Daylight Illuminance in Classrooms Adjacent to Covered and Uncovered Courtyards Under The Clear Sky of Najran City, Saudi Arabia

Daylight penetrating the classrooms makes students efficient, improves overall health and increases energy efficiency. In the hot regions, the concept of courtyards in buildings is deeply linked to the architecture as a sustainable solution to daylight indoors without negatively affecting the building cooling loads in the summer. Najran University has existing courtyards in college buildings. Recently, the university covered the courtyards using PVC canvas. This study aims to investigate and compare the daylight illuminance in classrooms adjacent to covered and uncovered courtyards. A case study of four classrooms in the College of Engineering was investigated under the clear sky of Najran City. Results showed that the daylight illuminance in the classrooms adjacent to the uncovered courtyard was low with a maximum of 100 lux close to the windows when outdoor illuminance was 110 Klux. However, the indoor daylight illuminance in the classrooms adjacent to the a covered courtyard was 18, 10 and 7 lux, with 1, 3 and 5 m distance from the window, respectively. These classrooms depend mainly on electrical lighting

Performance of the glazed facades with a flowing sustainable water film exposed to direct solar radiation under the Malaysian climate / Abdultawab Mohammed Qahtan

On the east and west orientations of the glazed buildings in the tropics where the solar altitude is low, the solar energy transmittance can not be effectively controlled by shading, except by blocking most of the glazed facades. Wherein, the daylight would be sacrificed. Based on this premise, to reduce the transmittance of solar energy without sacrificing daylight, the appropriate solution is the use of high performance insulated glazing system with spectrally selective coatings that distinguish between visible range (daylight) and infrared range (heat). Nevertheless, the drawback is its high capital cost. This study seeks to improve the control of total solar energy transmittance by exploitation the potential of recycled elements in such tropical countries combined with low cost glazing. The study examines the effectiveness of Sustainable Glazed Water Film (SGWF) in reducing the solar heat transmittance and maximizing the solar light transmittance indoors. The Malaysian climate and green-glazed buildings have been discussed to provide a direction to select the appropriate alternative solar control that copes with the east and west glazed facades in the tropical countries. SGWF was suggested as an alternative solar control and was numerically and experimentally investigated on glazed facades of west orientation, in the University of Malaya’s campus. The experiments involved a study of three parameters namely: water flow rate, types of glazing, and the solar radiation intensity. The effect of water film thickness was also discussed. Two full-scale rooms were used, one as a reference room, with a fixed configuration, and the other as a test room, which could be configured in different ways. It was found that the flowing water film on the glazed facades lowers the glazing surface temperature by 7.2 to 14°C (average) and absorbs a portion of the solar energy xx thus resulting in a decrease in the indoor temperature by 2.2 to 4.1°C (average). On the other hand, although about 70% of the short infrared ranging between 1300nm and 2500nm are totally absorbed by the thin water film, the solar radiation transmittance behind the SGWF facade increased by 2% to 6.8% compared to the facade without water film. This is because the water film acts as an anti-reflective coat to transmit the entire visible light range hence reducing its reflection outwards compared to dry glass. It was concluded that the sustainable spectrally selective feature of the SGWF improved the performance of glazed buildings by reducing the solar heat (or infrared) transmittance and maximizing the solar light (or visible light) transmittance indoors. From the study it can be summarised that significant energy could be saved by adopting the SGWF facade. It was observed that, (a) a reduction of 24.6% of the total energy cooling could be achieved as compared to an identical system without water film; (b) the reduction in glass surface temperatures contributed to the reduction of surrounding temperature (heat island effects) that affects the indoor environment; and (c) the increase in the visible light transmittance resulted in the reduction of the energy required for artificial lighting

Experimental Evaluation of Thermal and Lighting Performance Using Double Dynamic Insulated Glazing

Designing windows in hot climates that allow occupants to easily control their preferences in a smart home is of considerable importance. This paper aims to contribute to this topic by examining the potential of a smart window system that has double dynamic insulated glazing (DDIG) in preventing heat gain and maximising daylight indoors, considering smart privacy protection during both the day and the night. A small-scale model was developed to examine the proposed window system. Test cell temperature, glass surface temperature and indoor illumination lux were investigated. The results showed that the DDIG had high solar heat control inside the test cell, with a significant reduction of 2.5 °C compared with the common glazing of translucent glass used in Najran City, Saudi Arabia. At high solar irradiation intensities, no significant differences in controlling the heat gain to the test cell were found between coloured DDIG (DDIG-colo) and transparent DDIG (DDIG-trans). A graded reduction between DDIG-trans and DDIG-colo was found with decreasing solar intensity, which was found to be 15%, 10% and 8.7% at irradiation intensities of 200, 400 and 600 W/m2, respectively. The DDIG transparencies maintained the illumination lux with higher reduction under low solar irradiation. The DDIG also provided privacy protection and granted user preferences for outdoor connections

A case study to assess the near-glazed workplace thermal performance

Passive solar control solutions have been widely used in buildings in tropic countries like Malaysia. It is assumed that these solutions may notably control the heat-gain of buildings. However, there is a lack of empirical studies that assess the extent of green-glazed techniques to sufficiently control solar heat-gain. The current study uses a case study approach to examine the thermal indoor performance, particularly the near-glazed workplace area. The performance of the ST Diamond Building (in Putra Jaya, Malaysia) has been examined in terms of: outdoor/indoor dry bulb temperature; glass surface temperature; heat flux through glazing; outdoor/indoor air movement; lux and; solar radiation. The results of the field analysis indicated that ST Diamond Building’s green-glazed solutions are efficient to control solar heat gain, which in turn will lead to reduce energy consumption for controlling solar heat loads

Energy efficient and privacy protection window system for smart home using polymer-dispersed liquid crystals glass

Hot climates smart home system is steadily advancing recently. The main concern is energy efficiency particularly in the Arabian Gulf region. Privacy is another prioritized concern culturally. This project presents a solution for both demanded priorities implementing a polymer-dispersed liquid crystals (PDLC) glass system. The proposed design was validated via a developed prototype that was measured experimentally. Its experimental results show about 39% improvement in energy saving compared to conventional systems without depriving the indoor-outdoor connections and the privacy of the smart home inhabitants. Furthermore, it also achieves several other additional goals, for instance, decreasing cost as well as wasted energy by automatically off the lighting and air conditioning systems whenever they are not in used. Moreover, it is also capable to significantly reduce the risk of harmful exposure to ultraviolet A/B (UVA/B) of solar radiations, which conventional curtains are not capable to protect