• 한국태양에너지학회 논문집
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• 제39권4호
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• pp.11-24
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• 2019

The total solar irradiation on horizontal surfaces is separated into the beam and diffuses components. Although horizontal global irradiance is a commonly measured parameter for many sites, horizontal diffuse irradiance is not so readily obtainable. For such sites that measure global irradiation alone, a simple but reasonably accurate method is required to estimate diffuse irradiance from its global counterpart. This study investigates the applicability of correlation coefficients models correlating hourly diffuse and beam fraction and hourly clearness index in Daejeon. The three diffuse to global correlation coefficients models (Orgill and Holland model, CIBSE Guide J model, and Erbs et al. model) are selected and the three modified beam to global correlation coefficients models are generated. MBE, RMSE, r-squared of Daejeon and Daejeon boundary site-fitted models are compared with the case of original coefficients. The comparison result shows that the beam and diffuse to global solar irradiation correlation coefficients models with boundary site-fitted coefficients are best suitable for Daejeon. Further researches will be conducted to find the boundary site-fitting method using measured data of other cities and correlation coefficients models using solar altitude, cloud cover, and sunshine duration.

• 한국정밀공학회지
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• 제21권6호
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• pp.94-101
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• 2004

From the Beckmann's reflection model of wave incident, reflected light from a surface is known to have not only specular but also diffuse components. The specular component dominant a surface for a mirror-like surface is distributed on the almost the same area as the spot on the surface, but the diffuse component region dominant f3r a rough surface spreads scattered on the larger areas than the spot. Therefore, statistic parameters from the scattered light distribution are more meaningful in the diffuse region, while the magnitude of rather meaning in the specular region. In usual, there need two sensors to acquire two kinds of information: Photo-detector for light intensity magnitude and image sensor for light intensity distribution. But dual sensor scheme requires a beam splitter usually to feed light to each sensor, and moreover there is not a combination rule to relieve the different sensor characteristics. In this study a new method is proposed for acquisition of the dual information using only an image sensor. Specular region is established on an image area being distinguished from a diffuse component, and laser power is adjusted so that no pixel of the image sensor in the specular region is saturated. Simulation based on the light reflection theory and the experimental results are quite well matched, and thus the proposed method was proved to be very useful for mirror-like surface measurement.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.8-12
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• 2009

The Knowledge of the solar radiation components are essential for modeling many solar energy systems. This is particularly the case for applications that concentrate the incident energy to attain high thermodynamic efficiency achievable only at the higher temperatures. In order to estimate the performance of concentrating thermal systems, it is necessary to know the intensity of the beam radiation, as only this component can be concentrated. The Korea Institute of Energy Research(KIER) has began collecting solar radiation component data since August, 2002. KIER's component data will be extensively used by concentrating system users or designers as well as by research institutes. The Result of analysis shows that the annual-average daily diffuse radiation on the horizontal surface is $1,458cal/m^2$ and daily direct radiation on the horizontal surface is $1,632cal/m^2$ for all over the 16 areas in Korea.

• 한국태양에너지학회 논문집
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• 제29권3호
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• pp.12-18
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• 2009

The Knowledge of the solar radiation components are essential for modeling many solar energy systems. This is particularly the case for applications that concentrate the incident energy to attain high thermodynamic efficiency achievable only at the higher temperatures. In order to estimate the performance of concentrating thermal systems, it is necessary to know the intensity of the beam radiation, as only this component can be concentrated. The Korea Institute of Energy Research(KIER) has began collecting solar radiation component data since January, 2002. KIER's component data will be extensively used by concentrating system users or designers as well as by research institutes. The theoretical analysis of solar radiation as a component has compared with the experimental data obtained by the KIER station. The Result of simulation analysis shows that the annual-average daily diffuse radiation on the horizontal surface is $1,457cal/m^2$ and daily direct radiation on the horizontal surface is $1,632cal/m^2$ for all over the 16 areas in Korea.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.397-401
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• 1995

ESPI(Electronic Speckle Pattern Interfermetry) is an optical technique to measure surface deforamtion of engineering components and materials in industrial ares. This optical method is capable of providing full-field results with high spatial resolution, high speed and is the non-contact technique. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The contouring method by modified dual-beam speckle pattern interferometry is proposed. We introduce a shift of the illumination beams through optical fiber in order to obtain the contour fringe patterns. The speckle pattern correlation technique is suitable for providing measurement range from millimeters to several centimeters. The complete geometric analysis of the contoretical and experimental results are obtained.

