• 한국수소및신에너지학회논문집
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• 제30권4호
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• pp.303-311
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• 2019

Reversible solid oxide fuel cell (RSOFC) has become a prospective device for energy storage and hydrogen production. Many studies have been conducted around the world focusing on system efficiency improvement and realization. The system should have not only high efficiency but also a certain level of simplicity for stable operation. External waste steam utilization was proved to remarkably increase the efficiency at solid oxide electrolysis system. In this study, RSOFC system coupled with waste steam was proposed and optimized in term of simplicity and efficiency. Ejector for fuel recirculation is selected due to its simple design and high stability. Three system configurations using ejector for fuel recirculation were investigated for performance of design condition. In parametric study, the system efficiencies at different current density were analyzed. The system configurations were simulated using validated lumped model in EBSILON(R) program. The system components, balance of plants, were designed to work in both electrolysis and fuel cell modes, and their off-design characteristics were taken into account. The base case calculation shows that, the system with suction pump results in slightly lower efficiency but stack can be operated more stable with same inlet pressure of fuel and air electrode.

• 대한토목학회논문집
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• 제39권4호
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• pp.477-483
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• 2019

최근 원자력발전소 및 LNG 저장탱크 등 특수구조물의 공사 기간과 비용 절감을 목적으로 PSC 구조물 대신 프리캐스트 형식의 SCP 모듈의 사용이 증가하고 있다. SCP 모듈 내부는 강재와 콘크리트의 일체 거동을 위해 스터드로 연결되어 있어 고유동 콘크리트의 사용이 요구된다. 고유동 콘크리트는 일반적으로 많은 단위결합재량를 가지기 때문에 수화열 및 수축의 증대, 비경제적인 강도 발현 문제 등이 발생한다. 따라서 본 연구에서는 저분체 기반 고유동 콘크리트 최적 배합을 선정하기 위해 재료적 특성에 따른 고유동 콘크리트의 유동성 및 철근의 간극 통과성능을 검토하고, 펌프카를 활용하여 펌핑 전후에 따른 콘크리트의 물성을 검토하며, 최종적으로 강재와 강재 사이를 콘크리트로 채우는 SCP Mock-up 부재에 대하여 고유동 콘크리트의 충전 성능을 평가하였다.

• 대한건축학회논문집:계획계
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• 제34권2호
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• pp.41-48
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• 2018

This study is expected to provide some basic data on how to apply more economical and efficient eco-friendly factors to reduce the carbon emissions. It has been scrutinized and analyzed the environmental factors of passive eco-friendly elements along with active eco-friendly elements as more efficient factors for energy conservation based on the case of a newly constructed broadcasting building with the green building certification in Sangam-dong DMC area. The first analysis was the energy consumption trends in Korea and the necessity of energy saving. Secondly, it was examined the energy consumption in the current status of the broadcasting building. Thirdly, it was looked into the correlation between the eco-friendly design application factors applied to the broadcasting building and the energy consumption types. As a result of the analysis, the application of fan and feed pump inverter along with ventilation system of waste heat recovery ventilation system were more meaningful in accordance with the economic feasibility of broadcasting buildings rather than economical effect of passive elements such as rooftop garden, reinforcement of building insulation. Also, the application of lighting control had the economical feasibility. Therefore, when it is intended to change the green building certification energy related evaluation items of the similar broadcasting building types, it is necessary to change the direction of adding weight to the more economical active element items in the future.

• 해양환경안전학회지
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• 제27권2호
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• pp.355-362
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• 2021

L.P SCR의 촉매 반응을 위해 선박의 발전기용 4행정 디젤엔진의 배기가스 온도를 높게 설계 할 수밖에 없었다. 본 연구의 목적은 밸브개폐시기와 연료분사시기를 조정을 통한 배기가스의 온도 감소가 L.P SCR의 운전조건을 만족시키고 고온으로 인한 발전기 엔진의 사고를 예방하기 위함이었다. 배기가스 온도를 하강시키기 위해 캠샤프트의 각도를 조정하고 연료분사펌프의 Shim을 추가하였다. 그 결과 최대폭발압력은 12.8 bar 증가하였고 터보차저 출구온도 평균값은 13.3 ℃ 하강하였다. 터보차저 출구에서 SCR 입구까지의 열손실을 감안하더라도 L.P SCR 운전조건인 SCR 챔버 입구 온도인 290 ℃를 만족하였다. 배기가스 온도 하강을 통해 디젤발전기의 안전운전이 가능하게 한 연구였다.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2743-2759
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• 2020

