IEC TS 62257-2:2004

IEC/TS 62257-2 ®
Edition 1.0 2004-05
TECHNICAL
SPECIFICATION
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 2: From requirements to a range of electrification systems

IEC/TS 62257-2:2004(E)
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IEC/TS 62257-2 ®
Edition 1.0 2004-05
TECHNICAL
SPECIFICATION
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 2: From requirements to a range of electrification systems

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 27.160; 27.180 ISBN 2-8318-7525-0

– 2 – TS 62257-2  IEC:2004(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7

1 Scope.8
2 Normative references.8
3 Terms and definitions .9
4 Methodology for non technical preliminary studies .10
4.1 Place and role of preliminary studies in a decentralized rural electrification
project.10
4.2 Specifications of the preliminary study .10
4.3 The stages of a socio-economic study.15
5 Classification of electrification systems .15
5.1 Introduction to a range of systems .15
5.2 Users requirements .16
5.3 Typology of qualitative requirements .16
5.4 Typology of quantitative requirements .17
5.5 Classification for electricity services provided.18
5.6 Assisted selection of production subsystem .18
5.7 Typology of decentralized electrification systems .18
6 Electrification systems architecture .21
6.1 General .21
6.2 General presentation of isolated electrification systems.21
6.3 Combining subsystems .22
6.4 Functional diagrams .24
6.5 Related references .25
6.6 Limits between production, distribution and demand/application subsystems .25
6.7 Summary of the different electrification system types .25

Annex A (informative) Stages of a socio-economic study (see Clause 4).26
A.1 General .26
A.2 Preparation phase .26
A.3 Drawing up of the questionnaires, choice of surveyors and choice of sample .27
A.4 Conducting the survey - Analysis of the results.27
A.5 Extrapolation of the results .27

Annex B (informative) Analysis of the type of receivers installed versus types of use and
demonstrating seasonable variability (where applicable) (see Clause 5).28
B.1 Domestic use.28
B.2 Analysis of the type of receivers versus usage types .30

Annex C (informative) Supply quality indicators for isolated electrification systems (see
Clause 5) .32

TS 62257-2  IEC:2004(E) – 3 –
Annex D (informative) Assisted selection of production subsystem (see Clause 5) .34
D.1 Characteristics of possible production subsystems .34
D.2 Assisted selection of a decentralized production system suited to the requirement.34

Annex E (informative) Functional diagrams (See Clause 6).36
E.1 Glossary of symbols.36
E.2 Architectures of systems.37

Figure 1 – Example of the content of a non technical preliminary study .11
Figure 2 – Systems architecture and dispatchable energy.19
Figure 3 – General configuration of an electrification system.23
Figure A.1 – Flowchart of the stages of a socio economic study.26
Figure D.1 – Better adequacy of production subsystems solutions with supply
availability and daily duration of service .35
Figure E.1 – Type T I-a system .38
Figure E.2 – Type T I-b system .39
Figure E.3 – Type T I-c system .40
Figure E.4 – Type T I-d system .41
Figure E.5 – Type T I system .43
Figure E.6 – Type T I-a system .45
Figure E.7 – Type T I-b system .46
Figure E.8 – Type T I system .48
Figure E.9 – Type T I system .49
Figure E.10 – Type T I system .50
Figure E.11 – General architecture of a micropower plant supplying a microgrid .52
Figure E.12 – Type T C system.53
Figure E.13 – Type T C-a system .55
Figure E.14 – Type T C-b system.56
Figure E.15 – Type T C-a system.58
Figure E.16 – Type T C-b system.59
Figure E.17 – Type T C system.61
Figure E.18 – Type T C system .63
Table 1 – Application types and types of uses.16
Table 2 – Expected quality of the supply.17
Table 3 – Synthesis of quantitative requirements/category (examples of type of user
and use) .17
Table 4 – Typology of decentralized electrification systems.18
Table 5 – Preliminary range of relevant (as a minimum) decentralized electrification
systems .20
Table 6 – Recapitulation of characteristics of different types of isolated electrification
systems .25
Table C.1 – Combined categorization .32
Table C.2 – Service specification (example) .33

– 4 – TS 62257-2  IEC:2004(E)
Table D.1 – Principles and characteristics of production subsystems .34
Table E.1 – Glossary of symbols .36
Table E.2 – List of cases, type T I.37
Table E.3 – List of cases, type T I.44
Table E.4 – List of cases, type T C .54
Table E.5 – List of cases, type T C .57
TS 62257-2  IEC:2004(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 2: From requirements to a range of electrification systems

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
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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.
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 62257-2, which is a technical specification, has been prepared by IEC technical committee
82: Solar photovoltaic energy systems.
This technical specification is to be used in conjunction with IEC 62257 series.

