Hi M.A.M. Manaz,

Just this on the lifetime of photovoltaic solar panels. Solar modules are exposed to many environmental influences that cause some its materials to fatigue over the years. Researchers have developed a procedure to calculate the effects of these environmental factors for the long term. This allows lifespan predictions.

People who invest in their own solar panels for the roof would like as a rule to profit from them over the long term -- but how long will this technology actually last? While most manufacturers guarantee a lifetime of up to 25 years to their customers, the manufacturers themselves cannot make reliable predictions about the expected operating life. The modules must fulfill certain standards, of course, to be approved for operation. This involves exposing them in various trials to high temperatures and high mechanical loading. "However, this type of results only predict something about the robustness of a brand-new PV panel with respect to extreme, short-term loading. In contrast, age related effects only appear over the course of time. Material fatigue is a prime factor here and pertinent for the actual operating life.

Germany's Federal Environment Ministry funded a project on this topic and is working on a new procedure to predict the operating life of PV modules. Using a dual approach, actual measurements are combined with numerical simulations. To this end, initially scientists investigated how mechanical loading affects PV panel units in field tests. Snow load, temperature fluctuations, and wind gusts create mechanical stress, strain and elongation in the modules. This leads to material fatigue on the long term. Both the plastic embedding material and the cell connectors in particular -- thin strips of copper that connect the solar cells to one another -- are susceptible. It is like continually bending a paper clip back and forth. At some point, it breaks.

Even light wind gusts causes module oscillations. To be able to grasp the effect of these influences on the materials, researchers equipped a complete solar module with sensors measuring changes in resistance to probe for strains and elongations in the construction components. In turn, this allows the mechanical stresses in the material to be calculated. From data evaluation it was shown that even light wind gusts suffices to cause oscillations in the PV module units. The higher ambient temperature, the more pronounced these oscillations become. Moreover, the resonant frequency increases over time as the plastic material gets stiffer and more brittle, due to UV radiation. "The pivotal question is how these influences affect the operating life of the components in the long term. It is then that simulations come into play.

For this purpose, a detailed 3D simulation of a PV module has been worked out. Based on the measurements from the field tests, numerical calculations are used to derive long term effects of the environmental influences on the module components and what kind of mechanical stresses develop. Using the simulation, engineers learned for example that the brittleness caused by UV radiation plays a much more important role in material fatigue than assumed thus far. To be able to predict the operating life of a module, researchers combine the measurements from the field tests with known specific tensile strengths of corresponding materials. These numbers predict the load at which the material is expected to break or separate.

The procedure can be implemented immediately. However, to produce optimal and reliable prognoses, highly detailed specific material data and information about the geometry of the module is to be measured. The procedure has to be tuned for each specific customer,. Using the calculations, the researchers are able not only to make predictions about expected operating life but they can also depict potential improvements with regard to geometry and material slection as well as predict the effects of various materials on the mechanical stresses in the module.

That's where we are right now in Germany Manaz.

Cheers,

Frank

Dear Prof. Frank Veroustraete,

Thank you very much for your detailed explanation for my question. And this is the most comprehensive explanation I have ever got on the topic. Thank you again.

So far when I searched the internet for the answer for this question, I did not really get any closer to what you have explained. So it would be a great pleasure if you could provide or recommend some reference materials on this topic, which would help me understand these phenomenons in more detail.

Thank you,

Manaz

Are you referring to Silicon solar panels? They are many fundamental mechanisms as well for different technologies. Thin film vs bulk silicon. And thin film Si vs CIGS or CdTe.

For crystalline Silicon PV cells, the encapsulant seems to be the most import defining factor. The actual crystalline PV cells never wear out or degrade over our lifetimes; but the yellowing of the encapsulant blocks some of the light coming in or the encapsulant allows water to get to the cell surface to corrode the contacts. On my own off-grid home, I have PV cells that are well over 30 years old and they haven't changed siginficantely since I installed them used 26 years ago. some of the PV modules were well cooked on the Carrizo Planes before I got them. The proper way to recycle PV modules is to sell them to aging hippies.

Dear Christopher Buurma,

My question was regarding any general solar panels. But, according to the answers that I got from those experienced in the field of PV, it seems that life time of different panels depend on different factors. Could you please kindly share your view on the specific factors defining the life of different type of PV panel.

I should thank Richard Komp for sharing his experience. It is wonderful to hear that those PV panels are working fine for 30 years in the off-grid home.

Dear Abderafi Charki,

Your paper on regarding degradation of solar panels do provide an in depth analysis on various types of degradation that a solar panel could under go. Which make me think that you might be the right person to clarify my doubt.

Let me make the question shorter. Would the fact that the PV panel is connected to an electric load has any effect on degradation of the solar panel?

Its fill factor, oepn circuit voltage and short circuit current are the defining factors