Hydraulic and Structural Assessment of a Rubble-Mound Breakwater with a Hybrid Wave Energy Converter

Seaports’ breakwaters serve as important infrastructures capable of sheltering ships, facilities, and harbour personnel from severe wave climate. Given their exposure to ocean waves and port authorities’ increasing awareness towards sustainability, it is important to develop and assess wave energy conversion technologies suitable of being integrated into seaport breakwaters. To fulfil this goal whilst ensuring adequate sheltering conditions, this paper describes the performance and stability analysis of the armour layer and toe berm of a 1/50 geometric scale model of the north breakwater extension project, intended for the Port of Leixões, with an integrated hybrid wave energy converter. This novel hybrid concept combines an oscillating water column and an overtopping device. The breakwater was also studied without the hybrid wave energy device as to enable a thorough comparison between both solutions regarding structural stability, safety, and overtopping performance. The results point towards a considerable reduction in the overtopping volumes through the integration of the hybrid technology by an average value of 50%, while the stability analysis suggests that the toe berm of the breakwater is not significantly affected by the hybrid device, leading to acceptable safety levels. Even so, some block displacements were observed, and the attained stability numbers were slightly above the recommended thresholds from the literature. It is also shown that traditional damage assessment parameters should be applied with care when non-conventional structures are analysed, such as rubble-mound breakwaters with integrated wave energy converters.

Feasibility of the Potential for Wave and Wind Energy Hybrid Farm to Supply Offshore Oil Platform in Gulf of Mexico

Offshore oil and gas platforms use gas turbine with natural gas or fuel diesel for their high demand of power. Due to the declining amount of gas available, high carbon footprint, increasing cost of fuel and inefficient operating, alternative energy options are necessary and imminent. Most offshore oil and gas platforms locate in deep water surrounded by huge amount of energetic wave resources, hence, the feasibility of supplying offshore oil facilities electricity by hybrid wave and wind energy farms based on daily energy power production instead of annual average was conducted in this project. The hybrid energy farm was modeled and validated by applying meteorological data in Gulf of Mexico area from WaveWatch III system. With the hindcast wave and wind condition data from 1979 to 2019, daily energy generation of the hybrid energy farm was estimated. Meantime, the feasibility of suppling offshore oil and gas facilities by the proposed combined hybrid farm was assessed. The project optimized the configuration of the hybrid wave and wind energy farm to satisfy offshore oil and gas platform demands and reduce the variation of power generation, so that it may be feasibility to gradually substitute the gas turbines. Through matching the local wave and wind conditions, the project was able to maximize the power output while minimize the variation within limited ocean surface area. The project addressed the advantages of hybrid wave and wind devices, as well as theoretical prospection of wave harvesting device and wind turbine combination. To validate the proposed optimization model, a case study was explored by using Vesta V90 3MW wind turbines and Pelamis 750kW wave energy converters to supply five offshore platforms in more than 45 m deep water areas. The results indicated the possibility of bringing wave energy into large commercial operation and utilization with minor investment and environmental impact.