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Year 2010

Volume 1, Issue 4 October - December 2010

Abstract: This paper tries to evaluate the economic impact of mass transit systems, such as subways or railways. On evaluating four different urban areas (Bangkok, Hanoi, Jakarta, and Manila), the paper analyses the benefits and costs associated with urban mass transits and estimate their economic internal rate of returns (EIRRs). Through estimating the EIRRs, this paper addresses the potential economic benefits of urban mass transit systems, specifically energy security and environmental conservation.
The paper found that urban mass transit systems can, in general, produce substantial socio-economic benefits. The benefits come from savings on energy, CO2, time and passenger vehicle ownership. Also the simulation exercise revealed that cities with higher income may have bigger socio-economic benefits. Bangkok could enjoy the largest socio-economic benefits from expanding its urban mass transit network. Additionally, the analysis found that cities with higher population density may yield large socio-economic benefits. An outstanding example includes the case of Manila, which income level is nearly half of Bangkok, however, the city’s high population density will result in substantial socio-economic benefits through expanding its mass transit systems.
It should be noted that more than two decades is required to realize the potential socio-economic benefits from the urban mass transit systems. And this suggests that the early and timely implementation of a project could maximize the potential benefits. To facilitate early implementation, planning for mass transit systems should be an integral part of the city’s energy and environmental policy.

Keywords: Urban transport, mass transit, cost and benefit assessment, energy security, and sustainable development.
(178 K)
Abstract: The main objective of this paper is to investigate the acoustic and visual impacts on local residents of an existing 0.25 MW wind turbine generator (WTG) located in Huasai district, Nakhon Si Thammarat province, Thailand. Sound pressure level (SPL) was measured at various locations within 300 m around the WTG. A survey on general attitude towards the WTG of the residents living within a 2 km vicinity was also carried out among 351 respondents using a questionnaire. The results showed that while the ambient background noise was 38-44 dB(A), the SPL produced within 300 m around the WTG, operating at the rotational speed of 26-29 rpm, was 50-55 dB(A). Inside the tower at the heights of 12 m, 24 m and 36 m above the ground and inside the nacelle, the SPLs were 73 dB(A), 81 dB(A), 84 dB(A) and 91 dB(A), respectively, during the operation of the WTG and were 66 dB(A), 73 dB(A), 77 dB(A) and 78 dB(A), respectively, during the shutdown. The SPL produced as a result of the WTG was relatively low with respect to that generated from the other nearby sources such as the diesel engines of the pumping machines used in the shrimp farm. Public attitude
towards the acoustic and visual impact of the WTG was not negative. Furthermore, some respondents believed that installation of WTG farm should create jobs for the locals and the WTG farm could become a tourist attraction site.

Keywords:
Acoustic, Noise Annoyance, Public Attitude, Visual Impact, Wind Turbine Generator.
(449 K)
Abstract: The climate of Thailand is hot and humid and air-conditioning for thermal comfort is used in all tall buildings. Buildings with curtained walling are perceived to possess specific aesthetic value by many developers. As a consequence, such buildings cannot accommodate external shading device. In order to reduce transmission of solar radiation into such building, heat reflective glazing has been popularly used. Inadvertently, the building is subject to high cooling load from high heat gain through the curtained walling. However, as Thailand is located near the equator. For a northern or a southern façade, an exterior horizontal shading device can effectively shade radiation of the sun beam from a window below it while allowing skylight to enter the window to give a soft natural daylight in the room. The use of multiple-slat, sufficiently spaced horizontal shading device on the exterior of a facade on appropriately sized window will allow sufficient view out through the window, enables application of daylighting and reduces cooling load. This paper presents results of a study on the use of such shading device on windows under different combinations of glazing types, ratios of window area to wall area, and with un-insulated and insulated wall. When diffuse daylight from sky is used for daylighting, glazing that allows more daylight penetration is shown to offer a monetary worth of savings on electric lighting over its cost, and the cost of air-conditioning energy when the value of the ratio of window to wall ratio falls within certain range. The net benefit can be optimized at an appropriate ratio of window to wall area. When wall insulation is applied, the benefit is even enhanced at lower range of window to wall area.

