Iec ts 61724 3 2016

IEC TS 61 724 3 Edition 1 0 201 6 07 TECHNICAL SPECIFICATION Photovoltaic system performance – Part 3 Energy evaluation method IE C T S 6 1 7 2 4 3 2 0 1 6 0 7 (e n ) ® colour inside Copyright Interna[.]

IEC TS 61 724- 3

Edit io 1.0 2 16-0

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IEC TS 61 724- 3

Edit io 1.0 2 16-0

CONTENTS

FOREWORD 4

INTRODUCTION 6

1 Sco e 7

2 Normative ref eren es 8

3 Terms an def i ition 8

4 Test s o e, s hed le an d ration 1

5 Eq ipment an me s rements 11 6 Proced re 12 6.1 Overview 12 6.2 Calc lation an doc mentation of predicted energ an the method that wi b u ed to calc late the exp cted energ 14 6.2.1 General 14 6.2.2 Def i ition of test b u dary to al g with inten ed s stem b u dary 14 6.2.3 Def i ition of the mete rological inputs u ed for the prediction 15 6.2.4 Def i ition of the PV inputs u ed for the prediction 15 6.2.5 Def i ition of me s red data that wi b col ected d rin the test 16 6.2.6 Def i ition of the model calc lation 17 6.2.7 Predicted energ for the sp cif ied s stem an time p riod 18 6.2.8 Un ertainty defi ition 18 6.3 Me s rement of data 19 6.4 Identifi ation of data as ociated with u avai a i ty 19 6.5 Identifi ation of er one u data an re lacement or adju tment of s c data an pre aration of model input dataset 19 6.5.1 General 19 6.5.2 Data c ec s f or e c data stre m 2

6.5.3 Shadin of ir adian e sen or 2

6.5.4 Cal bration ac urac 21

6.5.5 Final c ec 21 6.5.6 Usin data from multiple sen ors 21

6.5.7 Substitution of b c -up data for er one u or mis in data 2

6.5.8 Out-of-ran e data or data that are k own to b in or ect 22 6.5.9 Mis in data 2

6.5.10 Partialy mis in data or p rtial u avai a i ty 2

6.5.1 Curtai ment b cau e of external req irement 23 6.5.12 In erter cl p in (con trained o eration) 2

6.5.13 Plan ed outage or f orce majeure 2

6.5.14 Grid s p ort events (e.g deviation f rom u ity p wer f actor) 2

6.6 Calc lation of exp cted energ 2

6.6.1 General 2

6.6.2 Me s re inputs 2

6.6.3 Ac e ta i ty of data 2

6.6.4 Time interval con isten y 2

6.6.5 Time stamp al g ment 2

6.6.6 Calc late exp cted energ d rin times of u avai a i ty 2

6.6.7 Calc late exp cted energ d rin times of avai a i ty 2

6.6.8 Calc late total exp cted energ 2

6.7 Calc lation of me s red energ 2

6.8 Calc lation of metric from me s red data 2

6.8.1 Calc lation of energ p rforman e in ex an avai a i ty 2

6.8.2 Calc lation of ca acity factor 2

6.8.3 Calc lation of p rforman e ratio 2

6.9 Un ertainty analy is 2

7 Test proced re doc mentation 27 8 Test re ort 2

An ex A (informative) Example calc lation – Calc lation for the energ p rf orman e in ices 2

Bibl ogra h 3

Fig re 1 – Sc ematic s owin relation hip of predicted, exp cted, an me s red energies to ref lect how the model is a pl ed con istently to historical an me s red we ther data 14 Ta le 1 – Example PV p rf orman e input p rameters to the model f or the initial prediction 15 Ta le 2 – Example ta le doc mentin the mete rological an other input p rameters to the model f or the calc lation of the exp cted energ 17 Ta le 3 − Example of data f ilterin criteria, to b adju ted ac ordin to local con ition 2

Ta le A.1 – Fictitiou data to demon trate calc lation 2

INTERNATIONAL ELECTROTECHNICAL COMMISSION

Part 3: Energy evaluation method

1 Th Intern tio al Ele trote h ic l Commis io (IEC) is a worldwid org niz tio for sta d rdiz tio c mprisin

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ex e tional circ mstan es, a tec nical commit e may pro ose the publ cation of a tec nical

sp cif i ation when

• the req ired s p ort can ot b o tained for the publ cation of an International Stan ard,

