Translucent load-bearing GFRP envelopes for daylighting and solar cell integration in building construction

This project investigates the light transmittance of load-bearing glass fiber-reinforced polymer (GFRP) laminates with a view to two architectural applications: the daylighting of buildings through load-bearing translucent GFRP envelopes and encapsulation of solar cells into the GFRP building skins of sandwich structures. The total and diffuse visible light transmittances of the laminates were experimentally investigated using a spectrophotometer coupled to an integrating sphere. The refractive indices of polymeric resin and glass fibers were also investigated and numerical ray-tracing simulations were performed to demonstrate the experimentally observed wavelength dependency of light diffusion. The total transmittance and translucency of GFRP laminates were analytically modeled as a function of the reinforcement weight, fiber architecture and fiber volume fraction. Goniophotometric experiments – performed to investigate the directional light scattering of laminates reinforced with different fiber architectures – were demonstrated as an effective method to predict the fiber architecture of translucent GFRP laminates. The optical properties of the laminates, i.e. the total and diffuse transmittances and directionality of light diffusion, were correlated with the experimentally investigated mechanical properties, i.e. the directional tensile strength and E-modulus. The experimental work demonstrated that structural skylights could be designed with GFRP laminates exhibiting a translucency of 0.9 and total light transmittance of 0.5 – minimum values recommended for daylighting of buildings through translucent envelopes – and that solar cells could be encapsulated in load-bearing GFRP laminates with a total light transmittance of around 0.83. A case study was performed using the GFRP/polyurethane sandwich roof of the Novartis Campus Main Gate Building to demonstrate the basic feasibility of integrating skylights and solar cells into the external translucent skin of optimized sandwich structures. Finally, the encapsulation of transparent and colored dye solar cells in translucent GFRP laminates has been explored. Prototype solar panels have been fabricated and a significant weight reduction, increase in structural strength and around 10% reduction of electrical efficiency compared to traditional solar panels with glass encapsulants were achieved.