• 설비공학논문집
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• 제18권2호
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• pp.158-162
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• 2006

Micro gas turbine (MGT) has received attention recently as a small-scale distributed power source. Due to many advantages such as their small size, low maintenance cost and minimal vibrations during operation, they are expected to become widespread in a wide range of applications. The exhaust heat emitted by the MGT is in the form of an exhaust gas that is about $270^{\circ}C$ which is an extremely clean gas. Korea Gas Corporation (KOGAS) has researched performance characteristics of a cogeneration system combining 28kW class MGT and 13 USRT class absorption hot and chilled water generator in the local condition. The present results of this study can be summarized as follows: (1) in heating mode, the total efficiency of cogen. system is about $65\%$ and heating capacity is 33kW at 25kW MGP power (2) in cooling mode, COP is about 0.6 at 22kW MGT power.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.247-255
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• 2012

Daylighting has a very effective role in reducing power consumption and improving indoor environments in office buildings. Previously, it was not under consideration as a major source of renewable energy due to poor reliability in the design. Optical fiber as a transmission medium in the daylighting system demands uniform distribution of light to solve cost, heat, and efficiency issues. Therefore, this study focuses on the uniform distribution of sunlight through the fiber bundle and to the interior of the building. To this end, two efficient approaches for the fiber-based daylighting system are presented. The first approach consists of a parabolic mirror, and the second approach contains a Fresnel lens. Sunlight is captured, guided, and distributed through the concentrator, optical fibers, and lenses, respectively. At the capturing stage, uniform illumination solves the heat problem, which has critical importance in making the system cost-effective by introducing plastic optical fibers. The efficiency of the system is increased by collimated light, which helps to insert maximum light into the optical fibers. Furthermore, we find that the hybrid system of combining sunlight and light emitting diode light gives better illumination levels than that of traditional lighting systems. Simulation and experimental results have shown that the efficiency of the system is better than previous fiber-based daylighting systems.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.79.1-84
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• 1995

The thermal analysis method containing micro drilling characteristic is proposed for the first time. There are such problems in thermal analysis of micro hole drilling as the thermal modeling complexity of drilling process and the undesirable micro drilling characteristic. Especially, the undesirable micro drilling characteristic prevents our using conventional thermal modeling. To model the thermal behavior of the micro drilling process, the finite different method, where heat source vectors are distributed by the measured rhrust and torque, is proposed. This method agrees with thermal behavior of the real system. And, it enable to predict the temperature field near the drill during. The validity of this method is verified in comparing with experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.456-461
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• 2003

A fuel cell is an electrochemical device in which the energy of a chemical reaction is converted directly into electricity. By combining hydrogen fuel with oxygen from air, electricity is formed, without combustion of any form. Water and heat are the only by-products when hydrogen is used as the fuel source. Fuel cell stack consists of multi-layered unit cells. A unit cell consists of MEA and bipolar plates. The end plate of fuel cell stack should give a uniform distributed pressure to multi unit cell layers so as to reduce the contact resistance and to prevent the leakage of reactant gases and the damage of multi layer components. The current end plate is redundantly large and heavy. It makes the power per unit volume reduced. Topology optimization of end plate is conducted for mass reduction and enhancement of bending rigidity. The evaluation of the current design and the recommendation for the future design is remarked.

• 한국유체기계학회 논문집
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• 제13권6호
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• pp.57-62
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• 2010

MW-class gas turbines are suitable for distributed generation systems such as community energy systems(CES). Recently, biogas is acknowledged as an alternative energy source, and its use in gas turbines is expected to increase. Steam injection is an effective way to improve performance of gas turbines. This study intended to examine the influence of injecting steam and using biogas as the fuel on the operation and performance a gas turbine combined heat and power (CHP) system. A commercial gas turbine of 6 MW class was used for this study. The primary concern of this study is a comparative analysis of system performance in a wide biogas composition range. In addition, the effect of steam temperature and injected steam rate on gas turbine and CHP performance was investigated.

