Systems considered in this recommended practice consist of PV as the only power source and a battery for energy storage. These systems also commonly employ controls to protect the battery from being over- or under-charged and may employ a power conversion subsystem (inverter or converter).
This recommended practice is applicable to all stand-alone PV systems where PV is the only charging source. This recommended practice does not include PV hybrid systems nor grid-connected systems. This recommended practice covers lead-acid batteries only; nickel-cadmium and other battery types are not included.
This standard applies to roof-mounted, ground-mounted, pole-mounted, or integrated-mounted modules used in a PV system with a voltage of 1000 volts or less. The National Electrical Code applies from an installation standpoint.
Requirements for Photovoltaic (PV) Generators (currently in development by IEC TC 82) – will set out general installation and safety requirements for the PV equipment. The Scope of Section 712 in BS 7671:2008 includes PV power supply systems including systems with a.c. modules but, currently, excludes any form of battery storage.
There are many systems across the world that feature battery storage but no single standard has as yet been developed to reflect this. Section 712 of BS 7671:2008 is Solar photovoltaic (PV) power supply systems; the section is likely to remain largely unchanged in the first amendment of the standard, due for publication in June 2011.
As shown in Fig 1, the PV system incorporates a number of PV modules which convert the energy of solar radiation emitted by the sun into electrical energy by means of the photovoltaic effect. The modules are connected into series ‘strings’ to provide the required output voltage and arranged into one or more arrays.