• Atmosphere
• /
• v.27 no.3
• /
• pp.331-344
• /
• 2017

Solar energy is calculated using high-resolution digital elevation model (DEM). In focus on Seoul metropolitan area, correction coefficients of direct and diffuse solar energy with the topographic effect are calculated from DEM with 1720, 900, 450, 90 and 30 spatial resolutions ($m{\times}m$), respectively. The solar energy on the real surface with high-resolution is corrected using by the correction coefficients with topographic effect from the solar energy on horizontal surface with lower resolution. Consequently, the solar energy on the real surface is more detailed distribution than those of horizontal surface. In particular, the topographic effect in the winter is larger than summer because of larger solar zenith angle in winter. In Seoul metropolitan area, the monthly mean topographic effects are more than 200% in winter and within 40% in summer. And annual topographic effects are negative role with more than -60% and positive role with below 40%, respectively. As a result, topographic effect on real surface is not a negligible factor when calculating and analyzing solar energy using regional and global models.

• KIEAE Journal
• /
• v.14 no.2
• /
• pp.37-46
• /
• 2014

University buildings are energy-guzzling facility that consume more than 10,000TOE within a campus annually. Even the consumption is on an upswing trend. Behind such high consumption are there cheap power rates for education facility, lack of high-efficiency equipment and ever-increasing use of various information equipment. Being keenly aware that greenhouse gas emission increases due to such rise of energy consumption, the present study carried out a case study. In the case study, the study chose the buildings of E university from top 10 universities that consume energy most in Seoul and examined the current status of their energy consumption and greenhouse gas emission. And then it set the reduction target of greenhouse gas by year. Putting aside a middle and long-termed strategy for later endeavor, it first established the 1st year's implementation plan (2014) for energy saving and greenhouse gas reduction with limited budget and according to greenhouse gas reduction target. The plan is specified as follows. Targets for energy saving are mainly divided into two sectors: machine equipment and electric equipment. 7 ideas were proposed. Three ideas to improve machine equipment are to replace with high-efficiency boilers and chillers and to adjust the position of the cooling tower. By doing so, it was estimated that energy could be saved by 176.34TOE in total and greenhouse gas could be reduced by 370.771t$CO_2$-eq. Four ideas to improve electric equipment include the replacement with LED lights, LED emergency lights and high-efficiency motors and the installation of motion sensors. It was calculated that such replacement could conserve 1,076.08TOE (electric energy) and reduce 2,181.420t$CO_2$-eq (greenhouse gas).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.8
• /
• pp.797-802
• /
• 2012

In this study, the potential performance enhancement in a dual heat pump system through series operation was investigated by a comparison between the performance for parallel and series operation for a heating supply temperature of $60^{\circ}C$. To compare the performance of each configuration fairly, the heat transfer surface area of the heat exchangers was fixed. The inlet temperatures and the flow rates of the heat source and the load were also fixed. In addition, the heat transfer and pressure drop characteristics of the working fluids were considered to achieve a more realistic comparison. The results show that the heating coefficient of performance (COP) of the series configuration is approximately 5% higher than that of the parallel configuration under the simulation conditions considered in the present study.

• Transactions of the Korean hydrogen and new energy society
• /
• v.25 no.4
• /
• pp.393-404
• /
• 2014

Unmanned aerial vehicles (UAVs) have been applied to not only military missions like surveillance and reconnaissance but also commercial missions like meteorological observation, aerial photograph, communication relay, internet network build and disaster observation. Fuel cells make UAVs eco-friendly by using hydrogen. Proton exchange membrane fuel cells (PEMFCs) show low operation temperature, high efficiency, low noise and high energy density and those characterisitcs are well fitted with UAVs. Thus Fuel cell based UAVs have been actively developed in the world. Recently, fuel cell UAVs have started to develope for high altitude UAVs because target altitude of UAVs is expanded upto stratosphere altitude. Long endurance of UAVs is essential to improve effects of the missions. Improvement of UAV endurance time could be fulfilled by developing a hydrogen fuel storage system with high energy density and reducing the weight of UAVs. In this paper, research trend and analysis of fuel cell UAVs are introduced in terms of their altitude and endurance time and then the prospect of fuel cell UAVs are shown.

• Korean Journal of Remote Sensing
• /
• v.15 no.4
• /
• pp.289-295
• /
• 1999

Space Physics Sensor (SPS) on-board the KOMPSAT-1 consists of the High Energy Particle Detector (HEPD) and the Ionospheric Measurement Sensor (IMS). The HEPD is to characterize the low altitude high energy particle environment and the effects on the microelectronics due to these high energy particles. It is composed of four sensors: Proton and Electron Spectrometer(PES), Linear Energy Transfer Spectrometer (LET), Total Dose Monitor (TDM), and Single Event Monitor (SEM). 35 MeV proton beam from the medical KCCH cyclotron, at Korea Cancer Center Hospital in Seoul, is used to calibrate the PES. Primary proton beam of 35MeV scattered by polypropylene target is converted to various energy protons according to the elastic collision kinematics. In this calibration, the threshold level of the proton in the PES can be determined and the energy ranges of PES channels are also calibrated.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.61 no.3
• /
• pp.116-121
• /
• 2012

