Optimization of a Brownfield Microgrid Comprising a Diesel Power Plant, Solar Power Plant, and Energy Storage System to Support the Diesel Power Bunaken Island: Integration of HOMER Pro and PLS-SEM

Abstract

Bunaken Island operates a diesel–PV–BESS hybrid microgrid; however, diesel dependence remains substantial because of degraded PV capacity, limited energy storage, and a temporal mismatch between solar generation and evening peak demand. This study evaluated a brownfield-based dedieselization strategy using a sequential explanatory mixed-methods approach. Four scenarios were simulated using HOMER Pro: baseline, dispatch optimization, PV revitalization, and 100% renewable dedieselization. The simulation outputs were subsequently integrated with Partial Least Squares Structural Equation Modeling (PLS-SEM) to examine the relationships among economic performance, technical performance, environmental and social factors, and microgrid optimization. Under the baseline assumptions, revitalizing the PV system to 287 kWp while retaining the existing 540 kWh BESS resulted in a net present cost (NPC) of US$8.386 million and a levelized cost of energy (LCOE) of US$0.327/kWh, compared with US$11.261 million and US$0.440/kWh, respectively, under the baseline scenario. Renewable energy penetration increased from 4.66% to 24.30%, accompanied by an annual diesel fuel reduction of approximately 116,000 liters. A 100% renewable configuration was technically feasible with 2,000 kWp of PV capacity and a 6,480 kWh BESS but required approximately US$4.52 million in capital expenditure. The PLS-SEM model yielded an R² value of 0.998 for microgrid optimization; economic performance was the strongest determinant (f² = 90.428), while technical performance contributed primarily through its effect on economic performance. The findings supported a phased optimize–modernize–decarbonize pathway for energy transitions in small-island and conservation-area microgrids.