| Author | Pipat Chaiwiwatworakul |
| Call Number | AIT Diss. no.ET-07-03 |
| Subject(s) | Daylighting--Tropics
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the
degree of Doctor of Engineering in Energy Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ET-07-03 |
| Abstract | This thesis study aims to investigate tropical daylight and its illuminance through side window. Issue of indoor daylight quality is included in consideration. The thesis study comprises three sub objectives; assessment of daylight illuminance and solar irradiance for tropical climate, characterization of tropical luminance and radiance distributions and an application of automated venetian blind for daylighting.
• Assessment of tropical daylight illuminance and solar irradiance.
Availability of tropical daylight and solar irradiance were assessed from measurement records at a station at Asian Institute of Technology (AIT) during 1999-2004. The mean hourly values of illuminance and irradiance and its cumulative frequency distribution are presented for 12 calendar months. The standard deviation of the data is also presented. The results demonstrate that tropical sky is luminous and daylight is high throughout the year. Diffuse illuminance value is also high due to the presence of clouds in the sky almost the time. These lend further credence to earlier expectation of high potential for daylighting in the tropics. Daylight illuminance and irradiance on four cardinal orientations were investigated. Variations of vertical illuminance and irradiance are dependent strongly on conditions of the sky and relative position of the sun with respect to the orientation of a plane. The functional form of Perez's model was selected for modeling of vertical illuminance and irradiance for tropical climate. A set of local coefficients of the Perez's model were derived. Performance evaluation was carried out for the localized models in conjunction with other existing models. The results illustrate that Perez's models using local coefficients give more accurate results than that using the original coefficients proposed by Perez and outperform al I other models. The results illustrate a need to distinguish the case when the sun is in front of a plane and when it is behind the plane. Atmospheric turbidity of tropical sky was also studied. The turbidity indices, namely, Linke factor, Angstrom coefficient, and illuminance turbidity factor were derived from the records of the AIT daylight station. The mean values and frequency of occurrence of each index have been used to characterize the atmospheric turbidity of the sky. Values of the turbidity of the atmosphere are found to vary with seasons. Atmospheric turbidity is relatively low and quite stable during dryer months from November to January and increasing in wet season from March to August. From the studies a tropical daylight database was created, illuminance and irradiance models were developed for the tropics.
• Characterization of tropical sky luminance and radiance distributions.
Eight published distribution models were first evaluated against the distribution data measured in the tropics. The results show that Harrison's, Matsuura's and Perez's models seem to perform well under different sky conditions. However, ASRC-CIE model performs relatively welI under all sky conditions. Most models do not perform well in the circumsolar region, irrespective of sky condition.
To characterize tropical luminance distribution, a set of standard sky luminance distribution (SSLD) was employed. It is found that the luminance of solar radiation from north Bangkok falls mainly under clear and intermediate sky types of the standard distribution classification. The turbid clear sky and clear sky occur more often during the dryer and cooler months of November, December, and January. In the midst of the rainy season, the sky falls into the intermediate category for over 40% of the time. Luminance and radiance distribution models were next developed for tropical sky. The model comprises two independent functions of gradation function and indicatrix function. Five parameters a-e of the model are used to account for patterns of luminance distribution over the sky. A search technique evolutionary programming was used to find suitable values of the model parameters for whole ranges of sky condition and of solar altitude angle. Two insolation parameters luminous clearness index and a ratio of zenith luminance to diffuse horizontal illuminance were modified first to improve its performance and then used to correlate to the model parameters. This enables the use of basic quantities of solar radiation measured at a meteorological station to determine luminance distribution. Performance of the developed models was evaluated. The results show that the developed model can predict well both the luminance distributions for tropical sky. The luminance model developed would facilitate calculation of interior daylight illuminance from sky. The model also helps in evaluation of applicability of a considered daylighting technology for tropical climate.
• Application of automated venetian blind for daylighting in the tropics.
An experiment of an automated blind system was conducted at a full-scale outdoor laboratory in Energy Park, Asian Institute of Technology (AIT) to investigate its application in tropical region. Many operation schemes of the blind system were set and experimented to evaluate resultant quantity and quality of indoor daylight. Quality of daylight is evaluated by excessive glare using daylight glare index (DGI). For a normal wok space, value of DGI is commonly limited to 22. The experimental results show that the automated blind system linked with a dimmable lighting system can provide sufficient work plane illuminance (500 lux) with an accepted uniformity of light distribution at the same time a good visual environment (DGI<22) through the year. The application of automated blind system can solve or at least alleviate limitations of the use of daylight through side window. Fluctuation of interior illuminance due to large variability from the exterior during cause of day is reduced by altering of blind slats. The automated blind system is applicable for all sky conditions in tropical climate. An algorithm was also introduced for calculation of interior daylight illuminance and associated glare from the blind-window system. Based on the algorithm, a computer program was written to simulate the operation of the blind system under tropical daylight climate. Using the distribution model developed earlier and the illuminance data from the AIT daylight station, the developed program can calculate interior daylight illuminance accurately. The program was employed to simulate the operation of the automated blind system when used for an office space. The results show that energy could be saved from lighting system upto 80% for the whole year. |
| Year | 2007 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ET-07-03 |
| 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) | Kumar, Sivanappan;Surapong Chirarattananon; |
| Examination Committee(s) | Honda, Kiyoshi ;Nadarajah, Mithulananthan ;DiLaura, David L. ; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2007 |