scholarly journals Development of an Elevation–Fresnel Linked Mini-Heliostat Array

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 4012
Author(s):  
Isaías Moreno-Cruz ◽  
Juan Carlos Castro ◽  
Omar Álvarez-Brito ◽  
Hilda B. Mota-Nava ◽  
Guillermo Ramírez-Zúñiga ◽  
...  
Keyword(s):  
Analytical Study ◽  
Flux Distribution ◽  
Radiative Flux ◽  
Tracking Performance ◽  
Wind Loads ◽  
The Sun ◽  
Slope Error ◽  
Critical Components ◽  
Mean Concentration ◽  
Concentration Ratios

Heliostats are critical components of solar tower technology and different strategies have been proposed to reduce their costs; among them diminishing their size to reduce wind loads or linking nearby heliostats mechanically, to reduce the overall number of actuators. This document aims to describe the development of a linked array of mini-heliostats which move together in an elevation–Fresnel configuration. This configuration consists of an array of mirrors rotating around linked parallel axes, in a linear Fresnel style with an added elevation mechanism allowing all axes to incline simultaneously in the plane North–South–Zenith; that is equivalent to an array of N linked mini-heliostats moved by only two drives instead of 2N. A detailed analytical study of the Sun-tracking performance of this kind of heliostat arrays was carried out, and an 8-mirror prototype based on optical and mechanical analyses was designed, built and tested. Even though the mirrors are flat, the array produced a rather compact radiative flux distribution on the receiver. The flux distribution is compatible with a slope error of the order of 1 mrad. Peak and mean concentration ratios reached 6.89 and 3.94, respectively.

The 0.12-2.5 micron Absolute Flux Distribution of the Sun for Comparison With Solar Analog Stars

1996 ◽  
Vol 112 ◽  
pp. 307 ◽  
Author(s):  
Luis Colina ◽  
Ralph C. Bohlin ◽  
Fiorella Castelli
Keyword(s):  
Flux Distribution ◽  
The Sun ◽  
Absolute Flux

scholarly journals Ruggedizing Printed Circuit Boards Using a Wideband Dynamic Absorber

2003 ◽  
Vol 10 (3) ◽  
pp. 195-210 ◽  
Author(s):  
V.C. Ho ◽  
A.M. Veprik ◽  
V.I. Babitsky
Keyword(s):  
Analytical Study ◽  
Printed Circuit Boards ◽  
Circuit Boards ◽  
Sinusoidal Vibration ◽  
Printed Circuit ◽  
Novel Approach ◽  
Dynamic Absorber ◽  
Commercial Off The Shelf ◽  
Scale Experiment ◽  
Critical Components

The existing approaches to ruggedizing inherently fragile and sensitive critical components of electronic equipment such as printed circuit boards (PCB) for use in hostile industrial and military environment are either insufficient or expensive. This paper addresses a novel approach towards ruggedizing commercial-off-the-shelf PCBs using a miniature wideband dynamic absorber. The optimisation technique used relies on the experimentally measured vibration spectra and complex receptance of the original PCB.The analytical study and full-scale experiment show that an optimised wideband dynamic absorber with the mass of only 15% relative to the total mass of the PCB is quite capable of the essential suppression of all relevant resonant responses of the PCB under shock, wideband random and sinusoidal vibration with variable frequency.

scholarly journals Pharmaceutico analytical study of Shodhita Shilajatu

2020 ◽  
Vol 5 (05) ◽  
pp. 214-219
Author(s):  
Arya Elias ◽  
Pramod C. Baragi ◽  
Kashinath Hadimur ◽  
K. A. Patil ◽  
Khazi Rahimbi
Keyword(s):  
Crystal Structure ◽  
Chemical Analysis ◽  
Analytical Study ◽  
Amorphous Material ◽  
Total Yield ◽  
Xrd Analysis ◽  
The Sun ◽  
Physico Chemical ◽  
Metallic Impurities

