• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.370-375
• /
• 2012

국가개발연구원(KDI)에서는 새만금에 40MW 용량의 국산 풍력발전단지 조성을 위한 예비타당성 조사를 실시하였다. 본 사업에 대한 KDI의 비용편익 분석 결과 순 현재가치가 0보다 작고, B/C 비율은 0.73으로 경제적 타당성이 나타나지 않았다. 하지만 모든 비용과 편익을 화폐가치로 환산해 내는 비용편익분석은 여러 가지 외부효과로 인해 사업의 타당성 연구자들에 의해 주관적인 결과물이 나오기도 한다. 이에 따라 본 논문에서는 새만금 풍력발전 시범단지의 경제성 평가 재검토 연구를 실시하였다. 본 논문에서는 기존 경제성 평가 항목에 대하여 여러 가지 쟁점을 제시하고, 그 중에서 대기오염물질 저감 비용과 학습효과(learning effect)로 인한 비용 절감 편익을 추가적으로 산정하였다. 여기서 학습효과의 학습속도(learning rate) 를 세 가지 시나리오로 나누어 분석하였다. 두 가지의 추가 편익을 KDI의 기존 예비타당성 조사 분석에 추가한 순 현재가치는 상당한 양의 값이 나왔고, B/C 비율은 8.8 로 편익이 비용에 비해 크게 증가했다. 이러한 항목들의 포함 여부에 따라 타당성 결과가 현저하게 달라짐을 알 수 있다. 향 후 비용편익 분석이 정책 결정에 적절히 반영되기 위해서는 외부효과를 고려한 환경 비용, 그리고 학습효과와 같은 추가적인 사항들이 면밀히 검토되어야 한다. 시장에 기반하지 않은 이러한 외부효과로 인한 항목들은 대상과 시기에 따라 매우 다른 결과를 보여주기에 이에 대한 세부적인 연구가 필요한 시점이다.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.325-330
• /
• 2012

A single-phase PVPCS(photovoltaic power conditioning system) that contains a single phase dc-ac inverter tends to draw an ac ripple current at twice the out frequency. Such a ripple current may shorten passive elements life span and worsen output current THD. As a result, it may reduce the efficiency of the whole PVPCS system. In this paper, the ripple current propagation is analyzed, and two methods to reduce the ripple current are proposed. Firslyt, this paper presents notch filter with IP voltage controller to reject specific current ripple in single-phase PVPCS. The notch filter can be designed that suppress just only specific frequency component and no phase delay. The proposed notch filter can suppress output command signal in the ripple bandwidth for reducing output current THD. Secondly, for reducing specific current ripple, the other method is feed-forward compensation to incorporate a current control loop in the dc-dc converter. The proposed notch filter and feed-forward compensation method have been verified with computer simulation and simulation results obtained demonstrate the validity of the proposed control scheme.

• The Korean Journal of Ecology
• /
• v.1 no.2
• /
• pp.57-65
• /
• 1977

The biomass and net production of alder and oak trees was estimated by allometric method. The productivity of the two stands of alder and oak was obviously different judging from the rate of photosynthesis productive structure and vertical distribution of light. The amounts of net photosynthesis under the saturated light were 2.31, 1.42mg $CO_2/dm^2\cdot$hr. in the sun and shade leaves of alder tree and 1.58, 0.84mg $CO_2/dm^2\cdot$hr in that of the oak, respectively. Total annual respiration loss calculated from the respiration measured at $25^{\circ}C$ and the mean air temperature from every 10 days were 13.56ton/ha.yr in the alder stand and 19.83 ton/ha.yr in the oak. The productive structure and the vertical distribution of light in the stand were assumedly more effective to produce dry matter in the oak stand than in the alder. The biiomasses measured in 1975 and 1976 were 51.51 and 56.82 ton/ha in the alder stand and 73.35, 86.77 ton/ha in the oak one, respectively. Annual net production and gross production were 8.56 and 22.12 ton/ha.yr in the alder stand but those were 17.90 and 37.74 ton/ha.yr in the oak stand. The ratios of respiration to gross procution (R/Pg) were prespectively 0.61 and 0.53 inthe alder and oak stands. Efficiencies of solar energy utilizaztion of net production during the growing season(May-Oct.) were 0.67 and 1.40% and those of gross production were 1.72 and 2.94% in the alder and oak stands respectively.

