IEC TS 62257-9-6:2019

Renewable energy and hybrid systems for rural electrification - Part 9-6: Integrated systems - Recommendations for selection of Photovoltaic Individual Electrification Systems (PV-IES)

IEC 62257-9-6:2019 proposes a simple selection procedure and cheap, comparative tests which can be performed in laboratories of developing countries, in order to identify the most suitable model of small Photovoltaic Individual Electrification Systems (PV- IES) up to 500 Wp for a particular rural electrification project from a number of products submitted for test. The tests provided in IEC TS 62257-9-6 allow assessment of the performance of a PV-IES according to the requirement of the general specification of the project (see IEC/TS 62257-2) and to verify their ability to provide the required service. This second edition of IEC TS 62257-9-6 cancels and replaces the first edition published in 2008. The main technical changes with respect to the previous edition are as follows:
- Removal of the term "small" from the title of the publication and from description of rural electrification systems.
- Removal of the limits on system voltage and power; these recommendations apply to systems of all sizes.

General Information

• Status: Published
• Publication Date: 25-Sep-2019
• ICS: 27.160 - Solar energy engineering
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: JWG 1 - TC 82/JWG 1
• Current Stage: PPUB - Publication issued
• Start Date: 26-Sep-2019
• Completion Date: 30-Sep-2019

Relations

• Revises: IEC TS 62257-9-6:2008 - Recommendations for small renewable energy and hybrid systems for rural electrification - Part 9-6: Integrated system - Selection of Photovoltaic Individual Electrification Systems (PV-IES)
• Effective Date: 05-Sep-2023

Overview

IEC TS 62257-9-6:2019 - "Renewable energy and hybrid systems for rural electrification - Part 9-6: Integrated systems - Recommendations for selection of Photovoltaic Individual Electrification Systems (PV‑IES)" is a technical specification from the IEC 62257 series. It provides a simple, practical selection procedure and low-cost comparative tests that can be carried out in laboratories - including those in developing countries - to identify the most suitable PV‑IES model for a rural electrification project. While earlier editions focused on PV‑IES up to 500 Wp, the 2019 edition removed limits on system voltage and power so the recommendations apply to systems of all sizes.

Key topics and requirements

• Pre-selection process: Guidance on defining the General Specification (GS) and the information to be requested from suppliers (design, operating conditions, components, safety, installation, operation & maintenance, documentation and marking).
• Comparative testing programme: A structured set of tests to assess product suitability:
  • Test 1 - Initial inspection and commissioning
  • Test 2 - Ability to provide required service under daylight-favourable conditions (initial charge cycles and operating cycles)
  • Test 3 - Ability to provide required service under daylight-unfavourable conditions
  • Test 4 - Final inspection and acceptance
• Service Quality Index (SQI): Quantitative indexes and scoring methods to evaluate lighting, radio/TV and refrigeration services against project requirements.
• Load profiles and examples: Annexes provide sample load profiles and instructions for recording daily performance to simulate real use cases during comparative tests.
• Practical test sheets: Informative annexes include visual inspection, commissioning records and data record templates to standardize laboratory testing and field verification.
• Safety and environmental considerations: Component requirements, IP/IK protection suggestions and installation/operation rules tailored for rural electrification contexts.

Applications and users

This specification is intended for stakeholders involved in off‑grid and rural electrification projects who need a repeatable, low‑cost method to select PV‑IES products. Typical users include:

• Project implementers and NGOs selecting systems for communities
• National and local governments procuring rural electrification solutions
• Product suppliers preparing submissions for comparative evaluation
• Laboratory technicians and test centres in developing countries
• Installers, supervisors and maintenance teams validating commissioning and operation

Related standards

• IEC 62257 series (general guidance for renewable and hybrid systems for rural electrification)
• IEC/TS 62257-2 (general specifications referenced for project requirements)

Keywords: IEC TS 62257-9-6, PV-IES, photovoltaic individual electrification systems, rural electrification, selection procedure, comparative tests, service quality index, load profiles, commissioning, IEC 62257.

Standards Content (Sample)

IEC TS 62257-9-6 ®
Edition 2.0 2019-09
TECHNICAL
SPECIFICATION
colour
inside
Renewable energy and hybrid systems for rural electrification –
Part 9-6: Integrated systems – Recommendations for selection of Photovoltaic
Individual Electrification Systems (PV-IES)
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IEC TS 62257-9-6 ®
Edition 2.0 2019-09
TECHNICAL
SPECIFICATION
colour
inside
Renewable energy and hybrid systems for rural electrification –

Part 9-6: Integrated systems – Recommendations for selection of Photovoltaic

Individual Electrification Systems (PV-IES)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160; 27.180 ISBN 978-2-8322-7353-1

– 2 – IEC TS 62257-9-6:2019 © IEC 2019
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 9
4 System boundaries . 9
5 System pre-selection . 9
5.1 Services to be provided by the system . 9
5.2 Specification of a model . 9
5.2.1 General operating conditions . 9
5.2.2 Design . 9
5.2.3 Components requirements . 10
5.2.4 Safety issues . 10
5.2.5 Installation rules . 10
5.2.6 Operation and maintenance rules . 10
5.2.7 Documentation and marking . 10
5.3 Pre-selection process . 11
5.3.1 Elements of the GS to be provided to potential suppliers . 11
5.3.2 Answers to be provided by potential suppliers . 11
5.3.3 Pre-selection criteria . 11
6 Comparative tests . 11
6.1 General . 11
6.2 Service requirements . 12
6.3 Service quality index . 12
6.4 Testing programme . 15
6.4.1 General . 15
6.4.2 Test 1: initial inspection and commissioning . 16
6.4.3 Test 2: ability to provide the required service under daylight favourable
conditions . 17
6.4.4 Test 3: ability to provide the required service under daylight
unfavourable conditions . 20
6.4.5 Test 4: final inspection . 22
6.4.6 General conclusion . 22
Annex A (informative) Data record sheet for visual inspection . 24
Annex B (informative) Commissioning records sheet . 25
Annex C (informative) Examples of load profiles for comparative tests . 26
C.1 Examples of loads. 26
C.2 Examples of systems . 26
C.3 Examples of load profiles . 27
Annex D (informative) Instruction and data record sheet models (according to a load
profile as proposed in Annex A) . 28
Bibliography . 35

Figure 1 – Test 2, Phase A: initial charge cycles . 18
Figure 2 – Test 2, Phase B: operating cycles . 19
Figure 3 – Test 3, operating cycles . 21

