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A team of Spanish researchers has developed a set of techniques to repair busbar interruptions in photovoltaic panels without resorting to expensive electroluminescence imaging. Scientists warn that the proposed method should not be used with modules that have not passed some basic safety tests.
A group of researchers led by the Center for Energy, Environmental and Technological Research (CIEMAT) in Spain has developed a set of techniques to repair busbar interruptions in photovoltaic panels.
“Interruptions between cells represent 10% of module failures,” Félix García Rosillo, lead author of the research, explains to pv magazine . “Repairing outages can be done with conventional hand tools and can help recover most of a modules rated power.”
The scientists presented two different repair methods. The first requires complete removal of the module backsheet, replacement of damaged bus bars, and placement of a new backsheet. The second requires removal of the backsheet in the damaged area, welding of the bus bar and sealing with silicone resin.
Both techniques do not require the acquisition of expensive electroluminescence (EL) images of panels before and after repair. “It is important to clarify that it is not possible to obtain EL images of a module affected by twin ribbon bus interruptions,” the scientists noted. “If the current tries to flow between the contacts of the solar panel, connected to a power supply and two of the cells are affected by a complete interruption of the ribbon bus bar, the current will not flow and, consequently, it will not be possible to obtain the image “THE”.
The academics explained that if the diodes are removed from the junction box and the electrical connections between the various terminals of the junction box are checked at the time of the EL measurement, unaffected arrays of cells can be imaged. They also noted that in the pre-repair EL images, only the active series of cells is visible to the camera. “When the module is repaired, the EL image reveals all the cells and it is possible to know their real state,” they added.
The repair process requires the use of tone testers or wire locators to accurately identify the interconnection of the interrupted twin cells. “A tone checker capable of performing this task can cost just over two dozen euros,” the team explains. “A similar result can be achieved by using a current detector to locate interruptions in single-bus bus cells, also at low cost and with a fast procedure.”
The last step of the repair can be performed with conventional craft tools, such as mini drills, belt sanders, or conventional welders. “Soldering paste and tape bus bar add-ons turn out to be a good option to repair tape bus bar interruptions,” the researchers emphasize.
After repair, the proposed method requires performing an IV curve measurement to determine how much power output has been recovered.
The research group carried out a series of tests with three 215 W modules produced in 2006 by the German manufacturer Qcells and found that, in some cases, it is possible to multiply the power output of the damaged modules by four.
“Safety should be an important objective when repairing a photovoltaic module, and any repaired module that does not pass some basic safety tests should be removed from service and recycled,” they noted, referring to the initial selection that must be made to avoid risks to installers.
The new technique was presented in the article “ Repairing ribbon bus bar interruptions in photovoltaic modules using non-intrusive interruption location ,” published in Renewable Energy . “This methodology can be applied in modestly equipped factories or laboratories, reducing the economic cost of repairing photovoltaic modules,” the academics conclude. |
