Evaluation of Hydraulic Losses and Photovoltaic Performance in the Design of Solar-Powered Irrigation and Domestic Water Supply Systems for Rural Rwanda

Bugesera, a historically drought-prone region in Rwanda, is undergoing transformation through investment in modern irrigation and sustainable agricultural practices. However, extending the national electrical grid to numerous dispersed smallholder farms poses a major challenge. The persistent water scarcity and rising conventional energy costs necessitate the development of innovative and sustainable solutions. This study investigates the use of photovoltaic (PV) pumping systems as a green energy alternative for off-grid rural areas, supporting both agricultural irrigation and domestic water supply. A model system serving five one-hectare market-gardening plots and 25 inhabitants was analyzed, with a total daily water demand of 300.75 m3/day. A comprehensive technical and economic evaluation was conducted using MATLAB to optimize the system design, including PV array sizing and storage capacity, to ensure reliable operation under defined water and energy demands. A critical component of the analysis was the optimization of the piping network to balance hydrodynamic performance, energy consumption, and overall system cost. For a water requirement of 300.75 m3/day, the optimal PV system consisted of 12 panels, providing a cost-effective balance between energy generation and pumping demand. The results show a rapid decrease in total system cost as the pipe diameter increases from 0.15 to 0.30 m, primarily due to reduced friction losses that lower the total dynamic head and significantly decrease the required PV array size, which dominates the system cost. An optimal diameter of approximately 0.30 m was identified, beyond which further increases yield diminishing cost reductions as the total dynamic head becomes governed mainly by static head rather than hydraulic losses. This integrated technical and economic approach provides a practical framework for designing sustainable, cost-effective solar-powered irrigation and domestic water systems tailored to off-grid smallholder farmers in drought-prone regions.