Classification of environmental conditions - Part 2-4: Environmental conditions appearing in nature - Solar radiation and temperature

IEC 60721-2-4:2018 is also available as IEC 60721-2-4:2018 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60721-2-4:2018 presents a broad division into types of solar radiation areas. It is intended to be used as part of the background material when selecting appropriate severities of solar radiation for product applications. All types of geographical areas are covered, except areas with altitudes above 5 000 m. This second edition cancels and replaces the first edition published in 1987 and Amendment 1:1988. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- Figures updated including the addition of global irradiation information
- Format updated.

Classification des conditions d'environnement - Partie 2-4 : Conditions d'environnement présentes dans la nature - Rayonnement solaire et température

IEC 60721-2-4:2018 est disponible sous forme de IEC 60721-2-4:2018 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
L’IEC 60721-2-4:2018 présente une large division en types de zones de rayonnement solaire. Elle est destinée à faire partie de la documentation de base pour choisir des sévérités appropriées de rayonnement solaire pour l'application aux produits. Tous les types de zones géographiques sont couverts, sauf les zones situées à plus de 5 000 m d’altitude. Cette deuxième édition annule et remplace la première édition parue en 1987 et l'Amendement 1:1988. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
- Mise à jour des figures incluant l’ajout d’informations sur l’exposition énergétique globale
- Mise à jour du format.

General Information

Status
Published
Publication Date
21-Jun-2018
Current Stage
PPUB - Publication issued
Completion Date
22-Jun-2018
Ref Project

Buy Standard

Standard
IEC 60721-2-4:2018 - Classification of environmental conditions - Part 2-4: Environmental conditions appearing in nature - Solar radiation and temperature
English and French language
29 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

IEC 60721-2-4
Edition 2.0 2018-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 2-4: Environmental conditions appearing in nature – Solar radiation and
temperature
Classification des conditions d’environnement –
Partie 2-4: Conditions d'environnement présentes dans la nature – Rayonnement
solaire et température
IEC 60721-2-4:2018-06(en-fr)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2018 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC

copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite

ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie

et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des

questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez

les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigenda or an amendment might have been published.
IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org

The stand-alone application for consulting the entire The world's leading online dictionary of electronic and

bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in

Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional

documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical

iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary

The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and

variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of

committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been

and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc

details all new publications released. Available online and If you wish to give us your feedback on this publication or

also once a month by email. need further assistance, please contact the Customer Service

Centre: sales@iec.ch.
A propos de l'IEC

La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des

Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC

Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la

plus récente, un corrigendum ou amendement peut avoir été publié.
Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient 21 000 termes et définitions en anglais
Spécifications techniques, Rapports techniques et autres
et en français, ainsi que les termes équivalents dans 16
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.
Recherche de publications IEC -
Glossaire IEC - std.iec.ch/glossary
webstore.iec.ch/advsearchform
67 000 entrées terminologiques électrotechniques, en anglais

La recherche avancée permet de trouver des publications IEC et en français, extraites des articles Termes et Définitions des

en utilisant différents critères (numéro de référence, texte, publications IEC parues depuis 2002. Plus certaines entrées

comité d’études,…). Elle donne aussi des informations sur les antérieures extraites des publications des CE 37, 77, 86 et

projets et les publications remplacées ou retirées. CISPR de l'IEC.

IEC Just Published - webstore.iec.ch/justpublished Service Clients - webstore.iec.ch/csc

Restez informé sur les nouvelles publications IEC. Just Si vous désirez nous donner des commentaires sur cette

Published détaille les nouvelles publications parues. publication ou si vous avez des questions contactez-nous:

Disponible en ligne et aussi une fois par mois par email. sales@iec.ch.
---------------------- Page: 2 ----------------------
IEC 60721-2-4
Edition 2.0 2018-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 2-4: Environmental conditions appearing in nature – Solar radiation and
temperature
Classification des conditions d’environnement –
Partie 2-4: Conditions d'environnement présentes dans la nature – Rayonnement
solaire et température
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040 ISBN 978-2-8322-5781-4

