• Advances in Energy Research
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• 제5권3호
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• pp.227-237
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• 2017

The continuous increase of emission rates of green house gases and the effects on global warming added a new dimension to the problem of substituting the petroleum and its derivatives by environment friendly and sustainable energy sources for the world. Solar and wind energy appear at the top of the list of renewable of high potential, widely available, of dominated technology and well accepted. Brazil is one of the few countries in the world that receives number hours of sunshine exceeding 3,000 hours per year with a daily average of 4.5 to 6 kWh. However, this potential is largely unexplored and poorly tapped. The number of renewable systems implanted in Brazil has grown in recent years, but still insignificant when compared, for example, with Germany and Spain among others. This paper presents the results of an optical study on small concentration solar collector with evacuated tube enveloping the absorber and internal reflective surface fixed on the bottom part of the evacuated tube. The designed collector has a 2D geometrical concentration ratio between 2.455 and 4.91. The orientation of the solar collector, the ratio of the radius of the receiver to the radius of the absorber, the incidence angle for each period of the year, the collector inclination angle, the aperture angle of the reflective surface, concentration and optical efficiency were determined. The ray traces and flux distribution on the absorber of the evacuated tube solar collector were determined by using the program Ray Optics Simulation. The optical efficiency varies during the year according to the solar declination. For the periods were the solar declination is close to zero the efficiencies are maximum, and the variation during the day is around 25.88% and 99.9%. For the periods were the solar declination is maximum the efficiencies are minimum, and the variation during the day is around 23.78% and 91.79%.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.149-153
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• 2011

The PC1D is widely used for modeling the properties of crystalline silicon solar cell. Optimized doping profile in crystalline silicon solar cell fabrication is necessary to obtain high conversion efficiency. Doping profile in the forms of a uniform, gaussian, exponential and erfc function can be simulated using the PC1D program. In this paper, the doping profiles including junction depth, dopant concentration on surface and the form of doping profile (gaussian, gaussian+erfc function) were changed to study its effect on electrical properties of solar cell. As decreasing junction depth and doping concentration on surface, electrical properties of solar cell were improved. The characteristics for the solar cells with doping profile using the combination of gaussian and erfc function showed better open-circuit voltage, short-circuit current and conversion efficiency.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.57-61
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• 2002

This paper presents development of a SEC(Solar Energy Concentration) utilizing the concentrated solar beam radiation for joining engineering thermoplastics such as Acrylonitrile/Butadiene/Styrene(ABS), Polycarbonate(PC) and Polymethylmethacrylate (PMMA). In addition, to study the joining of the materials, necessary experimentation with applying primer was performed. Tensile tests were conducted to determine the bond strength achieved at the specimen Joint interface. Microscopic examinations of the fractured joints were performed in order to analyze the overall bond quality. Finally, the results in terms of bond strength achieved at the joint interface and energy consumed in the process was compared with those obtained with similar thermoplastic joining technique utilizing microwave energy.

• 대한기계학회논문집B
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• 제39권12호
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• pp.927-934
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• 2015

고일사 지역인 사우디아라비아에서 태양열로 구동하는 흡수식 냉동 시스템 개발을 염두에 두고, 본 논문에서는 태양을 추적하는 선형 프레넬 반사판 시스템의 집광 특성을 수치해석 하였다. 몬테카를로 광선추적법을 기반으로 하는 광학 프로그램을 통해 집광 열유속, 집광 효율, 집광 에너지를 일년을 대표하는 춘분, 하지, 추분, 동지 날짜에 계산하였다. 동지를 제외하면, 9 시에서 15 시까지는 집광 성능이 일정한 가운데, 집광 효율도 70% 이상으로 높게 나타났다. 이 시간대에서 흡수기 중심 20% 영역에 모이는 최대 열유속은 하지 때 약 $13.0{\sim}14.6kW/m^2$ 범위에서 변했다. 집광 시스템의 설계 인자 중에서 흡수기 설치 높이, 반사판의 폭, 반사판 사이의 거리가 집광 효율을 조사해 보면, 흡수기 설치 높이는 반사판의 폭에 관계없이 5 m 에서 최적의 성능을 나타냈다. 반사판의 폭이 작을수록 집광 효율이 좋지만, 반사판의 폭은 집광 되는 에너지에 직접적으로 비례하기 때문에 냉동 시스템의 용량에 맞추어 설계가 필요하다. 본 연구는 흡수기의 열전달 해석의 중요한 선행조건이므로 향후에 광학-열전달 연계된 해석을 통해 전체 시스템의 성능을 예측하고 설계하는데 활용할 수 있을 것이다.

• Current Photovoltaic Research
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• 제4권2호
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• pp.31-41
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• 2016

n-type PERT (passivated emitter, rear totally diffused) bifacial solar cells with boron and phosphorus diffusion as p+ emitter and n+ BSF (back surface field) have attracted significant research interest recently. In this work, the influences of wafer thickness, bulk lifetime, emitter, BSF on the photovoltaic characteristics of solar cells are discussed. The performance of the solar cell is determined by using one-dimensional solar cell simulation software PC1D. The simulation results show that the key role of the BSF is to decrease the surface doping concentration reducing the recombination and thus, increasing the cell efficiency. A lightly phosphorus doped BSF (LD BSF) was experimentally optimized to get low surface dopant concentration for n type bifacial solar cells. Pre-oxidation combined with a multi-plateau drive-in, using limited source diffusion was carried out before pre-deposition. It could reduce the surface dopant concentration with minimal impact on the sheet resistance.

