• Research Article

    Analysis of the Impact of Power Loss by Snail Trail Degradation in Solar Power Plant

    태양광 발전소의 Snail trail 열화 현상과 출력 손실의 영향성 분석

    Oh Wonwook ・ Kim Daesung ・ Jeon Seonggeun ・ Yoon Ayoung ・ Kim Namseung ・ Kim Sangsoo ・ Seo Kun Won ・ Choi hoonjoo

    오원욱・김대성・전성근・윤아영・김남승・김상수・서근원・최훈주

    The snail trail is a common degradation phenomenon that is observed in solar power plants. Although the occurrence of cosmetic problems has ... + READ MORE
    The snail trail is a common degradation phenomenon that is observed in solar power plants. Although the occurrence of cosmetic problems has been reported in previous studies, the contribution of these problems to the actual power loss is negligible. However, the cracking of the solar cell induces a loss in the output. We analyzed the results of the thorough investigation of a 95 kWp solar power plant that was operated in the field for 5 years. The snail trail phenomenon was observed in a specific module using current-voltage measurement, electroluminescence analysis, and visual inspection. We evaluated the impact of the loss in the generated power via image extraction. - COLLAPSE
    December 2020
  • Research Article

    Performance Analysis of Photovoltaic System using Proposed Assessment Method: An Inquiry on Output Energy Analysis Depending on Distance
    Shin Min-Su・Kwon Oh-Hyun・Lee Sang-Hyuk・Lee Kyung-Soo
    The losses in grid-connected photovoltaic (PV) power generation systems were calculated using the monitoring data that were collected in 2018-2019 from the ... + READ MORE
    The losses in grid-connected photovoltaic (PV) power generation systems were calculated using the monitoring data that were collected in 2018-2019 from the path between the input and output energy. Thus, the various loss factors were identified. The performances of seven PV power plants in a specific area of Korea were evaluated by developing a quantitative performance evaluation model based on the loss factors. The meteorological environment data were considered vital for the accurate quantification of the input energy in this model. We performed quantitative analyses of the performance deviations and the errors, based on the distances between the weather-monitoring locations and the PV power plants. The proposed analytical method employed two sets of meteorological data that were obtained from the monitoring stations at different locations. Furthermore, one set of interpolated data was employed to quantify the deviations between the expected power and the actual power. The expected power was estimated using the proposed assessment method, while the actual power was measured at the seven PV power plants that were 1.2-17.1 [km] away from the location of the meteorological data measurement. When the distance between the input energy and the plant was minimum (1.2 [km]), the root mean square error (RMSE) and the mean absolute error (MAE) of the output energy were 0.0633 [kWh/kWP/h] and 0.0396 [kWh/kWP/h], respectively. When the distance between the input energy and the plant was maximum (17.1 [km]), the RMSE and MAE of the output energy were 0.1202 [kWh/kWP/h] and 0.0854 [kWh/kWP/h], respectively. Therefore, the error increased with the increase in the distance between the input energy and the PV power plants. It was interesting to note that the errors remained high for two of the seven sites, irrespective of the distance from the input energy. These sites were investigated via site inspections; thus, the errors were ascribed to factors such as module shading and incorrect system installation. - COLLAPSE
    December 2020
  • Research Article

    Voltage Rise Mitigation and Test Using the Reactive Power Compensator in LV Distribution Networks

    무효전력 보상기를 이용한 저압 배전계통 전압 상승 억제 및 실증

    Kim Young Roc ・ Cha Han Ju

    김영록・차한주

    The high penetration level of the generated photovoltaic (PV) power generation in low voltage (LV) networks induces the issue of voltage rise ... + READ MORE
    The high penetration level of the generated photovoltaic (PV) power generation in low voltage (LV) networks induces the issue of voltage rise, particularly at the end of the feeders. Several solutions such as grid reinforcement, transformer tap change, demand-side management, active power curtailment, and the use of reactive power control methods have been proposed to address this issue. However, the practicability of these solutions is limited owing to high costs, low efficiencies and the conflicts of interest between network operator and the owners of solar farms. This paper proposed the use of a reactive power compensator (RPC) to mitigate the dual issues of voltage rise and voltage drop. The voltage rise is caused by the distributed generation systems while the voltage drop is caused by the heavy loads at the end of the feeder of the weak LV distribution networks. The RPC was utilized to inject the lagging or leading reactive current during the voltage drop or voltage rise condition. The proposed RPC was developed as a part of the Kepco Open R&D project. The aim of this project is to investigate the techniques to mitigate the issues for the voltage rise and drop in the distribution networks, without either changing the service transformer tap or installing an additional distribution line and service transformer. The performance of the proposed RPC was verified via simulation and experiments. - COLLAPSE
    December 2020
  • Research Article

