• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.67-75
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• 2015

PV module is conventionally connected in series with some solar cell to adjust the output of module. Some bypass diodes in module are installed to prevent module from hot spot and mismatch power loss. However, bypass diode in module exposed outdoor is easily damaged by surge voltage. In this paper, we study the thermal and electrical characteristics change of module with damaged bypass diode to easily find module with damaged bypass diode in photovoltaic system consisting of many modules. Firstly, the temperature change of bypass diode is measured according to forward and reverse bias current flowing through bypass diode. The maximum surface temperature of damaged bypass diode applied reverse bias is higher than that of normal bypass diode despite flowing equal current. Also, the output change of module with and without damaged bypass diode is observed. The output of module with damaged bypass diode is proportionally reduced by the total number of connected solar cells per one bypass diode. Lastly, the distribution temperature of module with damaged bypass diode is confirmed by IR camera. Temperature of all solar cells connected with damaged bypass diode rises and even hot spot of some solar cells is observed. We confirm that damaged bypass diodes in module lead to power drop of module, temperature rise of module and temperature rise of bypass diode. Those results are used to find module with a damaged bypass diode in system.

• 농업과학연구
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• 제50권3호
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• pp.395-406
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• 2023

The large amount of energy required for successful crop production is the main challenge in greenhouse cropping systems. As a response to this challenge a comprehensive evaluation of greenhouse energy consumption was carried out in two structurally similar single-span greenhouses with different thermal curtain positions, with particular attention to energy productivity, specific energy, net energy, and energy ratio. The greenhouses are used for strawberry production. In the R-greenhouse (RGH), the thermal curtain hanged directly at the roof ridge, whereas in the Q-greenhouse (QGH), the thermal curtain was placed 5° from an imaginary vertical axis, from the middle of the roof ridge downwards to the north side of the greenhouse roof. The relevant data were recorded using standard methods. The results indicated that the energy expended in the RGH and QGH systems was 2,186.48 and 2,189.26 MJ/m², respectively. Electricity and nitrogen fertilizer contributed the highest energy input in both greenhouses and in all seasons. The output energy was 3.12 and 3.82 MJ/m², respectively, in RGH and QGH in season I and 4.40 and 4.87 MJ/m² in season II. In terms of energy expended, there was no significant difference between the two greenhouses, nor between the two seasons. These results indicate that greenhouses of the size used in this investigation are not viable in terms of energy productivity, energy-use efficiency, and subsequent economic performance. However, further studies should be conducted to scale-up the information obtained from this investigation.

• 한국태양에너지학회 논문집
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• 제32권spc3호
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• pp.255-261
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• 2012

Since PV PCS uses output current sensor for ac output current control, the sensor's sensing value includes unnecessary offset inevitably. If PV inverter is controlled by the included offset value, it's output current will generate DC offset. The DC offset of output current for trans-less PV inverter is fatal to grid, which results in saturating grid side transformer. Usually DSP controller of PV inverter reads several times sensing value during initial operation and, finally, it's average value is used for offset calibration. However, if temperature changes, the offset changes, too. And also, the switch device is not ideal, both each switching element of the voltage drop difference and on & off time delay difference generate DC offset. Thus, to compensate for deadtime and the switch voltage drop, feedback control by output current DC offset should be provided to compensate additional distortion of the output current. The validity of the proposed method is confirmed through PSIM simulation.

• 에너지공학
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• 제21권1호
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• pp.47-54
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• 2012

정부는 에너지 절약시책의 일환으로 제1,2차 석유파동 후 1983년에 목동신시가지에 집단에너지 사업을 도입하였다. 이후 집단에너지산업의 공급규모는 꾸준히 증가추세를 보이고 있다. 이에 본 논문에서는 2009년도 산업연관표에 근거한 투입산출분석을 이용하여 집단에너지산업의 국민경제적 파급효과를 분석하고자 한다. 수요유도형 모형을 이용하여 집단에너지산업에서의 생산 혹은 투자가 다른 산업에 미치는 영향에 대하여 논의한다. 공급유도형 모형을 적용하여 집단에너지산업에서의 공급지장이 다른 산업에 미치는 효과에 대해 살펴본다. 레온티에프 가격모형을 이용하여 집단에너지산업의 가격 변동이 다른 산업의 산출물 가격에 미치는 영향에 대해 검토한다. 특히 집단에너지산업을 중심에 놓고 이를 외생화하여 분석하는 접근방법을 취했다. 분석 결과를 요약하자면, 집단에너지산업은 낮은 생산유발효과, 높은 공급지장효과, 낮은 물가파급효과, 낮은 전방연쇄효과, 낮은 후방연쇄효과를 가진다. 이러한 정량적 정보는 집단에너지산업을 위한 정책결정에 있어서 유용하게 활용될 수 있다.

