• Article

    Comparative Analysis of System Performance for Water, Ground and Air Source Heat Pump System Using the Dynamic Energy Simulation

    동적 에너지 시뮬레이션을 이용한 수열원, 지열원 및 공기열원 히트펌프 시스템의 성능 비교분석

    Kwon Youngsik, Bae Sangmu, Nam Yujin, Yun Rin, Park Chang Yong, Lee Hoseong

    권영식, 배상무, 남유진, 윤린, 박창용, 이호성

    As the boundary of water source energy has recently expanded to the use of river, lake, and pond waters, the water source ... + READ MORE
    As the boundary of water source energy has recently expanded to the use of river, lake, and pond waters, the water source heat pump (WSHP) system is becoming a major issue. However, to apply the WSHP system to a real building, a comparison and analysis with a ground source heat pump (GSHP) and an air source heat pump system (ASHP) are required. Moreover, it is necessary to accurately analyze the performance of a WSHP based on the building load condition. Therefore, this study aims to analyze the performance of WSHP, GSHP, and ASHP systems for large office buildings using a dynamic energy simulation. The seasonal performance factor (SPF) of the system was calculated as 3.8 and 2.5 for a WSHP system, 3.8 and 2.6 for a GSHP system, and 2.9 and 1.7 for an ASHP system during the cooling and heating periods, respectively. The performance of the WSHP system was similar to that of the GSHP system and was 23% and 32% higher than that of the ASHP system, respectively. - COLLAPSE
    August 2021
  • Article

    Simulation Modeling of Simultaneous Heating and Cooling System with Thermal Storage Tanks using Radiant Heating and Cooling

    복사냉난방 시스템을 적용한 축열식 동시냉난방 시스템의 시뮬레이션 모델링

    Shin Dae-Uk

    신대욱

    Simultaneous heating and cooling systems (SHCs) can be effectively applied in large-scale, multi-purpose, or multi-ethnic buildings where both heating and cooling are ... + READ MORE
    Simultaneous heating and cooling systems (SHCs) can be effectively applied in large-scale, multi-purpose, or multi-ethnic buildings where both heating and cooling are required. This study is aimed at the development of a dynamic simulation model of an SHC with thermal storage tanks using a radiant system. To achieve this, the mechanism of each component of the entire system focusing on the terminal device was analyzed, a flowchart based on the mechanism was created, and dynamic simulation modeling was developed. Finally, a simulation was conducted on a building in which simultaneous heating and cooling occurred using the developed simulation model. The simulation model proposed in this study can be used for system applications in buildings where simultaneous heating and cooling occurs, and can also be used as a basic simulation model for various studies, such as system design and operation techniques. - COLLAPSE
    August 2021
  • Article

    Simulation Performance Analysis of an Air-type PVT Collector with Curved Baffles

    곡선형 집열 베플이 적용된 공기식 PVT 컬렉터의 연간 시뮬레이션 성능분석

    Ahn Jong-Gwon, Yu Ji-Suk, Kim Jin-Hee, Kim Jun-Tae

    안종권, 유지숙, 김진희, 김준태

    A photovoltaic thermal (PVT) collector uses solar energy efficiently to produce heat and electricity simultaneously. In particular, an air-type PVT collector has ... + READ MORE
    A photovoltaic thermal (PVT) collector uses solar energy efficiently to produce heat and electricity simultaneously. In particular, an air-type PVT collector has advantages over a water type collector because the latter is prone to fluid leakage and condensation problems. However, the performance of an air-type PVT collector is affected by design criteria such as the inner structure (baffle or fins) and fluid path. For this research, PV cell lines arranged alternately with empty lines and curved absorbers were installed in the collecting space of a PVT collector. The absorber was utilized as a baffle to improve its thermal performance. In this study, an outdoor experiment of the PVT collector was conducted. Furthermore, the experimental and simulation results were compared. In addition, the annual thermal and electrical performance of the PVT were evaluated based on TRNSYS modeling. - COLLAPSE
    August 2021
  • Article

    Analysis of the Aesthetic Improvement and High Efficiency of Color PV Module Based on Dot Pattern

