• Journal of the Korean Solar Energy Society
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• v.37 no.6
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• pp.69-77
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• 2017

The amount of solar irradiation obtained by a photovoltaic (PV) solar panel is the major factor determining the power generated by a PV system, and the array tilt angle is critical for maximizing panel radiation acquisition. There are three types of PV systems based on the manner of setting the array tilt angle: fixed, semi-fixed, and tracking systems. A fixed system cannot respond to seasonal solar altitude angle changes, and therefore cannot absorb the maximum available solar radiation. The tracking system continually adjusts the tilt angle to absorb the maximum available radiation, but requires additional cost for equipment, installation, operation, and maintenance. The semi-fixed system is only adjusted periodically (usually seasonally) to obtain more energy than a fixed system at an overall cost that is less than a tracking system. To maximize semi-fixed system efficiency, determining the optimal tilt angle adjustment schedule are required. In this research, we conducted a simulation to derive an optimal operation schedule for a semi-fixed system in Seoul, Korea (latitude $37.5^{\circ}$). We implemented a solar radiation acquisition model and PV genereation model on MATLAB. The optimal operation schedule was derived by changing the number of tilt angle adjustments throughout a year using a Dynamic Algorithm. The results show that adjusting the tilt angle 4 times a year was the most appropriate. and then, generation amount of PV system increased 2.80% compared with the fixed system. This corresponds to 99% compared to daily adjustment model. This increase would be quite valid as the PV system installation area increased.

• Solar Energy
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• v.20 no.4
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• pp.31-43
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• 2000

A model house with a "Ondol" heating working with solar energy and supplied by circulation air was investigated both experimentally and theoretically, A calculation method was developed for interpreting the measured values and for comparing several variants, This calculation method together with the measurement result is presented in the following. The gain in energy of the collector(Trombe wall type with TWD) measured on a particularly selected winter day with plenty of radiation amounted to approximately 31 % of the total solar radiation.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.432-441
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• 2016

Solar energy is the ideal power choice for long-endurance stratospheric airships. The output performance of solar array on stratospheric airship is affected by several major factors: flying latitude, flight date, airship's attitude and the temperature of solar cell, but the research on the effect of these factors on output performance is rare. This paper establishes a new simplified analytical model with thermal effects to analyze the output performance of the solar array. This model consisting of the geometric model of stratospheric airship, solar radiation model and incident solar radiation model is developed using MATLAB computer program. Based on this model, the effects of the major factors on the output performance of the solar array are investigated expediently and easily. In the course of the research, the output power of solar array is calculated for five airship's latitudes of $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$, four special dates and different attitudes of five pitch angles and four yaw angles. The effect of these factors on output performance is discussed in detail. The results are helpful for solving the energy problem of the long endurance airship and planning the airline.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1383-1389
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• 2011

The current study focuses on the consistent analysis of heat transfer in multichannel volumetric solar receivers used for concentrating solar power. Changes in the properties of the absorbing material and channel dimensions are considered in an optical model based on the Monte Carlo ray-tracing method and in a one-dimensional heat transfer model that includes conduction, convection, and radiation. The optical model results show that most of the solar radiation energy is absorbed within a very small channel length of around 15 mm because of the large length-to-radius ratio. Classification of radiation losses reveals that at low absorptivity, increased reflection losses cause reduction of the receiver efficiency, notwithstanding the decrease in the emission loss. As the average temperature increases because of the large channel radius or small mass flow rate, both emission and reflection losses increase but the effect of emission losses prevails.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.492-497
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• 2011

The objective of this research is to study the variation of optimum slope angles of collectors for seven regions in Korea, which are Seoul, Gangneung, Daejeon, Daegu, Gwangju, Busan and Jeju. The results for 2000~2007 are analyzed to sec if adjustment of slope angles is necessary each year to receive maximum solar radiation. For an azimuth fixed solar collector, solar radiation of yearly optimized slope angle during May~Sept.(summer), Nov.~Mar.(winter) and the whole year are greater than the fixed slope angle by 0.03%, 0.02%, and 0.04%, respectively. For an azimuth tracking solar collector, solar radiation of yearly optimized slope angle during May~Sept.(slimmer), Nov.-Mar.(winter) and the whole year are greater than the fixed slope angle by 0.03%, 0.07%, and 0.04% respectively. It is unnecessary to adjust slope angles each year for both azimuth fixed and tracking collectors, since the gains are insignificant. Solar radiation of the azimuth tracking solar collector during May~Sept., Nov.~Mar. and the whole year are greater by 14.7%, 16.0%, and 19.2% than the azimuth fixed solar collector.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.238-244
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• 2008

