Analytical Methods to Evaluate Flux Distributions From Point-Focus Collectors for Solar Furnace and Dish Engine Applications

2010 ◽  
Author(s):  
Clifford K. Ho ◽  
Siri S. Khalsa ◽  
Nathan P. Siegel
Keyword(s):  
Analytical Methods ◽  
Maximum Concentration ◽  
Concentration Ratio ◽  
Flux Distribution ◽  
Focal Length ◽  
Solar Furnace ◽  
Analytical Function

This paper introduces a new analytical “stretch” function that accurately predicts the flux distribution from on-axis point-focus collectors. Different dish sizes and slope errors can be assessed using this analytical function with a ratio of the focal length to collector diameter fixed at 0.6 to yield the maximum concentration ratio. Results are compared to data, and the stretch function is shown to provide more accurate flux distributions than other analytical methods employing cone optics.

Sunshape and Its Influence on the Flux Distribution in Imaging Solar Concentrators

1992 ◽  
Vol 114 (4) ◽  
pp. 260-266 ◽  
Author(s):  
M. Schubnell
Keyword(s):  
Concentration Ratio ◽  
Flux Distribution ◽  
Measurement Techniques ◽  
Solar Limb ◽  
Solar Furnace ◽  
Optical Systems ◽  
Solar Concentrators ◽  
Parabolic Dish ◽  
The Mean ◽  
Mean Concentration

Imaging solar concentrators, such as a parabolic dish, image the sun to their focal plane. Thus, the flux distribution is basically an image of the angular distribution of the direct incident solar radiation. This distribution, referred to as sunshape, is determined by solar limb darkening and by small angle scattering in the atmosphere. In this paper we present measurements of the sunshape and investigate its influence on the flux distribution in the solar furnace at Paul Scherrer Institute (PSI) and in parabolic concentrators, both experimentally and by a ray tracing procedure. Analyzing the influence of the spectral dependence of the sunshape we find that the characteristic width of the focal spot increases with longer wavelengths. In contrary, the mean concentration ratio is higher at shorter wavelengths. Although these effects are rather small, they can be important in radiometric measurement techniques to determine the emissivity and the temperature distribution of an irradiated sample as well as in designing solar pumped lasers. Comparing various sunshapes with the corresponding flux distributions in the two-stage solar furnace at PSI, we show that the influence of the circumsolar radiation on the flux distribution is usually negligible as compared to the distortion due to astigmatism. However, in more accurate optical systems, such as highly concentrating parabolic dishes, the flux distribution is a fairly accurate image of the sunshape. We find, that due to sunshape, the mean concentration ratio in a parabolic dish is decreased by about ten percent. As an example we subsequently estimate the mean annual conversion efficiency of an ideal solar converter operated in the Swiss mountains.

Optimal Scheduling of Parabolic Heliostats Aim Targets in a Mini-Tower Solar Concentrator System

2011 ◽  
Author(s):  
Karim Hamza ◽  
Umesh Gandhi ◽  
Kazuhiro Saitou
Keyword(s):  
High Temperature ◽  
Concentration Ratio ◽  
Flux Distribution ◽  
Incidence Angle ◽  
Focal Length ◽  
Low Cost ◽  
Small Scale ◽  
Solar Concentrator ◽  
Design Variables ◽  
Utility Scale

Solar tower with heliostat mirrors is an established technology for utility-scale solar energy harvesting. The setup has several advantages such as the capability to reach high temperature, modularity and ease of maintenance of the heliostats, containment of the high temperature zone, as well as overall low cost per harvested energy. Downscaling to medium and small scale applications is a desirable goal in order to attract more users of the technology. However, the downscaling often does not turn out economically feasible while using flat mirror heliostats, which are the norm in utility-scale systems. This is mainly due to the need to preserve the number (typically several hundred) of mirrors in order to maintain the solar concentration ratio. Use of parabolic mirrors instead can significantly reduce the required number of mirrors for smaller scale systems, but comes with new challenges. Unlike flat mirrors, the effective focal length of parabolic mirrors changes with the incidence angle causing undesirable variations in the concentration ratio and/or flux distribution at the receiver. To overcome this issue, we propose adjustment of the aim targets of the heliostat mirrors. Instead of aiming at the center of the receiver, aim targets are set as design variables and optimized to reduce undesirable peaks in the flux distribution. A special implementation of genetic algorithm is developed and applied to a case study of a nominal 10kW solar concentrator. Results of the study show significant improvement in flux distribution.

