IEC 60904-9:2020
(Main)Photovoltaic devices - Part 9: Classification of solar simulator characteristics
Photovoltaic devices - Part 9: Classification of solar simulator characteristics
IEC 60904-9:2020 is applicable for solar simulators used in PV test and calibration laboratories and in manufacturing lines of solar cells and PV modules. This document define classifications of solar simulators for use in indoor measurements of terrestrial photovoltaic devices. Solar simulators are classified as A+, A, B or C based on criteria of spectral distribution match, irradiance non-uniformity in the test plane and temporal instability of irradiance. This document provides the required methodologies for determining the classification of solar simulators in each of the categories. A solar simulator which does not meet the minimum requirements of class C cannot be classified according to this document. This document is used in combination with IEC TR 60904-14, which deals with best practice recommendations for production line measurements of single-junction PV module maximum power output and reporting at standard test conditions.
This third edition cancels and replaces the second edition issued in 2007. This edition includes the following significant technical changes with respect to the previous edition:
- Changed title;
- Added spectral match classification in an extended wavelength range;
- Introduction of new A+ class;
- Definition of additional parameters for spectral irradiance evaluation;
- Added apparatus sections for spectral irradiance measurement and spatial uniformity measurement;
- Revised procedure for spectral match classification (minimum 4 measurement locations);
- Revised measurement procedure for spatial uniformity of irradiance;
- Added informative Annex for sensitivity analysis of spectral mismatch error related to solar simulator spectral irradiance.
Dispositifs photovoltaïques - Partie 9: Classification des caractéristiques des simulateurs solaires
l'IEC 60904-9:2020 est applicable aux simulateurs solaires utilisés dans les laboratoires d’essai et d’étalonnage des dispositifs PV et dans les chaînes de fabrication des cellules solaires et des modules PV.. Le présent document définit les classifications des simulateurs solaires à utiliser dans les mesures en intérieur des dispositifs photovoltaïques terrestres.Les simulateurs solaires sont classés en catégorie A+, A, B ou C, sur la base de critères d’équilibre de répartition spectrale, de non-uniformité de l’éclairement énergétique dans le plan d’essai et d’instabilité temporelle de l’éclairement énergétique. Le présent document fournit les méthodologies exigées pour déterminer la classification des simulateurs solaires dans chacune des catégories. Un simulateur solaire qui ne satisfait pas aux exigences minimales de la classe C ne peut pas être classé conformément au présent document. Le présent document est utilisé conjointement avec l’IEC TR 60904-14, qui traite des recommandations en matière de meilleures pratiques pour les mesurages sur la chaîne de production de la puissance maximale de sortie des modules PV à jonction unique et des comptes rendus dans les conditions d’essai standard.
Cette troisième édition annule et remplace la deuxième édition parue en 2007 .Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- Modification du titre;
- Ajout d’une classification de l’égalisation spectrale dans une plage de longueurs d'onde étendue;
- Introduction d’une nouvelle classe A+;
- Définition de paramètres supplémentaires pour l’évaluation de l’éclairement énergétique spectrique;
- Ajout de sections d’appareils pour le mesurage de l’éclairement énergétique spectrique et le mesurage de l’uniformité spatiale;
- Révision de la procédure de classification de l’égalisation spectrale (au moins 4 emplacements de mesure);
- Révision de la procédure de mesure pour l’uniformité spatiale de l’éclairement énergétique;
- Ajout d’une annexe informative pour l’analyse de sensibilité de l’erreur de désadaptation des réponses spectrales liée à l’éclairement énergétique spectrique des simulateurs solaires.
