PV systems can operate trouble free for many years if they are well designed, well
planned, and properly installed. Quality components also add to the reliability
and stability of the system.
Good quality modules are usually the most reliable components of the PV
system. Do not fool yourself or your customer into thinking that PV panels or
inverters are commodities that are all basically the same in output, efficiency,
spectral-response consistency, and quality. They are not. The difference in
product quality alone is dramatic.
Some crystalline modules work well for more than 25 years and hardly age.
UV rays and temperature may cause slight degradation and some bleaching over
time. Weather aging also causes wear and tear on a module leading to corrosion
and degradation. Module degradation is the drop in electrical-energy output of a
solar module over its lifetime. Some panels hold up better than others. Degrada-
tion usually occurs due to environmental, fabrication quality, and material factors.
Plastic panels have a great deal of variability in all of the factors mentioned
above. All plastics and related polymers age over time and will age and deteriorate
even more rapidly in high-temperature and high-altitude locations. The plastic
cell encapsulation in a module ages and causes reliability issues. Plastic can
become detached from the cell. This is called delamination. Delamination occurs
more often in modules exposed to high temperature, UV, and humidity.
Crystalline panels also delaminate and degrade. This is becoming more
common with the proliferation of new manufacturers and factories. It takes a
substantial amount of time, skill, and ability to bring a manufacturing plant to an
adequate level of quality control in production. It is not an overnight process. PV
manufacturers are in the process of developing and instituting new manufac-
turing standards that will increase the quality and production of PV panels.
The design and installation portion of the industry has a lot to learn about
standards. This process is just beginning.
Thin-film modules experience degradation at a higher rate in general. They
often experience a degradation of 10 percent in the first 1,000 hours of exposure
to the sun. This degradation is partially a result of the technology and chemistry
related to light. There are still unknown factors in the way they degrade.
After the initial loss, the power output may not remain consistent. You must
consider this power loss during the design and output estimation phase. It is gen-
erally assumed that a thin-film cell will degrade by 0.25 to 0.5 percent each year. It
is important to remember that that thin film does not have the same performance
history of mono- and polycrystalline systems.
This industry must step up the quality of systems and components, and back
them up, instead of just pushing the issues of low cost. Low cost will come back to
hurt many customers and integrators.
210 REVIEW GUIDE FOR THE NABCEP ENTRY-LEVEL EXAM