• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.72-79
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• 2015

Electricity can be generated when the natural gas passes through a turbo-expander pressure reduction system at natural gas pressure reduction stations. Efficiency of the turbo-expander depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. Therefore, the optimal conditions for the operation of the pressure reduction system can be determined by controlling the natural gas flow rates. In this study, we have calculated the electric energy generation depending on the natural gas flow rates at the two low-pressure reduction stations when the pressure of the natural gas is reduced from 17.5 bar to 8.5 bar and have found the optimal conditions for the turbo-expander pressure reduction system through the comparison with the calculation results. The turbo-expander generates the electric power efficiently for the high natural gas flow rates which variations are slight. The determined design flow rate of the turbo-expander has the highest coverage of the natural gas flow rates. The electricity generation is calculated as much as 9 MW(B station) and 12 MW(D station) at each pressure reduction station.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.216-220
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• 2012

본 연구는 경기도 용인시에 위치한 공공하수처리장을 대상으로 소수력발전 성능특성을 예측하고 경제성을 분석하여 소수력발전소의 건설타당성을 제시하였다. 방류구에서의 수준측량 조사에 따르면 실제 유효 낙차는 4.3m로 나타났다. 최근 5년간 방류량 자료를 살펴보면 일평균 실제 처리량은 약 $30,000m^3/day$로 나타났으며, 우수 유입과 물 사용량이 증가하는 여름 및 가을에 처리량이 증가하였다. 설계유량은 유량변화에 따른 누적 확률밀도와 유량지속곡선에 근거해 산정하였으며, 시간빈도로 보았을 때 17%의 유량이 지속되는 $0.35m^3/sec$가 설계유량으로 나타났다. 예상되는 수차 발전용량은 11kW급이며, 시스템 가동율은 74%, 그리고 계통선에 송출될 수 있는 연 전력생산량은 71.3MWh로 나타났다. 경제성 평가는 신재생에너지 경제성 분석 도구인 RETScreen 프로그램을 사용하여 B/C ratio, IRR, 개발투자비 등의 경제성 평가지표들을 산정하였다. 편익(Benefit) 산정시 전력기준단가는 133.67원/kWh, 할인율 7%를 적용하였으며, 비용(Cost) 산정시 유지관리비는 초기 건설비의 1%, 사용연한 30년을 적용하였다. 경제성 분석결과 기흥레스피아의 소수력발전소 건설시 초기 건설공사비가 $165,000 일 때, B/C 1.0, NPV $3,534, 투자회수기간 15.1년으로 산정되었고 따라서 초기 건설비용이 $165,000 이하일 때 가장 경제적인 것으로 파악되었다.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.675-680
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• 2012

Wind energy is currently the fastest growing source of renewable energy used for electrical generation around the world. Wind farms are adding a significant amount of electrical generation capacity. The increase in the number of wind farms has led to the need for more effective operation and maintenance. CMS(Condition Monitoring System) can be used to aid plant operator in achieving these goals. Its aim is to provide operators with information regarding th e health of their machine, which in turn, can help them improve operation efficiency. In this work, wind turbine fault diagnostic algorithm which can diagnose the mass unbalance and aerodynamic asymmetry of the blades is proposed. Proposed diagnostic algorithm utilizes both FFT(Fast Feurier Transform) of the signal from accelerometers installed inside of nacelle and simple diagnostic logic. Furthermore, to verify the applicability of the proposed system, 3W small sized wind turbine system is tested and physical experiments are carried out.

• Resources Recycling
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• v.28 no.5
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• pp.30-41
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• 2019

Global production of zinc is about 13 million tons and zinc is the fourth-most widely used primary metal in the world following iron, aluminum and copper. When zinc is recycled to produce secondary zinc, it can save about 75 % of the total energy that is needed to produce the primary zinc from ore, and in therms of $CO_2$ emissions reduced by about 40 %. However, since zinc is mainly used for galvanizing of steel, the recycling rate of zinc is about 25 %, which is lower than other metals. The raw materials for recycling of zinc include dusts generated in the production of steel and brass, sludge in the production process of non-ferrous metals, dross in the melting of zinc ingots or hot dip galvanizing, waste batteries, and metallic scrap. Among them, steelmaking dust and waste batteries are most actively recycled up to now. Most of the recycling process uses pyrometallurgical methods. Recently, however, much attention has been given to a combined process of pyrometallurgical and hydrometallurgical processes.

