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Title: Optimising the Performance of Innovative Daylighting Systems by Integrating with Ceiling Geometries.
Author: Freewan, Ahmed A.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2007
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Abstract:
Daylighting improves visual environment, enhances human productivity, and reduces fossil fuel consumption and C02 emissions and thus decreases global warming. The contradiction between daylighting and heat gain in hot climates requires innovative daylighting systems that provide illumination to buildings while controlling the heat gain. Several innovative daylighting systems were developed to provide such a balance between daylighting and shading such as lightshelves, louvers and laser cut panel (LCP). The thesis objectives are to investigate the effects that ceiling geometries could have on the performance of the innovative daylighting systems, to optimise the performance of the daylighting systems by manipulating variables like lightshelves, and louvers geometries, and sloped angle, rooms heights and reflectance, to provide design guidelines for buildings designers to incorporate daylight buildings design and to ease daylight application in hot climates with contradictory situation. Optimising the performance of the innovative daylighting systems was assessed by modifying ceiling geometries, space parameters and systems parameters. Experimental studies using physical models under artificial light, artificial sky and real sky were conducted. The ceiling geometries were found to have significant effects on the performance of lightshelves, louvers and laser cut panels (LCPs). Curved and chamfered ceilings improved the performance of the innovative daylighting systems by reducing the illuminance level in the front part and increasing it in the rear part. Radiance simulation confirmed the effects of ceiling geometries on the performance of systems and agreed well with the experiment results under overcast and clear sky conditions. Therefore Radiance was used to optimise the performance of the innovative daylighting systems using ceiling parameters, space parameters and the innovative system parameters. Ceiling geometries, room height II I' Ii '·I'iI' . 'I! I: r i I'· I.' i. I, '' 'j; 'ii , ij , Ii I I I I I I I I I - '.. _ . . and lightshelf and louvers shape were found to have significant effects on the lightshelf and louvers perfonnance. On the hand, ceiling geometries and width to cut .ratio have significant effects on the LCP perfonnance. A curved ceiling could increase the illuminance level in the rear part of a room served by a lightshelfby 30%, while a chamfered ceiling improved it in a room with louvers by an average of 24%. Lightshelf geometries like a curved lightshelf could increase its perfonnance by up to 30% compared to a horizontal lightshelf. On the other hand, arch and angled louvers could improve the louvers perfonnance by up to 13%. Moreover curved ceilings could improve the perfonnance of LCPs by an average of 35%. These variables could increase the amount of light delivered deep into a room and direct the light to the required area. The best ceiling geometry, was the curved ceiling for lightshelves and LCPs and chamfered ceiling for the louvers7 Curved lightshelves and louvers perfonned better than flat lightshelves or louvers in addition increasing the room height improved both the illuminance level and unifonnity ratio. The lightshelf could be used in a large space up to 12m in depth, if combined with a curved high ceiling with specular reflectance in the front part, and a white back wall.
Supervisor: Not available Sponsor: Not available
Qualification Name: University of Oxford, 2007 Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.489967  DOI: Not available
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