Solar Energy, Vol.200, 76-88, 2020
CSP on fluidized particles with a beam-down reflector: Comparative study of different fluidization technologies
This paper presents two simple numerical models to analyze the behavior of two different fluidization technologies with concentrated solar energy on the top of the bed. A bubbling fluidized bed, which operates with low particle size (Geldart A-B particles with d(p) = 0.1 - 0.5 mm) and a spouted bed, which uses particles with larger sizes (Geldart D with d(p) greater than or similar to 1 mm). Two cases were studied with the same mass of particles (150 kg), considering the same incident solar radiation concentrated on the top of the bed (50 kW). The results obtained indicate that the airflow rate in the bubbling fluidized bed has a notable effect on the maximum temperature reached in the bed. Increasing the airflow rate (from 1.5 to 2.5 times the minimum fluidization velocity), the maximum temperature reached in the bed is reduced from 950 to 750 K. In the spouted bed, higher temperatures are reached (over 1000 K), although it takes almost 4 times longer for the temperature to be reached than in the bubbling bed. Consequently, the charging efficiency, defined as the energy stored in the particles divided by the solar energy concentrated on the bed, are similar for both cases.