Characterization of Lightweight Polymeric Honeycomb Structures for Use as Backsides in Glass-Free PV Modules

Abstract

In densely populated or mountainous countries where installation of large-scale solar plants is challenging, photovoltaic (PV) modules in building applications offer a solution by transforming passive surfaces into energy-generating systems. The need for flexible, lightweight, and “invisible” PV modules, with a life-time of over 20 years, comparable performance to the standard modules, and enabled recyclability resulted in various designs on the market. This research focuses on thermoplastic honeycomb sandwich composites (HSCs) with glass fiber-reinforced polymer skins as potential lightweight backsides for PV modules. Through material characterization and damp heat testing, their optical, mechanical, and thermal performance, compatibility with lamination processes, and ability to protect internal components from UV radiation and humidity were evaluated. Results show that proper glass fiber embedment improves mechanical properties and reduces water vapor transmission rates. Semitransparent skins could enable bifacial PV modules but require UV absorbers for long-term stability. HSCs exhibit glass-like thermomechanical behavior but low thermal conductivity, which could affect module temperature regulation. Damp heat exposure caused minor degradation in PP-based materials, while PET materials experienced polymer chain-scission and significant material embrittlement, which indicates the need for improved hydrolysis resistance.