Solar-Powered RO–Hydroponic Net House: A Scalable Model for Water-Efficient Tomato Production in Arid Regions

This study assessed six tomato (Solanum lycopersicum L.) cultivars within an integrated solar-powered closed hydroponic system in Al Dhaid, UAE (25°16′11.2″N, 55°55′52.2″E). The system combined an insect-proof net house, closed hydroponics, root-zone cooling, ultra-low-energy drip irrigation, and a cost-effective solar-powered reverse osmosis (RO) desalination unit to address salinity constraints. The cultivars, selected for their adaptability to controlled environments in the UAE, were evaluated for yield, water-use efficiency (WUE), and fertilizer-use efficiency (FUE). Among them, Torcida recorded the highest mean yield (0.619 kg m⁻² harvest⁻¹), WUE (27.1 kg m⁻³), FUE (26.5 kg fruit kg⁻¹ fertilizer), and marketable fruit ratio (66.3%), followed by Roenza, Eviva, and SV 4129 TH; Lamina was intermediate, while Saley, a bushy type, produced the lowest yield. The top cultivars achieved cumulative yields exceeding 7 kg m⁻²—surpassing regional open-field benchmarks (4–5 kg m⁻²; 3–6 kg m⁻³). Compared with conventional cooled hydroponic greenhouses (3.5 kg plant⁻¹; 8 kg m⁻³), the system demonstrated similar productivity using three times less water. The RO unit produced water at 1.05 US$ m⁻³—58–68% below regional tariffs—while minimizing reliance on grid electricity and mechanical cooling. Overall, the integrated solar-powered hydroponic–RO model proved technically reliable, resource-efficient, and economically viable, offering a scalable solution for sustainable veg-etable production in hyper-arid regions.