Thermal and hydrodynamic behavior of ceramic volumetric absorbers for central receiver solar power plants: A review

This paper presents an extensive review of the thermal and hydrodynamic behavior of conventional ceramic volumetric absorbers, i.e. monolithic honeycombs and open-cell foams. It is intended to provide scientific support to the design of more efficient absorbers with novel structures and materials, based on a further understanding of how the characteristics of conventional absorbers modify their performance. This review identifies radiative and thermal properties that a good absorber must have, providing reference values for SiC absorbers. An overview on how the typical manufacturing process modifies their properties is also presented. Significance of geometrical parameters and radiative and thermal properties of both type of absorbers, as well as the effects of incoming light direction on the solar radiation propagation and the solid-air temperature distributions within their structure are discussed. Typical operating conditions of these elements are given. Their characteristic outlet air temperature and thermal efficiency are compared and discussed. The different mechanisms that are responsible for the pressure drop in these elements are identified, and their influence on the heat transfer mechanisms is analyzed. To conclude, factors that promote the appearance of flow instabilities are described. (C) 2015 Elsevier Ltd. All rights reserved.