Surapong Chirarattananon

Daylight availability and models for global and diffuse horizontal illuminance and irradiance for Bangkok

We present results of a study on measurement of illuminance of daylight and solar irradiance from a station in the Asian Institute of Technology (AIT) campus, which is situated in a tropical region. Availability of daylight illuminance and solar irradiance on the horizontal and on vertical planes in cardinal directions is first presented. Mathematical models of global and horizontal daylight illuminance and solar irradiance are then presented. Our results reinforce earlier expectation of good potential for daylighting in tropical climate.

Experiments in a solar simulator on solid desiccant regeneration and air dehumidification for air conditioning in a tropical humid climate

This paper presents an indoor and analytical study to evaluate the performance of a desiccant cooling system that uses silica gel as desiccant, electric light bulbs to simulate solar radiation, and forced flow of air through an IDC (integrated Desiccant/Collector). In the regeneration process, the rate at which water is removed from the desiccant increases with irradiation and decreases with air flowrate. In the air dehumidification process, the adsorption rate decreases with irradiation and increases slightly with flowrate. Comparisons between analytical calculations and experimental data show good agreement, and the calculations show that it should be possible to operate this system in tropical humid climates using the regeneration process in the day and the air dehumidification in the night time.

A technical review of energy conservation programs for commercial and government buildings in Thailand

Abstract This paper examines the requirements for designated buildings and the mechanisms for implementation of energy conservation programs in accordance with the Energy Conservation Promotion Act of Thailand. It then reviews the details of energy audits and implementation of energy conservation of designated commercial buildings and small government buildings. Through use of the DOE-2 simulation program and reference building models developed from energy audit information, it is shown that whole building retrofit is more cost effective than adopting individual options. It also points out that mobilizing involvement of the occupants of a building is a necessary and integral part of a successful energy conservation program. The paper also suggests means to overcome the present impediments to successful implementation of the programs.

Daylighting through light pipes in the tropics

Daylighting possesses good potential for application in the tropics, where the sky is luminous. But the depth of penetration of skylight through side windows is limited and can be complemented by sunlighting for illumination of the deeper interior space of a building through light pipes in the ceiling plenum. Modeling of the mechanisms of light delivery and heat transfer will enable trading off between light gain, increased air-conditioning load, and overall system performance and cost. This paper reports the development of such a model based on a general configuration of a plenum in a test room and a comparison of the calculation results with results from physical measurements.

Daylighting Potential in Thailand

Daylighting has good potential for application in tropical climates. It can help save electric energy as well as reduce the daytime power demand substantially. It can bring another dimension of energy efficiency in addition to efficient lighting technology, as well as aesthetic value. Its integration with continuous-dimming electric lighting is found to be acceptable. However, fundamental research as well as daylighting application technology are required to realize the potential.

An experimental study of a facade mounted light pipe

An experimental study of a rectangular light pipe mounted on a façade is reported. We used static and adjustable reflectors for enhancing capture and transmission of sunlight through the light pipe. A ray tracing technique was used to calculate the direct sunlight reflected into the light pipe and its transmission to the end of the light pipe. An inter-reflection method was used to calculate the transmission of diffuse skylight and the resulting daylight illuminance in the building interior. The experimental and calculation results demonstrate that daylighting through light pipes can provide acceptable illuminances in deep spaces for almost the whole day under conditions of clear and partly cloudy skies.

Energy-efficient lighting in Thai commercial buildings

We explore the opportunities to reduce the electricity required for lighting in prototypical Thai offices, hotels, and shopping centers. Using a whole-building energy analysis approach, we calculate the savings from lighting conservation measures directly, and from associated reductions in cooling load. Ancillary cost savings of air-conditioning energy and capacity comprise a significant 30 to 50% of the total. Lighting technologies considered in this study include electronic ballasts; tri-phosphor, narrow-diameter lamps; specular reflectors; occupancy sensors; lumen maintenance and daylighting controls; and compact fluorescent lamps. From a societal economic perspective, the cost of conserved energy of employing all applicable lighting conservation measures to these buildings is one-quarter or less than the average retail price of electricity for commercial customers, with a payback time of less than one year in hotels and retail buildings and approximately three years in offices. The internal rate of return for installing all lighting measures is 35% in offices, 142% for hotels, and 107% for shopping centers. Several current policy initiatives in Thailand, including a proposed energy standard for commercial buildings, with specific provisions for lighting, and plans by the nations electric utility to develop two commercial sector conservation programs, should help to spur the adoption of more efficient lighting products. We strongly recommend that the currently high tariffs and taxes (50% and greater) for imported efficient lighting products be reduced.

Evaluation of Sky Luminance and Radiance Models Using Data of North Bangkok

Abstract The tropical sky is highly luminous. This gives rise to expectation of its high potential for daylighting. The availability of an accurate luminance distribution for daylight from the sky would help advance the movement for daylighting. On the other hand, accurate radiance distribution model is also needed to help manage the undesirable heat gain due to solar radiation penetration in air-conditioned buildings. Towards these ends, eight luminance and radiance distribution models were evaluated against luminance and radiance measurements recorded in a station located north of Bangkok. Due to prevalence of intermediate and cloudy sky conditions in the tropical region, attention was paid to seeking models that could perform well under these conditions. It turns out that a number of models are acceptable, but no single model performs distinctively well for the prevalent conditions.

Challenges of daylighting with the luminosity and variability of the tropical sky

Sky luminance and illuminance measurements from the daylight measurement station at the Asian Institute of Technology, Pathumthani, Thailand show that there is usable daylight throughout office hours on every day of the year. The variability of daylight, however, poses a challenge when attempting to characterize the sky and to develop models of daylight availability. Calculation of interior daylight and heat gain, and integration of electric lighting with daylighting are also a challenge. The disadvantages of glare and heat gain can overwhelm the benefits of daylighting in air-conditioned buildings if care is not taken. These problems are associated with clear and intermediate skies, and the combined frequency of occurrence of these conditions is 60%.

Daylighting for energy conservation in the tropics: The Lumen method and the OTTV

We describe a potential use of the Lumen Method for daylighting applications in commercial buildings in a tropical climate. Calculations of the overall thermal-transfer value show that daylighting and judicious choice of the composition of the building envelope optimize lighting and minimize air-conditioning loads in buildings.