• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.11-15
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• 2008

The composite membrane for direct methanol fuel cell (DMFC) was developed using $H_3O^+-{\beta}"-Al_2O_3$ powder and perfluorosulfonylfluroride copolymer (Nafion) resin. The perfluorosulfonylfluroride copolymer (Nafion) resin was mixed with $H_3O^+-{\beta}"-Al_2O_3$ powder and it was made to sheet form by hot pressing. The electrodes were prepared with 60 wt% PtRu/C and 60wt% Pt/C catalysts for anode and cathode, respectively. The morphology and the chemical composition of the composite membrane have been investigated by using SEM and EDXA, respectively. The composite membrane and $H_3O^+-{\beta}"-Al_2O_3$ were analyzed by using FT-IR and XRD. The methanol permeability of the composite membranes was also measured by gas chromatography (GC). The performance of the MEA containing the composite membrane (2wt% $H_3O^+-{\beta}"-Al_2O_3$) was higher than that of normal pure Nafion membrane at high operating temperature (e.g. $110^{\circ}C$), due to the homogenous distribution of $H_3O^+-{\beta}"-Al_2O_3$, which decreased the methanol permeability through the membrane and enhanced the water contents in the composite membrane.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.19-24
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• 2006

ZnO:Al(AZO) films prepared by rf magnetron sputtering on glass substrate and textured by post-deposition chemical etching were applied as front contact and back reflectors for ${\mu}c$-Si:H thin film solar cells. For the front transparent electrode contact, AZO films were prepared at various working pressures and substrate temperature and then were chemically etched in diluted HCl(1%). The front AZO films deposited at low working pressure(1 mTorr) and low temperature ($240^{\circ}C$) exhibited uniform and high transmittance ($\geq$80%) and excellent electrical properties. The solar cells were optimized in terms of optical and electrical properties to demonstrate a high short-circuit current.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.27-33
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• 2007

In this research, to develop the practical application system of fresh water generation system with plate-type fresh water generator using low pressure evaporation method is the main object, and to do that, this study used the evacuated solar collector with operating range of about $50-85^{\circ}C$ as thermal energy source and solar photovoltaic as electric energy source. To achieve that object, this study set up the demo-plant, then estimated and analyzed the usefulness, the safety, and the reliability through pre-tests during short time ahead of the long-time operation. This study showed that the pumps, which are including sea water supply, ejector, hot water supply, and fresh water pumps, were operated one after another. And, the fresh water yield was closely related with the solar irradiance and lower supply temperature of hot water was revealed more reasonable for the solar energy desalination system. That is due to the insufficient area than the solar collector area being required that was estimated through the performance tests of the fresh water generator.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.4
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• pp.280-286
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• 2008

In this study, characteristics simulation of heat pump system is investigated for heating and cooling using sewage water as a heat source. A simulation program for preestimate operation characteristics of heat pump system is developed. The performance of this system is resolved by several variables and the characteristics which is based on actual air and sewage temperature data. The simulation results agree well with the experimental values of COP. In the analysis of system characteristics, the COP is changed between $3\sim5$ in winter season for heating load, $4\sim6$ in summer season for cooling load. As the results of Life Cycle Cost analysis over a 15 year life cycle, the energy cost could be reduced by 250 million won if a heat pump system was used instead of a conventional boiler and an absorbtion refrigerator on the office building.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.164-168
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• 2011

This study of PV modules in the external environment, learn about the mechanical strength characteristics, the module will investigate the aluminum frame. Positive support in the module by wind loads if uniformly distributed load acting on the front glass of the module size and elongation(${\omega}$), and accordingly, depending on the bend is sealed inside the solar cell, micro-cracks that will occur. At this point the most damage-prone parts in a module, this module is part of the center of a strong wind load is applied by the destruction of the environment does not occur in the module frame to secure the reliability and to evaluate changes in the structure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.1044-1050
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• 2004

