It has been known for over 150 years that vessels with wings – or foils – in the bow can be partly or solely propelled by wave energy. The foils generate lift when the vessel is moving up and down in waves, and the lift typically has a forward thrust component larger than the drag.
Put simply, wave power is directly converted into propulsive power.
A vessel in waves experiences additional resistance compared to calm-water operation. For wave lengths similar to the hull length, this additional resistance will be amplified due to resonance, implying large heave and pitch motions. Wavefoil’s retractable bow foils dampen these motions so that the additional resistance decreases.
So how much fuel can you save? That depends on the ship, its speed, the foil size and location and the wave conditions. For a 100 m long ship operating in a wave-rich area, with constant brake power equivalent to a calm-water speed of 14 knots, research shows that an average fuel saving on the order of 20% can be achieved. Lower brake power gives higher percentage fuel saving.
Fuel savings are not the only benefit of bow foils. Increased comfort, reduced vibrations, less spray, increased operability and the ability to maintain higher speeds in waves for a given power are some other perspectives.
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