A detailed computational fluid dynamics (CFD) simulation analysis model was developed using ANSYS CFX 16.1 and analyzed to simulate the basic design and internal flow characteristics of a 180 MW small modular reactor (SMR) with a natural circulation flow system. To analyze the natural circulation phenomena without a pump for the initial flow generation inside the reactor, the flow characteristics were evaluated for each output assuming various initial powers relative to the critical condition. The eddy phenomenon and the flow imbalance phenomenon at each output were confirmed, and a flow leveling structure under the core was proposed for an optimization of the internal natural circulation flow. In the steady-state analysis, the temperature distribution and heat transfer speed at each position considering an increase in the output power of the core were calculated, and the conceptual design of the SMR had a sufficient thermal margin (31.4 K). A transient model with the output ranging from 0% to 100% was analyzed, and the obtained values were close to the T_hot and T_cold temperature difference value estimated in the conceptual design of the SMR. The K-factor was calculated from the flow analysis data of the CFX model and applied to an analysis model in RELAP5/MOD3.3, the optimal analysis system code for nuclear power plants. The CFX analysis results and RELAP analysis results were evaluated in terms of the internal flow characteristics per core output. The two codes, which model the same nuclear power plant, have different flow analysis schemes but can be used complementarily. In particular, it will be useful to carry out detailed studies of the timing of the steam generator intervention when an SMR is activated. The thermal and hydraulic characteristics of the models that applied porous media to the core & steam generators and the models that embodied the entire detail shape were compared and analyzed. Although there were differences in the ability to analyze detailed flow characteristics at some low powers, it was confirmed that there was no significant difference in the thermal hydraulic characteristics' analysis of the SMR system's conceptual design.

• KEPCO Journal on Electric Power and Energy
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• 제8권2호
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• pp.69-72
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• 2022

This paper actually investigates the load on major large-scale buildings in the downtown area, examines the economic feasibility of installing PV and ESS in a microgrid target building, and evaluates whether an electric vehicle capable of V2G through two buildings is effective as an economical analysis program (HOMER) was analyzed using. It is economical to install a mixture of ESS rather than using the whole PV, and it is shown that if there is an electric vehicle using the V2G function of EV, there is an economic effect to replace the PV. So that Incentives and policies are needed to replace a large area of PV and utilize the existing parking lot to lead EV as a resource of the microgrid. Currently, P2X technology that stores power as ESS or converts it to other energy to control when surplus renewable energy occurs in large-capacity solar power plants and wind farms, etc. This is being applied, and efforts are being made to maintain the stability of the system through the management of surplus power, such as replacing thermal energy through a heat pump. Due to the increase in electric vehicles, which were recognized only as a means of transportation, technologies for using electric vehicles are developing. Accordingly, existing gas stations do not only supply traditional chemical fuels, but electricity, and super stations that also produce electricity have appeared. Super Station is a new concept power plant that can produce and store electricity using solar power, ESS, V2G, and P2G. To take advantage of this, research on an urban microgrid that forms an independent system by tying a large building and several buildings together and supplies power through a super station around the microgrid is in full swing.

• 한국지열·수열에너지학회논문집
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• 제19권4호
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• pp.27-38
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• 2023

The Government the Republic of Korea is showing a lot of interest in net zero-energy buildings (NZEBs) to reduce energy consumption of buildings and to promote green growth policy in construction sector. The application of building passive technologies and renewable energies is essential to achieving NZEBs. Green remodeling reinforced the insulation of the exterior walls and roofs of the buildings and replaced high-efficiency windows and doors. In this study, the energy performance before and after green remodeling applied in a detached house was comparatively analyzed for baseline scenario and three different ones, ALT 1, ALT 2 and ALT 3. A building modeling and simulation software (DesignBuilder V7.0) with EnergyPlus (V9.4) calculation engine was used to calculate the energy demand and energy consumption for each scenario. Based on the calculation results of the building's energy demand for baseline, it was determined that the target building required more heating energy than cooling energy. The simulation results also showed that the implementation of building envelope performance improvement technologies (ALT 1) could notably decrease the heating energy consumption of the building. After the remodeling (ALT 1), the source energy consumption per unit floor area was assessed to be reduced by 65.2%, compared to prior remodeling of 338.7 kWh/m² -y. Meanwhile, ALT 2 can achieve energy savings of 67.7% and ALT 3 can achieve savings of 73.1%. Following completion of the remodeling project, actual construction costs, and on-site measurements and verification results will be gathered and compared with the simulation results. Additionally, economic analysis including construction costs and payback period will be conducted using actual site data.

