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Munisami, Kevin Jagadissen (2011) Novel technique for solar power capture using plastic optical fibres. Doctoral thesis, London Metropolitan University.
The design and performance of a novel low cost technique for solar power capture, for daylighting applications, is investigated both theoretically and experimentally. Unlike other fibre optic daylighting systems, this method uses Plastic Optical Fibre (POF) not only as the light transportation medium but mainly as the light collecting mechanism. This technique is implemented using POF as these offer considerable advantages over glass fibre. The light collecting arrangement consists of the curved surface of a POF that is structurally modified so that solar light can be directed into the fibre by using an analogous process to fibre side emission but in the reverse. Two types of modification are investigated, grooves and sandblasting. The roughened surface of the POF scatters the incident light into the fibre core some of which is refracted out of the fibre while some other undergoes total internal reflection (TIR) and propagates inside the core and is finally collected at the fibre ends.
One major advantage of this technique is the elimination of one of the two axes (orbital) of solar tracking and the considerable decrease in importance of the second axis (seasonal), currently a necessity in other daylighting systems. This reduces the number of mechanical components and therefore renders the system less bulky, less costly and with lower demands on maintenance. Concentration optics, such as lenses, are not used.
Theoretical investigations, which showed that the introduction of a curve on the POF could eliminate one of the two axes of solar scanning and the inherent curvature of the POF which near eliminate the second one, are confirmed by computer modelling over a range of at least ±50°. Analytical investigations also confirm this hypothesis and the elimination of the orbital tracking axis.
Theoretical analysis characterised sandblasting and experimental work confirms that sandblasting can be used as a means to scatter light into the POF core. Two laser sources, 543nm and 632.8 nm, were utilised and confirmed the increase in full width half maximum (FWHM) angles by an average of 35°. Larger FWHM angles but with a decrease in intensity were demonstrated when the angle of incidence was increased.
Experimental work showed that straight 1mm POF resulted in a light capturing efficiency of 0.008%. Grooving the fibre improved this efficiency to 0.11% while sandblasting increased that further to 0.41%. The efficiency of sandblasted POF was found to be 4.01% for 2mm and 6.16% for 3mm POF. The theoretical calculations which pointed out that one of the two axes of solar tracking (orbital) could be eliminated and the importance of the second (seasonal) could be decreased considerably were confirmed experimentally.
The principle of operation behind this novel light capturing technique was confirmed both theoretically and experimentally and various attractive features unique to this system have been demonstrated. Suggestions for future work are also offered.
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