IEEE Std 1562-2021 pdf download – IEEE Recommended Practice for Sizing of Stand-Alone Photovoltaic (PV) Systems.
4. Outline of sizing methodology 4.1 General Part of the process of sizing of a stand-alone photovoltaic (PV) system is to determine the required number of PV modules and the capacity of the battery. Other sizing aspects include wire, charge controllers, inverters, etc., which are beyond the scope of this document. The sizing is based on a combination of worst-case solar radiation, load consumption, and system losses. (Ambient temperature is also used when sizing maximum power point tracker (MPPT) charge controllers.) This is different than sizing hybrid or grid-connected systems, where the PV array may be sized to help maximize solar energy production on an annual basis. The PV array is sized to replace the ampere-hours (Ah) in the battery consumed by the load and to provide sufficient energy to overcome system losses and inefficiencies. Any additional over-sizing of the PV array is used to recharge the battery faster after periods of low solar radiation. Two different sizing methodologies are used in this recommended practice, both based on the average daily load in Ah. The methodology used depends on the type of charge controller in the system. (Refer to Annex C for more information on charge controller types.) Module temperature deratings are considered for determining the required number of series modules and Wh production from PV arrays using MPPT charge controllers, as the temperature has a great effect on the operating voltage (and therefore power output) of a PV module. Shading of the PV array is not addressed, and it is assumed that the PV array will not be shaded throughout the day. If the PV array is shaded, a computer model may be needed to determine the effect of shading on the output of the PV array.
The performance of PV systems is directly dependent on the accuracy of the solar radiation data and the load consumption data used. Inaccuracies in either of these pieces of information will cause the system to be over- or under-designed. The criticality of the application or load availability is also important. If the load is not critical and a loss of load can be tolerated, then the system can be designed more cost effectively than a critical system that requires extremely high system availability.