Net fuel saving from an air-layer or micro-bubble lubrication system, netting out the compressor-power penalty.
Formula
$$ \Delta P_\text{gross} = P_\text{ME} \cdot f_\text{fric} \cdot f_\text{cov} \cdot r $$$$ \Delta P_\text{net} = \Delta P_\text{gross} - P_\text{comp} $$Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\Delta P_\text{gross}$ | Gross ME power saved from reduced hull friction | kW | result |
| $\Delta P_\text{net}$ | Net saving after compressor cost | kW | result |
| $P_\text{ME}$ | Main-engine delivered power at reference load | kW | EEDI reference point |
| $f_\text{fric}$ | Share of total resistance that is frictional | fraction | tanker 0.60–0.70, bulker 0.65–0.75, container 0.45–0.55 |
| $f_\text{cov}$ | Wetted-surface fraction covered by air layer | fraction | flat-bottom area / total wetted surface |
| $r$ | Drag reduction on the covered area | fraction | MALS 5–10 %, micro-bubble 3–6 % |
| $P_\text{comp}$ | Compressor power demand | kW | 1–3 % of $P_\text{ME}$ typical |
EEDI treats air lubrication as a Category-C innovative technology (reduces propulsion power). The credit is subtracted from the EEDI numerator, with an availability factor $f_{\text{eff}}$ covering the fraction of operating time the system is active.
Sources
- Mitsubishi Heavy Industries - MALS Air Lubrication System.
- Silverstream Technologies - Air Lubrication System.
- IMO Resolution MEPC.1/Circ.815 - innovative energy-efficient technologies.