Energy converted from ocean waves has the potential to make a significant contribution to the worlds energy requirements. However to do this wave energy converters will need to form part of wave energy farms, where arrays of devices are deployed in the same geographical vicinity. Current plans for arrays of point absorber wave energy converters generally have devices with individual PTO systems. These generate electricity locally, which is then delivered to a central hub before being transmitted ashore. In this project an alternative to each device having an individual PTO is investigated, with the aim of significantly reducing the cost of arrays. Several individual point absorber devices will pump air to and from a single central common PTO, which will then generate electricity centrally. Such a configuration has the potential for significant cost savings, resulting from a reduction in the amount of electrical generation technology used within the array. There are also potential power smoothing effects resulting from several point absorbers, at different stages in their power capture cycle, feeding into the same PTO. However by sharing a common PTO control strategies, such as latching and variable damping, can no longer be applied to individual devices. There will also be losses brought about by the longer transmission distances of air between the power capture mechanism and the PTO. This may be significant. The use of a common PTO will also further complicate the intra array effects between individual point absorbers within the array. The project will examine these potential advantages and disadvantages of using a common PTO, with the aim of providing design guidance to the wave energy industry and research community. The work is being conducted as a collaboration between Plymouth University and Dalian University of Technology. Physical experiments will be conducted at Plymouth University with arrays of up to 4 devices and at two different scales. Results from these measurements will then be used to validate both a frequency and a time domain model developed at Dalian University of Technology. The numerical models can be used to model larger arrays and different configurations, before finally both experimental and numerical results are used to provide design guidance on the use of common PTO.

This work is undertaken in the context of the UK-China "Marine Development Feasibility Studies" call. This call was developed through a joint workshop between the UK and China research councils. As part of this workshop, four key areas were identified as critical to the development of wave and tidal energy in China. The research proposed here spans across two of these areas: "Increasing Survivability" and "Holistic Integrated Design Tools". More specifically, the aims and objectives of the present work address important questions related to "Understanding the system dynamics to increase reliability and survivability". In the context of holistic design tools, the research addresses improvements in "CFD techniques (including potential flow models) to assess fluid structure interactions". These two key elements of the present work are tightly linked, with one building upon the other. Whilst enhanced CFD techniques act as important design tools for wave energy conversion (WEC) developers, they are also urgently required to enable and understanding of WEC loading regimes. A firm understanding of loading regimes, in turn, will lead to improved design for survivability. These novel techniques are also crucial in addressing issues related to device reliability and fatigue loading. In addressing these challenges, the understanding of viscous effects and nonlinearities are central. The enhanced physical understanding of both viscous effects and nonlinearity in wave structure interactions is believed to stimulate the development of wave energy extraction in both China and the UK. In the case of China, this is hoped to reduce the high dependence on fossil resources currently imported from abroad. For the UK, the development of wave energy is an important element in meeting the long-term CO2 emission targets. The new unified model to be developed in this project will lead to a more efficient and accurate coupling method for the prediction of hydrodynamic characteristics, dynamic loadings and fatigue effects. Taken as a whole, this provides the base for the improved design of floating WECs, their survivability, and practical maintenance.

A key concern for tidal farm developers and investors is resource quantification. The ultimate aim of this project is to develop a tidal farm design tool that produces trustworthy results while requiring a level of computing power that is appropriate to industrial design. Once developed, the model can be extended towards analysis of sediment transport and thus can be used to understand the effect of large farms on the marine environment, which will be a key area of concern to stakeholders in the future.

The coastal zone is a unique geological, physical and biological area of vital economic, cultural and environmental value. More than two-thirds of the world's population is concentrated in coastal zones, where the coastline is either central or of great importance to trade, transport, tourism, leisure and the harvesting of marine food. Breakwaters are commonly adopted to protect and enhance the utility of coastlines. Worldwide, the combined costs for building new breakwaters and maintaining the existing ones are in the order of tens of billions of pounds a year.Breakwaters are vulnerable to the liquefaction of the seabed foundation, a process that can often lead to significant degradation of the foundation in as little as a few years after construction and sometimes even result in total collapse. The inappropriate design or maintenance of breakwaters can lead to catastrophic coastal disaster. For example, the failure of Sines Breakwater in Portugal caused damage equivalent to almost US$1 billion in reconstruction alone, excluding the huge economic and social impacts on the region. A recent example of coastal tragedy due to failure of breakwaters is that of New Orleans during Hurricane Katrina, putting 80% of the city under as much as 6 m of water and causing deaths and personal and economic chaos. The economic loss from the disaster was more than US$15 billion.In this study, we will firstly extend the existing 2D wave and soil models to 3D, and then integrate them into a single model to provide a better prediction of the wave-induced liquefaction around breakwater heads. A series of physical model experiments will be conducted for the verification of the proposed theoretical models. The proposed research is an essential step towards significantly improved engineering design and remedial action to address foundation-related damage to coastal structures. The underlying conceptual innovation of the project comes from three factors that combine to enable the proper understanding of the WSSI phenomenon: 1) the integration of all three components of wave/seabed interactions around breakwater heads; 2) the treatment of the seabed as a general porous media with large deformation; and 3) the use of 3D rather than 2D modelling. This approach is essential as it is the only way to simulate wave patterns around breakwater heads, model wave energy dissipation in marine sediments (including the critical phenomenon of flow through porous media) and account fully the interactions between waves, seabed and structures. .