IEC 60904-5:2011/AMD1:2022

IEC 60904-5 ®
Edition 2.0 2022-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
A MENDMENT 1
AM ENDEMENT 1
Photovoltaic devices –
Part 5: Determination of the equivalent cell temperature (ECT) of photovoltaic
(PV) devices by the open-circuit voltage method

Dispositifs photovoltaïques –
Partie 5: Détermination de la température de cellule équivalente (ECT) des
dispositifs photovoltaïques (PV) par la méthode de la tension en circuit ouvert

IEC 60904-5:2011-02/AMD1:2022-11(en-fr)

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IEC 60904-5 ®
Edition 2.0 2022-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
A MENDMENT 1
AM ENDEMENT 1
Photovoltaic devices –
Part 5: Determination of the equivalent cell temperature (ECT) of photovoltaic

(PV) devices by the open-circuit voltage method

Dispositifs photovoltaïques –
Partie 5: Détermination de la température de cellule équivalente (ECT) des

dispositifs photovoltaïques (PV) par la méthode de la tension en circuit ouvert

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-5728-9

– 2 – IEC 60904-5:2011/AMD1:2022
© IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC DEVICES –
Part 5: Determination of the equivalent cell temperature (ECT) of
photovoltaic (PV) devices by the open-circuit voltage method

AMENDMENT 1
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 document may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 1 to IEC 60904-5:2011 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
The text of this Amendment is based on the following documents:
Draft Report on voting
82/2069/FDIS 82/2082/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Amendment is English.

© IEC 2022
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications/.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under 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.
___________
INTRODUCTION
Add the following new text:
For modules with large thermal inertia such as glass-glass construction for BIPV applications,
measurements become even more challenging with increased temperature difference between
the cell and module external temperatures during transient conditions. In addition, for bifacial
PV modules the temperature sensors may shade an active cell, potentially even creating local
hotspots where sensors are located on effective cell areas.
NOTE 1 NMOT is defined as the equilibrium mean solar cell junction temperature within an open-rack mounted
module operating near peak power, in the following standard reference environment:
– Tilt angle: (37 ± 5)°.
– Total irradiance: 800 W/m .
– Ambient temperature: 20 °C.
– Wind speed: 1 m/s.
– Electrical load: A resistive load sized such that the module will operate near its maximum power point at STC or
an electronic maximum power point tracker (MPPT).
NOTE 2 NMOT is similar to the former NOCT except that it is measured with the module under maximum power
rather than in open circuit. Under maximum power conditions (electric) energy is withdrawn from the module,
therefore less thermal energy is dissipated throughout the module than under open-circuit conditions. Therefore
NMOT is typically a few degrees lower than the former NOCT.

1 Scope and object
Replace the first paragraph with the following text:
This part of IEC 60904 describes the preferred method for determining the equivalent cell
temperature (ECT) of PV devices (cells, modules and arrays of one type of module), for the
purposes of comparing their thermal characteristics, determining NOCT (nominal operating cell
temperature) or alternatively NMOT (nominal module operating temperature), and translating
measured I-V characteristics to other temperatures.

– 4 – IEC 60904-5:2011/AMD1:2022
© IEC 2022
2 Normative references
Add the following standards to the list of normative references:
IEC TS 60904-1-2:2019, Photovoltaic devices – Part 1-2: Measurement of current-voltage
characteristics of bifacial photovoltaic (PV) devices
IEC 60904-3, Photovoltaic devices – Part 3: Measurement principles for terrestrial photovoltaic
(PV) solar devices with reference spectral irradiance data
Delete the following standard from the list of normative references:
ISO/IEC 17025, General requirements for competence of testing and calibration laboratories

3.1 Principle
Replace the text of this subclause with the following new text:
Experience shows that the equivalent cell temperature can be determined more precisely by
. However, increased
the method described herein than by any alternative technique [1]
variability and errors have been observed at irradiances below 400 W/m , so this method should
only be used at irradiances above this threshold.
3.2 General measurement requirements
Add the following new text:
a) Use of the ECT method requires calibration of the device to be measured.
NOTE It is not sufficient to use calibration of another device of the same type, because even small differences
in parameters between a calibrated device and a similar one can lead to significant errors (e.g. 0,3 % variation
in module V leads to 1 °C impact on ECT temperature).
OC
Renumber existing item a)1) as item b)1) as follows:
1) The variation of V needs to be linear as defined in IEC 60904-10 with respect to
OC
temperature.
Replace item a)2) as item b)2) with the following new text:
2) The variation of V with respect to irradiance needs to have a quadratic dependence on
OC
the logarithm of irradiance.
Delete items a)3) and a)4).
___________
Numbers in square brackets refer to the Bibliography.

© IEC 2022
Replace the
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