Partial shadowing protection without diodes

Abstract

Abstract Partial shadowing on a photovoltaic module causes serious power loss in the photovoltaic module output. The percentage power loss is generally much larger than the percentage of the shadowed area of the module. A model has been developed — taking into account both the series and shunt resistances of the solar cell — to obtain a relationship between the percentage of power loss and percentage of shadowed area. The results obtained showed that the shunt resistance of the solar cells plays the major role in determining the relation between power loss and shadowed area of the module. An approximate formula for the power loss as a function of both shadowed area and shunt resistance is given. It is also proved that the power loss is determined by the total shadowed area of the module, regardless of the number of shadowed cells, i.e. if two cells are 50% shadowed or a single cell is totally shadowed, the same power loss results. In this work an alternative solution for the partial shadowing problem is tried. The concept is based on connecting the solar cells in the same module in a parallel series configuration, instead of the conventional series connection. The power loss of such modules is proved to be less. It is also shown that the number of series-connected cells does not influence the power loss due to partial shadowing as long as the percentage of shadowed area is kept constant.