Keywords: glazing performance, daylighting, window to wall ratio, wall insulation, multiple-slat shading device.
(222 K)
Abstract: The primary goal of this study is to analyze the mathematical model of Laser Induced Incandescence (LII) process applied to the measurement of diameter and temperature of a soot particle within flame. To simulate heating and cooling processes of a nanometer size particle, computer codes have been written to calculate the time dependent responses of the particle to laser pulse heating. The results include temperature, diameter, heat losses and LII-signal responses. At low laser fluence heating, the rate of heat losses from the particle is very low in comparison to the rate of heat gain by absorption and LII-signal being sensitive to the temperature of the particle. At high laser fluence heating, the particle sublimes and becomes smaller in diameter. The sublimation cooling is the most important form of heat loss for the particle and is at a comparable rate to the heat gain by absorption. The LII-signal is sensitive to both the temperature and diameter of the particle. Overall (or time integrated) heat transfer and LII-signal over the period of the laser pulse as a function of laser fluence has also been analyzed. The time integration of heat transfer modes over the duration of the laser pulse is represented in the form of an energy balance equation. It has been found that the absorption energy was, at the beginning, stored in the form of internal energy and later lost in the form of sublimation cooling as the laser energy fluence increased. At low laser fluence energy input, the magnitude of the time integrated LII-signal over the laser pulse duration increases with the laser fluence. At high laser fluence energy input, sublimation occurs and the diameter of the particle becomes smaller, undermining the LII-signal. These competing effects, between the internal stored energy gain against the sublimation energy lost, led to the threshold of the time integrated LII-signal at high laser fluence energy inputs. Once the threshold signal is reached, the overall LII-signal becomes less sensitive to the increasing of laser fluence.

Keywords: LII-process, soot diameter and temperature, heating and cooling of particle, energy budget
(505 K)
Abstract: This paper presents a practical methodology for quantifying the methane generation rate constant from four tropical sanitary landfills in Thailand. We used combination of static chamber and laser methane detection methods as well as geo-statistics to assess the total methane emission at each study site. After fitting of the estimated rate of methane emission per weight of waste deposited at the disposal sites with different age to the first order decay equation, it was found that the first order reaction rates were 0.33 yr-1. This high reaction rate as compared to previous studies in developed countries is probably due to the high moisture content of the waste in which food waste was the main component (>60%) combined with a tropical climate which has high precipitation and temperatures. These factors could stimulate anaerobic degradation and produce more biogas in a shorter time after the wastes has been disposed. In order to improve the estimation of methane emission from solid waste disposal sites in a tropical climate, this first order reaction rates can be considered as a country or region specific default value.

Keywords: methane generation rate constant, k value, landfill gas, greenhouse gas, first order decay.
(157 K)
Abstract: A micro-scale model of a Solid Oxide Fuel Cell (SOFC) involving electrochemical reactions and mass transport behaviors
throughout electrodes packed with nearly spherical-shaped particles was mathematically developed. The model was validated by
comparing the predicted results with already available experimental results. By minimizing the cell overpotential, the model provides
the optimal size of electrode particles corresponding to the specified porosities. The optimal volumetric ratio between ionic and
electronic conducting particles is also proposed. The study results substantiate the fact that SOFC overpotential could be effectively
decreased by increasing the operating temperature as well as operating pressure. The present study reveals the working mechanisms
of SOFC at the micro-scale level, while demonstrating the use of microstructure relations to enhance the SOFC performance.

Keywords: micro-scale model SOFC, microstructure; optimal size, overpotential, spherical-shaped particle.
(157 K)
Abstract: In this study energy consumption for canola production under irrigated and rain-fed conditions was investigated. Also energy and water indicators were analyzed to better understand the main effects of energy use in different production systems. For this purpose data were collected from 130 canola farms from Golestan province, the main center of oilseed production in Iran. The results revealed that, total energy input under irrigated and rain-fed conditions was 31809.9 and 15078.5 MJ ha-1, respectively. The main energy consumer inputs in irrigated conditions were electricity (45.3%), chemical fertilizers (28.3%) and diesel fuel (15.2%); also, about 85% of total energy input in rain-fed conditions was consumed by chemical fertilizers and diesel fuel inputs. Under irrigated and rain-fed conditions, the energy use efficiency was calculated as 1.85 and 3.5 and the energy intensity was found to be 13.54 and 7.13 MJ kg-1, respectively. Moreover, for irrigated conditions the water energy use efficiency and water productivity were calculated as 3.67 and 1.55 kg m-3, respectively. In order to reduce energy consumption and improve energy use efficiency and water productivity, it is suggested that canola production in the region shift to rain-fed conditions. Also, suitable design schemes for high irrigation efficiency and improving energy efficiency of water pumping systems are proposed to make the canola production more sustainable and to reduce its environmental impacts.

Keywords: Canola production; Energy input; Environmental impact; Irrigation; Water productivity.
(115 K)

ISSN: 1906-4918
Frequency: Quartery
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