A loading model for an OWC caisson based upon large-scale measurements

Abstract

A loading model for an OWC caisson based upon large-scale measurements', Coastal Engineering. AbstractWave energy is one of the most promising marine energy resources in terms of the scale of the resource, but there remains little technology convergence and costs remain at nearprohibitive levels. Of many wave energy converter (WEC) concepts that have been developed over the years, the oscillating water column (OWC) stands out for its simplicity and low maintenance cost. Quite some experience of actual OWC operation has been gained to date from small, stand-alone pilot schemes. One way to reduce costs is the integration of an OWC-WEC into a breakwater, enabling some degree of cost-sharing between energy and harbour or coastal defence functions. A major problem encountered during the design of an OWC-WEC scheme remains the uncertainty in the wave loads, with their critical influence upon capital cost. A model to estimate forces acting on an OWC chamber in a caisson breakwater is proposed in this paper. Horizontal forces on the front (curtain) wall and the rear (in-chamber) wall are predicted. In addition, and unlike a conventional caisson breakwater, vertical forces acting on the caisson chamber ceiling will have considerable effect on sliding and overturning characteristics of the breakwater structure. The proposed model enables the prediction of chamber pressures which in turn influence the chamber vertical force. The new model has been compared with results from large scale physical model measurements from tests carried out in the very large wave channel, GWK, in Hannover (Germany). Forces under both regular and irregular wave conditions were measured. The comparisons show that the model fits well with the test results to the factor of 1 ± 0.2 for the regular wave cases and to the factor of 0.8 ± 0.2 for irregular wave cases. This model will enable the structural design of caisson breakwater-integrated OWCs to be approached with uncertainties reduced to those comparable with conventional caisson design.

Front Wall and In-Chamber Impact Loads on a Breakwater-Integrated Oscillating Water Column

“…The other two chambers were installed with the same PTO arrangement and setting to ensure that they are hydraulically identical. For more detail on the experimental set-up, please see Pawitan et al, (2019) and Viviano et al, (2016).…”

The Influence of the Chamber Configuration on the Hydrodynamic Efficiency of Oscillating Water Column Devices

“…This reduction in the efficiency is explained by the fact that the energy transfer due to the wave motion over small periods is reduced when the front barriers are greater in thickness. However, in a real scenario, during severe storm events, or during times of high water levels, the front barrier is subjected to high loads, due to direct wave action [36][37][38][39], and a slender front wall cannot offer protection to the whole system, as occurred at the MWEP [12]. Therefore, special consideration should be given to this structural aspect.…”

A Numerical Study on Hydrodynamic Energy Conversions of OWC-WEC with the Linear Decomposition Method under Irregular Waves

“…The oscillating-water-column type WEC (OWC-WEC) is one of the terminator type WECs, which has been widely used due to its simplicity: the only moving part of the power take-off (PTO) system is the rotor of a turbine, located above the water level, rotating at a relatively high velocity and directly driving a conventional electrical generator [4,5]. Additionally, there is an effort to integrate the OWC-WEC with the conventional breakwater to enhance the economic feasibility of the device [6][7][8][9][10].…”