• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2883-2897
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• 2022

According to the Renewable Energy 3020 Implementation Plan announced in 2017 by the South Korean government, the electricity share of renewable energy will be expanded to 20% of the total electricity generation by 2030. Given the intermittency of electricity generation from renewable energy, realization of such a plan presents challenges to managing South Korea's isolated national electric grid and implies potentially large excess electricity generation in certain situations. The purpose of this study is: 1) to develop a model to accurately simulate the effects of excess electricity generation from renewables which would arise during the transition, and 2) to propose strategies to manage excess electricity generation through effective utilization of domestic electricity generating capabilities. Our results show that in periods of greater PV and wind power, namely the spring and fall seasons, the frequency of excess electricity generation increases, while electricity demand decreases. This being the case, flexible operation of coal and nuclear power plants along with LNG and pumped-storage hydroelectricity can be used to counterbalance the excess electricity generation from renewables. In addition, nuclear energy plays an important role in reducing CO₂ emissions and electricity costs unlike the fossil fuel-based generation sources outlined in the 8th Basic Plan.

• 자원ㆍ환경경제연구
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• 제14권3호
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• pp.729-751
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• 2005

RPS(Renewable Portfolio Standards)제도는 시장기능을 통하여 전력생산의 일정 양 또는 비율을 신재생에너지로 충당하도록 의무화함으로써 신재생에너지의 보급을 활성화하는 제도이다. 본 논문은 RPS제도의 국내 도입이 전력시장, 개별 산업부문 및 경제 전체에 어떤 영향을 미칠 것인가를 검토하였다. 의무비율을 채우지 못하거나 과다충족한 경우 각 해당부분을 대상사업자로부터 구매하거나 또는 대상사업자에게 판매할 수 있는 TREC(Tradable Renewable Energy Credits)시장과 RPS제도 실시에 따른 추가적인 공급비용이 유발하는 소비자의 추가비용을 판단할 수 있는 소매시장을 분석하여 최종소매가격과 공급량의 변화를 살펴보았다. 끝으로 RPS제도 도입에 따른 전력가격의 상승과 공급의 변화가 국민경제에 미치는 효과를 분석하였다. 주요 결과를 보면, 2011년 기준으로 전력가격의 용도별 평균치는 약 5% 정도 상승, 부문별 물가는 평균 0.268% 상승, 그리고 부문별 GDP는 평균 1.940% 감소하여 물가상승효과는 작은 반면 GDP 감소효과는 큰 것으로 나타났다.

• 청정기술
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• 제26권1호
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• pp.55-64
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• 2020

재생에너지 3020 이행계획에 따라 재생에너지 발전 비중 증가에 대비해 잉여전력 저장 및 전력 공급 안정화 기술 필요성이 대두되고 있다. 이를 위해 수요 공급의 불균형으로 활용할 수 없는 전력을 수소 또는 메탄으로 전환하여 저장하는 Power-to-Gas 기술 개발이 활발히 진행되고 있다. 본 연구에서는 국내 실정을 반영한 Power-to-Gas 경제성분석을 수행하였다. 균등화 수소원가를 산정하기 위하여 Total revenue requirement 방법론을 활용하여 경제성 분석 방법론을 재정립하고, 국제에너지기구의 경제성 분석 결과를 통해 검증하였다. 연구결과 국내 기준 100 MW급 Power-to-Gas 시스템 균등화 수소원가는 kg당 8,344원으로 나타났다. 전기 비용, 수전해 장비 비용, 작동 연한에 따른 민감도 분석이 수행되었고, 재생에너지 이용 수소 생산비용과 천연가스 개질 수소 생산비용을 비교하여 경제성을 확보할 수 있는 조건을 제시하였다.

• 청정기술
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• 제28권2호
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• pp.182-192
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• 2022

This study provides an overview of the production costs of methane and hydrogen via water electrolysis-based hydrogen production followed by a methanation based methane production technology utilizing CO₂ from external sources. The study shows a comparative way for economic optimization of green methane generation using excess free electricity from renewable sources. The study initially developed the overall process on the Aspen Plus simulation tool. Aspen Plus estimated the capital expenditure for most of the equipment except for the methanation reactor and electrolyzer. The capital expenditure, the operating expenditure and the feed cost were used in a discounted cash flow based economic model for the methane production cost estimation. The study compared different reactor configurations as well. The same model was also used for a hydrogen production cost estimation. The optimized economic model estimated a methane production cost of $11.22/mcf when the plant is operating for 4000 hr/year and electricity is available for zero cost. Furthermore, a hydrogen production cost of $2.45/GJ was obtained. A sensitivity analysis was performed for the methane production cost as the electrolyzer cost varies across different electrolyzer types. A sensitivity study was also performed for the changing electricity cost, the number of operation hours per year and the plant capacity. The estimated levelized cost of methane (LCOM) in this study was less than or comparable with the existing studies available in the literature.

