Hydraulic Audit and Techno-economic Comparison of Photovoltaic and Diesel Pumping for Drip Irrigation in the Maradi Valley, Niger
Moumouni Guero Mohamed *
Department of Mechanical and Energy Engineering, Polytech Maradi, Dan Dicko Dankoulodo University of Maradi, P.O. Box: 465, Maradi, Niger.
Aboubacar Sidikou Mazadou Garba
Department of Physics, Faculty of Sciences and Technics, Dan Dicko Dankoulodo University of Maradi, Maradi, Niger.
Soupiyanou Abdou Moussa
Department of Physics, Faculty of Sciences and Technics, Dan Dicko Dankoulodo University of Maradi, Maradi, Niger.
*Author to whom correspondence should be addressed.
Abstract
Aims: To audit an analytically sized, battery-backed photovoltaic (PV) drip-irrigation design for 1 ha in relation to borehole hydraulics and documented costs, and to compare it with direct-coupled PV and diesel pumping.
Study Design: A design audit and numerical simulation study without field measurements.
Place and Duration of Study: Djirataoua irrigation perimeter, Maradi, Niger (13.41° N, 7.14° E); reference design of January 2026, analysed in 2026.
Methodology: An hourly model coupled FAO-56 crop water demand, PV output, a variable-speed submersible pump and tank and battery balances. Options were compared by the levelised cost of water (LCOW) and volumetric coverage, with Monte Carlo, Sobol and multi-objective analyses. The model was checked against the original PVsyst outputs but not validated with field data.
Results: The main error was hydraulic: the design flow (23 m³ h⁻¹) was more than three times the borehole yield (7 m³ h⁻¹), the head was underestimated (20 instead of 25.4 m) and pump power was overestimated nearly threefold. A direct-coupled 3 kWp array with a 50 m³ tank met about 98 % of the seasonal demand; the January–February shortfall was set by the borehole, not by irradiation. At datasheet-based prices, direct PV, battery-backed PV and diesel cost 194, 201 and 190 FCFA m⁻³ (West African CFA franc): the battery did not reduce costs in the tested configurations, and solar was cheaper than diesel in about half of the Monte Carlo runs, depending mainly on the pump-set price. The reported internal rate of return (6.15) was an annuity factor.
Conclusion: Such systems should be sized from a pumping test and the peak-day demand. The solar–diesel choice depends more on local pump-set prices than on sunshine, and groundwater sustainability must be assessed before any extension.
Keywords: Solar water pumping, drip irrigation, borehole yield, levelised cost of water, crop water demand, sensitivity analysis, Sahel, Niger