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IEC 60904-9 ®
Edition 3.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Photovoltaic devices –
Part 9: Classification of solar simulator characteristics
Dispositifs photovoltaïques –
Partie 9: Classification des caractéristiques des simulateurs solaires
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IEC 60904-9 ®
Edition 3.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Photovoltaic devices –
Part 9: Classification of solar simulator characteristics
Dispositifs photovoltaïques –
Partie 9: Classification des caractéristiques des simulateurs solaires
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-8765-1
– 2 – IEC 60904-9:2020 © IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 Classification of solar simulator characteristics . 12
5 Measurement procedures . 13
5.1 Introductory remarks . 13
5.2 Spectral match . 13
5.2.1 General . 13
5.2.2 Apparatus . 13
5.2.3 Procedure . 14
5.2.4 Measurement uncertainty. 15
5.3 Non-uniformity of irradiance in the test plane . 16
5.3.1 General . 16
5.3.2 Apparatus . 16
5.3.3 Procedure . 17
5.3.4 Uncertainty of non-uniformity measurement . 19
5.4 Temporal instability of irradiance . 19
5.4.1 Solar simulators for I-V measurement . 19
5.4.2 Solar simulators for irradiance exposure . 21
5.4.3 Classification for temporal instability . 21
5.4.4 Uncertainty of temporal instability . 22
5.5 AM1.5 spectral coverage (SPC) . 22
5.6 AM1.5 spectral deviation (SPD) . 22
6 Name plate and data sheet . 22
Annex A (informative) Assessment of spectral mismatch error: Sensitivity to spectral
irradiance . 24
A.1 General . 24
A.2 Estimation of spectral mismatch-related uncertainty when the spectral
responsivities are known . 24
A.3 Sensitivity of spectral irradiance for spectral mismatch error when the
variation of spectral responsivities is not known . 25
A.4 Reporting . 28
Bibliography . 29
Figure 1 – Locations for spectral irradiance measurement of a rectangular test area
(left) and a circular test area (right) . 15
Figure 2 – Evaluation of STI for a long pulse solar simulator . 20
Figure 3 – Evaluation of STI for a short pulse solar simulator. 21
Figure A.1 – Virtual spectral responsivity with its dispersions and the modelling
parameters . 25
Figure A.2 – Reference SR curves for typical PV technologies . 27
Figure A.3 – Robustness of spectral irradiance regarding spectral mismatch error . 28
Table 1 – Global reference solar spectral irradiance distribution given in IEC 60904-3
contribution of wavelength intervals to total irradiance in the restricted wavelength
range 400 nm to 1 100 nm . 9
Table 2 – Global reference solar spectral irradiance distribution given in IEC 60904-3
contribution of wavelength intervals to total irradiance in the extended wavelength
range 300 nm to 1 200 nm . 10
Table 3 – Definition of solar simulator classifications . 12
Table A.1 – Reference SR curves for typical PV technologies . 26
– 4 – IEC 60904-9:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC DEVICES –
Part 9: Classification of solar simulator characteristics
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60904-9 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
This third edition cancels and replaces the second edition issued in 2007. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
• Changed title;
• Added spectral match classification in an extended wavelength range;
• Introduction of new A+ class;
• Definition of additional parameters for spectral irradiance evaluation;
• Added apparatus sections for spectral irradiance measurement and spatial uniformity
measurement;
• Revised procedure for spectral match classification (minimum 4 measurement locations);
• Revised measurement procedure for spatial uniformity of irradiance;
• Added informative Annex A for sensitivity analysis of spectral mismatch error related to
solar simulator spectral irradiance.
The text of this standard is based on the following documents:
FDIS Report on voting
82/1756/FDIS 82/1775/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60904 series, published under the general title Photovoltaic
devices, can be found on the IEC web site.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60904-9:2020 © IEC 2020
PHOTOVOLTAIC DEVICES –
Part 9: Classification of solar simulator characteristics
1 Scope
IEC standards for photovoltaic devices require the use of specific classes of solar simulators
deemed appropriate for specific tests. Solar simulators can be either used for performance
measurements of PV devices or endurance irradiation tests. This part of IEC 60904 provides
the definitions of and means for determining simulator classifications at the required
irradiance levels used for electrical stabilization and characterisation of PV devices.