• 청정기술
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• 제29권1호
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• pp.53-58
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• 2023

This study shows the summary of the economic performance of excess electricity conversion to hydrogen as well as methane and returned conversion to electricity using a fuel cell. The methane production process has been examined in a previous study. Here, this study focuses on the conversion of methane to electricity. As a part of this study, capital expenditure (CAPEX) is estimated under various sized plants (0.3, 3, 9, and 30 MW). The study shows a method for economic optimization of electricity generation using a fuel cell. The CAPEX and operating expenditure (OPEX) as well as the feed cost are used to calculate the discounted cash flow. Then the levelized cost of returned electricity (LCORE) is estimated from the discounted cash flow. This study found the LCORE value was ¢10.2/kWh electricity when a 9 MW electricity generating fuel cell was used. A methane production plant size of 1,500 Nm³/hr, a methane production cost of $11.47/mcf, a storage cost of $1/mcf, and a fuel cell efficiency of 54% were used as a baseline. A sensitivity analysis was performed by varying the storage cost, fuel cell efficiency, and excess electricity cost by ±20%, and fuel cell efficiency was found as the most dominating parameter in terms of the LCORE sensitivity. Therefore, for the best cost-performance, fuel cell manufacturing and efficiency need to be carefully evaluated. This study provides a general guideline for cost performance comparison with LCORE.

• 한국지능시스템학회논문지
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• 제25권3호
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• pp.299-305
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• 2015

Global environmental concerns and the ever increasing need of energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Distributed electricity generation is a suitable option for sustainable development thanks to the load management benefits and the opportunity to provide electricity to remote areas. Solar energy being easy to harness, non-polluting and never ending is one of the best renewable energy sources for electricity generation in present and future time. Due to the random and intermittent nature of solar source, PV plants require the adoption of an energy storage and management system to compensate fluctuations and to meet the energy demand during night hours. This paper presents an efficient, economic and technical model for the design of a MPPT based grid connected PV with battery storage and management system. This system satisfies the energy demand through the PV based battery energy storage system. The aim is to present PV-BES system design and management strategy to maximize the system performance and economic profitability. PV-BES (photovoltaic based battery energy storage) system is operated in different modes to verify the system feasibility. In case of excess energy (mode 1), Li-ion batteries are charged using CC-CV mechanism effectively controlled by fuzzy logic based PID control system whereas during the time of insufficient power from PV system (mode 2), batteries are used as backup to compensate the power shortage at load and likewise other modes for different scenarios. This operational mode change in PV-BES system is implemented by State flow chart technique based on SOC, DC bus voltages and solar Irradiance. Performance of the proposed PV-BES system is verified by some simulations study. Simulation results showed that proposed system can overcome the disturbance of external environmental changes, and controls the energy flow in efficient and economical way.

• 설비공학논문집
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• 제26권12호
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• pp.559-564
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• 2014

The development of photovoltaic-thermal (PVT) technology has been introduced in recent years specifically to increase PV efficiency. One of the characteristics of PV systems is that the electricity generation increases as the solar radiation increases whereas the efficiency decreases because of high surface temperatures. Using a photovoltaic-thermal system, the surface temperature can be decreased by capturing the excess heat and the efficiency can be increased due to these characteristics. In this paper, three cases are introduced : 1) PV_r as the reference case, 2) PVT_a, which uses air as a heat source, and 3) PVT_w, which uses water as a heat source. Experiments were performed, analyzed, and compared to examine the effect of the PVT type on the efficiency of the system. The results showed that ETC($%/^{\circ}C$) efficiency of the PVT cases was increased versus the reference case due to decreasing surface temperature. Total efficiencies, which are electrical efficiency and thermal efficiency, for each PVT are tested and found to be 12.22% for PV_r, 29.50% for PVT_a, and 68.74% for PVT_w.