Research On Why Solar Panels Yield Less Over Time?

• TNO Energy Transition and Solliance Solar Research are conducting joint research on thin film and crystalline silicon solar panels to understand why their output fails over time
• Using the technique of post mortem, solar panels are studied deep inside layer by layer to understand the reason for their failure
• They believe this can help predict what will be the yield of a solar panel over time

A group of researchers from TNO Energy Transition and Solliance Solar Research from the Netherlands are conducting research on defective solar panels to understand why these yield less over time. As per 100 samples studied so far by the team using a specific technique, the joint research figured out a number of factors leading to less output from the panels that are retrieved from the field.

They term their technique as 'post mortem' that TNO carries out at Solliance by dismantling both thin-film and crystalline silicon solar panels that are defective and examines these. Defect locations are pinpointed before disassembly and if the underlying issue is within the cell, it is cut off from the panel. Protecting layers are peeled off to study faulty layers.

To ensure no damage to the cell, the researchers had to develop and tune a process to peel off the top layers. Once the cell is stripped, it is connected and analyzed.  The team claims similar measurement and techniques can be used to analyze.

"With the technology we have developed, we can finally look inside the modules. This means that many research methods that we have been using for years in the laboratory to test new solar cells can now be applied to these failed modules," said Researcher at TNO/Solliance, Mirjam Theelen. "All these square kilometres of installed solar panels become a huge testing ground where we can perform autopsy by examining pieces of broken modules as single cells. In this way, we can do nanometre-scale analysis on degradation effects found on kilometre-scale PV installations."

The team says the panels being studied show these failed due to factors ranging from an extreme consequence of partial shading of the panels, and worm-like defects. At the same time, some reasons were due to PID-induced defects that spread.

The researchers continue to study the defects further and claim that the full potential of the technique has not yet been reached and will only develop as new types of defects become available to study and new reliability questions are raised.

"We conduct large-scale research on panels in the field. With this research, we learn why some panels have started to generate less electricity. In this way we can better predict what the yield will be during the long life of a solar panel," said Researcher Thomas Weber from Photovoltaic Institute Berlin (PI Berlin) and the Twente University both of which are collaborating in this research.