Spectrophotometry

Summary

Spectrophotometry is a branch of electromagnetic spectroscopy concerned with the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry uses photometers, known as spectrophotometers, that can measure the intensity of a light beam at different wavelengths. Although spectrophotometry is most commonly applied to ultraviolet, visible, and infrared radiation, modern spectrophotometers can interrogate wide swaths of the electromagnetic spectrum, including x-ray, ultraviolet, visible, infrared, and/or microwave wavelengths. Overview Spectrophotometry is a tool that hinges on the quantitative analysis of molecules depending on how much light is absorbed by colored compounds. Important features of spectrophotometers are spectral bandwidth (the range of colors it can transmit through the test sample), the percentage of sample-transmission, the logarithmic range of sample-absorption, and sometimes a percent

Official source

https://en.wikipedia.org/wiki/Spectrophotometry

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

Carlos Pascual Agullo

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.

EPFL2014

Water Injection in isothermal co-rotating scroll compressor and turbine

Roberto Passini

This project deals with the study of a quasi-isothermal scroll compression/expansion obtained by spray injection of water. The spray injection process is first described from the theoretical point of view as it concerns the droplets formation and breakup processes, both directly related to the evaporation. A simulation of spray injection is also performed using Ansys CFX. The last part deals with an experimental application in the laboratory of the system studied. Results are presented and discussed both for CFD simulation and experimental part.

2012

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Glass fiber-reinforced polymer (GFRP) materials are increasingly used in building construction for the design of multifunctional structures. These composite materials allow the integration of structural functions, building physics functions (mainly thermal insulation) and architectural functions (complex forms and color) in single large-scale building components. GFRP materials also allow the fabrication of translucent structural components with high degree of transparency when optically aligned resins and glass fibers are used, i.e. their refractive indices are identical. In this study the total light transmittance of hand lay-up GFRP laminates for building construction was investigated with a view to two architectural applications: translucent load-bearing structures and the encapsulation of photovoltaic (PV) cells into GFRP building skins of sandwich structures. Spectrophotometric experiments using an integrating sphere set-up were performed on unidirectional and cross-ply GFRP specimens in the range from 20% to 35% fiber volume fraction. Results were compared with the shortcircuit currents generated by amorphous silicon (a-Si) PV cells encapsulated in GFRP laminates exposed to artificial sunlight radiation. The total amount of fibers in the laminates was the major parameter influencing light transmittance, with fiber architecture having little effect. 83% of solar irradiance in the band of 300-800 nm reached the surface of a-Si PV cells encapsulated below structural GFRP laminates with a fiber reinforcement weight of 820 g/m2, demonstrating the feasibility of conceiving multifunctional GFRP structures.

EPFL Solar Energy and Building Physics Laboratory (LESO-PB)2013

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

Carlos Pascual Agullo

EPFL2014