This document is applicable for solar simulators used in PV test and calibration laboratories
and in manufacturing lines of solar cells and PV modules. The A+ category is primarily
intended for calibration laboratories and is not considered necessary for power measurements
in PV manufacturing and in qualification testing. Class A+ has been introduced because it
allows for reduction in the uncertainty of secondary reference device calibration, which is
usually performed in a calibration laboratory. Measurement uncertainty in PV production lines
will directly benefit from a lower uncertainty of calibration, because production line
measurements are performed using secondary reference devices.
In the case of PV performance measurements, using a solar simulator of a particular class
does not eliminate the need to quantify the influence of the simulator on the measurement by
making spectral mismatch corrections and analysing the influences of spatial non-uniformity
of irradiance in the test plane and temporal stability of irradiance on that measurement. Test
reports for PV devices tested with the simulator report the class of simulator used for the
measurement and the method used to quantify the simulator’s effect on the results.
The purpose of this document is to define classifications of solar simulators for use in indoor
measurements of terrestrial photovoltaic devices. Solar simulators are classified as A+, A, B
or C based on criteria of spectral distribution match, irradiance non-uniformity in the test
plane and temporal instability of irradiance. This document provides the required
methodologies for determining the classification of solar simulators in each of the categories.
A solar simulator which does not meet the minimum requirements of class C cannot be
classified according to this document.
For spectral match classification a new procedure has been added. This procedure addresses
the actual need for an extended wavelength range, which is arising from advances in solar
cell technology (such as increased spectral responsivity below 400 nm) as well as solar
simulator technology (use of component LEDs). The procedure of the second edition of this
standard is still valid, but is only applied if backward compatibility of classification for solar
simulators already in use and for solar simulators in production/sale is required. This
document is referred to by other IEC standards, in which class requirements are laid down for
the use of solar simulators. The solar simulator characteristics described in this document
are not used in isolation to imply any level of measurement confidence or measurement
uncertainty for a solar simulator application (for example, PV module power measurement).
Measurement uncertainties in each application depend on many factors, several of which are
outside the scope of this document:
• Characteristics of the solar simulator, possibly including characteristics not covered by this
document;
• Methods used to calibrate and operate the solar simulator;
• Characteristics of the device(s) under test (for example, size and spectral responsivity);
• Quantities measured from the device(s) under test, including equipment and methods
used for measurement;
• Possible corrections applied to measured quantities.
When applications require a certain solar simulator characteristic, it is preferable to specify a
numerical value rather than a letter classification (for example, “≤ 5 % non-uniformity of
irradiance” rather than “Class B non-uniformity of irradiance”). If not obvious from the
application, it should also be indicated how the required simulator characteristic correlates to
relevant measured quantities. Since PV module power measurement is one of the most
common applications for solar simulators, brief guidance on this application is given in
informative notes for each solar simulator characteristic described in this document. This
document is used in combination with IEC TR 60904-14, which deals with best practice
recommendations for production line measurements of single-junction PV module maximum
power output and reporting at standard test conditions. For output power characterization of
PV devices, IEC TR 60904-14 addresses the relevance of the letter grades (A+, A, B, C) for
measurement uncertainty.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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.
IEC 60904-1, Photovoltaic devices – Part 1: Measurement of photovoltaic current-voltage
characteristics
IEC 60904-3, Photovoltaic devices – Part 3: Measurement principles for terrestrial
photovoltaic (PV) solar devices with reference spectral irradiance data
IEC TR 60904-14:– , Photovoltaic devices – Part 14: Guidelines for production line
measurements of single junction PV module maximum power output and reporting at standard
test conditions
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 together
with the following, apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
solar simulator
equipment employing a light source with a spectral distribution similar to the natural sunlight
used to evaluate characteristics of PV devices
Note 1 to entry: Simulators usually consist of three main components:
a) light source(s) and associated power supply;
b) any optics and filters required to modify the output beam to meet the classification requirements; and
___________
Under preparation. Stage at the time of publication: 82/1748/DTR.
