• 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.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.227-232
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• 2008

Stirling engine for solar thermal power is an essential part of Dish-Stirling system which generates electricity by using direct normal irradiation and will go into commercialization in near future. For the Stirling engine used in this study is Solo 161 model the capacity of which is 10 kWe and was already used for the Dish-Stirling system of KIER in Jinhae. The receiver of Stirling engine absorbes concentrated solar radiation and transfer it to working fluid of Hydrogen. The working condition of striling engine is high temperature and high pressure to make high efficiency. Therefore the receiver should stand against high temperature of above 800 $^{\circ}C$ and high pressure of max. 150 bar with good performance of heat transfer. The receiver is composed of 78 Inconel tubes of 1/8" with thickness of 0.71 mm and two reserviors which is connected with two cylinders. In order to know the charaterristics of heat transfer of Stirling engine receiver, simulation on the heat transfer of the receiver of Solo 161 is conducted by using CFD code of Fluent. The heat flux on the receiver surface has a shape of Gaussian distribution so, it is necessary to simulate a whole receiver. However, It is difficult and time consuming to simulate the whole receiver that one tube with different heat flux conditions are considered in this study. From the simulation results, heat transfer charateristics of receiver are observed and tube wall and fluid temperature and heat transfer coefficient are obtained and compared with the calculated results from Dittus-Boelter's correlation.

• Journal of the Korean Solar Energy Society
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• v.28 no.2
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• pp.1-9
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• 2008

This paper describes water circulation characteristics of a water/steam receiver at various heat fluxes. The water/steam receiver for a solar tower power system is a natural circulation type. Experimental conditions of water and steam were set at a pressure of 5 bar and temperature of $151.8^{\circ}C$. The experimental device for the water/steam receiver consisted of a steam drum, upper/lower header, riser tubes, and downcomer tube. The experiments were conducted by varying heat fluxes in terms of mass flow rate in each riser tube. However, the total mass flow rate on the riser tubes was fixed at 217.4 g/s. For the uniform heat flux, while the water temperature of the steam drum and upper header were kept at steady state, the temperature of the lower header was fluctuated. For the non-uniform heat flux, while the temperature of the steam drum was kept steady state, the temperature difference increased in the right and left side of the upper header, and the temperature of the lower header was fluctuated.

• Journal of the Korean Solar Energy Society
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• v.27 no.1
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• pp.55-61
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• 2007

This paper describes the procedure and calculation results of basic design and transient variation of performance of 1 MWe large scale solar thermal power plant (STPP) by using the commercial software of THERMOFLEX and TRNSYS, respectively. In order to simulate the transient variation of STPP, the results of basic design are necessary. The design standard of the STPP is 1 MWe generation with solar only at high DNI condition and then 0.6 MWe output power for 1 hour using stored energy when the DNI becomes lower unable to operate normally. The results of basic design show the important design data of flow rates, water/steam conditions at each equipments and the estimated efficiency of STPP. In addition, dynamic simulation results of STPP are predicted and plotted for one year and three different days weather data of Daejeon.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.62-67
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• 2009

This paper describes the characteristics of scroll type stirling engine receiver. Scroll type stirling engine operated scroll compressor and expander instead of piston. Pass dimension of the receiver was $14(W){\times}14(H)$ mm and total pass length was 5,049 mm. External dimension of the receiver was $300{\times}300mm$. The experimental facility consisted of parabolic dish concentrator, compressor to supply air, triplex air filter, and flowmeter. In this study, basic experimental conditions were set at a inlet pressure of 5 bar and volume flow rate of $25m^3/hr$. As a result, air temperature in receiver at each measuring position of point 1, 2, 3 were $241^{\circ}C$, $465^{\circ}C$, and $542^{\circ}C$ respectively at inlet pressure of 5.5 bar and volume flow rate of $24.6m^3/hr$. As DNI increasing, heat transfer coefficient of the receiver changed from $695W/m^2K$ to $827W/m^2K$. Average heat transfer coefficient of receiver in the experiment was $798W/m^2K$. In addition, receiver efficiency became about 83%.

• Journal of computational fluids engineering
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• v.20 no.2
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• pp.46-51
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• 2015

In this paper, we have developed numerical model for particulated flow through narrow slit using Eulerian-Granular method. Commercial software (FLUENT) was utilized as simulation tool and main focus was to identify the effect from various numerical options for modeling of solid particles as continuos phase in granular flow. Gidaspow model was chosen as basic model for solid viscosity and drag model. And lun-et-al model was used as solid pressure and radial distribution model, respectively. Several other model options in FLUENT were tested considering the cross related effect. Mass flow rate of the particulate through the slit was measured to compare. Due to the high volume density of the stacked particulates above the slit, effect from various numerical options were not significant. The numerical results from basic model were also compared with experimental results and showed very good agreement. The effects from the characteristics of particles such as diameter, angle of internal friction, and collision coefficient were also analyzed for future design of velocity resistance layer in solar thermal absorber. Angle of internal friction was found to be the dominat variable for the particle mass flow rate considerably. More defined 3D model along with energy equation for complete solar thermal absorber design is currently underway.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.112.2-112.2
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• 2011

PVT(Photovoltaic Thermal) 모듈은 태양광과 태양열 에너지를 동시 이용이 가능한 모듈로서 태양광전지(PV, Photovoltaic)모듈에 열교환기를 접합한 형태로 전기에너지뿐만 아니라 열에너지를 동시에 생산할 수 있는 시스템이다. 기존 PV 모듈은 일사량이 많으면 전력 생산량이 증가하는 동시에 PV모듈의 온도가 상승함에 따라 발전 효율이 감소하는 문제점이 있으며 일반적으로 $25^{\circ}C$이상 조건에서 모듈 온도가 $10^{\circ}C$ 증가할수록 발전효율의 약 4~5% 정도 감소하는 것으로 보고되고 있다. PVT 모듈은 기존 태양광모듈에 열교환기를 접합하여 냉각함으로써 PV모듈의 온도를 낮추어 발전효율을 증가시키는 동시에 부가적으로 발생하는 온수를 직접이용하거나 다양한 계통의 보조 열원으로 이용할 수 있는 장점이 있다. 본 연구에서는 수치해석기법(CFD)을 활용하여 PV모듈 냉각 및 온수 발생을 위한 열교환기를 설계하였으며 다양한 형상의 열교환기에 대해 유동해석을 수행하여 최적의 열흡수효율을 갖는 열교환기의 형상을 설계하였다. 또한 최적 설계된 PVT 모듈을 제작하여 실제 태양과 유사한 광원을 갖는 인공태양조건에서의 실내 실험을 통해 PVT 모듈의 성능을 검증하였으며 또한 실제 노상에 설치하여 ASHRAE 93-77의 실험기준과 ECN의 PVT 집열기 성능측정 가이드라인에 따라 옥외 시험평가를 하여 PVT 모듈의 성능 검증을 하였다. 최적 설계된 PVT모듈에 대한 성능평가 결과 기존 PV 모듈보다 발전효율이 약 15%(기존 발전효율 대비) 향상된 결과를 확인하였다.