    Wind Load Analysis of the Heliostat Field in Northern Daegu for Concentrating Solar Power

    북대구 집광형 태양열 발전소 헬리오스탯 필드의 풍하중 분석

    Kim Hyun-Goo ・ Kang Yong-Heack ・ Jeon Wan-Ho

    김현구・강용혁・전완호

    The concentration performance of a heliostat field consisting of hundreds to thousands of reflectors allows for a deformation-based focus deviation of only ... + READ MORE
    The concentration performance of a heliostat field consisting of hundreds to thousands of reflectors allows for a deformation-based focus deviation of only 3 mrad or less. The most problematic aspect is the wind load; hence, in this study, the extreme wind speed condition was analyzed. Preceding studies such as field experiments, wind tunnel tests, or Reynolds-averaged Navier–Stokes (RANS) simulations were limited to a single heliostat or a single row, such that the characteristics of vortex shedding from the heliostat field could not be practically understood. In this study, the wind flow over the heliostat field in northern Daegu for Concentrating Solar Power (CSP), consisting of 450 reflectors, was analyzed using large eddy simulations with 33 million cells, in order to identify the characteristics of vortex shedding. In the heliostat field, the windward front and the left and right sides received the peak wind load, and the characteristics of vortex shedding were different depending on the position in the field. A fast Fourier transform analysis of the time-series wind pressure confirmed that the vortex shedding frequency ranged from 0.09 to 0.32 s-1; it was determined that the vortex shedding from the upper and lower sides dominated that of the left and right sides of the heliostat. After predicting the wind load by Large Eddy Simulations (LES), structural analysis was performed to calculate the maximum displacement of the reflector. It was confirmed that the maximum displacement angle of the heliostat at the windward front, which receives the largest wind load at extreme wind events, satisfies the performance requirement of 1 mrad or less. - COLLAPSE
    December 2020
  • Research Article

    Observational Study of Nudging Occupants’ Energy Saving Behavior

    정보 제공을 통한 건물에너지 절약 행동 유발에 관한 실험

    Kim Sung-Su ・ Kim So-Yeon ・ Kim Yong-Hun ・ Lim Jongyeon

    김성수・김소연・김용훈・임종연

    As a measure to reduce energy consumption in buildings, the high performance of the outer skin and the high efficiency of the ... + READ MORE
    As a measure to reduce energy consumption in buildings, the high performance of the outer skin and the high efficiency of the facility system are attracting attention to induce changes in the behavior of the inmates. A methodology in the field of behavioral science, so-called nudge, is being considered as an energy-saving measure. However, most of the existing empirical experiments are aimed at housing, which can be attributed to the fact that individual energy conservation acts as an economic incentive, making it easier to achieve its effect. This study reports the results of empirical experiments on energy saving in public spaces by nuts, which, so far, includes few examples. The experiment was conducted on 33 people in a university laboratory. The existing energy consumption patterns were measured for one month; only a few workers were regularly informed of the energy usage for two months, and the resulting changes in the energy consumption patterns were measured. The provision of energy consumption information has shown to increase the probability of energy saving, and it is particularly effective in promoting the energy-saving behavior of those willing to save energy. - COLLAPSE
    December 2020
  • Research Article

    Development of Energy Prediction Model for Residential Buildings through Statistical Analysis

    통계분석을 통한 주거용 건물의 주택유형별 에너지 예측모델 개발

    Kim Jiwon ・ Kwak Younghoon ・ Huh Jung-Ho

    김지원・곽영훈・허정호

    Reducing building energy is necessary to realize the post-2020 national greenhouse gas reduction target (37% reduction from the BAU). Among them, residential ... + READ MORE
    Reducing building energy is necessary to realize the post-2020 national greenhouse gas reduction target (37% reduction from the BAU). Among them, residential buildings account for about 64% of buildings and must seek ways to save energy. To achieve this, it is necessary to analyze the factors impacting energy consumption. Therefore, this study conducted a statistical analysis to build an energy prediction model for residential buildings by utilizing the “Furniture Energy Permanent Sample Survey” microdata provided by the Korea Energy Economics Institute. Energy consumption, a dependent variable, was a summed up value of annual electricity, city gas, and district heating consumption, and the factors influencing energy consumption were selected as variables, considering prior research and multiple recovery analysis results of microdata. Subsequently, an analysis of variance was performed to verify the significance of the regression equation. Insignificant variables were eliminated by the statistical analysis results, and regression models were presented for the remaining variables. Therefore, the regression model derived from this study is expected to be the basis for the prediction and reduction of energy consumption, in the future, for residential household characteristics. - COLLAPSE
    December 2020
  • Research Article