• Journal of Environmental Science International
• /
• v.17 no.8
• /
• pp.841-856
• /
• 2008

This research outlines a new method for evaluation of shellfish production in Gamak Bay based on the concept of EMERGY. Better understanding of those environmental factors influencing oyster production and the management of oyster stocks requires the ability to assess the real value of environmental sources such as solar energy, river, tide, wave, wind, and other physical mechanisms. In this research, EMERGY flows from environment sources were 76% for shellfish aquaculture in Gamak Bay. EMERGY yield ratio, Environmental Loading Ratio, and Sustainability Index were 4.26, 0.31 and 13.89, respectively. Using the Emergy evaluation data, the predicted maximum shellfish aquaculture production in Gamak Bay and the FDA (Food and Drug Administration, U.S.) designated area in Gamak Bay were 10,845 ton/y and 7,548 ton/yr, respectively. Since the predicted shellfish production was approximately 1.3 times more than produced shellfish production in 2005, the carrying capacity of Gamak Bay is estimated to be 1.3 times more than the present oyster production.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.4
• /
• pp.659-665
• /
• 2017

Power semiconductor devices required the low on-resistance and high breakdown voltage. Wide band-gap materials opened a new technology of the power devices which promised a thin drift layer at an identical breakdown voltage. The diamond had the wide band-gap of 5.5 eV which induced the low power loss, high breakdown capability, low intrinsic carrier generation, and high operation temperature. We investigated the p-type pseudo-vertical diamond Schottky barrier diodes using a numerical simulation. The impact ionization rate was material to calculating the breakdown voltage. We revised the impact ionization rate of the diamond for adjusting the parallel-plane breakdown field at 10 MV/cm. Effects of the field plate on the breakdown voltage was also analyzed. A conventional diamond Schottky barrier diode without field plate exhibited the high forward current of 0.52 A/mm and low on-resistance of $1.71{\Omega}-mm$ at the forward voltage of 2 V. The simulated breakdown field of the conventional device was 13.3 MV/cm. The breakdown voltage of the conventional device and proposed devices with the $SiO_2$ passivation layer, anode field plate (AFP), and cathode field plate (CFP) was 680, 810, 810, and 1020 V, respectively. The AFP cannot alleviate the concentration of the electric field at the cathode edge. The CFP increased the breakdown voltage with evidences of the electric field and potential. However, we should consider the dielectric breakdown because the ideal breakdown field of the diamond is higher than that of the $SiO_2$, which is widely used as the passivation layer. The real breakdown voltage of the device with CFP decreased from 1020 to 565 V due to the dielectric breakdown.

• Transactions of the KSME C: Technology and Education
• /
• v.1 no.2
• /
• pp.147-152
• /
• 2013

In this paper, we surveyed the opinion of MOTIE(Ministry of Trade, Industry and Energy) R&D PDs about what are the future promising industries and their mainly associated Ppuri-technologies. According to the survey result, the future technology trends are to shift the technologies beyond their own critical performance and dominate human-centered technologies through converging technologies. In particular, the 4 industries, personalized medical technology, intelligent and emotional-based system, solar power technology and flexible technology, are expected to be good perspective industries in the near future. In order to grow these industries, we need to develop the core Ppuri-technologies that are very closely related to the future main industries. More than all, Ppuri-technology acts as a leverage for the future promising industry and is expected to be the strong supporter in manufacturing infra.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.188.1-188.1
• /
• 2014

Aluminum is widely used as a material for electrode on silicon based devices. Especially, aluminum films are used as backside and front-side electrodes in silicon quantum dot (QD) solar cells. In this point, the diffusion of aluminum is very important for the enhancement of power conversion efficiency by improvement of contact property. Aluminum was deposited on a Si (100) wafer and a Si QD layer by ion beam sputter system with a DC ion gun. The Si QD layer was fabricated by $1100^{\circ}C$ annealing of the $SiO_2/SiO_1$ multilayer film grown by ion beam sputtering deposition. Cs ion beam with a low energy and a grazing incidence angle was used in SIMS depth profiling analysis to obtain high depth resolution. Diffusion behavior of aluminum in the Al/Si and Al/Si QD interfaces was investigated by secondary ion mass spectrometry (SIMS) as a function of heat treatment temperature. It was found that aluminum is diffused into Si substrate at $450^{\circ}C$. In this presentation, the effect of heat treatment temperature and Si nitride diffusion barrier on the diffusion of Al will be discussed.

