• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.56-59
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• 2011

The process conditions for high efficiency industrial crystalline Si solar cells with selective emitter were optimized. In the screen printed solar cells, the sheet resistance must be 50-60V/sq. because of metal contact resistance. But the low sheet resistance causes the increase of the recombination and blue response at the short wavelength. Therefore, the screen printed solar cells with homogeneous emitter have limitations of efficiency, and this means that the selective emitter must be used to improve cell efficiency. This work demonstrates the feasibility of a commercially available selective emitter process, based on screen printing and conventional diffusion process. Now, we improved cell efficiency from 18.29% to18.45% by transition of heavy emitter pattern and shallow emitter doping condition.

• Journal of the Korean Solar Energy Society
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• v.34 no.1
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• pp.39-47
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• 2014

Solar applications analysis and building energy performance depend on the quality of the solar resource data available. Unfortunately, most of the weather stations do not measure solar radiation data in Korea, as a reason many researchers have studied different solar radiation estimation models and suggested to apply them to various locations in Korea. In addition, they also studied the impact of hourly global solar radiation on energy performance of an office building by comparing the simulated building energy consumptions using four different weather files, one using measured, and three estimated solar radiation from different models, which are Cloud-cover Radiation Model (CRM), Zhang and Huang Model (ZHM), and Meteorological Radiation Model (MRM), and concluded that there was some impact on energy performance of the building due to the using different solar radiation models. However, the result cannot be applied to all other buildings since the simulated office building for that study only used limited building characteristics such as using fixed values of solar heat gain coefficient (SHGC) and window-to-wall ratio (WWR), which are significant parameters related to solar radiation that affect to the building energy consumptions. Therefore, there is a need to identify how the building energy consumption will be changed by varying these building parameters. In this study, the impact of one measured and three estimated global solar radiation on energy performance of the office building was conducted taking account of SHGC and WWR. As a result, it was identified that the impact of four different solar radiation data on energy performance of the office building was evident regardless SHGC and WWR changes, and concluded that the most suitable solar models was changed from the CRM/ZHM to the MRM as SHGC and WWR increases.

• Journal of the Korean Solar Energy Society
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• v.32 no.2
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• pp.19-27
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• 2012

This paper describes an experimental study on efficiency of solar collector in solar water heating system connected to hourly water heating load. In general, the functional form of solar efficiency is expressed as a function of fluid temperature entering solar collector, ambient temperature, and solar irradiance. When energy saving from solar heating of water heating system is analyzed on along-term basis such as one year with given solar irradiance data, simplified analysis is more convenient han detailed system simulation for quick assessment. However, the functional form of the efficiency is not convenient for approximately simplified energy analysis because the inlet temperature can be obtained through a detailed system simulation. In the study, solar collector efficiency is obtained with various daily water heating load sand daily solar irradiance using experimental tests. The study also considers large residential buildings such as apartment buildings for application of solar water heating systems. From test results, it is found that daily solar collector efficiency is proportional to daily water heating loads and daily solar irradiance. The data obtained from the study can be utilized to find a functional relation between daily solar irradiance and daily heating load in stead of collector inlet temperature for application of solar collector efficiency to long-term approximated energy analysis of solar heating system.

• KIEAE Journal
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• v.14 no.2
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• pp.3-10
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• 2014

Impact by estimation error of hourly horizontal global solar radiation in a weather file on building energy performance was investigated in this study. There are a number of weather parameters in a given weather file, such as dry-bulb, wet-bulb, dew-point temperatures; wind speed and direction; station pressure; and solar radiation. Most of them except for solar radiation can be easily obtained from weather stations located on the sites worldwide. However, most weather stations, also including the ones in South Korea, do not measure solar radiation because the measuring equipment for solar radiation is expensive and difficult to maintain. For this reason, many researchers have studied solar radiation estimation models and suggested to apply them to predict solar radiation for different weather stations in South Korea, where the solar radiation is not measured. However, only a few studies have been conducted to identify the impact caused by estimation errors of various solar radiation models on building energy performance analysis. Therefore, four different weather files using different horizontal global solar radiation data, one using measured global solar radiation, and the other three using estimated global solar radiation models, which are Cloud-cover Radiation Model (CRM), Zhang and Huang Model (ZHM), and Meteorological Radiation Model (MRM) were packed into TRY formatted weather files in this study. These were then used for office building energy simulations to compare their energy consumptions, and the results showed that there were differences in the energy consumptions due to these four different solar radiation data. Additionally, it was found that using hourly solar radiation from the estimation models, which had a similar hourly tendency with the hourly measured solar radiation, was the most important key for precise building energy simulation analysis rather than using the solar models that had the best of the monthly or yearly statistical indices.

