• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.223-229
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• 2020

Biodiesel produced using microorganisms, which are recognized as the third-generation biomass, is among the various known renewable energy sources that can replace fossil fuels used in conventional transportation. Scenedesmus obliquus has been identified as an excellent species for biodiesel production, as it grows faster and can accumulate up to 40-50 percent of the dry cell weight. Enhancing production using S. obliquus requires measuring the cell mass for controlling the cultivation process. In the current study, S. obliquus was cultured for 75 days, and growth changes of the microalgae were measured by absorbance, microscopic imaging, and Raman spectroscopy. Between days 60 to 75 of culture, the change in absorbance was observed to be less than 3%, whereas the number of microalgae observed microscopically was more than three times higher. Moreover, the Raman spectroscopy results showed three strong peak values of β-carotene at 997 cm^-1, 1148 cm^-1, and 1515 cm^-1, with peak values of β-carotene showing greater than 3-fold increase during the culture period. Therefore, we predict that application of Raman spectroscopy will help in identifying the growth elements and growth degree in microalgae culture during increased biomass production.

• Korean Journal of Microbiology
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• v.48 no.2
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• pp.125-133
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• 2012

Anaerobic digestion is an alternative method to digest food wastes and to produce methane that can be used as a renewable energy source. We investigated bacterial and archaeal community structures in a three-stage methane production process using food wastes with concomitant wastewater treatment. The three-stage methane process is composed of semianaerobic hydrolysis/acidogenic, anaerobic acidogenic, and strictly anaerobic methane production steps in which food wastes are converted methane and carbon dioxide. The microbial diversity was determined by the nucleotide sequences of 16S rRNA gene library and quantitative real-time PCR. The major eubacterial population of the three-stage methane process was belonging to VFA-oxidizing bacteria. The archaeal community consisted mainly of two species of hydrogenotrophic methanogen (Methanoculleus). Family Picrophilaceae (Order Thermoplasmatales) was also observed as a minor population. The predominance of hydrogenotrophic methanogen suggests that the main degradation pathway of this process is different from the classical methane production systems that have the pathway based on acetogenesis. The domination of hydrogenotrophic methanogen (Methanoculleus) may be caused by mesophilic digestion, neutral pH, high concentration of ammonia, short HRT, and interaction with VFA-oxidizing bacteria (Tepidanaerobacter etc.).

• Journal of Digital Contents Society
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• v.15 no.4
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• pp.513-520
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• 2014

The Smart Grid is next-generation power system materialized Convergence and Integration of power technologies and Information Technologies. And this system is the next generation power system optimizing energy efficiency via real-time information exchanges grafting the information technologies upon present power networks which are web-net. The introduction of smart grid can be embodied for latitude, distributed and cooperated network by inter-active exchange of energy information between electrical power provider and consumer previous uni-directional electrical power supplement. Therefore in this paper, we proposed Convergence technologies - Smart power grid, Smart Place, Smart Renewable and Smart Electricity Service - to make smart-grid succeed via analyzing the datum. And we scoped on Convergence and Integration technologies, which could be used for smart-power-grid that is most important factor to replace previous power industries. And we brought out the expecting industrialize timing and interesting aspects and analyzed the result with survey of professional worker from institute, research center, power plant and business of power industries. And proposed the essential policies for the government and power-control-business companies based on the datum and survey output.

• Journal of Bio-Environment Control
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• v.24 no.4
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• pp.317-325
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• 2015

This paper attempts to present a review about simulation of different greenhouse parameters and energy supplying techniques by using building energy simulation, to find out the optimal solution for keeping greenhouse microclimate favorable for the crop production. The objectives of conducting this study were, to describe the various energy systems and techniques used for the greenhouse energy management and efficiency analysis of these technologies by using building energy simulation. We describe different models to understand the behavior of the energy saving technologies with respect to the resources available and different outside climatic conditions. We identified main features of the building energy simulation software, that enable users, to simulate hybrid agricultural building projects by using user defined parameters. At the end of the paper we draw some important concluding remarks on the basis of reviewing all the investigators contributions for the developments of simulation model of agricultural greenhouse energy management, using a building energy simulation software specifically TRNSYS. In conclusion, this paper provides information that TRNSYS have great potential for agricultural buildings energy simulation along with the renewable energy resources and energy saving techniques. This review paper provides aid to greenhouse researcher and energy planner for the future studies of greenhouses energy planning.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.630-634
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• 2018