– 8 – IEC 60904-9:2020 © IEC 2020
c) the necessary controls to operate the simulator. If the system is used for maximum power determination of PV
modules, the I-V data acquisition system shall be additionally regarded as integral part. Solar simulators shall
be labelled by their mode of operation during a test cycle. These are steady state, single pulse, and multi-
pulse.
Note 2 to entry: Various types of solar simulators are commonly used to determine the current-voltage (I-V)
characteristics of PV devices as defined in IEC 60904-1. Generally, these work as single lamp systems where the
PV device is placed in the designated test area or multiple lamp systems, which are based on the superposition of
light cones. Examples include:
a) Pulsed single lamp or multilamp solar simulator operated in a dark room with typically several metres distance
between light source(s) and PV device. Internal reflections from walls may be suppressed by use of baffles.
b) Pulsed solar simulator operated in a casing or in tabletop configuration with typically less than 1 m distance
between light source(s) and PV device. Diffuser plates and reflectors may be used to achieve the specified
spatial uniformity of irradiance.
c) Steady state single lamp or multilamp solar simulator operated in a dark room with typically several metres
distance between light source(s) and PV device. Internal reflections from walls may be suppressed by use of
baffles.
d) LED based multilamp solar simulator operated with typically less than 1 m distance between light source(s)
and PV device.
Note 3 to entry: Pulsed solar simulators can be further subdivided into long pulse systems acquiring the total I-V
characteristic or a section of the I-V characteristic during one flash and systems acquiring one I-V data point per
flash. Several lamp types may be used in a multilamp solar simulator. These instruments are spectrally tuneable
instruments, which work with superposition of different spectral irradiances, emitted from various lamp types. If
available, in addition to the rating, the reported test data should be referred to for evaluation of the applicability of
the solar simulator for a specific use or testing purposes.
Note 4 to entry: Multilamp systems can be further subdivided into systems, where each lamp irradiates the total
test area, and systems, where a single lamp just irradiates a part of the test area.
Besides the light source, the lamp power supply and the optics, also the I-V data acquisition, the electronic load
and the operating software may be an integral part of the solar simulator. Requirements for the related
measurement technique are included in other parts of the IEC 60904 series.
3.2
test plane
plane intended to contain the device under test
3.3
designated test area
region of the test plane that is assessed for solar simulator classification
Note 1 to entry: If required, typical geometries can be specified. A specification related to a circular geometry is
also permitted.
3.4
data sampling time
time to take a single data set (irradiance, voltage, current). In the case of simultaneous
measurement, this is given by the characteristic of the A/D converter. In the case of
multiplexed systems the data sampling rate is the multiplexing rate.
Note 1 to entry: In the case of simultaneous measurement, the data sampling time is given by the characteristic of
the A/D converter. In the case of multiplexed systems the data sampling time is the multiplexing rate.
The data sampling time is used for evaluation of temporal stability.
EXAMPLE In the case of non-simultaneous measurement, a multiplexing time of 1 µs would give a sampling rate
of 1 Mega samples per second; the data sampling time would be 3 µs.
3.5
data acquisition time
time to take the entire or a part of the I-V curve of a PV device
Note 1 to entry: The data acquisition time depends on the number of I-V data points and a delay time that might
be adjustable.
Note 2 to entry: In the case of pulsed solar simulators the data acquisition time is related to the measurements
recorded during a single flash.
3.6
time for acquiring the I-V characteristic
time for acquiring the entire I-V characteristic of a PV device
Note 1 to entry: If the I-V characteristic of the PV device is measured in a single flash it is equal to the data
acquisition time.
