Numerical Study of a Novel Pneumatic Support Spring for Efficient Wave Energy Extraction

Ocean wave has been a potentially ideal kinetic energy source for long term and continuous environmental observation operations. The study of power take-off technologies (PTO) can be back tracked as early as last century. So far, most successful implementations of wave energy converters are of large scale or in permanent constructs, as large size is often beneficial to the efficient collection and conversion of the wave energy, where energy storage or plainly large number of extractors can compensate the low frequency and high amplitude nature of the incident wave. As for the more portable ocean observation operations, the small size of the device is usually too small compared to the wave length to utilize terminator or line absorber, leaving point absorber the only choice, and the efficiency of the conversion is critically dependent upon the oscillation amplitude and frequency of the PTO device on board. So far, the reported work has shown the approaches including the resonance design, direct conversion, etc. Yet, difficulties still present in achieving high oscillation amplitudes in the portable PTO. Facing the challenges, we propose a novel pneumatic support spring to replace the traditional mechanical spring in the PTO, to achieve more efficient wave energy conversion. Mathematical models and numerical solutions using Simulink have been developed. Initial results have shown that the PTO with the proposed pneumatic spring device can achieve higher vibration amplitude compared to the traditional one. And the output electric power can be improved.