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Dynamic analysis of a concentrating photovoltaic/concentrating solar power (CPV/CSP) hybrid system
摘要： Concentrating photovoltaic/concentrating solar power (CPV/CSP) systems suffer from varying irradiation and extreme working conditions. In this study, a dynamic physical model is developed for the CPV/CSP hybrid system to analyze the dynamic responses of several key parameters, such as the solar radiation saltation or linear variation to represent the typical weather variations. The results show that the hybrid system could rapidly reach the steady state in less than about 53 s after the solar radiation saltation increases or decreases by 10%. The response time reflects that the thermal hysteresis of the hybrid system is mainly determined by varying the outlet temperature of R134a from the solar thermal receiver. Meanwhile, when the solar radiation changes linearly, a lower gradient is beneficial to remit the thermal hysteresis of the hybrid system and improve the thermal stability, and the parameters could be treated as the steady state values with a gradient of less than 0.2 W m–2 s–1. Afterward, the quasi-steady state model was used to analyze the all-day dynamic performance of the hybrid system. It shows that the power output and the flow rate are directly related to the direct normal irradiance (DNI), while the outlet temperature of R134a vapor could be almost constant except for the starting and stopping periods.
关键词： solar radiation disturbance,concentrating solar power,dynamic performance,concentrating photovoltaic,transient simulation
更新于2025-09-19 17:13:59
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Specifications of Photovoltaic Pumping Systems in Agriculture || Photovoltaic Energy: Basic Principles
摘要： The sun is a star which provides nearly 95% of its energy to generate nearly all the energy available on the earth. In fact, the earth energy is a direct or indirect conversion form of the sun’s lights. For instance, the solar heat ensures the plants evaporation-transpiration by converting the sunlight energy into storable chemical form through the photosynthesis process, which allows the fauna and flora to be maintained in the earth. Moreover, the sunlight is the source of generating wind and wave energies, by causing temperature difference in the atmosphere. Additionally, sunlight generates the photothermal and photovoltaic energies, which are used to provide electrical and heat energies. Consequently, sun means life.
关键词： P-N junction,Silicon atom,Solar radiation,Photovoltaic energy,Solar cell efficiency
更新于2025-09-19 17:13:59
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Do optical sensor readings change throughout the day? An evaluation of two sensor systems
摘要： Optical sensors are useful tools for rapid and periodic assessment of plant nutritional status. However, the utility and potential of these sensors may be reduced if their readings change throughout the day. Therefore, this study aimed to assess the effects of time of day on measurements of the SPAD-502 chlorophyll meter and the GreenSeeker throughout the bean crop cycle. The treatments consisted of time of day for sensor measurements (8:00, 12:00, and 16:00 h) throughout six dates over the crop cycle. The results showed that measurements from the SPAD-502 and the GreenSeeker significantly changed according to time of day. The SPAD index at 16:00 h showed the lowest coefficient of variation (CV, 2.5%) and was on average, 3.05 ± 0.43, and 1.12 ± 0.25 SPAD units higher when compared to readings obtained at 8:00 and 12:00 h. Differently, the NDVI from the GreenSeeker showed the lowest CV (4.34%) at 8:00 h and was, on average, 0.06 ± 0.028 and 0.03 ± 0.01 units higher than measurements taken at 16:00 h and 12:00 h, respectively. Furthermore, the different times of sensor measurements present variations in air temperature and solar radiation, which directly influence the leaf water content and paraheliotropic movements. Thus, the indices from both sensors tend to show a high variability during different times of the day. Therefore, it is essential to create a consistent sampling protocol to reduce the variability of sensor measurements during the crop cycle.
