IEC 60904-5:2011

IEC 60904-5 ®
Edition 2.0 2011-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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

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IEC 60904-5 ®
Edition 2.0 2011-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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
PRICE CODE
INTERNATIONALE
CODE PRIX K
ICS 27.160 ISBN 978-2-88912-366-7

– 2 – 60904-5  IEC:2011
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope and object . 6
2 Normative references . 6
3 Measurement principle and requirements . 6
3.1 Principle . 6
3.2 General measurement requirements . 7
4 Apparatus . 7
5 Determination of required input parameters . 7
6 Procedure . 8
6.1 General . 8
6.2 Operating in a controlled environment . 8
6.3 Taking measurements under arbitrary irradiance conditions . 8
7 Calculation of equivalent cell temperature . 8
8 Test report. 9

60904-5  IEC:2011 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC DEVICES –
Part 5: Determination of the equivalent cell temperature (ECT)
of photovoltaic (PV) devices by the open-circuit voltage method

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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International Standard IEC 60904-5 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
This second edition cancels and replaces the first edition, issued in 1993, and constitutes a
technical revision.
The main technical changes with regard to the previous edition are as follows:
• added and updated normative references;
• added reporting section;
• added method on how to extract the input parameters;
• rewritten method on how to calculate ECT;
• reworked formulae to be in line with IEC 60891.

– 4 – 60904-5  IEC:2011
The text of this standard is based on the following documents:
CDV Report on voting
82/595/CDV 82/626/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
A list of all parts of IEC 60904 series, under the general title Photovoltaic devices, can be
found on the IEC website.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60904-5  IEC:2011 – 5 –
INTRODUCTION
When temperature sensors, such as thermocouples, are used to determine the cell
temperature of PV devices under natural or simulated steady-state irradiance, two main
problems arise. First, a considerable spread of temperature can be observed over the area of
the module. Second, as the solar cells are usually not accessible, sensors are attached to the
back of the module and the measured temperature thus is influenced by the thermal
conductivity of the encapsulant and back materials. These problems are aggravated when
determining the equivalent cell temperature for on-site measurements of array performance
where all cells have slightly different temperatures and one cannot easily determine the
average cell temperature.
The equivalent cell temperature (ECT) is the average temperature at the electronic junctions
of the device (cells, modules, arrays of one type of module) which equates to the current
operating temperature if the entire device were operating uniformly at this junction
temperature.
– 6 – 60904-5  IEC:2011
PHOTOVOLTAIC DEVICES –
Part 5: Determination of the equivalent cell temperature (ECT)
of photovoltaic (PV) devices
by the open-circuit voltage method

1 Scope and object
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) and translating measured I-V characteristics to other temperatures.
This standard applies to linear devices with logarithmic V dependence on irradiance and in
OC
stable conditions. It may be used for all technologies but one has to verify that there is no
preconditioning effect influencing the measurement.
2 Normative references
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.
IEC 60891, Photovoltaic devices – Procedures for tem
...