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• the s bject is sti u der tec nical develo ment or where, f or an other re son, there is the

f uture but no immediate p s ibi ty of an agre ment on an International Stan ard

Tec nical sp cif i ation are s bject to review within thre ye rs of publ cation to decide

whether they can b tran f ormed into International Stan ard

IEC TS 617 4-3, whic is a tec nical sp cif i ation, has b en pre ared by IEC tec nical

commit e 8 : Solar photovoltaic energ s stems

IEC 617 4-1, IEC T 617 4-2 an IEC TS 617 4-3 can el an re lace the f irst edition of

IEC 617 4, is ued in 19 8, an con titute a tec nical revision

The main tec nical c an es with regard to the first edition of IEC 617 4 (19 8) are as f ol ows:

– This f irst edition of IEC TS 617 4-3 provides a method f or q antif yin the an ual energ

generation for a PV plant relative to that exp cted f or the me s red we ther

The text of this tec nical sp cif i ation is b sed on the f olowin doc ments:

En uiry draft Re ort o v tin

Ful information on the votin for the a proval of this tec nical sp cif i ation can b fou d in

the re ort on votin in icated in the ab ve ta le

This publcation has b en draf ted in ac ordan e with the ISO/IEC Directives, Part 2

A l st of al p rts in the IEC 617 4 series, publ s ed u der the general title P hotov ltaic

s stem p rorma c , can b fou d on the IEC we site

The commit e has decided that the contents of this publ cation wi remain u c an ed u ti

the sta i ty date in icated on the IEC we site u der "htp:/we store.iec.c " in the data

related to the sp cifi publ cation At this date, the publ cation wi b

• tran formed into an International stan ard,

• recon rmed,

• with rawn,

• re laced by a revised edition, or

A bi n ual version of this publ cation may b is ued at a later date

IMPORTANT – The 'colour in ide' logo on the cov r pa e of this publ c tion indic te

that it contains colours whic are consid re to be u ef ul for the cor e t

understa ding of its conte ts Us rs s ould theref ore print this doc me t using a

colour printer

The p rf orman e of a PV s stem is de en ent on the we ther, se sonal ef fects, an other

intermitent is ues, so demon tratin that a PV s stem is p rformin as predicted req ires

determinin that the s stem fun tion cor ectly u der the ful ran e of con ition relevant to

the de loyment site IEC 6 4 6 des rib s a proced re f or en urin that the plant is

con tru ted cor ectly an p wered on pro erly by verifi ation throu h in remental tests, but

do s not atempt to verif y that the output of the plant me ts the desig sp cif i ation

IEC 617 4-1 defi es the p rforman e data that may b colected, but do s not def i e how to

analy e that data in comp rison to predicted p rf orman e IEC TS 617 4-2 an

ASTM E2 4 -1 des rib method for determinin the p wer output of a photovoltaic s stem,

an are inten ed to doc ment completion an s stem turn on, an re ort a s ort term p wer

ca acity me s rement of a PV s stem, but are not inten ed f or q antif yin p rf orman e over

al ran es of we ther or times of ye r IEC 6 6 0-2 also des rib s how to me s re the

energ f rom a CPV plant, but do s not des rib how to comp re the me s red energ with a

model

The method des rib d in this Tec nical Sp cif i ation is inten ed to ad res testin of a

sp cif i de loyed PV s stem over the f ul ran e of relevant o eratin con ition an for a

s stained time (general y a complete ye r) to verif y lon -term exp ctation of energ

prod ction to ca ture al typ s of p rf orman e is ues, in lu in not only resp n e to dif ferent

we ther con ition , but also outages or in tan es of red ced p rf orman e of the plant that

may arise from grid req irements, o erational set p ints, hardware f ai ure, p or maintenan e

proced res, plant degradation, or other pro lems The p rforman e of the s stem is

c aracterized b th by q antif yin the energ lost when the plant is not fun tionin

