scholarly journals Flux profile at focal area of concentrating solar dishes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Ebrahim Foulaadvand ◽  
Amir Aghamohammadi ◽  
Parvin Karimi ◽  
Hadi Borzouei
Keyword(s):  
Concentration Ratio ◽  
Flux Distribution ◽  
Optical Axis ◽  
Radial Dependence ◽  
Energy Harvest ◽  
Spherical Mirror ◽  
Line Region ◽  
Solar Radiation Flux ◽  
Flux Profile ◽  
Spherical Mirrors

AbstractWe analytically, experimentally and computationally explore the solar radiation flux distribution in the interior region of a spherical mirror and compare it to that of a paraboloidal one with the same aperture area. Our investigation has been performed in the framework of geometrical optics. It is shown that despite one can assign a quasi focus, at half the radius, to a spherical mirror, the light concentration occurs as well on an extended line region which starts at half-radius on the optical axis. In contrast to a paraboloidal concentrator, a spherical mirror can concentrate the radiation parallel to its optical axis both in a point-focus and in a line-focus manner. The envelope of the reflected rays is also obtained. It is shown that the flux distribution has an axial symmetry. The radial dependence of the flux on a flat circular receiver is obtained. The flux longitudinal dependence is shown to exhibit three distinctive regions in the interval [0, R] (R is mirror radius). We obtain the radiational (optical) concentration ratio characteristics and find the optimal location of the flat receiver of a given size at which the concentration ratio is maximised. In contrast to a parabolic mirror, it is shown that this location depends on the receiver size. Our findings offers that in spherical mirrors one can alternatively use a line receiver and gains a considerable thermal energy harvest. Our results are supported by Monte Carlo ray tracing performed by Zemax optical software. Experimental validation has been performed in lab with a silver-coated lens as the spherical mirror.

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.

scholarly journals An Autocollimation Circle Reading System for the Infrared Meridian Instrument

1995 ◽  
Vol 166 ◽  
pp. 361-361
Author(s):  
V.N. Yershov ◽  
A.A. Nemiro
Keyword(s):  
Optical Axis ◽  
Angular Position ◽  
Optical Center ◽  
Meridian Circle ◽  
Primary Mirror ◽  
Axis Position ◽  
Spherical Mirrors ◽  
Reading System ◽  
Zero Points ◽  
New System

A new autocollimation circle reading system is proposed for the reflector meridian circle (Nemiro and Streletsky, 1988). The instrument will be used for observations in the K-infrared waveband. Instead of the divided circle fixed to the instrument tube the new system has small spherical mirrors polished at the lateral surfaces of the primary mirror. The primary mirror is made from sitall and has an autocollimation system aimed at monitoring its optical axis position. The small spherical mirrors of the circle reading system link the circle readings with the primary's optical axis. The divided circles are fixed unmovable opposite to both lateral surfaces of the primary's optical block. Both surfaces have four spherical mirrors. The distance between the divided circles and the mirrors is equal to the mirrors' radii of curvature. The scales of each circle are illuminated from outside (where the measuring microscopes are placed). The mirrors form autocollimated images of the divisions at the plane of the divisions itself. Averaged coordinates of a division and its autocollimated image give the position of the mirror's optical center, and the semi-difference of the coordinates gives the angular position of the telescope. So, the measurements of the circle positions are differential ones, and any displacements of the microscope zero-points are not critical. The precision of measurements is estimated to be better then 0.05″ (random) and 0.005″ (systematical). The work was supported by the Russian Foundation of Fundamental Investigations (the project's code is 93-02-17095).

scholarly journals Experimental Study of Heat Flux Distribution of Arc Driven by AC Magnetic Field

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Naomi Matsumoto ◽  
Takeo Yamamoto ◽  
Masaya Sugimoto ◽  
Koichi Takeda
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Magnetic Fields ◽  
Flux Distribution ◽  
Field Experiments ◽  
Theoretical Calculations ◽  
Magnetic Flux Density ◽  
Heat Flux Distribution ◽  
Ac Magnetic Field ◽  
Flux Profile

The authors earlier developed a model to predict the heat flux distribution in an arc driven by an AC magnetic field. That theoretical model implied that the heat flux distribution depended on waveforms of the imposed AC magnetic field. Experiments were conducted in this study to validate that theoretical prediction. Theoretical calculations of heat flux distribution in the arc driven by AC magnetic field were conducted using the heat flux profile in the arc root obtained from the measurement under no magnetic field. The heat flux distributions in arcs driven by AC magnetic fields were measured by imposing two AC magnetic fields with sinusoidal and rectangular waveforms. Agreement between experimental and theoretical heat flux distributions was good. Results confirm that heat flux profiles of various types are producible by controlling the imposed magnetic flux density and its waveform.

