Capabilities of α-Al2O3, γ-Al2O3, and bentonite dry powders used in flat plate solar collector for thermal energy storage

In this experimental study, a flat plate solar collector was constructed and examined for absorbing and transferring heat from soil to fluid. The light source was an infrared lamp with average illumination intensity of 3150 lux. For the first time, alpha-Al2O3, gamma-Al2O3, and Bentonite powder were used for heat absorption, storage, and its transfer to the operating fluid. The average particles size of alpha-Al2O3, gamma-Al2O3, and Bentonite were 150 mm, 45 mm, and 75 mm, respectively. The operating fluid was distilled water. The absorption efficiency of alpha-Al2O3, gamma-Al2O3 and Bentonite was 5.50%, 30.90%, and 9.99%, respectively, in the absence of operating fluid. However, the absorption efficiency of alpha-Al2O3, gamma-Al2O3 and bentonite powders increases to 55.23%, 89.45%, and 70.50%, respectively in presence of circulating fluid circulates. The physical properties of all samples were evaluated to check the repeatability of the experiments using various analyses i.e., FT-IR, XRD, SEM, XRF, DSC and BET. Results indicated, before and after infrared radiation, there are no significant changes in the state of gamma-Al2O3 and bentonite samples. According to the results of BET and SEM analyses, due to the higher surface areas of gamma-Al2O3 and Bentonite than alpha-Al2O3, they have more active sites. Results also indicated that the caking of the sample particles occurs less frequently. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

In this experimental study, a flat plate solar collector using alpha-Al2O3, gamma-Al2O3, and Bentonite powder was constructed for heat absorption and transfer. The presence of circulating fluid significantly increased absorption efficiency, particularly for gamma-Al2O3 and Bentonite due to their larger surface areas and more active sites. Results from various analyses showed no significant changes in the state of gamma-Al2O3 and Bentonite samples before and after infrared radiation.