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Analysis of radiation propagation inside a hierarchical solar volumetric absorber
* 1, 2 , 2 , 2 , 1
1  Sapienza University of Rome, Dept. of Mechanical and Aerospace Engineering, Via Eudossiana 18, Rome, Italy
2  Fondazione Bruno Kessler, ARES Unit, Via Sommarive, 18, 38123, Trento, Italy

Published: 12 September 2020 by MDPI in The First World Energies Forum session Primary Energy Sources (registering DOI)

The Solar Receiver is a critical component of concentrated solar power technology; it works as a heat exchanger, transforming the concentrated solar radiation into high-temperature heat. Volumetric receiver technology, using air as heat transfer fluid, are designed to reach higher temperatures than the current receiver technology, which is limited by material resistance and fluid instability. The higher temperature, up to 1200K, could be used in high-temperature industrial processes or a high-temperature thermodynamic cycle. A correct radiation propagation is essential to develop their performances, reducing reflection and emission losses and promoting the heat transfer to the fluid. In this study, the optical behaviour of Hierarchical Volumetric Receiver (HVR) developed in FBK has been studied using Monte-Carlo Ray Tracing (MCRT) simulations. The simulations have been validated in an experimental setup that evaluates the light transmissivity of the HVR porous structure. Two different HVR structures are evaluated with MCRT simulations that use a real solar dish geometry to configure a complete CSP plant. Results show that frontal and rear losses are, respectively, 12% and 3% of the incoming concentrated radiation. Inside the HVR, 15% of the incoming power is propagated trough the lateral void spaces. Therefore, the power spreading avoids the overconcentration of the centre of the focalized area. The HVR optical behaviour has been investigated, showing an optical efficiency of 85%.

Keywords: Concentrates Solar Power; Radiation propagation; Volumetric Receivers; Monte Carlo Ray Tracing; High-temperature heat