(u avaia le) an the extent to whic the p rf orman e me ts exp ctation when it is

fun tionin

Multiple asp cts of PV s stem p rforman e are de en ent on b th the we ther an the

s stem q al ty, so it is es ential to have a cle r u derstan in of the s stem b in tested For

example, the mod le temp rature is primari y a f un tion of ir adian e, ambient temp rature,

an win spe d; al of whic are we ther ef fects However, the mod le-mou tin

con g ration also af f ects the mod le temp rature, an the mou tin is an asp ct of the

s stem that is b in tested This tec nical sp cifi ation presents a b st-practice proces for

test develo ment an clarif ies how me s rement c oices can af fect the outcome of the test

so that u ers can b nef it f rom stre ml ned test desig with con istent def i ition , whi e sti

al owin f lexibi ty in the a pl cation of the test so as to ac ommodate as man u iq e

in tal ation as p s ible

IECRE’s An ual PV Project Performan e Certif i ate in orp rates me s rements f rom this

Tec nical Sp cif i ation Althou h this tec nical sp cif i ation al ows a pl cation in multiple

way , to maintain a con istent def i ition of the me nin of the IECRE certif i ate, when this

tec nical sp cif i ation is u ed f or me s rements f or IECRE re ortin , the method may be

req ired to u e a minimum level of ac urac f or the me s rements or other detai s as

doc mented by IECRE

PHOTOVOLTAIC SYSTEM PERFORMANCE –

Part 3: Energy evaluation method

This p rt of IEC 617 4, whic is a Tec nical Sp cif i ation, def i es a proced re for me s rin

an analy in the energ prod ction of a sp cif i photovoltaic s stem relative to exp cted

electrical energ prod ction f or the same s stem f rom actual we ther con ition as def i ed by

the stakeholders of the test The method f or predictin the electrical energ prod ction is

outside of the s o e of this tec nical sp cif i ation The energ prod ction is c aracterized

sp cif i al y for times when the s stem is o eratin (avai a le); times when the s stem is not

o eratin (u avai a le) are q antif ied as p rt of an avai a i ty metric

For b st res lts, this proced re s ould b u ed f or lon -term p rf orman e (electrical energ

prod ction) testin of photovoltaic s stems to evaluate s stained p rforman e of the s stem

over the entire ran e of o eratin con ition en ou tered throu h the d ration of the test

(prefera ly one ye r) Su h an evaluation provides eviden e that lon -term exp ctation of

s stem energ prod ction are ac urate an covers al en ironmental eff ects at the site In

ad ition, f or the ye r, u avai a i ty of the s stem (b cau e of either internal or external

cau es) is q antified, ena l n a ful as es ment of electricity prod ction

In this proced re, in erter o eration an other statu in icators of the s stem are f irst

analy ed to f i d out whether the s stem is o eratin Times when in erters (or other

comp nents) are not o eratin are c aracterized as times of u avai a i ty an the as ociated

energ los is q antified ac ordin to the exp cted energ prod ction d rin those times For

times when the s stem is o eratin , actual photovoltaic s stem energ prod ced is me s red

an comp red to the exp cted energ prod ction f or the o served en ironmental con ition ,

q antif yin the energ p rforman e in ex, as def i ed in IEC 617 4-1 As a b sis f or this

evaluation, exp ctation of energ prod ction are develo ed u in a model of the PV s stem

u der test that wi serve as the g arante or b sis f or the evaluation an is agre d up n by

al stakeholders of the project Typical y, the model is complex an in lu es ef fects of s adin

an varia le ef f icien y of the ar ay, but the model can also b as simple as a p rf orman e

ratio, whic may b more commonly u ed for smal s stems, s c as residential s stems

