Consideration of insolation characteristics in sizing stand-alone PV stations

Stand-alone PV schemes have found a fairly wide application in remote isolated regions to meet small but essential electric load. The capacities of such stations are commonly specified in terms of the peak power available during maximum solar insolation. The actual insolation available at a site is, however, affected by the vagaries of the weather in addition to the seasonal and diurnal variation. The support for these systems to cover for the periods of low insolation levels is provided by the battery system. The variation of insolation can be quite drastic and the peak rating may not be a proper measure of the station capacity. This paper analyzes the statistical nature of the available insolation using historical data collected at an experimental PV station. It attempts to determine the appropriate statistical distribution for the insolation level. This representation is then used to simulate the operation of stand alone PV stations probabilistically using different station configurations to evaluate their performance. An interactive software package has been developed using MATLAB to carry out the insolation data analysis and to simulate the operation of such schemes. The details regarding: (i) the modeling of various components; (ii) the features of the software package; and (iii) typical simulation results and their applications, are presented