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60721-2-4:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 General ........................................................................................................................... 5

5 Solar radiation physics .................................................................................................... 6

6 Levels of global radiation ................................................................................................. 7

6.1 Maximum levels ...................................................................................................... 7

6.2 Mean monthly and annual global solar radiation ...................................................... 7

6.3 Simultaneous values of maximum air temperatures and solar radiation ................... 8

6.4 World distribution of daily global irradiation ............................................................. 8

7 Minimum levels of atmospheric radiation at night ............................................................. 8

Annex A (informative) World distribution of daily global irradiation ....................................... 10

Bibliography .......................................................................................................................... 15

Figure 1 – Spectra of electromagnetic radiation from the Sun and the surface

of the Earth ............................................................................................................................. 9

Figure A.1 – Mean relative global irradiation for the month of June (in %) ............................. 12

Figure A.2 – Mean relative global irradiation for the month of December (in %) ..................... 13

Figure A.3 – Mean relative global irradiation for the year (in %) ............................................ 14

Table 1 – Typical peak values of global irradiance (in W/m from a cloudless sky) ................. 7

Table A.1 – Mean daily extra-terrestrial global irradiation (kWh/m ) ...................................... 11

---------------------- Page: 4 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –
Part 2-4: Environmental conditions appearing in nature –
Solar radiation and temperature
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

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 60721-2-4 has been prepared by IEC technical committee 104:

Environmental conditions, classification and methods of test.
This second edition cancels and replaces the first edition published in 1987 and
Amendment 1:1988. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) Figures updated including the addition of global irradiation information,
b) Format updated.
---------------------- Page: 5 ----------------------
– 4 – IEC 60721-2-4:2018 © IEC 2018
The text of this International Standard is based on the following documents:
FDIS Report on voting
104/800/FDIS 104/803/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 60721 series, published under the general title Classification of

environmental conditions, can be found on the IEC website.

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.
---------------------- Page: 6 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 5 –
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –
Part 2-4: Environmental conditions appearing in nature –
Solar radiation and temperature
1 Scope

This part of IEC 60721 presents a broad division into types of solar radiation areas. It is

intended to be used as part of the background material when selecting appropriate severities

of solar radiation for product applications.

All types of geographical areas are covered, except areas with altitudes above 5 000 m.

This document also serves to define limiting severities of solar radiation to which products are

liable to be exposed during transportation, storage and use.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.

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
4 General

Solar radiation can affect products primarily by the heating of material and their environment

or by photochemical degradation of material.

Solar radiation, especially its ultraviolet content, causes photochemical degradation of most

organic materials. Elasticity and plasticity of certain rubber compounds and plastic materials

are affected. Optical glass may become opaque.

Solar radiation bleaches out colours in paints, textiles, paper, etc. This can be of importance,

for example for the colour-coding of components.

The heating of material is a consequence of exposure to solar radiation. The presentation of

severities of solar radiation is therefore related to the power density radiated towards a

surface, or irradiance, expressed in W/m .

An object subjected to solar radiation will attain a temperature that depends primarily on the

surrounding air temperature, the energy radiated from the Sun, and the incidence angle of the

radiation on the object. Other factors, for example wind and heat conduction to mountings,

can be of importance. In addition, the absorptance α of the surface for the solar spectrum

is of importance.
---------------------- Page: 7 ----------------------
– 6 – IEC 60721-2-4:2018 © IEC 2018

An artificial air temperature t may be defined, which, under steady-state conditions, results in

the same surface temperature of an object as the combination of the actual air temperature t

and the solar radiation of the irradiance E.
An approximate value can be obtained from the following equation:
α ⋅E
t =t +
s u

The coefficient h is the heat transfer coefficient for the surface, in W/(m · °C). It includes

thermal radiation to the surroundings, heat conduction of the surface material and convection

due to wind.