• 한국태양에너지학회 논문집
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• 제31권2호
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• pp.53-62
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• 2011

Heliostat in the tower type solar thermal power plant is a sun tracking mirror system to reflect the solar energy to the receiver and the optical performance of it affects to the efficiency of whole power plant most significantly. Thus a proper design of structure of the heliostat reflective surface could be the most important step in the construction of such power plant. The work presented here is a design of structure of optical surface of heliostat, which will be used in 200kW solar thermal power plant. The receiver located at 43(m) high from ground in tower has $2{\times}2$(m) rectangular shape. We first developed the software tool to simulate the energy concentration characteristics of heliostat using the ray tracing technique. Then, the shape of heliostat reflective surface is designed with the consideration of heliostat's energy concentration characteristics, production cost and productivity. The designed heliostat's reflective surface has a structure formed by canting four of $1{\times}1$(m) rectangular flat plate mirror facet and the center of each mirror facet is located on the spherical surface, where the spherical surface is formulated by the mirror facet mounting frame.

• 대한기계학회논문집B
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• 제35권10호
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• pp.989-996
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• 2011

태양의 집광 열유속을 이해하는 것은 태양에너지를 이용하는 시스템의 해석과 설계에 중요하다. 본 연구는 우수한 유연성과 확장성을 가진 몬테카를로 광선추적법에 기반하면서 태양주연감광과 반사판 표면 기울기 에러를 고려하는 알고리듬 개발과 이를 통한 태양 열유속 해석에 초점을 맞추고 있다. 검증을 위해 한국에너지기술연구원 태양로에서 측정된 열유속과 비교했을 때, 모델링 결과가 측정 에러 범위인 10% 이내에서 잘 일치하였다. 개발된 모델을 통해 태양로의 집광 성능을 2 mrad 의 추적 정밀도에 최대로 도달 가능한 집광비가 4400 sun 으로 평가하였다. 열유속의 측정 위치에 따른 변화와 수광각에 따른 분포를 통해 화학반응기나 보조집광기 설계에 필요한 상세한 정보를 제공하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.450-451
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• 2008

비정질 실리콘 태양전지는 n-i-p형 구조가 일반적이며, 각 층의 두께와 도핑농도가 태양전지의 효율을 결정하는 중요한 요인이다. 최대의 효율을 얻을 수 있는 태양전지 설계를 위해 AFORS HET 시뮬레이션을 통하여 n층의 두께와 도핑농도, 그리고 p층의 도핑농도롤 변화시켰다. 최적화 결과, a-Si:H(n) 층의 두께 1nm, a-Si:H(n)층의 도핑농도 $2\times10^{20}cm^{-3}$, a-Si:H(p+)층의 도핑농도 $1\times10^{19}cm^{-3}$에서 $V_{oc}$=679.5mV, $J_{sc}$=39.02mA/$cm^2$, FF=83.71%, Efficiency=22.21%의 고효율을 얻을 수 있다. 본 연구를 통하여 실제의 높은 효율을 갖는 태양전지 설계와 제조 시에 이용할 수 있을 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.684-687
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• 2007

Research on the solar thermal hybrid power generation technology which uses solar thermal chemical reaction has been carried out in KIER, The research covers development of solar concentration system and solar reactor for methane steam reforming reaction. This paper introduces a brief review and prospects of oversea's researches in similar areas and KIER's research progresses up to now.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.35.1-35.1
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• 2010

The Cu(In,Ga)Se2(CIGS) thin film solar cells have been achieved until almost 20% efficiency by NREL. These solar cells include chemically deposited CdS as buffer layer between CIGS absorber layer and ZnO window layer. Although CIGS solar cells with CdS buffer layer show excellent performance, many groups made hard efforts to overcome its disadvantages in terms of high absorption of short wavelength, Cd hazardous element. Among Cd-free candidate materials, the CIGS thin film solar cells with Zn compound buffer layer seem to be promising with 15.2%(module by showa shell K.K.), 18.6%(small area by NREL). However, few groups were successful to report high-efficiency CIGS solar cells with Zn compound buffer layer, compared to be known how to fabricate these solar cells. Each group's chemical bah deposition (CBD) condition is seriously different. It may mean that it is not fully understood to grow high quality Zn compound thin film on the CIGS using CBD. In this study, we focused to clarify growth mechanism of chemically deposited Zn compound thin film on the CIGS, especially. Additionally, we tried to characterize junction properties with unfavorable issues, that is, slow growth rate, imperfect film coverage and minimize these issues. Early works reported that film deposition rate increased with reagent concentration and film covered whole rough CIGS surface. But they did not mention well how film growth of zinc compound evolves homogeneously or heterogeneously and what kinds of defects exist within film that can cause low solar performance. We observed sufficient correlation between growth quality and concentration of NH3 as complex agent. When NH3 concentration increased, thickness of zinc compound increased with dominant heterogeneous growth for high quality film. But the large amounts of NH3 in the solution made many particles of zinc hydroxide due to hydroxide ions. The zinc hydroxides bonded weakly to the CIGS surface have been removed at rinsing after CBD.