• Title/Summary/Keyword: Wind Generation

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The Design and Experiment of Piezoelectric Energy-Harvesting Device Imitating Seaweed (해조류를 모방한 압전 에너지 수확 장치의 설계와 실험)

  • Kang, Tae-Hun;Na, Yeong-Min;Lee, Hyun-Seok;Park, Jong-Kyu;Park, Tae-Gone
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.4
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    • pp.73-84
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    • 2015
  • Electricity generation using fossil fuels has caused environmental pollution. To solve this problem, research on new renewable energy sources (solar, wind power, geothermal heat, etc.) to replace fossil fuels is ongoing. These devices are able to generate power consistently. However, they have many weaknesses, such as high installation costs and limits to possible setup environments. Therefore, an active study on piezoelectric harvesting technology that is able to surmount the limitations of existing energy technologies is underway. Piezoelectric harvesting technology uses the piezoelectric effect, which occurs in crystals that generate voltage when stress is applied. Therefore, it has advantages, such as a wider installation base and lower technological costs. In this study, a piezoelectric harvesting device imitating seaweed, which has a consistent motion caused by fluid, is used. Thus, it can regenerate electricity at sea or on a bridge pillar, which has a constant turbulent flow. The components of the device include circuitry, springs, an electric generator, and balancing and buoyancy elements. Additionally, multiphysics analysis coupled with fluid, structure, and piezoelectric elements is conducted using COMSOL Multiphysics to evaluate performance. Through this program, displacement and electric power were analyzed, and the actual performance was confirmed by the experiment.

Investigating the Power-Performance Prediction on an H- and Helical-type Tidal Current Turbine Using CFD Method (CFD에 의한 H 및 Helical 타입 조류발전용 터빈의 출력성능예측에 관한 연구)

  • Kim, Bum Suk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.8
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    • pp.653-660
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    • 2015
  • In this study, we conduct power performance and load analyses of two different types of vertical-axis tidal-current turbines using the computational fluid dynamics (CFD) method. To analyze the power output and loads, we perform transient CFD simulations considering the cavitation model using ANSYS CFX. The averaged power output of an H-type rotor was 7.47 kW and 67.6 kW in normal and extreme operating conditions, respectively, which did not satisfy the initial design conditions. However, in the case of the helical-type rotor, the power output under normal and extreme conditions were close to the expected values. The cavitation, which may cause instantaneous power fluctuation, occurred repeatedly at the suction side of the rotors. In order to guarantee a more stable power supply and to prevent fatigue failure, we require a design that minimizes cavitation.

The Generation of Typical Meteorological Year for Research of the Solar Energy on the Korean Peninsula (한반도 태양에너지 연구를 위한 일사량 자료의 TMY 구축)

  • Jee, Joon-Bum;Lee, Seung-Woo;Choi, Young-Jean;Lee, Kyu-Tae
    • New & Renewable Energy
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    • v.8 no.2
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    • pp.14-23
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    • 2012
  • The TMY (Typical Meteorological Year) for the solar energy study is generated using observation data with 22 solar sites from KMA (Korea Meteorological Administration) during 11 years (2000-2010). The meteorological data for calculation the TMY are used solar radiation, temperature, dew point temperature, wind speed and humidity data. And the TMY is calculated to apply the FS (Finkelstein and Schafer) statistics and RMSE (Root Mean Squared Error) methods. FS statistics performed with each point and each variable and then selected top five candidate TMM months with statistical analysis and normalization. Finally TMY is generated to select the highest TMM score with evaluation the average errors for the 22 whole points. The TMY data is represented average state and long time variations with 22 sites and meteorological data. When TMY validated with the 11-year daily solar radiation data, the correlation coefficient was about 0.40 and the highest value is 0.57 in April and the lowest value is 0.23 in May. Mean monthly solar radiation of TMY is 411.72 MJ which is 4 MJ higher than original data. Average correlation coefficient is 0.71, the lowest correlation is 0.43 in May and the highest correlation is 0.90 in January. Accumulated annual solar radiation by TMY have higher value in south coast and southwestern region and have relatively low in middle regions. And also, differences between TMY and 11-year mean of is distributed lower 100 MJ in Kyeongbuk, higher 200 MJ in Jeju and higher 125 MJ in Jeonbuk and Jeonnam, respectively.