• 대기
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• 제21권2호
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• pp.131-142
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• 2011

Spectral solar irradiances were observed using a visible and UV Multi-Filter Rotating Shadowband Radiometer on the rooftop of the Science Building at Yonsei University, Seoul ($37.57^{\circ}N$, $126.98^{\circ}E$, 86 m) during one year period in 2006. 1-min measurements of global(total) and diffuse solar irradiances over the solar zenith angle (SZA) ranges from $20^{\circ}$ to $70^{\circ}$ were used to examine the effects of clouds and total optical depth (TOD) on enhancing four solar irradiance components (broadband 395-955 nm, UV channel 304.5 nm, visible channel 495.2 nm, and infrared channel 869.2 nm) together with the sky camera images for the assessment of cloud conditions at the time of each measurement. The obtained clear-sky irradiance measurements were used for empirical model of clear-sky irradiance with the cosine of the solar zenith angle (SZA) as an independent variable. These developed models produce continuous estimates of global and diffuse solar irradiances for clear sky. Then, the clear-sky irradiances are used to estimate the effects of clouds and TOD on the enhancement of surface solar irradiance as a difference between the measured and the estimated clear-sky values. It was found that the enhancements occur at TODs less than 1.0 (i.e. transmissivity greater than 37%) when solar disk was not obscured or obscured by optically thin clouds. Although the TOD is less than 1.0, the probability of the occurrence for the enhancements shows 50~65% depending on four different solar radiation components with the low UV irradiance. The cumulus types such as stratoculmus and altoculumus were found to produce localized enhancement of broadband global solar irradiance of up to 36.0% at TOD of 0.43 under overcast skies (cloud cover 90%) when direct solar beam was unobstructed through the broken clouds. However, those same type clouds were found to attenuate up to 80% of the incoming global solar irradiance at TOD of about 7.0. The maximum global UV enhancement was only 3.8% which is much lower than those of other three solar components because of the light scattering efficiency of cloud drops. It was shown that the most of the enhancements occurred under cloud cover from 40 to 90%. The broadband global enhancement greater than 20% occurred for SZAs ranging from 28 to $62^{\circ}$. The broadband diffuse irradiance has been increased up to 467.8% (TOD 0.34) by clouds. In the case of channel 869.0 nm, the maximum diffuse enhancement was 609.5%. Thus, it is required to measure irradiance for various cloud conditions in order to obtain climatological values, to trace the differences among cloud types, and to eventually estimate the influence on solar irradiance by cloud characteristics.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.239-244
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• 1998

ESP(Electronic Speckle Pattern Interferometry) is an optical technique to measure deforamtion of engineering components and materials in industrial areas. ESPI, a non-contact and non-destructive measuring method, is capable of providing full-field results with high spatial resolution and high speed. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The electronic speckle contouring is suitable for providing measurement range from millimeters to several centimeters. In this study, we introduce the contouring method by modified dual-beam speckle pattern interferometer and a shift of the two illumination beams through optical fiber in order to obtain the contour fringe patterns. Before the experiments, we performed the geometric analysis for dual-beam-shifted ESPI contouring. And by this geometric analysis, we performed the electronic speckle contouring experiment. We used 4-frame phase shifting method with PZT for quantitative analysis of contour fringes. Finally, we showed good agreements between the geometric analysis and experimental results.

