• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1540-1547
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• 2013

The energy economic analysis of the standard rural house model with PV system was performed based on annual energy demand calculation using the EnergyPlus to contribute in reducing building energy which occupies 25% of national energy consumption and in developing a low-energy & eco-friendly house model. Two types of PV system installation was considered to cover electricity demand for cooling, electric, and heating devices. For the selected house model, heating energy demand is 7 times higher than cooling energy demand. For the Case1, it is favorable to use electricity from PV system for cooling and electric devices and to sell surplus electricity. For the Case2, it is favorable to use electricity from PV system for cooling, electricity and heating devices and to sell surplus electricity. Considering the installation cost of PV system and heat pump air conditioning system, the break-even point of Case1 and Case2 are about 13 and 11 years respectively. Although the installation cost of Case2 is more expensive, Case2 provides three times more profit than Case1 after the break-even point. Because the expected average life time of the selected PV system is 25 years, Case2 is more favorable option for the given standard rural house model.

• Plant Journal
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• v.12 no.1
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• pp.29-36
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• 2016

It is becoming increasingly important to make use of alternative energy source. because It is not able to rely on only fossil fuel for the recent increasing demand of energy consumption. With this situation, lots of studies for utilizing low grade energy such as industrial waste heat, solar energy, and geothermal energy have been conducted. The aim of this study is to predict the operation characteristics of working fluid by using performance analysis program (ThermoFlex) through the system analysis which is not mixing district return water but using ORC(Organic Rankine Cycle, hereinafter ORC) as a downstream cycle when accumulating district heating (hereinafter DH). In this study, We conducted the performance analysis for the case which has the district heating water temperature($120^{\circ}C$) and Flow rate of $163m^3/h$ (including District Heating return water flow), and examined several working fluid which is proper to this temperature. The case using R245fa (which is the best-case) showed 269.2kW power output, 6.37% efficiency. Additionally, Cut down on fuel was expected because of the boiler inlet temperature increase by being Formed $57.3{\sim}85^{\circ}C$ in a temperature of district heating return water, depending on a pressure change of a condenser in ORC system.

• Resources Recycling
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• v.28 no.5
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• pp.3-18
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• 2019

Due to the increasing demand for clean energy, the consumption of lithium ion batteries (LIBs) is expected to grow steadily. Therefore, stable supply of lithium is becoming an important issue globally. Commercially, most of lithium is produced from the brine and minerals viz., spodumene, although various processes/technologies have been developed to recover lithium from other resources such as low grade ores, clays, seawaters and waste lithium ion batteries. In particular, commercialization of such recycling technologies for end-of-life LIBs being generated from various sources including mobile phones and electric vehicles(EVs), has a great potential. This review presents the commercial processes and also the emerging technologies for exploiting minerals and brines, besides that of newly developed lithium-recovery-processes for the waste LIBs. In addition, the future lithium-supply is discussed from the technical point of view. Amongst the emerging processes being developed for lithium recovery from low-grade ores, focus is mostly on the pyro-cum-hydrometallurgical based approaches, though only a few of such approaches have matured. Because of low recycling rate (<1%) of lithium globally compared to the consumption of lithium ion batteries (56% of lithium produced currently), processing of secondary resources could be foresighted as the grand opportunity. Considering the carbon economy, environment, and energy concerns, the hydrometallurgical process may potentially resolve the issue.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.243-248
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• 2013

Internal combustion engines typically expel 30%-40% of the energy supplied by fuel to the environment through their exhaust system. Therefore, further significant improvements in the thermal efficiency of IC engines are possible by recovering the waste heat from the engine exhaust gas. With this fact in mind, a numerical simulation was carried out to investigate the potential of using thermoelectric generation with an internal combustion engine for waste heat recovery. Physical parameters such as the exhaust temperature and mass flow rate were evaluated in the exhaust system, and the optimum location for inserting a thermoelectric generator (TEG) into the system was determined. The TEG will be located in the exhaust system and will use the energy flow between the warmer exhaust gas and the external environment. The optimum position of the temperature distribution and the TEG performance were predicted through numerical analysis. The experimental results obtained showed that the power output significantly increases with the temperature difference between the cold and hot sides of the TEG.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.119-123
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• 2014

