Journal of the Korean Solar Energy Society (한국태양에너지학회 논문집)

The Korean Solar Energy Society (한국태양에너지학회)
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Analysis of Clear Sky Index Defined by Various Ways Using Solar Resource Map Based on Chollian Satellite Imagery

천리안 위성 영상 기반 태양자원지도를 활용한 다양한 정의에서의 청천지수 특성 분석

  • Kim, Chang Ki (New and Renewable Energy Resource & Policy Center, Korea Institute of Energy Research) ;
  • Kim, Hyun-Goo (New and Renewable Energy Resource & Policy Center, Korea Institute of Energy Research) ;
  • Kang, Yong-Heack (New and Renewable Energy Resource & Policy Center, Korea Institute of Energy Research) ;
  • Yun, Chang-Yeol (New and Renewable Energy Resource & Policy Center, Korea Institute of Energy Research)
  • 김창기 (한국에너지기술연구원 신재생에너지자원.정책센터) ;
  • 김현구 (한국에너지기술연구원 신재생에너지자원.정책센터) ;
  • 강용혁 (한국에너지기술연구원 신재생에너지자원.정책센터) ;
  • 윤창열 (한국에너지기술연구원 신재생에너지자원.정책센터)
  • Received : 2019.06.03
  • Accepted : 2019.06.16
  • Published : 2019.06.30
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Abstract

Clear sky indices were estimated by various ways based on in-situ observation and satellite-derived solar irradiance. In principle, clear sky index defined by clear sky solar irradiance indicates the impacts of cloud on the incoming solar irradiance. However, clear sky index widely used in energy sciences is formulated by extraterrestrial irradiance, which implies the extinction of solar irradiance due to mainly aerosol, water vapor and clouds drops. This study examined the relative difference of clear sky indices and then major characteristics of clear sky irradiance when sky is clear are investigated. Clear sky is defined when clear sky index based on clear sky irradiance is higher than 0.9. In contrast, clear sky index defined by extraterrestrial irradiance is distributed between 0.4 and 0.8. When aerosol optical depth and air mass coefficient are relative larger, solar irradiance is lower due to enhanced extinction, which leads to the lower value of clear sky index defined by extraterrestrial irradiance.

Keywords

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Fig. 1 Solar resource map derived by UASIBS-KIER model with Chollian Satellite imagery from 2016 to 2017

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Fig. 2 Flowchart of data analysis

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Fig. 3 Relative Frequency of ktm (red bar) and kte (green bar) from January, 2016 to December, 2017

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Fig. 4 Scatter plot of global horizontal irradiance between in-situ observation and satellite derivation when ktm is higher than 0.9

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Fig. 5 Relative Frequency of kte when ktm is higher than 0.9 (sky is clear)

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Fig. 6 Relative Frequency of kte when ktm is higher than 0.9 (black bar ) and otherwise (grey bar)

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Fig. 7 Scatter plot of ktc and kd when ktm is higher than 0.9

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Fig. 8 Scatter plot of kd and cosθ when ktm is higher than 0.9

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Fig. 9 2-dimensional histogram of kd for aerosol optical depth and cosθ when ktm is higher than 0.9

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