• Korean Journal of Materials Research
• /
• v.26 no.1
• /
• pp.47-53
• /
• 2016

Silicon nitride ($SiN_x:H$) films made by plasma enhanced chemical vapor deposition (PECVD) are generally used as antireflection layers and passivation layers on solar cells. In this study, we investigated the properties of silicon nitride ($SiN_x:H$) films made by PECVD. The passivation properties of $SiN_x:H$ are focused on by making the antireflection properties identical. To make equivalent optical properties of silicon nitride films, the refractive index and thickness of the films are fixed at 2.0 and 90 nm, respectively. This limit makes it easier to evaluate silicon nitride film as a passivation layer in realistic application situations. Next, the effects of the mixture ratio of the process gases with silane ($SiH_4$) and ammonia ($NH_3$) on the passivation qualities of silicon nitride film are evaluated. The absorption coefficient of each film was evaluated by spectrometric ellipsometry, the minority carrier lifetimes were evaluated by quasi-steady-state photo-conductance (QSSPC) measurement. The optical properties were obtained using a UV-visible spectrophotometer. The interface properties were determined by capacitance-voltage (C-V) measurement and the film components were identified by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectroscopy detection (RBS) - elastic recoil detection (ERD). In hydrogen passivation, gas ratios of 1:1 and 1:3 show the best surface passivation property among the samples.

• Korean Journal of Materials Research
• /
• v.28 no.1
• /
• pp.68-74
• /
• 2018

Cobalt-incorporated zeolitic imidazolate framework ZIF-8 was synthesized by a simple one-pot synthesis method at room temperature. Powder X-ray diffraction patterns and energy dispersive X-ray spectrum confirmed the formation of the bimetallic Co/Zn-ZIF structure. UV-Vis diffuse reflectance spectra revealed that the bimetallic ZIF had a lower HOMO-LUMO gap compared with ZIF-8 due to the charge transfer process from organic ligands to cobalt centers. A hydrolytic stability test showed that Co/Zn-ZIF is very robust in aqueous solution - the most important criterion for any material to be applied in photodegradation. The photocatalytic efficiency of the synthesized samples was investigated over the Indigo Carmine (IC) dye degradation under solar simulated irradiation. Cobalt incorporated ZIF-8 exhibited high efficiency over a wide range of pH and initial concentration. The degradation followed through three distinct stages: a slow initial stage, followed by an accelerated stage and completed with a decelerated stage. Moreover, the photocatalytic performance of the synthesized samples was highly improved in alkaline environment rather than in acidic or neutral environments, which may have been because in high pH medium, the increased concentration of hydroxyl ion facilitated the formation of hydroxyl radicals, a reactive species responsible for the breaking of the Indigo Carmine structure. Thus, Co/Zn-ZIF is a promising and green material for solving the environmental pollution caused by textile industries.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1795-1800
• /
• 2014

The temperature change in the biologically activated sludge wastewater treatment process was predicted using the heat transfer model. All incoming and outgoing heats in wastewater treatment processes were considered. Incoming heats included the solar radiation heat, the heat from impeller mechanical energy, and the biochemical heat in the aeration process. Outgoing heats comprised the radiation heat from the waste itself, the heat of vaporization and surface aeration, the wind convection heat and the conduction heat between the surface and aerator. All heats were used as an input to the existing empirical heat transfer model. The heat transfer model of wastewater treatment processes is presented also. To test the validity of the heat transfer model, the operating conditions of the actual wastewater treatment plant were used. The temperatures were compared with the model temperatures. Model predictions were consistent within the $1.0^{\circ}C$.