Table 1 – Climatic conditions (example) . 9
Table 2 – Suggested minimum values for IP and IK . 10
Table 3 – Lighting service indexes . 13
Table 4 – Radio / TV service indexes . 14
Table 5 – Refrigeration service indexes . 14
Table 6 – Testing programme . 16
Table A.1 – Data record sheet for visual inspection (example) . 24
Table B.1 – Commissioning records sheet (example) . 25
Table C.1 – Example of loads . 26
Table C.2– Example of small PV-IES loads (~50 Wp) . 26
Table C.3 – Example of medium PV-IES loads (~200 Wp) . 26
Table C.4 – Example of large PV-IES loads (~500 Wp) . 27
Table C.5 – Example of system load profile to perform test on PV-IES . 27
Table D.1 – Overview instruction sheet for daily records (example) . 28
Table D.2 – Record sheet for lighting service (example) . 30
Table D.3 – Record sheet for radio service (example) . 31
Table D.4 – Record sheet for TV service (example) . 32
Table D.5 – Record sheet for refrigeration service (example) . 33
Table D.6 – System daily quality index of service evaluation (example) . 34

– 4 – IEC TS 62257-9-6:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RENEWABLE ENERGY AND HYBRID SYSTEMS
FOR RURAL ELECTRIFICATION –
Part 9-6: Integrated systems – Recommendations for selection
of Photovoltaic Individual Electrification Systems (PV-IES)

FOREWORD
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Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62257-9-6, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

This second edition of IEC TS 62257-9-6 cancels and replaces the first edition published in
2008. It constitutes a technical revision.
The main technical changes with respect to the previous edition are as follows:
• Removal of the term "small" from the title of the publication and from description of rural
electrification systems.
• Removal of the limits on system voltage and power; these recommendations apply to
systems of all sizes.
This part of IEC 62257 is to be used in conjunction with the IEC 62257 series.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/1279/DTS 82/1533A/RVDTS
Full information on the voting for the approval of this technical specification 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 of IEC 62257 series, under the general title: Renewable energy and hybrid
systems for rural electrification, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
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.
A bilingual version of this publication may be issued at a later date.

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 TS 62257-9-6:2019 © IEC 2019
INTRODUCTION
The IEC 62257 series intends to provide different players involved in rural electrification
projects (such as project implementers, project contractors, project supervisors, installers,
product suppliers, etc.) documents for setting up renewable energy and hybrid systems with
a.c. voltage below 1 000 V and d.c. voltage below 1 500 V.
These documents are recommendations:
• to choose the right system for the right place;
• to design the system;
• to ensure product quality and installation quality;
• to operate and maintain the system.
These documents are focused on off-grid electricity access, concentrating on, but not limited
to, areas with a significant fraction of the population living without reliable electric grid access.
They should not be considered as providing complete coverage of all issues related to rural
electrification.
This set of documents is best considered as a whole, with different parts covering topics such
as safety, system design, product quality, installation and maintenance, and the sustainability
of systems aiming at the lowest life cycle cost possible. One of the main objectives is to
provide minimum requirements relevant to renewable energy and hybrid off-grid power
systems.
RENEWABLE ENERGY AND HYBRID SYSTEMS
FOR RURAL ELECTRIFICATION –
Part 9-6: Integrated systems – Recommendations for selection
of Photovoltaic Individual Electrification Systems (PV-IES)

1 Scope
The purpose of this part of IEC 62257 is to propose simple selection procedure and cheap,
comparative tests which can be performed in laboratories of developing countries, in order to
identify the most suitable model of Photovoltaic Individual Electrification Systems (PV-IES) up
to 500 Wp for a particular rural electrification project from a number of products submitted for
test.
It is different from the scope of IEC 62124, Photovoltaic (PV) stand alone systems – Design
verification, which provides guidance for verifying the design of stand-alone PV systems and
indoor and outdoor tests in order to evaluate the performance of PV systems including PV
generator, battery storage and loads such as lights, TV sets, and refrigerators.
The tests provided in this document allow assessment of the performance of PV-IES
according to the requirement of the General Specification (GS) of the project (see
IEC TS 62257-2) and to verify their ability to provide the required service. They are performed
locally, as close as possible to the real site operating conditions.
This document is not a type approval standard. It is a technical specification to be used as
guidelines and does not replace any existing IEC standard on PV systems.
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 61215 (all parts), Crystalline silicon terrestrial photovoltaic (PV) modules – Design
qualification and type approval
IEC 61730-1, Photovoltaic (PV) module safety qualification – Part 1: Requirements for
construction
IEC 61730-2, Photovoltaic (PV) module safety qualification – Part 2: Requirements for testing
IEC TS 62257-2:2015, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 2: From requirements to a range of electrification systems
IEC TS 62257-4, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 4: System selection and design
IEC TS 62257-5, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC TS 62257-6, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement

– 8 – IEC TS 62257-9-6:2019 © IEC 2019
IEC TS 62257-7-1, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 7-1: Generators – Photovoltaic generators
IEC TS 62257-8-1:2018, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 8-1: Selection of batteries and battery management systems for stand-alone
electrification systems – Specific case of automotive flooded lead-acid batteries available in
developing countries
IEC TS 62257-9-3, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-3: Integrated system – User interface
IEC TS 62257-9-4, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-4: Integrated system – User installation
IEC TS 62257-12-1, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 12-1: Selection of lamps and lighting appliances for off-grid electricity
systems
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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
3.1.1
cycle
sequence of a discharge followed by a charge or a charge followed by a discharge of a
battery under specified conditions
3.1.2
duration of service
number of hours when a load is powered
3.1.3
fulfilment of service
ratio of a measured provided service to a required service
3.1.4
initial charge
commissioning charge given to a new battery to bring it to the fully charged state
3.1.5
period of service
part of the day when a load is powered
3.1.6
reference irradiation
value of irradiation taken in consideration for the design of the system, approved by the
project implementer and specified in the GS of the project

3.1.7
service ratio
extent in which the service required by the GS is fulfilled by the system
3.2 Abbreviated terms
GS general specification for the project
QI quality of service index
TWQI total weighted quality of service
T
DWQI daily weighted quality of service
T
S service ratio under favourable conditions
good
S service ratio under unfavourable conditions
bad
S daily service ratio
d
4 System boundaries
A PV-IES comprises the following elements:
• a PV generator including PV modules and support structure;
• a charge controller;
• a storage system (including battery and associated casing);
• adequate wiring, switches and protective devices (see IEC TS 62257-9-3 and
IEC TS 62257-9-4);
• loads relevant for the required service (such as lamps, TV set, radio set, and refrigerators).
5 System pre-selection
5.1 Services to be provided by the system
The preliminary socio-economic studies shall provide the project developer with information
on the ability of the customers who will benefit from the project to pay for the service provided.
Then, the project developer shall define within the GS the range of services to be provided as
described in IEC TS 62257-2 as well as the relative priority of the services to be provided (TV,
lighting, etc.)
5.2 Specification of a model
5.2.1 General operating conditions
The project implementer shall define the operating conditions to which the PV-IES can be
subjected. Examples of such conditions are given in Table 1.
Table 1 – Climatic conditions (example)
Nominal operating range Storage – Transport
Temperature –10 °C to +50 °C –40 °C to +80 °C
Humidity at 28 °C 5 % to 95 %
Atmospheric pressure 860 hPa to 1 060 hPa

