Technical Standards for Solar Home Systems (SHS)

Field experience with PV rural electrification has shown that the performance of solar home systems SHSs is not always entirely satisfactory. However, in-depth studies of the problems encountered in existing installations have revealed that the pure solar part, i.e. the PV generator, rarely fails. The PV system is often initially blamed for the failure but, when things go wrong, it is usually the other PV system components or the appliances which are powered by the PV generator which are found to have failed. This is mainly because, while PV modules are highly standardised and certified using internationally validated procedures, there are no equivalent standards and procedures available for balance-of-system components, component matching or installation quality, even though the quality of these components has a dramatic influence on user satisfaction and operating costs.

The "Instituto de Energía Solar" at the "Universidad Politécnica de Madrid" prepared a report that is designed to form the basis for a Universal Standard for SHS. It is based on a world-wide review of existing technical standards for SHSs (see Annex 1), which has revealed a large number of inconsistencies¹ between these standards. In particular, different approaches have been found for system sizing, and for specifying types of PV modules, the number of cells in PV modules, types of battery, charge regulation voltage set points, operational information for users, voltage drops, safety measurements and ballast, cables and connectors requirements.

In preparing this report, each of the different approaches has been assessed using scientific reasoning, empirical evidence and the personal experience of the authors. To a large extent, the standard proposed here can therefore be considered as Universal, because each of the existing standards has provided extremely valuable inputs. Moreover, a first draft version has been circulated amongst a wide number of experts from different countries (see Annex 2), and their invaluable comments have also been taken into account.

In parallel with the above mentioned review of existing standards, an enquiry was carried out to identify the concerns of key persons involved in PV rural electrification programmes, and to seek their views on the usefulness and implementation possibilities of a Universal Standard for SHSs. The need for flexibility, which would allow it to be adapted to the particular conditions of each country (climate, local manufacture, internal market, indigenous capabilities, etc.), has been the most outstanding demand. In order to meet this demand, the requirements presented in this standard have been classified into three categories: Compulsory, Recommended and Suggested.

Compulsory requirements (C) are those which could directly affect safety or reliability. Failure to meet these requirements could lead to personal injuries or to SHS failure, and they are therefore intended to constitute a minimum core of requirements which must be fulfilled anywhere in the world.

Recommended requirements (R) are those which would normally lead to system optimisation. Most of these requirements are universally applicable, and failure to meet them would normally lead to a cost increase. However, because economic considerations can depend on local conditions, the application of these requirements must be reviewed for each particular case.

Suggested requirements (S) are those which might be expected to produce a sound installation. However, it should be noted that any judgement of soundness is essentially subjective, so the suggested requirements given here may have been influenced by the personal experience of the authors, and their applicability should also be reviewed for each particular case.

[1] "Systematic comparison of SHSs existing standards". IES Internal Report. 1997

Source: Universal technical standard for solar home systems, Version 2, Thermie B SUP 995-96, EC-DGXVII, 1998, updated in 2001.

This Wiki-Text gives an overview of the standards proposed by the "Instituto de Energía Solar" for the different parts of a typical SHS.