Non-Contact Measurement of Electric Potential of PV Modules

PV module characterization by non-contact electrostatic potential measurement method is investigated. The method can be carried out by a portable equipment under various outdoor operating conditions as well as in laboratories. The electric potential of the cells in various crystalline silicon and thin film PV modules can be determined in a noncontact configuration such as through their cover glass and backsheet. Basic repeatability of the electrostatic voltage measurement was confirmed to be within about +/- 0.5 V for indoor measurements, which is better than the output voltage of a component cell. The repeatability was typically within the voltage corresponding to 2 to 3 times the component cells even under changeable outdoor conditions. The present study demonstrates that the method is applicable to PV module characterization, such as identifying a hotspot cell in a PV module and determining degraded modules in a PV array, through monitoring the distribution of their electric potential under outdoor conditions without interrupting the grid-connected operation of the system.