关键词： Phaseolus vulgaris L,solar radiation,chlorophyll meter,precision agriculture,canopy reflectance sensor
更新于2025-09-19 17:13:59
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Solar Radiation
摘要： The sun’s structure and characteristics determine the nature of the energy it radiates into space. The first major topic in this chapter concerns the characteristics of this energy outside the earth’s atmosphere, its intensity, and its spectral distribution. We will be concerned primarily with radiation in a wavelength range of 0.25 to 3.0 μm, the portion of the electromagnetic radiation that includes most of the energy radiated by the sun. The second major topic in this chapter is solar geometry, that is, the position of the sun in the sky, the direction in which beam radiation is incident on surfaces of various orientations, and shading. The third topic is extraterrestrial radiation on a horizontal surface, which represents the theoretical upper limit of solar radiation available at the earth’s surface. An understanding of the nature of extraterrestrial radiation, the effects of orientation of a receiving surface, and the theoretically possible radiation at the earth’s surface is important in understanding and using solar radiation data, the subject of Chapter 2.
关键词： solar radiation,extraterrestrial radiation,diffuse radiation,solar geometry,spectral distribution,solar constant,beam radiation
更新于2025-09-16 10:30:52
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Potential impact of climate change on solar resource in Africa for photovoltaic energy: analyses from CORDEX-AFRICA climate experiments
摘要： The development of renewable electricity in Africa could be massive in coming decades, as a response to the rapid rising electricity demand while complying with the Paris Agreements. This study shows that in the high-resolution climate experiments of CORDEX-AFRICA, the annual mean solar potential is expected to decrease on average by 4% over most of the continent by the end of the century, reaching up to 6% over the Horn of Africa, as a direct result of decrease in solar radiation and increase in air surface temperature. These projections are associated with large uncertainties, in particular over the Sahel and the elevated terrains of eastern Africa. While the expected decrease may affect the sizing of the numerous solar projects planned in Africa for the next decades, this study suggests that it does not endanger their viability. At last, this study indicates that the design of such projects also needs to account for the non-negligible uncertainties associated with the resource.
关键词： climate change,solar potential,solar radiation change,solar resource assessment,Bayesian ANOVA method,model projections
更新于2025-09-16 10:30:52
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[IEEE 2019 6th International Conference on Control, Decision and Information Technologies (CoDIT) - Paris, France (2019.4.23-2019.4.26)] 2019 6th International Conference on Control, Decision and Information Technologies (CoDIT) - Tilt Angle Optimization of Photovoltaic Panels
摘要： The solar PV power sector in Spain has been developing at a spectacular rate in recent years. The energy cost and the dependence on fossil fuels can be reduced by improving the efficiency of photovoltaic energy production The performance of a solar radiation conversion system is affected by tilt angle with the horizontal plane. Thus, a photovoltaic array needs to be tilted at the correct angle to maximize its performance. In this paper, we investigate how to determine the optimum tilt angle. This procedure is illustrated for the city of Barcelona (Spain) located at latitude 41o 22' 56'' North and longitude 2o 6'56'' East. The optimal tilt angle varies according the seasons: In Winter (December, January, February) is 56.4, in Spring (March, April, May) is 29.11? in Summer (Jun, July, August) is 13.76? and in Autumn (September, October, November) is 48.14?. Finally, the annual optimum tilt angle for our latitude is 36.87?, with this optimal slope angel, maximum monthly and annual solar radiation is calculated. So, by means of the proposed approach, the energy generation is increased in 10.54% thanks to we are able to benefit from the maximum solar radiation.
关键词： solar PV power,optimum tilt angle,Barcelona,solar radiation,photovoltaic energy production
更新于2025-09-16 10:30:52
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Solar Cells Based on Cu(In, Ga)Se2 Thin-Film Layers
摘要： This paper presents the results of experimental studies of spectral, dark current–voltage and light load characteristics of the selenide–copper–gallium–indium (Cu(In, Ga)Se2) solar cell. Тhe main fundamental parameters of the photoactive semiconductor layer Cu(In, Ga)Se2, such as the band gap, the resistivity of the layer, the equilibrium majority–carrier concentration, the lifetime and the product μ nτn of nonequilibrium minority carriers from the spectral, photoelectric and dark current–voltage characteristics are determined. Based on an analysis of the light-load current–voltage characteristics at various solar radiation powers (50–1000 W/m2), the main parameters of the p–n junction were determined, as well as the nonideality factor and the magnitude of the reverse diode saturation current; a photogeneration mechanism was established in the studied solar radiation range, which had the character of a diffusion mechanism, where carrier recombination in the photoactive layer did not have a significant effect. We found that in conditions of real solar lighting (Рrad = 50–1000 W/m2), the output parameters of the solar cell – short-circuit current, open circuit voltage, the maximum output power increases with Рrad. The fill factor (FF) of the light-current–voltage characteristics has a maximum at Рrad ≈ 200 W/m2, and an efficiency has a maximum value at Рrad ≈ 600 W/m2. The observed dependences of FF and efficiency are explained by the dependence of the series (Rser) and shunt (Rsh) resistance of a solar cell on Prad. To maintain the efficiency of a solar cell based on thin-film layers Cu(In, Ga)Se2, equally high in conditions of increased radiation, as well as in conditions of low solar radiation, it is necessary that Rser decreases and Rsh does not change with Prad.
