Techno-economic analysis of a hybrid wave-solar-wind-battery microgrid: A case study for Koh Tao Island, Thailand

Remote tropical islands face persistent energy-planning challenges associated with diesel dependence, fuel-price volatility, limited developable land, tourism-sensitive coastlines, and the need for reliable low-carbon electricity. This study develops a deployment-aware techno-economic framework to evaluate the integration of onshore wave energy converters (WECs) into a hybrid photovoltaic (PV)-wind turbine (WT)-battery energy storage system (BESS)-diesel generator (DG) microgrid for Koh Tao, Thailand. Fifteen hybrid microgrid architectures were assessed using measured 2024 electricity demand, site-characterized solar, wind, and wave resources, an hourly wave-to-power model, HOMER Pro optimization, four deployment tiers, and full-factorial sensitivity analysis. The diesel-only baseline produced an LCOE of USD 0.2786/kWh, annual diesel consumption of 13.08 ML/yr, and CO 2 emissions of 34.29 kt/yr. The unconstrained Tier-2 optimum achieved an LCOE of USD 0.1773/kWh and a Renewable Fraction of 72.0 %, while the preferred Tier-3b deployment benchmark achieved USD 0.1775/kWh and 71.5 %, respectively, with diesel consumption of 3.88 ML/yr and CO 2 emissions of 10.31 kt/yr. These values correspond to approximately 70 % reductions in diesel consumption and CO 2 emissions relative to the baseline. In contrast, the land-constrained Tier-3a scenario achieved only 11.5 % renewable penetration at USD 0.2591/kWh, indicating that terrestrial renewable siting is a more influential physical constraint for Koh Tao than the modeled WEC infrastructure limit. Sensitivity analysis showed that economic performance is particularly responsive to diesel-generation costs and financing conditions. The proposed four-tier framework provides a transferable decision-support approach for wave-inclusive island microgrid planning and contributes to progress toward SDG 7 and SDG 13.