Non-ultraviolet (UV) photoexposure of luminescent solar concentrators (LSC's) can produce photoproducts that cause additional extinction at wavelengths somewhat longer than the main dye absorption peak. This photo-induced 'tails' extinction is deleterious to luminous output in collectors of useful lengths. An experimental method that enables the subdivision of tails extinction in an LSC into absorbed and scattered components is described. The relevant theory is outlined, and experimental results are presented for a polymethyl methacrylate (PMMA) LSC containing Lumogen F083 dye. For this sample, tails absorption increased significantly with outdoor exposure, while tails scattering remained constant. Further measurements indicate that LSC luminous output is around five times more sensitive to tails absorption than to fluorescence quenching. This work also indicates that merely checking for dye quenching, as is often done, can be a misleading indicator of long-term LSC output. (C) 2010 Elsevier B.V. All rights reserved.

Fluorometers are widely used in ecosystem observing to monitor fluorescence signals from organic compounds, as well as to infer geophysical parameters such as chlorophyll or CDOM concentration, but measurements are susceptible to variation caused by biofouling, instrument design, sensor drift, operating environment, and calibration rigor. To collect high quality data, such sensors need frequent checking and regular calibration. In this study, a wide variety of both liquid and solid fluorescent materials were trialed to assess their suitability as reference standards for performance assessment of in situ fluorometers. Criteria used to evaluate the standards included the spectral excitation/emission responses of the materials relative to fluorescence sensors and to targeted ocean properties, the linearity of the fluorometer's optical response with increasing concentration, stability and consistency, availability and ease of use, as well as cost. Findings are summarized as a series of recommended reference standards for sensors deployed on stationary and mobile platforms, to suit a variety of in situ coastal to ocean sensor configurations. Repeated determinations of chlorophyll scale factor using the recommended liquid standard, Fluorescein, achieved an accuracy of 2.5%. Repeated measurements with the recommended solid standard, Plexiglas Satinice® plum 4H01 DC (polymethylmethacrylate), over an 18 day period varied from the mean value by 1.0% for chlorophyll sensors and 3.3% for CDOM sensors.

The photodegradation rate of a perylene dye (Lumogen F Yellow 083) in methyl isobutyrate was found to increase with ketone concentration for two different ketones. Of the ketones employed, methyl pyruvate, an impurity in methyl methacrylate, was found to be particularly deleterious to dye stability. In agreement with other published studies, the addition of the anti-oxidant DABCO (1,4-diazabicyclo-[2.2.2] octane) to the dye matrix was found to increase dye stability; however when ketones were present, DABCO lead to increased photodegradation. These results highlight the importance of removing ketone impurities from dye matrices during production of Luminescent Solar Concentrators (LSCs).

For real diffuse surfaces, the bi-directional reflectance distribution function (BRDF) is non-Lambertian, and may require a more complex model in ray tracing simulations. The BRDF of a diffuse white surface is studied at multiple angles of incidence, and an additional reflectance component is observed, which becomes more specular as the angle of incidence increases. For angles of incidence >85°, the BRDF may be regarded as specular. In this article, a two-part model is proposed in which the BRDF of a diffuse surface consists of a Lambertian diffuse component and a Lorentzian pseudo-specular component — both of which vary with angle of incidence. This model may be used to reduce computation times for ray tracing simulations, as an alternative to large three-dimensional BRDF datasets.

Energy efficient coloured paint coatings utilising flaky aluminium pigment with either single layer (Fe2O3) or double layer (Fe2O3 on SiO2) interference coatings are optically and thermally characterised. Similar pigments with coatings on flaky dielectric particles and standard paints of similar colour are compared. Data presented includes hemispherical and specular reflectance spectra across visible and infra red wavelengths, thermal emittance from an emissometer and light spreading data from a photogoniometer. Solar absorptance, and colour show that, as theoretically predicted, and provided flaky metal pigments are used, a wide range of colours combined with a much lower solar absorptance than traditional paints of similar colour is achieved. Superior thermal performance to ordinary paints with similar colour is thus possible and is demonstrated for two such coloured layers via controlled heating-cooling studies under both an indoor lamp and outdoor clear sky solar illumination. It is seen that heat gains from the sun and associated cooling loads can be reduced by up to 50% for most colours, which is of some benefit for cars and metal roofs in hot climates.

Flakes of metal coated with thin dielectric films, when used as various coloured paint pigments, can reflect much more of the near infra red component of solar radiation than standard paints of equivalent colour, which makes them attractive for reducing cooling loads in cars and under metal roofs, while maintaining a wide range of decorative options. Spectral responses, solar absorptance and CIE colour co-ordinates are explored theoretically for a single layer, and two layers of different refractive index, on smooth aluminium flakes. Results in air, and in a clear matrix of refractive index close to that of the paint binder, are presented to highlight the colour shifts that are observed in a matrix when colour is due to interference. Thin film models show that the single layers have weak angle of incidence dependence while double layers have attractive variations in reflected colour while retaining their high NIR reflectance. This adds to decorative appeal. The origins and impact of diffuseness are briefly discussed.

Simple quantitative performance criteria are developed for translucent materials in terms of hemispherical visible transmittance, and angular spread of transmitted luminance using a half angle. Criteria are linked to applications in luminaires and skylights with emphasis on maximising visible throughput while minimising glare. These basic criteria are also extended to angle of incidence changes which are substantial. Example data is provided showing that acrylic pigmented with spherical polymer particles can have total hemisphercial transmittance with weak thickness dependence, which is better than clear sheet, while the spread of transmitted light is quite thickness sensitive and occurs over wider angles than inorganic pigments. This combination means significantly fewer lamps can achieve specified lux levels with low glare, and smaller skylights can provide higher more uniform daylight illuminance.

This chapter discusses material properties for advanced daylighting in building. Some recent developments in materials used to illuminate interior and exterior spaces with daylight, and mathematical modeling of their interaction with light for design purposes are presented. The Sydney 2000 Olympic Stadium roof and a new solid light guide system are two examples. Emphasis is on making full use of the daylight resource, not just the diffuse component, while controlling the associated solar heat gain. Sensitivity to glare is essential if materials capabilities are to be realized. The clever use of natural light can save substantial energy, add new dimensions to the beauty and impact of interior and exterior spaces, and enhance the enjoyment and productivity of occupants. Daylighting, previously either undervalued due to an emphasis on thermal energy, or put into the "too hard basket" because of its relative complexity compared to thermal issues, is increasingly being recognized as a core issue in the new energy efficient design era.