scholarly journals Computer Modelling of the Optical Behavior of Homogenizers in High-Flux Solar Furnaces

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1828 ◽  
Author(s):  
José Carlos Garcia Pereira ◽  
Kaveh Rahmani ◽  
Luís Guerra Rosa
Keyword(s):  
Solar Radiation ◽  
Computer Modelling ◽  
Light Flux ◽  
Optical Devices ◽  
High Flux ◽  
Radiation Distribution ◽  
Optical Output ◽  
Reflecting Surfaces ◽  
Optical Behavior ◽  
Optical Ray Tracing

Solar radiation homogenizers are multi-mirror devices that try to reshape the solar radiation distribution coming from a concentrator, so that, after passing through the homogenizer, the light flux becomes as much evenly distributed as possible. The optical behavior of these multi-reflective devices is complex and still ill-understood. The geometry of the concentrator defines the features of the concentrated flux and then the characteristics of a particular homogenizer must be chosen according to the envisaged use. In this work, we developed and used optical ray-tracing software to investigate how the homogenizer’s optical output is affected by the following homogenizer’s characteristics: (i) Number of reflecting surfaces; (ii) total length; (iii) position (relative to focal plane); and (iv) tilt angle (inclination) of reflecting surfaces. The obtained results provide valuable information for the use of these optical devices and may contribute to the development of more efficient strategies for homogenization of concentrated radiation generated by high-flux solar furnaces.

scholarly journals Simulation and experimental validation of solar radiation distribution on the absorber of a line-axis asymmetric compound parabolic concentrator

Solar Energy ◽  
2020 ◽  
Vol 198 ◽  
pp. 36-52 ◽  
Author(s):  
Ronald Muhumuza ◽  
Aggelos Zacharopoulos ◽  
Jayanta Deb Mondol ◽  
Mervyn Smyth ◽  
Adrian Pugsley ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Experimental Validation ◽  
Compound Parabolic Concentrator ◽  
Radiation Distribution

scholarly journals Semiparametric Semivariogram Modeling with a Scaling Criterion for Node Spacing: A Case Study of Solar Radiation Distribution in Thailand

Mathematics ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 2173
Author(s):  
Sompop Moonchai ◽  
Nawinda Chutsagulprom
Keyword(s):  
Solar Radiation ◽  
Monotonicity Condition ◽  
Ungauged Sites ◽  
Spurious Oscillation ◽  
Geostatistical Interpolation ◽  
Radiation Distribution ◽  
Parametric Functions ◽  
Close Form ◽  
Kriging Approach

Geostatistical interpolation methods, sometimes referred to as kriging, have been proven effective and efficient for the estimation of target quantity at ungauged sites. The merit of the kriging approach relies heavily on the semivariograms in which the parametric functions are prevalently used. In this work, we explore the semiparametric semivariogram where no close-form semivariogram is required. By additionally enforcing the monotonicity condition in order to suppress the presence of spurious oscillation, a scaling of the nodes of the semiparametric kriging is proposed. To this end, the solar radiation estimates across extensive but unmeasured regions in Thailand using three different semivariogram models are undertaken. A cross validation analysis is carried out in order to justify the performance of each approach. The best results are achieved by the semiparametric model with an improvement of around 7–13% compared to those obtained from the parametric semivariograms.

Ellipsometric Determination of the Spectra of Adsorbed Molecules

1971 ◽  
Vol 49 (7) ◽  
pp. 1115-1132 ◽  
Author(s):  
M. J. Dignam ◽  
B. Rao ◽  
M. Moskovits ◽  
R. W. Stobie
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Optical Constants ◽  
Order Term ◽  
Second Order ◽  
Lower Sensitivity ◽  
Model Calculations ◽  
The Media ◽  
Reflecting Surfaces ◽  
Optical Behavior

This paper presents a detailed analysis of the application of ellipsometry to obtaining the optical spectra (principally infrared (i.r.)) of molecules adsorbed on reflecting surfaces. Both external and total internal reflections are considered and the conditions for optimum sensitivity examined. A new empirical quantity, the relative complex optical density, is defined which exhibits thin film properties well, particularly in the case of multiple reflection measurements. An explicit expression is derived for this density function (relating it to the optical constants of the media and other system parameters), which is both reasonably simple and correct to second order terms in the film thickness. It is shown that for thin films, no higher order terms need be included, but that in general the second order term must be retained. Various limiting cases are examined to gain insight into the optical behavior of thin films, and to the same end, model calculations performed for CCl4 physically adsorbed on Ag, Ni, Sb, and Ge. In relation to conventional reflection spectroscopy, ellipsometric spectroscopy is shown to have three major advantages: (1) in general, higher sensitivity to adsorbate properties; (2) very much lower sensitivity to absorption of radiation by the adjacent gas phase; (3) more information, permitting the optical constants and film thickness to be determined. Finally, the practicability of the technique is demonstrated by presenting preliminary results for CH3OH reversibly adsorbed on Ag, showing clearly the C—H stretching bands.