The absorptance α , depends on the thermal colour, the reflectance and the transmittance of

the surface.
Typical clear sky values for common materials are:
α = 0,7
h = 20 W/(m · °C)
E = 900 W/m

resulting in an "over temperature" due to solar radiation of about 30 °C. It can then be seen

that an error of 10 % in the estimation of the intensity of the solar radiation will influence the

temperature involved by less than 5 °C. Therefore, there is no need in this classification for

extremely accurate severities of solar radiation and minor factors affecting the heat radiated

have therefore been disregarded here.

The heating effect is caused mainly by short-term radiation of high intensity, i.e. the solar

radiation around noon on cloudless days. Such values are presented in Table 1.

It may also be of interest to identify the lowest possible value of atmospheric radiation during

clear nights in order to determine the “under temperature” of products exposed to the night

sky.
5 Solar radiation physics

The electromagnetic radiation from the Sun to the Earth covers the spectrum from the

ultraviolet to the near infra-red. Most of the energy reaching the surface of the Earth is in the

wavelength range of 0,3 µm to 4 µm with a maximum in the visible range around 0,5 µm.

Typical spectra are shown in Figure 1.

The amount of radiant energy from the Sun which falls upon the unit area of a plane normal to

the Sun's rays just outside the atmosphere at the mean distance from the Earth to the Sun is

called the solar constant. Its value is 1 367 W/m .

The distance from the Earth to the Sun varies during the year, and consequently the radiation

varies.

Approximately 99 % of the energy of the Sun is emitted at wavelengths below 4 µm. Most

of the energy below 0,3 µm is absorbed by the atmosphere and does not reach the surface of

the Earth. Further absorption and scattering of the radiation takes place, due to particles and

gases, during passage through the atmosphere. The scattering of the direct solar radiation in

the atmosphere results in diffuse radiation from the sky. Thus, the energy received at a

certain place on Earth is the sum of the direct solar radiation and the diffuse solar radiation,

---------------------- Page: 8 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 7 –

which is referred to as "global radiation". From the point of view of heating effects, this sum is

of interest and the levels given in this document are therefore related to global radiation.

6 Levels of global radiation
6.1 Maximum levels

The maximum level of global radiation on a clear day occurs at noon. The highest value of

the power achieved on a cloudless day at noon at a surface perpendicular to the direction

of the Sun depends on the content of aerosol particles, ozone and water vapour in the air. It

varies considerably with geographical latitude and type of climate.

The global radiation on a surface perpendicular to the direction of the Sun can reach a value

of 1 120 W/m in a range of 280 nm to 3 000 nm at noon on a cloudless day with

approximately 1 cm of water vapour content, 2 mm of ozone and aerosols of β = 0,05, where β

is the Ångström turbidity coefficient. The value 1 120 W/m is typical for flat land far away

from industrial areas and from large cities at solar elevations exceeding 60°.

NOTE 1 The water vapour content of a vertical column of the atmosphere is measured as the height, in

centimetres, of the corresponding precipitated water. Analogously, the ozone content of a vertical column of the

atmosphere is measured as the height of the corresponding ozone column at normal temperature and pressure.

The scattering and absorption by aerosol particles is expressed by the Ångström turbidity coefficient, which is the

optical depth of the atmosphere with respect to extinction of monochromatic radiation of wavelength λ = 1 µm.

NOTE 2 During partly clouded days the global solar irradiation can increase up to 1 300 W/m for a few minutes.

This short-term phenomenon occurs when the Sun comes out behind the clouds and the radiation is reflected from

the edges of the clouds.

The direct solar radiation decreases with increasing turbidity. Turbidity is high in subtropical

climates and in deserts where the concentration of particles in the air is high. It is also high in

large cities and low in mountainous areas.

The levels in Table 1 are recommended for application as peak values of global irradiance at

noon, experienced by a surface perpendicular to the direction of the Sun in a cloudless sky.

