• Research Article

    Analysis of the Heat Transfer and Pressure Drop by the Turbulator Having a Non-Uniform Triangular Cross-Section in Air-Type PV/T Collector

    공기식 태양광/열 집열기 내 비균일 삼각 단면을 갖는 난류 촉진제에 의한 열전달 및 압력강하 성능 분석

    Kim Seongbhin, Moon Kwangam, Choi Hwiung, An Byungwha, Choi Kwanghwan

    김성빈, 문광암, 최휘웅, 안병화, 최광환

    A photovoltaic/thermal (PV/T) collector prevents a decrease in its electrical efficiency by reducing the temperature of the photovoltaic cell using a fluid. … + READ MORE
    A photovoltaic/thermal (PV/T) collector prevents a decrease in its electrical efficiency by reducing the temperature of the photovoltaic cell using a fluid. Air-type PV/T collectors use air as the fluid; however, the thermal efficiency of this collector is typically lower than that of other types of collectors. Thus, it is important to improve the thermal efficiency of air-type PV/T collectors. In this study, the heat transfer enhancement and pressure drop caused by a turbulator with a nonuniform triangular cross-section in a PV/T collector were analyzed as one of the methods for improving the thermal efficiency of a collector. The results were obtained using computational fluid dynamics analysis. As a results, the Nusselt number (Nu) and friction factor (f) improved 1.45 and 5.03 times, respectively, compared to those of the smooth air channel. The maximum thermal hydraulic performance parameter, which considered both the enhancement in heat transfer and the increase in pressure drop, was found to be 1.22. In addition, the correlations for Nu and f were developed as functions of the geometric conditions of the turbulator. The results indicated that the developed correlation could predict the simulated values with mean absolute percentage errors of 3.24% and 5.31% for Nu and f, respectively. - COLLAPSE
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    30 August 2023

  • Research Article

    UV Blocking Ga2O3/Cu2O Heterojunction Photoelectric Device

    UV를 차단하는 Ga2O3/Cu2O 이종접합 광전소자

    Ju Youngwoong, Bae Seunghan, Kim Woohyeok, Jeong Jinsol, Jung Uyoung, Lee Junsik, Choi Chanhyuk, Naveen Kumar, Juhyung Yun, Kim Joondong

    주영웅, 배승한, 김우혁, 정진솔, 정우용, 이준식, 최찬혁, Naveen Kumar, 윤주형, 김준동

    A transparent photoelectric device was fabricated using a metal-oxide heterojunction. Owing to the large energy bandgap of the p-type (Cu2O)–n-type … + READ MORE
    A transparent photoelectric device was fabricated using a metal-oxide heterojunction. Owing to the large energy bandgap of the p-type (Cu2O)–n-type (Ga2O3) junction, a space charge region was spontaneously formed, which provided an electric field to collect the photogenerated carriers, resulting in photovoltaics with solar-cell features. The formation of the Cu2O layer was modulated by the O2 flow rate to tune the photovoltage to 910 mV and the photocurrent to 3.2 mA/cm2. In addition, a transparent photovoltaic device was used along with the photodetectors to achieve high responsivity (149 mA/W) and detectivity (1.39 × 1012 Jones) at a wavelength of 340 nm. This suggests that high-performance and transparent Cu2O/Ga2O3 devices can be adopted for self-powering invisible human electronics. - COLLAPSE
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    30 August 2023

  • Research Article

    Development of Predicted Power Generation Nomogram of Photovoltaic System by Installation Conditions Using Typical Meteorological Year

    표준기상자료를 활용한 태양광발전 시스템의 설치 조건별 발전량 예측 노모그램 개발

    Kang Eun-Ho, Kim Jea-Won, Kim Dong-Soo, Yoon Jong-Ho

    강은호, 김재원, 김동수, 윤종호

    Recently, with the increase in the use of photovoltaic systems, the importance of evaluating data for the follow-up management of installed systems … + READ MORE
    Recently, with the increase in the use of photovoltaic systems, the importance of evaluating data for the follow-up management of installed systems has also gradually increased. In particular, the power generation prediction data of photovoltaic systems play an important role in evaluating the performance of installed systems. Therefore, in this study, the power-generation performance index of the photovoltaic system was derived by simulating the power-generation performance according to the installation angle using a typical meteorological year of the seven regions. Consequently, a monogram of the annual yield and performance factors was derived according to the installation angle in the seven regions. As a result of examining annual yield in the range of azimuth angle 180°±30° and inclination angle 30°±15°, the annual average yield for the seven regions was 1,238 kWh/kWp. The performance factors based on the installation inclination angle exhibited similar characteristics in most regions, except for Jeju. Jeju showed a high performance factor under a relatively low inclination-angle, and accordingly, it showed different characteristics from the other regions. - COLLAPSE
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    30 August 2023

  • Research Article

    Investigation on Architecture and Energy End-Use Characteristics of Korean Apartments for Whole-Building Energy Simulation Modeling

    한국형 공동주택 에너지 시뮬레이션 모델링을 위한 건물 형태 및 에너지 사용 특성 분석

    Lee Ru-Da, Kang Eun-Ho, Yoon Jong-ho, Kim Dong-Su, Kim Jin-Hwi, Won Jong-Yeon

    이루다, 강은호, 윤종호, 김동수, 김진휘, 원종연

    Apartment (APT)-type buildings are the most common type of domestic housing and are expected to continue to grow. Therefore, it is important … + READ MORE
    Apartment (APT)-type buildings are the most common type of domestic housing and are expected to continue to grow. Therefore, it is important to analyze the building energy consumption and improve the overall energy efficiency. Simulation-based analysis is typically adopted for building energy evaluation to predict energy usage and identify the potential savings of alternative designs or options. A validation process for the simulation models is required to ensure that the developed model accurately predicts the energy consumption and performance of the building. In this study, we investigated the architecture and energy behavior of domestic APTs that can be used for simulation-based modeling and calibration processes. In this process, for analyzing the building energy characteristics, we investigated the building energy end uses, such as electricity and gas energy consumption. Various datasets and sources, such as public data, actual measurement data, and surveyed drawings, were utilized to identify the representative features and combined relevance between buildings and their energy usage for building energy simulation modeling. The results of this study will help to suggest benchmark building energy simulation analyses for apartment-type buildings. - COLLAPSE
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    30 August 2023

