Islam A. Mashaly

Illumination of dense urban areas by light redirecting panels

With the high population growth rate, especially in developing countries, and the scarcity of land resources, buildings are becoming so close to each other, depriving the lower floors and the alleys from sunlight and consequently causing health problems. Therefore, there is an urgent need for cost-effective efficient light redirecting panels that guide sun rays into those dim places. In this paper, we address this problem. A novel sine wave based panel is presented to redirect/diverge light downward and enhance the illumination level in those dark places. Simulation results show that the proposed panel improves the illuminance values by more than 200% and 400% in autumn and winter respectively, operates over wide solar altitude ranges, and redirects light efficiently. Experimental and simulation results are in good agreement.

Light redirecting system using sine-wave based panels for dense urban areas

Cities and towns around the world are becoming more condensed due to the shrinking amount of buildable areas, which significantly reduces the amount of light that occupants have access to. This lack of natural lighting results in health, safety and quality of life degradation. This paper presents a new technique of transmitting sunlight downward into narrow alleys and streets, by using a daylighting guiding acrylic panel that is capable of changing the direction and distribution of the incident light. The core of the proposed daylight guidance system is made up of light transmission panels with high quality. The corrugations have sine wave shaped cross-section so that the panel functions as an optical diffuser perpendicular to the direction of sunlight propagation. The day lighting system consists of the corrugated panels and a lattice frame, which supports the panel. The proposed system is to be mounted on the building roof facing the sun so as to redirect the incident sunlight downward into the narrow alleys or streets. Since building sizes and orientations are different the frame is arranged such that substantially deep light penetration and high luminance level can be achieved. Simulation results show that the proposed panel improves the illuminance values by more than 200% and 400% in autumn and winter, respectively, provides fan-out angle that exceeds 80° for certain solar altitudes and the transmitted power percentage varies from 40% to 90% as the solar altitude varies from 10° to 80°. Experimental results are in a good agreement with the simulations.

A New Dynamic Climate-Based Daylight Metric for Sustainable Building Design in Hot Climates

Daylight performance metrics are moving away from the traditional daylight factor and average illuminance to more climatic-based metrics such as Daylight Autonomy (DA) and Useful Daylight Index (UDI). These metrics offer a better measure of the daylight performance throughout the year and incorporate the varying weather conditions and as such are dubbed climatic-based metrics. However, in hot climates where the ratio of direct to diffuse is highest, achieving these metrics may result in over-heating the spaces. Achieving acceptable climatic-based metrics for the space may result in unacceptable heat gains. The Day light Autonomy and the Useful Daylight Index do not account for the total amount of lux-hours achieved throughout the year. The solution thus far has been to run coupled-energy and daylight simulations and in order to assess the effect of achieving certain climatic-based metrics on the heat gain and thermal performance of the space. In this paper a new metric is proposed that takes into account the total amount of lux-hours achieved throughout the year and the irradiation for different time step into a single measure. Details about the measure and sample test cases are presented.