or eq u i valent id entification of person(s) auth orisin g th e report; j) wh ere relevant, a statem en t to th e effect th at th e resu l ts relate on l y to th e item s tested or calibrated Marking The cali brated reference sol ar device sh al l be m arked wi th a serial n um ber or reference num ber an d the followi n g inform ation attach ed or provi d ed on an accom pan yi n g certificate: a) date of (actual or present) cali bration ; BS EN 60904-4:2009 – 12 – – 60904-4 © I EC: 2009 Winter el al : “Th e resul ts of th e Secon d World Photovoltaic Scale Recal ibrati on ”, Proc of th e 31 s t I EEE PVSC 3-7 J an u ary 2005, Orl an d o, Florid a, U SA, pp 01 -1 01 A.2 Global sunlight method The establ ishm ent of traceabi l ity is based on th e calibration usin g the Conti nu ous Sun-and Shad e M eth od as d escribed in I SO 9846 Th e reference solar cell to be cal ibrated is com pared un d er n atural sun l igh t with two reference rad iom eters, n am el y a pyrhel iom eter m easurin g d irect solar irrad iance an d a pyran om eter m easuri n g d iffuse solar irrad i ance by application of a tin uous sh ade d evice un d er n orm al in cid ence d iti ons Th e total solar irrad i ance is d eterm in ed by th e sum of direct irrad iance and diffuse in-plane irrad iance As a pyrhel i om eter, a secon d ary stan dard is used in th e form of an absol u te cavi ty radiom eter com pared at 5-year in tervals with the World Stand ard Grou p (WSG) establ ish in g the World Rad iom etric Reference (WRR) The cal ibration factor for th e ph otovoltaic reference cel l is determ in ed from the m easured sh ort circu i t curren t, scal ed to 000 W/m and corrected for spectral m ism atch (I EC 60904-7) based on th e m easured spectral irrad iance of th e gl obal sun l igh t and th e rel ative spectral response of the reference sol ar cel l to be cali brated U n der certain cond i ti ons th e sim pl ifi ed global su n li ght m eth od is appl icable Th e sh ort-circu it curren t of th e reference cell is scal ed to 000 W/m and th en plotted versus pressure corrected geom etric air m ass The cal ibration value is determ ined from a l in ear least sq uare fit at air m ass , A spectral m ism atch correction is n ot req ui red an d hence the m easurem ents of the spectral irrad iance of the sun l igh t an d th e spectral response are not necessary I n the sim pl ified versi on of th e gl obal sun lig ht m eth od n o expl ici t spectral m ism atch correction is perform ed and it is replaced by di tions wh ich shou l d ensure th at th e spectral irrad iance of th e natural su nli ght i s sufficientl y cl ose to th e d efin ed stan d ard spectral irrad iance (I EC 60904-3) th at the uncertain ty com pon en t is sm all er than qu oted in Table A Althou gh th is shou l d be ensured by th e d iti ons l isted i n th e d escription of th e m ethod below, it sh ou l d be expl icitl y verifi ed (preferenti all y by using th e global sun l i ght m ethod) After th is val idati on th e sim pl ifi ed version can be appl ied as long as th e bou nd ary d iti ons are th e sam e as d uri n g th e val i dation N OTE Th e veri fi cati on and val i dati on wi l l prod uce n um eri cal val ues for both m ethods I f th e ag reem ent between th ese n u m eri cal val u es i s wi th i n th e u ncertai n ty bud get of th e m ethods, th e si m pl i fi ed m eth od shal l be d eem ed vali dated N OTE Th e si m pl i fi ed proced ure gi ves accu rate resu l ts for d evi ces wi th a spectral respon se over a broad rang e of th e sol ar spectru m e g crystal l i n e si l i d evi ces Si gn i fi can t errors m ay be i ntrod uced for n arrow spectral response d evi ces A.2.1 Equipment a) A m oun tin g pl atform , wh ich can be ori en ted n orm al to th e su n with i