• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.188-193
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• 2012

Recently, the nanofluid which is stably dispersing or suspending of nanoparticles in the conventional heat transfer fluids (HTF) such as water and ethylene glycol has attracted significant interests as a solar thermal energy absorbing medium because they have excellent absorption and thermophysical properties compared to the typical HTF. In the present study, the efficiency of nanofluid-based flat-plate solar collector is analytically evaluated using the theoretical model of energy balance equation. The theoretical model considers the incoming solar radiation as a volumetric heat generation and the water-based single wall carbon nanohorn(SWCNH) nanofluid is used as a solar energy absorbing medium. Finally, the efficiency of nanofluid-based collector is calculated according to the volume fraction of SWCNH using the analytical solution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.1
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• pp.8-14
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• 2014

We have performed experiments to enhance the stratification in a storage tank in order to raise the collector efficiency and solar fraction in solar thermal systems. The storage tank with a spiral jacket in the side wall has a scroll-shaped heat exchanger coil added to the upper part. The performance was compared between only the side and upper-side heating part through simulation using TRNSYS under the same weather conditions and initial conditions. As a result, the upper-side heating has a 4.2% advantage in solar fraction, but almost no increase in collector efficiency.

• Proceedings of the Korea Contents Association Conference
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• 2017.05a
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• pp.445-446
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• 2017

신재생 에너지 분야의 산업과 기술의 발달과 함께 스마트 그리드와 에너지 저장 시스템이 주목받고 있다. 기존의 에너지 공급망에 정보통신기술(ICT)을 접목하여 에너지 공급자와 소비자가 양방향으로 실시간 정보를 교환함으로써 에너지 효율을 최적화하는 차세대 지능형 에너지망에 대한 수요가 늘고 관리기술에 대한 요구가 증가함에 따라, 다양한 에너지 공급원마다의 최적화된 운영시스템을 요구하고 있다. 본 논문에서는 산업분야에서 사용되고 있는 태양열에 기반한 시스템과 누적된 기상 데이터와 집열량에 대한 데이터를융합분석하여 수평면전일사량을 예측할 수 있는 시스템을 제안한다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.122-128
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• 2001

The simulation analyses of a dish solar power system with stirling engine in this study are applied to system performance prediction if four different test sites; Seoul, Pusan and Cheju in Korea, and Naha in Japan. The effects of difference of concentrator type such as monolithic and stretched-membrane construction on system efficiency are also evaluated. The total amount of generated power for a year depends on the site. However the total maximum system efficiency in every site is approximately 16% and there isnt striking difference. It is also found that the maximum collector efficiency of stretched-membrane concentrator is about 3∼15% lower than that of the monolithic type.

• Journal of the Korean Solar Energy Society
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• v.34 no.3
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• pp.30-41
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• 2014

PV/Thennal combined system is a solar energy device that uses photovoltaic module as thermal absorption plate, producing thermal energy as well as electricity which can be utilized in buildings. The system removes heat from PV module through air or liquid and its efficiency will vary dependant on the thermal medium. The heat as the forms of hot air or hot water can be utilized for building use, like space heating and hot water. A significant amount of research and development on hybrid PV/thermal(PVT) collectors has been carried out. This study reviews literature on the research of air-based hybrid PVT collectors in terms of their design and energy performance.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.182-185
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• 2008

The thermal performance of air receiver with a change of flow direction for dish solar collector. This system is installed and operated in Incheon, Korea. 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. Experiments are being carried out to investigate the thermal performance variation of the receivers with several design parameters such as the shape of the receiver, the flow directions and the flow rate of air. First, 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. Second, air flows into the backside of the receiver, Which is the forward side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 1 exit. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases as expected.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.108-114
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• 1996

It is one of the most important factors to enhance the efficiency of the solar collectors by in-creasing collecting efficiency and decreasing heat loss. The pulse electrodeposition method has been involved in this study to improve characteristics of the solar selective coating on 230cm${\times}$60cm substrates and electrical efficiency of the process. The composition of the electrolyte was 280 g/$\ell$ chromic acid, 15 g/$\ell$ propionic acid, and 10 g/$\ell$ appropriate additive. 230cm${\times}$60cm copper and aluminium sheets were utilized as the substrates. It has been observed that the black chrome coatings exhibited reasonable optical properties for commercialization when the plating parameters were properly controlled; the absorptance was 0.98 and 0.97 and omittance was 0.17 and 0.23 for copper and aluminium substrate, respectively. This study implies that the pulse current electrolysis method could be applied to the large scale substrates, and the various products can be avilable after the consideration of the thermal conductivity, heat transfer efficiency and cost problems of the substrates.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.155-160
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• 2007

This study shows the results on thermal performance test with domestic solar collector for low-temperature applications using KS, then reveals the efficiency difference between KS and EN standard. Using the test results, this study Presents the status of thermal performance with domestic solar collector including flat-plate, single evacuated, and double evacuated (with mirror or U-tube) solar collector.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.4
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• pp.213-219
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• 2015

A thermal storage tank with internal heat exchange coils is commonly used in solar thermal systems with a collector area below $100m^2$. The coils are installed in the lower part of the tank because the temperature of the upper part of the tank can drop if the outlet temperature of the collector becomes lower than the upper temperature of the tank, which is a kind of temperature reversal. As an alternative to the well-mixed storage tank with lower coil only, we have proposed a tank with lower and upper coils and have achieved superior thermal stratification in the tank, which results in increased collector efficiency and solar fraction. But, the phenomenon of temperature reversal was often observed in the tank when the load or solar radiation changed rapidly. In the present work, revised control was successfully applied, i.e., to heat only the lower coil using a three way valve if temperature reversal occurs and to operate the collector at a low flow rate when the quality of solar radiation is not good.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.9
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• pp.361-366
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• 2016

As an alternative of well-mixed storage tank with lower coil only, we have proposed a tank with lower and upper coils and verified a superior thermal stratification in a tank, which results in increased collector efficiency and solar fraction. But the phenomenon of temperature reversal was often experimentally observed in the tank, so a revised control was successfully applied which is to heat only lower coil using three way valve if temperature reversal occurs and to operate the collector with low flow rate when the condition of solar radiation is not good. In the present study, using TRNSYS we compared the existing lower heating and the proposed lower and upper heating with a control preventing temperature reversal. The results showed that the proposed method has an increase of collector efficiency by 5.1% and solar fraction by 3.2%.