• Journal of the Korean Institute of Gas
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• v.25 no.4
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• pp.19-26
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• 2021

In this paper, we carried out the process modelling and economical analysis of the 500 kg-H₂/d-class green hydrogen production system process based on biomethane from the Food Bio Energy Center in Chungju. As a result of economic analysis, the NPV(Net present value) after 15 years of operation is 3.831 billion won, the PI(Profitability index method) is 1.42. It was found that the project of 500 kg-H₂/d-class green hydrogen production system has a 20.25% of IRR, which is higher than social discount rate of 4.5% and feasibility is ensured.

• Resources Recycling
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• v.28 no.4
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• pp.3-14
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• 2019

Lead is one of the common non-ferrous metals used in modern industry. The usage of lead continues to increase and has risen from 5 million tonnes per year worldwide in the 1970s to 11 million tonnes in the 2010s. In principle lead is virtually 100 % recyclable as an element without loss of quality. The recycling of lead scrap reduces the energy consumption and environmental burden, comparing to the primary metal production. Therefore production of secondary lead from scrap has been steadily growing and at present it meets approximately 60 % of usage worldwide. Lead scrap (mainly lead-acid battery) is smelted in primary and secondary smelter. Most secondary lead smelting were performed in a shaft-type furnace (blast furnace), rotary furnace and reverberatory furnace. The lead bullion is either cast into ingots and re-melted in refining kettles or refining is performed on the hot lead bullion immediately after production. This work provides an overview of the primary lead production and recycling process.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.1
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• pp.15-26
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• 2008

The NEMURO model is aimed to efficiently understand the interaction among factors of lower trophic level of a marine ecosystem, using data on solar radiation and sea water temperature. In this study, we analyzed the seasonal pattern of nutrients and planktons, and estimated productivity and biomass of planktons from 2002 to 2005. Nutrients($NO_3$, $NH_4$, and $Si(OH)_4$) which were used by phytoplankton showed a high concentration before the bloom of phytoplankton. Nutrients (DON, PON, and Opal) which were a byproduct of phytoplankton showed a high concentration in the same period as the bloom of phytoplankton. Both phytoplankton and zooplankton had two peaks in March and August. Estimated phytoplankton biomass from the NEMURO model showed a similar pattern with observed chlorophyll a concentrations. Biomasses of phytoplankton were bigger than those of zooplankton. Annual mean biomasses of small and large phytoplankton were estimated at 30.961 and $14.070\;{\mu}g\;l^{-1}$ respectively. Annual mean biomass of predatory zooplankton was greater than those of small and large zooplankton.

• Korean Journal of Environmental Agriculture
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• v.30 no.1
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• pp.24-30
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• 2011

BACKGROUND: High input to the arable land is contributed to increasing productivity with causing the global environmental problems at the same time. Rapeseed cultivation has been forced to reassess its positive point for utilization of winter fallow field. The Objective of this study was performed to assess the environmental impact of rapeseed cultivation with double-cropping system in paddy rice on Yeonggwang district using life cycle assessment technique. METHODS AND RESULTS: For assessing each stage of rapeseed cultivation, it was collected raw data for input materials as fertilizer and pesticide and energy consumption rate by analyzing the type of agricultural machinery and working hours by 1 ton rapeseed as functional unit. Environmental impacts were evaluated by using Eco-indicator 95 method for 8 impact categories. It was estimated that 216 kg $CO_2$-eq. for greenhouse gas, 3.98E-05 kg CFC-11-eq. for ozone lazer depletion, 1.78 kg SO2-eq. for acidification, 0.28 kg $PO_4$-eq. for eutrophication, 5.23E-03 kg Pb-eq. for heavy metals, 2.51E-05 kg B(a)p-eq. for carcinogens, 1.24 kg SPM-eq. for smog and 6,460 MJ LHV for energy resource are potentially emitted to produce 1 ton rapeseed during its whole cultivation period, respectively. It was considered that 90% of these potential came from chemical fertilizer. For the sensitivity analysis, by increasing the productivity of rapeseed by 1 ton per ha, potential environmental loading was reduced at 22%. CONCLUSION(s): Fertilization affected most dominantly to the environmental burden, originated from the preuse stage, i.e. fertilizer manufacturing and transporting. It should be included and assessed an indirect emission, which is not directly emitted from agricultural activities. Recycling resource in agriculture with reducing chemical fertilizer and breeding the high productive variety might be contribute to reduce the environmental loading for the rapeseed cultivation.