The proced re evaluates the q al ty of the PV s stem p rf orman e, ref lectin b th the q al ty

of the initial in tal ation an the q al ty of the on oin maintenan e an o eration of the plant,

with the as umption an exp ctation that the model u ed to predict p rforman e ac urately

des rib s the s stem p rforman e If the initial model is f ou d to b inac urate, the desig of

the s stem is c an ed, or it is desired to test the ac urac of an u k own model, the model

may b revised relative to one that was a pled e rl er, but the model s ould b fi ed

throu hout the completion of this proced re

The aim of this tec nical sp cif i ation is to defi e a proced re for comp rin the me s red

electrical energ with the exp cted electrical energ of the PV s stem The framework

proced re f oc ses on items s c as test d ration, data filterin method , data ac uisition,

an sen or c oice To reiterate, the proced re do s not pros rib a method f or generatin

prediction of exp cted electrical energ The prediction method an as umption u ed are

lef t to the u er of the test The en res lt is doc mentation of how the PV s stem p rformed

relative to the energ p rforman e predicted by the c osen model f or the me s red we ther;

this ratio is def i ed as the p rforman e in ex in IEC 617 4-1

This test proced re is inten ed for a pl cation to grid-con ected photovoltaic s stems that

in lu e at le st one in erter an the as ociated hardware

This proced re is not sp cif i aly writ en f or a pl cation to con entrator (> 3X) photovoltaic

(CPV) s stems, but may b a pl ed to CPV s stems by u in direct-normal ir adian e in te d

of glo al ir adian e

This test proced re was cre ted with a primary go l of f aci tatin the doc mentation of a

p rforman e g arante , but may also b u ed to verify ac urac of a model, trac

p rforman e (e.g degradation) of a s stem over the course of multiple ye rs, or to doc ment

s stem q al ty f or an other purp se The terminolog has not b en general zed to a ply to al

of these situation , but the u er is en ouraged to a ply this methodolog whenever the go l is

to verif y s stem p rforman e relative to modeled p rforman e Sp cif i g idan e is given for

providin the metric req ested for the IECRE certif i ation proces , providin a con istent

way f or s stem p rf orman e to b doc mented

The f olowin doc ments are ref er ed to in the text in s c a way that some or al of their

content con titutes req irements of this doc ment F r dated referen es, only the edition

cited a pl es For u dated referen es, the latest edition of the ref eren ed doc ment (in lu in

an amen ments) a pl es

IEC 617 4-1, P hotov ltaic s stem p rorma c – P art 1: Monitoring

1

IEC TS 618 6, Solar p otov ltaic e erg s stems – Terms definitio s a d s mb ls

ISO/IEC Guide 9 -1:2 0 , U nc rtainty of me s reme t – P art 1: I ntroductio to the

ex pre sio ofu c rtainty in me s reme t

ISO/IEC Guide 9 -3:2 0 , U nc rtainty of me s reme t – P art 3: Guide to the ex pre sio of

u c rtainty in me s reme t

ISO 5 2 (al p rts), Ac ura y (tru n s a d pre isio ) of me s reme t methods a d re ults

ISO 8 01:2 0 , Data eleme ts a d interc a g formats – Information interc a g –

Re re e tation of dates a d time

• IEC Electro edia: avai a le at ht p:/ www.electro edia.org/

• ISO Onl ne browsin platf orm: avai a le at htp:/ www.iso.org/o p

_ _ _ _ _

1

To b p bls e

e ergy a ai abi ity

metric of energ throu hput ca a i ty that q antif ies the exp cted energ when the s stem is

o eratin relative to the total exp cted energ

Note 1 to e try: Th e erg a aia i ty is c lc late fom th e erg u a aia i ty a d ma b e pre s d a a

p rc nta e or a fa tio

3.2

e ergy un v i abi ity

metric that q antif ies the energ lost when the s stem is not o eratin (as ju ged by an

automatic in ication of fun tional ty s c as the in erter statu f lag in icatin that the in erter

is actively con ertin DC to AC electricity or not The energ u avai a i ty is the ratio of the

exp cted energ (as calc lated from the original model an the me s red we ther data) that

can ot b del vered b cau e of in erters or other comp nents b in of f l ne divided by the

total exp cted energ f or the ye r

Note 1 to e try: Th e erg u a aia i ty ma b e pre s d a a p rc nta e or a fa tio En rg u a aia i ty

ma b c u e b is u s eith r intern l or e tern l to th PV s stem a d fin d b th s a plyin th te t

