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Year 2010

Volume 1, Issue 3 July - September 2010

Abstract: This paper presents the results of modeling and simulating the transmission of beams of sunlight and diffuse skylight, separately and together, through circular light pipes with and without bends. A well-known theoretical model of the transmission of light rays through straight cylindrical light pipes was introduced by Zastrow and Wittwer in 1986 and re-examined by Swift and Smith in 1995. The present authors propose an alternative approach that differs both in terms of the procedure for the calculation of the transmission of daylight components, and in the manner with which locally measured daylight illuminance data are utilized. The authors apply raytracing principles to trace an individual ray from the entry to the exit of a pipe. Torus sections are used to model bends in cylindrical light pipes. The present method is theoretical but lends itself to practical application and can be used for the design of a particular pipe. The paper illustrates the generation of sky luminance data from locally measured diffuse horizontal daylight illuminance data using a well-known sky luminance model, and the transmission of diffuse skylight and beam sunlight though straight pipes and pipes with bends. The computational procedure was coded into a computer program. The program was used to generate some interesting results that include results from the simulation of the transmission of daylight through straight pipes and pipes with bends.

Keywords: daylighting, light pipe, sunlighting, ray tracing, skylighting.
(632 K)
Abstract: In this study, crude Jatropha curcas oil was used as feedstock for biodiesel production by alkali-catalyzed methanolysis. The reaction in the presence of NaOH as catalyst was carried out to investigate the optimum conditions and to study the effects of variables on the reaction. These variables included methanol-to-oil molar ratios of 4:1-10:1, catalyst concentrations of 0.25-2.0% w/w of oil, reaction temperatures of 32-60ºC, and reaction times of 5-40 minutes. The methyl ester content in the product was analyzed by gas chromatography (GC). The optimum conditions for Jatropha curcas biodiesel production were a methanol-to-oil molar ratio of 6:1, a catalyst concentration of 1.0% w/w of oil, a reaction temperature of 60°C, and a reaction time of 40 minutes. The methyl ester content under these optimum conditions was 98.6% w/w, and all of the measured properties of the Jatropha curcas biodiesel met the Thai biodiesel (B100) specifications and international standards EN 14214:2008 (E) and ASTM D 6751-07b, with the exception of lower oxidation stability. The results reveal that all of the reaction variables in this study had positive effects on the reaction.

Keywords:
Biodiesel · Jatropha curcas oil · Methanolysis · Methyl ester.
(128 K)
Abstract: In 2006, the industrial sector became the biggest electricity consumer in Indonesia, followed by the household sector. The industrial sector consumed approximately 43% of total electricity followed by the household sector with 35%. By using the Long-range Energy Alternatives Planning system (LEAP) model for electricity projection from 2006 to 2025 for the Java-Madura-Bali (Jamali) islands, it was found that the household sector would become the biggest consumer by 2025, consuming about 42%. This study applied the demand side management (DSM) options to reduce electricity demand in the household sector by implementing lighting efficiency improvements namely: (1) replacing 40W incandescent lamps with 8W compact fluorescent lamps (CFL), (2) replacing 60W incandescent lamps with 12W CFL and (3) replacing 100W incandescent lamp with 20W CFL. With lighting efficiency improvements, the electricity demand would be reduced by 5.2% in 2025. For electricity generation capacity, it would reduce the electricity generation capacity by 3.2 GW or 5% of total generation capacity of the Business as Usual (BAU) scenario in 2025 and also reduce emissions by about 15.4 million tonnes of CO2 equivalent, accounting for a reduction of 5.8% compared to the BAU scenario. The DSM costs are analyzed in order to achieve electricity demand reduction target. In addition, the externality costs avoided by DSM application are also calculated to find a reasonable incentive for it.

