• Journal of Sensor Science and Technology
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• v.7 no.1
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• pp.67-72
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• 1998

The crystallized CuPc and PbTe films are formed by thermal evaporation and pulsed ArF excimer laser ablation. Structural and electrical properties of thin film is observed by XRD and current-voltage(I-V) curves. From XRD analysis, both PbTe and CuPc thin films show a-axis oriented structure. For the measurement of photovoltaic effect, the transverse current-voltage curve of CuPc/Si, PbTe/Si and PbTe/CuPc/Si junctions have been analyzed in the dark and under illumination. The PbTe/CuPc/Si junction exthibits a strong photovoltaic characteristics with short circuit current($J_{sc}$) of $25.46\;mA/cm^{2}$ and open-circuit voltage($V_{oc}$) of 170 mV. Quantum efficiency and power conversion efficiency are calculated to be 15.4% and $3.46{\times}10^{-2}$, respectively. Based on the results of QE and ${\eta}$, the photocurrent process of PbTe/CuPc/Si junction can be explained as following three effective steps; photocarrier generation in the CuPc layer, carrier separation at PbTe/CuPc interface, and finally a transportation of electrons through the PbTe layer.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.306-309
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• 2005

One of the most critical issues in sol id oxide fuel cell (SOFC)running on hydrocarbon fuels is the risk of carbon formation from the fuel gas. The simple method to reduce the risk of carbon formation from the reactions is to add steam to the fuel stream, leading to the carbon gasification react ion. However, the addition of steam to fuel is not appropriate for the auxiliary power unit (APU) and potable power generation (PPG) systems due to an increase of complexity and bulkiness. In this regard, many researchers have focused on so-called 'direct methane' operation of SOFC, which works with dry methane without coking. However, coking can be suppressed only by the operation with a high current density, which may be a drawback especially for the APU and PPG systems. The single chamber fuel cell (SC-SOFC) is a novel simplification of the conventional SOFC into which a premixed fuel/air mixture is introduced. It relies on the selectivity of the anode and cathode catalysts to generate a chemical potential gradient across the cell. Moreover it allows compact and seal-free stack design. In this study, we fabricated honeycomb type mixed-gas fuel cell (MGFC) which has advantages of stacking to the axial direction and increasing volume power density. Honeycomb-structured SOFC with four channels was prepared by dry pressing method. Two alternative channels were coated with electrolyte and cathode slurry in order to make cathodic reaction sites. We will discuss that the anode supported honeycomb type cell running on mixed gas condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1288-1295
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• 2012

Korea Ministry of Knowledge Economy has estimated that wind power (WP) will be occupied 37% in 2020 and 42% in 2030 of the new energy sources, and also green energies such as photovoltaic (PV) and WP are expected to be interconnected with the distribution system because of Renewable Portfolio Standard (RPS) starting from 2012. However, when a large scale wind power plant (over 3[MW]) is connected to the traditional distribution system, protective devices (mainly OCR and OCGR of re-closer) will be occurred mal-function problems due to changed fault currents it be caused by Wye-grounded/Delta winding of interconnection transformer and %impedance of WP's turbine. Therefore, when Double-Fed Induction Generator (DFIG) of typical WP's Generator is connected into distribution system, this paper deals with analysis three-phase short, line to line short and a single line ground faults current by using the symmetrical components of fault analysis and PSCAD/EMTDC modeling.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.476-481
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• 2016

Steam power generation is used to produce electricity through a generator that is connected to a steam turbine. As a result, the surface temperature of the deaerator is $70^{\circ}C$during the summer season, the surface temperature of the storage tank is $67^{\circ}C$, and the air temperature is $50^{\circ}C$. This environment is inappropriate for workers and instruments. Workers adjacent to the deaerator and storage tank in particular feel higher temperatures because of the radiative heat transfer effect. Therefore, we optimized the cooling conditions by computational analysis. Case 1 is the current shape of the power plant, Case 2 has additional insulation, and Case 3 has a radiation shield. Flow is caused by a temperature difference between the heat sources in the wall, and hot air is trapped in the right upper end. Based on the temperature contours and the maximum temperature of the surfaces, Case 2 was found to be the most efficient for reducing radiative heat transfer effects.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.4
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• pp.28-35
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• 2012

Recently, as the social interest increase has been focused on new renewable energy system to build-up sustainable urban planning system, the related studies have been actively conducting. As well as in other areas, the construction area, which accounts for over 40% of the total energy consumption, clearly showed this tendency. Whereas, various landscape facilities applying renewable energy equipments have been manufactured and installed, systematic study available for planning and designing is rarely found in Korea. This study is expected to contribute to the landscape planning and designing by quantifying the energy-efficient and economic advantages of the renewable energy system for landscape facilities. For this purpose, the analysis on the energy-efficiency and economic values under the scenario that the current fossil power supply for the streetlights in urban parks in Seoul, Daegu, and Incheon were replaced by photovoltaic power generation were performed through RETScreen$^{(R)}$ a clean energy simulation program based on the NASA Satellite Meteorological Data. As a result, the generated power and the economic values vary depending on the climatic features of the appointed cities. This study will be used to build up the effective decision-making in applying the clean renewable system to the plan and design of landscaping.