    Performance of a Photovoltaic/Concentrated Solar Power Hybrid System Based on the Splitting of the Solar Spectrum in Korea

    국내 주요지역에서 태양복사 스펙트럼 분리를 이용한 태양광/태양열 하이브리드 발전시스템의 성능

    니콜라스 리우・이현진

    Liew, J. Y. Nicholas ・ Lee Hyun-Jin

    Because photovoltaic (PV) cells respond only to wavelengths above the bandgap energy, only part of the solar spectrum incident on the surface ... + READ MORE
    Because photovoltaic (PV) cells respond only to wavelengths above the bandgap energy, only part of the solar spectrum incident on the surface of a PV is utilized. In this study, the spectrum splitting technique is used to exploit the entire solar spectrum. A wavelength-selective filter (WSF) is coated on the surface of PV cells, so the PV cell can absorb only the useful solar spectrum transmitted by the WSF. On the other hand, the solar spectrum reflected by the WSF is concentrated on thermal receivers for steam power generation in the concentrated solar power (CSP) system. We analyze the power performance of the PV/CSP hybrid using the WSF in various regions of South Korea. - COLLAPSE
    December 2020
  • Research Article

    Effect of Occupants’ Window Opening Behavior and Annual Ventilation Rates in Residential Building

    재실자의 창문개방행태에 따른 자연환기량 효과 분석

    Yoo Jihyun ・ Cho Ga Young

    유지현・조가영

    Seoul intends to realize zero-energy buildings through the “Green New Deal,” which aims to transform buildings that account for 68.2% of ... + READ MORE
    Seoul intends to realize zero-energy buildings through the “Green New Deal,” which aims to transform buildings that account for 68.2% of greenhouse gas emissions into green buildings with high energy efficiency. For this purpose, a passive method of high airtightness and high insulation of the building is also important, but this may cause health problems such as chronic respiratory diseases and asthma in occupants in terms of indoor air quality. In addition, according to the World Health Organization (WHO) report, the risk of infection to others has soared to 40% as indoor and outdoor air is not circulated in the corona virus (COVID-19). In contrast, even with ventilation of 0.3 ACH (air change rate), the risk of infection fell to the 1/20th level. Therefore, balancing ventilation, which not only affects indoor temperature but also indoor air quality, is the most important aspect of promoting zero-energy buildings. Therefore, the correlation between the window opening behavior of occupants, the most common source of ventilation, and the external environment was analyzed. The amount of natural ventilation with the window opening behavior was analyzed by the carbon dioxide decay method; further, the ACH value of residential buildings was determined considering the physical condition of each residential building. - COLLAPSE
    December 2020
  • Research Article

    On-site Measurement Method for Smart Skin Performance

    스마트 스킨 성능 측정을 위한 현장 측정 방법 개발을 위한 기초 연구

    Kim Seok-Hyun ・ Cho Soo

    김석현・조수

    Various performance measurement methods have been proposed to improve the performance of fit building methods. The measurement of the performance of a ... + READ MORE
    Various performance measurement methods have been proposed to improve the performance of fit building methods. The measurement of the performance of a smart skin, which adjusts the indoor environment in response to various stimuli, requires the measurement of the performance depending on the shape of the smart skin and the constituent material. Because the smart skin can adjust the amount of solar radiation transmitted from outdoors to indoors, it is necessary to measure the solar radiation transmission performance along the incident angle of the sun and the movement path of the sun. Therefore, it is necessary to develop an on-site measurement method that can measure the solar radiation acquisition performance based on the location and shape of the smart skin. In this study, we determine the solar radiation acquisition performance of the smart skin through the difference in the solar radiation measured indoor and outdoor using a configuration and an on-site measurement method. It is necessary to research and develop a field measurement method that can measure the performance of solar radiation acquisition according to the shape of the smart skin. - COLLAPSE
    December 2020
  • Research Article

    Spatial and Temporal Downscaling of Solar Radiation Using Statistical Techniques

    통계적 기법을 이용한 일사량의 공간 및 시간적 상세화

    Jung A hyun ・ Lee Dong-Hyun ・ Kim Jin-Young ・ Kim Chang Ki ・ Kim Hyun-Goo ・ Lee Yung-Seop

