Design and optimization of reliable off-grid solar PV–battery mini-grids for trading centers in Uganda

Reliable electrification of rural trading centres in Sub-Saharan Africa requires photovoltaic mini-grid sizing approaches. This study presents a reliability-constrained design framework for off-grid PV-battery mini-grids based on hourly energy-balance simulation using worst-month solar conditions and autonomy-based storage sizing. A representative Ugandan trading-centre load profile of 132.1 kWh/day was used to evaluate six PV–battery configurations, combining lead-acid and lithium-ion storage technologies with autonomy durations of 2–4 days under conservative peak sun hour conditions of 4.0–4.5 h/day. The resulting system capacities ranged from 40 to 48 kWp for photovoltaic generation and 280–870 kWh for battery storage, depending on technology and autonomy level. State-of-charge simulations confirmed stable storage operation above minimum thresholds during extended low-irradiance periods, while reliability assessment using loss-of-load probability yielded values between 0.003 and 0.028 for prioritised loads. Lifecycle economic evaluation using levelised cost of energy indicated improved reliability–cost performance for lithium-ion configurations relative to lead-acid alternatives. Among the evaluated scenarios, a three-day lithium-ion storage configuration (42 kWp PV, 420 kWh battery) provides the most balanced solution for reliable trading-centre electrification under worst-month design conditions. The framework guides reliable tropical off-grid mini-grid design by linking load, storage and solar-resource constraints.