9 Solar Module Technology
241
2. Accelerated degradation: generally due to unexpected phenomena (e.g.
potential-induced degradation (PID), snail-trails, etc.). These phenomena can
be triggered by a poor selection of the materials constituting the module, by a
poor module or system design, by damages occurred during the installation or
transport phase, or by specific climatic conditions (heavy snow loads, high UV
contents, marine environment, etc.).
3. Sudden degradation following a catastrophic event/failure: as for example a
fire, a lighting strike, or an earthquake.
Typical long-term annual degradation rates have been reported (from statistical
analyses of data given in the literature) to be in the order of −0.5 to −1%/y for
conventional crystalline silicon modules and somewhat higher for thin film modules
[7, 19, 21, 23–26]. Higher degradation rates occur in modules approaching their end
of life [21, 26]. The most relevant aging and failure mechanisms for c-Si modules
that may occur in the early period (so-called “infant” failures), during the middle of
operating life, and at the wear out (end of life) phase will be described in Chap. 10,
next up. These include:
• Effect of the environment on the surface of the module (e.g. pollution, soiling,
etc.);
• Discoloration or haze of the encapsulant or glass;
• Delamination of encapsulant leading to water ingress;
• Cell interconnect corrosion, loss of adhesion, increase in series resistance;
• Wiring degradation;
• Delamination or water ingress in the junction box;
• By-pass diode failure;
• Glass breakage;
• Loose frames;
• Potential-induced degradation (PID);
• Cracked cells;
• Backsheet foil defects: cracking, brittling, burn-marks,
7 etc.
Figure 9.14 shows an example of both “minor” and “major” failures for two
modules of the Tiso-10-kW solar plant connected to the grid in 1982 and operating
for 35 years in a temperate climate [7, 21]. “Soft” or “minor” failures have, according
to their definition, a moderate impact on performance. “Hard” or “major” failures
are failures, which substantially reduce module performance; they may in parallel
affect the operational safety of the module.
7 A typical example of burn-mark is a localized dark colouring of the backsheet. This is generally
due to localized overheating or arcing.
241
2. Accelerated degradation: generally due to unexpected phenomena (e.g.
potential-induced degradation (PID), snail-trails, etc.). These phenomena can
be triggered by a poor selection of the materials constituting the module, by a
poor module or system design, by damages occurred during the installation or
transport phase, or by specific climatic conditions (heavy snow loads, high UV
contents, marine environment, etc.).
3. Sudden degradation following a catastrophic event/failure: as for example a
fire, a lighting strike, or an earthquake.
Typical long-term annual degradation rates have been reported (from statistical
analyses of data given in the literature) to be in the order of −0.5 to −1%/y for
conventional crystalline silicon modules and somewhat higher for thin film modules
[7, 19, 21, 23–26]. Higher degradation rates occur in modules approaching their end
of life [21, 26]. The most relevant aging and failure mechanisms for c-Si modules
that may occur in the early period (so-called “infant” failures), during the middle of
operating life, and at the wear out (end of life) phase will be described in Chap. 10,
next up. These include:
• Effect of the environment on the surface of the module (e.g. pollution, soiling,
etc.);
• Discoloration or haze of the encapsulant or glass;
• Delamination of encapsulant leading to water ingress;
• Cell interconnect corrosion, loss of adhesion, increase in series resistance;
• Wiring degradation;
• Delamination or water ingress in the junction box;
• By-pass diode failure;
• Glass breakage;
• Loose frames;
• Potential-induced degradation (PID);
• Cracked cells;
• Backsheet foil defects: cracking, brittling, burn-marks,
7 etc.
Figure 9.14 shows an example of both “minor” and “major” failures for two
modules of the Tiso-10-kW solar plant connected to the grid in 1982 and operating
for 35 years in a temperate climate [7, 21]. “Soft” or “minor” failures have, according
to their definition, a moderate impact on performance. “Hard” or “major” failures
are failures, which substantially reduce module performance; they may in parallel
affect the operational safety of the module.
7 A typical example of burn-mark is a localized dark colouring of the backsheet. This is generally
due to localized overheating or arcing.