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 for? 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, the results only predict something about the robustness of a brand-new sample with respect to extreme, short-term loading. In contrast, agerelated effects that only appear over the course of time, such as material fatigue, are pertinent for the actual operating life," explains Alexander Fromm from the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg.
The scientist is part of a project called Reliability of Photovoltaic Modules II, funded by Germany's Federal Environment Ministry (BMU), and is working on a new procedure for predicting the operating life of solar cell modules. "Using a dual approach, we combine actual measurements with a numeric simulation," according to Fromm. To this end, Fromm is initially investigating how mechanical loading affects units in field tests. This is because snow loads, temperature fluctuations, and wind gusts create mechanical stresses and associated strain and elongation in the modules. This leads to material fatigue in 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," explains Fromm.
Even light winds cause module oscillations
To be able to grasp the effect of these influences on the material, the researchers equipped a complete solar modul
|Contact: Alexander Fromm|