    Dot 패턴 기반 컬러 태양광 모듈의 심미성 향상 및 고효율화 연구

    Kim Daesung, Yang Yeonwon, Ryu Boyeon, Kim Mingyu, Ju Jin, Cho Sungbae

    김대성, 양연원, 유보연, 김민규, 주진, 조성배

    The solar energy market in South Korea has shown a high growth rate, with an expectation of reaching 4 GW in 2022 ... + READ MORE
    The solar energy market in South Korea has shown a high growth rate, with an expectation of reaching 4 GW in 2022. Plans to expand BIPV (Building Integrated Photo Voltaic) when new buildings are created have recently been increasing in preparation for a mandatory zero energy policy. Currently, zero-energy construction is mandatory for public buildings of over 1,000 m2. By gradually expanding the scope of the target, the mandatory designation of all buildings of over 500 m2 as zero-energy buildings is expected to occur by 2030. In this paper, we describe an efficiency optimization study based on the width ratio, coverage rate, and color of the patterns for an aesthetic improvement and high efficiency of the product. We aim to develop 50 W dot-pattern-based color solar modules that can improve the artistry and value of buildings when BIPVs are installed. A commercialization model is needed to expand the BIPV product line, which can add design and functional elements in the domestic solar power market, which is expected to grow at rates of tens of gigawatts in the future. - COLLAPSE
    August 2021
  • Article

    Modeling of Boost Converter and Performance Comparison of Single-loop & Dual-loop Controller

    부스트 컨버터의 모델링과 단일 루프 & 이중 루프 제어기의 성능 비교

    Jo Yeong-Min, Lee Ju-A, Kim Yong-Rae, Kim Soo-Bin, Song Seung-Ho, Choi Ju-Yeop

    조영민, 이주아, 김용래, 김수빈, 송승호, 최주엽

    To maximize the amount of power generated in a photovoltaic inverter, MPPT (Maximum Power Point Tracking) is an essential function of a ... + READ MORE
    To maximize the amount of power generated in a photovoltaic inverter, MPPT (Maximum Power Point Tracking) is an essential function of a photovoltaic (PV) inverter. A PV inverter generally consists of a DC/DC converter (boost converter) and a DC/AC inverter. For stable MPPT control, the controller of the boost converter must be properly designed. In this study, the nonlinear characteristics of solar cells were linearized and modeled for a proper controller design, and an analog controller was designed using MATLAB and converted into a digital controller. The controller was simulated using a designed controller based on PSIM, and the performances of a single-loop controller and dual-loop controller were compared. In addition, the performance of the controller was verified and compared experimentally by applying the designed controller to a commercial PV inverter. - COLLAPSE
    August 2021
  • Article

    Energy Performance Assessment for Remodeling Decision-Making based on Energy Usage Data of Existing Public Buildings in Seoul

    서울시 공공건축물 에너지 성능개선 리모델링 의사결정을 위한 에너지 사용량 데이터 분석

    Cho Ga Young, Yoo Jihyun

    조가영, 유지현

    The Seoul Metropolitan Government announced a 2050 greenhouse gas reduction strategy through the Green New Deal promotion and proposed a plan to ... + READ MORE
    The Seoul Metropolitan Government announced a 2050 greenhouse gas reduction strategy through the Green New Deal promotion and proposed a plan to achieve carbon neutrality through the five major areas of green building, green mobility, green forest, green energy, and green cycles. Among them, it is of utmost importance to prepare for the transition of low-carbon zero-energy buildings in the building sector, which accounts for 67% of the total energy consumption and 68.2% of greenhouse gas emissions in Seoul. In particular, 71.4% of the 454,000 buildings in Seoul are aged, and measures to expand to the private sector are needed to overcome the economic crisis caused by COVID-19. Therefore, to prepare a decision-making plan to improve the energy performance of existing buildings, the operation status and energy usage survey were conducted on public buildings with a total floor area of 3,000 m2 or more. The uses of the buildings were classified as cultural, educational, medical, office, and training facilities. A regression analysis algorithm was used to analyze the energy usage patterns and conduct a relative evaluation. The study results are intended to be used as a decision-making method for the energy diagnosis and remodeling of existing buildings. - COLLAPSE
    August 2021
  • Article

    Heating Energy Performance of Heated Glass According to Insulation Level of the Residential Building

