The escalating global water scarcity demands innovative, sustainable desalination solutions, particularly in arid regions. This study aims to enhance the productivity of spherical solar stills by integrating novel composite nanoparticle mixtures, conducting a holistic Energy, Exergy, Economic, and Environmental (4E) analysis under the harsh climate of Madinah, Saudi Arabia. The primary innovation lies in the formulation and comparative evaluation of quaternary nanocomposites (activated charcoal, titanium carbide, activated carbon, and yttrium oxide), assessing their synergistic effects against a higher concentration of a single material. The key results demonstrate that the optimal composite mixture (SSD3) increases freshwater yield by 20.1%, achieving 6.28 L/ m2/day, compared to a base case of 5.23 L/m2/day. This enhancement is driven by a 5 degrees C rise in operational temperatures, leading to a 0.30-0.70 improvement in thermal efficiency and a threefold increase in exergy efficiency. Economically, the system shows a promising cost per liter of $0.050 with a short payback period, while environmentally, it mitigates 1.82 tons of CO2 per year per square meter. These findings confirm that tailored composite nanoparticles significantly improve the performance and sustainability of spherical solar stills, offering a viable, low-carbon technology for decentralized water production in water-scarce regions. The results establish a performance benchmark and a scalable 4E evaluation framework, providing a foundation for future validation and optimization studies aimed at practical deployment.