• Composites Research
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• v.32 no.6
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• pp.301-306
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• 2019

Triboelectric nanogenerator (TENG) is one of the energy harvesting methods in spotlight that can convert mechanical energy into electricity. As TENGs produce high electrical output, previous studies have shown TENGs that can power small electronics independently. However, recent studies have reported limitations of TENG due to air breakdown and field emission. In this study, we developed a triboelectric nanogenerator that utilizes the metal-to-metal surface contact to induce ion-enhanced field emission and electron avalanche for electrons to flow directly between two electrodes. The average peak open-circuit voltage of this TENG was measured as 340 V, and average peak closed-circuit current was measured as 10 mA. The electrical output of this TENG has shown different value depending on the surface charge of surface charge generation layer. The TENG developed in this study have produced RMS power of 0.9 mW, which is 2.4 times higher compared to conventional TENGs. The TENG developed in this study can be utilized in charging batteries and capacitors to power portable electronics and sensors independently.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.9
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• pp.71-80
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• 2007

This paper presents a new push-push VCO technique that extracts a second harmonic output signal from a capacitive commonnode in a negativegm oscillator topology. The generation of the $2^{nd}$ harmonics is accounted for by the nonlinear current-voltage characteristic of the emitter-base junction diode causing; 1) significant voltage clipping and 2) different rising and falling time during the switching operation of core transistors. Comparative investigations show the technique is more power efficient in the high-frequency region that a conventional push-push technique using an emitter common node. Prototype 12GHz and 17GHz MMIC VCO were realized in GaInP/GaAs HBT technology. They have shown nominal output power of -4.3dBm and -5dBm, phase noise of -108 dBc/Hz and -110.4 dBc/Hz at 1MHz offset, respectively. The phase noise results are also equivalent to a VCO figure-of-merit of -175.8 dBc/Hz and -184.3 dBc/Hz, while dissipate 25.68mW(10.7mA/2.4V) and 13.14mW(4.38mA/3.0V), respectively.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.125-135
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• 1993

The safe and efficient operation of nuclear plants is recognized to be accomplished through the application of plant automation using digital technology, which is one of main targets of the next generation nuclear plants. For plant level automation, it is first required that each major subsystem be digitalized, and the steam generator water level control system is discussed in this study. The transfer functions between inputs and the level are derived by employing the thermal hydraulic model of the steam generator and are applied to the analysis of the current three-element control system. Since the control scheme in this study includes the steam generator itself as a process plant, the system order is high and the numerical instability arises in digitalizing. Together with this, the unreliability of the feedwater feedback signal at low power level leads to the proposal of a two-element control system with a proper digital controller. The digital PI controller developed for this system has the initial power adaptive gain and integration time constant. And it makes the overall system response satisfy the stability and other necessary control specifications simultaneously. Since the two-element control system using this controller depends on the initial power only, it is simple to define and it shows a similar level response behavior to that of its corresponding analog system.

• Journal of computational fluids engineering
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• v.10 no.3 s.30
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• pp.9-18
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• 2005

During a hypothetical severe accident in a nuclear power plant (NPP), hydrogen is generated by the active reaction of fuel-cladding and steam in the reactor pressure vessel and released with steam into the containment. In order to mitigate hydrogen hazards possibly occurred in the NPP containment, hydrogen mitigation system (HMS) is usually adopted. The design of the next generation NPP (APR1400) designed in Korea specifies 26 passive autocatalytic recombiners and 10 igniters installed in the containment for the hydrogen mitigation. in this study, the analysis of the hydrogen and steam behavior during a total lose of feed water (TLOFW) accident in the APR1400 containment has been conducted by using the CFD code GASFLOW. During the accident, a huge amount of hot water, steam, and hydrogen is released in the in-containment refueling water storage tank (IRWST). The current design of the APR1400 includes flap-type dampers at the IRWST vents which are operated depending on the pressure difference between inside and outside of the IRWST. it was found that the flaps strongly affects the flow structure of the steam and hydrogen in the containment. The possibilities of a flame acceleration and transition from deflagration to detonation (DDT) were evaluated by using Sigma-Lambda criteria. Numerical results indicate the DDT possibility could be heavily reduced in the IRWST compartment when the flaps are installed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1532-1539
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• 2017

The floating photovoltaic system is a new concept in the renewable energy technology. That is similar to land based photovoltaic technology except floating system. So the system needs buoyant objects, mooring, ect, besides modules and supports, and that is able to withstand in water level changes and wind strength. Therefore the floating photovoltaic system is much different from land photovoltaic system. K-water (Korea Water Resources Corporation) has been operating two floating photovoltaic system that's capacity is 100 kW and 500 kW respectively since in summer 2011 for commercial generation, and have construction project for 2,000 kW in Boryeong multipurpose Dam and other areas. Furthermore K-water was developing a tracking-type floating photovoltaic system at Daecheong multipurpose Dam and developed and installed an ocean floating photovoltaic demonstration plant at Sihwa Lake in October 2013 for R&D. In this paper, we introduce that structure of floating photovoltaic system include buoyant structure, mooring system and auxiliary device. Especially the rope which is in part of mooring should be always maintain tension under any water level. Also we explain about structure design concept to wind load in an every loading condition and a kind of structure materials and PV structure types used in water environment. Especially ocean floating PV system is affected by tidal current and typhoon. So there are considering the elements in design. Finally we compare with floating and land photovoltaic on power amount. As a result of that we verified the floating photovoltaic system is more about 6.6~14.2 % efficiency than a general land photovoltaic system.