• Korean Chemical Engineering Research
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• 제58권3호
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• pp.396-407
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• 2020

As fossil fuels are depleted worldwide, alternative resources is required to replace fossil fuels, and biofuels are in the spotlight as alternative resources. Biofuels are produced from biomass, which is a renewable resource to produce biofuels or bio-chemicals. Especially, in order to substitute fossil fuels, the research focusing the biofuel (biodiesel) production based on CO₂ and biomass achieves more attention recently. To produce biomass-based biodiesel, the development of a supply chain network is required considering the amounts of feedstocks (ex, CO₂ and water) required producing biodiesel, potential locations and capacities of bio-refineries, and transportations of biodiesel produced at biorefineries to demand cities. Although many studies of the biomass-based biodiesel supply chain network are performed, there are few types of research handled the uncertainty in CO₂ supply which influences the optimal strategies of microalgae-based biodiesel production. Because CO₂, which is used in the production of microalgae-based biodiesel as one of important resources, is captured from the off-gases emitted in power plants, the uncertainty in CO₂ supply from power plants has big impacts on the optimal configuration of the biodiesel supply chain network. Therefore, in this study, to handle those issues, we develop the two-stage stochastic model to determine the optimal strategies of the biodiesel supply chain network considering the uncertainty in CO₂ supply. The goal of the proposed model is to minimize the expected total cost of the biodiesel supply chain network considering the uncertain CO₂ supply as well as satisfy diesel demands at each city. This model conducted a case study satisfying 10% diesel demand in the Republic of Korea. The overall cost of the stochastic model (US$ 12.9/gallon·y) is slightly higher (23%) than that of the deterministic model (US$ 10.5/gallon·y). Fluctuations in CO₂ supply (stochastic model) had a significant impact on the optimal strategies of the biodiesel supply network.

• Journal of Plant Biotechnology
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• 제34권2호
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• pp.111-118
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• 2007

Global warming crisis due primarily to continued green house gas emission requires impending change to renewable alternative energy than continuously depending on exhausting fossil fuels. Bioenergy including biodiesel and bioethanol are considered good alternatives because of their renewable and sustainable nature. Bioethanol is currently being produced by using sucrose from sugar beet, grain starches or lignocellulosic biomass as sources of ethanol fermentation. However, grain production requires significant amount of fossil fuel inputs during agricultural practices, which means less competitive in reducing the level of green house gas emission. By contrast, cellulosic bioethanol can use naturally-growing, not-for-food biomass as a source of ethanol fermentation. In this respect, cellulosic ethanol than grain starch ethanol is considered a more appropriate as a alternative renewable energy. However, commercialization of cellulosic ethanol depends heavily on technology development. Processes such as securing enough biomass optimized for economic processing, pretreatment technology for better access of polymer-hydrolyzing enzymes, saccharification of recalcitrant lignocellulosic materials, and simultaneous fermentation of different sugars including 6-carbon glucose as well as 5-carbon xylose or arabinose waits for greater improvement in technologies. Although it seems to be a long way to go until commercialization, it should broadly benefit farmers with novel source of income, environment with greener and reduced level of global warming, and national economy with increased energy security. Mission-oriented strategies for cellulosic ethanol development participated by government funding agency and different disciplines of sciences and technologies should certainly open up a new era of renewable energy.

• World Technopolis Review
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• 제8권1호
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• pp.59-70
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• 2019

