• KIEAE Journal
• /
• 제16권6호
• /
• pp.167-172
• /
• 2016

Purpose: The solar water heater with natural circulation has been used for several decades in the world as it is automatically operated without a pump and controller and is easy to maintain and repair. After the subsidy was offered from 2012, the solar water heater with natural circulation is becoming increasingly popular in Korea. Recently, the development of a wall-integrated solar water heater, which improves the applicability of buildings and prevents the overheating in the summer, is being developed. On the other hand, the design and performance evaluation data of solar water heaters are very inadequate, and analysis of heat and flow is required to develop a new type of solar water heater. Method: Therefore, in this study, we proposed a new simplified system analysis model that reflects heat and pressure loss from the test results of KS B ISO 9806-1 (Solar collector test method), assuming that the collector is a simple pipe system, the validity of which was verified through experiments. Result: As a result, first, the RMSE of the system circulation flow rate and the average temperature of the inlet and outlet of the collector according to the experimental results and the simulation are 0.05563 and 0.88530, respectively, which are very consistent. Secondly, the mass flow rate is increased linearly with the increase of the solar radiation, and the mass flow rate is 0.0104 ~ 0.0180kg/s in the range of $200{\sim}380W/m^2$ of solar irradiance. Compared with the test flow rate 0.0764kg / s of the test collector, it showed a level of less than 20%.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제4B권2호
• /
• pp.86-91
• /
• 2004

PV power generation, which directly converts solar radiation into electricity, contains numerous significant advantages. It is inexhaustible and pollution-free, silent, contains no rotating parts, and has size-independent electricity conversion efficiency. The positive environmental effect of photovoltaics is that it replaces the more polluting methods of electricity generation or that it provides electricity where none was available before. This paper highlights a novel simple method to abstract the entire parameters of the solar cell. In development, design and operation of PV power generation systems, a technique for constructing V-I curves under different levels of solar irradiance and cell temperature conditions using basic characteristic values of the PV module is required. Everyone who has performed manual acquisition and analysis of solar cell I versus V data would agree that the job is tedious and time-consuming. A better alternative is to use an automated curve tracer to print out the I versus V curves and compute the four major parameters; $V_{oc}$, $I_{sc}$, FF, and . Generally, the V-I curve tracer indicates only the commonly used solar cell parameters. However, with the conventional V-I curve tracer it is almost impossible to abstract the more detailed parameters of the solar cell; A, $R_{s}$ and $R_{sh}$ , which satisfies the user, who aims at the analysis of the development of the PV power generation system, that being advanced simulation. In this paper, the proposed method provides us with satisfactory results to enable us to abstract the detailed parameters of the solar cell; A, $R_s$ and $R_{sh}$.>.

• Current Photovoltaic Research
• /
• 제10권3호
• /
• pp.77-83
• /
• 2022

Renewable energy is receiving attention again as a way to realize carbon neutrality to overcome the climate change crisis. Among renewable energy sources, the installation of Photovoltaic is continuously increasing, and as of 2020, the global cumulative installation amount is about 590 GW and the domestic cumulative installation amount is about 17 GW. Accordingly, O&M technology that can analyze the power generation and fault diagnose about PV plants the is required. In this paper, a study was conducted to diagnose fault using I-V curves of PV strings and deep learning. In order to collect the fault I-V curves for learning in the deep learning, faults were simulated. It is partial shade and voltage mismatch, and I-V curves were measured on a sunny day. A two-step data pre-processing technique was applied to minimize variations depending on PV string capacity, irradiance, and PV module temperature, and this was used for learning and validation of deep learning. From the results of the study, it was confirmed that the PV fault diagnosis using I-V curves and deep learning is possible.