• Journal of Korea Foresty Energy
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• v.21 no.1
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• pp.65-75
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• 2002

The study was carried out to determine the growth and biomass production of major deciduous trees including Betula platyphylla var. japonica, Betula schmidtii, Zelkova serrata, Acer mono, Prunes sargentii, and Ligustrum obtusifolium subjected to artificial shade treatment in nursery field. The six deciduous trees seedlings grow for 2 years under different light intensity of 100%, 38-62%, 22-28%, 7-20%, and 2-6% of the full sun light intensity. The results were as follows; In the seedling heights and root collar diameters of shade intolerant species like Betula platyphylla var. japonica and Betula schmidtii, the relative growth rates of seedlings grown in full sun showed 2 times as compared with those subjected to the shade treatment of 2-6% light intensities of full sun. In the shade tolerant species like Acer mono ant Ligustrum obtusifolium, the growth performances were better in the seedlings grown in 38-62% light intensities of full sun. Total dry mass including the dry mass of leaves, shoot and root were as a whole decreased with shade treatment. The ratio of the dry mass of leaves and stem increased the dry mass of root. T/R ratio of the seedlings increased by decreasing the relative light intensity. And the T/R ratio of 2-6% light intensities of full sun was ranged from 1.1~5.0 were greater in the full sun light was ranged from 0.6~3.2. Light intensity by artificial shade treatment decreased in deciduous trees when compared on the whole, it showed tendency that SLA increases, increased that seeing resemblant tendency in LAR and LWR and changed of light intensity is strong, it increased that showed difference as statistical. But, LWR of Betula platyphylla var. japonica increased gradually and showed tendency that decreases rapidly in the shade treatment of 2-6% light intensities of full sun. This result is thought that biomass production decreased by shading treatment influenced in physiological characteristics such as leaf area and decrease of the leaf amount.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.235-250
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• 2021

The overarching question of this study is how a typical rice cultivation system in Gimje, Korea was keeping up with the triple-win challenge of climate-smart agriculture (CSA). To answer this question, we have employed (1) quantitative data from direct measurement of energy, water, carbon and information flows in and out of a rice cultivation system and (2) appropriate metrics to assess production, efficiency, GHG fluxes, and resilience. The study site was one of the Korean Network of Flux measurement (KoFlux) sites (i.e., GRK) located at Gimje, Korea, managed by National Academy of Agricultural Science, Rural Development Administration. Fluxes of energy, water, carbon dioxide (CO₂) and methane (CH₄) were directly measured using eddy-covariance technique during the growing seasons of 2011, 2012 and 2014. The production indicators include gross primary productivity (GPP), grain yield, light use efficiency (LUE), water use efficiency (WUE), and carbon uptake efficiency (CUE). The GHG mitigation was assessed with indicators such as fluxes of carbon dioxide (F_CO2), methane (F_CH4), and nitrous oxide (F_N2O). Resilience was assessed in terms of self-organization (S), using information-theoretic approach. Overall, the results demonstrated that the rice cultivation system at GRK was climate-smart in 2011 in a relative sense but failed to maintain in the following years. Resilience was high and changed little for three year. However, the apparent competing goals or trade-offs between productivity and GHG mitigation were found within individual years as well as between the years, causing difficulties in achieving the triple-win scenario. The pursuit of CSA requires for stakeholders to prioritize their goals (i.e., governance) and to practice opportune interventions (i.e., management) based on the feedback from real-time assessment of the CSA indicators (i.e., monitoring) - i.e., a purpose-driven visioneering.