Optimal Sizing and Operations of a Hydrogen-Based Multi-Energy Port System with Market Participation and Gas Grid Integration

This work addresses the optimal sizing and operations of a hydrogen-based multi-energy system in the Port of Livorno, Italy, aimed at decarbonizing maritime activities. The system includes renewable generation, batteries, electrolyzers, and hydrogen storage. Hydrogen is used both for fueling ships and for injection into the nearby gas grid, complying with hydrogen blending limits. A simulation-based optimization framework is developed to solve the plant sizing problem: the outer level recursively minimizes the Net Present Cost via surrogate optimization, while the inner level optimally schedules daily operations by solving a mixed-integer linear programming problem. The framework accounts for markets participation (electricity, gas, environmental) and technical constraints. The feasibility of the optimized hydrogen injection strategy is assessed through a steady-state isothermal fluid-dynamic model. The system is sized based on the Italian regulation assuming a 2% vol hydrogen injection limit, while operational scenarios with injection limits ranging from 2% to 20% vol are analyzed. Results show that increasing the blending limit from 2% to 20% enables a 9% rise in renewable hydrogen utilization and reduces the Levelized Cost of Hydrogen from 3.82 €/kg to 3.49 €/kg.