Spectra management through hybrid nanofluid for sustainable cooling of agricultural greenhouses: An experimental study

In the present experimental work, optically tuned CuS (99%)-MgO (1%)/water hybrid nanofluid (with a concentration of 0.005 wt.%) was synthesized to develop a distinct strategy for maintaining optimal temperature conditions inside greenhouses in hot arid climates. The nanoparticles showed good suspension in the water. The flow of nanofluid was directed through a duct connected to a small-scale greenhouse unit and positioned in front of a solar simulator in the lab environment. It was found that the nanofluid application reduced the greenhouse inside temperature under all ambient temperature ranges and solar irradiances. The results further showed an average of 21.9% reduction in the heat gained by cooling system for the nanofluid case than the no-fluid case. In addition, the nanofluid achieved a photothermal conversion efficiency of 52.9%. Meanwhile, the calculated crop growth factor was 72.1%. The application of optically tuned CuS-MgO/water hybrid nanofluid in the greenhouse will have a minimal effect on the growth of many plants, as the decrease in photosynthetic photon flux density inside the greenhouse unit is insignificant. Furthermore, the payback period calculated for the nanofluid system was 0.55 year for an electricity price of 0.1 $/kWh. Moreover, the results are expected to provide sustainable solutions to greenhouses, especially located in hot arid climates, by keeping the temperatures at the desired levels.