温度変化による太陽電池モジュール不具合の顕在化と潜在化

抄録

In this study we present the results of an experiment regarding the process of exposure and concealment of PV, photovoltaic, module interconnect failure, induced by temperature change. To carry out the experiment we built a PV string of modules with interconnect failures and observed its I-V characteristics for six months. Each PV module had two clusters, and each cluster had its cell strings output electrodes connected to a bypass circuit with diodes. The experiment showed that when the module temperature increased, the open circuit voltage and maximum power voltage of the PV string decreased below the amount indicated by the temperature coefficient. However, once the modules temperature decreased both voltage values returned to their original values. Regarding the dependence of maximum power voltage on temperature, we observed that it varies linearly in discrete intervals of voltage, and that such intervals were in agreement with the output voltage variation of the PV clusters. Moreover, the number of discrete intervals correctly indicated that eight PV clusters had interconnect failures, and at 60°C between seven to eight interconnect failures could be identified. However, when the temperature of the modules dropped to 25°C at most 2 interconnect failures were detected, indicating the occurrence of a concealment process. Finally, the study also shows the usefulness of the bleeder resistance method, and of the constant current method to detect interconnect failure in outdoor conditions.