• 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.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.68-73
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• 2009

The purpose of this study is to assess key competencies, especially mathematical skills and communications skills, in order to find disaccord between industry and college in the field of automotive electricity on technical engineering education. For this study, an assessment sheet is consisted of nine questions items. Four questions items of them are to assess mathematical skills and five questions items of them are to assess communications skills. 134 copies returned assessment sheets are analyzed after data cleaning and it is concluded that disaccord between industry and college in the field of automotive electricity on technical engineering education is found.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.174-176
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• 2007

Because of accident or leak of electricity, high voltage electricity can be conducted to vehicle chassis and damage human. Therefore the unit for detecting ground fault is necessary to minimize loss of life or equipment damage. Isolation resistance must be monitored for detecting ground fault. GFD(Ground Fault Detection) unit continually generate the pulse voltage between high voltage network and chassis. This will be sensing the returned current, calculate the isolation resistance and make decision the ground fault. This paper describes the method detecting ground fault.

• 대한공업교육학회지
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• 제31권2호
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• pp.177-202
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• 2006

이 연구의 목적은 전기 전자 통신 계열 공업교사들의 교수능력 수준과 교육요구를 구명하는데 있었다. 연구목적의 달성을 위해 250개 전기 전자 통신 관련 학과에 근무하는 750명의 전기 전자 통신 계열 공업교사를 대상으로 설문 조사를 실시하였다. 자료수집에 사용된 조사 도구는 3개 영역, 총 30개 교수능력에 대한 중요성 인식 수준과 현재의 교수능력 수준을 5점 리커트 척도로 응답하도록 구성하였다. 최종분석에 443부가 사용되었으며, 각 교수능력에 대한 교육요구는 보리치(Borich)의 교육요구도 계산공식을 사용하여 산출하였다. 주요 연구 결론은 다음과 같다. 첫째, 전기 전자 통신 계열 공업교사들은 30가지 교수능력에 대하여 평균적으로 모두 중요하다고 인식하고 있다. 특히, 교수능력 가운데 학생들의 수준과 흥미를 파악하는 능력에 대하여 가장 중요하다고 인식하고 있다. 둘째, 전기 전자 통신 계열 공업교사들은 30가지의 교수능력에 대한 중요성 인식 수준보다 낮은 수준의 교수능력을 가지고 있다. 특히, 교수능력 중 '실습시 시범보이기'에 대한 능력수준이 가장 높으나, '모의학습법 적용'에 대한 능력수준이 가장 낮다. 셋째, 교수능력 중 전기 전자 통신 계열 공업교사들의 교육요구가 높은 항목은 '학생들의 수준과 흥미 파악', '문제해결법 적용', '학습내용 재구성', '성취할 수업목표 설정' 등이고, 반면에 교육요구가 가장 낮은 항목은 '컴퓨터 매체 활용'이다. 넷째, 전기 전자 통신 계열 공업교사들의 교수능력에 대한 교육요구 순위는 성별, 학력, 교직경력, 산업체 근무경험, 근무지, 학교 설립유형에 따라 차이가 있다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1397-1405
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• 2009

In recent decades, exergy analysis has been holding spotlight as a useful tool in the design, assessment, optimization, and improvement of energy system. This paper presents the results of the energy and exergy analysis of a steam turbine cogeneration system for industrial complex using two efficiency concepts of conventional one and exergetic one. In order to obtain the destroyed exergy of each component, mathematical analysis is conducted by using exergy balance and the second law of thermodynamics, according as the parameters are changed, such as the ratio of returned process steam, process steam supplied, temperature and pressure of boiler and power. The computer program developed in this study can determine the efficiencies and exergy destroyed at each component of cogeneration system. As a result of this study, a component having the largest destroyed exergy was boiler. And closed and opened feedwater heater had the lowest one. The affects to the cogeneration system due to the variation of process steam flow and return rate of condensed water is shown that the total electric power efficiency(${\eta}_E$) is decreased as increasing the return rate of condensed water under constant process steam flow. As the boiler pressure is increased for the more production of electricity, the efficiency of cogeneration system was decreased.

• International Journal of Knowledge Content Development & Technology
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• 제11권2호
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• pp.23-36
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• 2021

Makerspace offers an innovative way for university libraries to render services and achieve its core objectives. However, there is low level of adoption in Nigerian university libraries, hence the need to investigate the personnel's perception towards makerspace as an innovative learning platform. To achieve this, the descriptive research design was used to elicit data with the aid of a structured questionnaire, from the 96 library personnel in John Harris Library, University of Benin. Of the 96 copies of questionnaire distributed, 68 copies were returned and analyzed using descriptive statistics. The results showed that the library personnel were familiar with makerspace even though they still require more information about it. Also, that makerspace gives students the opportunity to acquire ew skill and enhances collaboration among learners. Moreover, the study revealed that budget constraints, high cost and maintenance of equipments, erratic power supply and lack of staff training are some of the perceived challenges to makerspace implementation. Consequently, the study revealed that university libraries should strategize on how to increase allocation of funds, organize makerspace webinar for personnel, ensure stable electricity supply and create a dedicated space for makerspace in the library. In conclusion, makerspace will provide students with the technological exposure and creative abilities required for the future, and as such effective planning should be made for its deployment and sustainability in Nigerian university libraries.

• 한국산학기술학회논문지
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• 제17권10호
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• pp.86-92
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• 2016

하이브리드 자동차나 전기 자동차에는 대용량의 배터리를 장착하여 동력 및 전장품의 전원으로 사용하고 있다. 대용량의 배터리를 이용하여 ECU(Electronic control unit) 및 조명, 라디오, 네비게이션 등의 전장품의 전원으로 사용하기 위해서는 DC 240-400V의 높은 전압을 DC 12-14V의 낮은 전원으로 변환해 주는 DC 컨버터가 필요한데 이것을 LDC(Low Voltage DC-DC Converter)라 한다. LDC는 생산 공정 중에 잠재적인 불량을 줄이기 위해 장시간의 에이징(Aging)을 실시하고 있다. 일반적인 에이징 방법으로는 LDC가 DC-DC 컨버터이기에 입력에 직류전원공급기와 출력에 전자부하기를 연결하여 사용한다. 안정적인 동작을 위해 LDC 보다 10%이상 큰 용량의 제품을 사용하며, 출력에 걸리는 전력을 100% 열로 소비하는 구조이다. 때문에 LDC를 테스트 위해 2개의 장비를 사용함에 따른 부피의 문제와 전자부하기의 발열에 따른 문제가 존재한다. 이에 본 논문에서는 부하장치에서 열로 소비되는 전기의 상당부분을 입력 측으로 되돌려 보내는 재생형 방식의 부하시험방법을 제안하고 재생형 부하 시험기의 효율 개선을 통하여 열로 소비된 전기의 80% 이상 절감을 실현하였다.