Authors: Rohit Thakur, Riya Malhotra, Ankit Bhalla, Sanjay Seth
Conference: Sixth Building Simulation and Optimisation Virtual Conference
Abstract: The climatological study of sky conditions and radiation is relatively new in India. Prediction of daylight availability in an interior space throughout the year is imperative for daylighting design. This prediction of daylight availability is made in absolute or relative terms to external illuminance. This paper aims to showcase the correlation analysis of the measured CIE sky and overcast Sky for equinox days; March 21 and September 21. VELUX daylight visualizer software were used to run a box model analysis to extract illuminance levels for a correlation study of observed CIE sky conditions with overcast sky conditions. From the correlation analysis of the simulated data, it is computed that the illuminance analysis perceived by daylight simulation considering measured sky conditions compared to overcast sky conditions on the analysis grid is 23% more accurate in March and 42% more accurate in September. Therefore, it can be affirmed that the computed set of CIE design skies shall be used to enhance the passive design of windows for the locations falling under the respective climatic zones for better cost optimization through accurate illuminance prediction.
Authors: Ankit Bhalla, Riya Malhotra, Rohit Thakur, Sanjay Seth
Conference: The Fourteenth International Conference on Advances in System Simulation
Abstract: In the past decade, numerous daylighting practitioners, architects, engineers, and researchers have progressively used daylighting simulation tools to estimate the daylight areas of building design. Most of these tools employ overcast sky conditions for daylight simulations. However, the accuracy and pertinence of such simulation tools for the tropical sky are uncertain. This study aimed to validate the computer-simulated result of overcast and actual sky models with physical test bed results measured under a real tropical sky. The considered space is modelled as per the constructed test bed space (Mahindra-TERI Centre of Excellence (MTCoE), Gurgaon, India) model to be tested under a real sky measurement. The same model was configured in VELUX Daylight visualizer 3.0 to perform daylighting simulation for March 21st, 2022, from 8:00hrs to 18:00hrs. All the illuminance measurements in the test bed were carried out under prevailing sky conditions in Gurgram, India. In contrast, related CIE sky conditions and overcast sky conditions were used for simulations to compare the results using the agreement of the index method. The International Commission on Illumination (CIE) sky conditions are very dissimilar from the actual tropical sky; simulated absolute value results such as external illuminance, absolute work plane illuminance and surface luminance recorded moderate mean differences from the measured results. Results indicate that the accuracy of illuminance levels increased by almost 24% through daylight simulations under actual sky conditions on March 21st (equinox day). Aimed at imminent research, other parameters can be validated, such as orientations, angle of the overhang, glazing, window sizes, colours, environment settings, and electric lighting.