Comparative energy and exergy performance investigation of forced convection solar air collectors with cherry stone powder

The purpose of this study is to design new solar air collectors (SACs), to ensure that designed SACs continue to operate in cloudy weather and after sunset and to evaluate in terms of energy and exergy whether the cherry stone/powder will be appropriate to use as a sensible thermal energy storage (STES) material. The experiments were performed for a powdered cherry stones SAC (Type I), a cherry stones SAC (Type II), and a flat plate SAC (Type III) at seven different air mass flow rates (from 0.004 kg/s to 0.048 kg/s). Average thermal efficiency fluctuated between 6.05% and 39.99%, depending on the air mass flow rates under which the experiments were performed and whether the collectors have heat storage. The maximum difference in daily collector efficiency is in Type II, with a slight difference from Type I, which was 18.7% higher than the Type III. The inlet -outlet air temperatures of Type I and Type II were equaled 5 and 4 h after sunset, respectively, compared to the flat plate collector. The exergy efficiency ranged from 1% to 7% during the charging period. As a result, it can be seen that the use of cherry stone/ powder as a STES material is promising in contributing to the collector sustainability. (C) 2019 Elsevier Ltd. All rights reserved.