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This paper investigated the artificial neural network (ANN) modeling to forecast the one-hour ahead global and diffuse solar radiation using the observed data during 2019-2021 at a meteorological station in Bangkok, Thailand. Results from the statistical analysis portrayed the abundance of the tropical solar radiation and its large variation all year round. As a step to move advance the renewable energy use of the solar radiation at the location, the ANN forecasting models were proposed for all climatic conditions. The model input were the ambient temperature, solar elevation, and an insolation parameter namely normalized global solar radiation. The model performance was assessed by using the two statistic parameters: normalized mean bias error (nMBE), and normalized root mean square error (nRMSE). The results showed that the ANN models could forecast the global radiation with the nMBE of 1.79% and nRMSE of 26.20%. For the diffuse radiation forecast, the nMBE and nRMSE of the models were obtained at 7.78% and 36.21%, respectively. In order to demonstrate a benefit of the two developed ANN models, their forecasted horizontal data were employed to further predict the total solar radiation on vertical plane. Benchmarked with the smart persistence model, the developed ANN models possessed the higher forecasting accuracy for all weather conditions. [ABSTRACT FROM AUTHOR]

Urban settlements are home to the greatest levels of greenhouse gas emissions and energy consumption globally, with unprecedented rates of urban expansion occurring today. With the majority of global urbanization occurring along the periphery of urban areas in developing countries, investigation of 'green' building practices designed specifically for 'peri-urban' regions is critical for a low-emitting future society. This study assesses a state-of-the-art residence designed for a middle-class family of four residing in the peri-urban region of Bangkok, Thailand. The residence employs both demand-side management strategies and low-emitting energy supply technology to achieve energy-positive status. To elucidate the influence that key design decisions have on the life cycle sustainability of the home, several variants of the residence are modeled. A process-based life cycle assessment consistent with the International Organization for Standardization (ISO) 14044:2006 standard and following ReCiPe Midpoint life cycle impact assessment methodology is used to quantify the life cycle impacts per square meter of conditioned residence floor area for climate change (582 kilograms [kg] carbon dioxide equivalent), terrestrial acidification (4.01 kg sulfur dioxide equivalent), freshwater eutrophication (30.4 grams phosphorous equivalent), fossil depletion (362 kg iron equivalent), and metal depletion (186 kg oil equivalent) impacts. We model multiple scenarios in which varying proportions of Bangkok's peri-urban detached housing demand are fulfilled by the energy-positive residence variants. Under the best-case replacement scenario (i.e., 100% replacement of future peri-urban detached housing), significant reductions are achieved across the life cycle climate change (80%), terrestrial acidification (82%), and fossil depletion (81%) impact categories for the steel-framed, energy-positive residence. [ABSTRACT FROM AUTHOR]

• 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]

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]

Daylighting is perceived to be a potential measure for energy conservation in commercial buildings. In Thailand where the sky is highly luminous and daytime is long throughout the year, daylighting is however neglected by the use of heat reflective glasses to prevent excessive solar gain from windows. To address the issue, this paper investigates the energy performance of the daylighting from a window with horizontal slats located between two panes of glasses (slat window). The slats can shade the intense beam radiation, but allow penetration of the diffuse daylight for interior illumination. In the study, a model was developed to determine the thermal gain from the slat window. By using the thermal model together with the daylight model developed earlier, the simulations were performed and the results show that the slat window, when used with typical office room, can save 25–70% of the total electrical energy of air-conditioning and lighting in the same room equipped with heat reflective glass window. [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]

As renewable energy sources and net-zero energy homes become increasingly pervasive within the residential building industry, further reductions in consumption patterns will occur through demand side management (DSM). DSM can include measures such as energy-efficient system design, automated control and energy management systems, or policies and monitoring systems intended to alter user behavior. For an energy-efficient modern residence designed within a tropical context, several DSM strategies are considered for reductions in operational-phase energy consumption: a lightweight, thermally high-performing building envelope, installation of light dimmers to enhance user control of lighting, and comparison of a solar hot water system versus a point-of-use electric water heater to produce hot water for bathing demands. The energy-consumption savings associated with the three DSM strategies are simulated and normalized to an energy savings per cost of implementation basis in kWh per 1000 Thai Baht (THB) for comparison. The results show that financial investments in low-energy hot water heaters (i.e., solar water heating systems) result in relatively higher energy savings per unit financial investment than the other two strategies. Conversely, the installation of a lightweight, well-insulated envelope is highly expensive relative to its associated energy savings over a 25-year time frame. The savings associated with the insulated envelope, light dimmers, and hot water production strategies are evaluated at 80, 609 and 657 kWh/1000 THB investment, respectively. [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 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]

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]

Nanofilms of a polymer mixer of two ionomers, poly 3,4-ethylenedioxythiophene:poly(styrene sulfonic acid) (PEDOT:PSS), were used as conducting materials to develop transparent conducting electrodes. It was firstly found that convective deposition, a versatile and wide-area coating method, could be used for the coating and acid treatment of PEDOT:PSS films. Electrical conductivity of the PEDOT:PSS films was significantly enhanced up to 1814 S/cm by only one-time surface treatment by a mild acid solution (4 M methanesulfonic acid). This is because some PSS chains were removed out from the polymer mixer films without damage on the substrates. UV-vis-NIR spectroscopy, Raman spectroscopy, and cyclic voltammetry were used to characterize the acid-treated transparent conducting films. In this report, obtained transparent conducting PEDOT:PSS films on polyester substrates were used as flexible electrodes for fabrication of flexible electrochromic devices. Poly(3-hexylthiophene) (P3HT) was used as an active layer, which its color changed reversibly from transparent-light blue to purple with a small applied voltage (±3 V). [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]