Note 2 to entry: If the I-V characteristic of the PV device is measured through sectoring in different parts with
multiple flashes, it is the sum of data acquisition times for the single sectors of the IV characteristic.
3.7
spectral range
reference spectral distribution of sunlight at Air Mass 1,5 Global (AM1.5), defined in
IEC 60904-3. For simulator evaluation purposes two wavelength ranges are defined:
a) Restricted wavelength range (400 nm to 1 100 nm): This definition shall establish
backward compatibility to IEC 60904-9 Ed.2:2007. Spectral match evaluation is performed
in the 6 wavelength bands given in Table 1.
b) Extended wavelength range (300 nm to 1 200 nm): In accordance with Table 2 the total
wavelength range is divided into 6 wavelength bands, each contributing the same
percentage to the integrated irradiance.
3.8
spectral match
spectral match of a solar simulator defined by the deviation from AM1.5 reference spectral
irradiance as laid down in IEC 60904-3
Note 1 to entry: For six wavelength intervals of interest, the percentage of total irradiance is specified in Table 1
and Table 2. Table 1 shall be referenced if backward compatibility to the Edition 2 of this document is required.
Table 1 – Global reference solar spectral irradiance distribution
given in IEC 60904-3 contribution of wavelength intervals to total
irradiance in the restricted wavelength range 400 nm to 1 100 nm
Wavelength range Percentage of total irradiance Cumulative integrated
in the wavelength range irradiance
400 nm to 1 100 nm
nm % %
1 400 to 500 18,4 18,4
2 500 to 600 19,9 38,3
3 600 to 700 18,4 56,7
4 700 to 800 14,9 71,6
5 800 to 900 12,5 84,1
6 900 to 1 100 15,9 100,0
– 10 – IEC 60904-9:2020 © IEC 2020
Table 2 – Global reference solar spectral irradiance distribution given
in IEC 60904-3 contribution of wavelength intervals to total irradiance
in the extended wavelength range 300 nm to 1 200 nm
Wavelength range Percentage of total irradiance Cumulative integrated
in the wavelength range irradiance
300 nm to 1 200 nm
nm % %
1 300 to 470 16,61 16,61
2 470 to 561 16,74 33,35
3 561 to 657 16,67 50,02
4 657 to 772 16,63 66,65
5 772 to 919 16,66 83,31
6 919 to 1 200 16,69 100,00
Note 2 to entry: It is generally recognized that this classification does not allow for prediction of PV module power
measurement uncertainties. The methods of IEC 60904-7 and this document’s Annex A should be used to
understand and potentially correct for spectral mismatch errors.
3.9
spatial non-uniformity of irradiance in the test plane
𝑢𝑢𝑚𝑚𝑚𝑚.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖 −𝑢𝑢𝑢𝑢𝑁𝑁.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖
𝑁𝑁𝑁𝑁𝑁𝑁−𝑢𝑢𝑁𝑁𝑢𝑢𝑢𝑢𝑁𝑁𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢 (%) =� �∙ 100% (1)
𝑢𝑢𝑚𝑚𝑚𝑚.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖 +𝑢𝑢𝑢𝑢𝑁𝑁.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖
where the maximum and minimum irradiance are those measured with the detector(s) over the
designated test area.
Note 1 to entry: Often, a wide range of values for non-uniformity of irradiance can produce errors < 1 % in PV
module power measurements, though this should be analysed on a case-by-case basis. Various publications on
this topic are given in the bibliography.
3.10
temporal instability of irradiance
𝑢𝑢𝑚𝑚𝑚𝑚.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖 −𝑢𝑢𝑢𝑢𝑁𝑁.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖
𝑇𝑇𝑖𝑖𝑢𝑢𝑇𝑇𝑁𝑁𝑢𝑢𝑚𝑚𝑇𝑇 𝑢𝑢𝑁𝑁𝑖𝑖𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑇𝑇𝑢𝑢𝑢𝑢𝑢𝑢 =� �∙ 100% (2)
𝑢𝑢𝑚𝑚𝑚𝑚.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖 +𝑢𝑢𝑢𝑢𝑁𝑁.𝑢𝑢𝑢𝑢𝑢𝑢𝑚𝑚𝑖𝑖𝑢𝑢𝑚𝑚𝑁𝑁𝑖𝑖𝑖𝑖
where the maximum and minimum irradiance are those measured within the relevant time
interval.