n an accuracy of ± 0, 5° through ou t th e cal ibrati on ru n b) A cavity rad i om eter, traceabl e to WRR c) A pyranom eter, traceable to WRR d) A sh adin g d evice to provi de shad e to item c) The fiel d angle, viewi n g angl e and aperture angl e provid ed by th e shad e sh all com pensate the respecti ve d escri pti ve an gles of th e cavity rad iom eter of item b) e) A tem perature control l ed m oun tin g bl ock for the reference d evice u n d er test capabl e of m aintai n in g the cel l tem perature at (25 ± 2)° C through ou t al l cal ibrati on ru n s f) Traceable m eans to m easure the sh ort circu it curren t of th e sol ar cel l to an accuracy of ± 0, % or better g) Traceable m eans to m easure th e si gn al of th e pyran om eter to an accuracy of ± 0, % or better h) A spectrorad iom eter capabl e of m easuri n g th e spectral irrad i ance of the total i n-plane natural su n l igh t i n th e wavelen gth range of 350 – 500 nm (or l arger) N OTE N ot req ui red i n si m pl i fi ed versi on BS EN 60904-4:2009 60904-4 i) © I EC: 2009 – 13 – Apparatus to determ in e the rel ati ve spectral response of the reference sol ar cel l N OTE N ot req ui red i n si m pl i fi ed versi on j) Means to m easure th e sun ’s el evati on to a precision of ± 2° Al tern ativel y, th e elevation of th e su n d urin g the data sam pl in g can be taken from alm anacs or com pu ted , as long as th e precision req u irem ent is m et for th e i nstant of d ata sam pli ng Th e latter norm all y requ ires traceabl e m eans to m easure tim e for th e com pu tati on of air m ass N OTE Onl y req ui red i n si m pl i fi ed versi on k) A m anom eter to m easure the local air pressure P to an accuracy of ± 250 Pa or better N OTE Onl y req ui red i n si m pl i fi ed versi on A.2.2 Measurements A calibrati on accord in g to th is stan dard shal l be perform ed on l y on clear, sun n y d ays wi th n o visibl e cloud cover with in 30 d egrees of th e su n a) Determ ine th e relative spectral response of th e reference cell to be cali brated N OTE N ot req ui red i n si m pl i fi ed versi on b) Sel ect th e si te an d/or th e season of th e year to en sure th at the su n ’s el evati on reaches an an gl e du rin g th e course of th e day wh i ch correspon ds to AM , (41 , d egrees at P0 ) c) Mount th e cavity rad iom eter on th e su n-poi n ti ng d evice (item A a) Avai l able rad i om eters h ave their own el ectronic uni t wh ich shall be n ected to the i nstrum en t foll owing th e m an ufactu rer’s recom m endations Allow suffici ent tim e to stabil ise th e electron ic u n it d) Mou nt the reference solar cell to be cal ibrated copl an ar on the m ou nti ng platform , attach i ng it to th e m oun ting block an d m n tain th e cell tem perature at (25 ± 2) ° C e) Mou nt th e pyran om eter i nten ded to m easure d iffuse sol ar irrad iance copl anar on the m ountin g platform Ensu re th at with i n the field of view of th e pyran om eter n o refl ecti ve surfaces m ay influ ence th e m easurem en t resu l t Mount th e sh ad in g devi ce an d ensure th at th e sensi ti ve area of th e pyran om eter is pointed to the cen tre of the sh ad e f) Mou nt th e spectrorad iometer coplan ar on th e m ou nti ng platform N OTE N ot req ui red i n si m pl i fi ed versi on g) Take sim ul tan eous read i ngs accord i ng to the fol lowi n g steps: ) Ensure th e alignm en t of all i nstrum en ts wi th respect to th e su n an d th e proper ali gnm ent of the shad in g device 2) Ensure that the tem perature of the reference solar cel l is with i n th e l im its given in d) 3) Record Gd i r, th e d irect n orm al irrad i ance as in d icated by th e cavity rad iom eter 4) Record Gd i f, th e d iffuse i n-plane irrad iance as in d i cated by th e pyranom