Oscillating Water Column based wave energy plants built so far have experienced a low efficiency in the conversion of the bidirectional oscillating flow. A new concept is considered here, the LeanCon Wave Energy Converter (WEC), that unifies the flow direction by use of non-return valves, into a unidirectional flow, making the use of more efficient air turbines possible. Hereby, a more steady flow is also obtained.
The general objective of this note is to examine, the power take off (PTO) efficiency under irregular wave conditions, for WECs with flow redirection. Final practical aim is to identify a method that allows the choice of the optimal power generation capacity for which the device should be designed, when subjected to any given wave climate.
The analysis is based on the experimental results of existing tests carried out in the 3D deep water wave tank at Aalborg University, Denmark.
First, the power measured at the modelled PTO is compared with the available incident wave power in order to examine the overall system response in a scale-independent manner. Then, the power production density function is fitted to a simplified shape, whose parameters are related to the tested sea state conditions (wave period, wave height). Average performance and stochastic variability is thus obtained for any sea state and therefore also for the annual wave climate of interest.
An example application of a LeanCon unit is carried out for a location off-shore Cagliari (Italy).
Conclusions provide economic criteria for estimating the optimal value of power for which the PTO should be designed.