VISdish: A new tool for canting and shape-measuring solar-dish facets

Abstract

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.

Scaling effects of a novel solar receiver for a micro gas-turbine based solar dish system

“…Montecchi et al [22] characterized the solar dish performance installed at the ENEA Casaccia Research center using the VISdish tool for canting and shape-measuring of solar-dish facets in combination with the ray-tracing tool SIMULDISH to predict the flux distribution around the focal spot. During the experimental campaign the surface error of 149'736 measurement points on the dish was determined in horizontal and vertical direction.…”

“…For this work the probability density function (PDF, cp. [32]) of the surface error was determined for both the zenith and azimuth angle based on the experimental data provided by Montecchi et al [22]. The results for 200 bins are shown in Figure 9 with the distribution of the zenith angle error at the top and the azimuth angle error at the bottom.…”

“…In the ray-tracing implemented in this work the dish surface error is determined stochastically according to the PDFs presented in Figure 9 whereas Montecchi [22] considers the measured values of the surface error for each point individually as obtained during the measurement campaign.…”

“…The MATLAB based Monte Carlo ray-tracing for the solar dish is calibrated using the experimental characterization of the solar dish surface error and the complete ray-tracing work undertaken by Montecchi [22]. The calibration was implemented for a direct normal irradiance (DNI) value of 800 W/m² which is the design value for the OMSoP solar dish installed at the ENEA Casaccia Research Center.…”

“…In earlier work [20] a new receiver concept was designed for the integration into a MGT solar dish with boundary conditions derived from the Eurodish concentrator [7]. In this work the concept is adapted to fit the specific OMSoP boundary conditions [21] [22]. The development process of solar receivers for CSP plants often involves the testing of a scaled version in a laboratory environment with controllable testing conditions and reduced system complexity as compared to the full-scale system.…”