    정아현・이동현・김진영・김창기・김현구・이영섭

    We evaluated the forecast performance of solar radiation on the Korean Peninsula from the solar radiation data provided by the UASIBS-KIER model ... + READ MORE
    We evaluated the forecast performance of solar radiation on the Korean Peninsula from the solar radiation data provided by the UASIBS-KIER model of KIER with the solar radiation forecast data generated by the GFS model of the NCEP. In this study, the spatial and temporal downscaling of the GFS model, a cumulative solar radiation forecast model per 3 hours units, was conducted to measure forecast performance. First, in the case of spatial downscaling, K-means clustering of solar radiation values corresponding to all latitude and longitude values of the Korean Peninsula was performed, and seven clusters were formed. Second, in the case of temporal downscaling, the cumulative solar radiation forecast value over 3 h was converted to the cumulative solar radiation value over 1 h. To measure the downscaling performance, the downscaling results of the cumulative forecast over 1 h of the GFS model were compared with the observed solar radiation values of the UASIBS-KIER model. We performed downscaling by using the same average ratio as the cumulative value over 3 h. In addition, we performed downscaling by using the correlation between the cumulative value over 1 h by the UASIBS-KIER model. Based on the rRMSE and rMAE, the use of the correlation was found to be more efficient that the use of the same average ratio. - COLLAPSE
    December 2020
  • Research Article

    Construction and Evaluation of Empirical Model for Estimating UV Erythemal Irradiance using Global Horizontal Irradiance in South Korea

    전천일사를 이용한 남한 지역 홍반자외선 추정 경험 모델 구성 및 평가

    Kim Jaemin ・ Lee Yun Gon ・ Kim Hyun-Goo

    김재민・이윤곤・김현구

    Ultraviolet (UV; 100~400 nm) radiation, which is a short-wavelength part of the solar spectrum, has harmful effects on the human body ... + READ MORE
    Ultraviolet (UV; 100~400 nm) radiation, which is a short-wavelength part of the solar spectrum, has harmful effects on the human body, such as skin aging, sunburn, and skin cancer. Because overexposure to UV causes erythema in human skin, the UV erythemal irradiance (UVER) is provided to people as an index of the risks of UV irradiation. In this study, statistical empirical models for estimating surface UVER were developed and evaluated at Gangneung, Pohang, Mokpo, and Gosan sites in South Korea, where UVER and global horizontal irradiance (GHI) observation data have been collected for a long period. For the establishment of an empirical model, the clearness index of the GHI (KT), total column ozone, and solar zenith angle were used as independent variables. The underestimations of the empirical models were improved by grouping the dataset with KT. The improved models exhibited an average R2 of 90% at the four sites during the validation period. The atmospheric transmittance of the UVER was reconstructed using the empirical model at the GHI observation network during past 5 year data in South Korea, and the monthly variation showed seasonality with high values in May–August and low values in December–January. - COLLAPSE
    December 2020
  • Research Article

    Characteristics of Semiconductor Device and Multiplexer Control Method for Photovoltaic Panel Fault Diagnosis

    태양광 패널 고장 진단기기를 위한 소자 특성 및 Mux 회로 제어 방법에 대한 연구

    Seon Yong-Geun ・ Shin Hyun-Jin ・ Choi Eui-Seong ・ Shin Woo-Gyun ・ Ko Suk-Whan

    선용근・신현진・최의성・신우균・고석환

    In Korea, the annual installed PV capacity has increased over the years. However, the supply of photovoltaic panel fault diagnosis techniques for ... + READ MORE
    In Korea, the annual installed PV capacity has increased over the years. However, the supply of photovoltaic panel fault diagnosis techniques for efficient management is stil insufficient. Thus, many research groups and companies have been developing photovoltaic panel fault diagnostic equipment to measure I-V characteristics (1500 VMax. and 50 AMax.) and calculate the power efficiency of photovoltaic panels to quickly detect faults. In these methods, the capacitor load is used to measure the I-V curve of the photovoltaic panel. In addition, a MOSFET is used for stable I-V measurement and Multiplexing, and a high sampling ADC is used for simultaneous and quick (6 s) multi-channel measurements. - COLLAPSE
    December 2020
  • Research Article

    ADC Noise Reduction Technology to Improve the Diagnostic Accuracy of Solar Panel Fault Diagnosis Systems

