Design and lifetime cost optimization of ship energy systems including weather-driven speed profile variability

This study presents a framework for designing and optimizing ship energy systems including weather-driven speed variability and navigation safety constraints. Navigation risks including resonance, surf-riding, and successive high-wave impacts, are calculated using five years of hourly weather data. Random speed variations (up to ±5%) are applied to a baseline speed profile to capture operational uncertainty, and safety-based speed reductions (up to 40%) are applied when required. Course changes are excluded. Treating navigation risks as constraints, operating profiles are generated for different weather conditions. For a conceptually retrofitted cargo ship, hydrogen fuel cell and battery capacities, and their power distribution, are optimized for each operating profile to minimize lifetime energy system cost and assess the effects of weather-induced power variation. Results show that speed and weather variability can significantly change power demand, requiring fuel cell capacities between 700 and 1500 kW. The most common configuration is a 1200 kW fuel cell system with 180 kWh of battery capacity, covering 39% of laden profiles, while full power coverage requires 1500 kW. Lifetime cost outcomes exhibit a 5th–95th percentile spread of −10.3% to +11.1% relative to mean cost. The results demonstrate the significant influence of weather variability on system sizing and cost. • Hydrogen fuel cell-battery system sizing under weather-driven speed variability. • MINLP lifetime cost optimization using power profiles based on 5-year metocean data. • Model includes IMO constraints for surf-riding, resonance, successive-wave risks. • Ship speed reductions up to 40% reduce navigation risks from 25.25% to 6.38%. • Weather variability causes −10% to +11% cost deviation from mean lifetime NPV.