Reliability-Driven Techno-Economic Assessment of an Off-Grid PV–Battery System for Small-Scale Irrigation Pumping in Lafia, Nigeria

Reliable electricity supply is essential for small-scale irrigation pumping systems that operate within narrow and time-sensitive windows. In Lafia, Nigeria, persistent grid unreliability has sustained heavy reliance on diesel generators for irrigation, exposing operators to high operating costs, fuel price volatility, and frequent service interruptions. This study presents a reliability-driven techno-economic assessment of an off-grid photovoltaic (PV)–battery system with diesel backup for small-scale irrigation pumping under local operating conditions. A representative irrigation load of 10 kWh/day, characterized by fixed morning (06:00–09:00) and evening (17:00–19:00) pumping windows, is evaluated under a zerounmet-load reliability constraint and benchmarked against a diesel-only generation alternative. System performance is assessed using technical and economic indicators including load served, renewable energy fraction, battery operation, generator runtime, fuel consumption, net present cost (NPC), and levelized cost of energy (LCOE). Results show that the hybrid PV–battery system fully serves the annual irrigation demand (≈3,650 kWh/yr) with near-zero unmet load and a renewable fraction of approximately 78%. Annual PV generation of about 4,750 kWh reduces generator operation to roughly 220 h/yr and fuel consumption to approximately 300 L/yr, compared with 1,460 h/yr and 1,460 L/yr for diesel-only supply. Over a 10-year lifetime, the hybrid system achieves a lower NPC (≈₦10.8 million) and LCOE (≈₦190/kWh) than diesel-only operation (≈₦18.6 million and ≈₦330/kWh). The findings demonstrate that reliability-oriented PV–battery systems offer a technically robust and economically viable alternative to diesel-only generation for small-scale irrigation in fuel-dependent off-grid environments.