Wing Sail / Kite Wind Assist

Rigid wing sails (bound to the ship) or towing kites (free-flying on a long tether) generate direct thrust from ambient wind. Different operating envelopes than Flettner rotors - wing sails like quartering winds, kites like downwind trades.

DesignWind assist

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

P = C_L \cdot \tfrac{1}{2} \rho_\text{air} V^2 A \cdot V_\text{ship} \cdot f_\text{useful}

Symbol	Meaning	Unit
$P$	Time-average thrust power contributed to the ship	kW
$C_L$	Effective lift coefficient - wing 1.0–1.4, kite 0.8 time-averaged
$\rho_\text{air}$	Air density	kg / m³
$V$	Apparent wind speed	m / s
$A$	Sail or kite projected area	m²
$V_\text{ship}$	Ship speed	m / s
$f_\text{useful}$	Share of voyage hours with useful wind angle	fraction

Source: Oceanbird Wallenius - wind-powered RoRo concept; SkySails Marine - towing kite systems; IMO Resolution MEPC.1/Circ.815 - innovative energy-efficient technologies

In short

Fuel saving from rigid wing sails or towing kites for merchant-ship wind assist.

Learn the theory Decarbonization Technologies for Ships