Solar cells (photovoltaic cells) are semiconductor materials that convert sunlight directly into electrical energy. The area of solar cells, whose surfaces are shaped as squares, rectangles or circles, is usually around 60 cm² to 160 cm² and their thickness is between 0.2-0.4 mm.

Cell defects are seen as hot spots in thermographic examination, which are shaped according to the production characteristics of the panel. PV panels are usually produced by connecting different numbers of cells (such as 36, 60). For this reason, if the production of even one cell of the panel decreases due to various reasons (shadow, pollution, etc.), it affects the production of all cells in the panel.

It is the junction point of the cables connecting the photovoltaic panels in series with each other and the cables going outside. In this box, the ribbons/conductors coming from the cells are connected to the panel cables to the terminals. The junction box is a kind of terminal box. There are also fuses and bypass diodes inside this box.

Junction boxes, which are manufactured resistant to outdoor conditions, are adhered to the back surface of the panel with chemicals and have an openable cover on top.

When the diodes burn out, this cover can be opened for repair and measurement. At the same time, the heat of the junction box can be seen from the panel surface in case of malfunction. Detecting junction box faults in the early stages is important in preventing the risk of fire.

Module anomalies caused by cracks in the module. Cells reaching high temperatures due to these cracks lead to solder melting, thermal fatigue, rupture of contact wires and rapid aging of intact cells. This failure, which occurs in cases of installation error, manufacturing error or exposure of the panel to an external mechanical effect, can be detected by thermographic inspection.

Repeated relative movement of cracked cell parts can lead to complete separation and thus inactive cell parts. For this special case a clear assessment of the power loss is possible. For a 60-cell 230 Watt PV module, the loss of cell parts is acceptable as long as the lost part is less than 8% of the cell area.

In order to obtain the desired voltage from solar cells, these cells are connected in series or in parallel and these cells do not always receive the same intensity of sunlight. In case of any shading, the output power of the panel decreases. Bypass diodes are used to prevent this drop. Bypass diodes are activated in a shaded condition. Current flows through the diodes, preventing a decrease in panel power.

The bypass diode, which should ideally be connected to each cell, is not connected in this way because it increases the cost. One of the common faults in plants is active bypass diodes, such faults show a characteristic thermal distribution in a certain strip of the panel depending on the way they are connected.

Defects caused by poor adhesion between the glass, encapsulant, active layers and back layers.

Typically, delamination occurs due to adhesion contamination (e.g. improper cleaning of the glass) or environmental factors, followed by moisture ingress and corrosion. The cell heats up too much, damaging both the coating material (EVA) and the support film (TPT).

Delamination defects are more common in modules produced by thin-film technique and have a low risk of causing a fire by itself. However, if this fault is combined with the failure of a bypass diode, it causes a significant safety hazard in addition to a significant or, more likely, complete loss of power to the module. Gaps can create a large and continuous arc at temperatures that can melt glass, subject to the overall system voltage.

In terms of working principles; Strings (arrays) consist of photovoltaic panels connected to each other and the arrays formed in this way are connected to the inverter. Inverters are connected to an alternating current collector panel and from this panel to the grid via a transformer.

In centralized inverters, the connections of photovoltaic panel arrays are collected in a direct current collector box and connected to the central inverter from this box. The central inverter is connected to the grid via a transformer. Considering this working principle, String faults reduce the output power of the whole plant and are analyzed in the thermographic inspection according to the thermal characteristics of the adjacent panels matching the inventor layout.

In the case of partial shading in solar energy systems, the power varies significantly depending on the voltage, reducing the output power of the panel.

In photovoltaic systems, when shadow falls on some of the cells, these cells act like diodes, blocking the current generated by other cells. These cells, acting like diodes, are also subject to the voltage of the other cells, causing localized overheating, causing the connection to be punctured and damaging the module. These faults are caused by sunlight blocked by vegetation surrounding the photovoltaic system, man-made structures, or adjacent rows due to improper installation.

MapperX detects and reports shading errors. You can follow the guidelines in the report to increase efficiency in solar power plants.