Utilization of Energy in the Sea Water of the Southeastern Yellow Sea (한국남서해의 열 에너지 이용)

  • 장선덕
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.14 no.2
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    • pp.113-116
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    • 1978
  • To ascertain the feasibility of the energy utilization in the sea adjacent to Korea, the distribution of the vertical temperature difference and the seasonal variation in the southeastern Yellow Sea are studied in relation to the sea water circulation. In summer, a region of high vertical temperature difference of approximately 16$^{\circ}C$ was found at a distance of approximately 40 miles from the western coast of Korea. It is located at the west of 125${\circ}$ 30`E and at the north of 34${\circ}$N. The vertical temperature structure is sustained by the inflow of Yellow Sea Warm Current water, the warming of the surface water of the Yellow Sea and the periodical renewal of the Yellow Sea Cold Water. It may be stated that power can be obtained from the sea water by making the use of the temperature difference. The vertical temperature difference was around 14$^{\circ}C$ in the western and southern waters of Jejudo Island. The vertical temperature difference decreases in autumn, and disappears due chiefly to the vigorous convective vertical mixing in winter when the northwest monsoon prevails. The power can be obtained from sea throughout the year, if power generation by the temperature difference is combined with that by wind and wave, and systemized in such a way that the former is employed in the hot season of summer, while the latter in winter and spring.

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TOWARD A NEXT GENERATION SOLAR CORONAGRAPH: DIFFRACTED LIGHT SIMULATION AND TEST RESULTS FOR A CONE OCCULTER WITH TAPERED SURFACE

  • Yang, Heesu;Bong, Su-Chan;Cho, Kyung-Suk;Choi, Seonghwan;Park, Jongyeob;Kim, Jihun;Baek, Ji-Hye;Nah, Jakyoung;Sun, Mingzhe;Gong, Qian
    • Journal of The Korean Astronomical Society
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    • v.51 no.2
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    • pp.27-36
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    • 2018
  • In a solar coronagraph, the most important component is an occulter to block the direct light from the disk of the sun. Because the intensity of the solar outer corona is $10^{-6}$ to $10^{-10}$ times of that of the solar disk ($I_{\odot}$), it is necessary to minimize scattering at the optical elements and diffraction at the occulter. Using a Fourier optic simulation and a stray light test, we investigated the performance of a compact coronagraph that uses an external truncated-cone occulter without an internal occulter and Lyot stop. In the simulation, the diffracted light was minimized to the order of $7.6{\times}10^{-10}I_{\odot}$ when the cone angle ${\theta}_c$ was about $0.39^{\circ}$. The performance of the cone occulter was then tested by experiment. The level of the diffracted light reached the order of $6{\times}10^{-9}I_{\odot}$ at ${\theta}_c=0.40^{\circ}$. This is sufficient to observe the outer corona without additional optical elements such as a Lyot stop or inner occulter. We also found the manufacturing tolerance of the cone angle to be $0.05^{\circ}$, the lateral alignment tolerance was $45{\mu}m$, and the angular alignment tolerance was $0.043^{\circ}$. Our results suggest that the physical size of coronagraphs can be shortened significantly by using a cone occulter.

Boundary Layer Correction of Hypersonic Wind-tunnel Nozzle Designed by the Methods of Characteristics (특성곡선 해법 설계 극초음속 노즐의 경계층 보정)

  • Kim, So-Yeon;Kim, Sung Don;Jeung, In-Seuck;Lee, Jong-Kuk;Choi, Jeong-Yol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.12
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    • pp.1028-1036
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    • 2014
  • A design procedure is established for hypersonic nozzles by using MOC(Method of Characteristics) and CFD. The inviscid nozzle contour is designed by MOC, then BLC(Boundary Layer Correction) is made by evaluating the boundary layer thickness from viscous CFD analysis. By comparing various definitions of the boundary layer thicknesses, it seems that the boundary layer thickness of 95% speed of the maximum value at the cross section satisfies best the design Mach number. Design procedure is as follow; MOC design, grid generation, inviscid analysis, viscous analysis, BLC and viscous analysis for confirmation and post-processing. All procedures are made automatically by using the batch processing.

Seasonal Variation and Statistical Analysis of Particulate Pollutants in Urban Air (도시대기립자상물질중 오염성분의 계절적 변동 및 통계적 해석)