Background: Shilajatu or Adrija is one of the Maharasa, which is considered as a wonderful medicine in Ayurveda. It is named as it comes out of the stones heated by the sun in summer in the form of thick blackish exudation having many shades. Since it contain stone, mud, wood, sand and various physical and metallic impurities, Shodhana (Purification) of Shilajatu is a mandatory procedure. It has been used as a prime ingredient in many formulations mainly for Prameha, Sotha, Pandu Roga, Kshaya, Swasa, Pliha Vrudhi, Jwara, Agnimandya, Apasmara, etc. Objectives: Shodhana of Ashudha Shilajatu and Physico chemical analysis of Shodhita Shilajatu. Materials and Methods: Bhringaraja Swarasa for Shodhana of Shilajatu. Results:It took 8 days for completion of Shilajatu Shodhana. XRD Analysis report indicates that the sample Shilajatu was Amorphous material. Conclusion: Total yield of Shodhita Shilajatu was 99.6%. The Sample of Shilajatu was found to be Amorphous material in XRD Analysis hence crystal structure was not identified.

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 Faint solar analogues at the limit of no reddening

2019 ◽  
Vol 629 ◽  
pp. A33 ◽  
Author(s):  
R. E. Giribaldi ◽  
G. F. Porto de Mello ◽  
D. Lorenzo-Oliveira ◽  
E. B. Amôres ◽  
M. L. Ubaldo-Melo
Keyword(s):  
Principal Component Analysis ◽  
Solar System ◽  
Effective Temperature ◽  
Flux Distribution ◽  
Principal Component ◽  
Surface Gravity ◽  
The Sun ◽  
Spectral Indices ◽  
Atmospheric Parameters ◽  
Solar System Bodies

Context. The flux distribution of solar analogues is required for calculating the spectral albedo of solar system bodies such as asteroids and trans-Neptunian objects. Ideally a solar analogue should be comparatively faint as the target of interest, but very few analogues fainter than V = 9 mag have been identified so far. Only atmospheric parameters equal to solar guarantee a flux distribution equal to solar as well, while only photometric colours equal to solar do not. Reddening is also a factor to consider when selecting faint analogue candidates. Aims. Our aim is to implement the methodology for identifying faint analogues at the limit of precision allowed by the current spectroscopic surveys. We quantify the precision attainable for the atmospheric parameters of effective temperature (Teff), metallicity ([Fe/H]), and surface gravity (log g) when derived from moderately low-resolution (R = 8000) spectra with S∕N ~ 100. We estimate the significance of reddening at 100–300 pc from the Sun. Methods. We used the less precise photometry in the HIPPARCOS catalogue to select potential analogues with V ~ 10.5 mag (located at ~135 pc). We calibrated Teff and [Fe/H] as functions of equivalent widths of spectral indices by means of the principal component analysis regression. We derived log g, mass, radius, and age from the atmospheric parameters, Gaia parallaxes, and evolutionary tracks. We evaluated the presence of reddening for the candidates by underestimations of photometric Teff with respect to those derived by spectral indices. These determinations were validated with extinction maps. Results. We obtained the atmospheric parameters Teff, [Fe/H], and log g with precision of 97 K, 0.06 dex, 0.05 dex, respectively. From 21 candidates analysed, we identify five solar analogues: HIP 991, HIP 5811, and HIP 69477 have solar parameters within 1σ errors, and HIP 55619 and HIP 61835 within 2σ errors. Six other stars have Teff close to solar, but slightly lower [Fe/H]. Our analogues show no evidence of reddening except for four stars, that present E(B−V) ≥ 0.06 mag, translating to at least a 200 K decrease in photometric Teff.

Comparative Study of Solar Optics for Paraboloidal Concentrators

1980 ◽  
Vol 102 (4) ◽  
pp. 305-315 ◽  
Author(s):  
L. Wen ◽  
L. Huang ◽  
P. Poon ◽  
W. Carley
Keyword(s):  
Flux Distribution ◽  
Computational Method ◽  
Optical Parameters ◽  
Solar Concentrator ◽  
Surface Slope ◽  
Algebraic Form ◽  
Reflector Surface ◽  
Slope Error ◽  
Definition Of ◽  
Limb Darkening

Different analytical methods for computing the flux distribution on the focal plane of a paraboloidal solar concentrator are reviewed. An analytical solution in algebraic form is also derived for an idealized model. The effects resulting from using different assumptions in the definition of optical parameters used in these methodologies are compared and discussed in detail. These parameters include solar irradiance distribution (limb darkening and circumsolar), reflector surface specular spreading, surface slope error, and concentrator pointing inaccuracy. The type of computational method selected for use depends on the maturity of the design and the data available at the time the analysis is made.

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