3.3

e ternal-c us -e clud d e ergy a ai abi ty

metric that q antif ies the exp cted energ when the s stem is o eratin relative to the total

exp cted energ d rin times when it was p s ible f or the plant to b o eratin

Note 1 to e try: Ex lu io s are ma e for time wh n th grid is n t o eratin or for oth r time wh n th pla t

wa n t o eratin for re s n o tsid of th c ntrol of th pla t

3.4

pre icte e ergy

energ generation of a PV s stem that is calc lated with a sp cif i p rforman e model, u in

historical we ther data that is con idered to b re resentative f or the site, where y the

sp cif i p rforman e model has b en agre d to by al stakeholders to the test (se Fig re 1)

Note 1 to e try: Th historic l we th r d ta ma b g th re fom a we th r statio th t is within re s n ble

pro imity to th site

3.5

energ generation of a PV s stem that is calc lated with the same sp cif i p rforman e

model as that u ed in the predicted energ model, u in actual we ther data col ected at the

site d rin o eration of the s stem for the ye r in q estion

Note 1 to e try: Th we th r d tais c le te lo aly at th site

Note 2 to e try: Th e p cte e erg is u e to c lc lateth e erg p rorma c in e

3.6

me s re e ergy

electric energ that is me s red to have b en generated by the PV s stem d rin the test

over the same d ration as the exp cted energ model

Note 1 to e try: Se als 3.13 te t b u d ry to d fin th lo atio of me s reme t

3.7

perf orma c inde

electricity generation of a PV s stem relative to exp cted, as def i ed in IEC 617 4-1 an

calc lated as des rib d in this tec nical sp cif i ation

3.8

e ergy perf orma c ind x

electricity generation of a PV s stem relative to the exp cted energ over a sp cif ied time

p riod, as def i ed in IEC 617 4-1 an calc lated in this tec nical sp cif i ation The energ

p rf orman e in ex may ref er to al times or only times of avai a i ty as def i ed by the al -in

energ p rf orman e in ex or the in-service energ performan e in ex, resp ctively

in-s rvic e ergy perf orma c in e

electricity generation of a PV s stem relative to the exp cted energ over a sp cif ied time

p riod d rin times when the s stem is fun tionin (ex lu in times when in erters or other

comp nents are detected to b of f l ne)

3.1

power perf orma c inde

electricity generation of a PV s stem relative to exp cted p wer prod ction f or a sp cif ied set

of con ition , as def i ed in IEC 617 4-1 an calc lated as in IEC TS 617 4-2

3.12

primary s nsor

sen or that has b en desig ated as the source of data f or the test Primary sen ors may b

desig ated for the ir adian e, temp rature, win sp ed or other me s rements The electrical

me s rements are defi ed as p rt of the s stem defi ition

3.13

te t bou dary

a (ph sical) dif ferentiation b twe n what is con idered to b p rt of the s stem u der test an

what is outside of the s stem for purp ses of q antif yin the p rforman e in ex

Note 1 to e try: Qu ntific tio of th e erg u a aia i ty ma b afe te b e e ts o tsid of th te t

b u d ry

3.14

sta e olders of th te t

in ivid als or comp nies that are a plyin the test

Note 1 to e try: Commo ly, th s p rtie ma b th PV c stomer a d th PV in taler, with th te t meth d

a ple to d f i e c mpletio of a c ntra t, b t th te t meth d ma b a ple in a v riety of situ tio s a d th

sta e old rs of th te t ma in s me c s s b a sin le in ivid al or c mp n

3.15

te t

test that comp res the me s red output of a PV s stem over a prolon ed time p riod to the

output that was exp cted f or the PV s stem for the me s red set of we ther con ition , as

def i ed by this tec nical sp cif i ation (se 3.4)

3.16

model

simulation model u ed to calc late b th predicted an exp cted PV generation f rom we ther

data The model is also u ed to calc late exp cted energ d rin times of u avai a i ty

Note 1 to e try: Ty ic ly, th mo el is e p cte to b th s me th t wa u e to d s rib th pla t b fore

c n tru tio , b t th mo el ma b u d te to refle t c a g s in th pla t d sig , or a y mo el ma b u e if th

g al is to te t th a c ra y of th mo el It is a s me th t th mo el is a pro riate for th situ tio