5.2.2 Design
For the part of the project which will be implemented through Individual Electrification
Systems, the project developer shall size a range of PV IES able to provide the required

– 10 – IEC TS 62257-9-6:2019 © IEC 2019
service under the specified operating conditions (see IEC TS 62257-2). The project
implementer could either:
• specify complete integrated systems, or
• specify the different components for PV-IES in order to realize the integration of these
components through its own system design.
In addition, the project developer shall set up the requirements for the loads relevant for the
service to be provided (such as lamps, TV set, radio set, and refrigerator).
5.2.3 Components requirements
The components of the PV-IES shall comply with the relevant IEC standards and/or the
relevant local regulations if any.
For the selection of batteries, tests recommended in IEC TS 62257-8-1 shall apply and for the
selection of lamps, tests recommended in IEC TS 62257-12-1 shall apply.
5.2.4 Safety issues
The project developer shall define the IP degree and IK code of the expected products.
Table 2 gives some values that could be considered as a minimum.
Table 2 – Suggested minimum values for IP and IK
Protection degree Minimum suggested value
IP 34
IK 8
Safety rules shall comply with IEC TS 62257-5.
5.2.5 Installation rules
The complete installation shall comply with IEC TS 62257-7-1 and IEC TS 62257-9-4 and any
local wiring codes.
5.2.6 Operation and maintenance rules
The systems shall be designed in order that operation and maintenance may be performed in
accordance with the specifications given in IEC TS 62257-6.
5.2.7 Documentation and marking
A manual shall also be provided including PV-IES installation and operating guidelines such
as:
• initial operations before first use;
• instructions to use the PV-IES properly;
• mounting the PV module;
• charging instructions;
• maintenance and troubleshooting instructions.

5.3 Pre-selection process
5.3.1 Elements of the GS to be provided to potential suppliers
The project implementer shall supply the annual locally available solar irradiation curve.
NOTE This information could be provided through available laboratory data or through local measurements
performed with a reference cell that will be used afterwards for the comparative tests.
This information as well as the requirements defined in 5.1 and 5.2 shall be provided to
potential suppliers in order to receive proposals for relevant products.
The project implementer could:
• provide load requirements and let the suppliers provide systems to supply the load, or
• provide a complete PV-IES system specification, in order to source complete integrated
PV-IES, or
• provide components requirements in order to source separately the different components
of a PV-IES and realize the integration of these components.
5.3.2 Answers to be provided by potential suppliers
The supplier of the PV-IES and/or of the components shall prove that the PV-IES and/or the
components comply with the relevant IEC standards and IEC 62257 technical specifications.
A technical sheet shall be provided by the supplier in order to demonstrate the ability of its
product to match the requirements defined in 5.1 and 5.2.
5.3.3 Pre-selection criteria
The performances claimed by the manufacturer shall be compared to the performances
required by the GS in order to make a pre-selection of available products.
The following general criteria can be used as an initial help for product pre-selection:
• services characteristics claimed by the manufacturer (duration of service and fulfillment of
service);
• conformity of the modules with the following IEC standards: IEC 61215 series and
IEC 61730-1 and IEC 61730-2;
• conformity of the batteries, lamps, etc., with the relevant IEC standards and pre-selection
process of potential products as recommended in the IEC TS 62257 series;
• battery casing characteristics.
A short list of products potentially able to match the requirements of the GS shall be set up by
the project implementer.
6 Comparative tests
6.1 General
After the pre-selection process, samples of products of the short list shall be processed
through comparative technical tests.
IMPORTANT: All the pre-selected systems shall be tested simultaneously in the same local
conditions in order to ensure that they are tested under the same environmental parameters
(irradiation, humidity, temperature, etc.).

– 12 – IEC TS 62257-9-6:2019 © IEC 2019
Tests could be performed either in outdoor conditions, in local laboratories or in site
conditions (on future customer homes for instance). The systems installation rules provided in
the GS are also applicable to test installations.
6.2 Service requirements
Pre-selected models shall be examined to ensure that they will provide the required services
mentioned in the GS according to the load profile used for the design of the system.
A service is defined by:
• The types of appliances/loads powered by the system (such as lamps, TV set, etc.);
• For each type of appliance:
– the number of appliances that can be simultaneously powered;
– the daily duration of the power supply;
– the fulfilment of the provided service.
6.3 Service quality index
A Quality of service Index (QI) of a system is based on one of these two terms:
• d = duration index, d, is the ratio of the measured daily duration of service compared to the
required daily duration of service;
• f = fulfilment index, f, is the ratio of the measured performance (illuminance for lamps,
temperature for refrigerator, etc.) compared to a reference level required by the GS.
For the different considered services the QI takes into account either, d, or, f:
– for lighting: f;
– for radio: d;
– for TV: d;
– for refrigeration: f.
The systems shall be compared through a Total Weighted Quality of service Index (TWQI )
T
calculated on the basis of observations and measurements performed during, T, days of
comparative tests.
The TWQI and service ratio (S) are calculated as follows:
T
a) Step 1: for each service, calculation every day of either “duration” or “fulfilment”
indexes
The following Tables 3 to 5 illustrate the necessary index evaluation data and calculation
rules.
Table 3 – Lighting service indexes
Service Lighting
Requirements Number of lamps  N

L
Daily duration of service per lamp (h) D

L
Illuminance (lux)  Q
Duration index Fulfilment index
Measured Total Fulfilment index
illuminance measured
illuminance for
every hour of
service
lux lux
see Note 1 see Note 2
Not relevant
For lamp 1:
q
L1
j=D i=n
L
For lamp 2: i=n q
∑∑ L
i
q
j=1 i=1
L2 q
L f =
∑
i Lighting
n×Q
… i=1
For lamp i:
q
Li
NOTE 1 n = number of illuminance measurements at each hour of service; n ≤ N
.
L
NOTE 2 In order to limit the number of measurements, if N > 3, n could be limited to n = 3.
L
j=D i=3
L
q
∑∑ L
i
j=1 i=1
In this case the formula becomes:
f =
Lighting
3×Q
In this example only 3 lamps out of N are measured every hour. Generally it is preferable to

L
ensure that all the lamps have been equally monitored at the end of the test.
A complete example for the lighting service is given in Table D.2.

– 14 – IEC TS 62257-9-6:2019 © IEC 2019
Table 4 – Radio / TV service indexes
Service Radio (or TV) (see Note)
Requirements Number of radio sets N

R
Daily duration of service per set (h) D

R
Duration index Fulfilment index
Total required Measured daily Total measured Duration index
daily duration of duration of daily duration of
service service service
h h h
For set 1: Not relevant
i=N
R
d
R1
d
i=N
R
R ∑
i
i=1
N × D d
∑ R
R R i d =
Radio
N × D
i=1
R R
For set N:
d
RN
NOTE In the TV set case, subscript R should be changed to T.