Where is a better place to live? In the coming era, this should be more than simply a livable place. It should be an adaptable place that has a flexible system adaptable to any new situation in terms of diversity. Customization and real-time operation are needed in order to realize this technologically. We expect a smart city to have a flexible system that applies technologies of self-monitoring and self-response, thereby being a promising city model towards being a better place to live. Energy demand and supply is a crucial issue concerning our expectations for the flexible system of a smart city because it is indispensable to comfortable living, especially city living. Although it may seem that energy diversification, such as the energy mix of a country, is a matter of overriding concern, the central point is the scale of place to build grids for realizing sustainable urban energy systems. A traditional hard energy path supported by huge centralized energy systems based on fossil and nuclear fuels on a national scale has already faced difficult problems, particularly in terms of energy flexibility/resilience. On the other hand, an alternative soft energy path consisting of small diversified energy systems based on renewable energy sources on a local scale has limitations regarding stability, variability, and supply potential despite the relatively light economic/technological burden that must be assumed to realize it. As another alternative, we can adopt a holonic path incorporating an alternative soft energy path with a traditional hard energy path complimentarily based on load management. This has a high affinity with the flexible system of a smart city. At a system level, the purpose of all of the paths mentioned above is not energy itself but the service it provides. If the expected energy service is fixed, the conclusive factor in choosing a more appropriate system is accessibility to the energy service. Accessibility refers to reliability and affordability; the former encompasses the level of energy self-sufficiency, and the latter encompasses the extent of energy saving. From this point of view, it seems that the small diversified energy systems of a soft energy path have a clear advantage over the huge centralized energy systems of a hard energy path. However, some insuperable limitations still remain, so it is reasonable to consider both energy systems continuing to coexist in a multiplexing energy system employing a holonic path to create and maintain reliable and affordable access to energy services that cover households'/enterprises' basic energy needs. If this is embodied in a smart city concept, this is nothing else but smart energy inclusion. In Japan, following the Fukushima nuclear accident in 2011, a trend towards small diversified energy systems of a soft energy path intensified in order to realize a nuclear-free society. As a result, the Government of Japan proclaimed in its Fifth Strategic Energy Plan that renewable energy must be the main source of power in Japan by 2050. Accordingly, Sony vowed that all the energy it uses would come from renewable sources by 2040. In this situation, it is expected that smart energy inclusion will be achieved by the Japanese version of a smart grid based on the concept of a minimum cost scheme and demand response.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제11권4호
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• pp.333-349
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• 2013

As the capacity of spent nuclear fuel storage pool at reactor sites becomes saturated in ten years, long term dry storage strategy has been recently discussed as an alternative option in Korea. In this study, we reviewed safety-criteria-related research results on spent nuclear fuel performance and integrity under long-term dry storage and proposed the direction and the scope of future domestic research and development. Creep and hydride effect in relation to the embrittlement are known to be the major degradation mechanisms of the spent fuels during the long term dry storage. However, recent research results showed that hydride reorientation and hydride embrittlement are one of the most critical factors to the spent fuel integrity. Accordingly safety criteria of US and Japan for the storage system are basically founded on those mechanisms. However, in Korea, not only in-pile but out-of-pile experimental data have not been generated to understand fuel cladding degradation and to determine the criteria to ensure the safety. In addition, the transient behavior of the spent fuel during transportation also needs to be thoroughly examined. Therefore, various experimental research and development will be required to establish our own safety criteria for future long-term dry storage of domestic spent fuels.

• Journal of Korean Society of Environmental Engineers
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• 제36권4호
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• pp.231-236
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• 2014

Sawdust, produced as an wood by-product, is usable biomass as liquid fuels if decomposed to monomer unit, because the chemical structure are similar to high octane materials found in gasoline. In this study, parameters of thermochemical degradation by acetone-solvolysis reaction of sawdust such as the effect of reaction temperature, reaction time and type of solvent on conversion yield and degradation products were investigated. The liquid products by acetone-solvolysis from sawdust produced various kind of ketone, phenol and furan compounds. The optimum sawdust conversion was observed to be 88.7% at $350^{\circ}C$, 40min. Combustion heating value of liquid products from thermochemical conversion processes was as high as 7,824 cal/g. The energy yield and mass yield in acetone-solvolysis of sawdust was 60.8% and 36.4 g-oil/100g-sawdust after 40 min of reaction at $350^{\circ}C$, respectively. The major components of the acetone-solvolysis products, that could be used as liquid fuel, were 4-methyl-3-pentene-2-one, 1,3,5-trimethylbezene, 2,6-dimethyl-2,5-heptadiene-4-one, 3-methyl-2-cyclopenten-1-one as ketone compounds.

