Eventos Anais de eventos
CONEM 2022
XI Congresso Nacional de Engenharia Mecânica - CONEM 2022
Effect of the interception factor with the variation of the receiver’s aperture area of a Scheffler concentrator
Submission Author:
Isabel Kodama Correa de Moraes , SP
Co-Authors:
Isabel Kodama Correa de Moraes, Erick Dib, Flavio Augusto Sanzovo Fiorelli
Presenter: Isabel Kodama Correa de Moraes
doi://10.26678/ABCM.CONEM2022.CON22-0445
Abstract
The demand for more sustainable and low-carbon energy sources and a greater efficiency of energy conversion processes has been increasing due to the depletion of fossil fuels, the increase in energy consumption, the need to reduce environmental pollution, and curb climate change. Solar energy is an alternative source with potential for growth. Due to its low density, means of concentrating energy are used to achieve higher temperatures, which expands the application fields of solar energy. In this paper, a 2 m² Scheffler concentrator at the equinox was studied, whose geometry corresponds to the side section of a paraboloid bounded by an elliptical frame. Scheffler concentrators are equipped with two tracking axes (daily and seasonal) and a flexible surface, which allow focus to remain in a fixed region as the solar declination and azimuth vary. The seasonal adjustment modifies the rim angles that interfere with the concentrator’s aperture area and the focal image’s size. The characteristics of this concentrator enable the solar beams to concentrate outside the projection of its frame, which prevents shadow formation on the reflecting surface. It belongs to the category of image-forming reflectors that collect and concentrate solar radiation on a fixed receiver for conversion to heat. To assist receiver designs that seek to avoid thermal losses and increase efficiency, the behavior of the interception factor was evaluated according to the variation of the receiver aperture area. The results also showed the seasonal variation of the concentrator aperture and focus geometry associated with optical deviations inherent to the construction process. The analysis was performed using the EES and MATLAB programs based on the numerical model and processing of data obtained from monthly experiments conducted from June to December 2021 with a target with a Lambertian property and a CMOS (complementary metaloxide semiconductor) sensor camera, that transforms the incoming light energy from each image point into a proportional electrical signal. The diffuse surface allows the photograph of the image produced by the radiation on the target to accurately represent the reflected flux converted from the pixel readout. The camera image records gray-scale intensity levels, which represents the way in which the beams reach the receiver. The correlation between the grayscale and the corresponding irradiance at the Lambertian target is linear, thus it is possible to characterize the distribution and identify the interception factor for a given area of the measurement plane.
Keywords
Solar Energy, Scheffler concentrator, Interception factor, Imaging, solar receiver