• 대한기계학회논문집B
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• 제36권3호
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• pp.343-350
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• 2012

본 연구에서는 외부 개질기에 열원을 공급하기 위한 시스템 내에 가용한 열에너지의 활용 및 확보에 대한 해석을 위해서 외부 개질기를 연계한 평판형 SOFC 시스템의 해석 모델을 구축하고자 한다. 이러한 해석을 위한 모델 구축을 위해 Matlab simulink$^{(R)}$ 기반의 ThermoLib module을 사용하였으며, 구축된 해석 모델을 통하여 시스템의 성능 향상을 위한 구성 기법에 대해서 연구를 하였다. 시스템 구성 방법은 기존 시스템의 layout을 바꾸기 위해 공기극 출구가스 재순환 및 외부개질기와 촉매연소기를 통합한 개질반응시스템 적용, 개질기에 공급되는 혼합연료의 예열, 연료극 출구가스의 응축을 통한 연료 농도 향상 등을 고려하였다. 시뮬레이션의 해석 결과에서는 SOFC 시스템에 있어서 일반 연소기를 적용한 기준 시스템에 비하여 촉매 연소기를 사용한 시스템의 전기 효율이 12.13% 향상되었으며, 연료극 출구 가스를 응축시켜 버너로 연소시킨 시스템에서는 열효율이 76.12%로 가장 높았다.

• 공업화학
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• 제9권1호
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• pp.82-88
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• 1998

고효율 공냉형 흡수식 냉방기를 위한 신작동매체로 기존의 $LiBr-H_2O$계에 높은 흡수성과 용해성를 지닌 $LiNO_3$과 LiCl 무기물을 각각 첨가하여 제조하였다. 본 연구를 통하여 제조된 다성분계의 작동매체에 대한 용해도와 증기압을 측정하여 $LiBr-H_2O$계와 비교 분석하였으며, 이들에 대한 최적혼합비를 각각 구하였다. 용해도 측면에서 $LiBr-LiNO_3-H_2O$계의 경우, LiBr과 $LiNO_3$의 최적혼합 몰비는 5:1이었으며, 반면 $LiBr-LiNO_3-LiCl-H_2O$계의 경우 LiBr, $LiNO_3$, LiCl의 최적혼합몰비는 5:1:2로 나타났다. 한편 증기압은 $LiBr-H_2O$계에 $LiNO_3$의 첨가량이 증가하였으나, LiCl의 경우에는 첨가량이 증가함에 따라 감소하는 경향을 각각 나타내었다.

• 대한기계학회논문집 C: 기술과 교육
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• 제1권1호
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• pp.99-105
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• 2013

LNG 극저온기계기술 시험인증센터에 구축되는 LNG 선박용 펌프 및 압축기 성능시험에서 발생하는 증발가스는 안전을 위하여 전량 회수가 요구된다. 본 논문에서는 36 MTD 용량의 천연가스 재액화 시스템에 대한 기본 설계 연구를 수행하였다. 대기압, $-60^{\circ}C$, 일반적인 도시가스 조성비, 1,500 kg/hr 유량의 공급 가스를 기본 설계 조건으로 하여 공정 설계가 이루어졌고, 입구 온도 조건 및 가스 조성비에 따른 LNG 생산량 또한 계산하여 다양한 입구 설계 조건에 따른 시스템의 성능 변화를 비교, 분석하였다. 공정 설계 외에도 재액화 시스템의 핵심 기기인 송풍기, 압축기, 극저온 열교환기, 컴팬더의 제작 사양이 도출되었으며, 전력 및 냉각수의 유틸리티 요구조건 또한 기본 설계를 통해 도출되었다.