• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.58.3-59
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• 2018

We investigate velocity oscillations in a solar quiet region by using the spectral data of the $H{\alpha}$ and Ca II $8542{\AA}$ lines. The data were acquired by the Fast Imaging Solar Spectrograph installed at the 1.6 m Goode Solar Telescope of Big Bear Solar Observatory. According to Chae & Litvinenko (2018)'s theoretical work, there is a correlation between dominant period of the oscillations and the temperature of the temperature minimum region in a non-isothermal atmosphere. In our study, we measure the temporal variations of the intensity and the line of sight Doppler velocity, and find out the relations between the intensity and dominant period of the oscillations. In addition, we investigate oscillations in a few distinct regions and discuss regional characteristics of the oscillations.

• Current Photovoltaic Research
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• v.11 no.4
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• pp.118-123
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• 2023

The main cause of solar facility fires is arc, and in the last 3 years ('16 to '18), about 80% of domestic solar facility fires have been caused by arcs. The capacity of solar power facilities installed around the world continues to increase, and fires caused by arcs are also expected to increase as the solar power generation facilities that were initially installed become obsolete, In this paper, an arc generation test was conducted based on the UL1699B test standard. As a result of the test, the arc generation satisfied the minimum arc current according to the test conditions, and DC arc characteristics were analyzed through data such as arc voltage and arc current according to variables such as speed of moving electrodes and electrode spacing.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.297-302
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• 2011

In this study, used Trnsys and will apply metropolitan city distinguishes, fixations and BIPV systems the photovoltaic module arrangement environment which receives solar radiation quantity plentifully from the case design process which and most the outcome value simulation did analyzed. The climate data uses each metropolitan city distinguishes 20 average weather data, With measured values of horizontal solar radiation. The error scope appeared with 0.1%~6.7%. Variable of module arrangement Azimuth and angle of inclination of module and comparison group Module on due south direction angle of inclination $45^{\circ}$ day time set with the yearly average solar radiation quantity which receives. The result When the case comparison group which arranges a solar storehouse module with optimum environment and comparing until the minimum 1.4% - maximum 10.9% the solar radiation quantity difference appears with the thing, metropolitan city distinguishes considers the case solar radiation quantity which will arrange a photovoltaic module and that must establish with optimum environment judges.

• Journal of Environmental Science International
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• v.22 no.7
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• pp.885-893
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• 2013

The purpose of this study was to analyze the effects of partial solar eclipse on 21 May 2012 in Korea on meteorological variables in Busan. 0800 LST(Local Standard Time) solar radiation was similar or lower than 0700 LST solar radiation, and sunshine duration decreased by 0.2~0.5 hours in Busan and great cities under the influence of the partial solar eclipse. Temperature drop due to the partial solar eclipse was $0.2{\sim}2.0^{\circ}C$, time taken to arrive at maximum temperature after onset of eclipse was 8~62 minutes, and time taken to arrive at minimum temperature after maximum eclipse was -9~17 minutes in Busan. Change of wind speed was negligible as partial solar eclipse occurred in the morning. Soil temperature of 5 cm was minute as well, the increase of soil temperature due to sunset was delayed by more than 1 hour.

• Journal of the Korean Solar Energy Society
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• v.34 no.3
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• pp.57-65
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• 2014

As the environmental regulations is more strengthened, the study of the renewable energy system and waste heat for electricity production is being accelerated. In this study, the performance and power generation rate of solar power generation by using R134a Rankine cycle was analyzed with solar radiation and mass flow rate of R134a. As a result, the maximum and minimum collected heat of solar collector was 20.4 kW and 13.6 kW at October and December, respectively. Besides, the highest generator power was generated at October and it was 0.91 kW/day, while the lowest generator power is occurred at December and it was about 0.85 kW/day.