View Factors of Flat Solar Collectors Array in Flat, Inclined, and Step-Like Solar Fields

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Nassar Yasser Fathi ◽  
Alsadi Samer
Keyword(s):  
Solar Radiation ◽  
Diffuse Radiation ◽  
Dynamic Parameter ◽  
Incident Radiation ◽  
Appreciable Amount ◽  
Design Parameters ◽  
View Factor ◽  
Solar Radiation Incident ◽  
View Factors ◽  
Reflecting Surfaces

Solar radiation consists of direct beam, sky diffuse, and reflected radiations from the ground and adjacent surfaces. The amount of diffuse radiation falling on solar collector depends on the view factor of the collector to sky. The reflected radiation striking the collector's surface depends on the reflectivity of the surface, as well as on view factors and the amount of solar radiation reaching the reflecting surfaces. The amount of reflected radiation coming from the ground can be of an appreciable amount, and can be amplified using special reflector surfaces. This study develops general analytical expressions for the sky's view factors as well as factors related to the ground and those between collectors for the deployment of collectors in multiple rows, in three types of solar fields: flat, inclined, and steplike solar fields. All parameters presented in these expressions are measurable (edge-to-edge dimension). The effects of the design parameters such as the tilt of the angle of the collector, the distance between the collectors, the height of the collector, the position of the collector above the ground (as in the case of step-like field), and the inclination of the land of the field (as in the case of an inclined field) on the view factors are numerically demonstrated. The current study also specifies new terms such as the sunny zone and the shadow zone; these zones control the amount of solar radiation reflected onto the collector. As a result, the ground-view factor that depends on the altitude of the solar angle is considered to be a dynamic parameter. The results obtained may be used to estimate the solar radiation incident on all types of solar fields, with the possibility of increasing the incident radiation on a collector by using planar reflectors.

The Use of Virtual Reflectors to Improve Speech Intelligibility in Open Stage Auditoria

1998 ◽  
Vol 5 (1) ◽  
pp. 57-68 ◽  
Author(s):  
L. El-Zeky ◽  
D.J. Oldham
Keyword(s):  
Speech Intelligibility ◽  
Potential Problem ◽  
Computer Modelling ◽  
Conventional Technique ◽  
Energy Fraction ◽  
Human Speech ◽  
Suitable Parameter ◽  
Transmission Index ◽  
Speech Transmission ◽  
Reflecting Surfaces

A potential problem encountered with open stage auditoria is poor speech intelligibility arising from the directional nature of human speech sources. The conventional technique of employing large overhead reflecting surfaces to ensure a large early energy fraction to improve intelligibility is shown to be unsuitable in this situation. The use of Virtual Reflectors consisting of microphones and loudspeakers symmetrically located relative to the stage is proposed as a possible solution to the problems of open stage auditoria. It is suggested that the Speech Transmission Index is a suitable parameter for assessing the performance of Virtual Reflectors when in use and that computer modelling could provide a suitable method for investigating the action of Virtual Reflectors.

Modelling of real solar radiation spatial distribution as a tool for solar energy cadastre in the cities

2017 ◽  
Vol 29 (2) ◽  
pp. 204-215 ◽  
Author(s):  
Małgorzata Pietras-Szewczyk ◽  
Leszek Szewczyk
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Cloud Cover ◽  
Significant Variable ◽  
State Security ◽  
Radiation Distribution ◽  
Linke Turbidity Factor ◽  
Gis Software ◽  
The City

The increasing needs of energy and decreasing traditional energy sources are becoming one of the biggest issues of our civilization. The provision of stable energy supply is a matter of state security. The energy consumption keeps growing especially in big cities. Therefore, it became reasonable to produce energy directly in cities. To optimize the use of the solar energy in the city areas, a fundamental issue is to find and estimate the amount of solar radiations at a specified location by using available tools and data. The main goal of this work is to demonstrate the potential of the r.sun model, a component of GRASS software, in calculating real solar radiation for the selected location. The work starts with demonstrating the effect of cloud cover for the amount of solar radiation reaching the Earth’s surface and the usage of GIS software and Ogimet website in the spatial analysis of real solar radiation distribution. For this purpose, data concerning cloud cover for selected locations were analysed. The study is based on the synoptic data obtained from Ogimet. Average daily cloud cover totals and long-term values were calculated. Apart from the cloud cover data, a significant variable, the Linke turbidity factor, describing the weakening of solar radiation due to the presence of aerosols and water vapour in the atmosphere, was taken into consideration. The obtained results were used to develop a map of real solar radiation distribution for a part of Wrocław. The results obtained by that model with the acquired data by the local meteorological station show compatibility.

Solar Radiation Distribution Method for a Photovoltaic Greenhouse based on the Maximization of Annual Economic Benefits

2021 ◽  
Author(s):  
Yi Wang ◽  
Tiejun Zhou ◽  
Weiji Zhou
Keyword(s):  
Mathematical Model ◽  
Power Generation ◽  
Solar Radiation ◽  
Agricultural Production ◽  
Crop Production ◽  
Economic Benefits ◽  
Distribution Method ◽  
Greenhouse Crops ◽  
Photovoltaic Power ◽  
Radiation Distribution

Abstract A solar radiation distribution method is proposed based on the maximization of economic benefits for photovoltaic power generation and agricultural production in a photovoltaic greenhouse to solve the problem of low overall economic benefits because of an unreasonable solar radiation distribution between photovoltaic power generation and agricultural production in the photovoltaic greenhouse. First, a mathematical model of the solar radiation yield of photovoltaic greenhouse crops is proposed based on a rectangular hyperbolic modified light response model of crops to represent the relationship between solar radiation energy and crop production. Second, a mathematical model of the average annual revenue of a photovoltaic greenhouse is established to determine the maximum annual economic benefit of the photovoltaic greenhouse, and the model is constrained by the requirements of the light intensity of photovoltaic power generation and environmental conditions for the growth of greenhouse crops. Finally, the correctness of the model is verified by actual operation data of a photovoltaic greenhouse in Xinjiang, and the optimal solar radiation distribution proportion is calculated. This study provides theoretical support for the design of photovoltaic greenhouses.

SOLAR RADIATION DISTRIBUTION IN A TUNNEL GREENHOUSE

2008 ◽  
pp. 855-862 ◽  
Author(s):  
C. Baxevanou ◽  
T. Bartzanas ◽  
D. Fidaros ◽  
C. Kittas
Keyword(s):  
Solar Radiation ◽  
Radiation Distribution
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