Abstract

We present the initial results for the comparative study of two types of reflecting surfaces for solar concentrating systems. We use two identical mirrors with different coatings: The first have an aluminium coating with SIO2 protection and the second was covered with the commercial film Reflectech®. This cover is used mainly for parabolic trough and has several advantages like a high reflectivity, low maintenance, and resistance to extreme weather conditions. Since this film was developed for concentrating solar applications, the purpose of this study is  exploring the potential application of the film in point focus concentrating systems.

Evaluation of two reflective Coatings for the Mirrors of The High Radiative-Flux Solar Furnace

Riveros-Rosas, R. Castrejón-García, C.A. Arancibia-Bulnes, C.A. Pérez-Rábago, C.A. Estrada

Publicado en Memorias de Congresos

Abstract

The paper presents the technical modifications of DEFRAC (Spanish acronym for Device for the Study of Highly Concentrated Radiative Fluxes) in order to obtain a mini-solar furnace (MSF). DEFRAC is placed in vertical position and the optical arrangement of facets is oriented viewing to the north. A small flat heliostat system with 5.6 m2 of surface area was designed and constructed to track the movement of the sun and redirect sunlight along to the optical axis of the fixed DEFRAC the concentrator. The reflective surface of the heliostat is obtained by using a flat mirror with a tolerance lesser than 1 mrad. The MSF has a shutter with an area of 2.56 m2 that attenuates the solar energy reflected by the heliostat. In this paper we present the preliminary result of the optical performance for the MSF and the evaluation of the track system of the heliostat and the control of the shutter. The MSF will be used in the development of different kind of studies; from studies of heat transfer in open small cavities to the development of small receivers.

Mini-Solar Furnace by Using a Point Focus Solar Concentrator

Pérez-Rábago C.A., D. Riverso-Rosas, O.A. Jaramillo, M. Bazán, M. Carrillo-Santana, M. Montiel-González, G. Ascanio, C.A. Estrada

Publicado en Memorias de Congresos

Abstract

In the present work, the analysis of the first images obtained from de Solar Furnace of High Radiative Flux in Mexico is presented. The solar furnace has five different focal distance groups. The images were acquired using the first two groups of mirrors from complete optics of main concentrator. We used a Heliostat with a reflective surface of 36 m². The Images was captured with a CCD camera and the irradiance profile was modeled with a ray-tracing program in order to estimate the global optical error for the concentrator-heliostat optical system. The results shows that the optical error is less to 3 mrad and the calculations indicates that the flux peak for the complete groups of mirrors could be higher than 12 000 suns and the average flux could be higher than 5,000 suns.

Concentration Image Profiles of the High-Flux Solar Furnace of CIE-UNAM in Temixco, Mexico. First Stage

David Riveros-Rosas, Carlos A. Perez-Rabago, Camilo A. Arancibia-Bulnes, Ricardo Perez-Enciso, and Claudio A. Estrada

Publicado en Memorias de Congresos

Abstract

A new high flux solar furnace facility has been developed in Mexico. It is located in Temixco, Morelos, Mexico and in its first phase of development consists of a heliostat of 36 square meters (6 m by 6 m), a shutter made of stainless steel blades 6.2 m by 6.2 m, and a multifaceted concentrator of 211 spherical mirrors with an equivalent focal length of 3.64 m. In order to set the HFSF in operation, all the mirrors were aligned, the control system was developed and tested, the heliostat was aligned and its tracking movement tested. The purpose of this paper is to present the new facility and its first results in the evaluation of its capacities. The results show that the optical error is less to 3 mrad and the calculations indicates that the average flux could be higher than 5,000 suns and the facility can reach temperatures as high as 3406º C.

A New High-Flux Solar Furnace at CIE-UNAM in Temixco, México. First Stage

Claudio A. Estrada, Camilo A. Arancibia-Bulnes, Sergio Vazquez, Carlos A. Pérez-Rábago, David Riveros, Ricardo Perez-Enciso, Jesús Quiñones, Rafael Castrejón, Moises Montiel, Fermín Granados

Publicado en Memorias de Congresos

Abstract

The new high radiative flux solar furnace is being developed in Mexico at the Centro de Investigación en Energía of the Universidad Nacional Autónoma de México. The alignment of the facets of the concentrator is a key procedure to obtain the required energy distribution in the focal zone and to keep the global standard deviation of the optical errors low. We present a novel method for optical alignment of the facets; this alignment procedure requires a simple optical system, allows rapid alignment and guarantees the required accuracy. Preliminary results obtained with this procedure are discussed, which show that the facets alignment satisfactorily meets specifications.

