Thermomechanical deformations in photovoltaic laminates

Recent experimental results based on the digital image correlation technique (U. Eitner, M. Köntges, R. Brendel, Solar Energy Mater. Solar Cells, 2010, 94, 1346–1351) show that the gap between solar cells embedded into a standard photovoltaic laminate varies with temperature. The variation of this gap is an important quantity to assess the integrity of the electric connection between solar cells when exposed to service conditions. In this paper, the thermo-elastic deformations in photovoltaic laminates are analytically investigated by developing different approximate models based on the multilayered beam theory. It is found that the temperature-dependent thermo-elastic properties of the encapsulating polymer layer are responsible for the deviation from linearity experimentally observed in the diagram relating the gap variation to the temperature. The contribution of the different material constituents to the homogenized elastic modulus and thermal expansion coefficient of the composite system is also properly quantified through the definition of weight factors of practical engineering use.