Table 5 – Refrigeration service indexes
Service Refrigeration
Requirements Number of refrigerators N (N =1 in most cases)
F F
Daily duration of service (h) Not relevant
Temperature (°C) Temperature reference: T°
Duration index Fulfilment index
Measured Average Fulfilment index
measured
temperature: Θ
temperature
deviation
Not relevant
°C
°C
See Note
measure 1
i=n
 
∆θ = Θ – T
i=n
1 1  
∆θ
∑ i
 
∆θ
measure 2
∑ i
i=1
f = 1− 
i=1
∆θ
2  n× T 
n
 
…
 
 
measure n
∆θ
n
NOTE n = number of temperature measurements.

b) Step 2: for each tested system, calculation of a DWQIT
For a given service X, the Quality of service Index (QI) is:
QI = d
X X
or
QI = f
.
X X
If the project implementer does not give the same priority to the services, he could
determine some “weighting coefficients”, k, reflecting the relative importance assigned to
the different services provided.

The relative priority of the different services shall be determined by a socio-economic
study (see 5.1).
Using these weighting coefficients, a Daily Weighted Quality Index (DWQI) shall be
calculated for a system, as given in the following formula (1). For a given day, t, and for X
types of services:
i=X
DWQI = k × QI (1)
t
∑ i i
i=1
– For lamps: k = k
Lighting L
– For radios: k = k
Radio R
– For TVs: k = k
TV T
– For refrigerators: k = k
Fridge F
Using this hypothesis, for a system providing all the mentioned services the DWQI for a
day, t, is:
DWQI = (k × QI ) + (k × QI ) + (k × QI ) + (k × QI )
t L Lighting R Radio T TV F Fridge
It is the project developer’s responsibility to determine the k coefficients according to the
importance he gives to each service.
As an example, a convenient rule to determine values for the weighting coefficient, k, may
be based on the daily required duration of service (see Table D.6).
c) Step 3: for each tested system, calculation of a TWQI
T
On the complete duration of the test, a TWQI shall be determined according to the
T
following formula (2). For a test performed on, T, days:
t=T
TWQI = DWQI (2)
T ∑ t
t=0
i=X
with TWQI = T × k (case where all service quality indexes are equal to 1)
,max
T ∑ i
i=1
d) Step 4: for each tested system, calculation of a service ratio, S
The laboratory operator shall calculate the maximum value of the TWQI in the conditions
T
of the test.
Then he shall calculate for each system the service ratio by the following formula (3):
TWQI
T,act
S= (3)
TWQI
T,max
where
TWQI : results of TWQI ;
T,act T
and TWQI : maximum value of TWQI
T,max T
This ratio expresses to what extent the system is able to provide the service required by
the GS.
6.4 Testing programme
6.4.1 General
The comparative tests include a set of 4 tests as indicated in Table 6.

– 16 – IEC TS 62257-9-6:2019 © IEC 2019
The complete set of tests is intended to be performed within a period of 90 days during the
appropriate season as identified during the project preliminary studies and according to the
quality of service specified by the project developer (see IEC TS 62257-2:2015, Annex C).
The system shall be tested under two daylight conditions:
• Daylight favourable conditions: in this configuration local irradiation is at least 90 % of the
reference value given in the GS.
• Daylight unfavourable conditions: in this configuration, the irradiation taken into account
shall be determined by the project implementer as a percentage of the reference value
given in the GS (such as for example the irradiation during the rainy season).
Table 6 – Testing programme
Test 1 Test 2 Test 3 Test 4
Ability to provide Ability to recover Final inspection
Initial inspection
the required the required
and commissioning
service under service under
daylight daylight
Favourable Unfavourable
conditions conditions
See 6.4.2 See 6.4.3 See 6.4.4 See 6.4.5

6.4.2 Test 1: initial inspection and commissioning
6.4.2.1 General
The purpose of the different inspection tests (Test 1 and Test 4) is to assess the evolution /
degradation of the conditions of the different parts of the product during the test period,
especially casings, lamps, cables and PV modules.
The initial inspection is intended to record all necessary details of each sample of each pre-
selected model and identify the sample for the duration of all tests. It will also verify that the
sample has been supplied with all necessary items and components required by the GS.
In Test 1, after the initial inspection, the system shall be commissioned.
As much information as possible concerning each sample to be tested should be recorded.
6.4.2.2 Sampling
Three samples of each model are required. For small projects, if the cost of the testing is too
high, the sampling could be limited to two samples of each model.
A test item number shall be assigned to each sample and used in all data sheets and records
to avoid confusing sample results. It is recommended that the unit should be photographed in
such a way that all major accessible components are recorded.
6.4.2.3 Operation
The initial inspection shall be performed in two steps:
• unpacking step; and
• installation step.
A list (non comprehensive) of items to be checked and recorded during these two periods is
provided as an example in Annex A.
After the initial inspection and installation of the system, commissioning shall be performed
(an example of a commissioning sheet is given in Annex B).
6.4.2.4 Results
The pass criteria is based on the following:
For each sample:
• there shall be no visual evidence of a major defect on any component; and
• the sample is complete; and
• the installed system has been commissioned satisfactorily.
The fail criteria is based on the following:
For each sample:
• there is evidence of a major defect; or
• some components are missing or incorrect; or
• the system cannot be installed properly according to the GS requirements.
It is up to the project implementer to determine whether he will accept a certain model if one
or more samples have failed this initial visual inspection.
6.4.3 Test 2: ability to provide the required service under daylight favourable
conditions
6.4.3.1 General
The purpose of this test is to check the ability of a PV-IES product to perform the required
service under daylight sunny conditions considered as favorable.
A reference load profile shall be established for the tests according to the service required in
the GS. Some examples of such load profiles are given in Annex C.
6.4.3.2 Sampling
Each model for which all samples passed Test 1 shall go through to Test 2.
6.4.3.3 Equipment
To perform Test 2 the following equipment shall be necessary:
• A power system to supply energy to all test instruments.
If the testing is performed in a laboratory connected to a grid, no additional power system
is necessary. If the testing is performed on site, a dedicated power system is necessary to
supply energy to testing devices.
• A reference device (such as a reference PV module, pyrheliometer, etc.) to assess and
record the daily irradiation.
This device may also be initially used to assess the value of the irradiation to be taken in
account for the design of the systems.

