Rotating-cylinder wind-assist thrust estimation. Real systems publish route-integrated fuel savings rather than spot-power numbers; use this for back-of-envelope sizing.
Formula
$$ P_\text{gen} = C_L \cdot \tfrac{1}{2} \rho_\text{air} V^2 A \cdot V_\text{ship} $$
$$ P_\text{net} = P_\text{gen} \cdot f_\text{useful} - N \cdot P_\text{drive} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $P_\text{gen}$ | Gross thrust power from all rotors | kW | result |
| $P_\text{net}$ | Net main-engine saving after rotor-drive cost | kW | result |
| $C_L$ | Lift coefficient for rotating cylinder at spin ratio ~3 | - | ≈ 5–8 empirical |
| $\rho_\text{air}$ | Air density | kg / m³ | 1.225 |
| $V$ | Apparent wind speed | m / s | anemometer |
| $A$ | Total rotor projected area ($N \cdot h \cdot d$) | m² | rotor geometry |
| $V_\text{ship}$ | Ship speed | m / s | operating profile |
| $f_\text{useful}$ | Share of voyage hours with useful cross-wind | fraction | route climatology |
| $N$ | Number of rotors | - | installation |
| $P_\text{drive}$ | Drive-motor power per rotor | kW | rotor-maker data |
Sources
- Norsepower - Rotor Sail in-service results.
- Anemoi Marine Technologies - Rotor Sails.
- IMO Resolution MEPC.1/Circ.815 - innovative energy-efficient technologies.