• Journal of Ecology and Environment
• /
• 제42권4호
• /
• pp.198-204
• /
• 2018

Background: The effective use of habitats is essential for the successful adaptation of a species to the local environment. Although habitats exhibit a hierarchical structure, including macro-, meso-, and microhabitats, the relationships among habitats of differing hierarchy have not been well studied. In this study, we studied the quantitative measures of microhabitat use of Gekko japonicus from three field populations in Japan: one at Tsushima Island, one at Nishi Park, Fukuoka, and one at Ohori Park, Fukuoka. We investigated whether land cover type, a higher hierarchical habitat component, was associated with quantitative microhabitat use, a lower hierarchical component, in these populations. Results: The substrate temperature where we located geckos (SubT) and the distance from the ground to the gecko (Height) were significantly different among the three populations. In particular, SubT on Tsushima Island was lower than it was in the other two populations. Irradiance at gecko location and Height were significantly different among the land cover types. In particular, Height in evergreen needleleaf forest was significantly lower than that in deciduous broadleaf forest. Furthermore, significant interactions between population and land cover type were observed for the SubT and Height variables. Conclusions: The quantitative measures of microhabitat use of G. japonicus varied with population and land cover type, which exhibited significant interaction effects on microhabitat use variables. These results suggest that higher hierarchical habitat components can affect the quantitative measures of lower hierarchical microhabitat use in nocturnal geckos.

• 통합자연과학논문집
• /
• 제15권3호
• /
• pp.99-110
• /
• 2022

Solar photovoltaic (PV) system shows a non-linear current (I) -voltage (V) characteristics, which depends on the surrounding environment factors, such as irradiance, temperature, and the wind. Solar PV system, with current (I) - voltage (V) and power (P) - Voltage (V) characteristics, specifies a unique operating point at where the possible maximum power point (MPP) is delivered. At the MPP, the PV array operates at maximum power efficiency. In order to continuously harvest maximum power at any point of time from solar PV modules, a good MPPT algorithms need to be employed. Currently, due to its simplicity and easy implementation, Perturb and Observe (P&O) algorithms are the most commonly used MPPT control method in the PV systems but it has a drawback at suddenly varying environment situations, due to constant step size. In this paper, to overcome the difficulties of the fast changing environment and suddenly changing the power of PV array due to constant step size in the P&O algorithm, least mean Square (LMS) methods is proposed together with P&O MPPT algorithm which is superior to traditional P&O MPPT. PV output power is predicted using LMS method to improve the tracking speed and deduce the possibility of misjudgment of increasing and decreasing the PV output. Simulation results shows that the proposed MPPT technique can track the MPP accurately as well as its dynamic response is very fast in response to the change of environmental parameters in comparison with the conventional P&O MPPT algorithm, and improves system performance.

• Journal of Plant Biotechnology
• /
• 제37권4호
• /
• pp.425-441
• /
• 2010

Forages are the backbone of sustainable agriculture. They includes a wide variety of plant species ranging from grasses, such as tall fescue and bermudagrass, to herbaceous legumes, such as alfalfa and white clover. Abiotic stresses, especially salinity, drought, temperature extremes, high photon irradiance, and levels of inorganic solutes, are the limiting factors in the growth and productivity of major cultivated forage crops. Given the great complexity of forage species and the associated difficulties encountered in traditional breeding methods, the potential from molecular breeding in improving forage crops has been recognized. Plant engineering strategies for abiotic stress tolerance largely rely on the gene expression for enzymes involved in pathways leading to the synthesis of functional and structural metabolites, proteins that confer stress tolerance, or proteins in signaling and regulatory pathways. Genetic engineering allows researchers to control timing, tissue-specificity, and expression level for optimal function of the introduced genes. Thus, the use of either a constitutive or stress-inducible promoter may be useful in certain cases. In this review, we summarize the recent progress made towards the development of transgenic forage plants with improved tolerance to abiotic stresses.