– 18 – IEC TS 62257-9-6:2019 © IEC 2019
• Test instruments:
– Programmable controllers to monitor the load profiles. If not, the loads may be
switched on/off manually.
– One (or several) illuminance measurement box(es) (see IEC TS 62257-12-1).
– A thermometer, preferably electronic.
6.4.3.4 Operation
6.4.3.4.1 General
Test 2 shall be performed according to the following phases:
6.4.3.4.2 Phase A: initial preparation
This phase is dedicated to charge the battery before testing the ability of the system to
perform the required service.
The initial charge is controlled by the charge controller of the PV-IES without any manual
intervention. During the initial charge, all the loads shall be switched off.
The initial charge shall be performed for, x days (x ≥ 5) until 5 "good sunny days" have been
recorded. A "good sunny day" is defined as a day when irradiation is equal to or greater than
90 % of the reference irradiation defined in the GS (considered as favourable conditions).
The following Figure 1 illustrates the Phase A cycles:
START Test 2,
Phase A
t = 0
Sunrise
Charge battery
under daylight
without any load
t = x days
STOP Test 2,
Repeat x days the cycle (until 5 “good sunny days”)
Phase A
Wait until next
morning without
any load
Sunset
IEC
NOTE It would be preferable to perform the initial charge in the season when the probability of having five "good
sunny days" consecutively is the highest.
Figure 1 – Test 2, Phase A: initial charge cycles
6.4.3.4.3 Phase B: operating conditions
This phase is dedicated to run the system over a long period in order to check its ability to
provide the required services under local operating conditions.
Phase B shall be performed immediately after Phase A.
Figure 2 illustrates the cycles to be performed.

The time for start is chosen a short while before sunrise.
The charging of the battery is controlled by the charge controller provided within the system.
The loads are switched on and off according to the load profile, either manually by the
laboratory operator or automatically by a programmable controller.
Between sunrise and sunset, the system is intended to be both able to charge the battery and
to supply energy to loads (according to the load profile).
After sunset, the system is intended to be able to supply the loads according to the load
profile which reflects as close as possible the way of life of the future customers.
The sunrise-sunset cycle shall be repeated, y, days (y ≥ 30) until 30 "good sunny days" have
been recorded.
It is better to perform the test during the sunny season and to ensure that, y, is less than or
equal to 40 days. This is intended to shorten the duration of the test and thus reduce its cost
and ensure good quality records.
The laboratory operator shall observe and record the start and the end of the service
according to each step of the load profile.
An example of an instruction sheet for the operator is given in Annex D. For the duration of
the test, the laboratory
...

IEC TS 62257-9-6 ®
Edition 2.0 2019-09
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for small Renewable energy and hybrid systems for rural
electrification –
Part 9-6: Integrated system – Recommendations for selection of Photovoltaic
Individual Electrification Systems (PV-IES)

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IEC TS 62257-9-6 ®
Edition 2.0 2019-09
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for small Renewable energy and hybrid systems for rural

electrification –
Part 9-6: Integrated system – Recommendations for selection of Photovoltaic

Individual Electrification Systems (PV-IES)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160; 27.180 ISBN 978-2-8322-7454-5

– 2 – IEC TS 62257-9-6:2019 RLV © IEC 2019
CONTENTS
FOREWORD . 4
INTRODUCTION . 2
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 10
4 System boundaries . 10
5 System pre-selection . 10
5.1 Services to be provided by the system . 10
5.2 Specification of a model . 10
5.2.1 General operating conditions . 10
5.2.2 Design . 11
5.2.3 Components requirements . 11
5.2.4 Safety issues . 11
5.2.5 Installation rules . 11
5.2.6 Operation and maintenance rules . 11
5.2.7 Documentation and marking . 12
5.3 Pre-selection process . 12
5.3.1 Elements of the GS to be provided to potential suppliers . 12
5.3.2 Answers to be provided by potential suppliers . 12
5.3.3 Pre-selection criteria . 12
6 Comparative tests . 13
6.1 General . 13
6.2 Service requirements . 13
6.3 Service quality index . 13
6.4 Testing programme . 16
6.4.1 General . 16
6.4.2 Test 1: initial inspection and commissioning . 17
6.4.3 Test 2: ability to provide the required service under daylight favourable
conditions . 18
6.4.4 Test 3: ability to provide the required service under daylight
unfavourable conditions . 21
6.4.5 Test 4: final inspection . 23
6.4.6 General conclusion . 23
Annex A (informative) Data record sheet for visual inspection . 25
Annex B (informative) Commissioning records sheet . 26
Annex C (informative) Examples of load profiles for comparative tests . 28
C.1 Examples of loads. 28
C.2 Examples of systems . 28
C.3 Examples of load profiles . 29
Annex D (informative) Instruction and data record sheet models (according to a load
profile as proposed in Annex A) . 30
Bibliography . 37

Figure 1 – Test 2, Phase A: initial charge cycles . 19
Figure 2 – Test 2, Phase B: operating cycles . 20
Figure 3 – Test 3, operating cycles . 22

Table 1 – Climatic conditions (example) . 11
Table 2 – Suggested minimum values for IP and IK . 11
Table 3 – Lighting service indexes . 14
Table 4 – Radio / TV service indexes . 15
Table 5 – Refrigeration service indexes . 15
Table 6 – Testing programme . 17
Table A.1 – Data record sheet for visual inspection (example) . 25
Table B.1 – Commissioning records sheet (example) . 26
Table C.1 – Example of loads . 28
Table C.2– Example of small PV-IES loads (~50 Wp) . 28
Table C.3 – Example of medium PV-IES loads (~200 Wp) . 28
Table C.4 – Example of large PV-IES loads (~500 Wp) . 29
Table C.5 – Example of system load profile to perform test on PV-IES . 29
Table D.1 – Overview instruction sheet for daily records (example) . 30
Table D.2 – Record sheet for lighting service (example) . 32
Table D.3 – Record sheet for radio service (example) . 33
Table D.4 – Record sheet for TV service (example) . 34
Table D.5 – Record sheet for refrigeration service (example) . 35
Table D.6 – System daily quality index of service evaluation (example) . 36

– 4 – IEC TS 62257-9-6:2019 RLV © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS
FOR RURAL ELECTRIFICATION –
Part 9-6: Integrated systems – Recommendations for selection
of Photovoltaic Individual Electrification Systems (PV-IES)

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
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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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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6) All users should ensure that they have the latest edition of this publication.
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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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62257-9-6, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.
This second edition of IEC TS 62257-9-6 cancels and replaces the first edition published in
2008. It constitutes a technical revision.
The main technical changes with respect to the previous edition are as follows:
• Removal of the term "small" from the title of the publication and from description of rural
electrification systems.
• Removal of the limits on system voltage and power; these recommendations apply to
systems of all sizes.
This part of IEC 62257 is to be used in conjunction with the IEC 62257 series.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/1279/DTS 82/1533A/RVDTS
Full information on the voting for the approval of this technical specification 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 of IEC 62257 series, under the general title: Renewable energy and hybrid
systems for rural electrification, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.

