This study presents the design, performance and economic feasibility of a centralized solar-powered reverse osmosis (RO) desalination system for a residential compound of 10 buildings in Tripoli, Libya. Pretreatment was modeled using Aspen Plus V.12, and the RO unit was simulated with IMSDesign. The FilmTec CPA5-LD-4040 membrane produced permeate meeting WHO and Libyan drinking-water standards (e.g., TDS of 335 mg/L, pH of 7.6). A dosing-sensitivity analysis identified 93 mg/L of 5% Ca(OH)₂ solution as the optimal value for post-treatment stabilization. To minimize costs, the system was configured as a battery-free PV-powered design using 4 monocrystalline IBC Solar modules (395 W each, 1.58 kWp total). CO₂-emission sensitivity analysis showed a reduction of 7 kg CO₂/day during fully solar operation. The RO unit’s energy demand (7.8 kWh/day) is fully met by the PV array. The Levelized cost of water ranged between 8–21 LYD/m³ depending on lifetime and assumed discount rate. Compared to bottled water consumption for the 300-resident compound, the system provides substantial annual savings resulting in a payback period of 133 days. Overall, the results confirm the strong technical performance, economic viability, and long-term sustainability of deploying stand-alone PV-driven RO desalination for residential applications in Libya. This scientific manuscript was presented at the sessions of the International Renewable Energy, Gas, Oil and Climate Change Conference "iREGO" in the period of April 25-27, 2026. Tripoli - Libya............... Keywords:............ Solar Desalination; Reverse Osmosis; Calcium Hydroxide Dosing; Photovoltaic system.