scholarly journals Modeling Approach for Determining Equivalent Optical Constants of Plastic Shading Nets under Solar Radiation Conditions

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
A. M. Abdel-Ghany ◽  
I. M. Al-Helal
Keyword(s):  
Solar Radiation ◽  
Optical Constants ◽  
Present Model ◽  
Incident Angle ◽  
Radiative Properties ◽  
Beam Radiation ◽  
Extinction Coefficients ◽  
Average Value ◽  
Texture Structure ◽  
Radiation Conditions

The radiative properties of several plastic shading nets were measured under natural solar radiation conditions. We found that the plastic nets behave as homogeneous translucent materials (e.g., plastic film, plastic sheets, and glass). Based on this behavior, we suggest that it is possible to treat plastic nets as translucent materials and to characterize them with equivalent optical constants (i.e., equivalent refractive indexes,neq, and equivalent extinction coefficients,σeq). Here a physical model to determineneqandσeqof plastic nets was described in analogy to homogeneous translucent materials. We examined three groups of nets based on their color (black, black-green, and beige). Each group consisted of nets with four or five different porosities. Nets of each group had almost the same texture structure. For each group, we derived an equation forneqas a function of the net porosity and determined an average value forσeq. Once values ofneqandσeqwere determined, the solar radiative properties of a net could then be calculated fromneqandσeqfor any incident angle of solar beam radiation without the need of measurements. The present model was validated by comparing the calculated with the measured radiative properties of three nets at different incident angle of solar beam radiation. The calculated radiative properties reasonably agreed with measured values.

scholarly journals Diffusion Characteristics of Solar Beams Radiation Transmitting through Greenhouse Covers in Arid Climates

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 472
Author(s):  
Ibrahim Al-Helal ◽  
Abdullah Alsadon ◽  
Mohamed Shady ◽  
Abdullah Ibrahim ◽  
Ahmed Abdel-Ghany
Keyword(s):  
Solar Radiation ◽  
Diffuse Radiation ◽  
Radiative Properties ◽  
Arid Climate ◽  
Beam Radiation ◽  
Transmitted Beam ◽  
Plastic Films ◽  
Diffusion Characteristics ◽  
Heating Load ◽  
And Diffusion

In hot and sunny regions, extensive solar radiation transmitted into greenhouses makes it essential to select a greenhouse cover with specific characteristics. Reflection and diffusion are the most important properties of covers for reducing solar heating load and scattering solar beams for better growth of plants. Three types of plastic films that are commonly used for covering greenhouses in arid climate were selected for this study. These were reflective-diffusive (RDF), diffusive (DF), and locally produced (CF) films. The films were used to cover three identical twin-span greenhouse models; the radiation components, air temperature (Ti), and relative humidity (RHi) were measured in each model. Transmission of solar radiation through each cover was characterized by determining: (i) The beam that is diffused during transmission, and (ii) the unscattered beam that is transmitted directly through the film. The results show that the diffuse radiation transmitted through the DF, RDF, and CF covers was enhanced, respectively by 77%, 85%, and 109% as a result of diffusing 34%, 33%, and 43% of the transmitted beam radiation by the DF, RDF, and CF covers, respectively during transmission. The diffusive nature of the tested covers increased the ratio of diffuse to direct beam radiation (D/B) from 0.3 outside the greenhouse to 0.77, 0.69, and 0.95 inside a greenhouse covered with DF, RDF, and CF, respectively. At around noon, the CF cover decreased Ti by about 5–10 °C and increased RHi by about 3%–5% compared to those under the DF and RDF covers. However, DF and RDF covers showed almost similar effects in Ti and RHi. The low-price CF cover showed higher diffusive-radiative properties than DF and RDF covers and can serve effectively in arid climate as an alternative covering material.

Implementation of a modified P&O-MPPT algorithm adapted for varying solar radiation conditions

2016 ◽  
Vol 99 (3) ◽  
pp. 839-846 ◽  
Author(s):  
Abdelhakim Belkaid ◽  
Ilhami Colak ◽  
Korhan Kayisli
Keyword(s):  
Solar Radiation ◽  
Radiation Conditions

scholarly journals An empirical correlation of ambient temperature impact on PV module considering natural convection

2020 ◽  
Vol 19 (2) ◽  
pp. 627
Author(s):  
Kamil Jadu Ali ◽  
Ahmed Hasan Mohammad ◽  
Ghanim Thiab Hasan
Keyword(s):  
Natural Convection ◽  
Solar Radiation ◽  
Ambient Temperature ◽  
Analytical Model ◽  
Incident Angle ◽  
Tracking System ◽  
Empirical Correlations ◽  
Pv Module ◽  
Pv Modules ◽  
Temperature Impact

<p><span>In this paper, the effect of the ambient temperature on the PV modules for different angles of inclinations and different intensities of the solar radiation on the surface of the PV module is considered by using empirical correlations for natural convection. An analytical model based on the energy balance equilibrium between the PV module and the environment conditions has been used. Also an expression for calculating the electric power of silicon PV modules in a function of the ambient temperature, the intensity of the solar radiation, the incident angle of the solar radiation to the surface of the PV module and the efficiency of the PV modules at STC conditions have been used. By comparing the obtained both results, it can be seen that the largest deviation between the power values obtained by the analytical model and expression is about (5 %). The results obtained indicates that in the case of a small number of PV modules corresponding to the required number for an average household, it is more economical to invest additional resources in increasing the PV module's surface area than in case of the PV module with sun tracking system. </span></p>

