• Proceedings of the KIEE Conference
• /
• 2003.11a
• /
• pp.348-350
• /
• 2003

본 논문에서는 태양광-풍력 복합발전시스템의 발전용량 예측을 통한 시스템 시설투자비 및 발전단가와 경제성에 대하여 분석한다. 도시지역의 일사량 및 풍속 데이터를 기초로 하여 복합발전시스템의 일일 발전량을 구하고, 수용가의 일일부하패턴과 수요부하를 고려하여 태양전지 어레이와 풍력발전기의 용량을 산정한다. 그리고 용량 산정에 따른 복합발전시스템의 초기투자비용과 연간 발전량, 연간 소요경비 등의 요소를 고려하여 총 수명가 분석법(Total Life-Cycle Cost Analysis)에 기초한 발전단가를 계산하고 잉여전력을 계통에 판매할 경우의 경제성을 평가한다.

• Journal of Power Electronics
• /
• v.19 no.6
• /
• pp.1544-1553
• /
• 2019

The efficiency of photovoltaic generation systems depends on the maximum power point tracking (MPPT) technique. Among the various schemes presented in the literature, the incremental conductance (INC) method is one of the most frequently used due to its superb tracking ability under changes in insolation and temperature. Generally, conventional INC algorithms implement a simple duty-cycle updating rule that is mainly found on the polarity of the peak-power evaluation function. However, this fails to maximize the performance in both steady-state and transient conditions. In order to overcome this limitation, a novel regulated INC (r-INC) method is proposed in this paper. Like the compensators in automatic control systems, this method applies a digital compensator to evaluate the INC function and improve the capability of power tracking. Precise modeling of a new MPPT system is also presented in the optimized design process. A 120W boost peak power tracker is utilized to obtain comparative test results and to confirm the superiority of the proposed method over existing techniques.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.2
• /
• pp.110-118
• /
• 2008

The regulated peak power tracking (RPPT) systems such as the series structure and the parallel structure are commonly used in the satellite space power system. However, this structure processes the solar array power to the load through two regulators during one orbit cycle, which reduces the energy transfer efficiency. The series-parallel structure for the RPPT system can improve the power conversion efficiency, but an additional regulator increases the cost, size and weight of the system. In this paper, a simplified series-parallel space power system that consists of two regulators is proposed. The proposed system has the similar energy transfer efficiency with the series-parallel structure by adding one switch to the series structure, which reduces the cost, size and the weight. The large signal stability analyses is provided to understand the four main modes of system operation. In order to compare the energy efficiency with a series structure, the simulation is performed. The experimental verifications are performed using a prototype hardware with TMS320F2812 DSP and 200W solar arrays.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.04a
• /
• pp.269-276
• /
• 2009

South Korea having military power within the $10^{th}$ in world ranking is the biggest single institution among public institutions in Korea and comprises force of over seven hundred thousand soldiers. However, outworn equipments and efficiency problem have issued. So, this study is to search the distribution state of new-renewable energy and to analyze application plan on the basis of interview with a official in charge in military. Analysis process is the first, classify surveyed military facilities into troops and the geographical factor. Second, classify a scale and type of facilities that new-renewable energy is supplied. Third, find consideration facts on the basis of interview with a official in charge. On the results of the survey, new-renewable energy applied to the military facility is photovoltaic, solar heat, wind power and geo-thermal energy. Also, divide military into the army, navy, air force and marine, visit 14 units and analyze the official's opinion. This study will deduce LCCA(Life cycle cost analysis) considered expenses for the installation and maintenance, and will be basic research that suggest an appropriate new-renewable energy model in military.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.1
• /
• pp.15-23
• /
• 2013

In this study, thermodynamic performance of R435A is examined both numerically and experimentally in an effort to replace HFC134a used in the refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in the near future in Europe and most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experimental measurements are carried out with a new refrigerant mixture of 20%R152a/80%RE170 using actual domestic water purifiers. This mixture is numbered and listed as R435A by ASHRAE recently. Test results show that the system performance with R435A is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system of the domestic water purifiers. With the optimum amount of charge of 21 to 22 grams, about 50% of HFC134a, the energy consumption of R435A is 11.8% lower than that of HFC134a. The compressor discharge temperature of R435A $8^{\circ}C$ lower than that of HFC134a at the optimum charge. Overall, R435A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a requiring little change in the refrigeration system of the domestic water purifiers.