The level varies only by a few per cent within the hours nearest to noon and can therefore be

assumed to be representative for a few hours at a time.
Table 1 – Typical peak values of global irradiance
(in W/m from a cloudless sky)
Area Large cities Flat land Mountainous areas
Subtropical climates and deserts 700 750 1 180
Other areas 1 050 1 120 1 180
6.2 Mean monthly and annual global solar radiation

Whilst the maximum heating effect of solar radiation on a surface is normally dependent on

short-term irradiance around noon, the photochemical effects are related to radiation,

integrated over time, i.e. irradiation. For the purpose of comparison, daily global irradiation is

the most convenient and commonly used value.
In December, the monthly mean average of daily irradiation reaches approximately

10,8 kWh/m close to the South Pole, because of the duration of daylight. Outside the

Antarctic area, daily levels reach approximately 8,4 kWh/m

The highest annual mean averages of daily global irradiation, up to 6,6 kWh/m , are found

mainly in desert areas.
---------------------- Page: 9 ----------------------
– 8 – IEC 60721-2-4:2018 © IEC 2018
6.3 Simultaneous values of maximum air temperatures and solar radiation

The lowest values of the turbidity coefficient β are found in cold air masses. Therefore, the

levels in Table 1 do not occur at the highest values of air temperature.
6.4 World distribution of daily global irradiation
For the distribution of daily global irradiation, see Annex A.
7 Minimum levels of atmospheric radiation at night

In cloudless nights when the atmospheric radiation is very low, objects exposed to the night

sky will attain surface temperatures below the surrounding air temperature.

The theoretical temperature T , in kelvins, of an object in equilibrium with the atmospheric

radiation is given by Boltzmann's law:
1/4
 
T = 
 
where
−8 2 4
σ is Stefan-Boltzmann's constant, 5,67 ⋅ 10 W/(m ⋅ K );
A is the atmospheric radiation in W/m .

In practice, temperatures will be higher due to heat conduction, convection and water

condensation.

As an example, it has been found that the surface of a horizontal disk thermally isolated from

the ground and exposed to the night sky during a clear night can attain a temperature of

−14 °C when the air temperature is 0 °C and the relative humidity is close to 100 %.

The relative humidity is normally very high on clear nights.
---------------------- Page: 10 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 9 –
Ultraviolet Infra-red
Visible light
2 000
1 000
500
200
100
0,1 0,2 0,5 1 2 5 10 20 50 100
Wavelength (µm)
IEC

A Radiation outside the atmosphere from the Sun E Absorption bands of water vapour

represented as a black body at temperature and carbon dioxide
6 000 K (1,60 kW/m )
B Solar radiation outside the atmosphere F Absorption by oxygen and ozone
(1,37 kW/m )

C Direct solar radiation at the surface of the Earth G Radiation of a black body at 300 K

perpendicular to the direction of radiation (0,47 kW/m )
(e.g. 0,9 kW/m )

D Diffuse solar radiation at the surface of the Earth H Thermal radiation from the Earth

2 2
(e.g. 0,10 kW/m ) (e.g. 0,07 kW/m )
Figure 1 – Spectra of electromagnetic radiation from the Sun
and the surface of the Earth
Spectral irradiance (power density per unit of wavelength) W/(m •µm)
---------------------- Page: 11 ----------------------
– 10 – IEC 60721-2-4:2018 © IEC 2018
Annex A
(informative)
World distribution of daily global irradiation

Figures A.1, A.2 and A.3 are world maps showing isohels of relative global irradiation

(June, December and annual mean values), derived from satellite measurements (see [1] ).

Relative global irradiation is defined as the ratio of global irradiation measured at the Earth's

surface, divided by the extra-terrestrial global irradiation, which is the solar radiation on a

plane perpendicular to the direction of the Sun just outside the atmosphere.

