The electrification of port infrastructure is emerging as a potential industry standard, driven by stringent emission regulations and the push for decarbonized maritime corridors. Technologies such as On-Shore Power Supply (OPS), battery-powered cargo equipment, and the retrofitting of diesel systems are pivotal for enhancing energy efficiency and achieving greenhouse gas (GHG) reduction targets. However, implementation faces fundamental challenges: ensuring a secure energy supply, mitigating grid stability issues, and maintaining cost competitiveness in volatile markets. These obstacles are exacerbated by port grid characteristics, notably concentrated demand nodes, constrained feeder capacity, and variable, peak-driven load profiles that often exceed existing infrastructure limits.

To address these constraints, ports are adopting microgrid architectures that integrate endogenous Renewable Energy Sources (RES), particularly solar photovoltaic (PV) generation. In this context, Battery Energy Storage Systems (BESS) are recognized as key enablers for the transition toward zero-emission ports. BESS provide the flexibility to mitigate RES intermittency and decouple local generation from variable port demands, potentially deferring costly grid investments by alleviating congestion in weak or isolated networks. Efficient BESS utilization requires an integrated sizing and location strategy that considers future RES integration and the non-linear nature of evolving load demands.

This work proposes a grid-aware sizing optimization framework for the Port of Sines, Portugal, a major European deep-water port. The objective is to identify the optimal BESS capacity (kWh) and power rating (kW) that maximizes PV self-consumption under net-metering schemes and meets future OPS demands while minimizing the Levelized Cost of Electricity (LCOE). The methodology employs a simulation-based optimization approach integrated into a professional power system analysis environment. It features an energy management system (EMS) that performs a grid search over predefined BESS configurations, executing successive quasi-dynamic power flow analyses in DIgSILENT PowerFactory over a representative year using real-world operational datasets.

The results validate that the proposed sizing ensures operational stability, preventing voltage violations and component overloading during high-power OPS events when multiple vessels are berthed simultaneously. Furthermore, the study provides a technical evaluation of the impact of 15-minute data resolution versus the hourly standard. Findings demonstrate that high-resolution data is critical to capture short-duration peak events and PV fluctuations, effectively preventing renewable energy curtailment and ensuring long-term State of Charge (SOC) sustainability within the port microgrid. This framework offers a scalable decision-support tool for port authorities to balance environmental goals with technical and economic feasibility.