– 6 – IEC TS 62257-9-6:2019 RLV © IEC 2019
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.
INTRODUCTION
The IEC 62257 series intends to provide to different players involved in rural electrification
projects (such as project implementers, project contractors, project supervisors, installers,
product suppliers, etc.) documents for the setting up of renewable energy and hybrid systems
with a.c. voltage below 500 V, d.c. voltage below 750 V and power below 100 Kva 1 000 V
and d.c. voltage below 1 500 V.
These documents are recommendations:
• to choose the right system for the right place;
• to design the system;
• to ensure product quality and installation quality;
• to operate and maintain the system.
These documents are focused only on rural electrification concentrating on but not specific to
developing countries. They must not be considered as all inclusive to rural electrification. The
documents try to promote the use of renewable energies in rural electrification; they do not
deal with clean mechanisms developments at this time (CO emission, carbon credit, etc.).
Further developments in this field could be introduced in future steps.
This consistent set of documents is best considered as a whole with different parts
corresponding to items for safety, sustainability of systems and at the lowest life cycle cost as
possible. One of the main objectives is to provide the minimum sufficient requirements,
relevant to the field of application that is: small renewable energy and hybrid off-grid systems.
This document and the others of the IEC 62257 series are only guidance and so cannot be
International Standards. Additionally their subject is still under technical development and so
they shall be published as Technical Specifications.
These documents are focused on off-grid electricity access, concentrating on, but not limited
to, areas with a significant fraction of the population living without reliable electric grid access.
They should not be considered as providing complete coverage of all issues related to rural
electrification.
This set of documents is best considered as a whole, with different parts covering topics such
as safety, system design, product quality, installation and maintenance, and the sustainability
of systems aiming at the lowest life cycle cost possible. One of the main objectives is to
provide minimum requirements relevant to renewable energy and hybrid off-grid power
systems.
– 8 – IEC TS 62257-9-6:2019 RLV © IEC 2019
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS
FOR RURAL ELECTRIFICATION –
Part 9-6: Integrated systems – Recommendations for selection
of Photovoltaic Individual Electrification Systems (PV-IES)

1 Scope
The purpose of this part of IEC 62257 is to propose simple selection procedure and cheap,
comparative tests which can be performed in laboratories of developing countries, in order to
identify the most suitable model of small Photovoltaic Individual Electrification Systems (PV-
IES) up to 500 Wp for a particular rural electrification project from a number of products
submitted for test.
It is different from the scope of IEC 62124, Photovoltaic (PV) stand alone systems – Design
verification, which provides guidance for verifying the design of stand-alone PV systems and
indoor and outdoor tests in order to evaluate the performance of PV systems including PV
generator, battery storage and loads such as lights, TV sets, and refrigerators.
The tests provided in this document allow assessment of the performance of PV-IES
according to the requirement of the General Specification (GS) of the project (see
IEC TS 62257-2) and to verify their ability to provide the required service. They should be are
performed locally, as close as possible to the real site operating conditions.
This document is not a type approval standard. It is a technical specification to be used as
guidelines and does not replace any existing IEC standard on PV systems.
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 61215 (all parts), Crystalline silicon terrestrial photovoltaic (PV) modules – Design
qualification and type approval
IEC 61646, Thin-film terrestrial photovoltaic (PV) modules – Design qualification and type
approval
IEC 61730-1, Photovoltaic (PV) module safety qualification – Part 1: Requirements for
construction
IEC 61730-2, Photovoltaic (PV) module safety qualification – Part 2: Requirements for testing
IEC TS 62257-2:20042015, Recommendations for small renewable energy and hybrid
systems for rural electrification – Part 2: From requirements to a range of electrification
systems
IEC TS 62257-4, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 4: System selection and design

IEC TS 62257-5, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC TS 62257-6, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement
IEC TS 62257-7-1, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 7-1: Generators – Photovoltaic arrays generators
IEC TS 62257-8-1:20072018, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 8-1: Selection of batteries and battery management systems for stand-alone
electrification systems – Specific case of automotive flooded lead-acid batteries available in
developing countries
IEC TS 62257-9-3, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 9-3: Integrated system – User interface
IEC TS 62257-9-4, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 9-4: Integrated system – User installation
IEC TS 62257-12-1, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 12-1: Selection of self-ballasted lamps (CFL) for rural electrification
systems and recommendations for household lighting equipment Selection of lamps and
lighting appliances for off-grid electricity systems
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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
3.1.1
cycle
sequence of a discharge followed by a charge or a charge followed by a discharge of a
battery under specified conditions
3.1.2
duration of service
number of hours when a load is powered
3.1.3
fulfilment of service
ratio of a measured provided service to a required service
3.1.4
initial charge
commissioning charge given to a new battery to bring it to the fully charged state
3.1.5
period of service
part of the day when a load is powered

– 10 – IEC TS 62257-9-6:2019 RLV © IEC 2019
3.1.6
reference irradiation
value of irradiation taken in consideration for the design of the system, approved by the
project implementer and specified in the GS of the project
3.1.7
service ratio
extent in which the service required by the GS is fulfilled by the system
3.2 Abbreviated terms
GS general specification for the project
QI quality of service index
TWQI total weighted quality of service
T
DWQI daily weighted quality of service
T
S service ratio under favourable conditions
good
S service ratio under unfavourable conditions
bad
S daily service ratio
d
4 System boundaries
A PV-IES comprises the following elements:
• a PV generator including PV modules and support structure;
• a charge controller;
• a storage system (including battery and associated casing);
• adequate wiring, switches and protective devices (see IEC TS 62257-9-3 and
IEC TS 62257-9-4);
• loads relevant for the required service (such as lamps, TV set, radio set, and refrigerators).
5 System pre-selection
5.1 Services to be provided by the system
The preliminary socio-economic studies shall provide the project developer with information
on the ability of the customers who will benefit from the project to pay for the service provided.
Then, the project developer shall define within the GS the range of services to be provided as
described in IEC TS 62257-2 as well as the relative priority of the services to be provided (TV,
lighting, etc.)
5.2 Specification of a model
5.2.1 General operating conditions
The project implementer shall define the operating conditions to which the PV-IES can be
subjected. Examples of such conditions are given in Table 1.

