Direct Irradiation Absorption by Nanofluids: A Proposal of Standardization by the Use of the “Solar Wall”

We analyzed the behavior of a “Solar Wall” and validated the apparatus using three nanofluids (silver, titanium dioxide, and a hybrid compound) based on their photothermal conversion performance. The factors considered were the temperature gain in relation to the base fluid, the stored energy, and the specific absorption rate. A cost analysis was conducted to assess the cost associated with energy generation for each nanofluid. Five concentrations were studied for each nanofluid. A hybrid nanofluid formed by the previous ones was also tested. The results show that the Solar Wall demonstrates repeatability, indicating it is suitable for testing other nanofluids. The silver and hybrid nanofluids performed better; the former achieved a temperature increase of 10.2 °C relative to the base fluid, and the latter reached 9.9 °C. Regarding energy gain, the silver-based sample achieved 31.93%, and the hybrid sample achieved 34.52%. The SAR values for the silver nanCheckedofluid were higher than those for the titanium-based; the cost to generate an energy unit using the former was higher than in the titanium case. The silver-based and hybrid nanofluids obtained showed improved photothermal conversion, making them the most promising options.