The present study has been conducted to develop a heat pipe heat exchanger for middle-high temperature ranged from 300 to $600^{\circ}C$. Heat transfer rate, overall heat transfer coefficient and temperature effectiveness were investigated using a heat pipe heat exchanger with Dowtherm A as working fluid. Theoretical analysis was also conducted, and the followings were obtained: (1) Heat exchange rate increased as waste gas temperature supplied to evaporator and frontal velocity in condenser increased, (2) Overall heat transfer coefficient increased by $3{\sim}7\%$ as frontal velocity in evaporator and condenser increased, (3) Temperature effectiveness was about $30\%$ in evaporator and was about $40\%$ in condenser, (4) Heat recovery rate was about $38\%$, (5) Pressure drop did not exceed $8\;mmH_{2}O$ under the running condition of $1{\sim}3Nm/s$, (6) Simulation results were corresponded with experimental results.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.214-217
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• 2006

p-type 비정질 실리콘 에미터와 n-type 실리콘 기판의 계면에 intrinsic 비정질 실리콘을 증착함으로써 계면의 재결합을 억제하여 20%가 넘는 효율을 보이는 이종접합 태양전지가 Sanyo에 의해 처음 제시된 후 intrinsic layer에 대한 연구가 많이 진행되어 왔다. 하지만 p-type wafer의 경우는 n-type에 비해 intrinsic buffer의 효과가 미미하거나 오히려 특성을 저하시킨다는 보고가 있으며 그 이유로는 minority carrier에 대한 barrier가 상대적으로 낮다는 것과 partial epitaxy가 발생하기 때문으로 알려져 있다. 본 연구에서는 partial epitaxy를 억제하기 위한 방법으로 증착 온도를 낮추고 QSSPC를 사용하여 minority carrier lifetime을 측정함으로써 각 온도에 따른 passivation 특성을 평가하였다. 또한 SiH4에 H2를 섞어서 증착하였을 경우 각 dilution ratio(H2 flow/SiH4 flow)에서의 passivation 특성 또한 평가하였다. 기판 온도 $100^{\circ}C$에서 증착된 샘플의 lifetime이 가장 길었으며 그 이하와 이상에서는 lifetime이 감소하는 경향을 보였다 낮은 온도에서는 박막 자체의 결함이 증가하였기 때문이며 높은 온도에서는 partial epitaxy의 영향으로 추정된다. H2 dilution을 하여 증착한 샘플의 경우 SiH4만 가지고 증착한 샘플보다 훨씬 높은 lifetime을 가졌다 이 또한 박막 FT-IR결과로부터 H2 dilution을 한 경우 compact한 박막이 형성되는 것을 확인할 수 있었는데 radical mobility 증가에 의한 박막 특성 향상이 원인으로 생각된다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.6
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• pp.596-604
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• 2005

This paper presents the work on evaluating the LCC (Life-Cycle Cost) of a heat pump system as unutilized energy system. The river water as an unutilized energy source was used for the heat source of heat pump system. LCC analysis is a concrete method for evaluating the economical efficiency of energy facilities of building. The present case study shows an example of adequate use of the LCC analysis on a heat pump system and conventional gas boiler and refrigerator for building heat supply. A life cycle of 20 years was used to calculated net present value of energy cost. Over a 20 year life cycle, the energy cost could be reduced by 612 million won if a heat pump system were used instead of a conventional boiler and an absorption refrigerator.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.6
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• pp.521-528
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• 2005

This study has been conducted to investigate the potential energy reserve amount of river water as energy resource with useful temperature difference. Since the river water temperature is one of the primary parameters deciding the potential amount of river water energy reserve amount, the climate change effects on it are critically important. In this study, the heat exchange processes and the inter-relationship between the air temperature and river water temperature have been theoretically analyzed. Based on the present study, the potential energy reserve of river water is calculated to amount to 192,000 Tcal/year. Among this, it is estimated that approximately 2,000 Tcal/year can be directly utilized for heat pump energy sources.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.501-505
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• 2006

A preliminary performance test of a 30RT 2-stage screw heat pump was carried out in order to develop a high performance large-scale unutilized energy source heat pump, which will be used in district heating and cooling. Two issues on the system control were investigated in this study, A stable 2-stage heating operation is guaranteed only if the load-side water inlet temperature is over a certain value, to where the 1-stage heating operation should be done first from a cold start. An oil shortage problem in low stage compressor, which depends on the degree of suction superheat, was solved by the proper oil level control scheme.