• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.113-120
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• 2007

The 5kWt dish solar collector is designed and the preliminary performance test for this is carried out. The diameter of the parabolic dish is 3.2 m, and its focal length is 2 m. It consists of 10 small reflectors which have their own curvatures, and the effective reflecting area is $5.9\;m^2$, and the rim angle of the dish is $43.85^{\circ}$. The reflectivity of reflectors is 0.95, and the thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. A quartz window is installed at the receiver aperture to minimize the convective heat loss and prevent air leakage. In order to increase the heat transfer area, porous materials (nickel-alloy) are inserted into the receiver. Air flows into the upper part of the receiver which is the opposite side of the aperture. After the air flows through the inside of the receiver, that goes out of the receiver through 3 exits which are located near the aperture. The volumetric flow rates of air are varied from 600 to 1200 L/min. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases.

• Membrane Journal
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• v.17 no.4
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• pp.302-310
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• 2007

The effects of various system parameter on the absorption of sulfur dioxide into the absorbent liquid were investigated in a circulatory porous polymer membrane contactor. A feed gas and an absorbent used in the study were the gas mixture of air and $SO_2$ and the $Na_2SO_3$ aqueous solution, respectively. The separation of sulfur dioxide was measured in terms of the concentration of $Na_2SO_3$ absorbent, the concentration of sulfur dioxide, the feed flow rate, the absorbent velocity and the different membrane material. As the concentration of absorbent increased from 0.05 to 0.2 M, the removal efficiency increased from 74 to 100%. By increasing the concentration of sulfur dioxide from 700 to 2,500 ppm, the removal efficiency decreased from 100 to 75%. Also as the absorbent velocity increased from 2.5 to 15 mL/min, the removal efficiency increased from 85 to 100%. As the porosity of the membrane increased, the removal efficiency increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1367-1373
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• 2011

This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than $90^{\circ}C$ when the heat source and sink temperatures were $50^{\circ}C$. Experiments with various $NH_3/H_2O$ mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific $NH_3$ concentration.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.795-800
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• 2009

In this study, the $CO_2$ removal characteristics of the Vortex tube type absorbtion apparatus were investigated to enhance the compactness of $CO_2$ absorption process and to reduce the amount of absorbing solution of the $CO_2$ separation process. The Vortex tube with the diameter of 17 mm and the length of 250mm was introduced in the experimental apparatus to treat $20Nm^3/hr$ of $CO_2$ containing flue gas. The flue gases for experiments containing 11~13 vol% of $CO_2$ were supplied from the coal-firing CFBC power plant with 12 ton/hr of steam producing capacity. The mixed solutions of 20 wt% of MEA as base solution with the adding solutions like HMDA, AMP and KOH were used as absorbents. The experiments were executed under the various conditions like the absorbing solution concentrations in the range of 20 to 50 wt%, the flow rate of $CO_2$ containing flue gases in the range of 6 to $15Nm^3/hr$ and the flow rate of absorbing solution in the range of 1.0 to 3.0 l/min. As a results, the $CO_2$ removal efficiency of mixed absorbent of 20 wt% of MEA with HMDA was remarkable. From this study, we concluded that the efficient separation of $CO_2$ from flue gases using the features of the Vortex tube type absorbing unit for gas/liquid contact and the separation of gas/liquid be possible. But more works are needed to increase the $CO_2$ removal efficiency of Vortex tube process.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.683-683
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• 2013

박막태양전지의 일종인 CIGS 태양전지는 직접천이형 반도체로 광흡수계수가 $1{\times}10^5cm^{-1}$로 매우 높고, 전기광학적 안정성이 우수하여 실리콘 결정질 태양전지를 대체할 고효율 태양전지로 각광받고 있다. CIGS 태양전지는 광흡수층 공정방법에 따라 다양한 결정구조 및 효율 차이가 나타난다. 본 실험에서는 Sputtering방법으로 금속전구체를 증착하고, Sequential process를 이용하여 고온에서 셀렌화 열처리를 수행하였다. Soda-lime glass 기판에 배면전극으로 Mo를 증착하고, 1단계로 CuIn0.7Ga0.3 조성비의 타겟을 이용하여 Sputtering법으로 $1.0{\sim}1.2{\mu}m$두께의 CIG 전구체를 증착하였다. 2단계로 CIG 전구체에 분자빔증착기를 이용하여 Se를 증착하고, 열처리를 통하여 CIGS 화합물 구조의 박막을 형성시켰다.증착된 CIGS 박막은 광전자분광분석기로 원소의 화학적 결합상태를 확인하고, in-situ 엑스선회절분석을 통해 Se층의 증착두께와 열처리 온도 변화에 따른 CIGS 층의 결정구조 및 결정화도 변화를 분석하였다.