DIMENSIONING OF ORTHOTROPICALLY STIFFENED CFRP SHELLS OF LARGE LAUNCH VEHICLES FOR LOAD INTRODUCTION AND STABILITY

2010 ◽  
Vol 10 (04) ◽  
pp. 601-621 ◽  
Author(s):  
ANDREAS RITTWEGER ◽  
SUSANNE CHRISTIANSON ◽  
HUBA ÖRY
Keyword(s):  
Analytical Methods ◽  
Flux Distribution ◽  
Fe Analysis ◽  
Launch Vehicles ◽  
Local Instability ◽  
Axial Loads ◽  
Ring Frame ◽  
Final Design ◽  
Shell Equations ◽  
Analytical Approaches

The dimensioning of an orthotropically stiffened cylindrical CFRP shell subjected to the introduction of concentrated axial loads using rapid analytical methods is presented. For stress calculation the shell equations are simplified by applying the semibending theory and integrated by employing the transfer matrix method. Analytical approaches are used for stability verification. The dimensioning considers required constraints in the force flux distribution, strength of the laminate, general instability, panel instability (from ring frame to ring frame) and local instability. The rapid analytical methods allow mass optimization. The final design is confirmed by detailed FE analysis. A comparison of the FE analysis with the analytical results is shown.

scholarly journals Monte Carlo Ray-Tracing Simulation of a Cassegrain Solar Concentrator Module for CPV

2021 ◽  
Vol 9 ◽  
Author(s):  
Seung Jin Oh ◽  
Hyungchan Kim ◽  
Youngsun Hong
Keyword(s):  
Monte Carlo ◽  
Ray Tracing ◽  
Concentration Ratio ◽  
Collection Efficiency ◽  
Focal Length ◽  
Tracking Error ◽  
Target Area ◽  
Solar Concentrator ◽  
Acceptance Angle ◽  
Energy Applications

The concentration ratio is one of the most important characteristics in designing a Cassegrain solar concentrator since it directly affects the performance of high-density solar energy applications such as concentrated photovoltaics (CPVs). In this study, solar concentrator modules that have different configurations were proposed and their performances were compared by means of a Monte Carlo ray-tracing algorithm to identify the optimal configurations. The first solar concentrator design includes a primary parabolic concentrator, a parabolic secondary reflector, and a homogenizer. The second design, on the other hand, includes a parabolic primary concentrator, a secondary hyperbolic concentrator, and a homogenizer. Two different reflectance were applied to find the ideal concentration ratio and the actual concentration ratio. In addition, uniform rays and solar rays also were compared to estimate their efficiency. Results revealed that both modules show identical concentration ratios of 610 when the tracking error is not considered. However, the concentration ratio of the first design rapidly drops when the sun tracking error overshoots even 0.1°, whereas the concentration ratio of the second design remained constant within the range of the 0.8° tracking error. It was concluded that a paraboloidal reflector is not appropriate for the second mirror in a Cassegrain concentrator due to its low acceptance angle. The maximum collection efficiency was achieved when the f-number is smaller and the rim angle is bigger and when the secondary reflector is in a hyperboloid shape. The target area has to be rather bigger with a shorter focal length for the secondary reflector to obtain a wider acceptance angle.

The SCATMES Device for Measurement of Concentrated Solar Radiation

1999 ◽  
Vol 121 (2) ◽  
pp. 116-120 ◽  
Author(s):  
A. Neumann ◽  
A. Schmitz
Keyword(s):  
Solar Radiation ◽  
Measurement System ◽  
Flux Distribution ◽  
Optical Design ◽  
Video Camera ◽  
Solar Furnace ◽  
Camera Systems ◽  
Measurement Principle ◽  
Concentrated Solar Radiation ◽  
Compact Geometry

Video camera systems monitoring a diffuse reflecting target for measuring the flux distribution of concentrated solar radiation are quite common. This technique cannot be used if parts of the experimental setup screen the surface of the target. The development of a new measurement system with a compact geometry and a new optical design is described. With this system it is possible to measure the flux distribution behind parts of an experiment and at any position of the plane of measurement, without any alteration of the setup. The sources of error, especially those of the target and the camera, are described and discussed, and finally a comparison to the existing FATMES-System, which has been performed at the solar furnace of the DLR in Cologne, is presented. Due to its measurement principle the new system is called ’Scanning Camera and Target Measurement System‘ (acronym: SCATMES).

scholarly journals Study on Concentrating Characteristics of a Solar Parabolic Dish Concentrator within High Radiation Flux

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Qianjun Mao ◽  
Liya Zhang ◽  
Hongjun Wu
Keyword(s):  
Focal Plane ◽  
Flux Distribution ◽  
Radiation Flux ◽  
Focal Length ◽  
Thermal Conversion ◽  
High Radiation ◽  
Equal Area ◽  
Future Design ◽  
Parabolic Dish ◽  
Parabolic Dish Concentrator

Concentrating characteristics of the sunlight have an important effect on the optical-thermal conversion efficiency of solar concentrator and the application of the receiver. In this paper, radiation flux in the focal plane and the receiver with three focal lengths has been investigated based on Monte Carlo ray-tracing method. At the same time, based on the equal area-height and equal area-diameter methods to design four different shape receivers and numerical simulation of radiation flux distribution characteristics have also been investigated. The results show that the radiation flux in the focal plane increases with decreasing of the focal length and the diameter of the light spot increases with increasing of the focal length. The function of the position with a maximum of radiation flux has been obtained according to the numerical results. The results also show that the radiation flux distribution of cylindrical receiver has the best performance in all four receivers. The results can provide a reference for future design and application of concentrating solar power.