Note 1 to entry: Temporal instability is defined by two relevant time intervals:
a) Short term instability (STI)
This relates to the data sampling time of a data set (irradiance, current, voltage) during an I-V measurement.
This value of temporal instability may be different between data sets on the I-V curve. In that case the short
term instability is determined by the worst case.
For batch testing of cells or modules with no irradiance monitoring during I-V measurement the STI is
irrelevant and LTI related to the time period between irradiance determinations shall be used for classification.
b) Long term instability (LTI)
This is related to the time period of interest. Three cases can be distinguished:
– For a three channel I-V measurement (irradiance, current, voltage) with a pulsed or steady-state solar
simulator, the LTI value is the time for acquiring the I-V characteristic.
– For a two channel I-V measurement (voltage, current) with a pulsed or steady-state solar simulator,
irradiance shall be measured before and after I-V measurement. The LTI value shall be calculated from
these two irradiance values. The LTI value may depend on the I-V data acquisition time and the stability of
the light source. The maximum averaging interval for irradiance shall correspond to the time interval
between I-V data points.
– For irradiation exposure LTI shall be verified for the specifications (time period, data recording interval for
irradiance) given by the supplier. If such information is not available LTI shall be related to at least 100
irradiance values, with a minimum of one data point per hour, taken at equal intervals over the exposure
period.
Note 2 to entry: Irradiance corrections, such as those of IEC 60891, are often used to minimize the effects of
irradiance fluctuations on PV module output power measurements. The uncertainty related to irradiance correction
will depend on the difference “measured irradiance –target irradiance” and the precision of relevant I-V correction
parameters of the PV device. For other applications, the use of such corrections should be considered together
with requirements for solar simulator temporal instability.
3.11
solar simulator classification
a solar simulator may be one of four classes (A+, A, B, or C) for each of the three categories
– spectral match, spatial non-uniformity and temporal instability. Each simulator is rated with
three letters in order of spectral match, non-uniformity of irradiance in the test plane and
temporal instability of irradiance.
EXAMPLE: CBA, meaning a class C spectral match, a class B spatial non-uniformity and a class A temporal
instability.
Note 1 to entry: The solar simulator classification should be periodically checked in order to prove that
classification is maintained. For example spectral irradiance may change with operation time of the used lamp, or
uniformity of irradiance may be influenced by the reflection conditions in the test chamber.
3.12
AM1.5 spectral coverage
SPC
the SPC parameter identifies wavelength ranges, where solar simulator spectral irradiance is
larger than 10 % of AM1.5 reference spectral irradiance as laid down in IEC 60904-3. For all
data points fulfilling this condition the corresponding AM1.5 reference spectral irradiance is
integrated. SPC is the ratio of the resulting value and the total AM1.5 solar irradiance in the
range 300 nm to 1 200 nm.
1200 𝑛𝑛𝑛𝑛
(3)
𝑆𝑆𝑆𝑆𝑆𝑆 = � � 𝐸𝐸 (𝜆𝜆)∙ 𝛥𝛥𝜆𝜆� � 𝐸𝐸 (𝜆𝜆)∙𝛥𝛥𝜆𝜆�∙ 100%
𝐴𝐴𝐴𝐴1.5 𝐴𝐴𝐴𝐴1.5
𝐸𝐸 (𝜆𝜆)>0.1∗𝐸𝐸 (𝜆𝜆) 300 𝑛𝑛𝑛𝑛
𝑆𝑆𝑆𝑆𝑆𝑆 𝐴𝐴𝑆𝑆1.5
Note 1 to entry: A high value of SPC is in principle more desirable than a low value of SPC. In this document no
requirements for this parameter will be defined.
