The Operation of Loads Powered by Separate Sources or by a Common Source of Solar Cells

A procedure is introduced for analyzing the interaction between different loads connected to a common solar cell (SC) source, and the performances of these loads when powered by separate and common sources are compared. It is shown that for identical loads (the same type and size), either optimal or nonoptimal, powered by identical SC arrays, and for loads of the same type but different sizes that are powered by proportional sizes of SC arrays, the operation of the loads is the same when powered either by separate sources or by a common SC source. The arrays in the separate source systems are of the same sizes, and in the common source system the arrays are of double size. The loads in both setups are of the same type. Two types of loads are considered in this study: two different ohmic loads; two different water electrolyzer loads. A comparison of the operation of the above two load types is performed for systems that incorporate a maximum-power point-tracker (MPPT), for both the separate and common SC sources. The criterion for comparing the performances is the energy utilization efficiency. It is shown that the performance of one load affects the performance of another load in a common source system. In systems not including MPPTs, the total performance of the loads in a common source system is improved as compared to the total performance of the loads when they are powered separately by individual sources. In systems including MPPTs, the total performance of the loads is the same when powered either by a common source or by single sources. MPPTs improve the performance of loads, the amount of improvement depending on the mismatch of the loads to the solar cells. >