– 6 – TS 62257-2  IEC:2004(E)
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/302/DTS 82/320/RVC
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 publication has been drafted in accordance with the ISO/IEC Directives, Part 2. It was
developed in cooperation with other IEC technical committees and subcommittees dealing with
renewable energies and related matters, namely technical committee 21 ("Secondary cells and
batteries"), subcommittee 21A ("Secondary cells and batteries containing alkaline or other non-
acid electrolytes"), technical committee 64 ("Electrical installations and protection against
electric shock"), technical committee 88 ("Wind turbines"), and others.
This document is based on IEC/PAS 62111(1999); it cancels and replaces the relevant parts of
IEC/PAS 62111.
The committee has decided that the contents of this publication will remain unchanged until
2007. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

TS 62257-2  IEC:2004(E) – 7 –
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, etc.)
documents for the setting up of renewable energy and hybrid systems with AC voltage below
500 V, DC voltage below 50 V and power below 50 kVA.
These documents are recommendations:
a) to choose the right system for the right place,
b) to design the system,
c) to operate and maintain the system.
These documents are focused only on rural electrification concentrating on but not specific to
developing countries. They shall 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 development 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.
The purpose of this part of the IEC 62257 series is to propose a range of renewable energy
based electrification systems able to meet the requirements of customers identified in the field
of decentralized rural electrification projects.

– 8 – TS 62257-2  IEC:2004(E)
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 2: From requirements to a range of electrification systems

1 Scope
The scope of this part of the IEC 62257 series is to propose a methodological approach for the
setting up and carrying out of socio-economic studies as part of the framework of decentralized
rural electrification projects. It is addressed to project teams and in particular to experts in
charge of socio-economic studies in international projects.
The amount of detail gathered and the requisite number of experts needed would depend on
the scale of the proposed project. For large projects involving many households, a detailed
study would be required, for a project which involves a single or few households, the study
could be truncated.
The information coming from such preliminary studies could be used for several purposes,
such as more complete economic and financial studies of the electrification project.
This part of IEC 62257 also provides some structures as technical solutions that could be
recommended, depending on the qualitative and quantitative energy demands, consistent with
the needs and financial situation of the customers.
Then, in relation with each model of the proposed range of systems, electrical architectures are
proposed to technical project managers to assist in designing the systems.
2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60617 (all parts)[DB] , Graphical symbols for diagrams
IEC 62257-1, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 1: General introduction to rural electrification
IEC 62257-3, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 3: Project development and management
IEC 62257-4, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 4: System selection and design
IEC 62257-5, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 5: Safety rules
___________
“DB” refers to the IEC on-line database.
Under consideration.
TS 62257-2  IEC:2004(E) – 9 –
IEC 62257-6, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement
IEC 62257-7, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 7: Technical specifications: generators
IEC 62257-8, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 8: Technical specifications: batteries and converters
IEC 62257-9, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 9: Technical specifications: integrated systems
IEC 62257-10, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 10: Technical specifications: energy manager
IEC 62257-11, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 11: Technical specifications: considerations for grid connection
IEC 62257-12, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 12: Other topics
3 Terms and definitions
For the purposes of this part of the IEC 62257 series, the following terms and definitions apply.
3.1
REN
renewable energy
3.2
hybrid system
multi-sources system with at least two kinds of technologies
3.3
dispatchable power system
source, generator, system is dispatchable if delivered power is available at any specified time
(for example, a genset is a dispatchable system, REN generator is usually a non dispatchable
power system)
3.4
non dispatchable power system
a non dispatchable system is resource dependent; power might not be available at a specified
time
3.5
storage
storage of energy produced by one of the generators of the system and which can be
reconverted through the system to electricity
3.6
micropower plant
power plant that produces less than 50 kVA through the use of a single resource or hybrid
system
___________
Under consideration.
– 10 – TS 62257-2  IEC:2004(E)
3.7
microgrid
grid that transfers a capacity level less than 50 kVA and powered by a micropower plant
3.8
Individual Electrification System
IES
micropower plant system that supplies electricity to one consumption point usually with a single
energy resource point
3.9
Collective Electrification System
CES
micropower plant and microgrid that supplies electricity to multiple consumption points using a
single or multiple energy resource points
3.10
isolated site
electric characteristic to define a specific location not currently connected to a national/regional
grid
3.11
remote site/area
geographic characteristic to define a specific location far from developed infrastructures,
specifically energy distribution
4 Methodology for non technical preliminary studies
4.1 Place and role of preliminary studies in a decentralized rural electrification project
It is strongly recommended that it is unwise to launch an electrification project against the
wishes of the local institutions and populations. A good understanding of the needs and wishes
of the local populations is recommended, to know what is their demand, their capacity and
willingness to pay for a modern energy service.
If all the socio-economic data are available, they have to be properly collected and processed
for this purpose.
If not, a preliminary study is recommended that will be the first stage in the establishment of a
feasibility study for a decentralized rural electrification project. Its role is to allow a better
understanding of the areas concerned by the various project experts and such a study would
make available some of the data needed for technical evaluations, economic, financial and
legal analyses, and for the carrying out of the project in general.
In this Clause, a method is suggested to obtain the various information needed.
Some of the information described in the following section might be obtained from govern-
mental organizations prior to specific sites visits.
4.2 Specifications of the preliminary study
4.2.1 General
A socio-economic study shall provide a certain amount of data to the experts in charge of the
financial, techno-economic and organizational studies. It also allows a better understanding of
the global environment of the project and can provide information to the community about the
scope of the project.
TS 62257-2  IEC:2004(E) – 11 –
The following subclauses suggest some considerations concerning data to be collected and
analyzed in consideration with:
• general information on the environment of the project,
• techno economic study,
• organizational study,
• financial analysis.
Figure 1 is an illustration of the main topics that should be investigated in the socio-economic
study.
-
Preliminary study
Organisational study
General information on the
- possible sources of financing