The main purpose of reactive power compensation monitoring system is to manage factory electrical installation efficiently by On-Off switching reactive power compensation equipment. The existing reactive power compensation monitoring system is only able to be managed by operator whenever electrical installation needed reactive power. Therefore, it may be possible for propagating the installation's faults when operator make the unexpected mistakes. To overcome the unexpected mistakes, in this paper, the author presents a reactive power compensation monitoring system for factory electrical installation using active database. by using active database production rule, stated system can minimize unexpected mistake and can operate centralized monitoring system efficiently. Test results on the five factory electrical installations show that performance is efficient and robust.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.109-109
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• 2017

전 세계적으로 기후변화, 인구증가, 도시화에 따른 물, 에너지, 식량 등 필수 자원의 수요량 증가로 인한 수급 불균형으로 글로벌 자원안보 위기가 대두되고 있다. 특히, 국내의 경우 경제성장로 인한 중산층 증가와 도시 인구 팽창에 따른 물, 에너지, 식량 등 필수 자원에 대한 수요 증가로 인해 유한한 자원에 대한 대응책이 시급한 실정이다. 또한 국내 자원의 대외 의존성이 높아 국제 자원 시장에 크게 영향을 받기 때문에 물-에너지-식량의 연계를 통한 자립적 자원확보가 필요하다. 국내에서도 수자원 자체만의 기존 기술 한계를 극복하기 위한 물-에너지, 물-식량 연계신기술 개발과 지속가능한 활용방안이 필요한 실정으로 현재 미국, 일본, 유럽 등 주요 선진국을 중심으로 물관리와 연계한 에너지의 효율화 및 수자원이 갖는 에너지의 회수와 적극적 활용이 추진되고 있다. 이를 반영하여, 국내의 경우 독립적으로 구분되는 이수, 치수, 물순환 건전화 등 주요 물관리 이슈에 대하여 에너지, 식량 분야를 연계한 통합적이고 효율적인 지속가능 방안제시가 필요하다. 이를 위해 자원안보의 선제적 대응을 위한 구체적이고 실질적인 물-에너지-식량의 연계 기술이 필요하며, 국내 실정에 적합한 기술의 도입이 필요하다. 즉 (1) WEF 데이터공유 및 범정부적 의사결정을 위한 다부처 협업체계 구축을 위한 Bigdata기반 부처간 데이터베이스 구축 및 공유 (2) 기후변화 적응 자원연계 솔루션 개발 및 넥서스 영향평가 툴 개발을 위한 자원 효율성 증대를 위한 연계 기술 고도화 (3) 국내(미래넥서스시티 versus 지자체자립형넥서스마을), 해외 on-demand형의 미래자원관리 패키지기술 실증을 위한 국내외 Testbed구축 및 운영 (4) 기술의 실현을 위한 제도, 정책의 개선 및 국민 공감대 형성을 위한 WEF 넥서스 거버넌스 수립 및 개선으로 구분할 수 있다. 이를 통해, 물-에너지-식량 분야 상호 연계를 통한 분야별 "생산-가공-유통처리" 효율 30% 개선, 20C SOC 시설산업기반에서 21C 사회 인프라 국민 서비스 산업으로 전환을 통한 국가 신산업기반 구축, 4차 산업혁명의 Data Technology 분야에서 세계 최초의 공공기반 WEF 연계 패키지 기술 개발 들이 가능할 것으로 판단된다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.201-206
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• 2022

Energy harvesting is a concept introduced in 1954 by Bell Labs in the US while conducting research on solar cells that convert sunlight into energy. Such energy harvesting technology is a technology that collects wasted or unused energy in daily life and recycles it as electric power. In particular In the case of a photovoltaic power generation system, energy harvesting can be applied by storing electricity generated by using a battery to reduce power consumption generated by the inverter in the form of loss of power generation in cloudy weather compared to sunny days. Therefore, in this paper, energy harvesting technology is applied in the low sunlight section such as sunrise, sunset, and cloudy weather to improve the amount of power generation by recovering the power that is below the minimum operating voltage of the inverter and dissipated. Accordingly, the research contents were verified through the development of systems and algorithms according to the amount of solar power generation and the development of systems and algorithms using low power generated in sunset, sunrise, and other environments.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.396-396
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• 2022

