Solar dishes allow us to obtain highly concentrated solar fluxes used to produce electricity or feed thermal processes/storage. For practical reasons, the reflecting surface is composed by a number of facets. After the dish assembly, facet-canting is an important task for improving the concentration of solar radiation around the focus-point, as well as the capture ratio at the receiver placed there. Finally, flux profile should be measured or evaluated to verify the concentration quality. All these tasks can be achieved by the new tool we developed at ENEA, named VISdish. The instrument is based on the visual inspection system (VIS) approach and can work in two functionalities: canting and shape-measurement. The shape data are entered in a simulation software for evaluating the flux profile and concentration quality. With respect to prior methods, VISdish offers several advantages: (i) simpler data processing, because light point-source and its reflections are univocally related, (ii) higher accuracy. The instrument functionality is illustrated through the preliminary experimental results obtained on the dish recently installed in ENEA-Casaccia in the framework of the E.U. project OMSoP.
Concentrating solar power plants use mirrors to redirect solar radiation toward receivers. Mirrors (facets) are suitably shaped to optimize the radiation capture ratio. Because deviations from ideal shape/slope degrade optical efficiency, the availability of reliable instruments for 3D shape measurement is essential. This paper deals with an innovative instrument, named VISproLF, specific for the case of facets for the primary reflector of linear Fresnel collectors. The instrument is simply composed of a LCD screen and a digital camera; to avoid artifacts, the camera must be equipped with a high quality lens and its characteristic matrix and distortion coefficients have to be accurately evaluated. The arrangement of the LCD screen and camera around the facet must follow the simple rule to view from the camera the facet surface entirely covered by the image of the screen. Then, the position and attitude of the camera (first) and LCD screen (second) are accurately evaluated by a simple procedure based on the pinhole camera model, which makes the instrument self-calibrating. The shape and slope of the facet surfaces are obtained by processing five binary images by means of a completely digital method of which a detailed description is given. In the experimental arrangement used to prepare the present paper, the slope accuracy is about 0.2 mrad. With respect to the most common instruments based on the Fringe reflection technology, VISproLF offers two great advantages: full-digital image processing and a self-calibration feature.
In Concentrating Solar Power plants, reflective panels are used to redirect solar radiation towards a receiver. Because the panel shape drives the radiation distribution around the focus where the receiver is placed, the 3D measurement is fundamental to assess the panel shape quality. The VISproPT instrument is the advanced version of the prototype VISprofile; these instruments are designed for indoor measuring of the 3D shape of parabolic-trough reflective panels. The VIS proPT hardware has been manufactured by MARPOSS Italia Spa and funded by EU project ’Solar Facilities for the European Research Area - Third Phase’ (SFERA-III), while the image processing software as well as the calibration procedure, based on the measurement of a perfectly flat surface as that of a calm body of water, have been developed by Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). The instrument precision is better than 0.1 mrad and 0.3 mm (root mean square value over an area 1.2 × 0.8 m2), for slope and height of the surface respectively. Technical details of experimental set up and calibration-procedure are here reported. The instrument effectiveness is shown by reporting the results obtained on a set of 10 specimen (5 inner + 5 outer) adopted to run the SFERA-III WP10 Task3 round-robin on 3D shape measurements among the different instruments used by the Fraunhofer Institute for Solar Energy Systems ISE (F-ISE), Deutsches Zentrum Fuer Luft - und Raumfahrt EV (DLR), the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (SANDIA).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.