Improving thermal performance of a solar thermal/desalination combisystem using nano fluid-based direct absorption solar collector

Depletion of freshwater resources and reduction of rainfall in arid areas causes water scarcity, which is intensified by population and urbanization growth. In this study, a small-scale solar thermal/desalination combisystem using nanofluid-based direct absorption solar collectors and humidification-dehumidification desalination unit is proposed to supply domestic hot water, space heating, and freshwater demands of a residential building. The dynamic simulation of the system performance in the Hot-Dry climate zone is done using TRNSYS-MATLAB co-simulator. The results indicate that using the proposed combisystem reduces 94.3% and 17% of annual energy consumption for providing domestic hot water and space heating demands, respectively. The freshwater demand is supplied in the range of 11.3% to 100%. In the case of using a flat plate solar collector, the solar fraction for domestic hot water and space heating demands in comparison with nanofluid-based direct absorption solar collectors reduces by 3.7% and 1.7%, respectively. Furthermore, the produced freshwater reduces 18% on average. The payback time using nanofluid-based direct absorption and flat plate solar collectors are 6.4 and 7.8 years, respectively.