• 한국태양에너지학회 논문집
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• 제23권3호
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• pp.23-28
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• 2003

The purpose of this study is to procure basic data to be used for solar power plant and concentrating collector designs. Site elevation is one of the major factors which influences the incoming insolation to the earth surface. Because the nonpermanent gases such as ozone, water vapor are unmixed components of the atmosphere and their concentrations are the function of height, the site elevation effects the relative proportion of the atmospheric constituents. We have measured solar radiation on Jiri Mt. (1,400m) and in Gurye area(115m) at the near same latitude. These values were then compared to obtain their characteristics and to investigate the potential for the solar utilization for both high and low elevated areas. From the experimental results, we concluded that 1) Daily mean horizontal global radiation and normal beam radiation on Mt. Jiri are 9.5%, and 35.3% higher than Gurye area respectively for a clear day. 2) A significant difference in atmospheric clearness index is observed between Mt. Jiri and Gurye areas.

• 생물환경조절학회지
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• 제5권2호
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• pp.215-235
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• 1996

본 연구에서 수행한 Model 시뮬레이션에 의한 열환경 분석 기법은 지역별로 다양한 기상여건 하에서 대상온실의 난방 및 냉방부하를 보다 합리적으로 예측할 수 있을 뿐만 아니라 냉방이나 난방용 시스템의 결정을 비롯한 난방대책을 수립하고, 에너지 이용 전략의 수립이나 계절적인 작부계획 수립, 온실산업용 적지선정 등에 유익하게 활용될 수 있을 것이라 판단된다. 본 연구에서는 온실의 적극적인 환경조절 유형을 난방과 냉방의 두 가지로 대별하고, 난방 소요열량 산정을 비롯하여 야간의 보온 커튼효과, Heating Degree-Hour 산정 등 난방과 관련된 시뮬레이션은 동적 모형을 이용하여 시간별, 일별 및 월별로 검토하였으며, 환기를 비롯한 차광, 증발냉각시스템의 효과 분석은 정적모형을 이용하여 검토하였다. 특히 하절기 지하수와 같은 저온수를 직접 이용하거나 Heat Pump를 통하여 확보될 수 있는 저온수를 이용하여 온실의 피복면에 살수함으로서 확보할 수 있는 온실냉방효과를 검토하는 데는 1.2m$\times$2.4m 크기의 모형온실을 제작하여 기초실험을 수행함으로서 동절기의 수막시스템의 보온효과와 마찬가지로 하절기 냉방 효과를 거둘 수 있다는 가능성을 확인하였다. 본 연구에 활용된 온실의 수치 환경모형 중 난방관련 시뮬레이션용 동적 수치모형은 소기의 목적을 달성하는데 충분히 응용될 수 있는 이론모형이다. 이 이론모형이 범용성이 높은 것은 온실 내ㆍ외의 미기상 변화, 특히 난방이나 냉방이 본격적으로 요구되는 기간동안에 온도, 습도, 일사, 풍속 등의 미기상 인자들을 면밀하게 관찰하여 실측된 자료를 바탕으로 개발되었고, 다양한 자료에 의해 충분히 검정되었기 때문이다. 