Advanced Encapsulants for Reduced Thermal Mechanical Stress in Photovoltaic Modules: A Quantitative Analysis Using FBGS

In this work, two mini-modules using a 3D multi-ribbon interconnection are fabricated. One with TPO and the other with glass fiber reinforced TPO (GF TPO) encapsulant. Using fiber Braggs grating sensors (FBGS) attached to the cell, in situ temperature and strain are quantified during reliability tests in the form of thermal cycling from -40°C to +85°C. It was found that the temperature of the cell surface reaches -36°C and +81°C at its minimum and maximum respectively. The measured cell strain followed the same cycling behavior between tension and compression. The strain in the GF TPO based module was found to have a lower peak-to-peak (difference between max tension and compression) value. Also, a consistent difference between strain in parallel and perpendicular directions relative to the busbars was observed, with the latter one being larger.