• Solar Energy
• /
• v.19 no.3
• /
• pp.23-28
• /
• 1999

The thermal performance of storage brick, containing microencapsulated PCM(phase change material), was investigated for utilization as a floor heating system. Sodium acetate trihydrate($CH_3COONa{\cdot}3H_2O$) was selected for the PCM and was encapsulated. The thermal storage brick was manufactured with mixing cement mortar having 10%, 20% PCM contents, respectively. Four different flow rates and three different cooling temperatures was used in this work for analyzing the heat charging and discharging characteristics of the thermal storage brick. The result showed that cycle time was shortened as the PCM content was increased and as the mass flow rate was increased. The same effect was obtained when the cooling temperature was decreased. For each thermal storage brick the overall heat transfer coefficient(U-value) was constant for a 0% brick, but was increased with time for the bricks containing microencapsulated PCM.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.6 no.3
• /
• pp.149-163
• /
• 2004

Evapotranspiration (ET) is a critical component of the hydrologic cycle which influences economic activities as well as the natural ecosystem. While there have been numerous studies on ET estimation for homogeneous areas using point measurements of meteorological variables, monitoring of spatial ET has not been possible at landscape - or watershed - scales. We propose a site-specific application of the land surface model, which is enabled by spatially interpolated input data at the desired resolution. Gyunggi Province of South Korea was divided into a regular grid of 10 million cells with 30m spacing and hourly temperature, humidity, wind, precipitation and solar irradiance were estimated for each grid cell by spatial interpolation of synoptic weather data. Topoclimatology models were used to accommodate effects of topography in a spatial interpolation procedure, including cold air drainage on nocturnal temperature and solar irradiance on daytime temperature. Satellite remote sensing data were used to classify the vegetation type of each grid cell, and corresponding spatial attributes including soil texture, canopy structure, and phenological features were identified. All data were fed into a standalone version of SiB2(Simple Biosphere Model 2) to simulate latent heat flux at each grid cell. A computer program was written for data management in the cell - based SiB2 operation such as extracting input data for SiB2 from grid matrices and recombining the output data back to the grid format. ET estimates at selected grid cells were validated against the actual measurement of latent heat fluxes by eddy covariance measurement. We applied this system to obtain the spatial ET of the study area on a continuous basis for the 2001-2003 period. The results showed a strong feasibility of using spatial - data driven land surface models for operational monitoring of regional ET.

• Journal of the Korean Solar Energy Society
• /
• v.38 no.1
• /
• pp.45-55
• /
• 2018

Environmentally benign lead-free solder coated ribbon (e. g. SnCu, SnZn, SnBi${\cdots}$) has been intensively studied to interconnect cells without lead mixed ribbon (e. g. SnPb) in the crystalline silicon(c-Si) photovoltaic modules. However, high melting point (> $200^{\circ}C$) of non-lead based solder provokes increased thermo-mechanical stress during its soldering process, which causes early degradation of PV module with it. Hence, we proposed low-temperature conductive paste (CP) based tabbing method for lead-free ribbon. Modules, interconnected by the lead-free solder (SnCu) employing CP approach, exhibits similar output without increased resistivity losses at initial condition, in comparison with traditional high temperature soldering method. Moreover, 400 cycles (2,000 hour) of thermal cycle test reveals that the module integrated by CP approach withstands thermo-mechanical stress. Furthermore, this approach guarantees strong mechanical adhesion (peel strength of ~ 2 N) between cell and lead-free ribbons. Therefore, the CP based tabbing process for lead free ribbons enables to interconnect cells in c-Si PV module, without deteriorating its performance.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.115.2-115.2
• /
• 2012

In this study we have used the data of various instruments onboard the THEMIS spacecraft to study the characteristics of the outer radiation belt during the ascending phase of solar cycle 24. The most astonishing result is that we discovered four long-term (a month or so) periods during which the belt has nearly disappeared. The first disappearance started late 2008, followed by reappearance in ~a month, and three more similar events repeated until early 2010 when the belt has reappeared. This is well revealed at 719 keV electrons, which is the currently available uppermost energy channel from the THEMIS SST observation, but also seen at even lower energies. Overall consistent features were confirmed using the NOAA-POES observations. The vanished belt periods are associated with extremely weak solar wind conditions, low geomagnetic disturbances (in terms of Kp and AE/AL), greatly suppressed wave (ULF and chorus) activities, greatly reduced storm and substorm activities (little source particle supply), and expanded plasmapause locations. The direct observations of such events shed light on the fundamental question of the origin of the radiation belt, which is the main focus of our presentation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.2
• /
• pp.94-102
• /
• 2009

Conceptual design of scroll expander and scroll compressor for 10kW-class Stirling engine utilizing solar energy as heat source has been carried out to estimate the applicability of scroll mechanism for Stirling cycle. CO2 was chosen as working fluid, since it has lower expansion index and higher density among probably usable gases. Gas temperature at the expander inlet was set at $700^{\circ}C$, and that at the compressor inlet was at $40^{\circ}C$. System efficiency reached maximum at the pressure ratio of about 2.5, and the peak efficiency increased with increasing high side pressure. Due to safety concern, the pressure condition of 6 MPa/2.5 MPa was chosen as design condition. Orbiting scroll members for the expander and compressor were designed to have double-sided structure in order to reduce the overall scroll size and to cancel out the axial gas forces acting on the orbiting scroll base plate. By parametric study on the scroll profile, smaller possible size for the scroll members was obtained. With the shaft speed of 3600rpm, the shaft output of the designed scroll expander was calculated to be 45.4kW, while input power for the scroll compressor was 34.5kW, yielding 10.9kW for the output power of the Stirling engine. System efficiency was estimated to be about 7.3%, and overall efficiencies of the scroll expander and compressor were around 84.1% and 88.3%, respectively.