Table 1 – Climatic conditions (example)
Nominal operating range Storage – Transport
Temperature –10 °C to +50 °C –40 °C to +80 °C
Humidity at 28 °C 5 % to 95 %
Atmospheric pressure 860 hPa to 1 060 hPa

5.2.2 Design
For the part of the project which will be implemented through Individual Electrification
Systems, the project developer shall size a range of PV IES able to provide the required
service under the specified operating conditions (see IEC TS 62257-2). The project
implementer could either:
• specify complete integrated systems, or
• specify the different components for PV-IES in order to realize the integration of these
components through its own system design.
In addition, the project developer shall set up the requirements for the loads relevant for the
service to be provided (such as lamps, TV set, radio set, and refrigerator).
5.2.3 Components requirements
The components of the PV-IES shall comply with the relevant IEC standards and/or the
relevant local regulations if any.
For the selection of batteries, tests recommended in IEC TS 62257-8-1 shall apply and for the
selection of lamps, tests recommended in IEC TS 62257-12-1 shall apply.
5.2.4 Safety issues
The project developer shall define the IP degree and IK code of the expected products.
Table 2 gives some values that could be considered as a minimum.
Table 2 – Suggested minimum values for IP and IK
Protection degree Minimum suggested value
IP 34
IK 8
Safety rules shall comply with IEC TS 62257-5.
5.2.5 Installation rules
The complete installation shall comply with IEC TS 62257-7-1 and IEC TS 62257-9-4 and any
local wiring codes.
5.2.6 Operation and maintenance rules
The systems shall be designed in order that operation and maintenance may be performed in
accordance with the specifications given in IEC TS 62257-6.

– 12 – IEC TS 62257-9-6:2019 RLV © IEC 2019
5.2.7 Documentation and marking
A manual shall also be provided including PV-IES installation and operating guidelines such
as:
• initial operations before first use;
• instructions to use the PV-IES properly;
• mounting the PV module;
• charging instructions;
• maintenance and troubleshooting instructions.
5.3 Pre-selection process
5.3.1 Elements of the GS to be provided to potential suppliers
The project implementer shall supply the annual locally available solar irradiation curve.
NOTE This information could be provided through available laboratory data or through local measurements
performed with a reference cell that will be used afterwards for the comparative tests.
This information as well as the requirements defined in 5.1 and 5.2 shall be provided to
potential suppliers in order to receive proposals for relevant products.
The project implementer could:
• provide load requirements and let the suppliers provide systems to supply the load, or
• provide a complete PV-IES system specification, in order to source complete integrated
PV-IES, or
• provide components requirements in order to source separately the different components
of a PV-IES and realize the integration of these components.
5.3.2 Answers to be provided by potential suppliers
The supplier of the PV-IES and/or of the components shall prove that the PV-IES and/or the
components comply with the relevant IEC standards and IEC 62257 technical specifications.
A technical sheet shall be provided by the supplier in order to demonstrate the ability of its
product to match the requirements defined in 5.1 and 5.2.
5.3.3 Pre-selection criteria
The performances claimed by the manufacturer shall be compared to the performances
required by the GS in order to make a pre-selection of available products.
The following general criteria can be used as an initial help for product pre-selection:
• services characteristics claimed by the manufacturer (duration of service and fulfillment of
service);
• conformity of the modules with the following IEC standards: IEC 61215 series, IEC 61646,
and IEC 61730-1 and IEC 61730-2;
• conformity of the batteries, lamps, etc., with the relevant IEC standards and pre-selection
process of potential products as recommended in the IEC TS 62257 series;
• battery casing characteristics.
A short list of products potentially able to match the requirements of the GS shall be set up by
the project implementer.
6 Comparative tests
6.1 General
After the pre-selection process, samples of products of the short list shall be processed
through comparative technical tests.
IMPORTANT: All the pre-selected systems shall be tested simultaneously in the same local
conditions in order to ensure that they are tested under the same environmental parameters
(irradiation, humidity, temperature, etc.).
Tests could be performed either in outdoor conditions, in local laboratories or in site
conditions (on future customer homes for instance). The systems installation rules provided in
the GS are also applicable to test installations.
6.2 Service requirements
Pre-selected models shall be examined to ensure that they will provide the required services
mentioned in the GS according to the load profile used for the design of the system.
A service is defined by:
• The types of appliances/loads powered by the system (such as lamps, TV set, etc.);
• For each type of appliance:
– the number of appliances that can be simultaneously powered;
– the daily duration of the power supply;
– the fulfilment of the provided service.
6.3 Service quality index
A Quality of service Index (QI) of a system is based on one of these two terms:
• d = duration index, d, is the ratio of the measured daily duration of service compared to the
required daily duration of service;
• f = fulfilment index, f, is the ratio of the measured performance (illuminance for lamps,
temperature for refrigerator, etc.) compared to a reference level required by the GS.
For the different considered services the QI takes into account either, d, or, f:
– for lighting: f;
– for radio: d;
– for TV: d;
– for refrigeration: f.
The systems shall be compared through a Total Weighted Quality of service Index (TWQI )
T
calculated on the basis of observations and measurements performed during, T, days of
comparative tests.
The TWQI and service ratio (S) are calculated as follows:
T
a) Step 1: for each service, calculation every day of either “duration” or “fulfilment”
indexes
The following Tables 3 to 5 illustrate the necessary index evaluation data and calculation
rules.
– 14 – IEC TS 62257-9-6:2019 RLV © IEC 2019
Table 3 – Lighting service indexes
Service Lighting
Requirements Number of lamps  N

L
Daily duration of service per lamp (h) D

L
Illuminance (lux)  Q
Duration index Fulfilment index
Measured Total Fulfilment index
illuminance measured
illuminance for
every hour of
service
lux lux
see Note 1 see Note 2
Not relevant
For lamp 1:
q
L1
j=D i=n
L
For lamp 2: i =n
q
L
∑ ∑
q i
L2 q
L
∑ j=1 i=1
i
f =
Lighting
… i =1
n ×Q
For lamp i:
q
Li
NOTE 1 n = number of illuminance measurements at each hour of service; n ≤ N
.
L
NOTE 2 In order to limit the number of measurements, if N > 3, n could be limited to n = 3.
L
j=D i=3
L
q
∑ ∑ L
i
j=1 i=1
In this case the formula becomes:
f =
Lighting
3 ×Q
In this example only 3 lamps out of N are measured every hour. Generally it is preferable to

L
ensure that all the lamps have been equally monitored at the end of the test.
A complete example for the lighting service is given in Table D.2.

Table 4 – Radio / TV service indexes
Service Radio (or TV) (see Note)
Requirements Number of radio sets N

R
Daily duration of service per set (h) D

R
Duration index Fulfilment index
Total required Measured daily Total measured Duration index
daily duration of duration of daily duration of
service service service
h h h
For set 1: Not relevant
i =N
d
R
R1
i =N
R
d
∑ R
i
N × D d
∑ R
R R i
i =1
d =
Radio
i =1
N × D
R R
For set N:
d
RN
NOTE In the TV set case, subscript R should be changed to T.

Table 5 – Refrigeration service indexes
Service Refrigeration
Requirements Number of refrigerators N (N =1 in most cases)
F F
Daily duration of service (h) Not relevant
Temperature (°C) Temperature reference: T°
Duration index Fulfilment index
Measured Average Fulfilment index
measured
temperature: Θ
temperature
deviation
Not relevant
°C
°C
See Note 1
measure 1
i =n
 
∆θ = Θ – T
i =n
1 1  
∆θ
∑ i
 
∆θ
measure 2
∑ i
i =1
f = 1−  
i =1
∆θ
2  n× T 
n
 
…
 
 
measure n
∆θ
n
NOTE n = number of temperature measurements.

b) Step 2: for each tested system, calculation of a DWQIT
For a given service X, the Quality of service Index (QI) is:
= d
QI
X X
or
= f
QI .
X X
If the project implementer does not give the same priority to the services, he could
determine some “weighting coefficients”, k, reflecting the relative importance assigned to
the different services provided.