    태양광 패널 고장진단기기의 진단 정밀도 향상을 위한 ADC 노이즈 저감기술에 대한 연구

    Shin Hyun-Jin ・ Seon Yong-Geun ・ Choi Eui-Seong ・ Shin Woo-Gyun ・ Ko Suk-Whan ・ Ji Pyeong-Shik

    신현진・선용근・최의성・신우균・고석환・지평식

    According to the IEA PVPS report, the global power of new photovoltaic plants in 2018 is approximately 100 GW. Large investments are ... + READ MORE
    According to the IEA PVPS report, the global power of new photovoltaic plants in 2018 is approximately 100 GW. Large investments are expected to be made in photovoltaics in the future to improve these renewable energy sources. Photovoltaic generation is a structure that makes profits by selling power produced for 20 years, and the annual generation amount decreases by 0.7 to 0.8% every year. However, if the failure of solar panels is not detected at an early stage, their profitability cannot be guaranteed. To solve this problem, research on photovoltaic maintenance technology is required. - COLLAPSE
    December 2020
  • Research Article

    Evaluation of Satellite-Derived Solar Irradiance and Limitation in Ground Observation

    공공데이터포털에 등재된 천리안 1호 위성영상 기반 일사량의 검증 및 관측 일사량의 한계점

    Kim Chang Ki ・ Kim Hyun-Goo ・ Kang Yong-Heack ・ Kim Bo-Young

    김창기・김현구・강용혁・김보영

    Recently, satellite-derived solar irradiance data, generated by the Korea Institute of Energy Research, has been opened for public use via the Public ... + READ MORE
    Recently, satellite-derived solar irradiance data, generated by the Korea Institute of Energy Research, has been opened for public use via the Public Big Data Platform organized by the Ministry of Public Administration and Security. These data are the monthly mean of daily total irradiance for the domain with latitude between 32°N and 40°N and longitude between 124°E and 130°E with a horizontal resolution of 1 km. The purpose of this study is to evaluate the monthly mean of daily total irradiance by comparing it with the ground truth obtained from the Automated Synoptic Observing System (ASOS) in the Korea Meteorological Administration (KMA). For the investigation period, that is, from 2012 to 2019, the average value of the correlation coefficients for all stations is 0.913. In addition, the root mean square error, which is normalized to the observation, is 12.2%, which is larger than that reported in previous studies. The ground observations employed for the evaluation were not performed by data quality control system. In the Daejeon station, in-situ observation from ASOS in KMA is significantly different from the measurement that is controlled by a data quality system, which means that in-situ observation from ASOS in KMA would be dangerous for use in the evaluation. With the solar irradiance controlled by the data quality control system, the root mean square error is reduced from 15.8% to 5.3%. Therefore, it is necessary to examine the in-situ observation via data quality control for the quantitative analysis of satellite-derived solar irradiance. - COLLAPSE
    December 2020
  • Research Article

    Multi-Year and Typical Year Data for Solar Energy System in South Korea
    Laetitia Uwineza ・ Kim Hyun-Goo ・ Kim Jin-Young ・ Kim Boyoung ・ Kim Chang Ki
    Typical meteorological year (TMY) data has significant importance for solar resource assessment, as well as for building performance analysis. The necessity of ... + READ MORE
    Typical meteorological year (TMY) data has significant importance for solar resource assessment, as well as for building performance analysis. The necessity of high-accuracy TMY data has been well known for many years for the financial viability of solar long-term planing project as it represents long-term weather features. However, the TMY does not mean the use of real-time data; it is therefore important to determine the accuracy of the TMY dataset. In this study, the solar energy performance of TMY was evaluated quantitatively by comparing it to multi-year average weather data (2008-2017) based on the statistical analysis method. The PV power output were produced by using 100kW photovoltaic system based on PVsyst software at six sites. The results showed that the difference between the TMY-PV power output and long-term PV power output (measured with percentage error) are smaller than 9%, which means there is close-fit agreement between TMY and long-term averages PV power output. These findings suggests that TMY can provide reliable estimation of PV power in the feasibility study of PV project. - COLLAPSE
    December 2020
  • Research Article

    Validation of Building Power Consumption Prediction Accuracy According to Frozen Number of Layers based on Transfer Learning