생물전기화학적 혐기성소화(Bioelectrochemical anaerobic digestion; BEAD)는 소량의 전압공급을 통해 고농도 하·폐수의 효과적인 처리 및 에너지 회수가 가능한 처리방법으로, 기존 하·폐수처리공정(활성슬러지 및 그 변법)에서 벗어나기 위한 방법 중 하나로 연구되고 있지만, 내부저항 및 전극구조에 따른 물질전달저해로 인해 소규모 연구 위주로 진행되었다. 하지만 stainless steel(SS) 등 내부저항을 완화할 수 있는 전극재료 및 전극구조 개선 연구가 진행됨에 따라 BEAD 적용규모가 증가하는 추세이며, 본 연구에서는 100 L의 용량에서 전극재질 및 구조에 따른 적용적합성을 에너지효율 비교를 통해 평가하였다. 반응조는 비교를 위한 AD, 반응조 내부에 전극을 설치한 BEAD, 반응조 외부에 전극이 포함된 반응조를 추가한 ABEAD로 구성하였으며, AD 및 BEAD는 기계적 교반, ABEAD는 기계적 교반 및 펌프를 통한 bulk 용액 순환으로 물질전달이 이뤄졌다. 또한 BEAD는 탄소계 전극, ABEAD는 SS계 전극을 사용하였으며 두 반응조 모두 0.4 V의 전압을 공급하였다. 실험조건은 유효용량 100 L, 유기물부하율 3 kg/m³/d, HRT 20 days 및 중온소화(35℃)으로 운전하였다. 실험결과 AD, BEAD 및 ABEAD의 유기물제거율은 각각 평균 68.1 %, 68.9 %, 74.9 %로 전극 및 반응조의 분리를 통해 물질전달을 개선한 ABEAD에서 증가하였다. 에너지 생성량의 경우 AD에 비해 BEAD는 평균 229 kJ/d, ABEAD는 309 kJ/d가 추가 생성되었으며 유기물제거율이 높은 ABEAD에서 더 높은 에너지생산이 이뤄졌다. 마지막으로 전압공급으로 인한 에너지소비량은 BEAD는 평균 3.4 kJ/d, ABEAD는 평균 0.9 kJ/d로 전극의 낮은 생물적합성으로 인해 전극에서의 생화학반응이 적은 ABEAD가 에너지소비량이 낮았다. 따라서 본 연구에서는 SS 전극의 사용가능성 및 전극구조 개선에 따른 에너지효율성 향상을 확인할 수 있었으며, 추후 연구에 활용할 수 있을 것으로 기대된다.

• Clean Technology
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• v.24 no.2
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• pp.87-98
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• 2018

Phosphorus (P) is an essential and irreplaceable element for all living organisms, and it is widely used as a fertilizer. Unfortunately, it is estimated that phosphate reservoir is depleted within about 100 years. Sewage sludge ash (SSA) is an alternative resource for P recovery because of its high P content. However, SSA cannot be directly used as a fertilizer due to heavy metals in it and low P bioavailability. Thermochemical treatment with Cl donor is known to reduce heavy metal contents and increase P bioavailability of SSA. Literature review on thermochemical technologies of SSA for the reduction of heavy metals and bioavailability enhancement has been carried out to estimate the status of current P recovery technology and to develop strategic future research plan for P recovery. The review showed that $CaCl_2$ and $MgCl_2$ were the most effective Cl donors and reaction temperature (< $1000^{\circ}C$) was the critical operation condition for the reduction. The removal efficiency depends on the species of heavy metals. Thermochemical technology of SSA for P recovery showed the possibility of commercial application in the near future to overcome the coming crisis of human sustainability by P depletion, but it needs cost effectiveness and more ecofriendly process to reduce energy consumption.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.170-170
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• 2010

The energy conversion from the temperature difference between hot and cold source like ocean thermal energy conversion (OTEC), requires a long and large-diameter pipe (about 1000 to 10,000 meters long) to reach the deep water. The pipe diameter ranges from 2.8 meter for proposed early test systems, to 5 meter for large, commercial power generation systems. The pipe must be designed to resist collapsing pressures produced by water temperature and density differences, and the reduced pressure required to induce flow up the pipe. Other design considerations include the external-drag effect on the pipe due to ocean currents, and the wave-induced motions of the platform to which the pipe is attached. Various approaches to the pipe construction have been proposed, including aluminum, steel, concrete, and fiberglass. More recently, a flexible pipe construction involving the use of fiberglass reinforced plastic has been proposed. This report presents the results of a scaled fixed cold water pipe (CWP) model test program performed by EES(Engineering Equation Solver) to demonstrate the feasibility of this pipe approach.