    주거건물 단열수준에 따른 발열유리의 난방에너지 성능 평가

    Lee Do-Hyung, Yoon Jong-Ho, Lee Kyung-Woo, Seo Mun-Goo

    이도형, 윤종호, 이경우, 서문구

    Heat losses through exterior windows and condensation on their surface can cause thermal discomfort inside a building. In addition, the use of ... + READ MORE
    Heat losses through exterior windows and condensation on their surface can cause thermal discomfort inside a building. In addition, the use of low energy-efficient windows tends to increase thermal heat losses, and thus building energy consumption. In this study, we present the performance evaluation of heated glass in a residential building when the system is applied to a building and used as a heating system. In this study, a simulation-based analysis was conducted to evaluate the heating energy consumption based on the insulation standards with different areas and types of heating systems in a residential building. The results of this study reveal that the heated glass used a relatively higher heating energy consumption when compared to those of the other two heating systems, including floor radiant heating and air-source heat pump systems. Although the heated glass exhibited the highest energy consumption, it is expected that the system can be used as an alternative to other systems, such as a floor radiating heating system. This is mainly because the heated glass includes high benefits of indoor thermal comfort and prevents the window surface from forming condensation. In terms of combinations of heating systems, a case that includes radiant floor and heated glass heating systems can be considered as the best option based on the study analysis because the traditionally preferred heating method in Korea is based on a radiant floor heating system. - COLLAPSE
    August 2021
  • Article

    Experimental Study of Thermochemical Two-step Water Splitting Cycle for Hydrogen by Fe-CeO2 Redox Metal Oxide Coated foam Device with 3kWth Sun-simulator

    인공 태양열 집광장치를 이용한 Fe-CeO2 전이금속 화합물이 코팅된 세라믹 금속 산화물 반응체의 열화학 이단계 물분해 싸이클 및 수소 생산의 실험적 연구

    Hyun-Seok Cho, Yu Sakai, Tatsuya Kodama

    조현석, 사카이유, 고다마타츠야

    A newly developed Fe-CeO2-coated ceramic-foam device has been designed, fabricated, and tested for higher oxygen/hydrogen productivity in the thermochemical ... + READ MORE
    A newly developed Fe-CeO2-coated ceramic-foam device has been designed, fabricated, and tested for higher oxygen/hydrogen productivity in the thermochemical two-step water-splitting cycle. For the fabrication of the Fe-CeO2-coated ceramic-foam device, the direct depositing method was adopted. This method, in which elemental Fe is doped into CeO2 and this is coated onto the ceramic foam matrix surface, has advantages for the fabrication of reactive foam devices. In the synthesis of Fe-CeO2, the degree of Fe doping was set at 10, 15, or 30 mol%, and the amount of Fe-CeO2 loaded onto the foam matrix surface was fixed at 30 wt%. A 3kWth sun-simulator was used as the heat source in the thermochemical two-step water-splitting cycle for hydrogen production. The thermal reduction step for releasing oxygen was conducted at an operating temperature of 1400°C for 45 minutes, and the subsequent water-decomposition step for producing hydrogen was carried out at 1200°C for 60 minutes. The performance of the newly developed Fe-CeO2 foam device was compared with that of previously tested foam devices fabricated by the co-precipitation method and the spin-coating method. - COLLAPSE
    August 2021
  • Article

    Development of Fatigue Load Prediction Algorithm for Wind Turbines

    풍력발전시스템 하중예측 알고리즘 개발

    Choi Jungchul, Son Eunkuk, Lee Gwangse, Kang Minsang, Lee Jinjae, Hwang Sungmok, Park Sail

    최정철, 손은국, 이광세, 강민상, 이진재, 황성목, 박사일

    Continuous fatigue information is essential for the structural health monitoring (SHM) of wind turbines. Faults, such as sensor failure, data loss, and ... + READ MORE
    Continuous fatigue information is essential for the structural health monitoring (SHM) of wind turbines. Faults, such as sensor failure, data loss, and cable disconnection, can result in a total loss of SHM. To avoid such a malfunction, machine learning algorithms and polynomial curve fitting are suggested to predict the missing fatigue data from the otherwise known measurement data. Artificial neural networks showed the best prediction performance. Decision trees and regularized linear regression are also powerful alternatives. - COLLAPSE
    August 2021
  • Article

