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.

Slope Error Measurements of Parabolic Troughs Using the Reflected Image of the Absorber Tube

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Steffen Ulmer ◽  
Boris Heinz ◽  
Klaus Pottler ◽  
Eckhard Lüpfert
Keyword(s):  
Digital Camera ◽  
Observation Point ◽  
Fast Method ◽  
Image Analysis Algorithm ◽  
Measurement Results ◽  
Close Range ◽  
Photogrammetric Method ◽  
Slope Error ◽  
Geometric Relationship ◽  
Good Agreement

A new and fast method for optically measuring the reflector slope of parabolic troughs with high accuracy has been developed. It uses the reflection of the absorber tube in the concentrator, as seen from some distance, and is therefore called “absorber reflection method.” A digital camera is placed at a distant observation point perpendicular to the trough axis with the concentrator orientated toward it. Then, a set of pictures from the absorber tube reflection is taken with slightly different tilt angles of the concentrator. A specially developed image analysis algorithm detects the edges of the absorber tube in the reflected images. This information, along with the geometric relationship between the components, the relative collector tilt angles, and the known approximately parabolic shape of the concentrator, is used to calculate the slopes perpendicular to the trough axis. Measurement results of a EuroTrough segment of four facets are presented and verified with results from a reference measurement using high-resolution close-range photogrammetry. The results show good agreement in statistical values as well as in local values of the reflector slope. Compared to the existing photogrammetric method, the new technique reduces drastically the time measurement.

scholarly journals RESEARCH OF DIGITAL CAMERA DYNAMIC RANGE ON THE IMAGING PROCESSING BASIS

2017 ◽  
Vol 8 (3) ◽  
pp. 271-278
Author(s):  
M Sutkowski ◽  
Ya. N. Saukova
Keyword(s):  
Dynamic Range ◽  
Digital Camera ◽  
Measuring Channel ◽  
Blue Color ◽  
Lower And Upper Bounds ◽  
Color Target ◽  
Color Channel ◽  
Imaging Processing ◽  
Colorimetric Measurements ◽  
Target Sets

Digital images provide to determine photometric and colorimetric properties of objects subject to validation all elements of a measuring channel (digital camera, software, display) and solve the problem of their limited dynamic ranges. The aim of the study was to explore the dynamic range of a digital camera for use in photometric and colorimetric measurements.The Laboratory of Photonics at the Institute of Microelectronics and Optoelectronics (Warsaw Technical University, Poland) conducted a comparative experiment to determine the threshold of sensitivity, linearity and range of application the digital camera. Color target sets with certified brightness and chromaticity were created at the terminals and recorded with a digital camera with different exposure times. The authors propose a method to extend the dynamic range of a digital camera for red, green and blue color channel of intensities by pairing the calibration dependencies, and determine the true brightness and color of a point on the object by calculation.Calibration dependencies (triads) of digital camera for red, green and blue color channels intensities were constructed. These dependences allow determining lower and upper bounds of the dynamic range. Each triad has a form of the hysteresis loop. The experiment showed that the accuracy of this method is ± 3–5 %. 

Maximization of Exergy Gain in High Temperature Solar Thermal Receivers by Choice of Pipe Radius

1991 ◽  
Vol 113 (2) ◽  
pp. 337-340 ◽  
Author(s):  
P. Bannister
Keyword(s):  
Power Systems ◽  
Thermal Power ◽  
Solar Thermal ◽  
Working Fluid ◽  
Pumping Power ◽  
Design Values ◽  
Parabolic Dish ◽  
Solar Thermal Collectors ◽  
Pipe Radius ◽  
Typical Design

The problem of optimizing the radius of boiler tubes in a radiation-dominated environment such as a solar thermal power receiver is examined. The trade-off between heat transfer and pumping power is investigated, resulting in an explicit expression for the radius that maximizes the net exergy gain under turbulent flow conditions. The effect of the pumping power being generated on site is included, thus making the result particularly applicable to the design of stand-alone power systems. Examples using typical design values for small parabolic dish solar thermal collectors using water and steam as the working fluid are given to illustrate the characteristics of the problem.

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.

Photogrammetry: An Available Surface Characterization Tool for Solar Concentrators, Part II: Assessment of Surfaces

1997 ◽  
Vol 119 (4) ◽  
pp. 286-291 ◽  
Author(s):  
M. Shortis ◽  
G. Johnston
Keyword(s):  
Gaussian Distribution ◽  
Surface Characterization ◽  
Flux Distribution ◽  
Focal Point ◽  
Three Dimensional ◽  
Close Correlation ◽  
Solar Concentrators ◽  
Surface Normal ◽  
Normal Vectors ◽  
Reflecting Surfaces

In a previous paper, the results of photogrammetric measurements of a number of paraboloidal reflecting surfaces were presented. These results showed that photogrammetry can provide three-dimensional surface characterisations of such solar concentrators. The present paper describes the assessment of the quality of these surfaces as a derivation of the photogrammetrically produced surface coordinates. Statistical analysis of the z-coordinate distribution of errors indicates that these generally conform to a univariate Gaussian distribution, while the numerical assessment of the surface normal vectors on these surfaces indicates that the surface normal deviations appear to follow an approximately bivariate Gaussian distribution. Ray tracing of the measured surfaces to predict the expected flux distribution at the focal point of the 400 m2 dish show a close correlation with the videographically measured flux distribution at the focal point of the dish.

