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In this study, a method is used to develop a model for estimating luminance distributions of Thai’s sky. From the sky characterization, five out of the fifteen CIE standard skies are selected for the distribution estimation. This selection represents the minimum sky types that best fit to the distribution records of Bangkok (Thailand) and cover three sky conditions of clear, partly cloudy, and overcast. The developed model uses the five standard skies each to estimate prevailing luminance distributions within a particular range of insolation condition defined by lower and upper limit values of Perez’s clearness ( ε ) and sky brightness ( Δ ). In this scheme, a stochastic search technique of evolutionary computation was applied to optimize limit values for an accurate sky classification. Equations of optimal limit values were also formulated as part of the method. From the comparative evaluation with other sky models (i.e. Perez’s model, ASRC-CIE model, Harrison’s model, CIE-Si model, and Igawa’s all-sky model), the proposed model offers an alternative option for generating luminance distribution of Thai’s sky. [ABSTRACT FROM AUTHOR]

Ventilation is necessary for good indoor air quality (IAQ) in air-conditioned buildings. However, the ventilation causes a substantial load and resulting energy consumption of the air-conditioning system particularly for buildings in tropical region. To address the issue, this paper investigates the dedicated outdoor air system (DOAS) for the energy-efficient ventilation. In the study, performance of various DOAS configurations is evaluated for a typical office building under the hot and humid climate of Thailand. The results from the simulations using TRNSYS software show that the DOAS of the combination of a cooling coil, a run-around coil and an enthalpy wheel is the most energy efficient by which it offers the smallest total air-conditioning loads in obedience with the Thai's ventilation standard requirement. [ABSTRACT FROM AUTHOR]

The use of automatically controlled interior Venetian blinds can provide view and penetration of daylighting through window. In this study, an automatic system of vertical blinds affixed behind windows situated on north-west facades of a laboratory room were developed in order to investigate its daylighting performance. The system controls automatically the blind slats to shade out beam sunlight. Simulation using reference calculation algorithms and sky luminance distribution models and utilizing measured beam sunlight and diffuse daylight from the sky or skylight produces results that agree well with results from experiments. Moreover, using records of beam sunlight and diffuse skylight illuminance, simulation results show that the automated vertical blind and electric lighting system, when used in a room with the same configuration as that of the experimental room, can utilize daylight to save more than 24% of electric lighting energy in every month of the simulated year while maintaining illuminance at the workstation at the required level. [ABSTRACT FROM AUTHOR]

Radiant cooling is an alternative air-conditioning that have been implemented successfully in high latitude regions. In tropical region as Thailand, radiant cooling is quite challenge due to its cooling performance being limited by high-moisture ambient air. This paper reports an investigation of radiant cooling in a tropical building. The study comprises full-scale experiments of a radiant cooling system with cool panels installed in a room of a laboratory building. A separate fan coil unit was installed to remove humidity of the ventilation air before suppluying it into the room. A software namely TRNSYS was used to model the systems in order to determine the heat extraction rate of the cool panels. Thermal comfort level in the room was evaluated by predicted mean vote (PMV) index. The results show that the radiant cooling is able to use for air conditioning for human comfort in tropical buildings. However, a sophistical system to control temperature of the chilled water supplied to the cool panels and the fan coil unit for the ventilation air dehumidification is inevitably required. [ABSTRACT FROM AUTHOR]

Abstract: In the tropics, daylighting from a side window requires shading to intercept direct sunlight from the window whilst allowing penetration of daylight from sky. In this paper, daylighting from a double-pane glazed window with enclosed horizontal slats (slat window) was investigated for which it is situated on either north or south wall of a room. Full-scale experiments and simulations were conducted to characterize distribution of the interior daylight from the slat window under a real tropical climate. Performance of the slat window was evaluated in terms of the “useful daylight illuminance” (UDI), interior daylight availability and light power density (LPD) of an integrated dimmable lighting system. Empirical formulas were developed for determining annual average LPD values of the dimmable lighting system over its served area. The LPD value can be used with a reduced form of the energy equation of Thailand's building energy code to evaluate the reduced annual electrical energy consumption for accreditation of the daylight use in a building. The analysis of life cycle cost proved that the daylighting from the slat window integrated with the dimmable lighting system is cost effective. [Copyright &y& Elsevier]

Abstract: This paper reports results of a study on characteristics of luminous efficacies of tropical global and diffuse horizontal solar irradiances using observed data from a daylight measurement station located in the southern area of Bangkok, Thailand (latitude 13.58°N and longitude 100.44°E). Mean hourly values of the efficacies and their frequency distributions are first presented. Through scatter plots, variations of the efficacies are then presented for different sky conditions covering from cloudy to clear skies. From our results, the pattern of variation of tropical global efficacy is noticed to be distinct from those in high latitude region. In this study, two all-weather models are developed empirically for predicting values of the tropical global and diffuse efficacies. The models are evaluated for their performances against some selected existing models. The results show that the proposed models predict well the tropical efficacies and outperform all other evaluated models. [Copyright &y& Elsevier]

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]

Abstract: This paper reports an experimental and simulation study on application of automated Venetian blind for daylighting in tropical climate. A horizontal blind system operating automatically under programmed control was constructed and integrated onto the glazed windows to form a window system with an automated blind in a room of a laboratory building. A dimming controller was also integrated to the lighting system of the room. Different operation schemes of the window system were devised and tested in the attempt to maximize energy savings while maintaining the quality of the visual environment in the room. Intensive measurement of illuminance of the interior space was undertaken during the experiments. A methodology for calculation of interior daylight illuminance and associated glare corresponding to the configurations of the experiments was adopted. The method was coded into a computer program. Results of calculation from the program agree well with those from experiments for all the schemes of operation conducted. The program was used to simulate the situation when each scheme of operation was implemented for a whole year. It was found that such window system with automated blind enabled energy savings of 80%, but a more sophisticated scheme also helped maintain the interior visual quality at high level. [Copyright &y& Elsevier]

Abstract: In the tropics, the sky is luminous and variable. Distribution of luminance over the sky dome is non-uniform and varies widely and dynamically with weather condition. The high luminosity offers good potential for daylighting, but an understanding of the luminance distribution of tropical sky would help advance the movement for daylighting. This paper reports results of a characterization of sky luminance and radiance under the standard sky luminance patterns proposed by Kittler using measurements from a station located north of Bangkok. In accordance to the standard sky luminance classification, the sky patterns of north Bangkok mostly fall into clear and intermediate types. During cooler months, the sky is clear for over 60% of the time. In the midst of the rainy season, the sky falls into the intermediate category for over 40% of the time. The high incidence of clear sky on this classification differs from earlier results that use sky ratio and Perez''s clearness indices in the classification of sky condition. [Copyright &y& Elsevier]

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]