    Data Generation for Machine Learning Applications in Building Operation

    기계학습 적용을 위한 건물에너지 데이터의 생성 방법론 개발

    Park Se-mi, Joe Jaewan, Park Jung-Kyu

    박세미, 조재완, 박정규

    Utilizing the machin learning (ML) algorithm for the building cooling/heating operations requires the actual building data. The robustness of the ML-based ... + READ MORE
    Utilizing the machin learning (ML) algorithm for the building cooling/heating operations requires the actual building data. The robustness of the ML-based controller depends on the amount and quality of the data. However, reserving actual building operation data is challenging because of the cost and time required. This study proposes the methodology for generating the synthetic simulation data the development of the ML (specifically, reinforcement learning) algorithm when the actual data are lacking or unavailable. As the first step toward investigating this methodology, we built two building models, an EnergyPlus simulation model and a grey-box model. The prediction performances of two models were quantified and evaluated. - COLLAPSE
    August 2021
  • Article

    Accuracy Assessment of Typical Meteorological Year Data for a Photovoltaic System using a Bootstrap Method
    Uwineza Laetitia, Kim Hyun-Goo, Kim Chang Ki, Kim Boyoung, Kim Jin-Young
    The typical meteorological year (TMY) is a key element in the long-term performance predictions of photovoltaic systems. However, there is a loss ... + READ MORE
    The typical meteorological year (TMY) is a key element in the long-term performance predictions of photovoltaic systems. However, there is a loss of some hourly measured weather data during the formation of the TMY dataset owing to a lack of observations. Therefore, various statistical techniques or satellite observations can be utilized to address this limitation, and these interpolated data may represent some degree of uncertainty that can influence the accuracy of the TMY data. This may in turn affect the long-term planning reliability of the photovoltaic systems. Therefore, a bootstrap method was used in this study to evaluate the accuracy of TMY datasets in the prediction of long-term photovoltaic yields. The electricity production uncertainties obtained through a simulation conducted using this TMY were calculated with a confidence level of 95% for each resulting value as validated based on the long-term average electricity yield. The results show that the bootstrap method provides valid and more useful information than the deterministic approach. Therefore, it is the best method for quantitatively analyzing uncertainty in TMY datasets. The results described herein can serve as a guide for risk management strategies and other business decisions related to solar energy projects. In addition, the results can help planners achieve greater confidence when applying TMY data to feasibility studies. - COLLAPSE
    August 2021
  • Article

    Decentralized Real-time Volt/Var Control of Distributed Generation in Distribution System

    배전계통에서 분산 기반 분산형전원의 실시간 전압 및 무효전력제어 방안

    Park Hak-Yeol, Jo Kun-Yik, Choi Joon-Ho

    박학열, 조건익, 최준호

    Renewable energy resource policies are being promoted to solve global resource depletion and environmental problems. Accordingly, as the connection between renewable energy ... + READ MORE
    Renewable energy resource policies are being promoted to solve global resource depletion and environmental problems. Accordingly, as the connection between renewable energy resources and the distribution system has increased, various problems such as degradation in the quality of the power produced and voltage fluctuations have occurred. In this study, to solve the voltage problem, we propose a decentralized real-time volt/var control of the distributed generations (DGs) in a distribution system. The proposed control scheme aims to maintain the voltage for a point of common coupling (PCC) within a specified range, and the proposed control is applied in two stages. The proposed control scheme compensates for the disadvantages of a conventional control scheme and shows a new control structure. The proposed control scheme was applied to the test distribution system using MATLAB and was verified to be more effective than the conventional control scheme. - COLLAPSE
    August 2021
  • Article

    Assessment of Long-Term Operational Performance of Building Attached PV System Installed on Horizontal Plane