In order to obtain the mean daily value of global irradiation at the Earth's surface, the

percentage value shown on the maps should be multiplied by the appropriate mean daily

value of extra-terrestrial global irradiation, which is given as a function of geographical

latitude in Table A.1.

NOTE The basis for determining the daily irradiation values in kWh/m is the values of monthly and annual

irradiation in MJ/m divided by the number of days in June (30), in December (31), and in the year (365).

EXAMPLE:

Determination of the mean daily global irradiation to be expected in June at the southern point of the Californian

peninsula.

From Figure A.1, the point (at an approximate geographical latitude of 23° N) is surrounded by an isohel of 60 %,

and the percentage value for the point is estimated to be 62 %.

In Table A.1, interpolation for 23° N in the June column gives 11,16 kWh/m , which is multiplied by the percentage

value above.
The mean daily global irradiation will thus be approximately 6,9 kWh/m .
___________
Numbers in square brackets refer to the Bibliography.
---------------------- Page: 12 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 11 –
Table A.1 – Mean daily extra-terrestrial global irradiation (kWh/m )
Latitude June December Annual
90 N 12,47 0,0 4,17
85 N 12,42 0,0 4,20
80 N 12,28 0,0 4,30
75 N 12,05 0,0 4,49
70 N 11,72 0,0 4,76
65 N 11,40 0,11 5,16
60 N 11,40 0,65 5,71
55 N 11,48 1,36 6,29
50 N 11,56 2,16 6,87
45 N 11,61 3,00 7,42
40 N 11,61 3,85 7,93
35 N 11,56 4,72 8,40
30 N 11,44 5,57 8,82
25 N 11,26 6,40 9,19
20 N 11,00 7,20 9,49
15 N 10,68 7,96 9,73
10 N 10,30 8,68 9,90
5 N 9,84 9,34 10,01
0 9,33 9,95 10,04
5 S 8,76 10,50 10,01
10 S 8,13 10,98 9,90
15 S 7,46 11,39 9,73
20 S 6,74 11,73 9,49
25 S 5,99 12,00 9,19
30 S 5,21 12,19 8,82
35 S 4,41 12,32 8,40
40 S 3,60 12,37 7,93
45 S 2,79 12,37 7,41
50 S 2,01 12,31 6,86
55 S 1,27 12,22 6,29
60 S 0,60 12,13 5,71
65 S 0,10 12,12 5,16
70 S 0,0 12,45 4,75
75 S 0,0 12,80 4,48
80 S 0,0 13,05 4,30
85 S 0,0 13,20 4,20
90 S 0,0 13,25 4,16
---------------------- Page: 13 ----------------------
– 12 – IEC 60721-2-4:2018 © IEC 2018
IEC
Figure A.1 – Mean relative global irradiation for the month of June (in %)
---------------------- Page: 14 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 13 – I
IEC
Figure A.2 – Mean relative global irradiation for the month of December (in %)
---------------------- Page: 15 ----------------------
– 14 – IEC 60721-2-4:2018 © IEC 2018
IEC
Figure A.3 – Mean relative global irradiation for the year (in %)
---------------------- Page: 16 ----------------------
IEC 60721-2-4:2018 © IEC 2018 – 15 –
Bibliography
[1] G. Major et al., World maps of relative global radiation

[2] World Meteorological Organization, Technical Note No. 172, Annex. WMO-No. 557,

Geneva (1981)
[3] Haarto, Antti, 2001, Estimation methods for sky radiance distribution from
multipyranometer observations, Annales Universitatis Turkuensis Ser A1, vol 265,
Turku, University of Turku, 121 p. ISBN 951-29-1889-7
___________
---------------------- Page: 17 ----------------------
– 16 – IEC 60721-2-4:2018 © IEC 2018
SOMMAIRE

AVANT-PROPOS .................................................................................................................. 17

1 Domaine d’application ................................................................................................... 19

2 Références normatives .................................................................................................. 19

3 Termes et définitions ..................................................................................................... 19

4 Généralités ...................................................................................................

...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.