• 전기학회논문지P
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• 제61권4호
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• pp.192-198
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• 2012

Switch losses directly affect the efficiency of power conversion systems and those have big differences according to the power consumed by load systems and the structures of power conversion circuits. In this paper, analyses for switch losses in DC link converter are performed based on the circuit structures of the DC/DC converter in photovoltaic generation system whose output power is varied according to the amount of solar radiation, temperature and partial shade on the solar modules. Boost converter is adopted as a DC link converter topology of the photovoltaic generation system and the loss analyses for the switches used in the boost converters are performed according to the circuit structures. Analyses like the things performed in this paper will be a prerequisite to designing the photovoltaic generation system whose output power is changed according to the environmental variations.

• 한국수소및신에너지학회논문집
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• 제30권4호
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• pp.297-302
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• 2019

In this paper, the power generation efficiency increase has been studied for a Rankine cycle using both supercritical carbon dioxide as a working fluid and LNG as a coolant with PRO/II with PROVISION release 10.0 from Aveva company. Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle using LNG cold heat. Power generation efficiency was increased from 24.82% to 57.76% when using LNG as a coolant for supercritical carbon dioxide power generation cycle.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.318-323
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• 2024

In this paper, computer modeling works have been performed for the power generation Rankine cycle using new working fluids and liquefied natural gas (LNG) cold heat. PRO/II with PROVISION released January 2023 from AVEVA company was used, and Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle. Optimal working fluid composition was determined to maximize LNG cold heat to increase power generation efficiency and net power production.

• 대한기계학회논문집B
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• 제36권2호
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• pp.205-210
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• 2012

화력발전은 지구온난화의 주범으로 인식되고 있지만, 산업화와 지속적인 국가경제성장에 의한 전력소요 증가는 에너지사용을 증대시켜 에너지 자원의 부족을 초래하고 환경오염물질의 과다배출로 지구 환경문제를 유발하고 있다. 에너지원의 확보를 위한 국가와 지역간 경쟁이 심화되어 새로운 갈등의 원인이 되고 있으며, 지구온난화와 에너지 문제를 해결하기 위해 교토의정서 등 기후변화 협약이 체결되고 화석에너지에 재생에너지로의 에너지원의 전환과 다양화가 추진되고 있지만, 각국의 이해관계와 기술부족으로 완벽한 해결책을 제시하지 못하는 상황이다. 에너지 부족을 해소하고 $CO_2$ 배출량을 저감할 수 있는 가장 효과적인 방안으로 기존 화력발전 효율을 향상시킨 고효율 발전과 Near Zero Emission 수준의 저공해 기술이 결합된 고효율 석탄화력발전시스템을 개발현황을 논하고자 한다.

• Applied Science and Convergence Technology
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• 제23권5호
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• pp.221-239
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• 2014

The global demand for energy has been increasing since past decades. Various technologies have been working to find a suitable alternative for the generation of sustainable energy. Photovoltaic technologies for solar energy conversion represent one of the significant routes for the green and renewable energy production. Despite of remarkable improvement in solar cell technologies, the generation of power is still suffering with lower energy conversion efficiency, high production cost, etc. The major problem in improving the PV efficiency is spectral mismatch between the incident solar spectrum and bandgap of a semiconductor material used in solar cell. Luminescent materials such as rare-earth doped phosphor materials having the quantum efficiency higher than unity can be helpful for photovoltaic applications. Quantum cutting phosphors are the most suitable candidates for the generation of two or more low-energy photons for the absorption of every incident high-energy photons. The phosphors which are capable of converting UV photon to visible and near-IR (NIR) photon are studied primarily for photovoltaic applications. In this review, we will survey various near IR quantum cutting phosphors with respective to their synthesis method, energy transfer mechanism, nature of activator, sensitizer and dopant materials incorporation and energy conversion efficiency considering their applications in photovoltaics.

• 한국수소및신에너지학회논문집
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• 제17권4호
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• pp.409-417
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• 2006

The characteristics of hydrogen-oxygen mixture gas generation stack was experimentally studied in terms of efficiency. For this purpose, the mixture gas generation stack was fabricated by connecting 7 cells in series following the Tero Ranta report. In order to avoid the instrument inaccuracy, all measuring equipments were re-tested and calibrated by Korea Laboratory Accreditation Scheme (KOLAS) certified laboratories. Since the amount of produced gas is most crucial in determining the efficiency, two gas collecting methods such as bottle trap method and wet gas meter method were adopted. From the experimental results, it was found that both KOH fume and steam evaporated along with hydrogen-oxygen mixture gas, and these by-product gases could cause the misestimation of the stack efficiency. The current, voltage, and energy efficiencies of the hydrogen-oxygen mixture gas generation stack was evaluated based upon the stack efficiency calculation method summarized in this work.