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.69-69
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• 2007

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.199.2-199.2
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• 2015

전이금속 칼코겐화합물(TMD)은 2차원 박막 물질로, 그래핀과 함께 차세대 사물인터넷에 적용할 수 있는 전자소자의 소재로 활용될 것으로 기대되고 있다. 특히 TMD는 그래핀과 다르게 1.2 eV 이상의 넓은 밴드갭을 지녀, 기존 실리콘 기반 반도체 소자를 대체할 차세대 물질로 각광받고 있다. TMD는 또한 실리콘 등의 3차원 반도체보다 광전효율이 뛰어나며, 이를 활용한 광전소자의 개발 및 연구가 활발히 진행되고 있다. 그러나 TMD는 그 두께가 나노미터 단위로 매우 얇아 광흡수율이 매우 떨어지는 단점이 있다. 우리는 이러한 TMD 기반 광전소자의 광흡수율을 향상시키기 위해 광전효율이 매우 뛰어난 페로브스카이트(Perovskite)를 TMD 채널 위에 덮음으로써, 이종접합 광전소자를 구현하였다. TMD 물질은 이황화 몰리브데넘($MoS_2$)을 선택하였으며, 광흡수층으로 선택한 페로브스카이트는 $MAPbI_3$을 스핀 코팅을 통해 TMD 채널 층에 접합하였다. 우리는 Photoluminescence 및 UV-Vis 측정을 통해 페로브스카이트 및 페로브스카이트/$MoS_2$ 층의 광특성을 측정하여 페로브스카이트에서 생성된 광캐리어가 확산되어 $MoS_2$에 전달되는 것을 확인하였다. 우리는 추가로 4가지 서로 다른 파장대의 레이저(520, 655, 785, 850 nm)를 이용하여 페로브스카이트 광흡수층이 있을 때와 없을 때의 $MoS_2$ 광검출기의 성능 변화를 관찰하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.389-397
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• 2014

An absorption chiller-heater using only a natural refrigerant hardly causes any environmental pollution. In an absorption chiller-heater, the performance of its high-temperature generator, which uses exhaust gases, is essential to achieving superior system performance. To investigate the performance of such a high-temperature generator, a laboratory-scale high-temperature generator working with exhaust gases was designed and tested. Changes in the performance of the high-temperature generator as a function of inlet conditions of the absorbing solution, such as air inlet temperature and mass flow, were investigated. It was observed that when the air mass flow rate ratio was increased from 80% to 120%, the heat capacity was increased by 30%, 33%, 34%, and 37%, respectively. Additionally, when the air inlet temperature was elevated from $170^{\circ}C$ to $210^{\circ}C$ for absorption solution concentrations of 56%, 55%, 545, and 53%, the heat capacity increased by 140%, 160%, 220%, and 224%, respectively.

• Bulletin of the Korea Photovoltaic Society
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• v.2 no.2
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• pp.21-28
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• 2016

3족과 5족 물질로 구성된 III-V 고효율 화합물 태양전지는 태양광 스펙트럼에 대한 많은 파장영역대의 빛을 흡수할 수 있는 장점을 갖고 있어 지구상에서 만든 태양전지 중 가장 효율이 높다. 그러나, III-V 화합물 물질은 실리콘 보다 고가의 비용이 들므로 이를 극복하기 위해서 집광렌즈 및 빛을 추적하기 위한 추적기 등 집광시스템으로 구성되어야 한다. 본고에서는 고효율의 III-V 화합물 태양전지의 현재 기술개발동향 및 고효율 저가화를 위한 방안으로 기판재활용 기술, 태양광 태양열 복합활용 시스템 및 소형집광모듈 등을 소개하고자 한다.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.570-575
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• 2007

The thermal performance of the air receiver filled with porous material for 5kWt dish solar collector installed in Inha University, Korea, is experimentally investigated. The diameter of the parabolic dish is 3.2 m, and its focal length is 2 m. It consists of 10 small pieces of glasses which have their own curvatures, and the effective reflecting area is 5.9 m2. The reflectivity of the glass is 0.95, and the thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. A quartz window is installed at the receiver aperture to minimize the convective heat loss and prevent air leakages. In order to increase the heat transfer area, porous material (nickel-alloy) is inserted into the receiver. Air flows into the upper part of the receiver, which is the opposite side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 3 exits which are located near the aperture. The volumetric flow rates of air are varied from 600 to 1200 L/min. The thermal efficiency of the receiver ranges from 82% - 92% depending upon the flow rate. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases as expected. These results from the experiment will be useful for the applications to air heating receivers and solar reactors.