Non-contact measurements method of of solar cells shunt resistence in panel

Abstract

For the periodic control of photovoltaic solar panels during their operation, an important task is to obtain data on the internal condition of the solar cells’ plates, which may indicate the beginning of the degradation process due to the appearance and development of hidden local defects. An objective criterion for the condition of a solar panel is the results of measuring its electrical parameters. One of these important parameters is the shunt resistance. When the value of the shunt resistance is reduced in the solar cells’ plates, an additional Joule heat begins to be released. The result of this process can be local overheating of the panel, as well as a decrease of its efficiency. A significant drop in the efficiency of a solar panel is a sign of its degradation. Degraded panels are decommissioned. According to the authors, the forecast of the beginning and further development of the degradation process is possible and could be performed based on data on the value of the shunt resistance of individual solar cells in the panel. The authors proposed a non-contact method of measuring the shunt resistance of solar cells that are already mounted in the panel and do not have galvanic contacts for control. As non-contact sensors, flat rectangular antennas made of fiberglass, which is covered with a one-sided layer of copper, were used. The sensors are placed directly above the solar cells. The signal from the generator successively passes through the line of shunt resistances of all solar cells, and its amplitude gradually decreases. Antenna sensors allow you to capture a signal without distortion and display it on the screen of a digital oscilloscope. When a uniform decline of the signal from one antenna to the next is present, we have the same value of the shunt resistance and the identity of the solar cells. According to the authors, this method should be used to check solar panels that are planned to be installed in hard-to-reach or difficult-to-mount and dismantle places: on the facades of high-rise buildings, on roofs, canopies, etc. This method will reduce the risks of allocation of additional costs for replacing those panels that are subject to degradation during operation. The aim of this work is the justification of the non-contact method of measuring shunt resistance and its experimental verification in laboratory conditions on the basis of a solar panel made of polycrystalline silicon with a nominal power of 270 W.

Keywords

• predictive maintenance
• shunt resistance
• solar panel