Note 2 to entry: No specific guidance can be given at this time regarding its use for assessing PV module output
power measurement uncertainties.
3.13
AM1.5 spectral deviation
SPD
within the wavelength ranges defined in Table 2, spectral irradiance values may be higher or
lower than AM1.5 reference spectral irradiance as laid down in IEC 60904-3. These deviations
are not detected by spectral match. The SPD parameter represents the summed deviation
between both curves and indicates how well the solar simulator spectral irradiance matches
with AM1.5 spectral irradiance:
1200 𝑛𝑛𝑛𝑛 1200 𝑛𝑛𝑛𝑛
(4)
𝑆𝑆𝑆𝑆𝑆𝑆 = � |𝐸𝐸 (𝜆𝜆)−𝐸𝐸 (𝜆𝜆)|∙𝛥𝛥𝜆𝜆� � 𝐸𝐸 (𝜆𝜆)∙𝛥𝛥𝜆𝜆 ∙ 100%
𝑆𝑆𝑆𝑆𝐴𝐴 𝐴𝐴𝐴𝐴1.5 𝐴𝐴𝐴𝐴1.5
300𝑛𝑛𝑛𝑛 300 𝑛𝑛𝑛𝑛
– 12 – IEC 60904-9:2020 © IEC 2020
Note 1 to entry: A low value of SPD is in principle more desirable than a high value of SPD. Values for SPD may
exceed 100 %. In this document no requirements for this parameter are defined.
Note 2 to entry: The parameter SPD is also used for characterizing light sources in non-photovoltaic applications
(EN 13032-1). No specific guidance can be given at this time regarding its use for assessing PV module power
measurement uncertainties.
4 Classification of solar simulator characteristics
Table 3 gives the performance requirements for the three characteristics spectral match, non-
uniformity of irradiance and temporal instability of irradiance.
For the spectral match, all six intervals shown in Table 1 or Table 2 shall agree with the ratios
in Table 3 to obtain the respective classes.
– Spectral irradiance of solar simulators shall be evaluated in the extended wavelength
range according to Table 2.
– Solar simulators in use and solar simulators in production/sale that have been classified
under Edition 2 of this document make an exception. Spectral irradiance of these can be
re-evaluated according to the same method (that of Edition 2) in the restricted wavelength
range. For that purpose Table 1 shall be referenced. This exception shall ensure the
backward compatibility, if required.
– If a significant change of PV technology occurred in the production of PV devices, the
customer is encouraged to perform spectral classification in the extended wavelength
range and use Table 2 to re-evaluate the simulator. In addition the sensitivity analysis for
spectral mismatch uncertainty as of Annex A shall be applied.
– The method used for the spectral classification renewal (restricted or extended wavelength
range) should be clearly stated in the report.
Refer to Clause 5 for procedures to measure and calculate the three characteristics of the
simulator (spectral match, non-uniformity of irradiance and temporal instability of irradiance).
In addition the parameters SPC and SPD shall be calculated. These results for SPC and SPD
are informative.
If stated by the manufacturer a number of flashes or on-time to stabilize irradiance should be
done prior to the classification.
These requirements apply to both steady state and pulsed solar simulators.
Table 3 – Definition of solar simulator classifications
Temporal instability
Spatial non- Short term Long term
Spectral match to all
uniformity of
instability of instability of
Classifications intervals specified in
irradiance irradiance irradiance
Table 1 or Table 2
% STI LTI
% %
A+ 0,875 to 1,125 1 0,25 1
A 0,75 to 1,25 2 0,5 2
B 0,6 to 1,4 5 2 5
C 0,4 to 2,0 10 10 10
Class A+ is only defined for the three solar simulator characteristics, if spectral match
evaluation is performed in the extended wavelength range according to Table 2.
