Siwa Oasis, a remote desert region in Egypt, depends heavily on diesel generators, leading to high fuel costs, logistical challenges, and significant CO₂ emissions. This study evaluates hybrid renewable energy systems for the region using real-world data, considering three configurations: Case 1 (PV, BESS, Diesel), Case 2 (PV, Ternary Pumped Hydro Storage (T-PSH), Diesel), and Case 3 (PV, Wind, T-PSH, Diesel). T-PSH enhances system flexibility by enabling three operational modes—pumping, generation, and simultaneous pumping and generating—optimizing the management of surplus renewable energy.A novel Hybrid Cheetah Optimization with Particle Swarm Optimization (HYCHOPSO) algorithm, along with CHO, PSO, GWO, and SSIA, is used to optimize system performance. Results show that Case 1 achieves a COE of $0.03Fih/kWh with 210.6 tons/year emissions and a 61.9% renewable share. Case 2 has the COE ($0.592/kWh) but the highest emissions (525.3 tons/year) due to 91% diesel dependency, while Case 3 attains the lowest emissions (123.6 tons/year) with 69.8% renewable energy at a COE of $0.0935/kWh.These findings highlight the trade-offs between cost and environmental performance and demonstrate that hybrid systems with advanced storage and diversified renewables provide a viable pathway for sustainable energy management in isolated microgrids.