Daylighting through light pipes for deep interior illumination with consideration of heat gain | |
| Author | Vu Duc Hien |
| Call Number | AIT Diss. no.ET-07-01 |
| Subject(s) | Daylighting Interior lighting |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Electric Power System Management, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ET-07-01 |
| Abstract | Daylighting offers great potential for application in tropical regions because daylight is highly available near the equator, where the sky is luminous and overcast sky conditions occur infrequently. Traditional methods of daylighting utilizing daylight from the sky (skylight) through windows on the side of a building (sidelighting) require extensive shading to prevent direct light from the sun (sunlight) from entering since it will introduce excessive radiation into the interior, which is now extensively air-conditioned. Another drawback of sidelighting is that the level of resulting illuminance falls exponentially with distance from the window into the interior. The non-uniform workplane illuminance distribution and luminance gradient within the space can also result in an uncomfortable lighting environment. Use of light shelves might help overcome this limitation to some extent but their applicability and effectiveness are limited to certain times of a day and to certain months of the year in tropical region. A light pipe-reflector system is one of the configurations that can provide higher workplane illuminance levels deeper into a space over substantial daytime periods during the year. Study of the use of an adjustable reflector for reflecting sunlight through light pipe to illuminate the deep interior space of a building is the subject of this dissertation. In lighting, daylighting, and radiation heat transfer analyses, numerical values of form factors of different configurations are required. This dissertation starts with development a numerical approach for calculation of the form factor between two polygons. The approach used is based on dividing each polygon into triangles and subdividing each triangle into identical incremental triangles to evaluate the double area integral of the form factor under deterministic and Monte Carlo schemes. The study then develops a mathematical model and a computer program for calculation of illumination on surfaces of a light pipe and in a room. A ray tracing technique is used to calculate beam sunlight reflected from reflectors into the light pipe and its reflection at the end of the light pipe into the deep interior space in the room. Inter-reflection of diffuse light flux is used for calculation of resulting illumination on surfaces of the room. The light pipe is envisaged to be situated above the ceiling where radiation heat gain through light pipe will affect heat transfer into the space below. Evaluation of the heat gain to a room is needed to determine the thermal effect of the light pipe-reflector system. The development of a model for unsteady heat transmission through the building envelope is presented. The backward finite difference method is used for the solution of heat diffusion equations. A dynamic equation is also written for the transfer of heat and moisture to the air in each interior zone. The methodologies were then applied to a study on heat transmission through the roof for various configurations including the use of a radiant barrier (thermally reflective sheet) placed in the roof plenum of air-conditioned buildings. The methodologies were also applied to a light pipe-reflector system including static reflectors and an adjustable reflector that was designed to provide illumination on the workplane in the deep interior space. The approach developed and used for obtaining results differs from the approach taken by well-known researchers in developing a methodology for calculating interior daylight illuminance from the use of vertical light pipes. Experiments with the light pipe-reflector system are reported in detail, along with development of a computer program to assist in the calculation. Experimental values are compared with results from output of computer program. The results of calculation using the approach described in this dissertation agree well with experimental results. The experimental and calculation results demonstrate that daylighting through light pipes can provide acceptable illuminances in deep spaces for 9 hours per day under clear-sky conditions. |
| Year | 2007 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ET-07-01 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Surapong Chirarattananon; |
| Examination Committee(s) | Kumar, Sivanappan ;Guha, Sumanta ; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2007 |