• 한국응용과학기술학회지
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• 제36권4호
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• pp.1427-1433
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• 2019

본 연구에서는 합성가스의 에너지화를 위한 가스엔진 성능 평가를 수행하였다. 회전수 1800 rpm 조건에서 공기과잉률이 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 증가에 따른 엔진출력(kW_m)과 열효율(%)을 평가한 결과, 공기과잉률 λ 1.4에서 엔진출력 34 kW_m를 나타냈으며, 공기과잉률이 증가할수록 엔진 열효율은 전반적으로 감소하는 경향을 보였다. 엔진출력 34 kW_m 조건에서 공기과잉률이 1, 1.1, 1.2, 1.3, 1.4 증가시 열효율이 34.2%, 36.9%, 37.2%, 37.4%, 38.1%로 증가하였고, 발전출력을 통한 종합효율은 발전출력 30 kWe 부하조건에서 38.7 kg/h의 연료를 소모하여 32.1%의 발전효율과 냉각수와 배기가스에서의 열회수를 통해 57.3 kW의 폐열을 회수하여 53.8%의 열을 회수하여 총 85.8%의 종합효율을 보이는 것으로 나타났다.

• KIEAE Journal
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• 제11권6호
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• pp.87-93
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• 2011

This study examines building's power consumption unit cost and Building Integrated Photovoltaic (BIPV)'s generation efficiency and load rate with the subjects of university dormitory buildings in order to suggest foundational data for new and recycled energy use and management to plan and operate university dormitories afterwards. Thereby, this research gained the following findings. 1. The quantity of solar radiation and efficiency change in the BIPV system applied to the research subject buildings after the lapse of time was averagely 8.7%, and it is thought that temperature increase determines conversion efficiency with the influence of surrounding outside temperature and the module's temperature. 2. The generation efficiency of the BIPV system in the research subject buildings was averagely 10.9%. In May, it was 13.9%, and in January, it was the lowest as 10.25%. Considering the fact that power consumption reduces during an intermediate period, it will be necessary to establish measures for equipment and power consumption load balancing. 3. The monthly load rate of the BIPV system was averagely 4.09%. In May, it was the highest as 4.94%, and in July, it was the lowest as 3.24%. 4. It is intended to conduct constant follow-up research on estimating university dormitory building's power consumption unit cost and examining the generation efficiency and load rate of the BIPV system.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.208.1-208.1
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• 2010

일일 50톤 처리용량의 도시고형폐기물소각설비의 폐열 보일러에서 생산되는 4.0~6.5 bar의 저압증기를 이용하여 전력을 생산하는 축류식 MSTG설비에 있어서 공급증기압력, 입출구의 압력차이에 의한 발전효율을 비교하고, 저압의 증기의 균질화를 위한 기술분리, 정압유지설비 및 증기터빈의 본체의 기수분리된 증기의 응축효율을 증기공급율, 발전효율별로 비교분석하였다. 공급되는 증기의 압력, 증기터빈의 입출구 압력 차이가 높아짐에 따라, 증기의 응축효율이 증가를 하였으며, 배출되는 증기량에 따른 발전효율의 증가는 없었다. 따라서, 가변적으로 변하는 저압의 증기를 기수분리 및 정압을 유지하여도 증기질의 변동이 없으며 그에 따른 증기의 엔탈피 변화가 없으므로 발전 효율의 향상을 기대하기는 어려웠다.

• 전기학회논문지
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• 제59권3호
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• pp.604-608
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• 2010

An electric fan for cooling high density electronic devices is limited and operated in very low efficiency. The corona discharge is utilized as the driving mechanism for an ionic gas pump, which allows for air flow control and generation with low noise and no moving parts. These ideal characteristics of ionic pump give rise to variety applications. However, all of these applications would benefit from maximizing the flow velocities and yields of the ionic pump. In this study, a needle-mesh type ionic pump has been investigated by focusing on the radius of curvature of corona needle points elevating the ionic wind velocity and efficiency. It is found that the radius of curvature of the corona discharge needle point influences significantly to produce the ionic wind and efficiency. As a result, an elevated ionic wind velocity and increased ionic wind generation yield can be obtained by optimized the radius of curvature of the corona needle electrode.