Direct comparison of polymethylmetacrylate (PMMA) and silicone-on-glass (SOG) for Fresnel lenses in concentrating photovoltaics (CPV)

Hans Philipp Annen; Ling Fu; Ralf Leutz; Luis González; Jehu Mbakop

doi:10.1117/12.893884

13 September 2011 Direct comparison of polymethylmetacrylate (PMMA) and silicone-on-glass (SOG) for Fresnel lenses in concentrating photovoltaics (CPV)

Hans Philipp Annen, Ling Fu, Ralf Leutz, Luis González, Jehu Mbakop

Author Affiliations +

Proceedings Volume 8112, Reliability of Photovoltaic Cells, Modules, Components, and Systems IV; 811204 (2011) https://doi.org/10.1117/12.893884
Event: SPIE Solar Energy + Technology, 2011, San Diego, California, United States

Abstract

The CPV community is still undecided on one critical issue: what material to use best for Fresnel lens parquets. Reliability and longevity are the most important, but all other properties play roles as well. We have developed and manufactured Fresnel lenses with the two commonly used materials: PMMA (Polymethylmethacrylate) and silicone on glass (SOG). Both lenses are designed for the same optical train for best comparability. This allows for better understanding the pros and cons of the materials and making an informed choice for a specific CPV module. While PMMA lenses are embossed from pre-fab sheets in a hot-cold process, the silicone lenses are cast from a heat-curing silicone rubber at moderate temperatures, reducing the energy consumption. PMMA allows for the inclusion of custom low-profile 3D (2.5D) structures for module assembly and mechanical alignment, a feature not possible in silicone due to its low rigidity. Both lenses suffer from thermal expansion and refractive index change. While PMMA parquets expand isotropically, SOG prisms deform due to the difference of expansion coefficients between the glass and the silicone. SOG lenses are prone to delamination of the silicone film. The adhesive strength of the film to the glass can be measured using a modified blister test that we developed. The results show large difference with different materials and confirm the necessity of controlling this issue closely. While the small thermal expansion of the glass sheets allows for larger parquet sizes, the deformation of the prisms with temperature may cause a performance hit.

Citation Download Citation

Hans Philipp Annen, Ling Fu, Ralf Leutz, Luis González, and Jehu Mbakop "Direct comparison of polymethylmetacrylate (PMMA) and silicone-on-glass (SOG) for Fresnel lenses in concentrating photovoltaics (CPV)", Proc. SPIE 8112, Reliability of Photovoltaic Cells, Modules, Components, and Systems IV, 811204 (13 September 2011); https://doi.org/10.1117/12.893884

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