The Negev Radiation Survey

2004 ◽  
Vol 126 (3) ◽  
pp. 906-914 ◽  
Author(s):  
David Faiman ◽  
Daniel Feuermann ◽  
Peter Ibbetson ◽  
Bryan Medwed ◽  
Amos Zemel ◽  
...  
Keyword(s):  
Power Plant ◽  
Solar Radiation ◽  
Site Selection ◽  
Thermal Power Plant ◽  
Meteorological Parameters ◽  
Thermal Power ◽  
Beam Radiation ◽  
Large Variability ◽  
Solar Thermal Power ◽  
Selection For

We present a summary of the principal findings in an ongoing, multiyear, survey of the solar radiation resource and associated meteorological parameters in Israel’s Negev Desert. The summary addresses calibration and monitoring issues, the format in which the annual results are published, availability of the data, and some of the more interesting results observed to date. In particular, we quantify the large variability observed in the direct beam radiation across neighboring sites. The year-to-year variation in this radiation component is also considerable. The variation in the global horizontal radiation is much smaller. Two practical examples are given of uses to which the Negev Radiation Survey has been put: Site selection for a proposed 500 MW solar-thermal power plant; and an estimation of the potential photovoltaic value of rooftops in the major cities.

scholarly journals Remote sensing of cloud droplet radius profiles using solar reflectance from cloud sides – Part 1: Retrieval development and characterization

2019 ◽  
Vol 12 (2) ◽  
pp. 1183-1206 ◽  
Author(s):  
Florian Ewald ◽  
Tobias Zinner ◽  
Tobias Kölling ◽  
Bernhard Mayer
Keyword(s):  
Remote Sensing ◽  
Solar Radiation ◽  
Droplet Size ◽  
Cloud Droplet ◽  
Effective Radius ◽  
Radiative Properties ◽  
Trade Wind ◽  
Small Scale ◽  
Passive Remote Sensing ◽  
Remote Sensing Techniques

Abstract. Convective clouds play an essential role for Earth's climate as well as for regional weather events since they have a large influence on the radiation budget and the water cycle. In particular, cloud albedo and the formation of precipitation are influenced by aerosol particles within clouds. In order to improve the understanding of processes from aerosol activation, from cloud droplet growth to changes in cloud radiative properties, remote sensing techniques become more and more important. While passive retrievals for spaceborne observations have become sophisticated and commonplace for inferring cloud optical thickness and droplet size from cloud tops, profiles of droplet size have remained largely uncharted territory for passive remote sensing. In principle they could be derived from observations of cloud sides, but faced with the small-scale heterogeneity of cloud sides, “classical” passive remote sensing techniques are rendered inappropriate. In this work the feasibility is demonstrated to gain new insights into the vertical evolution of cloud droplet effective radius by using reflected solar radiation from cloud sides. Central aspect of this work on its path to a working cloud side retrieval is the analysis of the impact unknown cloud surface geometry has on effective radius retrievals. This study examines the sensitivity of reflected solar radiation to cloud droplet size, using extensive 3-D radiative transfer calculations on the basis of realistic droplet size resolving cloud simulations. Furthermore, it explores a further technique to resolve ambiguities caused by illumination and cloud geometry by considering the surroundings of each pixel. Based on these findings, a statistical approach is used to provide an effective radius retrieval. This statistical effective radius retrieval is focused on the liquid part of convective water clouds, e.g., cumulus mediocris, cumulus congestus, and trade-wind cumulus, which exhibit well-developed cloud sides. Finally, the developed retrieval is tested using known and unknown cloud side scenes to analyze its performance.

scholarly journals Aerosol-radiation feedback deteriorates the wintertime haze in North China Plain

2019 ◽  
Author(s):  
Jiarui Wu ◽  
Naifang Bei ◽  
Bo Hu ◽  
Suixin Liu ◽  
Meng Zhou ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Air Pollutants ◽  
North China Plain ◽  
North China ◽  
Radiative Properties ◽  
Surface Cooling ◽  
Near Surface ◽  
Incoming Solar Radiation ◽  
Haze Pollution ◽  
Pm2.5 Concentration

Abstract. Atmospheric aerosols or fine particulate matters (PM2.5) scatter or absorb a fraction of the incoming solar radiation to cool or warm the atmosphere, decreasing surface temperature and altering atmospheric stability to further affect the dispersion of air pollutants in the planetary boundary layer (PBL). In the present study, simulations during a persistent and heavy haze pollution episode from 05 December 2015 to 04 January 2016 in the North China Plain (NCP) were performed using the WRF-CHEM model to comprehensively quantify contributions of the aerosol shortwave radiative feedback (ARF) to near-surface PM2.5 mass concentrations. The WRF-CHEM model generally performs well in simulating the temporal variations and spatial distributions of air pollutants concentrations compared to observations at ambient monitoring sites in NCP, and the simulated diurnal variations of aerosol species are also consistent with the measurements in Beijing. Additionally, the model simulates well the aerosol radiative properties, the downward shortwave flux, and the PBL height against observations in NCP during the episode. During the episode, the ARF deteriorates the haze pollution, increasing the near-surface PM2.5 concentration in NCP by 10.2 μg m−3 or with a contribution of 7.8 %. Sensitivity studies have revealed that high loadings of PM2.5 during the episode attenuate the incoming solar radiation down to the surface, cooling the temperature of the low-level atmosphere to suppress development of PBL and decrease the surface wind speed, further enhancing the relative humidity and hindering the PM2.5 dispersion and consequently exacerbating the haze pollution in NCP. The ensemble analysis indicates that when the near-surface PM2.5 mass concentration increases from around 50 to several hundred μg m−3, the ARF contributes to the near-surface PM2.5 by more than 20 % during daytime in NCP, substantially aggravating the heavy haze formation. However, when the near-surface PM2.5 concentration is less than around 50 μg m−3, the ARF generally reduces the near-surface PM2.5 concentration due to the consequent perturbation of atmospheric dynamic fields.

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