NOTE Spatial non-uniformity of irradiance corresponding to Class A+ is consistent with the requirements specified
in IEC 60904-2 for calibration of reference devices using simulated sunlight.
If spectral match evaluation is performed in the restricted wavelength range according to
Table 1, only the classifications A, B and C are permitted for each solar simulator
characteristic (backward compatibility to previous Edition of this document).
Practical examples for different applications of solar simulators are given in IEC TR 60904-14.
5 Measurement procedures
5.1 Introductory remarks
It is the intent of this document to provide guidance on the required solar simulator
performance data to be taken, and the required locations in the designated test area for these
data to be taken. It is not the intent of this document to define the possible methods to
determine the simulator spectrum or the irradiance at any location on the test plane. It is the
responsibility of the simulator manufacturer or test laboratory to provide information upon
request for test methods used in the determination of the performance in each classification.
The classification of a solar simulator does not provide full information about sources of
measurement uncertainty that are related to PV performance measurements obtained with a
classified solar simulator. Such uncertainties are dependent on the actual measurement
devices and procedures used and need to be evaluated.
In general, the classification of solar simulators will depend on a number of factors. Also most
simulators can be operated at different working points (for example different irradiances). In
this case, the classification is only valid for the conditions similar to those during classification
assessment. If the intended use of the solar simulator includes a change of irradiance levels,
classification shall be performed and reported at these irradiance levels ± 50 W/m .
Classification of a solar simulator is not constant but subject to various factors:
– Ageing of lamp with operation time.
– Exchange of lamp(s.)
– Lamp power setting.
– Use of any inserts in the beam of light such as optical filters or (light reducing) masks or
meshes.
– Ageing or soiling of any inserts.
– Reflections from the surroundings such as properties of dark room walls.
– Pulse duration, if applicable.
Accordingly, classification only refers to the actual operating conditions. Ideally, classification
as stated in the product specification or test report shall cover the range of operating
conditions during practical use. Classification should be reviewed periodically.
5.2 Spectral match
5.2.1 General
Spectral match may change during the pulse of a pulsed solar simulator and is subject to
spatial non-uniformity. Integration time for spectral irradiance measurement should be
adjusted to the data acquisition time and spectral match should be calculated for that time
period.
5.2.2 Apparatus
The spectroradiometer shall be appropriate for the measurement task. Ensure that the
sensitivity of the sensor is suitable for the wavelength range of interest. The time constant
– 14 – IEC 60904-9:2020 © IEC 2020
(integration time) of the detector shall be suitable for the pulse length of the simulator.
Caution should be taken that the spectrum of the simulator might change during the light
pulse. In the case of spectral shifts, differences in spectral responsivities between the
irradiance monitor and the DUT will introduce spectral mismatch error. The integration time
should be less than half of the pulse length.
The following features and parameters may determine the quality of spectral irradiance
measurement:
• Wavelength resolution: The wavelength resolution of the spectroradiometer should be
equal or less than 5 nm in the visible range (300 nm to 900 nm) and 10 nm in the near
infrared range (900 nm to 1 200 nm). The wavelength step setting of the
spectroradiometer should be equal to or less than the wavelength resolution. Some
apparatus using band pass filters may have wavelength resolution greater than 10 nm.
Such apparatus may be used for classification of spectral match (5.2.3), determination of
SPC (5.5), and determination of SPD (5.6). However, additional apparatus may be
required to satisfy the requirements of Clause 6 for reporting spectral irradiance.
NOTE The wavelength resolution is a measure of the ability of the spectroradiometer to separate two spectral
lines that are close together.
• Non-linearity of sensor element(s): Spectroradiometers are typically calibrated with
tungsten calibration lamps at low irradiance level. However, the spectral intensity of solar
simulators may differ considerably from calibration conditions.
• Stray light or second order wavelength
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