A Color Error Correction Mode for Digital Camera

2010 ◽  
Vol 44-47 ◽  
pp. 3706-3710
Author(s):  
Han Kun Ye
Keyword(s):  
Color Space ◽  
Digital Camera ◽  
Color Management ◽  
Experimental Sample ◽  
Color Target ◽  
Polynomial Curve ◽  
Engineering Requirement ◽  
Color Error ◽  
Image Production ◽  
Color Conversion

Digital camera is the one of the main devices in the computer and multimedia technology and its color management model is the key to guarantee the color consistency in the succedent image production and transfers. The paper presents a color conversion model for digital camera based on polynomial curve generation. First, color rendering principle of digital camera is analyzed. Then digital camera data is pretreated to a unitary field to deduce final model. Third, standard color target is taken for experimental sample and substitutes color blocks in color shade district for complete color space to solve the difficulties of experimental color blocks selecting; Fourth, the model using polynomial curve generation algorithm to correct color error is deduced; Finally, the realization and experiment results show that, compared with some methods which have relatively high accuracy, the algorithm can improve color conversion accuracy and can satisfy the engineering requirement in digital camera color management

scholarly journals An Inviscid Low-Solidity Cascade Design Routine

1993 ◽  
Author(s):  
Jerry G. Myers ◽  
Terry Wright
Keyword(s):  
Experimental Data ◽  
Accurate Method ◽  
Analysis Procedure ◽  
Suitable Method ◽  
Design System ◽  
Design Technique ◽  
Axial Fan ◽  
Design Information ◽  
Design Values

An investigation was performed to determine a suitable method of designing and analyzing the performance of straight axial fan cascades of solidities below 0.6. The methods investigated included direct interpolation between design values obtained from experimental data at solidities of 0.6 and isolated airfoil theory predictions. A new inviscid design technique developed from a simplified low-solidity analysis procedure by J. Horlock and K. Tanabe was also developed. Testing of these methods was performed using a PC based inviscid “panel” routine developed by McFarland at NASA-Lewis. Results of the investigation yielded a reasonably accurate method for the design of axial fan cascades for solidities ranging from 0.2 to 0.6 which can supplement an existing design system that requires cascade design information lying beyond the range of NACA testing.

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 DIGITAL ELEVATION MODEL FROM NON-METRIC CAMERA IN UAS COMPARED WITH LIDAR TECHNOLOGY

2015 ◽  
Vol XL-1/W4 ◽  
pp. 411-414
Author(s):  
O. M. Dayamit ◽  
M. F. Pedro ◽  
R. R. Ernesto ◽  
B. L. Fernando
Keyword(s):  
Digital Elevation Model ◽  
Digital Camera ◽  
Accurate Method ◽  
Analysis Data ◽  
Modern Technology ◽  
Geographic Space ◽  
Digital Elevation ◽  
Dem Accuracy ◽  
Elevation Model ◽  
Short Time

Digital Elevation Model (DEM) data as a representation of surface topography is highly demanded for use in spatial analysis and modelling. Aimed to that issue many methods of acquisition data and process it are developed, from traditional surveying until modern technology like LIDAR. On the other hands, in a past four year the development of Unamend Aerial System (UAS) aimed to Geomatic bring us the possibility to acquire data about surface by non-metric digital camera on board in a short time with good quality for some analysis. Data collectors have attracted tremendous attention on UAS due to possibility of the determination of volume changes over time, monitoring of the breakwaters, hydrological modelling including flood simulation, drainage networks, among others whose support in DEM for proper analysis. The DEM quality is considered as a combination of DEM accuracy and DEM suitability so; this paper is aimed to analyse the quality of the DEM from non-metric digital camera on UAS compared with a DEM from LIDAR corresponding to same geographic space covering 4 km2 in Artemisa province, Cuba. This area is in a frame of urban planning whose need to know the topographic characteristics in order to analyse hydrology behaviour and decide the best place for make roads, building and so on. Base on LIDAR technology is still more accurate method, it offer us a pattern for test DEM from non-metric digital camera on UAS, whose are much more flexible and bring a solution for many applications whose needs DEM of detail.

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.

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