Optimizing photovoltaic array size in a hybrid power system

This paper describes a simple programming model to minimize the life cycle cost of a hybrid power system consisting of a photovoltaic array, engine generator and battery. The power output of the array is calculated and used to optimize an objective function which calculates the net present value of the system over its life. While the life cycle cost of the PV array is its capital cost which increases with the size of the PV array, the life cycle cost of the generator is a function of operation time, which decreases as a function of the PV array size. In addition, the life cycle cost of the battery can also be calculated as a function of PV array size since this determines the frequency and depth of battery cycling, which is the main contributor to battery aging. Therefore, choosing an optimum power system design to meet a specific load is reduced to determining the optimum PV array size. The designs generated by the model are compared with a more accurate hourly irradiation performance model.