eter 5) Record IS C , the short circu it current of the reference solar cell to be calibrated 6) Record E( λ ), the spectral irrad iance of th e global natural su n l igh t N OTE N ot req ui red i n si m pl i fi ed versi on 7) Measure θ , the solar elevation an gl e, or al tern ati vel y, record th e h our, m inute an d secon d of th e d ata sam pl i ng an d calcu l ate the sun ’s el evation N OTE Onl y req ui red i n si m pl i fi ed versi on 8) Record P, th e local r pressure N OTE Onl y req ui red i n si m pl i fi ed versi on 9) Repeat Steps to several tim es N OTE N ot req ui red i n si m pl i fi ed versi on BS EN 60904-4:2009 – 14 – 60904-4 © I EC: 2009 0) Repeat steps to 5, and at least every m i n for several h ou rs before an d after solar n oon , span n ing th e ran ge of air m ass from below AM , to above AM 3, i n both tim e periods N OTE Onl y req ui red i n si m pl i fi ed versi on h) Repeat th e whol e m easu rem ent procedure on at l east two oth er d ays A.2.3 Data analysis For al l d ata poin ts taken, appl y in seq u ence the fol lowi ng steps: a) Rej ect d ata poi nts wh ere Gd i r G d i f or Isc deviate by m ore th an ± % wh en com pared to the previ ous d ata poi n t b) Calcu late th e total irrad i ance GT G di r Gdi f , = + c) Scale th e m easured short circu it current Isc of the reference sol ar cell to be cal ibrated to 000 W/m accord in g to Equati on A d) Correct for tem perature accord in g to Eq u ati on A N OTE Thi s i s n orm al l y n ot req u ired as th e tem peratu re i s m ain tai n ed as d escri bed i n A 2 d ) an d th e al l owed tem peratu re d evi ati on i s accou nted for i n th e un certai n ty bud get e) Correct for spectral m ism atch accordi n g to Eq u ati on A 3, wh ere spectral irrad i ance of the gl obal n atural sun l i gh t f) Calcu late th e calibration valu e accordin g to Eq u ati on A g) Average al l calibrati on val ues for one day to obtai n CV1 Em ( λ) is th e m easured h) Repeat steps a) to g) for the oth er d ays of m easurem ent ru ns to obtain CV2 , CV3 , CVn accord ingl y i) Determ ine the arithm etic average of al l n CVi valu es an al ysed accord in g to th e above steps wh ich yi el ds th e fin al calibration valu e for th e reference d evice: CV j) = ( CV1 + CV2 + + CVn ) / n (A 5) I n th e sim pl ifi ed version the steps e) to g) are repl aced as fol lows: ) Rej ect d ata points for wh ich the ratio Gdi f GT is either sm al ler th an 0, or l arger than 0, Also reject data poin ts wh ere GT is ou tsid e th e range 800 – 200 W/m / N OTE Th i s to en sure th at d ata u sed for th e anal ysi s are taken d u ri n g atm ospheri c di ti ons cl ose to th e stan dard reference spectrum 2) U si n g th e su n ’s elevation angl e and th e atm osph eric pressure, calcu l ate the r m ass (AM) at th e m om ent of measurem ent accord ing to: AM = P / ( P0 × sin( θ )) (A 6) 3) Rej ect al l d ata sam ples wh ere AM is larger th an 4) Plot th e val ue of Isc obtain ed after step d) versus th e air m ass val u e AM i of each correspond ing m easuremen t sam pl e 5) By usin g a l in ear l east-squ are tech ni q ue, calcu late th e slope ( m ) an d offset ( b ) of the best fit strai ght l in e of th e d ata set I n order to balance the fi t, al l sh ort circu it curren t read ings sh ou ld be averaged for AM bins of 0, 01 before perform ing the fit Both m orni ng an d aftern oon h ave to tribu te at l east 33 % of th e total n um ber of m easurem ent sam ples u sed for the Least-Sq u ares fit N OTE For a g ood strai g ht l i ne fi t, d ata poi n ts shal l be consi dered as m i n i m um The sm al l er th e u ncertain ty of th e proced ure, the m ore d ata poi n ts i n th e l east-sq uares fi t are cl ose to AM , N OTE I t i s perm i ssi bl e to u se on l y d ata from