System modelling forms a key part of the photovoltaic (PV) system design. It can provide answers to a number of important issues such as the overall array size, orientation and the electrical configuration; it can also determine the size of various subsystems such as the battery and/or the inverter (see the standard for a detailed discussion of the relevant terminology used to describe PV systems). The design criteria will vary depending on the nature of the application. In stand-alone systems, the consideration of energy production to meet the load is paramount; the reliability of supply and economic considerations may also be important. A critical aspect of stand-alone system design is sizing which is discussed in Section 2. The applications of grid-connected systems vary from small building integrated systems (BIPV) to PV power stations. Modelling tools are available to provide solar radiation data, assess possible shading effects (which may be particularly important at urban sites), and produce the resulting electrical layout of the array. Further considerations will include the restrictions imposed by the connection to the local utility, discussed in Chapter IIc-1. Economic aspects may include an investigation of financial support mechanisms and the economic impact of local electricity generation, including possible revenue for electricity exported to the utility through feed-in-tariff or net metering.

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