– 16 – IEC TS 62257-9-6:2019 RLV © IEC 2019
The relative priority of the different services shall be determined by a socio-economic
study (see 5.1).
Using these weighting coefficients, a Daily Weighted Quality Index (DWQI) shall be
calculated for a system, as given in the following formula (1). For a given day, t, and for X
types of services:
i =X
DWQI = k × QI (1)
t
∑ i i
i =1
– For lamps: k = k
Lighting L
– For radios: k = k
Radio R
– For TVs: k = k
TV T
– For refrigerators: k = k
Fridge F
Using this hypothesis, for a system providing all the mentioned services the DWQI for a
day, t, is:
DWQI = (k × QI ) + (k × QI ) + (k × QI ) + (k × QI )
t L Lighting R Radio T TV F Fridge
It is the project developer’s responsibility to determine the k coefficients according to the
importance he gives to each service.
NOTE As an example, a convenient rule to determine values for the weighting coefficient,
k, may be based on the daily required duration of service (see Table D.6).
c) Step 3: for each tested system, calculation of a TWQI
T
On the complete duration of the test, a TWQI shall be determined according to the
T
following formula (2). For a test performed on, T, days:
t =T
TWQI = DWQI (2)
t
T ∑
t =0
i =X
with TWQI = T × k (case where all service quality indexes are equal to 1)
,max
T ∑ i
i =1
d) Step 4: for each tested system, calculation of a service ratio, S
The laboratory operator shall calculate the maximum value of the TWQI in the conditions

T
of the test.
Then he shall calculate for each system the service ratio by the following formula (3):
TWQI
T,act
S = (3)
TWQI
T,max
where
TWQI : results of TWQI
;
T,act T
and TWQI : maximum value of TWQI
T,max T
This ratio expresses to what extent the system is able to provide the service required by
the GS.
6.4 Testing programme
6.4.1 General
The comparative tests include a set of 4 tests as indicated in Table 6.

The complete set of tests is intended to be performed within a period of 90 days during the
appropriate season as identified during the project preliminary studies and according to the
quality of service specified by the project developer (see IEC TS 62257-2:2015, Annex C).
The system shall be tested under two daylight conditions:
• Daylight favourable conditions: in this configuration local irradiation is at least 90 % of the
reference value given in the GS.
• Daylight unfavourable conditions: in this configuration, the irradiation taken into account
shall be determined by the project implementer as a percentage of the reference value
given in the GS (such as for example the irradiation during the rainy season).
Table 6 – Testing programme
Test 1 Test 2 Test 3 Test 4
Ability to provide Ability to recover Final inspection
Initial inspection
the required the required
and commissioning
service under service under
daylight daylight
Favourable Unfavourable
conditions conditions
See 6.4.2 See 6.4.3 See 6.4.4 See 6.4.5

6.4.2 Test 1: initial inspection and commissioning
6.4.2.1 General
The purpose of the different inspection tests (Test 1 and Test 4) is to assess the evolution /
degradation of the conditions of the different parts of the product during the test period,
especially casings, lamps, cables and PV modules.
The initial inspection is intended to record all necessary details of each sample of each pre-
selected model and identify the sample for the duration of all tests. It will also verify that the
sample has been supplied with all necessary items and components required by the GS.
In Test 1, after the initial inspection, the system shall be commissioned.
As much information as possible concerning each sample to be tested should be recorded.
6.4.2.2 Sampling
Three samples of each model are required. For small projects, if the cost of the testing is too
high, the sampling could be limited to two samples of each model.
A test item number shall be assigned to each sample and used in all data sheets and records
to avoid confusing sample results. It is recommended that the unit should be photographed in
such a way that all major accessible components are recorded.
6.4.2.3 Operation
The initial inspection shall be performed in two steps:
• unpacking step; and
• installation step.
– 18 – IEC TS 62257-9-6:2019 RLV © IEC 2019
A list (non comprehensive) of items to be checked and recorded during these two periods is
provided as an example in Annex A.
After the initial inspection and installation of the system, commissioning shall be performed
(an example of a commissioning sheet is given in Annex B).
6.4.2.4 Results
The pass criteria is based on the following:
For each sample:
• there shall be no visual evidence of a major defect on any component; and
• the sample is complete; and
• the installed system has been commissioned satisfactorily.
The fail criteria is based on the following:
For each sample:
• there is evidence of a major defect; or
• some components are missing or incorrect; or
• the system cannot be installed properly according to the GS requirements.
It is up to the project implementer to determine whether he will accept a certain model if one
or more samples have failed this initial visual inspection.
6.4.3 Test 2: ability to provide the required service under daylight favourable
conditions
6.4.3.1 General
The purpose of this test is to check the ability of a PV-IES product to perform the required
service under daylight sunny conditions considered as favorable.
A reference load profile shall be established for the tests according to the service required in
the GS. Some examples of such load profiles are given in Annex C.
6.4.3.2 Sampling
Each model for which the three all samples passed Test 1 shall go through to Test 2.
6.4.3.3 Equipment
To perform Test 2 the following equipment shall be necessary:
• A power system to supply energy to all test instruments.
NOTE 1 If the testing is performed in a laboratory connected to a grid, no additional power
system is necessary. If the testing is performed on site, a dedicated power system is
necessary to supply energy to testing devices.
• A reference device (such as a reference PV module, pyrheliometer, etc.) to assess and
record the daily irradiation.
NOTE 2 This device may also be initially used to assess the value of the irradiation to be
taken in account for the design of the systems.

• Test instruments:
– Programmable controllers to monitor the load profiles. If not, the loads may be
switched on/off manually.
– One (or several) illuminance measurement box(es) (see IEC TS 62257-12-1).
– A thermometer, preferably electronic.
6.4.3.4 Operation
6.4.3.4.1 General
Test 2 shall be performed according to the following phases:
6.4.3.4.2 Phase A: initial preparation
This phase is dedicated to charge the battery before testing the ability of the system to
perform the required service.
The initial charge is controlled by the charge controller of the PV-IES without any manual
intervention. During the initial charge, all the loads shall be switched off.
The initial charge shall be performed for, x days (x ≥ 5) until 5 "good sunny days" have been
recorded. A "good sunny day" is defined as a day when irradiation is equal to or greater than
90 % of the reference irradiation defined in the GS (considered as favourable conditions).
The following Figure 1 illustrates the Phase A cycles:
START Test 2,
Phase A
t = 0
Sunrise
Charge battery
under dayligh
...