    수평설치조건의 건물부착형 태양광발전시스템에 대한 장기 운영 성능평가

    Lee Hyo-Mun, Kang Eun-Ho, Kim Dong-Su, Yoon Jong-Ho

    이효문, 강은호, 김동수, 윤종호

    Regulations and certification systems have been installed in many building-applied renewable energy systems (BARESs). Efforts to investigate and maintain the performance of ... + READ MORE
    Regulations and certification systems have been installed in many building-applied renewable energy systems (BARESs). Efforts to investigate and maintain the performance of renewable energy systems (RESs) have been lacking from the perspective of users or facility managers. This maintenance issue has obstructed the RES from operating in terms of its original purpose. Therefore, in this study, the operation status is evaluated through a power generation performance analysis on building attached photovoltaic (BAPV) systems, which are representative BARESs. The average performance ratio (PR) was 68.97%, with 78.42% in 2012 when monitoring started and 62.34% after 6 years. The PR continued to decline over time, with a difference of 16.07% between 2012 and 2018. In addition, the losses were 2.22%, 3.14%, 3.51%, and 22.16% over the entire period for the balance of the system (BOS), module temperature, incident angle modifier, and miscellaneous losses, respectively. Although other losses did not change over time, the miscellaneous loss was 10.43% in 2012, which increased to 29.49% in 2018. The BAPV system has experienced a continuous performance degradation since 2012. This indicates that managers have conducted no maintenance or performance surveys. Furthermore, more power can be generated by the BAPV system if maintenance is regularly conducted. The literature review has shown that a system installed for regulation or certification is not maintained, and that the facility managers are being challenged. Therefore, it is necessary to consider means to guide the maintenance points or methods applied. - COLLAPSE
    August 2021
  • Article

    Condensation Heat Transfer Characteristics of R-1234yf with the Variation of Tube Diameter

    R-1234yf의 관경 변화에 따른 응축 열전달 특성

    Seol Sung-Hoon, Yoon Jung-In, Lee Joon-Hyuk, Cha Seung-Yun, Ha Su-Jeong

    설성훈, 윤정인, 이준혁, 차승윤, 하수정

    In this study, the condensation heat transfer characteristics of the R-1234yf refrigerant were analyzed according to the variation in tube diameter, which ... + READ MORE
    In this study, the condensation heat transfer characteristics of the R-1234yf refrigerant were analyzed according to the variation in tube diameter, which were then considered as condenser design data. The inner diameter of the experimental tube was varied from 3.7 mm to 5.3 mm. Subsequently, the heat transfer coefficient of R-1234yf was analyzed according to the changes in vapor quality, mass flux, saturation temperature, and pipe diameter. Slug flow was observed at a low mass flux, and annular flow was observed at a high mass flux. Furthermore, it was observed that the heat transfer coefficient’s value increased with increase in the vapor quality and mass flux, whereas it decreased with increase in the tube diameter and saturation temperature. By comparing the heat transfer coefficients of the refrigerants R-134a and R-1234yf, it was found that the heat transfer coefficient of R-134a is higher. Furthermore, four correlations were conducted, and it was found that the correlation of Dobson and Chato and the correlation of Bashar can predict the experimental condensation heat transfer coefficient within an error range of ±10%. - COLLAPSE
    August 2021
  • Article

    SiC Powder Manufacturing through Silicon Recovery from Waste Si Solar Cells

    폐 실리콘 태양전지의 실리콘 회수를 통한 SiC분말 제조

    Kim Ga Min, Chang Hyo Sik

    김가민, 장효식

    We recovered Si from the waste Si solar cell through a three-stage chemical process at room temperature and recycled the recovered Si ... + READ MORE
    We recovered Si from the waste Si solar cell through a three-stage chemical process at room temperature and recycled the recovered Si to investigate the manufacture of SiC particles. Metal electrodes made of Ag and Al were removed using either nitric acid solution or hydrochloric acid solution. After etching the metal electrodes, the anti-reflection coatings containing SiNx and SiOx were removed by employing a mixed solution of NH4HF2, H2O2, and H2SO4. Small quantities of impurities remaining in the Si solar cells were subsequently removed through the application of potassium hydroxide to recover Si. Based on the measurements conducted through inductively coupled plasma atomic emission spectroscopy, the purity of the recovered Si was found to be 99.99% (4N), and no high energy-consuming steps were involved in the proposed chemical process. Furthermore, by incorporating the 4N purity-grade Si, we successfully obtained SiC particles for usage in structural ceramic materials. This suggests that the proposed chemical process can aid in recycling recovered Si. - COLLAPSE
    August 2021
  • Erratum