Sizing Batteries for Photovoltaic Systems

This paper describes a computerprogram for sizing photovoltaic stand-alone systems (PV-systems) with batteries. The computer program is based on an insolation model described by M Collares-Pereira and Ari Rabl (1) and a newly developed battery algorithm. The algorithm is based on - capacity derating as a function of electrolyte temperature - charging efficiency as a function of electrolyte temperature and state of charge - charging voltage as a function of electrolyte temperature and state of charge The program is used to calculate the required number of PV-modules and the size of the battery. The program was originally designed for nickel-cadmium batteries, but can also be used for sizing systems with lead acid batteries, if the required battery data are available.