S. Vazquez-Montiel, C.A. Pérez-Rábago, R. Pérez-Enciso, D. Riveros-Rosas, F. Granados-Agustin, C.A. Arancibia-Bulnes, C.A. Estrada

Method for Facets’ Alignment for the High-Flux Solar Furnace at CIE-UNAM in Temixco, Mexico. First Stag

Publicado en Memorias de Congresos

Abstract

This paper presents the control system design of a new high flux solar furnace that is being developed in Mexico at the Center for Energy Research of the National University of Mexico. The control of the whole system is critical for the correct operation of it. The control system consists of a rugged PC running state machine-based software which manages the operation of all the user interfaces for the furnace systems which are the heliostat, shutter, cooling, visual and data acquisition subsystems, as well as the positioning desk control. The control routines run in real-time controllers dedicated for each subsystem. The computer routines used by the main program and the tests made for characterizing the heliostat follow-up system is also described. Preliminary results obtained shows that the heliostat control presents great versatility due to the type of control it has, including the possibility of accepting feedback through images projected by it.

C.A. Pérez-Rábago, R. Guzmán-Galán, N. Flores-Guzmán, E. Brito, D. Marroqui-García, R. Pérez-Enciso, D. Riveros-Rosas, C.A. Arancibia-Bulnes, C.A. Estrada

Control System for the High-Flux Solar Furnace of CIE-UNAM in Temixco, Mexico. First Stage

Publicado en Memorias de Congresos

Abstract

This paper discusses the methods implemented for the solution of the drift and backslash problems in the heliostat of the High Radiative Flux Solar Furnace recently built at the Center for Energy Research of the Universidad Nacional Autónoma de México, located at the geographical coordinates 18° 50' 24" North and 99° 15' 00" West. To solve the observed drift, various algorithms were analyzed for the calculation of the solar vector,and a closed loop through an electronic device was implemented which makes corrections to the position of the heliostat. Drift was corrected by means of unbalancing the heliostat.

R. Pérez-Enciso, E. Brito-Bazan, C. A. Arancibia-Bulnes, D. Riveros-Rosas, C. A. Perez-Rábago, J.J.Quiñones, C. A. Estrada

Correction of the Concentrated Sunlight Spot’ s Drift of the CIE-UNAM Solar Furnace

Publicado en Memorias de Congresos

Abstract

Since August 2011, the 30 kWt Solar Furnace for Higher Radiative Fluxes (HoSIER) of the Renewable Energy Institute (former Center for Energy Research) of the National University of Mexico (IER-UNAM) is in operation. The optical design of the HoSIER-UNAM includes a total of 409 spherical facets, divided into 5 different focal length groups [1]. A ray-tracing simulation was carried out to realize a three-dimensional analysis of the concentrated solar radiation distribution at the focal area of the HoSIER. In this way, theoretical profiles of the radiative flux were obtained. To get the experimental profiles of the concentrated solar irradiance of the HoSIER, a Lambertian screen was placed in the focal zone, normal to the optical axis of the concentrator. The screen was movedalong 10 cm on the focus with each flat separated 5 mm of distance and in front of a CCD 8-bit digital camera. With the CCD was possible to obtain several experimental radiative flux distributions and thus it was possible to validate the ray-tracing simulation. This comparison shows a very good agreement between experimental and theoretical distribution.

R. Perez-Enciso, D. Riveros-Rosas, M. Sanchez, C.A. Pérez-Rabago, C.A. Arancibia-Bulnes, H. Romero-Paredes, C.A. Estrada

Three-dimensional analysis of solar radiation distribution at the focal zone of the solar furnace of IER-UNAM

Publicado en Memorias de Congresos

Abstract

In this work we show the analytical study of radiative heat exchange in a proposed calorimeter to measure the properties of absorptivity  and emissivity of materials under high temperatures produced by the highly concentrated solar radiation of the Solar Oven at Renewable Energy Institute of UNAM (HoSIER), that allowed us to detect the need for a modification to the design of the prototype in order to get proper measurements.

Estudios calorimétricos para la medición de propiedades opto-térmicas en sólidos sujetos a altas temperaturas y altos flujos radiativos

Moreno-Álvarez L., Pérez-Rábago C., Pérez-Enciso R., Estrada C.

Publicado en Memorias de Congresos

Abstract

Experimental results of the campaign to determine a method for measuring the temperature of a surface exposed to the highly concentrated radiation at HoSIERthrough three different conditions: quartz window, PYREX® window and without window are presented in this paper. It seeks to achieve a method for measuring the surface temperature without any thermocouple contact, preventing its overestimation due to the effect of the surface's radiosity itself.This methodology is able to determine a correction factor of the emissivity (FCε) depending on the incident temperature. In addition to determine the temperature difference overestimated due to the component of the radiation reflected by the surface.

Dependencia de la emisividad con la temperatura de una superficie receptora sometida a radiación altamente concentrada

Carlos Pérez-Rábago, Lúar Moreno-Álvarez, Ricardo Pérez-Enciso, Alejandro Bautista-Orozco y Claudio Estrada

Publicado en Memorias de Congresos
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