scholarly journals Alignment Strategy Optimization Method for Dish Stirling Faceted Concentrators

2007 ◽  
Author(s):  
Charles E. Andraka
Keyword(s):  
Flux Distribution ◽  
Single Point ◽  
Optimization Method ◽  
Spot Size ◽  
Geometric Constraints ◽  
Novel Approach ◽  
Peak Flux ◽  
Flux Profile ◽  
Receiver Plane ◽  
Alignment Strategy

A Dish Stirling parabolic concentrator typically consists of a number of mirror facets that must be aligned to focus the concentrated sunlight on the engine receiver. An alignment strategy must be developed to deliver the energy uniformly to the receiver while maximizing system performance. Several criteria must be met in order to maximize the performance and lifetime of the system. The peak flux should be minimized at the receiver to extend life. This is accomplished by locally optimizing the mirror aimpoints, minimizing overlap of facet images. The energy delivered to each cylinder of a multi-cylinder engine should be balanced to maximize the power production capability of the engine. This is accomplished through globally optimizing the mirror aimpoints. Depending on dish geometry, both of these constraints will be met by moving the aimpoints of certain facets away from a single point at the center of the aperture. However, this often results in a larger aperture or more flux spillage. The larger aperture results in greater thermal and reflective losses from the receiver cavity. This paper proposes and demonstrates a novel approach to optimizing the alignment strategy while obeying these constraints. The method uses an approach similar to molecular dynamics to globally and locally distribute the power on the receiver, while imposing movement constraints at the aperture to limit the focal plane spot size. The method can also impose additional geometric constraints at the receiver plane to accommodate un-cooled surfaces. The method is explored and demonstrated on the Stirling Energy Systems 25kW dish Stirling system at Sandia National Laboratories. The approach provides a receiver flux distribution and power balance equal to the strategy developed by McDonnell Douglas in the early 1980’s, but with an aperture size equal to that of the single aimpoint strategy. This should result in about a 1kW increase in power generated at rated conditions, with no additional cost, due to reduced thermal losses from the receiver. The method can be extended to other point-focus concentrating solar technologies. On a tower, the heliostat aiming strategy could be dynamically updated to accommodate flux profile needs, sun position, or maintenance in the field.

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.

scholarly journals Research on Measurement Accuracy of Laser Tracking System Based on Spherical Mirror with Rotation Errors of Gimbal Mount Axes

2018 ◽  
Vol 18 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Zhaoyao Shi ◽  
Huixu Song ◽  
Hongfang Chen ◽  
Yanqiang Sun
Keyword(s):  
Measurement Error ◽  
Measurement Accuracy ◽  
Optical Axis ◽  
Tracking System ◽  
Vertical Direction ◽  
Laser Ranging ◽  
Spherical Mirror ◽  
Laser Tracking ◽  
Radial Error ◽  
Error Motion

Abstract This paper presents a novel experimental approach for confirming that spherical mirror of a laser tracking system can reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy. By simplifying the optical system model of laser tracking system based on spherical mirror, we can easily extract the laser ranging measurement error caused by rotation errors of gimbal mount axes with the positions of spherical mirror, biconvex lens, cat’s eye reflector, and measuring beam. The motions of polarization beam splitter and biconvex lens along the optical axis and vertical direction of optical axis are driven by error motions of gimbal mount axes. In order to simplify the experimental process, the motion of biconvex lens is substituted by the motion of spherical mirror according to the principle of relative motion. The laser ranging measurement error caused by the rotation errors of gimbal mount axes could be recorded in the readings of laser interferometer. The experimental results showed that the laser ranging measurement error caused by rotation errors was less than 0.1 μm if radial error motion and axial error motion were within ±10 μm. The experimental method simplified the experimental procedure and the spherical mirror could reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy of the laser tracking system.

