Efektivitas Daylight Mirror Shaft sebagai Sistem Pencahayaan Alami Ruang Bawah Tanah pada Langit Tropis

Title: Effectiveness of Daylight Mirror Shafts as Natural Daylighting System for Basements under Tropic Sky Conditions Basements have lots of potential as functional spaces, but have mostly been neglected due to lighting issues. Therefore, this study will explore the daylight mirror shaft system as a daylight strategy for basements, which features the placement of a reflecting surface on a light shaft to redirect daylight. The system was introduced by Heliobus®, a daylighting company from Switzerland. To see the effectiveness of implementing the system in Indonesia, a study was made on its performance on the climate sky condition. Furthermore, a study was made on the effect of different opening orientations and light shaft placements toward the illuminance level achieved. The lighting data was obtained using the simulation softwares Lightstanza. Results show that the performance of the system on climate sky condition can provide sufficient light for 41% of a basement. The use of mirrors on the light shaft could also increase the lighting levels by 2.1 times compared to a shaft without a mirror. Moreover, it was found that different opening orientations and light shaft placements didn’t give a significant effect on the lighting quantity. Overall, the study shows that the system’s implementation on climate skies still require adjustments through further studies to be effective.

The effects of wind velocity and building geometry on air change efficiency in light shafts: Case studies

The evaluation of the air quality in light shafts requires a specific study of its air renewal ability due to building shape, dimensions and other external conditions. This research has studied the capacity of light shafts to provide natural ventilation through the air change efficiency concept. A methodology based on the limitation of the computational urban domain is used to adapt the indoor air change efficiency index for outdoor environments. Numerical simulations were performed using CFD and a model that was experimentally validated. The aim is to evaluate the effect of the centreline building width and light shaft dimensions in the air change quality within several wind climates. Results would provide a numerically proven tool for designers, summarised in some design-based strategies in order to select which one improves the air change quality. The results indicate that the light shaft dimension perpendicular to the wind direction has a negligible effect on efficiency. For the range of wind velocities studied (0.75–9.00 m/s), the efficiency decreases at higher velocities, up to −7.41% with respect to the mean. For variations in the wind velocity and the centreline building width, a mean variation of ± 18.77% in the efficiency is obtained. Practical applications: The present methodology defines a proceeding to numerically evaluate the air change efficiency in light shafts inside different dimensional cases of buildings within several urban wind conditions.

An Innovative Vertical Axis Current Turbine Design for Low Current Speed

This article presents the new innovative concept for optimal design of Vertical Axis Current Turbines (VACT) applicable in low current speed which is being increasingly used to harness kinetic energy of water and convert it into other useful forms of energy as a clean and renewable energy. Widespread commercial acceptability of these turbo machines depends upon their efficiency. This largely depends upon the geometric features of the hydro turbines such as operation of designed system, joints, number and shape of blades and etc. The concept of VACT was proposed to provide a solution for the case of low current force inflow to vertical axis turbines. VACT has four suitable blades with flexible hinge joint to guide the water in come to reduce the drag force, light shaft and arms with stiff metal to make rigid and strong structure. The current study discusses the components of VAC turbine, rigidity of structure, performance, executive concept, efficiency, material, gearbox, environmental impacts and prevention of water corrosion. The new proposed innovative concept of VACT has flexible hinge connection for changing the blades directions automatically to reduce hydrodynamic drag and increase the hydrodynamic pressure to rotate the main shaft and enhance the efficiency as well. Main shaft connected to epicyclical gearbox to provide the higher torque for maximum electric power generation.

Shafts for daylighting underground spaces: sizing guidelines

This paper presents an experimental study on Daylight Factors (DFs) distribution in underground multi-level open spaces which use continuous light shafts to reduce energy consumption by the artificial lighting system and to improve the human acceptability of the spaces. Experimental measurements were carried out in a scale model, which could be assembled to provide different shapes and could be placed in an unobstructed site. The use of a real sky, which very seldom shows a fully overcast CIE luminance distribution, required the development of a special procedure to guarantee the accuracy of the experimental results. Level height, slab floor thickness, aspect ratio and glass covering of the light shaft were some of the parameters considered. Measured DFs were correlated by dimensionless parameters and reported in the form of charts which can be used to size the width of the shafts on the basis of the required illuminance and on the frequency distribution of the diffuse natural illuminance. An example of DFs calculation for an underground space is also reported.