• Coupled systems mechanics
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• 제12권3호
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• pp.261-276
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• 2023

This article is an application of new modified couple stress thermoelasticity without energy dissipation in association with two-temperature theory. The upper and lower surfaces of the plate are subjected to an axisymmetric heat supply. The solution is found by using Laplace and Hankel transform techniques. The analytical expressions of displacement components, conductive temperature, stress components and couple stress are computed in transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerically simulated results are depicted graphically. The effect of two temperature is shown on the various components.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.96-101
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• 2005

Cogeneration is an energy conversion process, where electricity and useful heat are produced simultaneously in one process. Also, carbon dioxide emissions can be reduced as well. The cogeneration process may be based on the use of steam, gas turbines or combustion engines. However, there have been few models with an output of less than 100 kilowatt. In the present study, a spark ignited gas engine with generation output of 10 kilowatts was developed for micro cogeneration package. The gas engine shows 29.2$\%$ of thermal efficiency under Stoichiometric combustion and 33.6$\%$ of thermal efficiency under lean combustion. NOx emission shows less than 10ppm at 13$\%$ oxygen under stoichiometric combustion and about 100ppm at 13$\%$ oxygen under lean combustion.

• 자원ㆍ환경경제연구
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• 제30권4호
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• pp.557-579
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• 2021

집단에너지는 에너지전환의 중간단계이자, 분산전원으로서 전력구조에 미치는 영향이 크다. 하지만 최근 일부 집단에너지사업자의 수익성 악화로 인해 집단에너지사업의 문제가 대두되고 있다. 본 연구는 우리나라 집단에너지사업자의 기술적 생산효율성 추정을 통해, 주요 사업자의 기술적 생산효율성을 측정하였으며 이를 바탕으로 사업자의 수익구조 개선방안을 살펴보았다. 16개 집단에너지사업자의 2016~19년 세부 재무 및 생산 자료를 수집한 후, 패널 확률 프론티어모형을 이용하여 사업자들의 기술적 생산효율성을 추정하였다. 추정 결과, 증기공급병행, 대형 전기중심, 소규모 구역전기, 역송CHP 사업자 순으로 생산효율성이 높음을 확인하였다. 더 나아가 수익성 영향요인에 대해 살펴본 결과, 기술적 생산효율성은 전반적으로 수익성과 양(+)의 영향 관계를 가지나, 소규모 구역전기사업자와 같이 열 생산 비중이 높은 사업자는 수익성이 악화됨을 확인하였다. 이는 현재 열 판매 시장의 구조적 한계로 인한 현상이며, 수익성 개선을 위해서는 열 판매단가에 대한 조정이 필요함을 확인하였다.

• 에너지공학
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• 제19권1호
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• pp.8-15
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• 2010

새로운 발전설비의 건설부지 확보의 어려움을 극복하고 친환경적인 에너지시스템으로 분산형 초소형 가스터빈이 주목받고 있다. 분산형 초소형 가스터빈 발전시스템은 다음과 같은 장점을 가지고 있다. 첫째는 친환경성으로서 NOx < 9 ppm, 소음 < 65 dB, 둘째는 다양한 연료를 사용할 수 있으며 천연가스 뿐만 아니라, 디젤, 저발열량 신재생에너지원료, 등유이다. 셋째는 작은 면적대비 높은 출력을 얻을 수 있고 컴팩트한 건설이 가능하다. 1998년부터 미국에서 개발되어 캘리포니아 및 일본등에서 활발히 적용되고 있다. 기존의 대용량 발전시스템이 주로 바닷가 근처에 건설되었다면 본 시스템은 수요자 인근에 설치되어 열과 전기를 동시에 공급하고 있으며 다양한 적용처에 에너지를 공급한다. 최근들어 국내에서는 신재생에너지의 개발, 보급이 아주 중요한 이슈로 떠오르고 있는 가운데, 이러한 소형 분산전원의 적용성이 많이 요구되고 있다. 따라서, 본 논문에서는 분산형 가스터빈의 최적 현장 적용을 위하여 필수적인 계통연계를 통한 병열운전 모델링과 실증시험 및 평가과정을 분석하여 에너지 품질을 정립하고자 한다.

• 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.