A ship's hull resistance grows roughly with the square of speed, so the power its engine must deliver grows with speed cubed — the same reason cruising slightly slower saves fuel disproportionately. Each fuel candidate stores a different amount of chemical energy per litre (its energy density), so the same tank volume gives very different range depending which fuel is loaded. Burning that fuel also releases a different amount of greenhouse gas per unit of energy (its well-to-wake carbon intensity), and IMO's 2025 GHG Fuel Intensity framework requires that intensity to fall on a schedule toward 2050. Raising the "green production share" slider blends in renewably-produced fuel (e-ammonia, e-methanol, bio-LNG, biofuel-blended HFO), which cuts the carbon intensity without changing the energy density.
power(v) ∝ v³
range = tank_energy / (k · v²)
intensity = grey_intensity · (1 − green%) + green_intensity · green%
compliant = intensity ≤ IMO_target(year)
- Fuel type — sets energy density (MJ/L, controls range) and base carbon intensity (grey production).
- Green production share — how much of that fuel comes from a renewable pathway; ammonia and methanol can reach near-zero combustion carbon when fully green.
- IMO target year — moves the regulatory bar; it tightens sharply after 2030 toward net-zero by 2050.
- Cruising speed — higher speed shrinks range faster than it grows daily distance, because power scales with the cube of speed.
- Tank volume — physical space onboard; low-energy-density fuels like ammonia need much bigger tanks for the same range.
Real-world relevance: this speed-cubed / energy-density trade-off is exactly why the shipping industry's 2050 net-zero pathway leans on both switching molecules (LNG → ammonia/methanol) and slow-steaming, not either alone.