    전이 학습 기반 고정된 레이어 수에 따른 건물 전력 소비량 예측 정확도 검증

    Ahn Yusun ・ Chin Kyung-Il ・ Lee Yong-Jun

    안유선・진경일・이용준

    Owing to recent advances in data-driven technologies, prediction models can now be utilized in various fields such as energy consumption prediction. Among ... + READ MORE
    Owing to recent advances in data-driven technologies, prediction models can now be utilized in various fields such as energy consumption prediction. Among them, transfer learning, which enables prediction using data collected for a short term, is actively gaining ground. In the field of building energy, attention is focused on predicting the power consumption of buildings with the development of smart grids and micro-grids. The purpose of this study is to implement a machine learning (ML) method using the transfer learning algorithm that enables the prediction of energy consumption of the buildings using data collected for a short-term period. This study also validates the accuracy of the predicted energy consumption by adjusting the number of frozen layers based on the input parameters used in the ML method. A total of 5 layers were set, and the frozen layers were increased from 0 to 5. In addition, to validate the prediction rate of the transfer learning algorithm, only the existing ML model was used. As a result, when 0 through 3 layers were fixed, the accuracy criterion tended to be met. In contrast, when the 4-5 layers were reflected, the accuracy criterion was not met. It should also be noted that the model without using transfer learning showed poor accuracy. - COLLAPSE
    December 2020
  • Research Article

    Economic Analysis of Residential BESS Connected to Balcony-PV in Apartment Houses Using HOMER

    공동주택 발코니 PV 연계 가정용 BESS의 HOMER를 이용한 경제성 분석

    Eum Ji-Young ・ Kim Yong-Ki

    엄지영・김용기

    The Seoul metropolitan area and many local governments are supporting a project that involves installing and using PV (Photovoltaic) modules on the ... + READ MORE
    The Seoul metropolitan area and many local governments are supporting a project that involves installing and using PV (Photovoltaic) modules on the balconies of apartment houses in Korea. The power capacity of the installed PV is generally 300 W (a single PV module) per household. If the power capacity of the PV module is larger than the peak load of the household during the PV generation time, the surplus power cannot be utilized. Therefore, the necessity of a battery energy storage system (BESS) that can utilize the PV surplus power is being increasingly felt. In this study, we analyzed the economic efficiency of the residential BESS connected to a balcony- PV using HOMER (Hybrid Optimization of Multiple Energy Resources) software in Korea. The simulation was conducted for five cases in which the price of each component of BESS with balcony-PV and the limit installation capacity of the PV module were variable. As a result, when the balcony-PV and residential BESS were 50% (915,000 won) lower than the current price (1,830,000 won) and a PV with a power capacity of 1.2 kW was installed, the electric power charge was reduced by 34.2% (NPC 10,207,600 won) and the payback period required 4.09 years compared with the pre-installation times (NPC 15,519,570 won). - COLLAPSE
    December 2020
  • Research Article

    Development of an Empirical Model for Photosynthetically Active Radiation Direct Normal Irradiance using Spectral Direct Normal Irradiance in Daejeon

    대전지역에서 법선면직달일사량을 이용한 광합성유효 복사량의 직달 성분 추정 모델 개발

    Choi Kyung Bae ・ Lee Yun Gon ・ Kim Chang Ki

    최경배・이윤곤・김창기

    Photosynthetically active radiation (PAR; wavelength 400–700 nm) is the spectral range of solar radiation used by plants for photosynthesis. It is ... + READ MORE
    Photosynthetically active radiation (PAR; wavelength 400–700 nm) is the spectral range of solar radiation used by plants for photosynthesis. It is necessary to use PAR data in various fields, such as the surface vegetation growth, light energy–chemical energy conversion process, and terrestrial carbon cycle. In this study, a direct normal irradiance (DNI) spectroradiometer installed at the Korea Institute of Energy Research was used to observe direct insolation over the whole wavelength ranges including PAR. The variabilities in solar radiation and wavelength sensitivity according to the solar zenith angle and the clearness index (an indicator of atmospheric turbidity), were analyzed using data collected during June–October, 2020. As the optical path increased, PAR DNI—having a short wavelength—showed greater attenuation than the near-infrared radiation (NIR). Additionally, an increase in the clearness index under the same optical path increased the PAR DNI relatively more. These results mean that the attenuation effect of atmospheric constituents under optical path can be different depending on the wavelength range. Based on the empirical model presented in previous studies and the observation data in Daejeon, the PAR DNI estimation model using DNI in the entire wavelength range were developed and evaluated. Although it was a short analysis period, each model showed an R2 of 90% or more, and the model with the clearness index, an indicator of atmospheric conditions, presented higher estimation accuracy. We expect that further data collection will enhance the accuracy of the model despite seasonal variability. Thus, this research will encourage broader applications of the model in other regions. - COLLAPSE
    December 2020