Recently, in the field of renewable energy such as solar cells including the semiconductor and display industries, thin film deposition process is being diversified. Furthermore, to deal with trend of making high-quality and fast, the high-capacity and output plasma power supply which can control high density plasma is required. The biggest problem is arc discharge caused by using high voltage power supply. Thus, the key function of plasma power supply is to prevent arc discharge and there is a need to maintain the possible minimum arc energy. In DC sputtering power supply, on a periodic basis (-)voltage powering up is able to significantly reduce arcing, as well as arc discharge prevention, and maintaining uniform charge density. This conventional method for powering up (-)voltage requires heavy mutual inductance of the transformer to avoid distortion problem of the output voltage. This study is about energy recovery circuit for arc discharge prevention in sputtering plasma power supply. By using energy recovery circuit, it is possible to reduce the mutual inductance and size of the transformer dramatically, prevent distortion of the output voltage and has a stable output waveform. This work was proved through simulation and experimental study.

• The Korean Journal of Ecology
• /
• v.8 no.3
• /
• pp.153-161
• /
• 1985

Energy flow through the trophic levels was studied at a salt marsh ecosystem distinguished into low and high marsh. Gross primary productions of Suaedeto-Salicornietum and Artemisieto-Limonietum at low marsh were 8, 299 and 13, 154kca/$m^2$/yr, and those of Calama-grostetum and Sonchuso-Setaetum at high marsh were 17, 899 and 15, 177kca/$m^2$/yr, respectively. Efficiencies of solar energy utilization of plants were 1.7 and 2.6% at the former, and were 3.6 and 3.2% at the latter. Of gross productions, net primary productions were 3, 977 and 5, 280kca/m2/yr at low marsh and were 6, 354 and 5, 329kca/$m^2$/yr at high marsh, and the remainder, 52~67%, was consumed by respiration of plants. A small amount (0.03~0.04%) of the net primary production was flowed through grazing food chain and most amout was transferred into dead parts. Of dead parts, 40% was accuulated as litter and the rest was decomposed into detritus. In the detritus food chain, a little energy was utilized by detritus feeder, and a major by microorganism. The amounts of energy flowed through grazing and detritus feeders at high marsh were much more than those at low marsh, but tertary production as spider was Vice versa.

• Progress in Superconductivity
• /
• v.9 no.1
• /
• pp.74-79
• /
• 2007

We characterized the highly refined boron precursor powders which were attrition milled for different milling times. $MgB_2$ powder precursor was formed from elemental crystalline Mg and amorphous B powder. The microstructure was investigated by SEM. SEM results indicate that the size of the milled powders was reduced with increasing milling time, which were varied from 0 to 8 hours. We also studied thermal behavior of the starting precursor by DSC as a function of milling time. The thermal behavior of the powder precursors was influenced by milling time. In order to determine the thermal events at DSC peaks, we annealed the milled powder mixture at $600^{\circ}C$ and $650^{\circ}C$ under protective gas and then analyzed the formation of $MgB_2$ by the XRD. We observed that superconducting $MgB_2$ phase was formed at lower temperature by the longer high energy milling. These results show that the high energy milling of the boron precursor powder can improve the reactivity for the formation of $MgB_2$.

• Nuclear Engineering and Technology
• /
• v.41 no.8
• /
• pp.1109-1114
• /
• 2009

The evolution of a high burnup structure (HBS) in a light water reactor (LWR) $UO_2$ fuel was simulated using the Potts model. A simulation system for the Potts model was defined as a two-dimensional triangular lattice, for which the stored energy was calculated from both the irradiation damage of the $UO_2$ matrix and the formation of a grain boundary in the newly recrystallized small HBS grains. In the simulation, the evolution probability of the HBS is calculated by the system energy difference between before and after the Monte Carlo simulation step. The simulated local threshold burnup for the HBS formation was 62 MWd/kgU, consistent with the observed threshold burnup range of 60-80 MWd/kgU. The simulation revealed that the HBS was heterogeneously nucleated on the intergranular bubbles in the proximity of the threshold burnup and then additionally on the intragranular bubbles for a burnup above 86 MWd/kgU. In addition, the simulation carried out under a condition of no bubbles indicated that the bubbles played an important role in lowering the threshold burnup for the HBS formation, thereby enabling the HBS to be observed in the burnup range of conventional high burnup fuels.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.6
• /
• pp.610-619
• /
• 2000

This paper presents an off-line UPS using the high temperature superconductive magnetic bearing. FES(Flywheel Energy Storage) system has good advantages in compare with lead acid battery. So, high efficiency FES using high temperature SMB(superconductive magnetic bearing) was composed in this paper. The outer rotor type of PMSM(Permanent Magnet Synchronous Motor) as motor/generator was used for the experiment, and square wave current and sinusoidal wave control methods was compared for high efficiency operation of motor/generator. The circuit for in phase sinusoidal wave current control with EMF in the full speed range was designed and the proposed flywheel energy storage system was applied in single phase off-line UPS system. As the stable operation characteristics of prototype system was confirmed, the its excellence as energy storage device in Off-line UPS was proved.