본 연구에서는 경남 진주지역의 어느 특정 기간(1987년)의 시간별 기상자료를 중심으로 온실의 열적 환경변화에 대한 수치모형 시뮬레이션을 실시하였으며, 아직 수치모형에 의한 시뮬레이션이 불가능한 일부 냉방효과를 검토하는 데는 모형 실험을 실시하였으며, 그 결과를 요약하면 다음과 같다. 1. 주간과 야간의 설정온도를 달리하고 다단계 변온조절방식으로 시뮬레이션을 행한 결과 난방 소요열량은 난방 설정온도에 따라 현저한 차이를 보였다. 특히 주간 설정온도에 비하여 야간 설정온도가 난방 소요열량에 예민하게 영향을 미치므로 야간의 설정온도 결정에 신중을 기해야 할 것으로 판단된다. 2. 기존의 Heating Degree-Hour 자료는 평균 외기온을 중심으로 임의의 설정온도에 대하여 산정된 값이므로 난방 소요열량에 대한 상대적인 비교수단은 되나 고려되는 기상인자의 제한과 설정온도의 임의성 때문에 실용성이 부족하다. 따라서 본 연구에서 제시된 것처럼 온실 주변의 제반 미기상 인자나 경계조건이 반영됨은 물론 작물의 생육상태 및 구체적인 설정온도까지도 고려하는 동적 수치모형으로 시시각각으로 예측된 실내기온을 중심으로 재배기간 동안의 난방열량을 적산함이 합리적이라 판단된다. 기존의 MDH 자료로 난방 설계를 할 경우에는 지나치게 과잉설계 될 가능성이 있다. 3. 산정된 난방 소요열량은 물론 커튼의 보온성능도 월별 기상여건에 따라 현저한 차이를 보이며, 시뮬레이션에 이용된 커튼의 경우 높은 보온효과를 보임으로서 년 평균 50% 이상의 난방 에너지를 절감할 수 있으며, 동절기 3-4개월의 집중 난방기에 에너지가 크게 절감됨을 발견할 수 있다. 4. 고온기 환기성능은 온실의 구조, 기상조건, 작물의 생육상태 등에 따라 다소의 차이가 있으나 환기율에 의해 크게 좌우되며, 시뮬레이션에 이용된 두 가지 농가보급형 온실 모두 환기율의 증가에 따른 실내기온의 강하 효과가 환기율이 1회/min 정도를 넘어서면서 급격히 둔화되는 현상을 보인다. 이는 기존에 권장되고 있는 적정 환기율인 1회/min 전후의 환기 시스템을 갖추는 것이 합리적임을 확인해 준다. 5. 작물이 성숙된 유리온실에서 외기의 상대습도가 50%인 쾌청한 주간동안 연속적으로 1회/min로 환기를 시킬 경우 실내기온 36.5$^{\circ}C$의 대조구에 비한 온도강하는 50% 차광만 했을 시 2.6$^{\circ}C$이고 효율 80%의 Pad ＆ Fan 시스템만 작동시 6.1$^{\circ}C$ 정도이며, 차광과 냉각시스템을 동시에 작동시는 약 8.6$^{\circ}C$로서 외기온보다 3.3$^{\circ}C$가 낮은 28$^{\circ}C$까지 실내온도를 낮출 수 있으나, 동일 조건하에서 외기의 상대습도가 80%로 높은 경우에는 Pad ＆ Fan시스템에 의한 온도강하가 2.4$^{\circ}C$에 불과하여 50% 차광하에서도 외기온 이하로 실내온도를 낮출 수 없음을 알 수 있다. 6. 하절기 3개월(6/1-8/31)동안 Pad ＆ Fan 시스템의 냉방효과($\Delta$T)는 설정된 작동 온도에 따라 다소 차이를 보일 것으로 예상되나 본 시뮬레이션에서 설정한 시스템의 작동 온도 27$^{\circ}C$에서 상대습도와의 상관관계는 대략 다음과 같았다: $\Delta$T= -0.077RH＋7.7 7. 전형적인 하절기 주간기상 하에서 경시적 냉방효과를 분석한 결과 환기만으로는 실내기온을 외기온 보다 5$^{\circ}C$ 높게 유지하는 정도가 고작이고, 차광이나 증발식 냉방시스템 만으로는 작물이 성숙한 단계에서조차도 외기온 이하로 떨어뜨리기가 어려우나 차광과 아울러 증발식 냉방을 병행할 경우에는 작물상태에 따라 다소 차이는 있지만 실내기온을 외기온보다 2.0-2.3$^{\circ}C$ 낮게 유지할 수 있음을 발견할 수 있다. 8. 일사가 차단된 27.5-28.5$^{\circ}C$의 외기온하에서 6.5-8.5$^{\circ}C$의 냉수를 온실 바닥면적 1$m^2$당 1.3 liter/min의 유량으로 온실표면에 살수했을 때 실내기온을 외기온보다 1$0^{\circ}C$ 낮은 16.5-18.$0^{\circ}C$ 정도로 낮출 수 있었다. 앞으로 살수 수온(T$_{w}$ )이나 외기온(T$_{o}$ ) 뿐만아니라 살수율(Q)에 따라 온실기온 (T$_{g}$ )에 미치는 상관 관계 T$_{g}$ = f(T$_{w}$ , Q, T$_{o}$ )를 구명하여 지하수 자체 또는 Heat Pump를 이용한 지하수온 이하의 냉수로 온실냉방의 가능성을 구명하는 것이 앞으로의 과제이다.