Large scale power generation from tidal currents will require the deployment of large numbers of tidal turbines arrayed in close proximity to one another. This presents significant challenges; turbine-in-wake interactions, as well as significant opportunities; arraying turbines side-by-side in closely spaced fences can significantly enhance their performance. Extreme weather survivability and the ability to maintain offshore systems are key to delivering economic and durable tidal energy systems. A potential solution to these challenges is floating systems supporting multiple closely spaced turbines. Such systems will provide rapidly deployable, retrievable and maintainable multi-turbine systems that deliver high performance. This project will conduct a preliminary assessment and feasibility study of floating closely spaced tidal turbine arrays. Specifically the project will seek to optimize the hydrodynamic performance of multiple closely spaced turbines supported from a single platform and determine their load and response when subjected to combined wave and tidal flows. The project will also seek to determine the suitability and stability of mooring systems under such loads and the platform's static and dynamic response leading to definition of permissible operating regimes.

In the past decade, tidal stream energy converters have become a major focus for renewable energy R&D with a number of turbine farms now in its planning and development phase. The majority of existing designs for tidal energy devices utilize sea-bed mounted turbine energy converters. These underwater devices however present many challenges related to economic and technical viability in terms of their installations and maintenances cost. In recent years, a floating type tidal energy device is being developed. The installation of such a device comprises of single or multiple turbines mounted on a floating platform anchored to the sea-bed with mooring lines. Research and industry teams in China and UK have presented multiple demonstrations both on a model scale and a full scale floating tidal energy converter. All of the results add credibility to their technical feasibility and cost effective nature as compared to fixed turbines. Despite the advantages of floating tidal current turbines (FTCT) over their fixed counterparts, the existing design guidance is not deemed to be ready for the commercial market. The key challenges include guaranteeing the safety of supporting platform and floating mooring lines, the survivability of large scale rotor under extreme sea conditions, the accurate assessment for the proper site selection and the reliable evaluation of environmental impacts. Existing industry design tools rely very much on the simplified models or individual component design rules which negatively impact the energy extraction process/amount/supply. The proposed project aims to integrate the work already carried out at University of Strathclyde in UK in the field of offshore renewable energy and floating offshore structure with the work performed at (a) Harbin Engineering University in China in the area of floating tidal turbine and (b) Ocean University of China in China in the field of tidal resources and environment impacts assessment. The main goal of the proposed research is to explore whether an integrated method is feasible to better understand the fundamental physics associated with a coupled floating tidal energy system through numerical framework with experimental comparisons and validations. This would then potentially provide more accurate industry design guidelines for the future commercialized FTCTs and other floating marine energy devices.

This project aims to develop a framework that will integrate data collected and recorded through a Structural Health Monitoring (SHM) system for marine energy converters, in order to estimate reliability levels at component and system level in real time and evaluate its ability to further fulfil its intended function. Obtaining a more well-informed understanding of the actual state of the system, alternative operational strategies can be adopted, particularly taking into consideration its residual capacity after extreme environmental events, optimizing its inspection and maintenance scheduling and hence reducing the OPEX. Application of the developed framework on an existing prototype wave device, already developed by the Chinese partners, will allow its validation and extension to future applications. This reference case will be employed in order to classify its components and determine potential failure modes and limit states to assess failure. From the key failure mechanisms that will be identified, arrangements for Structural Health Monitoring will be proposed obtaining data from relevant measurements (ie strains and accelerations) that can then inform the reliability evaluation in real time, updating its operational strategy, particularly taking into consideration residual capacity after extreme environmental events. Outcome of the project will be a generic framework applicable to a range of marine energy devices.

The Made in China 2025 report, highlights ocean renewable energy technologies as one of the 10 areas of opportunity for UK and Chinese companies. The "Outline of the National Marine Economic Development Plan" specifically targets the development of novel ocean farming methods, more productive but also more socially and environmentally compatible. In the EU, the "Blue Growth" program aims at sustainable growth in the marine and maritime sectors, already representing 5.4 million jobs and generating a gross added value of 500 billion euros a year. Offshore structures are very costly. The main idea of a Multi-Purpose Platform (MPP), integrating (for example) renewable energy devices and aquaculture facilities, is to find the synergies to share manufacturing, installation, operation and maintenance, and decommissioning costs. This has the potential to, save money, reduce the overall impact, and maximize the socio-economic benefits. MPP development poses cross-disciplinary challenges, since they simultaneously aim to achieve several potentially conflicting objectives: to be techno-economically feasible, environmentally considered, socially beneficial, and compatible with maritime legislations. In the EU, previous research focused on farms of multi-megawatt MPP (ocean renewable devices + aquaculture systems), with very few/no attempts to investigate lower rated power systems suitable for island/coastal communities. In China, previous projects aimed at island communities focused on renewable energy, but they did not integrate any aquaculture elements. Therefore, for island communities, novel fundamental questions arise, especially in terms of techno-economic feasibility and assessment and maximization of socio-environmental benefits at a completely different scale, but still requiring a whole-system, cross-disciplinary approach. The proposed solution is to investigate which are the specific challenges arising from the integration of these different offshore technologies, and with a multi-disciplinary approach to tackle them, making sure that all the dimensions (technological, economic, social, environmental, legal) are taken into account. The renewable energy technologies (Which wind turbine? Which wave device? What kind of solar panel?) and aquaculture systems most suitable for the needs of an island community will be identified, and the "cross-disciplinary" questions will be defined, e.g. "What is the impact of the noise generated by the renewable energy devices on the (closely co-located) aquaculture species growth rate?". Answering these questions, the novel contribution will consist in developing approaches to assess the feasibility of an MPP system, focusing on: global MPP dynamic response to metocean conditions, overall integrated control and power management strategies, environmental impact, socio-economic risks and benefits. The potential of these methodologies will be then show-cased through two case-studies, one focusing on an island community in China, and one in the UK. This consortium brings together internationally recognised experts from three Chinese and three British universities and institutes, for a total of 20 investigators, in the fields of solar and offshore wind and wave energy, control systems for renewable energy devices, environmental and socio-economic impact of renewables and aquaculture systems, aquaculture and integrated multi-trophic aquaculture development, and ecosystem modelling. These investigators are also leading members of the research community, directly involved in: Renewable Energy Key Lab of Chinese Academy of Sciences, IEC and Chinese National Standardization Committee for Marine Energy Devices, Supergen Wind Hub, EU Energy Research Alliance JP Wind, ITTC Ocean Engineering Committee, the Royal Institution of Naval Architects Maritime Innovation Committee, ICES WG-Marine Mammal Ecology, International Platform for Biodiversity and Ecosystem, Ecopath Consortium Advisory Board.