• Solar Energy
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• v.12 no.2
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• pp.79-86
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• 1992

To assure the appropriate role of solar energy in the future energy mix scenarios, considering the inevitable volatile and unstable energy market, it is urgent to introduce the "Soft Energy Path" concept. In Korean energy situation, the "Soft Energy Path" concept of solar energy has to be assured by the optimum technology mix of appropriate scale and quality for their individual tasks, especially in the industrial sector. So, the solar society is requested to establish an conceptional innovation regarding the merits of soft energy path and of ultimate potential of solar energy.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.120-125
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• 2012

Daegu Solar Power Tower Plant of a 200 kW thermal capacity uses an open air receiver. An air receiver is generally based on the volumetric receiver concept with porous ceramic absorbers. Because absorber material is important in the volumetric receiver, ceramic materials with excellent thermal conductivity, high solar absorptivity and good thermal stability have been researched. KIER also developed SiC honeycomb absorber modules and evaluated performance of the modules at the KIER solar furnace. For performance evaluation, we made an open volumetric receiver containing the modules and measured the outlet temperature and the efficiency. It is demonstrated that performance of the KIER absorber is comparable to that of a reference absorber developed by DLR.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.27-33
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• 2007

In this research, to develop the practical application system of fresh water generation system with plate-type fresh water generator using low pressure evaporation method is the main object, and to do that, this study used the evacuated solar collector with operating range of about $50-85^{\circ}C$ as thermal energy source and solar photovoltaic as electric energy source. To achieve that object, this study set up the demo-plant, then estimated and analyzed the usefulness, the safety, and the reliability through pre-tests during short time ahead of the long-time operation. This study showed that the pumps, which are including sea water supply, ejector, hot water supply, and fresh water pumps, were operated one after another. And, the fresh water yield was closely related with the solar irradiance and lower supply temperature of hot water was revealed more reasonable for the solar energy desalination system. That is due to the insufficient area than the solar collector area being required that was estimated through the performance tests of the fresh water generator.

• Solar Energy
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• v.13 no.2_3
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• pp.151-156
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• 1993

The comparison of solar energy technologies with conventional technologies involves more than just comparing the costs of supplying energy and provding capacity. Solar technologies supply energy in a sustainable manner while having minimal effects on the environment. When choosing between solar energy technologies and conventional technologies, first cost is a important factor. The environmental and other social benifits of using solar energy technologies contrasts sharply with the environmental degradation and social costs resulting from the use of conventional technologies. These hidden costs, sometimes called "social cost", are not included in conventional economics. This paper is emphasized that the consideration of social costs effects comparisons between renewable and conventional energy technologies is of importance.

• Journal of the Korean Solar Energy Society
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• v.33 no.6
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• pp.98-104
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• 2013

At the moment, in Korea, over 90% of energy resources depend on imports, and nearly 60% of electric energy is produced using fossil fuel. Therefore, the government adopted the Climatic Change Convention and has implemented the RPS system since 2012 to actively cope with the dependence on imported energy, and to grow and expand the new renewable energy industry. This study examined the performance results of mandatory supply of solar photovoltaic energy and non-solar photovoltaic energy assigned to providers and the present state after implementation of the RPS system. As a result, the achievement rate in 2012 was 64.7%. Especially, solar photovoltaic energy showed a high achievement rate of 95.7%, whereas non-solar photovoltaic energy showed a low achievement rate of 63.3% due to several problems and was highly dependent on the government. In 2013, the burden of each provider has increased due to more mandatory supply and addition of unfulfilled supply of 2012, and the separate mandatory supply of solar photovoltaic energy established for protection of the solar photovoltaic market is restricting investment. Therefore, there is a need to assign mandatory supply in consideration of the available amount of each new renewable energy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.4724-4747
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• 2016

To efficiently reduce on-grid energy consumption, the admission control algorithm in the hybrid energy powered cellular network (HybE-Net) with base stations (BSs) powered by on-grid energy and solar energy is studied. In HybE-Net, the fluctuation of solar energy harvesting and energy consumption may result in the imbalance of solar energy utilization among BSs, i.e., some BSs may be surplus in solar energy, while others may maintain operation with on-grid energy supply. Obviously, it makes solar energy not completely useable, and on-grid energy cannot be reduced at capacity. Thus, how to control user admission to improve solar energy utilization and to reduce on-grid energy consumption is a great challenge. Motivated by this, we first model the energy flow behavior by using stochastic queue model, and dynamic energy characteristics are analyzed mathematically. Then, fuzzy logic based admission control algorithm is proposed, which comprehensively considers admission judgment parameters, e.g., transmission rate, bandwidth, energy state of BSs. Moreover, the index of solar energy utilization balancing is proposed to improve the balance of energy utilization among different BSs in the proposed algorithm. Finally, simulation results demonstrate that the proposed algorithm performs excellently in improving solar energy utilization and reducing on-grid energy consumption of the HybE-Net.