h al f a d ay H owever, i n th e fi n al average, at l east d ata from three di fferen t d ays wi th at l east two m orni n gs an d two aftern oon s h ave to be i n cl u d ed 6) Calcu late th e cal ibration valu e of th e reference device by th e form ula: CV1 = m × AM + b with AM = , (A 7) BS EN 60904-4:2009 60904-4 © I EC: 2009 – 15 – 7) Perform steps h) an d i) A Uncertainty estimates I n Table A , typi cal valu es of th e u ncertai nty com ponen ts for th e gl obal sun li gh t m ethod (left colum n) an d i ts sim pl ified version (righ t colum n) are listed , resu ltin g i n com bi ned expanded uncertai nties U95 (with coverage factor k = 2) of 0, % an d , % respectivel y Table A.1 – Typical u ncertainty compon ents ( k = 2) of gl obal su nl ight method U ncertainty in measurem ent of short circuit cu rren t 0, % U ncertai nty du e to un stable cel l temperature ( ± K) 0, % U ncertai nty of di rect i rradi ance 0, % U ncertai nty of di ffuse i rrad i an ce ,6 % U ncertai nty of total i rradian ce (80 % di rect and 20 % diffu se) 0, % U ncertai nties due to spectral m ismatch correcti on (I EC 60904-7) or spectral irradian ce deviations between test condi ti ons and the referen ce spectral irradi an ce of AM , (IEC 60904-3) 0, % 0, % Variation s of data on di fferen t days 0, % 0, % Com bined expanded un certai nty 0, % ,1 % A – – – – – – – References d ocuments K A Em ery, C R Osterwal d, L L Kazm erski, an d R E H art, (1 988c), Cali brati on of Prim ary Terrestri al Reference Cells When Com pared With Prim ary AM Reference Cells, Proceed ings of th e 8th PV Sol ar Energ y Conferen ce, Florence, pp 64-68 K A Em ery, C R Osterwal d, S Rum m el, D R M yers, T L Stoffel , an d D Waddi ng ton , “A Com parison of Ph otovoltaic Cali bration M eth ods, ” Proc 9th European Ph otovol taic Solar Energ y Conf , Frei burg, W Germ an y, Septem ber 25-29, 989, pp 648-651 K A Em ery, D Waddi ngton, S Rum m el, D R M yers, T L Stoffel, an d C R Osterwal d, “SERI Resu lts from the PEP 987 Sum m it Rou n d Robin an d a Com parison of Photovol taic Cal ibration M eth ods, ” SERI tech rep TR-21 3-3472, M arch 989 Gom ez, T, Garcia L, M artin ez G, "Groun d level sun l igh t cal ibration of space solar cel ls Tenerife 99 cam pai gn, " Proc 28th I EEE PVSC, 332-1 335, (2000) J M etzd orf, T Wittchen , K H eid l er, K Dehn e, R Shim okawa, F N agam in e, H Ossenbrink, L Fornarin i , C G ood bod y, M Davi es, K Em ery, an d R Deblasi o, “Th e Resu lts of th e PEP '87 Rou nd-Robin Cali brati on of Reference Cells an d Mod ules, - Fin al Report” PTB techn ical report PTB-Opt-31 , Braunsch wei g, G erm an y, N ovem ber 990, I SBN 3-89429-067-6 H M ü l lej ans, A I oann i des, R Ken n y, W Zaaim an, H A Ossenbri nk, E D Du n lop “Spectral m ism atch in cali brati on of photovol tai c reference d evices by gl obal sun li ght m ethod” Me a sure m e n t Scie n ce a n d Te ch n o lo gy (2005) 250-1 254 H Mü l l ej ans, W Zaaim an , E D Du nlop, H A Ossen bri nk “Cali brati on of ph otovoltaic reference cells by gl obal sun l igh t m eth od”, Me tro lo gia 42 (2005) 360-367 – H M ül l ejans, W Zaaiman , F Merl i, E D Dun lop, H A Ossen bri nk “Com parison of traceable cali bration m eth ods for prim ary photovoltaic reference cel ls” Progre ss in Ph o tovo lta ics (2005) 661 -671 – F C Treble an d K H Krebs, “Com parison of European Reference Sol ar Cell Cal ibrati ons”, Proc 5th I EEE PV Spec Conf , 981 , pp 205-21 R Whitaker, G Zerlau t, an d A Purn el l, “Experim ental dem onstrati on of th e efficacy of global versus direct beam use in ph otovol taic perform ance prediction of fl at plate ph otovoltaic m odu l es”, Proc 6th I EEE PVSC, pp 469-474, 982 – BS EN 60904-4:2009 – 16 – A 60904-4 © I EC: 2009 Differential spectral responsi