Design and Techno-Economic Optimisation of a Hybrid Stand-Alone Microgrid for Sustainable Artisanal and Small-Scale Mining Operations in Zimbabwe

Abstract

Artisanal and Small-Scale Mining (ASM) operations in Zimbabwe face severe operational constraints due to grid instability and high diesel fuel inflation. This study presents the design and techno-economic optimization of an off-grid, hybrid stand-alone microgrid tailored to the volatile, high-inertia load profile of a remote gold-processing plant with a ~63 kW peak surge. A multi-variable metaheuristic Particle Swarm Optimization (PSO) model was built in MATLAB and simulated across an empirical 8,760-hour dataset utilizing field-measured mine loads and real solar Global Horizontal Irradiance (GHI) from the NASA POWER API. The optimization solver achieved global convergence at a minimum lifecycle Net Present Cost (NPC) of $303,647.13 USD over a 20-year project lifetime. The mathematically optimal configuration consists of a 215.12 kW Solar PV array, a 402.58 kWh Lithium Iron Phosphate (LiFePO₄) battery storage bank, and a downsized 10.73 kW backup diesel generator, coupled with a robust 150 kW central inverter to absorb heavy motor startup transients. The optimized system yields an exceptional Levelized Cost of Energy (LCOE) of $0.0952 per kWh while maintaining a renewable energy fraction above 90%. A 3D sensitivity surface analysis mapping 121 macroeconomic scenarios confirms that this decoupled architecture effectively insulates remote operators from localized fossil-fuel price shocks. Ultimately, the results prove that transitioning to optimized high-renewable microgrids provides a technically resilient, environmentally sustainable, and commercially superior alternative to conventional energy baselines in Sub-Saharan African mining sectors.