3.17

inv rter cl ppin

the in erter output is l mited by the ca a i ty of the in erter rather than by the input p wer

f rom the PV ar ay

4 Test scope, schedule and duration

This test may b a pled at one of several levels of gran larity of a PV plant The u ers of the

test s al agre up n the level(s) at whic the test wi b a pl ed The smalest level to whic

the test may b a pl ed is the smal est AC p wer generatin as embly ca a le of

in e en ent on-grid o eration

PV plant con tru tion is of ten divided into phases Phases may have se arate or s ared

intercon ection p ints an may b spre d over a p riod of month or even ye rs In general,

it is recommen ed that the test b a pl ed at the hig est level, that whic en omp s es the

entire PV project However, for very large plants s hed led f or intercon ection in p rts, with

the first an last intercon ection se arated by a p riod of more than 6 month It is

recommen ed that the test b a pl ed to smal er s bsets of the plant as they b come

avai a le f or intercon ection In s c cases, up n ful plant completion the test may b

a pl ed again in a way that en omp s es the entire plant, but in these cases the exp cted

energ is modif ied to in lu e exp cted plant p rforman e degradation in ac ordan e with the

model ac e ted by the stakeholders of the test

Some PV modules s ow me s ra le p rforman e c an es within hours or day of b in

in tal ed in the f ield, others do not The start of the test s ould b negotiated b twe n the

stakeholders u in the man f acturer’s g idan e for the n mb r of day or the ir adian e

exp s re ne ded f or the plant to re c the modeled p rforman e alon with the detai s of the

actual in tal ation an intercon ection dates An degradation as umption s ould b agre d

to by al stakeholders an doc mented as p rt of the model des ription

It is recommen ed that the test lasts 3 5 day The actual test term s ould b agre d up n in

ad an e If the test is not contin ed f or a ful ye r, se sonal variation (in lu in s adin ,

sp ctrum, temp rature, an win ) may cau e the p rforman e to deviate f rom what would b

o tained over a f ul ye r

The p rf orman e metric, in-service energ p rf orman e in ex, is re orted only f or times when

the in erters an other comp nents are on l ne Exp cted energ f or times when the in erters

or other comp nents are of f l ne is q antif ied in the energ u avai a i ty metric The energ

u avai a i ty metric may b further divided into situation with internal an external cau es,

as agre d to by the stakeholders

Al stakeholders agre on a detai ed test proced re b f ore the test commen es as des rib d

in Clau es 5 an 6

Usin the default test b u dary (u ed for simpl f ied dis u sion here), the we ther is

c aracterized by:

• Glo al horizontal ir adian e (direct an dif fuse may also b me s red)

• Ambient temp rature

• Rainf al or soi n (if the test agre ment as umes a cle n s stem)

If ad itional c aracterization of the we ther is req ired for implementation of the model, these

data s al b col ected in a man er con istent with the model If the model u es a dif ferent

test b u dary then the default test b u dary is modified For example, if plane-of -ar ay

ir adian e is sp cif ied as an input to the model, defi in the alb do to b outside of the test

b u dary, then the we ther is c aracterized by the plane-of -ar ay ir adian e rather than the

glo al horizontal ir adian e

Some models u e other inputs s c as atmospheric pres ure an h midity sin e these can

af f ect the in ident l g t sp ctrum an the PV p rforman e Where s it is en ouraged to

monitor man asp cts of the PV s stem o eration to b st u derstan the statu of the s stem

an o timize its p rforman e, the u e of data f rom the s stem as a c aracterization of the

we ther inputs to the model ris s compromisin the integrity of the test When data are u ed

f or s c c aracterization there is the ris that some asp cts of the s stem p rf orman e are

then con idered to b p rt of the u control ed we ther For example, if mod les are mou ted

without adeq ate venti ation, the temp rature of the s stem may in re se b yon the desig

value, red cin s stem output Simi arly, a trac ed s stem that do s not trac cor ectly wi

me s re a plane-of -ar ay ir adian e that is lower than what it would have b en with o timal

trac in Althou h f req ent rain an s ow wi af f ect s stem p rf orman e, the desig of the

s stem may aid in s ed in s ow an /or b in resistant to soi n

The s stem output is c aracterized by:

