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In this section, we will design a simple stand-alone system, as depicted in Figure 20.1. The
design presented here is based on very simple assumptions and does not take any weatherdependent performance changes into account. Nonetheless, we will see the major steps
that are necessary for designing a system. Such a simple design can be performed in a six
step plan:
Determine the total load current
1
and operational time.
Add system losses.
Determine the solar irradiation in daily equivalent sun hours (ESH).
Determine the total solar array current requirements.
Determine the optimum module arrangement for solar array.
Determine the battery size for recommended reserve time.
Choose a suitable charge controller.
Figure 20.1: Illustrating a simple off-grid PV system with AC and DC loads (see also Figure 17.2).
1. Determine the total load current and operational time
Before we can determine the current requirements of loads of our PV system, we have to
decide on the nominal operational voltage of the PV system. Usual nominal voltages are