• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.101-101
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• 2010

Anaerobic digestion(AD) is the most promising method for treating and recycling of different organic wastes, such as organic fraction of municipal solid waste, household wastes, animal manure, agro-industrial wastes, industrial organic wastes and sewage sludge. During AD, i.e. organic materials are decomposed by anaerobic forming bacteria and fina1ly converted to excellent fertilizer and biogas which is a mixture of carbon dioxide and methane. AD has been one of the leading technologies that can make a large contribution to produce renewable energy and to reduce $CO_2$ and other green-house gas(GHG) emission, it is becoming a key method for both waste treatment and recovery of a renewable fuel and other valuable co-products. Currently some 80% of the world's overall energy supply of about 400 EJ per year in derived from fossil fuels. Nevertheless roughly 10~15% of this demand is covered by biomass resources, making biomass by far the most important renewable energy source used to date. The representative biofuels produced from the biomass are bioethanol, biodiesel and biogas, and currently biogas plays a smaller than other biofuels but steadily growing role. Traditionally anaerobic digestion applied for different biowaste e.g. sewage sludge, manure, other organic wastes treatment and stabilization, biogas has become a well established energy resource. However, the biowaste are fairly limited in respect to the production and utilization as renewable source, but the plant biomass, the so called "energy crops" are used for more biogas production in EU countries and the investigation on the biomethane potential of different crops and plant materials have been carried out. In Korea, with steadily increasing oil prices and improved environmental regulations, since 2005 anaerobic digestion was again stimulated, especially on the biogasification of different biowastes and agro-industrial biomass including "energy crops". This study have been carried out to investigate anaerobic biodegradability by the biochemical methane potential(BMP) test of animal manures, different forage crops i.e. "energy crops", plant and industrial organic wastes in the condition of thermophilic temperature, The biodegradability of animal manure were 63.2% and 58.2% with $315m^3CH_4/tonVS$ of cattle slurry and $370m^3CH_4/tonVS$ of pig slurry in ultimate methane yields. Those of winter forage crops were the range 75% to 87% with ultimate methane yield of $378m^3CH_4/tonVS$ to $450m^3CH_4/tonVS$ and those of summer forage crops were the range 81% to 85% with ultimate methane yield of $392m^3CH_4/tonVS$ to $415m^3CH_4/tonVS$. The forge crops as "energy crops" could be used as good renewable energy source to increase methane production and to improve biodegradability in co-digestion with animal manure or only energy crop digestion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.19-26
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• 2010

A PEMFC(proton exchange membrane fuel cell) is a good candidate for residential power generation to be coped with the shortage of fossil fuel and green house gas emission. The attractive benefit of the PEMFC is to produce electric power as well as hot water for home usage. The thermal management of PEMFC for RPG is to utilize the heat of PEMFC so that the PEMFC can be operated at its optimal efficiency. In this study, thermal management system of PEMFC stack is modeled to understand the dynamic response during load change. The thermal management system of PEMFC for RPGFC is composed of two cooling circuits, one for controling the fuel cell temperature and the other for heating up the water for home usage. The different operating strategy is applied for each cooling circuit considering the duty of those two circuits. Even though the capacity of PEMFC system (1kW) is enough to supply hot domestic water for residence, heat-up of reservior takes some hours. Therefore, in this study, time schedule of the simulation reflects the heat-up process. Dynamic responses and operating strategies of the PEMFC system are investigated during load changes.

• Journal of the Korean Wood Science and Technology
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• v.42 no.1
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• pp.1-12
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• 2014

This study carried out life cycle assessment for evaluating environmental impacts of timber Arch-Truss bridge by using domestic Pinus rigida Miller glued-laminated timber throughout life cycle such as extraction, manufacturing, transportation, construction, use, dismantlement, transportation of waste, disposal and recycling. The life cycle GHG (GreenHouse Gas) emissions of the target bridge are 192.56 ton $CO_2$ eq. in 50 years. Especially, the life cycle GHG emissions of concrete used in the target bridge are 82.84 ton $CO_2$ eq. which accounts for 53.02% of the GWP (Global Warming Potential) in extraction and manufacturing stages. The target bridge is constructed of $116.57m^3$ of domestic Pinus rigida Miller glued-laminated timber and used timber has stored 104.72 ton $CO_2$. If an effect of carbon storage in timber is applied to the total GHG emissions of the target bridge, the GHG emissions can be reduced by 54.38%. In the case of substitution effect, if domestic Pinus rigida Miller glued-laminated timber replaces steel manufactures used in other bridge which has the same structure and life span as the target bridge, the GHG emissions in extraction and manufacturing stages can be reduced by 10.26% to 23.91%.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.985-994
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• 2007

