• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.1-8
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• 2015

Thermoelectric (TE) technology is becoming increasingly important in applications of solid-state cooling and renewable energy sources. $Bi_2Te_3$-based TE materials are widely used in small-scale cooling and temperature control applications; however, higher levels of TE performance are required for new applications such as large-scale cooling (e.g., domestic refrigerators or air conditioners) and for highly efficient power generation system. Recently, the TE performance of $Bi_2Te_3$-based materials has been remarkably enhanced by the introduction of nanostructuring technologies which can be used to prepare TE raw materials. Because it takes into account the theoretical and experimental characteristics, nanostructuring has been shown to be one of the most promising ways to realize the simultaneous control of the electronic and thermal transport properties. In this review, emphasis is placed on bulk-type nanostructured $Bi_2Te_3$-based TE materials. Nanostructuring technologies for enhanced TE performance are summarized, and a few important strategies are presented.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.415-418
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• 2006

In Japan, research and development were undertaken on gas hydrate-side industrial processes associated with power generation system connections that may particularly be necessary to develop gas hydrated technology-based industrial systems. In so doing, data and engineering technologies useful n formulating guidelines on design of practical process were accumulated. In addition, basic research into theoretical evidence were carried out to promote and support the development of technological elements for those processes. In basic research designed to promote and support the research and development of elemental technologies microanalyses were conducted to understand the decomposition mechanism of mixed gas hydrate. Moreover, measurement technologies that can be applied in industrial processes, such as numerical analyses and concentration ion measurement, were examined. Japan has developed a highly efficient gas hydrate formation process using micro-bubbles with a tubular reactor. Higher formation rate over conventional systems has been obtained by the process. As mentioned above, the technical problems were clarified and the economics were studied from a view point of the NGH technology in this study. The results can be applied for utilization and must contribute to popularization of gas hydrate production.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.170-170
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• 2010

The energy conversion from the temperature difference between hot and cold source like ocean thermal energy conversion (OTEC), requires a long and large-diameter pipe (about 1000 to 10,000 meters long) to reach the deep water. The pipe diameter ranges from 2.8 meter for proposed early test systems, to 5 meter for large, commercial power generation systems. The pipe must be designed to resist collapsing pressures produced by water temperature and density differences, and the reduced pressure required to induce flow up the pipe. Other design considerations include the external-drag effect on the pipe due to ocean currents, and the wave-induced motions of the platform to which the pipe is attached. Various approaches to the pipe construction have been proposed, including aluminum, steel, concrete, and fiberglass. More recently, a flexible pipe construction involving the use of fiberglass reinforced plastic has been proposed. This report presents the results of a scaled fixed cold water pipe (CWP) model test program performed by EES(Engineering Equation Solver) to demonstrate the feasibility of this pipe approach.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.98.2-98.2
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• 2011

For optimal performance of a proton exchange membrane fuel cell (PEMFC), the membrane electrode assembly (MEA) requires hydration, and the membrane's conductivity depends on water content. A humidifier is required to ensure that the reactant gas, usually hydrogen and air, is hydrated before entering the fuel cell. Dry membrane operation or improper hydration causes performance degradation. Typically, the humidification of a fuel cell is carried out by means of an internal or external humidifier. A membrane humidifier is applied to the external humidification of transportation or residential power generation fuel cell due to its convenience and high performance. In this study, The experiments were constructed with a plate-type membrane humidifier in terms of geometric parameters and operating parameters. The results show that the temperature and pressure, the channel length, the membrane thickness and gas flow rate are critical parameters affecting the performance of the humidifier.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.668-671
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• 2007

A numerical study was conducted on a simplified model of a high-temperature solar receiver which incorporates liquid-metal heat pipe. The objective of this paper is to compare the isothermal characteristics of the heat pipe receiver with the conventional receiver utilizing convection of molten salt as heat carrier. The solar receiver was assumed to be subject to a concentration ratio between 50 and 1,000 to supply high-temperature heat to a stirling engine for electric power generation. For simplicity of the analysis, a cylindrical geometry was assumed and typical dimensions were used based on available literature. The heat pipe had a shape of double-walled cavity and the working fluid was a sodium. The analysis was performed assuming that the radiation heat flux on the inner walls of the receiver was uniform, since the focus of this study was laid on the comparison of the conventional type and heat pipe type receiver. The results showed that the heat pipe type exhibited superior performance when the operating temperature becomes higher. In addition, to explore the advantage of the heat pipe receiver, the channel shape and dimensions should be adjusted to increase the heat transfer area between the wall and the heat trnasfer medium.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.105-108
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• 2006

