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Figure 6.1. Possible uses of photovoltaics on and off the central grid.
In the US in 1991, a PV system could be cost-effective if the grid extension was more
than 5 miles and the load was less than 1500 kWh/month, typical of two houses
(Rannels, 1991). Smaller 2 kW systems could be cost effective at grid extensions of
only one third of a mile (Ibid.).
6.2 STAND-ALONE PV SYSTEM DESIGN
The design of a stand-alone PV-based power system is determined by the location,
climate, site characteristics and equipment to be used. The selection and
interconnection of system components will be discussed in this chapter and design
procedures in the next. Unless stated otherwise, the comments on storage refer to
lead-acid batteries. Fig. 6.2 shows a schematic of a typical PV-based stand-alone
power system.
Many countries and regions have produced standards and/or guidelines for PV
systems over the last decade, and the applicable ones should always be understood
and followed by designers and installers. Sometimes, compliance is a condition for
subsidies or other forms of financial support. In Australia, the primary standards of
interest are the AS4509 series of three standards (Standards Australia, 1999–2000a,
1999–2000b, 2002). Other standards apply to system components and particular
aspects, some of which are mentioned below and/or listed in Appendix E.
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