Small hydropower is the one of the cleanest one among new and renewable energy with less green house gas emissions. Recently, the necessity of developing small hydropower is emerging since its remaining potential resources in this country are abundant. However, a survey or research on the small hydropower development has been hardly performed since the 1990#s. These circumstances encourages a systematic approach for the small hydropower development. The purpose of this study is to propose a methodology of the location analysis for developing small hydropower. To this end, constraint and location criteria with weights are established and quantification method of each factor is presented. Especially, the analysis procedure is established on the basis of GSIS. Also the study focus on raising the objectivity and precision of analysis by developing system model with automatic search. The proposed methodology is applied to Bochung stream in Keum Riverbasin. The result selects the four and two locations of dam type and run-of-river type respectively. This study will be beneficial to the future activation of small hydropower development as a fundamental work.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.562-571
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• 2014

In these days, many countries carry out many renewable energy policies to increase the renewable energy portion and to reduce the GHG(Green House Gas). In Korea, RPS(Renewable Portfolio Standards) focused on over 500MW power producers is conducting. And they are using the bio-fuel oil to meet their RPS quota. The oil is a mixture of animal and vegetable fat or fatty acid ester of them and should satisfy some specifications to use the power generation such as viscosity, pour point, acid number. Depends on the raw materials, quality characteristics of power bio-fuel oil are changed. By adding the power bio-fuel oil, pour point, density, sulfur content and viscosity are decreased and acid number, iodine number, oxygen content are increased. In this study, we test the quality characteristic of power bio-fuel oil and the property changes by the blending ratio of power bio-fuel oil & conventional fuel oil.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.129-143
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• 2015

Increasing concerns on climate change and energy security accelerated policies to reduce green-house gas emission, especially from the transportation sector. Electric vehicle (EV) has been on the spotlight to deal with such environmental issue and V2G (Vehicle-to-Grid) technology began to draw attentions as an alternative to reduce ownership costs while contributing to an efficient and decentralized power grid. This study conducts a scenario analysis on total cost of ownership of EV under V2G scheme and compare with non-V2G EV and Internal Combustion Engine (ICE) vehicle. As result, V2G service is expected to provide an annual average profit of $210 to EV users willing to reverse flow its residual power in the battery. The profit from V2G service leaves a margin of $4,530 over operational lifetime, compared with $2,420 cost of charge for non-V2G EV. In summary, total cost of ownership of V2G-capable EV was 6.2% less than non-V2G EV and 10.2% higher than ICE vehicle. The results confirm a comparative economic advantage of operating EV under V2G scheme. Increased number of EVs with V2G service has shown to provide positive effects to power industry for valley filling in load distribution, thus, favorably increasing the overall economic feasibility.

• Korean Journal of Agricultural and Forest Meteorology
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• v.10 no.2
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• pp.65-68
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• 2008

Crop production in a country is very crucial not only in a country's crop self-sufficiency, but also in carbon recycle. Crop can capture and store the emitted $CO_2$ by cereal food consumption. However, imported cereal food is not concerned in carbon recycle and this hinders the accurate estimation of carbon recycle. Korea imports major grain products including wheat, corn, soybean, and rice and about 90% of the grain composition consists of carbohydrate, protein and lipid. Carbon portions in carbohydrate, protein and lipid are 45, 53, and 77%, respectively. When the carbon portions are digested and converted into $CO_2$ completely, one ton of rice, wheat, corn, and soybean can release 1.51, 1.63, 1.56, and 1.56 tons of $CO_2$ to the atmopshere, respectively. Based on this premise, the evolved $CO_2$ calculated from imported grains for the last 4 years in Korea was over 21 MT of $CO_2$. This amount is equivalent to 4.8 billion US dollars in the conception of carbon tax. These results suggest that a decrease in a cereal import(i.e, an increase in a country's crop self-sufficiency) can lower $CO_2$ release to the atmosphere.