vity calibration (DSR calibration) Traceabil ity is based on a cal ibration of spectral responsi vity based on stan dard d etectors d irectl y traceable to SI u n its The cali bration valu e is com puted from th e m easured absol u te spectral responsi vity of the reference cel l an d th e reference sol ar spectral irrad iance d istri bu tion The spectral responsivi ty cali bration is transferred from th e stan dard detector irrad iance level to th e solar irradiance l evel over m an y ord ers of m agn i tud e with n o restrictions to th e solar cell concern in g l ineari ty or spectral m atch A Equ ipment The fol lowi ng apparatus is req ui red (see Fi gures A an d A 2) a) a m on ochrom ator prod ucing ch opped spectral irrad iance of at least mWm –2 nm –1 with in th e wavelen gth range coverin g th e spectral responsi vity of the reference solar cell to be cali brated, with a traceabl e wavelen gth setti ng; b) lam p(s) with l ens or m irror entrance optics (recomm end ed are q u artz-h alogen lam p to cover wavelen gths above 400 nm ; and Xen on-arc l am ps for wavel en gths below 400 nm ); c) a bi as light source, m eetin g in spectral irrad i ance, u niform ity an d tem poral stability the req u irem ents of Cl ass CBA as d efi n ed in I EC 60904-9; d) a ch opped m onochrom atic beam , traceabl e in i ts wavelen gth cal i brati on , for the absol u te calibrati on at on e or m ore d iscrete wavel en gths The n on-u n iform ity sh all be sm aller than ± % with i n th e acti ve area of the device to be cal ibrated ; e) a m onitor ph otod iode l arge enou gh to m on itor th e rad iation power of the m onochrom atic beam of a) and d ); f) stan dard radi ati on d etector(s) with tem perature trol directl y traceable to SI un its These d etectors sh al l be of ph otod i odes with th e best avai l able l i nearity, u niform ity an d stabi li ty; g) adj ustable aperture (im aged onto the reference cell); h) m eans for m aintain in g th e tem perature of th e reference cel l at (25 ± 2)° C; i) m eans for m easurin g th e AC short-circui t currents of th e reference cell, th e stan dard detector(s) an d the m on i toring d etector, e g with a l ock-in am plifi er The variation of th e am plificati on factor of such am pl ifiers sh all be l ess th an 0, % over th e si gn al ran ges used Preferabl y th e sam e am plifier is used for th e reference cell an d th e stan d ard detector; j ) m eans for m easurin g the DC com pon ent of the reference cel l Ib as d efi ned i n step A f A Test procedu re a) Set an d m ain tai n th e tem perature of th e reference cel l to (25 ± 2) ° C b) Adjust the aperture u n til its im age coincid es with the acti ve area of th e reference cell withi n ± m m c) Mount th e stan dard detector in a position close to th e focus of th e m onochrom atic beam coll ecti ng th e whol e rad iati on power d) Cal ibrate the m on ochrom atic irrad iance source of A a (wi thout bias rad iation) with respect to its relative spectral irrad iance e) U se its ch opped m on ochrom atic beam to d eterm ine the ratio of the AC short-circuit curren ts of th e m onitor ph otod iode ( Δ Im on cal ) an d stan d ard d etector ( Δ Ist ) m easured sim ul tan eousl y at wavelength in tervals of not m ore th an nm over th e wh ole responsi vity ran ge f) Set th e wh ite bias i rrad iance Eb to th e d esired operati on al l evel (between Wm –2 an d 1 00 Wm –2 ) an d m easure the correspond in g DC short circu it curren t Ib = Isc ( Eb ) g) Measure th e relati ve spectral responsivity of th e reference cell by usi n g th e ch opped m onoch rom atic rad i ation of irrad i ance source A a) an d determ in ing the rati o of th e short-circuit curren ts of reference cell ( Δ Iref) an d m onitor photod iod e ( Δ Im on ) an d