• Solar Energy
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• v.20 no.1
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• pp.73-80
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• 2000

Considering the optical performance of the reflector and analyzing heat losses from the receiver, the optimal diameter of the absorber for a PTC(Parabolic Trough Concentrator) system was numerically determined. The results of this study were compared with the results of the IST (Industrial Solar Technology)-PTC test to verify the validity of the model. Good agreement was obtained with the deviation range from 0.4 to 7.7%. Generally, the net energy gained by the receiver shows the maximum at the particular absorber diameter and the specific gap size between the absorber and the glass envelop because the heat losses from the receiver becomes the minimum. The results showed that the conductive and convective heat losses became the minimum when the gap size was 7 to 10mm. Finally, it was known that the optimal absorber diameter was 62mm at $100^{\circ}C$, 57mm at $150^{\circ}C$, and 53mm at $200^{\circ}C$ of the absorber surface temperature, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.136.2-136.2
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• 2011

In this work, we analyzed correlations between life-cycle greenhouse gas (GHG) emissions and life-cycle cost of energy resources. Energy resources studied in this paper include coal, natural gas, nuclear power, hydropower, geothermal energy, wind power, solar thermal energy, and solar photovoltaic energy, and all of them are used to generate electricity. We calculated the mean values, ranges of maximum minus minimum values, and ranges of 90% confidence interval of life-cycle GHG emissions and life-cycle cost of each energy resource. Based on the values, we plotted them in two dimensional graphs to analyze a relationship and characteristics between GHG emissions and cost. Besides, to analyze the technical maturity, the GHG emissions and the range of minimum and maximum values were compared to each other. For the electric generation, energy resources are largely inverse proportional to the GHG emission and the corresponding cost.

• Journal of the Korean Solar Energy Society
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• v.36 no.2
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• pp.73-78
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• 2016

This study investigates the main factors of fire prevention, such as spontaneous ignition and flash point, while using Diehylene Glycol (DEG) as the antifreeze for automobile and industrial machines. Our results show the flash point of $142^{\circ}C$ and the minimum ignition temperature of $388^{\circ}C$ in the range of $130{\mu}{\ell}{\sim}150{\mu}{\ell}$. By increasing temperature to ignite in 1 second, an instantaneous ignition temperature of the sample is $569^{\circ}C$ in the sample amount of $140{\mu}{\ell}$.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1110-1111
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• 2008

The life time of PV module is semi-permanent. But, because of installation and module fabrication process, its important part can not be finished. In this paper, we analyze 15 years old modules made from different company. Among the PV modules, the maximum power drop ratio was 12.23% minimum and 80.63% maximum. Also the effect of solar cell's short circuit current difference was analyzed. The PV module exposed about 65days, its the maximum power drop ratio was 1.29% minimum and 23.43% maximum. It is for reduction of current value. And the reason for current reduction was due to reduction of parallel resistance of solar cell. To prevent early degradation, it is need to have attention to fabrication, installation and maintenance.

• Journal of the Korean Solar Energy Society
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• v.36 no.3
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• pp.53-61
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• 2016

Solar assisted heat pump system uses solar thermal energy as a heat source of evaporator of heat pump. So, COP can be enhanced as well as collector efficiency. For improving performance of this system, some research about hybrid solar collector that has fin-and-tube heat exchanger has been conducted. This collector can get a thermal energy from ambient air for liquid heating, so heated liquid can be used as a heat source of evaporator in heat pump even the solar radiation is not enough. In this study, numerical analysis was conducted for confirming heat gain of liquid according to fin height and pitch of fin-and-tube heat exchanger in collector. As a result, higher heat gain was obtained on lower fin height and narrow fin pitch, but the pressure drop also increased with increment of heat gain. Thus the JF factor considering both heat transfer enhancement and pressure drop was investigated and the maximum value was shown when the fin height and pitch were 40mm and 45mm. So it is considered that this installation condition has a highest heat transfer improvement when comparing with pressure drop. However heat gain of liquid at this condition was less than the other installation conditions of fin pitch on same height. Then, after establishing a proper minimum heat gain of liquid, actual production and experiment of collector will be conducted with fin height and pitch showing maximum JF factor and satisfying selected minimum heat gain of liquid on the basis of results of this study.