  • 이승일
    • Journal of environmental and Sanitary engineering
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    • v.9 no.2
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    • pp.8-23
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    • 1994
  • During the period from Mar., 1991 to Feb., 1992 66 tSP samples were collected by Hi volume air sampler at 1 sampling site in Seoul and the amount of concentration of 21 components(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Al, Ba, Ca, Cd, Cr, Cu, Fe, It Mg, Mn, Na, Ni, Pt Si, Ti, Zn, Zr ) were measured. And monthly and seasonal variation were surveyed and the principal component analysis( PCA ) were carried out with respect to these amount of pollutants, minimum of visibility and radiation on a horizontal surface. The total amount of soluble ion in water was high in order o(SO$_{4}$$^{2-}$> NO$_{3}$$^{-}$> N%'>Cl$^{-}$ and metal ion was high in order of Na> Ca>Si> Fe> Al> K> Mg> Zn> Pb> Cu>Ti> Mn > Ba> Cr> Zr> Ni> Cd. There was Seasonal variation in concentration for SO$_{4}$$^{2-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Na, Al, Ca, Bt Mg, Fe and Si. It was assumed that the components of the highest concentration on April were depend on yellow sand and the frequency of wind velocity and direction. As the results of PCA, the amount of pollution components was able to characterized with two principal components(Z$_{1}$, Z$_{2}$ ). The first principal components Z$_{1}$ was considered to be a factor indicating the pollutants originated from natural generation and The second principal components Z$_{2}$ was considered to be a factor indicating the pollutants originated from human work. The monthly concentration of pollutants in ISP, minimum of visibility and radiation on a horizontal surface was possible to evaluate by the use of these two principal components Z$_{1}$ and Z$_{2}$ .

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Study on the Confidential Document of A Distinguished Medical Family (기문비록(岐門秘錄)에 대한 고찰)

  • Kim, Dong-Min;Choi, Kyung-Suk;Shin, Seung-Yuel;Ahn, Jun-Mo;Keum, Kyung-Soo;Lee, Si-Hyeong
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.22 no.5
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    • pp.1078-1105
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    • 2008
  • An empirical formula that has been empirically shown to be effective for a particular condition can be said to add medicinal materials to an existing formula or to make a new prescription by the Korean medical doctors' empirical clinic. This dissertation aims to study the prescriptions according to A Confidential Document of A Distinguished Medical Family written by the writer's ancestor and to contribute to the development of Korean medicine. A Confidential Document of A Distinguished Medical Family is a medicinal recipe that is an heirloom of the Gyeongju Kim family for the eighth generation. And the date and the writer of the book are unknown. The contents of the book consist of 18 parts and are made up of about 300 medical recipes. Of these, 158 formulas and indications of cold damage, wind, urination, stool, jaundice, and internal injury are found in the book. From among these, 61 formulas was directly quoted out of The Precious Mirror of Oriental Medicine, 97 formulas are adjusted in proportion or combined. By the parity of reasoning of the above, I think that this book was published after The Precious Mirror of Oriental Medicine. I will continue to study other formulas except the formulas above mentioned.

A study on Optimal Operation of Protection Coordination Devices Evaluation System in Distribution System with Distributed Sources (분산전원이 연계된 배전계통에 보호협조기기 평가시스템의 최적운용에 관한 연구)

  • Ji, Sungho;Song, Bangwoon;Kim, Byungki;Rho, Daeseok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.6
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    • pp.2971-2978
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    • 2013
  • Recently, with the world-wide issues about global warming and CO2 reduction, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with the distribution systems. However, DGs can change the direction of the power flow from one-direction to bi-direction, and also change the direction and amount of fault current of existing distribution systems. Therefore, it may cause the critical problems on the power quality and protection coordination. This paper proposes an operation algorithm for bi-directional protection coordination using and apply it for the evaluation system for protection coordination. From the simulation results It is found that the proposed method is more effective and convenient than existing method.

Genetic Diversity and Population Structure of Chimaphila japonica in Southern Part of Korea (한국 남부지역의 매화노루발의 유전적 다양성과 집단구조)

  • Joo-Soo Choi;Man-Kyu Huh
    • Journal of Life Science
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    • v.8 no.6
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    • pp.687-694
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    • 1998
  • Enzyme electrophoresis was used to estimate genetic diversity and population structure of Chimaphila japonica Miq. in Korea. The percent of polymorphic loci within the enzymes was 48.7%. Genetic diversity at the species level and at the population level was high (Hes=0.278 ; Hep=0.222, respectively), whereas the extent of the population divergence was relatively low ( $G_{ST}$ =0.079). $F_{IS}$ , a measure of the deviation from random mating within the 7 populations, was 0.355. An indirect estimate of the number of migrants per generation (Nm=2.61) indicates that gene flow is high among Korean populations of the species. In addition, analysis of fixation indices revealed a substantial heterozygosity deficiency in some populations and at some loci. Factors contributing to the high levels of genetic dive-rsity found in the entire species of C. japonica include wide distribution, long-lived perennials, ability to regenerate due to rhizomatous spread, outcrossing induced by animal vectors, and occasional pollen dispersal by wind.

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