The fuel cell is one of the promising environment-friendly energy sources for the next generation. The fuel cell provides good energy efficiency above 40% without pollution or noise. Different fuel cell types are usually distinguished by the kind of electrolyte. Among these, the proton exchange membrane fuel cell (PEMFC) has advantages of high power density. low operating temperature, relatively quick start-up, and rapid response to varying loads. The bipolar plate is a major component of the PEM fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding with design of experiments (DOE) to evaluate moldability. The cost for compression molding of graphite-composite bipolar plate was compared with machining cost to make the same bipolar plate.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.247-250
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• 2008

Biomass gasification is a promising technology for producing a fuel gas which is useful for power generation systems. In biomass gasification processes, tar formation often causes some problems such as pipeline plugging. Thus, proper tar treatment is necessary. So far, nickel (Ni)-based catalysts have been intensively studied for the catalytic tar removal. However, the deactivation of Ni-based catalysts takes place because of coke deposition and sintering of Ni metal particles. To overcome these problems, we have been using ruthenium (Ru)-based catalyst for tar removal. It is reported by Okada et al., that a Ru/$Al_2O_3$ catalyst is very effective for preventing the carbon deposition during the steam reforming of hydrocarbons. Also, this catalyst is more active than the Ni-based catalyst at a low steam to carbon ratio (S/C). Benzene was used for the tar model compound because it is the main constituent of biomass tar and also because it represents a stable aromatic structure apparent in tar formed in biomass gasification processes. The steam reforming process transforms hydrocarbons into gaseous mixtures constituted of carbon dioxide ($CO_2$), carbon monoxide (CO), methane ($CH_4$) and hydrogen ($H_2$).

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.841-847
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• 2018

Since global energy consumption and demand for energy have dramatically risen, a focus on environmental problems and sustainability has become more important. Clean and renewable energy sources such as offshore wind power generation have received attention among new renewable energy options as alternative energy resources. Due to maintenance and operational perspectives, offshore wind farms have been planned for installation in many coastal waters. However, development of offshore wind farms faces interference from existing maritime traffic along the planned areas. In order to safely and effectively govern marine traffic in the vicinity of wind farms and inner areas, standard criteria are suggested to allow vessels to sail the internal waters of offshore wind farm areas. Therefore, the purpose of this study is to establish allowable criteria for sailing vessels and safety zones for offshore wind farms by investigating the local regulations of various offshore wind farm cases overseas. The commended inner safety zone of wind farms is proposed to be a distance of 150 % of the rotation diameter of the wind turbine rotor and a distance of 200 m from the outer wind turbine for the outer safety zone. Besides this, the allowable criteria for sailing vessels within a wind farm is proposed to have an air draft of 14.47 m south-west wind farm sea areas for a minimum margin to avoid hull contact through evaluation of the tide and height of a wind turbine. further studies will be needed to establish vessel sailing criteria among adjacent offshore wind farms as well as vessel sailing criteria within a single offshore wind farm.

• Journal of Korean Society of Disaster and Security
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• v.7 no.1
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• pp.27-33
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• 2014

This research has been shown the strategic disaster prevention and safety management's methodology that minimize the demage and loss from environmental disaster: it is made the renewable energy using the urban wastes causing the main environmental disaster, it minimize the generating cost from the environmental disaster, it gain the energy source for preparing the large-scale shutdown electricity, it gain the profit from the continuous electric power and heat energy's generating, it gain the renewal energy source from the old urban wastes' landfill, it give back the citizen the clean environment, the construction cost is able to be solved form the profit which the power plant is made the plasma gasification generation of the urban wastes, it create the new related jobs in the local government, it base to be invested the local industrial zone's commercialization due to the renewal energy power plant. Especially, in happen to the large-scale natural disaster's typhoon and earthquake, in the result generating the large-scale urban wastes, it is shown the prepared and robust model which contribute the preventing recovery of the local economy using the renewal energy of the urban wastes, and the strategic disaster prevention and safety management's method in the future city.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.4
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• pp.73-84
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• 2015

Electricity generation using fossil fuels has caused environmental pollution. To solve this problem, research on new renewable energy sources (solar, wind power, geothermal heat, etc.) to replace fossil fuels is ongoing. These devices are able to generate power consistently. However, they have many weaknesses, such as high installation costs and limits to possible setup environments. Therefore, an active study on piezoelectric harvesting technology that is able to surmount the limitations of existing energy technologies is underway. Piezoelectric harvesting technology uses the piezoelectric effect, which occurs in crystals that generate voltage when stress is applied. Therefore, it has advantages, such as a wider installation base and lower technological costs. In this study, a piezoelectric harvesting device imitating seaweed, which has a consistent motion caused by fluid, is used. Thus, it can regenerate electricity at sea or on a bridge pillar, which has a constant turbulent flow. The components of the device include circuitry, springs, an electric generator, and balancing and buoyancy elements. Additionally, multiphysics analysis coupled with fluid, structure, and piezoelectric elements is conducted using COMSOL Multiphysics to evaluate performance. Through this program, displacement and electric power were analyzed, and the actual performance was confirmed by the experiment.