Aljudaiy, Fawzan
(2022)
A novel integrated daylighting system for optimal daylight performance in office buildings.
PhD thesis, University of Nottingham.
Abstract
The thesis assessed the potential of optimising the daylight performance for an office building in Riyadh city, Saudi Arabia, by means of a novel passive daylighting system that can achieve balanced daylighting performance. The function of the proposed system is to prevent and mitigate the negative impact of direct sunlight inside the building by reducing the illuminance level in the front area while increasing it in the deep area of the space. The aim was to reduce the annual level of sunlight exposure (ASE) while increasing the daylight autonomy (DA), the useful daylight illuminance (UDI) and the daylighting uniformity at the work plane. This aim was achieved through four objectives, to assess the current situation of the daylighting performance for typical office space, to invent a novel integrated daylighting system that can enhance the daylighting performance, to optimise the design of the proposed system and finally to assess the daylighting performance of the proposed system.
A novel integrated daylighting system that consist of a perforated solar screen (PSS) and daylight-redirecting devices (DRDs) was designed. The PSS was optimised by examining the effect of the perforation percentage on the daylighting performance. Next, the impact of the DRD on the daylighting performance was investigated. The tested parameters include the position, per unit area ratio, material, geometry, tilt angle and truncation. Finally, a prismatic lens was integrated within the DRD and its impact was evaluated.
The daylighting performance of the case study was evaluated for Riyadh city, Saudi Arabia. First, the redirection of the sunbeams was analysed through a raytracing study. Afterwards, the illuminance levels at the workplane were assessed using climate-based daylight modelling. The annual daylighting performance was evaluated for the whole year and each season. Furthermore, the hourly daylighting performance was assessed between 8 am and 4 pm on the summer solstice, autumn equinox and winter solstice days at 2-hour intervals. Later, experimental tests for a prototype model under an artificial sun simulator were conducted. Finally, the simulation modelling results were validated against the outputs of the experimental test for a prototype-scale model under real sky conditions.
The results of the study revealed that the daylight uniformity was enhanced by the proposed system compared to the base case and the perforated screen. The daylight uniformity was enhanced by case DRSS11-B for most of the tested hours. A significant improvement was recorded on 21 December. The daylight uniformity was increased from 2% to 22% compared to the base case. In addition, the daylight uniformity on 21 June and 21 September reached up to 32% whereas the highest uniformity was19% and 28% for the base case and the PSS, respectively.
Furthermore. the annual analysis of the daylighting performance indicates that the proposed system reduced the negative impact of direct sunlight. The ASE value was reduced from 381 hours to 121 hours by case DRSS11-B and 186 hours by case PSS5 compared to the base case. On the other hand, the DA value analysis showed that at daylighting zones Z1 and Z2 the performance was similar among the tested cases, namely, the base case, case PSS5 and case DRSS11-B. The DA value was 100% at Z1 and 97 to 98% at Z2. However, the highest DA values at Z3 was 72% for case PSS5 with an increase of 3% and 6% compared to the base case and case DRSS11-B, respectively. Nevertheless, the UDI values revealed that the at daylight zones Z1 and Z4, case DRSS11-B increased the UDI values from 1% and 3% to 5% at Z1, and 5% and 15% to 17% compared to the base case and case PSS5, respectively.
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