• Re l AC p wer del vered to the grid

• Ap arent AC p wer or AC p wer factor

The model simulatin the PV s stem p rf orman e s ould in lu e an as umption a out the

p wer f actor, whic may af f ect the predicted energ The recorded p wer factor (or an

simi ar input to the model) s ould b then u ed when calc latin the exp cted energ , as

des rib d b low

The def i ition of the AC energ , in lu in the p int of me s rement (s c as at a uti ty-grade

meter at the p int of intercon ection) is doc mented as p rt of the test b u dary def i ition If

p rasitic lo d outside the s stem b u dary exist (e.g trac ers an nig t-time electricity u e

by in erters an tran f ormers), the contract or test def i ition defi es whether adju tments are

made f or these, an , if so, these adju tments are c aracterized

Me s rement eq ipment an proced res f or al me s red p rameters are recommen ed to

conf orm to IEC 617 4-1, Clas A req irements However, a Clas B or Clas C evaluation

(p r the contract may also b completed an doc mented in the fi al re ort

Al detai s of data col ection (in lu in sen or n mb r, maintenan e, cal bration an cle nin )

fol ow IEC 617 4-1 ac ordin to the c osen Clas of me s rement with the ex e tion o

• The c oice of sen or an sen or p sitionin s al b con istent with the p rforman e

model that is b in u ed f or the test

NOT Ofte th f i al u c rtainty of th me s reme t is d min te b th u c rtainty of th ira ia c

me s reme t, s hig -a c ra y s n ors are d sire

• The f req en y of cle nin of ir adian e sen ors may vary by site an s ould b

doc mented

• Verif i ation of ac urate p sitionin of the sen ors is ac ompl s ed throu h comp rison of

data f rom a cle r day with model ed ir adian e f or a cle r day an the res lts in lu ed in

the doc mentation of the u certainty of the a plcation of the test

• When ir adian e sen ors are de loyed in the plane of the ar ay, the grou d alb do s ould

b me s red to demon trate con isten y with that as umed in the model an the res lts

in lu ed in the doc mentation of the u certainty of the a plcation of the test

• For Clas A tests, b cau e the ir adian e me s rement is so cru ial to the test, the

cal bration s ould b in e en ently verif ied either by u in sen ors cal brated at dif ferent

test location or at dif ferent times so as to prevent a s stematic bias to the cal bration

6 Procedure

6.1 Ov rview

The terms “predicted” an “exp cted” energ are def i ed in 3.4 an 3.5 to avoid ambig ity

on the me s red we ther data f or the time of interest The method u ed for calc latin the

“predicted” an “exp cted” energies are alg ed for con isten y If the historical an

me s red we ther data dif fer in their format, the a pl ed model may b inad ertently

c an ed Care s al b taken to ad res the dif feren es in the we ther data u ed f or the two

calc lation so that the model u ed f or calc latin the “predicted” energ is the same as the

model u ed f or calc latin the “exp cted” energ

The comp rison of me s red energ to exp cted energ is simplf ied by colectin the new

we ther data in the same format as the historical data In this case b th p rties agre up n

an doc ment data in an identical f ormat

The comp rison of the modeled an test res lts to evaluate the energ p rforman e in ex is

doc mented in detai in the fol owin s bclau es The folowin l st s mmarizes 6.2 to 6.9:

• Def i e test b u dary to al g with the inten ed s stem b u dary

• Calc late an doc ment the predicted energ u in the c osen model by l stin al inputs

in lu in historical we ther data, as umption regardin soi n , s adin , outages, etc

the raw data s ould b in lu ed in the f i al re ort as an a p n ix The predicted energ

may as ume 10 % avai a i ty or may b red ced to ac ou t f or exp cted times of

u avaia i ty

• Complete the me s rement of data f rom the o eratin s stem over the test p riod

• Identif y times when the s stem is u avaia le f or a variety of e son that may b external

or internal to the plant

• Evaluate the me s red data to identif y an doc ment anomal es that may req ire extra

tre tment Su h anomal es in lu e mis in or er one u data that are re laced

• Calc late an ag regate the exp cted energ for the f ul time p riod, re lacin mis in

data, as ne ded

• Ag regate the me s red energ , re lacin mis in data, as ne ded

• Comp re the exp cted an me s red energies f rom the plant to derive the energ

p rforman e in ex

• Compute the u certainty of the me s rement

Time of u a aia i ty are n t a dre s d in this fig re.