environment of the project
- existing local infrastructures

- private sector dynamics
- sociological data
- community-level dynamics
- community’s priorities for development
- public-sector dynamics
- economic activity
- development projects under way in the region

- externalities (environmental impact)

- level of education
Financial analysis
Techno - economic study
- number of customers and
variations in time
- average selling price
- demographic and geographic data

- access fee for electricity
- the load distr ibution curve of the village or the

distribution of customers per service
- fuel price
IEC  598/04
Figure 1 – Example of the content of a non technical preliminary study
4.2.2 General data for a better understanding of the project environment
The following topics should be considered by project contractors. It’s their role to determine the
relevant importance of each of these categories in regard to a specific project or programme.
4.2.2.1 Sociological data
This data is important for an understanding of the local population. It is essential to look at the
organizational, cultural and ethnological structures of the society. In particular, one should
investigate the way of life, the sanitary conditions, the national and local languages, the level of
education and literacy, the technical sophistication level and the presence of organizations and
associations. In addition, the role of male and female in the social organization of the village
shall be taken into account.
4.2.2.2 The communities’ priorities for development
It is important to understand the population’s opinions of their village. What are their priorities
for improvement in their daily life? (Such as water pumping, construction of a hospital, of a
school, communications infrastructure, electricity, etc.).
In the case of a rural electrification project, what are the priorities for the village as expressed
by the population and the local authorities?