• Journal of Korean Society of Forest Science
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• v.104 no.2
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• pp.239-247
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• 2015

Since 2006, new national forest inventory in Korea has been restructured to assess current status and and monitor the changes in forest resources based on permanent sample plots. The objective of estimate this study is to assess changes in forest resources such as land use/cover categories and forest stand variables. For this study, permanent plot data were collected between 2006-2008 and 2011-2013 in Chungcheongbuk-do, respectively. In order to produce land use/cover change matrix which plays an important role as an activity data for estimating GreenHouse Gas inventory, permanent plots were classified into six land use/cover categories. Additionally, matrixes for assessing the changes in age class and dominant tree species can provide more detailed information. For forest stand variables(tree density, basal area, growing stock, mean diameter at breath height, and mean height), their growth and change were assessed. The periodic annual growth ratios for tree density and basal area were slightly declined whereas that of growing stock was estimated to be about 3.7%. The uncertainty of changes in forest stand variables is less than 5%, except for tree density (RSE: 58%). The variation of tree density is relatively high compared to the other variables.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.56-61
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• 2009

Paradigm depending only on fossil fuel for building heat source is rapidly changing. Accelerating the change, as it has been known, is obligation for reducing green house gas coming from use of fossil fuel, i.e. reaction to United Nations Framework Convention on Climate Change. In addition, factors such as high oil price, unstable supply, weapon of petroleum and oil peak, by replacing fossil fuel, contributes to advance of environmental friendly renewable energy which can be continuously reusable. Therefore, current new energy policies, beyond enhancing effectiveness of heat using equipments, are to make best efforts for national competitiveness. Our country supports 11 areas for new renewable energy including sun light, solar heat and wind power. Among those areas, ocean thermal energy specifies tidal power generation using tide of sea, wave and temperature differences, wave power generation and thermal power generation. But heat use of heat source from sea water itself has been excluded as non-utilized energy. In the future, sea water heat source which has not been used so far will be required to be specified as new renewable energy. This research is to survey local heating system in Europe using sea water, central solar heating plants, seasonal thermal energy store and to analyze large scale central solar heating plants in German. Seasonal thermal energy store necessarily need to be equipped with large scale thermal energy store. Currently operating central solar heating system is a effective method which significantly enhances sharing rate of solar heat in a way that stores excessive heat generating in summer and then replenish insufficient heat for winter. Construction cost for this system is primarily dependent on large scale seasonal heat store and this high priced heat store merely plays its role once per year. Since our country is faced with 3 directional sea, active research and development for using sea water heat as cooling and heating heat source is required for seashore villages and building units. This research suggests how to utilize new energy in a way that stores cooling heat of sea water into seasonal thermal energy store when temperature of sea water is its lowest temperature in February based on West Sea and then uses it as cooling heat source when cooling is necessary. Since this method utilizes seasonal thermal energy store from existing central solar heating plant for heating and cooling purpose respectively twice per year maximizing energy efficiency by achieving 2 seasonal thermal energy store, active research and development is necessarily required for the future.

• Journal of Energy Engineering
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• v.25 no.2
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• pp.94-100
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• 2016

ESS(Energy Storage System) is an important source that keeps power supply stable and utilizes electricity efficiently. For example, ESS contributes to resolve power supply imbalance, stabilize new renewable energy output and regulate frequency. ESS is predicted to be expanded to 55.9GWh of installed capacity by 2023, which is 30 times more than that of 2014. To raise competitiveness of domestic ESS industry in this increasing world market, we have disseminated load-shift ESS for continuous power supply imbalance with FR ESS, and also necessity to secure domestic track record is required. However in case of FR ESS, utility of installing thermal power plant is generally generated within 5% range of rated capacity, so that scalability of domestic market is low without dramatic increase of thermal power plant. Necessity of load-shift ESS dissemination is also decreasing effected by surplus backup power securement policy, raising demand for new dissemination model. New dissemination model is promising for $CO_2$ reduction effect in spite of intermittent output. By stabilizing new renewable energy output in connection with new renewable energy, and regulating system input timing of new renewable energy generation rate, it is prospected model for 'post-2020' regime and energy industry. This research presents a policy alternatives of REC multiplier calculation method to induce investment after outlining PV-connected ESS charge/discharge mode to reduce GHG emission, This alternative is projected to utilize GHG emission reduction methodology for 'Post-2020' regime, big issue of new energy policy.