• Journal of Biosystems Engineering
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• 제3권2호
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• pp.100-113
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• 1978

Drying grain with conventional artificial drying methods requires great quantities of petroleum fuels. Depletion of fossil fuel increases the need of the utilization of solar energy as an alternative to petroluem fuels for drying grain , an energy intensive agricultural operation. Many techniques for the utilization of solar energy in grain drying have been developed, however, there are many problems in adopting solar energy as an energy sources for drying grain. Futhermore, very little research has been done on solar grain drying in Korea. This study was conducted to evaluate the availability of solar energy for drying of rough rice in Chuncheon, Suweon, and Jinju areas based on 50year meteorological data, and to analyze experimentally the performance of a solar air collector for dying grain, and to find the effects of solar heated air compared to unheated air on the rate of drying and energy consumption required for drying of rough rice. The results of this study was may be summarized as follows ; 1. Monthly average daily total radiation on a horizontal surface in October was 260.6 ly/day for Chuncheon, 240.3 ly/day for Suweon , and 253.4 ly/day for Jinju area, respectively. 2. the ratio of monthly average daily diffuse radiation to daily total radiation on a horizontal surface was approximately 0.41 for Chuncheon, 0.45 for Suweon, and 0.44 for Jinju area, respectively. 3. Although the statistical distribution curves of daily total radiation for the three locations were not identical , the differences among them were not large and may be neglected for many practical purposes. 4. I was estimated that the optimum tilting angle of the collector in October was approximately 46 degrees for Chuncheon and Suweon and 45 degrees for Jinju. 5. The ratio of the total radiation on a optimum tilting plane to that on a horizontal plane was estimated to be 1.36 for Chuncheon, 1.31 for Suweon, and 1.27 for Jinju , respectively. 6. The collection efficiency of the solar air collector ranged from 47. 8 to 51. 5 percent at the air flow rates of 251. 1-372.96 $m^3$/hr. High efficiency remained nearly , constant during the best sunshine hours, 10 a.m. to 2 p.m. and decreased during other hours. More energy was collected as the air flow rate incresed. 7. The average temperature rise in the drying air from the solar collector for the test period varied from $6.5^\circC$ to $21.8^\circC$ above the ambient air temperature. 8. Solar-dried rough rice averaged 13.7 percent moisture (w.b.) after 130 hours of drying with the air flow rate of 1. 64 ccm/$m^3$, and rough rice dried with natural air averaged 15.1 percent moisture (w.b.) after 325 hours of drying with the same air flow rate. 9. Energy saving of 2.4 kwh per $m^3$ percentage point of moisture removed was obtained from solar heated air drYing. The solar bin used 53.3 percent less energy per percentage point of moisture removed than the natural air bin.

• Journal of Biosystems Engineering
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• 제3권2호
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• pp.114-125
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• 1978

The use of petroleum fuels in grain drying causes problems of high cost and management. To solve these problems, it is required to study on soLar energy as an alternative to petroleum fuels for grain drying. The purposes of this study were to find out the optimum received area and air flow rate of a flat-plate solar air collector for grain drying and to assess its effects on grain drying with a small grain bin. The results of this study are summarized as follows ; 1. The calculated optimum tilt angles of the collector in the summer and autumn drying seasons were 20 and 50 degress, respectively, in suwon area. 2. The outlet temperature of the collector was $36^\circ C$ on the daily average with the maximum of $36^\circ C$ at 12:00 o clock. Solar radiation on the collector surface was 1.04 ly( 1 langley = 1 cal/$cm^2$) per minute on the daily average and 1.30 ly per minute on the maximum at 11:00am. The thermal efficiency of the collector was 62.4 percent on the daily average, and the air flow-rate per unit receiving are was 1.03 $m^3$/min/$m^2$.4. The calculated optimum receiving area and the air flow-rate per unit cubic volume for paddy in autumn drying season was 2 $m^2$ and 2$m^3$/min , respectively. 5. not significantly difference in the collector efficiency was appeared between the rotating and fixed type of solar collector. 6. For drying of wheat with 0.6 meter of the depth in the bin, approximately 9 hours were required to reduce the moisture content from 21.6% to 13% with air follow rate of 5 $m^3$/min an initial moisture per cubic meter of wheat and with air temperature of $52^\circ C$. 7. In the drying test of rough rice with a turning operation in a grain bin approximately 21 hours were required to reduced the moisture from 21% to 14.5% with airflow rate of 2 $m^3$/min per cubic meter of rice and the air temperature of $43.5^\circ C$. 8. Over-drying at the bottom and less -drying at the top of the grain mass was resulted from the high -temperature of drying air which was obtained from the flat-plate solar collector in this test. An appropriate operation should be prepared for the uniform moisture of the grain in the bin.