calcu late BS EN 60904-4:2009 60904-4 © I EC: 2009 – 17 – th e rel ati ve differen tial spectral responsivity s( λ , Ib ) rel of th e reference cell u nd er bi as irrad i ance Eb : s (λ Ib )rel = ΔΔIIref , mon ΔImon, cal ⋅ Sst ( λ ) ΔIst ⋅ (A 8) wh ere Sst ( λ ) = spectral responsi vity of the stand ard d etector at wavel en gth λ h) Repeat steps f) an d g) at or m ore d ifferen t bi as levels coveri n g at least th e range between Wm –2 and 1 00 Wm –2 , th us i nclu d in g a l i nearity test of relati ve spectral responsi vity i) With the bi as irrad iance set as i n step f) to a l ow level n ear to or at the m in im um as specified i n step h), m easure th e absolu te d ifferenti al spectral responsi vity of th e reference cel l at th e wavel engths of the narrowban d fil ter set an d th e DC short circu it curren t I0 = Isc ( E0 ) Th i s is don e by usin g th e ch opped an d fi ltered m onochrom atic rad iati on as d escribed in item A d) j) The absolu te d ifferen tial spectral responsivi ty s ( λ i , Io ) wi th i = , 2, is d eterm in ed by th e rati o of sh ort-circu i t curren t to irrad iance (as m easured by th e stan dard detector in th e worki n g plan e) with each fi lter i n turn A.3.3 Data analysis a) Calcu late th e rati o kI ( λ i ) = (relati ve spectral responsivity as determ in ed in A g)/(absolute spectral responsivity as d eterm ined i n A i ) for each of th e three wavelen gths λ , λ , λ u nd er the Eo irrad i ati on b) Com pu te th e absolu te differen tial spectral responsivi ties by scalin g th e rel ative responsi vity wi th the m ean valu e of th e ki d eterm in ed in step a): λ λ s ( , Ib ) = s ( , Ib ) rel * ( k1 + k2 + k3 )/3 (A 9) c) Com pu te the d ifferen tial responsivity s AM1 ( Ib ) u nd er irrad iation wi th Es ( λ ) for at l east d ifferent levels of bi as l ig ht d eterm ined by Ib : s AM1 ( Ib ) = ∫ s( λ , λ λ Ib ) ⋅ Es ( ) ⋅ d ESTC (A 0) with ESTC = ∫ Es ( λ )dλ = 000 Wm − (A 1 ) an d Ib = Isc ( Eb ) (A 2) d) The reference solar cel l can be consid ered to be lin ear, if th e variati on of s AM , ( Ib ) over ≥ successive sets of m easurem ents at d ifferen t bias li ght levels is l ess than ± 0, % I n th is case, take the m ean of s AM1 , ( Ib ) as the defin i ti ve responsivity un der STC and calcu l ate CV: CV = s AM1 ESTC (A 3) e) I f th e reference cel l is n on l inear, i t sh all not serve as transfer stan d ard for the scope of th is stan d ard A.3.4 Uncertainty estimate I n Table A 2, typi cal val u es of the u ncertai nty com ponen ts resu lti ng i n a com bi ned expanded uncertainty of U95 < % (wi th coverage factor k = 2) are summ arised BS EN 60904-4:2009 – 18 – 60904-4 © I EC: 2009 N OTE Th e d om i n an t com pon en t i n th e u n certai n ty i s th at from th e stan d ard d etector Th e un certai n ty qu oted is not easi l y ach i eved an d m i ght on l y be avai l abl e at som e nati onal m etrol og y i n stitu tes (N MI s) Table A.2 – Typical u ncertainty compon ents ( k = 2) of a differenti al spectral responsivity cal ibration < 0, % < 0, % < 0, % U n certai n ty of th e stan d ard detector(s) U n certai n ty d u e to n onl i n ear or narrow-ban d cel l s U n certai n ty d ue to u n stabl e cel l tem peratu re ( ± K) Transfer u n certai nti es d u e to Rel ati ve spectral respon si vi ty N ot appl i cabl e Absol u te spectral respon si vi ty at di screte wavel ength(s) < 0, % < 0, % Spectral m i sm atch between bi as rad i ati on and reference sol ar spectrum ; n on -u n i form i ty of bi as radi ati on ; non -un i form i ty of m onoch rom ati c rad i ati on; m i sm atch of cel l area an d i rrad i ated area (i m age of th e d i aphragm ); spectral ban d wi dth ( ≤ 20 n m ) of the m on ochrom ati c radi ati on ; n on l i n eari ty of th e am pl i fi ers