The Oscillating Water Column (OWC) device is one of many available technologies for generating electricity from water waves. It is a caisson-like structure, which houses a water column in an enclosed chamber with an inlet at the bottom. Waves enter the device, exciting the water column. The trapped air above is forced out through a turbine, generating electricity. The technology is relatively young compared to other sources of renewable energy, such as solar or wind energy. This makes the produced energy expensive, expressed in the Levelised Cost of Energy (LCOE). Integrating devices into breakwaters already resulted in a large reduction of the costs, as they now can be shared. During the design of such devices, main attention is given to the geometrical design. This should be based on local wave conditions to ensure the largest energy production. Having the eigenperiod match with the incident wave period enhances the resonance effect in the chamber. This research explores the potential to reduce the costs of OWC devices integrated in breakwaters through means of structural optimisation. The structural are built quite robust, leaving the thought there is room for improvement. The device in Civitavecchia, Italy was used as a case study. A new method was adopted to investigate the potential. A numerical model was constructed in STAR-CCM+, including both a fluid domain and a solid domain. The two are one-way coupled, from water to structure. The exerted wave pressures are mapped on the structure directly, resulting in a stress state in the OWC structure. Due to the transient nature of the simulations, all results are available through time. It was found, the main walls shaping the OWC device could be built with 35% less material. Variants of the original geometry were tested as well to see how these influence the results. Furthermore, the structural behaviour was investigated. Clear trends were found in position and timing of governing load combinations in the different walls. One of the most important findings was that the governing load case always was in the direction of the transverse width. The walls were found to behave more like beams in this direction. The bending moments could therefore easily be calculated using standard beam equations and the net horizontal pressure on the wall as load. This leads to the beginning of a new simplified design method where the full numerical structural analysis is not required anymore.

The purpose of this report is to design a wave energy converter, in particular a U-oscillating water column (U-OWC), to maximize energy conversion in the low wave energy environment of Gwadar, Pakistan. At present Pakistan’s 1000km coastline is largely undeveloped and the county is devoid of any wave energy harnessing devices or studies. However, recent years have seen an influx of Chinese investment being made under the China-Pakistan economic corridor agreement, which is stimulus for the near future construction of a large rubble mound breakwater to shelter an assistance vessel basin in the city of Gwadar. Typically, a WEC is not feasible in low incident wave energy environments because the economic return from minimal energy generation cannot offset the capital cost of the structure. However, the opportunity in Gwadar is unique in the sense that a substantial investment is already envisaged for the creation of a breakwater. Therefore, it is worth investigating if re-designing this structure with vertical caissons embedded with U-OWC chambers is feasible. In this way, the structure can fulfill the dual role of sheltering the assistance vessel basin against wave attack, and produce renewable energy over its design life. To assist with this task, existing data and methods available in literature along with numerical codes have been utilized. A 10 year SWAN hindcast has been performed, the result of which have been condensed into 60 representative design sea-states on the basis of which the U-OWC chamber geometry and turbine configuration have been optimized. This was achieved by employing a random sampling technique to determine which combinations produce the most power and by identifying the ideal turbine operating revolutions for each sea-state. Next, the approximate cost of the caisson breakwater integrated with U-OWC chambers is calculated and compared against the currently proposed rubble mound design. It is expected that despite an attempt to maximize the energy generation by the device, its levelized cost of energy will be high, given the low wave energy in the region. Nevertheless, if the design proves cheaper than its rubble mound counterpart, it goes to show that wave energy converter can be deployed in low energy environments provided an opportunity exists where they can be integrated into proposed marine structures. This will be an important finding, considering that the majority of the global coastline is subjected to moderate to low incident wave energy, and neglected from WEC deployment considerations.