  • Research Article

    Estimation of LCOE Ranges and Analysis of Cost Components for Korean Fixed-Bottom Offshore Wind Farms

    국내 고정식 해상풍력발전단지의 LCOE의 범위 추정과 비용구성요소 분석

    Lee Keon-Woo, Ko Kyung-Nam

    이건우, 고경남

    The levelized cost of energy (LCOE) was estimated for Korean fixed-bottom offshore wind farms. The actual financial data of the two offshore … + READ MORE
    The levelized cost of energy (LCOE) was estimated for Korean fixed-bottom offshore wind farms. The actual financial data of the two offshore wind farms were collected from the Data Analysis, Retrieval and Transfer System (DART) of the Korean Financial Supervisory Service and categorized to calculate capital expenditure (CapEx) and operational expenditure (OpEx). The CapExs of the three offshore wind farms in the planning stage were added to those of the two actual wind farms. A capacity factor (CF) of 30% was assumed for this study, and a discount rate of 4.5% was used, which is the Korean social discount rate. Two cases were considered for estimating the LCOE using the actual OpEx data of the two Korean offshore wind farms (Case 1) and the ratio of OpEx to CapEx of the world (Case 2). A Monte Carlo simulation (MCS) was performed to estimate the LCOEs, because the financial data were not sufficient to compute the real data. CapEx, OpEx, and the ratio were extracted as random numbers for MCS. To clarify the features of the cost components of offshore wind farms, the LCOE was divided into levelized fixed costs (LFC) and levelized variable costs (LVC). Consequently, the LCOEs for Cases 1 and 2 are 189 and 193 USD/MWh, respectively. The LVC for the two cases were 65 and 57 USD/MWh, respectively. The LCOE of Korean offshore wind farms was higher than that worldwide, except for that of Japan. - COLLAPSE
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    30 August 2023

  • Research Article

    Analysis of Power Consumption Patterns and Power Generation Amount of Balcony Photovoltaic System by Apartment Household in Seoul

    서울지역 아파트 세대별 전력소비패턴 및 발코니 태양광 설비의 발전량 분석

    Eum Ji-Young, Kim Yong-Ki

    엄지영, 김용기

    For apartments with 30 or more households, the government is implementing a zero-energy building mandate from 2023 in the public sector and … + READ MORE
    For apartments with 30 or more households, the government is implementing a zero-energy building mandate from 2023 in the public sector and 2024 in the private sector. Many local governments are promoting mini-photovoltaic (PV) system supply support projects that can be installed on apartment balconies. An apartment mini-PV system is a concept that installs a PV module on a balcony and directly supplies the power from the PV to the household outlet through a plug. In this study, we analyzed real-time power consumption patterns for approximately one year for apartments in the Seoul area and analyzed the amount of power generated by mini-PV systems installed on balconies. The power consumption pattern by household and the amount of PV power on the balcony showed significant differences owing to the influence of life patterns of the residents, PV installation capacity, and installation environment. However, power consumption was the highest during the evening and summer, and balcony PV power was highest during spring and autumn. In addition, a large amount of surplus power is generated during the PV generation. The balcony photovoltaic system contributes to a household electricity energy self-sufficiency rate of 26%, on average, for four households by electricity production. - COLLAPSE
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    30 August 2023

  • Research Article

    Experimental Study on the Cooling Performance Evaluation of a Thermally Activated Light Shelf System

    광선반형 복사냉방패널 시스템의 냉방성능 평가 실증 연구

    Rhee Kyu-Nam, Kim Sang-Yeop

    이규남, 김상엽

    In this study, cooling performances were experimentally evaluated for a thermally activated light shelf (TALS), which was represented by integrating a light … + READ MORE
    In this study, cooling performances were experimentally evaluated for a thermally activated light shelf (TALS), which was represented by integrating a light shelf with a radiant cooling panel. A full-scale test-bed was constructed to evaluate the cooling performance of the TALS in terms of the cooling energy and thermal environment. Three TALS alternatives were evaluated: the INS case wherein the insulation was filled in the TALS, the AIR case wherein the insulation was replaced by an air cavity, and the FAN case wherein small DC fans were installed in the AIR case for the enhancement of air flow. The experimental results showed that the TALS provides 11% ~ 51% additional cooling capacity of the fan coil unit (FCU) when it is utilized as an auxiliary cooling system for the FCU. It was found that the TALS can reduce the system operation time by 17.2 ~ 29.6% while it raises the chiller ΔT by up to 0.4 K, which implies a possible energy reduction due to the improved chiller efficiency. The cooling energy was reduced by 1.3% for the INS case and 2.7% for the FAN case, whereas the cooling energy was increased by 6.9% for the AIR case, because the cooled cavity air was not successfully used for space cooling. It was also deduced that the thermal environment can be improved, particularly at the perimeter zone, because the TALS can lower the radiant temperature at the perimeter zone. The application of the INS and FAN cases is proposed to improve the energy performance as well as the thermal environment in a building equipped with the TALS. - COLLAPSE
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    30 August 2023
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