Keywords: The household sector, demand side management, electricity demand reduction, LEAP model, emission reduction.
(102 K)
Abstract: Biochemical conversion of lignocellulosic biomass to ethanol provides a sustainable energy production system. Bamboo is a fast growing woody grass that has great potential to be used as a domestic feedstock for fuel ethanol production. It consists of about 40% cellulose, and 27% hemicelluloses. In this investigation, bamboo (Dendrocalamus asper) was pretreated with dilute sulfuric acid prior to enzymatic hydrolysis process to produce fermentable sugars. The amount of dry feedstock solid/liquid loading at 10% w/w was pretreated in an autoclave at different temperatures (120, 140°C) with different residence times (30, 60, 90 min) and different sulfuric acid concentrations (0.6, 0.9, 1.2% w/w). Maximum glucose and xylose yields were achieved at 140°C, 1.2% sulfuric acid concentration and 90 min. After enzymatic saccharification with cellulase and β-glucosidase at the same pretreatment conditions, the yields of total reducing sugars were found to be low (56 mg/g). On the other hand, the maximum yields of total reducing sugar (85 mg/g) were obtained for the pretreatment conditions at 120°C, 1.2% sulfuric acid concentration and 60 min. Within these conditions, increasing temperature, residence time and acid concentration led to higher total sugar yields and cellulose conversion rates.

Keywords: Bamboo; Hydrolysis; Lignocellulosic materials; Pretreatment; Reducing sugars
(139 K)
Abstract: 91% of electricity generated in Thailand is mainly by Centralized Generation (CG) [1]. Moreover the recent power development plan [2] relies mostly on Centralized Generation (CG) including centralized fossil fuel plants, large hydropower and nuclear power plants. While the existing potential of Decentralized Generation (CG) such as on site generation CHP plants and renewable energy resources, until now have not been fully utilized. In order to present the significant benefits that DG can contribute, if they are fully utilized, this paper determines primary energy saving, economical and environmental values that can be benefited from DG with the most appropriate generation shares based on its potential. In this study, WADE economic model has been applied for the analysis to calculate the generation share in the next 20 years based on 4.95% of electricity demand growth. With the penetration of DG in the system regarding its potential and existing power development plan of Thailand, DG share will increase from 2% (1,759 MW) to 17% (12,282 MW) by the year 2026. This decentralized system results in significant savings on primary energy 84.3 TWh/year (11%), emissions reduction (NOx, SO2, PM10, CO2) 40 Mton (17%), capital cost savings US$ 1.42 billion (3%), and mostly in a reduction of required additional capacity of around 4,955 MW (6%).

Keyword: Decentralized Generation, Potential, Primary Energy Saving, Emissions Reduction, Thailand.
(216 K)
Abstract: The objective of this research is to quantify the water content on the cathode side in various PEM fuel cell operations. It
can be revealed by direct visualization in an operational transparent single-serpentine PEM fuel cell. Images of liquid water
accumulated inside the cathode flow channel were recorded by a digital camera to study water flooding in PEM fuel cell. The water
coverage area in the cathode flow channel was estimated by an image processing technique. The effects of oxygen flow rate, cell
temperature and time development on the water flooding were studied. The results indicated that excessive low or high cell
temperature caused water to flood into the PEM fuel cell. The increasing of oxygen flow rate can remove more liquid water out of the
cathode flow channel. However, too high oxygen flow rate caused the insufficient water content to maintain the membrane in the
hydrated state and the dramatic decrease of fuel cell’s performance. The water flooding did not appear in a single-serpentine cathode
flow channel when a transparent PEM fuel cell has operated within 40 minutes.

Keywords: PEM fuel cell; water management; direct visualization; transparent single-serpentine, image processing.
(736 K)
Abstracts: By conducting a survey of energy demand in rural industries of the Mekong Delta in Vietnam, this study aimed to: (i)
estimate current and future energy demands of rural industries; (ii) identify the most available biomass source for energy production;
and (iii) develop and assess biomass utilization scenarios with different system scales and conversion technologies. The results
showed that rice husk and straw are the most available biomass sources for energy production in the Mekong Delta. Depending on
the type of technology and the scale of the system, electricity produced from such biomass sources could be used to satisfy demands
within the community, and the excess energy produced could be sold to the national grid. A set of indicators, including the specific
cost and greenhouse gas (GHG) emissions of usable energy, total GHG emissions, and GHG marginal abatement cost were used to
assess the economic and environmental benefits of several biomass utilization scenarios. All the scenarios in which grid-based
electricity was replaced by biomass-based electricity have lower specific usable energy costs and GHG emissions, resulting in
negative values of the marginal GHG abatement cost. Among the scenarios we considered, medium-scale systems offer better
economic and environmental benefits than small-scale systems. Gasification-based systems have a lower environmental impact but a
higher cost for usable energy than steam turbine systems.

Key Words: biomass, material flow, conversion technology, rural industry, Mekong Delta.
(398 K)

 

ISSN: 1906-4918
Frequency: Quartery
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