Slope Measurements of Parabolic Dish Concentrators Using Color-Coded Targets

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Steffen Ulmer ◽  
Peter Heller ◽  
Wolfgang Reinalter
Keyword(s):  
Flux Distribution ◽  
Optical Axis ◽  
Digital Camera ◽  
Accurate Method ◽  
Observation Point ◽  
Color Target ◽  
Image Analysis Algorithm ◽  
Design Values ◽  
Parabolic Dish ◽  
Normal Vectors

A new fast and highly accurate method for measuring the slope errors of parabolic dish concentrators has been developed. This method uses a flat target with colored stripes placed close to the focal plane of the concentrator and a digital camera located at an observation point on the optical axis at some distance from it. A specially developed image analysis algorithm detects the different colors of the images of the reflection of the target in the concentrator and assigns them their known position on the color target. This information, along with the geometry of the measurement setup and the theoretical parabolic shape of the concentrator, is used to calculate the normal vectors of the concentrator surface. From these normal vectors, the radial and tangential slopes can be calculated and compared to the design values of the concentrator. The resulting slope errors not only give the total concentrator error for general characterization of the dish but also indicate systematic errors from fabrication and installation with a high spatial resolution. In order to verify the quality of the results obtained, a ray-tracing code was developed that calculates the flux distribution on planes perpendicular to the optical axis. Measured slope errors of a 8.5m dish concentrator are presented and the calculated flux distributions are compared to measured flux distributions. The comparison shows excellent agreement in the flux distribution on the absorber plane. This verifies the promising potential of this fast and highly precise new method for measuring imperfections in dish concentrator shape.

scholarly journals DESIGN OF IRRADIATION FACILITIES AT CENTRAL IRRADIATION POSITION OF PLATE TYPE RESEARCH REACTOR BANDUNG

2020 ◽  
Vol 22 (1) ◽  
pp. 1
Author(s):  
Epung Saepul Bahrum ◽  
Wawan Handiaga ◽  
Yudi Setiadi ◽  
Henky Wibowo ◽  
Prasetyo Basuki ◽  
...  
Keyword(s):  
Neutron Flux ◽  
Thermal Neutron ◽  
Flux Distribution ◽  
Thermal Neutron Flux ◽  
Research Reactor ◽  
Reactor Core ◽  
Irradiation Position ◽  
Neutron Flux Distribution ◽  
Flux Profile ◽  
Plate Type

One of the results from Plate Type Research Reactor Bandung (PTRRB) research program is PTRRB core design. Previous study on PTRRB has not calculated neutron flux distribution at its central irradiation position (CIP). Distribution of neutron flux at CIP is of high importance especially in radioisotope production. In this study, CIP was modeled as a stack of four to five aluminum tubes (AT), each filled by four aluminum irradiation capsules (AIC). Considering AIC dimension and geometry, there are three possibilities of AT configuration. For irradiation sample, 1.45 gr of molybdenum (Mo) was put into AIC. Neutron flux distribution at Mo sample was calculated using TRIGA MCNP and MCNP software. The calculation was simulated at condition when fresh fuel is loaded into reactor core. Analyses of excess reactivity show that, after installing irradiation AT and Mo sample was put into each configuration, the excess reactivity is less than 10.9 %. The highest calculated thermal neutron flux at Mo sample is 5.08×1013 n/cm2.s at configuration 1. Meanwhile, the highest total neutron flux at Mo sample is located at capsule no. II and III. Thermal neutron flux profile is the same for all configurations. This result will be used as a basic data for PTRRB utilization.Keywords: Central Irradiation Position, Neutron Flux Distribution, MCNP, PTRRB

scholarly journals Optical Simulation and Experimental Verification of a Fresnel Solar Concentrator with a New Hybrid Second Optical Element

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Guiqiang Li ◽  
Yi Jin
Keyword(s):  
Optical Properties ◽  
Concentration Ratio ◽  
Flux Distribution ◽  
Deflection Angle ◽  
Optical Element ◽  
Fresnel Lens ◽  
Optical Simulation ◽  
Solar Concentrator ◽  
Optical Efficiency ◽  
Solar Concentrators

Fresnel solar concentrator is one of the most common solar concentrators in solar applications. For high Fresnel concentrating PV or PV/T systems, the second optical element (SOE) is the key component for the high optical efficiency at a wider deflection angle, which is important for overcoming unavoidable errors from the tacking system, the Fresnel lens processing and installment technology, and so forth. In this paper, a new hybrid SOE was designed to match the Fresnel solar concentrator with the concentration ratio of 1090x. The ray-tracing technology was employed to indicate the optical properties. The simulation outcome showed that the Fresnel solar concentrator with the new hybrid SOE has a wider deflection angle scope with the high optical efficiency. Furthermore, the flux distribution with different deviation angles was also analyzed. In addition, the experiment of the Fresnel solar concentrator with the hybrid SOE under outdoor condition was carried out. The verifications from the electrical and thermal outputs were all made to analyze the optical efficiency comprehensively. The optical efficiency resulting from the experiment is found to be consistent with that from the simulation.

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