A New Design of a (3D) Fresnel Collector With Fixed Mirrors and Tracking Absorber

2000 ◽  
Vol 122 (2) ◽  
pp. 63-68 ◽  
Author(s):  
A. B. Larbi
Keyword(s):  
Concentration Ratio ◽  
Focal Length ◽  
Computer Code ◽  
Design Parameters ◽  
Medium Temperature ◽  
Maintenance Costs ◽  
Energy Delivery ◽  
Half Angle ◽  
Optical Behavior ◽  
Fixed Mirrors

In this paper we developed model of a (3D) Fresnel collector with fixed mirrors and tracking absorber which approximates the optical behavior of a fixed spherical collector (hemispherical bowl). The aim of the study is to investigate the possibility of using this type of installation for applications in medium temperature processes (200—300°C). Via a computer simulation which includes ray-tracing, we evaluate the sensitivity of the geometric concentration ratio to: concentrator design parameters and the option of using curved versus flat elementary mirrors. The developed computer code permits the optimization of the concentrator reflecting area, the focal length (or rim half-angle), and the dimensions and number of reflecting elementary mirrors. The (3D) Fresnel collectors can be a practical alternative to spherical collectors (hemispherical bowl). Capital and maintenance costs can be significantly lower than for spherical collectors, but with reduced energy delivery. [S0199-6231(00)00302-6]

Flux Density Distribution in the Focal Region of a Solar Concentrator System

1991 ◽  
Vol 113 (2) ◽  
pp. 112-116 ◽  
Author(s):  
M. Schubnell ◽  
J. Keller ◽  
A. Imhof
Keyword(s):  
Density Distribution ◽  
Flux Density ◽  
Ray Tracing ◽  
Radiation Flux ◽  
Focal Length ◽  
Solar Furnace ◽  
Focal Region ◽  
The Sun ◽  
Parabolic Dish ◽  
Flux Density Distribution

In high temperature solar energy applications highly concentrating optical systems, such as, e.g., parabolic dishes, achieve typical radiation flux densities >2 MW/m2. In order to investigate thermo and photochemical reactions at temperatures >1500 K and radiation flux densities >2 MW/m2 a solar furnace was built at Paul Scherrer Institute (PSI). This furnace is a two-stage concentrator. The first stage is a prefocusing glass heliostat with a focal length of 100 m. The second stage is a highly concentrating parabolic dish with a focal length of 1.93 m. To design experiments to be carried out in the focal region of the parabolic dish, the radiation flux as well as its density distribution have to be known. This distribution is usually measured by radiometric methods. However, these methods are generally rather troublesome because of the high temperatures involved. In this paper we present a simple method to estimate the characteristic features of the radiation flux density distribution in the focal region of a concentrator system. It is well known from solar eclipses that the mean angular diameter of the moon is almost equal to that of the sun (9.1 mrad versus 9.3 mrad). Hence, the lunar disk is well suited to be used as a light source to investigate the flux distribution in a solar furnace. Compared to the sun the flux density is reduced by 4·105 and the flux density distribution can be inspected on a sheet of paper located in the plane of interest, e.g., the focal plane. This distribution was photographed and analyzed by means of an image processing system. The density distribution was also simulated using a Monte Carlo ray tracing program. Based on this comparison, and on further ray tracing computations, we show that the peak flux density decreases from 8.9 MW/m2 in December to values below 4 MW/m2 in June and the net radiation flux from 25 kW to 15 kW, respectively.

Design of Fresnel Lens With Constant Height Spherical Facets

2020 ◽  
Author(s):  
Kuldeep Awasthi ◽  
Desireddy Shashidhar Reddy ◽  
Mohd. Kaleem Khan
Keyword(s):  
Ray Tracing ◽  
Concentration Ratio ◽  
Focal Length ◽  
Constant Width ◽  
Fresnel Lens ◽  
Aperture Diameter ◽  
Constant Height ◽  
Proposed Model ◽  
Fresnel Lenses ◽  
Ray Tracing Model

Abstract In the present work, a ray tracing model based on Snell’s law of refraction is developed using MATLAB for the design of Fresnel lens with spherical facets of equal height. In practice, the facet curvature is approximated by straight line, which causes an increase in spherical aberrations and reduction in concentration ratio. The proposed model takes facet curvature into consideration, which will result in effective utilization of incident solar radiations. Fresnel lenses are available with facets having constant width and facets with constant height. A comparison of spherical aberrations in the two cases has also been presented using different f - numbers (ratio of focal length to aperture diameter). Effect of different parameters like number of facets and refractive index of lens material on concentration ratio is also presented in present study. The proposed ray tracing model is validated with the model developed in SolTrace, an open access software. The predictions from the proposed model are in good agreement with the results of SolTrace model with an average deviations of 6.8% for concentration ratio and 2.2% for focal length.

Flux distribution of solar furnace using non-imaging focusing heliostat

Solar Energy ◽  
2009 ◽  
Vol 83 (8) ◽  
pp. 1200-1210 ◽  
Author(s):  
Chern Sing Lim ◽  
Li Li
Keyword(s):  
Flux Distribution ◽  
Solar Furnace
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