• 전력전자학회논문지
• /
• 제14권2호
• /
• pp.89-95
• /
• 2009

태양광발전시스템에서 태양전지의 최대전력점 추적(MPPT, Maximum Power Point Tracking)은 중요한 부분이다. MPPT 알고리즘은 태양전지가 주어진 일사량 및 온도에 의해 최대전력점에서 동작할 수 있도록 전압($V_{MPP}$), 전류($I_{MPP}$)를 찾는다. 기존의 P&O, IncCond 알고리즘은 듀티를 증가 혹은 감소시키기 위하여 마이크로 프로세서나 DSP를 필요로 한다. 본 논문에서는 간단하면서 빠른 아날로그 MPPT 알고리즘을 제안한다. 이 방식은 기존 방식과 비교해서 매우 빠르게 MPP를 추적할 수 있으며 구현하기 쉽다. 또한 급격히 변하는 일사량에 기존 방식보다 대처가 빠르며 높은 효율을 보여준다.

• 한국항해항만학회지
• /
• 제31권3호
• /
• pp.229-233
• /
• 2007

본 논문은 브이용 PV 시스템 성능과 최대전력점추적기의 알고리즘에 대하여 기술하고자 한다 현재 운영되고 있는 브이는 대부분 태양광을 활용한 독립형 전력 시스템을 이용하고 있다. 이러한 태양광 전력 시스템은 직류 출력 특성을 가지고 있으며 직류 버스와 연결된다. 태양광 전지판의 I-V 출력 특성은 일사량, 전지판의 온도에 따라 변화하며 태양광 전지 마다 그 특성이 각기 다르게 나타나기 때문에 태양광 전지는 최대전력추적방식의 알고리즘에 의해 운영되어야 한다. 이에 본 논문은 태양광 전지의 특성, 최대전력추적방식, 태양광 전지판의 최적경사각을 논의하고자 한다.

• 한국항공우주학회지
• /
• 제38권6호
• /
• pp.577-585
• /
• 2010

본 논문은 태양복사에너지를 고려한 지상 물체에서 방출되는 적외선 복사휘도를 예측하는 소프트웨어 개발 중 BRDF 데이터를 고려한 적외선 복사휘도를 분석한 내용을 다루었다. 물체 표면에서 방출되는 적외선 복사휘도는 물체의 표면온도 및 광학적 표면 특성을 이용하여 계산할 수 있다. BRDF는 물체 표면에 입사되는 에너지와 반사되는 에너지의 관계로 나타낼 수 있는 백분율로 정의하며 적외선 복사휘도를 분석하는 데 매우 중요한 자료로 사용된다. 본 논문에서는 중적외선 및 원적외선 영역에 대하여 태양이 존재하는 시간동안 다양한 재질의 광학적 표면 특성에 따른 적외선 영상을 생성하여 분석하였다. 연구결과 물체 표면의 복사율 및 BRDF 등은 물체의 적외선 영상에 매우 중요한 영향을 미치는 것을 확인하였으며, 특히 태양의 영향을 받을 경우 MWIR 영역의 복사휘도는 수치적으로 최대 10배까지 신호량의 차이를 보일 수 있음을 확인하였다.

• 한국전산유체공학회지
• /
• 제22권1호
• /
• pp.88-94
• /
• 2017

The IR signal entering into a sensor is composed of the following components: the self-emitted component directly from the object surface, the reflected components of the solar and sky irradiance at the object surface, and the scattered component by the atmosphere without reference to any object surfaces. The self-emitted and reflected components from the object can be lowered by the atmospheric layer between the object and the IR sensor. The principle factors influencing the atmospheric transmittance are the air temperature, the relative humidity and the observation distance. Previous studies on IR signal transmission through the atmosphere are focused on uniform atmospheric conditions and the non-uniform nature of the atmosphere was not properly treated in modeling. In this study, we use the local atmospheric transmittance to simulate the non-uniform atmosphere in analyzing the IR signal from the object surface. The results show that the nonuniform analysis of the atmosphere becomes more important as the wavelength of IR signal increases.