The recovery of paraffin components contained in the fraction as a part of improving the quality for the fraction of waste plastics pyrolysis oil (WPPO) was investigated by batch cocurrent 4 stages equilibrium extraction. The fraction at a distilling temperature of $120-350^{\circ}C$ recovered from WPPO by the simple distillation and a little water-added dimethylformamide (DMF) solution were used as a raw material and solvent, respectively. As the number of equilibrium extraction (n) and the carbon number of paraffin component increased, the concentration of paraffin component contained in the raffinate increased. The concentrations of $C_{12}$, $C_{14}$, $C16$ and $C_{18}$ paraffin components present in the raffinate recovered at n = 4 were about 1.2, 1.5, 1.6 and 1.8 times higher than those of using the raw materials, respectively. Recovery rates (residue rates present in raffinate) of paraffin components rapidly decreased with increasing n, and increased sharply with increasing the carbon number. Furthermore, it was possible to predict the recovery rates at n = 1 - 4 for all paraffin components ($C_7-C_{24}$) contained in the raw material. The raffinate recovered through this study is expected to be used as a renewable energy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.1
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• pp.21-26
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• 2011

Ni-YSZ (Yttria Stabilized Zirconia) composite powders were fabricated by glycine nitrate process. The prepared powders were sintered at $1300{\sim}1400^{\circ}C$ for 4 h in air and reduced at $1000^{\circ}C$ for 2 h in a nitrogen and hydrogen atmosphere. The microstructure, electrical conductivity, thermal expansion and mechanical properties of the Ni-YSZ cermets have been investigated with respect to the volume contents of Ni. A porous microstructure consisting of homogeneously distributed Ni and YSZ phases together with well-connected grains was observed. It was found that the open porosity, electrical conductivity, thermal expansion and bending strength of the cermets are sensitive to the volume content of Ni. The Ni-YSZ cermet containing 40 vol% Ni was ascertained to be the optimum composition. This composition offers sufficient open porosity of more than 30 %, superior electrical conductivities of 917.4 S/cm at $1000^{\circ}C$ and a moderate average thermal expansion coefficient of $12.6{\times}10^{-6}^{\circ}C^{-1}$ between room temperature and $1000^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.493-493
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• 2014

The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7176-7181
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• 2015

This thesis is about the system where the solar module is attached to the high functional guardrail posts with anti-weed, anti-plant, and road-kill applied to produce internal power, enabling the integrated control and real-time monitoring of appearance of wildlife and road conditions using the USN. The whole system consists of a photovoltaic module(PV), a detection sensor(pyroelectric), a controller(operation select and motion sensor), the USN system, the DB(sound and flash), an output unit of sound and flash, and the control system of road-kill prevention and safety induction for vehicles. Thus this study aims to address the remote control and monitoring system of multipurpose guardrails to improve road environment, prevent road-kills, protect wild animals, and guide cars safely by using the USN which is combined with new renewable energy and IT convergence technology. As a result of the study on the remote control and monitoring system using the USN, it was ascertained that the response time of the unmanned sensing system was within 5.1 ms with the current consumption of 0.328 mA, and the data transmission speed of the remote control system was 250 kbps with the current consumption of 0.283 mA.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.345-357
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• 2011

Recently, as part of diversifying energy sources and earth environmental issues, technology development of new renewable energy using wave energy is actively promoted and commercialized around Europe and Japan etc. In particular, OWC(Oscillating Water Column) wave power generation system using air flow induced by vertical movement of the water surface by waves in an air-chamber within caisson is known as the most efficient wave energy absorption device and therefore, is one of the wave power generation apparatus the closest to commercialization. This study examines air flow velocity, which operates turbine(Wells turbine) directly in oscillating water column type wave power generation structure from two-and three-dimensional numerical experiments and discusses optimal shape of oscillating water column type wave power generation structure by estimating the maximum flow rate of air according to change in shape. The three-dimensional numerical wave flume was applied in interpretation for this study which is the model for the immiscible two-phase flow based on the Navier-Stokes Equation. From this, it turned out that size of optimal shape appears differently according to the incident wave period and air flow is maximized at the period where minimum reflection ratio occurs.

• Journal of Energy Engineering
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• v.25 no.3
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• pp.104-113
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• 2016

This study analyzes correlation between methane gas production and injection of food waste water to motivate to expand renewable energy as a way of GHG (Green House Gas) mitigation to achieve the national GHG target proposed for the climate agreement in Paris last year. Pretreatment of food waste water was processed with pH 6 at $35^{\circ}C$ and used the fixed-bed upflow type reactor with the porous media. As a result of operation of pilot-scaled bioreactor with food waste water, the methane gas production was 6 times higher than the methane gas production of control group with rain water. The average production of methane was $56{\ell}/day/m^3$ which is possible to produce $20m^3$ of methane in $1m^3$ of landfill. As a way of energy source, when it is applied to the landfill over $250,000m^3$, it is also able to achieve financial feasibility along with GHG reduction effect. GHG reductions of $250,000m^3$ scale landfill were assessed by registered CDM project and the annual amount of reductions was 40,000~50,000 $tCO_2e$.