关键词： photoactive thin film layer,series resistance,solar cell,Cu(In, Ga)Se2,fill factor,short circuit current,solar radiation power,light current–voltage characteristics,efficiency,open circuit voltage,shunt resistance
更新于2025-09-16 10:30:52
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Technical analysis of photovoltaic energy generation for supplying the electricity demand in Brazilian dairy farms
摘要： In many Brazilian dairy farms, the supply of electrical energy does not fully meet the demands of the production systems and/or presents frequent fluctuations and interruptions, making the expansion of production chain unfeasible. These and other barriers have motivating the adoption of renewable and independent energy sources, installed directly in the farms. The present study was conducted to perform a technical analysis of photovoltaic energy generation required for supplying the electricity demand in dairy farms located at Minas Gerais State, Brazil. Daily global radiations on tilted panels were estimated by mathematical models and long-term meteorological database (greater than 33 years). Electrical energy generated by grid-connected photovoltaic systems was predicted considering minimum, average, and maximum daily global radiation conditions. Electrical energy demands were monitored in small (66 cows), medium (106 cows), and large (158 cows) dairy farms. The direct use of electrical energy in operations performed at Brazilian dairy farms were 4, 28, 15, 39, and 15%, on average, for lighting, milking, water heating/pumping, milk cooling/refrigeration, and miscellaneous, respectively. The estimated energy consumptions were 0.96, 0.87, and 0.81 kWh cow?1 day?1 for farms with 66, 106, and 158 cows, respectively. The photovoltaic panel area varied considerably among small, medium, and large dairy farms in order to meet 80% of renewable fraction for the electricity demand.
关键词： Solar radiation models,Photovoltaic panels,Grid-connected photovoltaic system,Energy consumption,Renewable energy,Farm building
更新于2025-09-16 10:30:52
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Radiation Transmission through Glazing
摘要： The transmission, reflection, and absorption of solar radiation by the various parts of a solar collector are important in determining collector performance. The transmittance, reflectance, and absorptance are functions of the incoming radiation, thickness, refractive index, and extinction coefficient of the material. Generally, the refractive index n and the extinction coefficient K of the cover material are functions of the wavelength of the radiation. However, in this chapter, all properties initially will be assumed to be independent of wavelength. This is an excellent assumption for glass, the most common solar collector cover material. Some cover materials have significant optical property variations with wavelength, and spectral dependence of properties is considered in Section 5.7. Incident solar radiation is unpolarized (or only slightly polarized). However, polarization considerations are important as radiation becomes partially polarized as it passes through collector covers.
关键词： absorptance,refractive index,solar radiation,transmittance,extinction coefficient,wavelength,reflectance,collector performance,polarization
更新于2025-09-16 10:30:52
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Concentrating Collectors
摘要： For many applications it is desirable to deliver energy at temperatures higher than those possible with flat-plate collectors. Energy delivery temperatures can be increased by decreasing the area from which heat losses occur. This is done by interposing an optical device between the source of radiation and the energy-absorbing surface. The small absorber will have smaller heat losses compared to a flat-plate collector at the same absorber temperature. In this chapter we discuss two related approaches: the use of nonimaging concentrators and the use of imaging concentrators.
关键词： Solar Radiation,Concentrating Collectors,Nonimaging Concentrators,Energy Delivery,Imaging Concentrators
更新于2025-09-16 10:30:52