Makebe, Rethabile2026-06-172026-06-172025https://hdl.handle.net/20.500.14155/2362This dissertation examines the design, efficacy, and viability of a hybrid solar photovoltaic-thermal (PVT) and ultraviolet (UV) water purification system specifically developed for rural Lesotho, featuring a case study in the Mohale Basin. The system incorporates thermal energy capture by the solar PVT array to preheat feedwater before reverse osmosis (RO) treatment, hence improving membrane efficiency and minimizing fouling hazards. The electricity produced by the PVT array energizes UV disinfection devices and water pumps, while battery storage guarantees continuous operation under low solar irradiance circumstances. Two optimized setups, that is, 5.2 kWp and 14.4 kWp were simulated by PVsyst, underpinned by mathematical modelling and validated against DuPont WAVE software. The 14.4 kWp configuration exhibits enhanced energy reliability with feedwater preheating to 40 °C, recovery rates of 60%, and specific energy consumption as low as 1.06 kWh/m³. Comparative evaluations solar PV and solar PVT RO demonstrate that the incorporation of PVT preheating with dual-stage RO markedly decreases operating pressures and enhances water quality. Analysis indicated that the smaller 5.2 kWp system, despite its reduced initial expenditure, yields water at a higher Levelized Cost of Water (LCOW) of USD 1.25/m³. The larger 14.4 kWp system on the other hand attained a lower LCOW of USD 0.75/m³, illustrating the benefits of economies of scale in hybrid PVT-RO configurations. This work demonstrates the viability of scalable solar-driven water purification systems for offgrid rural Lesotho, with implications for sustainable development and climate adaptation, providing a viable approach to furthering Sustainable Development Goals 6 (Clean Water and Sanitation) and 7 (Affordable and Clean Energy) in Lesotho.en