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• Thermal performance of the radiant ceiling cooling was assessed for intermittent operation in tropical office environment. • Insulated envelope and outdoor air heat recovery improved both indoor comfort and energy saving of the radiant ceiling system. • The local people would achieve their neutral sensation by the radiant ceiling cooling for more than 95% of the office hours. • The radiant system saved the electrical energy up to 40% opposed to the conventional mixed-air system. This paper investigated the radiant ceiling cooling in office buildings in a tropical hot humid climate. Full-scale experiments were conducted in an outdoor laboratory chamber to observe the indoor thermal conditions and the envelope heat gain from the intermittent operation of the installed radiant chilled panels (RCP) coupled with an outdoor air unit (OAU). The radiant system was also modeled by using a simulation software namely Transient System Simulation Software (TRNSYS), and the calculation results from the model were compared to the experimental observations. In the simulation part, the validated TRNSYS model was adopted to assess the radiant system performance in a typical office environment under the four schemes of combinations of the technology options for the OAU and the building envelope. The perceived comfort from the radiant cooling was assessed based on the thermal sensation of the local subjects acclimatized to hot humid climate. The energy consumption of the radiant cooling was also apprised as opposed to the conventional mixed-air system. The simulation results presented an insight into the importance of the exhaust air heat recovery and the envelope insulation on energy saving and human comfort improvement for the radiant cooling. [ABSTRACT FROM AUTHOR]

An automated blind can provide energy saving and better comfort. To obtain these benefits a computer program that is able to calculate interior illuminance, heat gain, glare discomfort and thermal comfort has been developed. The thermal performance of the window system was investigated. From the study it is found that installing a venetian blind in between the double-pane glass window causes a significant reduction in heat gain compared to the plain glass window. The heat gain through the window system in the shortwave part of the radiation is analyzed. The slat reflectance, slat angle and solar profile angle are the major affect on the shortwave part of solar heat gain coefficient. The blind using a lower value of slat reflectance has a lower shortwave part of solar heat gain coefficient. The effective solar heat gain coefficient (SHGC) and the effective overall heat transfer coefficient (U) for the double-pane glassed window with enclosed horizontal slats was developed. These SHGC and U value can be used with the equation to calculate the Overall Thermal Transfer Value (OTTV) of Thailand's building energy code to evaluate a building that use the double-pane glassed window with enclosed venetian blind. [ABSTRACT FROM AUTHOR]

Abstract: This paper adopts a concept of life cycle cost (LCC) to develop a scheme suitable to rate the energy performance of air-conditioning systems for Thailand. The developed scheme arranges the performance into three levels: good, very good, and excellent by which the excellent corresponds to that that provides the minimum system life cycle cost. The lowest performance level of the scheme is assigned corresponding to the minimum performance requirements of air-conditioning systems announced in Thailand''s building energy code (BEC). In this study, the capital cost of air-conditioning equipment was obtained from the main manufacturers and distributors in the country. The operating cost was derived from the annual electrical energy consumption of the system simulated using a well-established software named “DesignBuilder”. The analysis results show that in most cases the best performance of chillers available in the market offers the minimum life cycle cost. [Copyright &y& Elsevier]

The International Commission on Illumination has adopted a set of fifteen standard sky luminance distributions (SSLD). One of our previous papers uses a least squares method to sort sky luminance measurements from a station located north of Bangkok into fifteen slots, each corresponding to each type of SSLD, to appraise the statistics of occurrence of each sky type at the location. The paper also uses Kittler's method (Kittler; and others, 1997) to prepare paired values from the measurements sorted and obtains parameter values of the gradation function and those of the indicatrix function separately from measurements in each slot. This paper applies evolutionary computation to obtain a set of parameter values for both gradation function and indcatrix function simultaneously under least squares criterion. This method enables all measurements in each slot to be used. The resulting luminance distribution function thus obtained for each sky type possesses lower bias error and lower mean square error than those of the corresponding type of SSLD when both are evaluated against measurements [ABSTRACT FROM AUTHOR]

An investigation of atmospheric turbidity has been undertaken for tropical Thai sky. Values of turbidity indices, namely, Linke factor (TL), Angstrom coefficient (β) and illuminance turbidity factor (Til) are derived directly from measurements taken by pyrheliometer, Volz sunphotometer and beam illuminance meter. Monthly mean values and frequency of occurrence of the value of each turbidity index are used to characterize variations of atmospheric turbidity. Simple polynomial equations are developed for computing values of Linke factor and illuminance turbidity factor as functions of solar altitude angle. Using the values of Linke factor and illuminance turbidity factor obtained from the models developed, values of beam normal irradiance and illuminance can be calculated accurately under clear sky conditions. Values of daylight illuminance are useful for daylighting application that contributes to energy conservation for buildings. Knowledge of the size of beam normal irradiance is useful for calculation of cooling load in air-conditioning buildings in tropical climate. [Copyright &y& Elsevier]

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%. [ABSTRACT FROM AUTHOR]

Abstract: Vernacular residential houses in Thailand were not heated nor cooled. The walls of such houses were constructed from wood and other light natural materials. Air-conditioning to cool interior spaces is now common and brick and concrete has replaced natural materials for walling. Even when a house is designed for air-conditioning, no insulation is used on the enclosing walls. It is generally believed that thick and heavy walls reduces cooling load in a space but insulation may not and is too costly. This paper presents results from an experimental and simulation study on comparative thermal performance of walls enclosing spaces that are used to serve three residential functions of bedroom, living room, and studio room. The study considers different levels of insulation and its placement at the interior and exterior surfaces on walls with and without windows, and for each functional use of a space. Use of external shading and blinds or curtain is not considered in this study. In all cases, the study concludes that insulation placed at interior wall surface improves wall thermal performance and is superior to that of exterior placement. The latter part appears to contrast with what have been found in similar studies taken under cool climate. [Copyright &y& Elsevier]