In EF Solare Italia we pursuit a continues path of research and technological evolution to make solar power generation more and more efficient and sustainable.


In EF Solare Italia we have tested the use of electroluminescence to monitor solar panels in our Fiumesanto photovoltaic plant, near Sassari in Sardinia, to identify those compromised by the PID (Potential Induced Degradation) effect. Thanks to this solution the duration of the inspection has dramatically shortened and we have been able to intervene quickly, identifying the defective panels and scheduling their substitution to recover the optimal solar power generation level.


PID effect is caused by a degenerative phenomenon that regards crystalline silicon photovoltaic technology and is caused by a power loss at high tension, that causes a sharp decrease of the plant Perfomance Ratio. In detail, it is a progressive dissipation of the charge carriers in form of dispersion currents that run from the module to the ground. Humidity and heath tend to accelerate the process.

The industry has become aware of the issue from 2013 onward, when the panels issued on the market between 2008 and 2011, a timespan of massive new installations, begun to suffer from it. Only recently, to root out the issue, a PID-free certification has been introduced.


Electroluminescence analysis allows to verify emissions from photovoltaic cells powered by alternate current. The luminous emission, invisible to the naked eye, shows possible flaws and malfunctioning, including the PID effect, that is revealed by feeble or absent emissions, especially around cells on the edge. In the last few years it has become possible to use electroluminescence directly on site, with several advantages compared to lab analysis, including cost reduction: you do not risk to damage the panels during the disassembling and transport phases and it is possible to test them in their exact position inside the string.

Once the PID-ridden panels are identified, they are grouped in three severity categories. Those most compromised – more than 60% of the cells turned off – have to be replaced, the others can be treated with Anti-PID kits that, even if they do not solve the problem, can stop it and hold it or – with Anti-PID active kits – reverse the process until they almost eliminate it. These Anti-PID kits are devices that operates outside the production timeslots and, by generating an alternate current flux, allows the panel to recharge at night. After a month of constant use of the kit, the module is back to 80-85% of its capacity.

Electroluminescence analysis must be carried out in complete darkness and thus is usually performed at night. At Fiumesanto, the analysis has been carried on over 25,000 panels and has allowed us to identify over 6,000 photovoltaic modules afflicted by PID and another 7,000 – 10,000 at strong risk in the medium range: regarding the first we are moving forward with their replacement with compatible panels from another producers. For the panels at risk we are acquiring Anti-PID kits to install to prevent the degenerative process so to not have to replace them in the future.

In EF Solare Italia we pursuit a continues path of research and technological evolution, to make solar power generation more and more efficient and sustainable thanks to innovation such as analysis through electroluminescence or thermography, which we aim to turn into shared standards across the whole industry.

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