Thermal assessment of a dual-purpose air/water heating system with perforated concrete matrix and water storage

The main objective of this study is to design and optimize an innovative concrete based dual-purpose solar collector with working fluids of air and water. The system is designed, built, and tested in the Tunisian climate, and its main feature is that it warms both air and water. Different configurations have been tested and analyzed based on the air/water inlet positions and the convection mode, in order to determine the highest thermal efficiency for given solar energy input. The findings indicate that perforations enhance the surface area for heat absorption and facilitate better airflow, whereas the water storage tank acts as a dependable thermal mass for storing and stabilizing the collected energy. For example, the air outlet temperature reached 30 °C at night. This illustrates the effectiveness of using both concrete and water as thermal energy storage mediums, highlighting the superior thermal potential of the developed system in comparison to traditional solar heating systems. The collector’s dual-fluid efficiency is 80.59 % while operating under the air forced convection regime, and 79.77 % when using an up-water input. Therefore, there is potential for application in the areas of space heating and residential hot water use, particularly in cold climates.