• Journal of Korea Port Economic Association
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• 제25권4호
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• pp.1-20
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• 2009

Green logistics is regarded as an inevitable global trend in the 21st century. It can be accomplished through more broad and active reverse logistics globally, resulting in use of less fossil fuels, finally reducing carbon dioxide and other pollutants. Many countries such as U.S., Japan, EU nations have already set up policies related to carbon reduction, so-called 'green policies.' This paper aims to identify evaluation criteria for logistics policies and relative importance among those criteria, especially in the field of ports and in-land hub terminals. We examined projects related to carbon reduction from domestic and foreign ports and logistics centers and found evaluation factors and assessment indicators. With pre-evaluative items and pre-assessment indicators, we have done a survey and selected evaluation factors and assessment indicators for ports and inland hub terminals in Korea. By analyzing the mutual importance of each pre-evaluative items and pre-assessment indicators related to carbon reduction policies, this research provides guidelines on selecting the key items for the propulsion of carbon reduction projects. This study shows the importance of preliminary evaluation items and indexes with AHP in evaluating carbon reduction policies and the result shows the restrictions and change in transportation and use of alternative fuels. Lastly, it provides a guideline to policy-makers and firm managers in the field of green logistics.

• Journal of the Korean Institute of Gas
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• 제20권6호
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• pp.9-15
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• 2016

Liquefied petroleum gas (LPG) and compressed natural gas (CNG) are often used as fuel for vehicles because they are clean alternative gas fuels. CNG, as a low-carbon fuel, can contribute to the reduction of greenhouse gas emissions. LPG is often used as fuel for taxis because the performance is almost the same as that of gasoline but the price is lower. In the present study, the exhaust gas and the particle number (PN) of particulate matter, which is a recent environmental issue, were compared between LPG and CNG for the same vehicle. A chassis dynamometer was used to conduct the test according to the Federal Test Procedure (FTP)-75 and Worldwide harmonized Light-duty vehicle Test Procedure (WLTC) modes. The PN values of discharged particles having sizes of 5 nm or larger and 23 nm or larger were measured using two condensation particle counters (CPC). The ratio of carbon dioxide was high in the exhaust gas from the LPG vehicle; the ratio of methane was high in the exhaust gas from the CNG vehicle. The PN values of the emitted particles from the two fuels were similar. The PN values of particles having sizes of 23 nm or smaller were high in the high-speed WLTC mode.

• Korean Chemical Engineering Research
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• 제61권2호
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• pp.296-301
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• 2023

Solid oxide fuel cell has received more attention recently due to the fuel flexibility via internal reforming. Commonly used Ni/YSZ anode, however, can be easily deactivated by carbon coking in hydrocarbon fuels. The carbon deposition problem can minimize by developing alternative perovskite anode. This study is focused on improving conductivity and catalytic activity of the perovskite anode by introducing rGO (reduced graphene oxide). Sr_0.92Y_0.08TiO₃(SYT) anode with perovskite structure was synthesized with 1wt% of rGO. The presence of rGO during anode fabricating process and cell operation is confirmed through XPS and Raman analysis. The maximum power density of rGO/SYT anode improved to 3 times in H₂ and 6 times in CH₄ comparing to that of SYT anode due to the high electrical conductivity and good catalytic activity for CH₄.