Researchers at Cranfield University are working on a new form of wave devouring propulsion (WDP) that could power larger ships and help reduce the use of fossil fuels in the maritime industry, in addition to its impact on the marine world. This is because a wave devouring propulsion system (WDPS) operates at a lower frequency compared with traditional ship propellors, reducing underwater noise and the adverse effects of this on marine life. WDP isn’t a new technology. The original concept actually dates back to the 1900s when – taking inspiration from the power of a whale’s fins – researchers discovered and demonstrated the ability to generate thrust from surrounding flows.
“The ocean waves have a tremendous amount of energy. As wave propulsion devices, foils can use the kinetic energy of the waves to achieve self-propulsion without fuel,” says Dr Liang Yang, a lecturer in marine renewable energy solutions at Cranfield University. “An oscillating foil can extract wave energy and convert it to wave propulsion, which could potentially replace traditional propellers, enhance ship stability by significantly decreasing pitch and heave motion, and reduce ship resistance against waves,” he explains.
Submerged foils can be used in three ways to generate thrust – passive, semi-passive/active, and active. In passive mode, the flapping motion is entirely flow-induced, with foils often accompanied by springs to ensure the equilibrium position is restored, Yang explains. But while providing the least disturbance to the flow, their efficiency is the lowest of the options.