Fig re 1 – Sc ematic s owin relations ip of pre icte , e pe te ,

a d me s re e ergie to ref le t how the model is appl e consiste tly

to historic l a d me s re we ther data

6.2 Calc lation a d doc me tation of pre icte e erg a d the method that wi be

us d to c lc late the e pe te e erg

As s own in Fig re 1, the f irst ste in the proces , typical y, is to predict the p rf orman e of

the PV s stem b sed on historical we ther data u in a model that has b en agre d to by the

stakeholders The model is def i ed in terms of the model inputs, calc lation proces , an how

the me s red mete rological data wi b input into the model It is exp cted that the

information req ired p r this s bclau e (6.2) is doc mented b f ore the b gin in of the test;

althou h the f i al comp rison of exp cted an me s red energ do s not u e the predicted

energ directly, the predicted energ is u ual y req ired f or project plan in The model may

as ume 10 % avai a i ty or may sp cif y a predicted u avai a i ty as p rt of the prediction,

red cin the predicted energ f or the ye r ac ordin ly

6.2.2 Def inition of te t boundary to al gn with inte d d s stem boundary

This test method is inten ed to q antif y the p rf orman e of a s stem, but the res lt of the test

may de en on what is con idered to b p rt of the s stem The stakeholders of the test s al

• Asp cts of s stem desig that are b in tested s c as whether mod les are mou ted

ac ordin to the desig ( i t, azimuth, heig t, rac in desig ) al owin the exp cted

co l n an ca ture of s nl g t

• L cation an typ of al me s rement devices

• Asp cts of s stem o eration that are b in tested s c as whether the soi n level wi b

con idered as p rt of the test

NOT To fa i tate th d s riptio of th te t meth d, this d c me t d fin s a d fa lt te t b u d ry Glo al

h riz ntal ira ia c , ambie t temp rature, win s e d, a d a y oth r mete rolo ic l me s reme ts s c a

h midity a d atmo p eric pre s re le o tsid of this d fa lt te t b u d ry Al oth r a p cts of th s stem are

c n id re to b p rt of th PV s stem th t is u d r te t, in lu in th mo ule temp rature a d th pla e-ofar a

ira ia c Th p rtie to th te t ma d fin th te t b u d ry h we er th y wis ; th d fa lt te t b u d ry is

d fin d o ly a a to l to clarify th a plc tio of th te t meth d d s rib d in this d c me t a d a a e ample for

h w to d fin th te t b u d ry Wh n mo els in lu e th efe ts of rainf al it c n b u eful to als mo e rainfal

o tsid of th d fa lt te t b u d ry

6.2.3 Def inition of th meteorological inputs us d f or th pre iction

The sources of the glo al horizontal ir adian e, ambient temp rature, win sp ed, an an

other mete rological data s c as atmospheric pres ure an h midity are des rib d an the

raw data are in lu ed as an a p n ix in the f i al re ort It is exp cted that this wi b

doc mented as sp cifi aly as p s ible b f ore the test (e.g sen or typ , location, cle nin

an cal bration s hed les, an an ad itional relevant inf ormation) Refer to IEC 617 4-1 f or

(Clas A, B, or C)

6.2.4 Def inition of th PV inputs us d f or th pre iction

Ta le 1 s ows the inf ormation req ested a out e c input data typ This example ta le

def i es the inf ormation that is req ested a out e c p rameter Enou h inf ormation s ould

b given so that the prediction could b d pl cated

Table 1 – Ex mple PV perf orma c input parameters

to the model for the initial pre iction

Mo ule P

ax

at S C (or CS C) = 1 0 0 W/m

2

Mo ule p wer temp rature c eficie t

– No -mo ule (e.g in erter or re istiv ) lo s fa tors

– Op ratio s a d mainte a c a aia i ty a s mptio s

– Uti ty a aia i ty a d c rtaime t, oth r o ta e

– In erter clp in

– Sn w lo s s

Mo el d tais (a gle of in id n e, s rie re ista c , s e tral a d oth r p rameters)

Some factors may b con idered outside of the simulation to l Also, a simple model s c as

p rforman e ratio may b u ed, in whic case, this ta le b comes very simple