Operational Strategies for <i>CII</i> Under Short Voyages: Hybrid Denominator Correction and CPP Mode Optimization

This study addresses structural distortions in the IMO Carbon Intensity Indicator (<i>CII</i>) for short-voyage training vessels and proposes corrective strategies combining denominator adjustments with controllable pitch propeller (CPP) mode optimization. Using 2024 operational data from a training ship, we computed monthly and annual <i>CII</i> values, identifying significant inflation when time-at-sea fractions are low due to extensive port stays. Two correction methods were evaluated: a hybrid denominator approach converting port-stay <i>CO</i>₂ to equivalent distance, and a Braidotti functional correction. The CPP operating maps for combination and fixed modes revealed a crossover point at approximately 12 kn (~50% engine load), where the combination mode shows superior efficiency at low speeds and the fixed mode at higher speeds. The hybrid correction effectively stabilized <i>CII</i> values across varying operational conditions, while the speed-band CPP optimization provided additional reductions. Results demonstrate that combining optimized CPP mode selection with hybrid <i>CII</i> correction achieves compliance with required standards, attaining a B rating. The integrated framework offers practical solutions for <i>CII</i> management in short-voyage operations, addressing regulatory fairness while improving operational efficiency for training vessels and similar ship types.