Optimization of Auxiliary Power Supply (APS) Systems with Photovoltaic Modules

Auxiliary power supply (APS) systems are increasingly used for low power rating home appliances (e.g. televisions, water dispensers, etc.) and lighting (e.g. CFL lamps) in countries where long power rationing schemes are applied. In general, these systems charge a 240AH (Ampers-Hours) bank of batteries as long as the grid is on and then convert the stored energy into AC current to supply a load of 400W during the rationing time which sometimes last for several hours (four to six hours). Thus, such systems would be able to afford all these hours if and only if the battery bank of the APS was fully charged. Unfortunately, the practice shows that this target (full charge of the battery bank) cannot be achieved mainly due to the short on period of the grid – while in lucky times (when there are no sporadic interruptions) the on period of the grid does not exceed six consecutive hours, the average time needed to fully charge the battery bank at 20 amps charging current is twelve hours. This paper shows how a small number of solar photovoltaic (PV) modules can be used as an additional charging power source to overcome this problem. Besides the major reduction in the size of the PV modules, an average saving of 61.5% in the energy drawn from the utility is achieved. Keywords— Hybrid supply systems, solar photovoltaic modules, off grid. ————————————————————