A numerical and experimental studies are carried out to investigate the heat transfer characteristics of 5kWth dish-type solar air receiver. Measured solar radiation and temperatures at several different locations are used as boundary conditions for numerical simulation. Many parameters' effects (reflectivity of the reflector, the thermal conductivity of the receiver body, transmissivity of the quartz window, etc.) on the thermal performance are investigated. Discrete Transfer Method is used to calculate the radiation heat exchange in the receiver. A heat transfer model is developed and the rate of radiation, convection and conduction heat transfer are calculated. Using the numerical model, the heat transfer characteristics of volumetric air receiver for dish-type solar thermal systems are known and the thermal performance of the receiver can be estimated.

• Journal of Environmental Impact Assessment
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• v.21 no.1
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• pp.219-227
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• 2012

Daily solar radiation is essential for water resources planning and environmental impact assessment. However, radiation data is not commonly available in Korea other than in big cities, and there has been no direct measurement for rural areas where water resources planning and environmental impact assessment is usually most needed. In general, missing radiation data is estimated from nearby regional stations within a certain distance, and this study compared two dominant methods (modified Angstrom equation and transmittance interpolation method) at six stations in Nakdong River watershed area. Two methods shows a similar level of accuracy but the transmittance interpolation method is likely to be superior in that there is no need for any measurement element since the modified Angstrom equation require the sunshine hour measurement. This study will contribute to improve water resource and water quality management in Nakdong River watershed.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.5
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• pp.545-554
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• 1999

We would like to develop a short-term model to predict the time-related concentration of ozone whose reaction mechanism is complex. The paper targets Seoul where an ozone alert system has recently been employed. In order to develop a short-term prediction model for ozone, we suggested the Ozone Peak Indicator(OPI), an equivalent of the potential daily maximum ozone concentration, with precursors being the only limiting factor, and we calculated the Ozone Peak Indicarot as OPI={$rac{(O_3)_{max}cdot(H_{eH})_{max}(Rad)_{max}$ to preclude the influence of mixing height and solar radiation on the daily maximum ozone concentration. The OPI on the day of the prediction is to be calcultated by using the relation between OPI and the initial value of precursors. The basic prediction formula for time-related ozone concentration was established as $O_3(1)={(OPI)cdot Rad(t-2)H_{eH}}$, using the OPI, solar radiation two hours before prediction and mixing height. We developed, along with the basic formula for predicting photochemical oxidants, "SEOM"(Seoul Empirical Oxidants Model), a Fortran program that helps predict solar radiation and mixing height needed in the prediction of ozone pollution. When this model was applied to Seoul and an analysis of the correlation between the observed and the predicted ozone concentrations was made through SEOM, there appeared a very high correlation, with a coefficient of 0.815. SEOM can be described as a short-term prediction model for ozone concentration in large cities that takes into account the initial values of precursors, and changes in solar radiation and mixing height. SEOM can reflect the local characteristics of a particular and region can yield relatively good prediction results by a simple data input process.t process.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.2
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• pp.91-97
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• 2018

High-energy charged particles are comprised of galactic cosmic rays and solar energetic particles which are mainly originated from the supernova explosion, active galactic nuclei, and the Sun. These primary charged particles which have sufficient energy to penetrate the Earth's magnetic field collide with the Earth's upper atmosphere, that is $N_2$ and $O_2$, and create secondary particles and ionizing radiation. The ionizing radiation can be measured at commercial flight altitude. So it is recommended to manage radiation dose of aircrew as workers under radiation environment to protect their health and safety. However, it is hard to deploy radiation measurement instrument to commercial aircrafts and monitor radiation dose continuously. So the numerical model calculation is performed to assess radiation exposure at flight altitude. In this paper, we present comparison result between measurement data recorded on several flights and estimation data calculated using model and examine the characteristics of the radiation environment in the atmosphere.

• Solar Energy
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• v.20 no.3
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• pp.21-30
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• 2000

It is necessary to estimate the regression coefficients in order to predict the monthly mean daily global radiation on a horizontal surface. Therefore many different equations have proposed to evaluate them for certain areas. In this work, a new correlation has been made to predict the solar radiation for any area over Korea by estimating the regression coefficients taking into account percentage of possible sunshine, and cloud cover. Particularly, the multiple linear regression model proposed shows reliable results for estimating the global radiation with average deviation of -1 to 3 % from the measured values.