• 자원ㆍ환경경제연구
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• 제12권1호
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• pp.29-48
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• 2003

The Steel Industry has made a significant contribution to the increase of energy use in Korea. This paper presents a method for development energy efficiency indicator in the steel industry based on the decomposing approach. This paper develops a logically consistent method for decomposing a change in energy consumption into the effects of three factors structural change, energy intensity and output level. Numerical illustration of the method is given using 1992~2001 data for energy consumption in a virtual works. The most dominant factor is revealed to be the output effect. The energy intensity for the steel industry has increased and the effect of such a growth was relatively strongly reflected in the decomposition analysis. The structural effect turned out to be also important during the periods.

• 한국태양에너지학회 논문집
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• 제34권1호
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• pp.28-38
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• 2014

The effects of geometric parameters (stack position, stack length, resonator tube length) and varying input power over acoustic energy output were investigated. The acoustic laser kit (Garret 2000) was used for the construction of TA lasers. A series of sound pressure level measurements in different orientations did not differ significantly confirming that the sound wave generated could be assumed as a spherical wave. An increase in acoustic pressure was recorded with respective increase in input power, stack and resonator tube lengths owing to their relative influence over heat transfer rate and critical temperature gradient across the stack.

• 전기학회논문지
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• 제66권3호
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• pp.486-492
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• 2017

In recent years, renewable energy sources have been mentioned as solution to environmental regulation and energy supply-demand. Energy storage systems are needed to mitigate the intermittent output characteristics of renewable energy sources and to operate micro grid efficiently using renewable energy generation systems. However, despite the necessity of energy storage system, this cannot secure the economical efficiency of the energy storage system by high initial cost. In this paper, a micro grid is constructed to supply electric power to industrial customers by using solar power generation system and energy storage system among renewable energy generation power sources and operated to improve energy independence. In the case study, we use photovoltaic system which is representative renewable energy generation system. Unlike conventional photovoltaic system, this system uses floating photovoltaic system with the advantage of having high output and no land area limitations. It is operated for the purpose of improving energy independence in the micro grid. In order to secure economical efficiency, the energy storage system operates a micro grid with a minimum capacity. Finally, this paper calculates the appropriate subsidy for the energy storage capacity.

• 한국광학회지
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• 제7권3호
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• pp.244-249
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• 1996

DIAL의 레이저광원으로 사용하는 다중통과 Ti:sapphire의 증폭시스템을 각-다중방식으로 개발하고 출력에너지와 스펙트럼 특성을 조사하였다. 개발된 2단의 다중통과 증폭기의 특성은 790nm파장에서 최대 출력에너지는 22mJ, 증폭이득은 20dB, 펌핑에너지에 대한 출력효율은 18%이다. 또한 스펙트럼선폭은 파장가변 범위 705-845nm에서 0.15$cm^{-1}$ /(9.3pm)이다. 최대 출력에너지 때 레이저빔 발산각은 X, Y축에서 각각 1.1, 1.5mrad이며 레이저빔의 quality factir N$^{2}$은 2.6이다.

• 전기학회논문지
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• 제63권3호
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• pp.338-342
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• 2014

Energy storage is a key issue when integrating large amounts of intermittent and non-dispatchable renewable energy sources into electric power systems. To maintain the instantaneous power balance and to compensate for the influence of power fluctuations from renewable sources, flexible capability for power control is needed. Adjustable Speed Pumped Storage Power Generator is pumped storage unit that is adjustable for pump output adjustments as well as the highest efficiency operations because it has fast response time. In this paper we address the adjustable speed pumped storage power generator for frequency control against the intermittence of wind turbine output and calculate the appropriate capacity of adjustable speed pumped storage power generator.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.615-619
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• 2009

This paper is investigated to variation of wave power generation operation rate, operating capacity and output with the wave conditions represented by wave height-period window. By the use of the long-term wave data from 1979 to 2002 which is provided by Korea Ocean Research & Development Institute(KORDI), we calculated the monthly variation of significant wave height(Hs), zero-up crossing period(Tz) and distribution of wave appearance rate. And using the same wave data, it was charted the Hs-Tz and wave-energy scatter diagrams.