Community Research and Development Information Service - CORDIS

Modelling techniques for wave energy extraction devices

The Islay wave power system consists of a 3-stage energy conversion cycle. The stages are: oscillating water column (hydraulic to pneumatic), Wells turbine (pneumatic to mechanical), induction generator (mechanical to electrical). Each medium containing energy can be modelled in general terms as a source generating effort, e(t) which causes a flow, f(t) into a connected system. In this notation e(t).f(t) gives the instantaneous power transfer from the source to the system. For each medium variables can be assigned to effort and flow.
This common approach to the modelling of each medium allows analogous models to be drawn up. Transformation of a network of interconnected systems consisting of different media to a single equivalent model simplifies analysis and enhances understanding of the behaviour of the whole network. This approach is particularly useful for the analysis of system dynamic behaviour.
The concept is applied to an onshore wave energy extraction device.

The model as presented possesses many drawbacks, particularly in the incorporation of several nonlinear elements which defy analytical solution. These nonlinear representations are unfortunately unavoidable in any treatment of this system. Thus the concept is, in this regard, at no greater disadvantage than other methods.

The method does, however, possess the important characteristic that it allows the various energy conversion elements to be represented according to a small set of parameters all sharing a common base. This allows the interactions between the various stages to be analysis systematically while contributing to the understanding of the performance of the system as a whole.

Reported by

Queen's University of Belfast
BT7 1NN Belfast
United Kingdom
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