IR-IMAGES INVESTIGATION OF THE THERMAL BEHAVIOR OF SHADED PV CELLS DURING OPERATION

摘要

Partial shading on photovoltaic modules or systems can lead to early aging and failure of the shadowed cells. As a result of this critical situation more than one power peak appear on the P-V characteristic curve. The purpose of this work is to evaluate the heat dissipation and the temperature distribution in the shaded solar cells for each local or global power peak. To this aim, three PV systems are used. Each of them is composed by one Si-monocrystalline PV module (JT-185W) equipped with three bypass diodes, 2 volts solar battery elements are used as loads. For each module two shaded solar cells are considered, each cell is from a given string protected by a bypass-diode. IR images show the limits of the temperature distribution in each shaded cell for each peak (local or global) and the influence of the shadow pattern on the P-V characteristic curve. The risk of shading on the PV module was quantified. It was found that the nearest power peak to Voc on the P-V characteristic curve is the safest one for the module operation.