Multi-criteria Design of a Mini-grid System: a Case Study of the Tsumkwe Plant in Namibia

The Tsumkwe mini-grid in Namibia, initially converted from diesel-only to a hybrid system in 2005, received an upgrade in 2015 with an additional PV and lead BESS. Despite these improvements, the plant now faces operational issues like high diesel consumption, outdated control systems, and frequent outages, prompting the need for a second system upgrade. This research investigates whether a multi-criteria design approach—focusing on optimization objectives, control strategies, load growth, and proactive maintenance—can improve the system's sustainability and resilience using Tsumkwe plant mini-grid as a case study. Analysis revealed that excessive diesel uses stems from the generator's dual role in powering the system and charging weak batteries, exacerbated by growing demand and insufficient PV charging during daylight hours. Using HOMER simulations, the study assessed the balance between renewable energy generation, storage, and diesel use to optimize costs. The models incorporated key factors like PV and battery sizing, advanced energy management, and scalability for future loads. The results demonstrate that optimized mini-grid’s PV and battery configurations, combined with intelligent system utilization strategies, can significantly reduce diesel reliance and enhance system efficiency. These findings validate a structured, multi-criteria design approach, providing practical insights for mini-grid designers and operators to drive sustainable energy solutions.