– 12 – TS 62257-2  IEC:2004(E)
4.2.2.3 Economic activities and possible development
Knowledge of the economic activities in the community allows a better general understanding
of the environment of the project; it also helps in understanding the dynamics of local
development, in order to evaluate the evolution of demand in energy in the coming years.
One can compile the economic activities of the village (commerce, handicrafts, animal
husbandry, agriculture, etc.) and look at their relative importance. It would also be useful to
look at potential activities due to electricity.
4.2.2.4 The development projects under way in the region
One should look at the local development projects under way, who are the instigators and who
are the beneficiaries, what are the impacts on the population, and what would be the impacts
on a future electrification project.
4.2.2.5 Environmental considerations
One of the clear drivers in the use of renewable technology is the favorable impact of these
systems on the environment as compared to the conventional sources, primarily diesel and grid
extension. The impact of any technology choice on the environment, from a carbon, plant
footprint, noise and visual impact should be assessed. Understanding the desires of the local
participants will be important in this endeavor.
4.2.3 Necessary data for the techno-economic study
Although this information is not strictly in the domain of the socio-economic expert, it shall be
collected in the initial phases of any analysis as it is essential to the techno-economic study.
The socio-economic expert is therefore asked to collect this data, being usually the first project
person to visit a rural community.
4.2.3.1 Geographic and demographic data
In particular one shall obtain the geographical coordinates of the village, its topography, local
fauna, and the geographical distribution of the inhabitants. The geographic layout of the
community is important because it impacts the economics of meeting the power requirements
for the community. If the community is widely dispersed, the cost of a local distribution network
may be prohibitive, at which point individual home systems or small cluster systems may be the
most cost-effective solutions. The analysis will require specification of the location, power, and
energy requirements of each load. It is also important to obtain an understanding of the
acceptance of different qualities of service that these electrification options offer. If possible,
one should collect data on the climate, local natural resources, site transportation issues and
other important sighting issues such as land ownership and right of way issues.
4.2.3.2 Human resources
The personnel resources available in the community, region and country shall be considered
when conducting an analysis for renewable based power systems. The infrastructure required
for the project installation, long term operation, and system maintenance shall be in place to
insure its long-term sustainability. In most cases, a multi layer infrastructure is required, a
local system operator who is able to address short term incidents, a regional service center
capable of conducting system repair and component assessment and a country or globally
regional center that can provide timely replacement of major components and detailed service.
Without a specified institutional framework, it will be impossible to provide a quality level of
service at a cost that can be sustainable over the life of the project. The whole infrastructure
framework relies on people with the right level of training and equipment to perform their
specified tasks in the right geographic area with enough systems to guarantee a successful
business model. If the infrastructure is not currently in place, care shall be taken to investigate
whether the resources are available to create one.

TS 62257-2 © IEC:2004(E) – 13 –
4.2.3.3 Energy, resources assessments
Data on the local (renewable) energy sources such as wind, insolation, biomass and hydraulic
potential should be collected. If a sufficient amount of reliable data is not available, the project
should be postponed until the necessary data have been collected. For wind and solar energy,
a measurement program may be necessary. For wind measurements, a duration of at least one
full year or the ability to comfortably correlate the data to other long-term data collection sites,
is recommended. Information on the daily or seasonal resource pattern is also important in the
assessment of the available resource. Modern site assessment techniques should be utilized to
establish the best possible prediction of the resource and the energy production potential,
including the use of resource assessment modeling techniques such as the Wind Atlas
Analysis and Application Program (WASP) Riso National Laboratories, Denmark; MesoMap,
True Wind Solutions, United States; and the Wind Resource Assessment and Mapping System
(WRAMS), National renewable Energy Laboratory, United States. This data can then be used
in performance simulation models such as RAPSIM, Australia; RETScreen, Canada; HOMER,
Hybrid2, PVSYST, and Wattsun, United States. At locations without electric service, it will also
be important to obtain an assessment of all of the electrification options for the community or
dwelling in question. This would include information like the distance to any existing distribution
network and the cost of diesel fuel transported to the site.
4.2.3.4 Environmental conditions, climate
Data on the local environment and climate should be collected. For warm climates with high
temperatures, humidity and possibly corrosive environments may influence design criteria,
choice of material and systems layout. For cold climates with low temperatures, icing and again
possible corrosive environment may, in different ways, influence design criteria, choice of
material, systems layout and performance. Altitude may also be an important parameter. Local
conditions may also influence transport, installation and access to the site as well as operation
and maintenance costs. Extreme conditions such as earthquakes, floods and hurricanes may
influence design criteria and expected systems lifetime. Data on all these matters should be
collected and, if possible considered in relation to any national and/or international standard.
4.2.3.5 Existing energy supply
The structure of the existing energy supply in terms of fuel, gas, wood, candles and other
sources should be mapped with respect to sources, amounts, availability and costs. Existing
infrastructure in terms of power plants, fuel storage and distribution lines should be listed and
specified in considerable detail. Costs and metering principles should be accounted for, and
subsidies, if any, on the existing energy supply should be accounted for. Special care should
be taken in the determination the real cost of diesel fuel delivered to an existing diesel power
station. The number of hours of service per day and the customer’s impression of the level of
service are important factors to consider for any existing power stations.
4.2.3.6 Present and future consumer demands
The expected loads in a community, as well as the projected growth, or reduction, of those
loads will impact the specification and configuration of the hybrid system. Determining the
initial loads and the growth projections can be very difficult, and is often based on historical
values for similar situations. It is very clear that the load and projected growth have a clear
relation to system design and the life-cycle cost of energy for systems providing various levels
of service. The quality of the electric service, the number of hours per day the system is
expected to operate, and whether there are large inductive loads, such as motors, need to be
considered. Investigation should also be made into areas of potential power use, for example
animal driven agricultural water pumps that could be electrified or grain drying operations that
could be converted to biogas.
4.2.4 Necessary data for the financial analysis
The financial expert needs a number of data to make his analysis, and the socio-economic
expert shall provide them. For the financial analysis, one shall know the following:

