Papers by Keyword: Non-Imaging Optics

Abstract: Fenestraria aurantiaca (also known as window plant) is a succulent with specialized adaptations to deal with heat, light and aridity. Fenestraria aurantiaca (F. a.) grows with most of its body under the sand. Just the top, with a light transparent surface – the window – on it, protrudes from the surface hence giving explanation to the plants name. Experiments with light, and detailed microscopy studies show the physical, biological and chemical capabilities of F. a. It was found that the window works as a lens, light from a 90 ° angle is directed into the plant. Thereby the window filters the light. Up to 90 % of the visible light is blocked; with rising wavelength the window gets more transparent until the near infrared light (1000 nm) where the transparency declines rapidly. But the parenchyma is up 90 % transparent. Based on those results the principles of the plant were defined, which are used for abstractions. Generally F.a. has four principles: light handling, surface cleaning, heat avoidance and water storing. Improvements founded on the inspiration of the window plant seem to be possible in photovoltaic systems, which have problems with overheating and also light concentration. An example solution called “buried solar cells” is presented. Another working field is the screen of mobile devices, where the clarity and readability suffers from direct sunlight. With the help from the methods displayed by F.a., there is an energy saving solution explained.

Abstract: The use of solar divergence collimators is the key for reliable optical tests that reproduce the on-field collector operating conditions. Aiming to test small (<80 mm diameter/diagonal) and large concentrators (80-240 mm diameter/diagonal range), the collimator geometry should be evaluated because of some optical errors introduced by the need of bending the optical axis. This paper discusses the optical characteristics of the beams obtained with straight and bent collimators with solar divergence. The collimated beams are examined by ray tracing simulations, studying the aberrations as a function of bend angle, and measured in laboratory. Finally characterisation tests for sunlight concentrators of various shapes, dimensions and collection features are presented describing instrumentation, optical set-up and methodology to determine collection efficiency, image plane analysis and spot size.