– 14 – TS 62257-2  IEC:2004(E)
4.2.4.1 Number of customers and variation in time
This data is deduced from the data on the demand expressed by the population for a modern
energy service. In order to evaluate the potential number of customers at the beginning of the
project, one shall take into account the social demand (willingness to pay) and the capacity to
pay.
To estimate the variations in the number of customers with time, one shall know the
demographic growth, and in particular the growth in the number of households (or the average
number of persons per household).
4.2.4.2 Availability, willingness to pay
To determine the average selling price for implementing the financial plan, one generally uses
the average capacity to pay determined in the previous stage. However it is preferable to
determine the willingness to pay of customers for a given service and the distribution of
potential customers per service. One then determines the average selling price for each
service.
4.2.4.3 Potential sources of financing for the user
It is important to know the various financial institutions and the habits of the local population in
their money management. Understanding of their sources of income, and in particular the
regularity of their income, allows for better customer management. Questions put to the
households lead to knowledge of their preferences and the social acceptability of the different
payment methods envisaged.
4.2.4.4 Institutional organizations: potential sources for financing
International and national organizations are potential sources for financing. In relation with the
specific goals of the project, it is recommended to have a look to the updated list of these
organizations (governmental and NGOs ) in order to request their support. Such institutions or
organizations can be used to fill the gap between the true project cost and the income coming
from the local community. Some projects can be financed only by the local resources, but most
of them require assistance from such organizations, commonly the case in developing
countries.
4.2.4.5 Connection charge for electricity (initial equipment)
It is important to know if an access fee for electricity can be accepted by the population. If so,
what is the adequate fee and what is the willingness to pay of the populations for this access
fee?
4.2.5 Necessary data for the organizational study
4.2.5.1 Existing local infrastructures
In order to optimize any decentralized electrification system, one needs to know the transport
and communication infrastructures in place. It is necessary to know if they operate all year
round (if for example one needs to supply petrol to the village).
One needs to know the distance to the national grid to evaluate the social acceptability of a
decentralized system, what are the existing equipments and services available, what electricity
supply (if any) the population has access to, and the available communication infrastructures.

TS 62257-2  IEC:2004(E) – 15 –
4.2.5.2 Private sector dynamics
Private sector dynamics can be evaluated through the number of commerce and handicrafts in
the village, as well as the local technical skills: presence of electrical technicians, mechanics,
and other activities, etc.
This gives a measure of the capacity of the private sector to support electrification projects in
terms of customer management, or even in terms of investment. It is therefore interesting to
note the private initiatives under way, such as private micro-grids, battery charging, rental of
solar home systems, etc.
4.2.5.3 Community-level dynamics
The capacity for initiative and organization of the local communities should be looked at. This
may be evaluated by noting the presence (or absence) of structured local organizations or
associations: professional guilds, community infrastructure associations, socio-cultural
associations, etc. It is also essential to note the presence of community-level electrification
projects, such as micro-grids.
Generally, the fewer of these organizations are present, the lower will be the organizational
capacity of the community. In this case, it is difficult to imagine a management of the
electrification project purely on a community level.
4.2.5.4 Public sector dynamics
This dynamic can be evaluated by looking at the public sector (state, local authorities) projects
under way in the village. If they are few, one can conclude that generally speaking, a public
sector management approach for electrification projects is not appropriate.
4.2.5.5 Local governmental Issues
There will be a number of local and federal governmental issues that will have to be assessed
prior to project implementation. Items include financing and subsidy issues, responsibility for
system operational status, import tariffs, land use issues and power production legislation and
regulation. In many cases, governmental barriers to the use of new and renewable rural
electrification technology are the hardest to overcome and result in the most project delays.
4.2.5.6 Institutional organizations
International and national organizations are potential sources for organization support. In
relation with the specific goals of the project, it is possible to find organizations with specific
experience, for example business development.
4.3 The stages of a socio-economic study
The main steps recommended to be followed for the carrying out of a socio economic study are
presented at the end of the present document as Annex A.
5 Classific
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