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Tidal stream energy is a low carbon energy source. Tidal stream turbines operate in a turbulent environment, and the effect of the structure between the turbine and seabed on this environment is not fully understood. An experimental study using 1:72 scale models based on a commercial turbine design was carried out to study the support structure influence on turbulence intensity around turbine blades. The study was conducted using the wave-current tank at LABIMA, University of Florence. A realistic flow environment (ambient turbulent intensity = 11%) was established. Turbulence intensity was measured upstream and downstream of a turbine mounted on two different support structures (one resembling a commercial design, the other the same with an additional vertical element), in order to quantify any variation in turbulence and performance between the support structures. Turbine drive power was used to calculate power generation. Acoustic Doppler Velocimetry was used to record and calculate upstream and downstream turbulence intensity. In otherwise identical conditions, performance variation of only 4% was observed between two support structures. Turbulent intensity at 1, 3 and 5 blade diameters, both upstream and downstream, showed variation up to 21% between the two cases. The additional turbulent structures generated by the additional element of the second support structure appears to cause this effect, and the upstream propagation of turbulent intensity is believed to be permitted by surface waves. This result is significant for the prediction of turbine array performance.

Energy transitions require strategic plans that minimize inefficiencies and maximize energy production in a sustainable way. This aspect is fundamental in the case of innovative technologies based on marine renewable energies. Marine renewable energies involve problems and advantages which imply a reconceptualization of marine space and its management. Through an holistic SWOT analysis the main strengths, weaknesses, opportunities and threats are highlighted in this paper, considering social, economic, legal, technological, and environmental dimensions. We disaggregate the SWOT analysis for marine renewable energy technologies in order to create an overview of pros and cons for every dimension and better identify specific hotspots and possible solutions in different fields.

The exploitation of marine renewable energy sources, such as offshore wind (OW), wave (WA), and tidal stream (TS) energy, is essential to reducing carbon emissions in China. Here, we demonstrate that a well-designed deployment of OW-WA-TS joint exploitation would be better than OW alone in improving performance in terms of the total amount and temporal stability of integrated power output in the northern Bohai Sea/Strait, the Subei Shoal, and the surrounding areas of Taiwan and Hainan Island. The design principles for an efficient joint energy deployment can be summarized as follows: first, a small ratio of WA output favors a temporally stable performance, except for areas around Taiwan Island and southwest of Hainan Island. Second, more TS turbines will contribute to steadier integrated outputs. Meanwhile, in the coastal waters of Guangdong and Zhejiang, the potential of WA to increase the total amount of power output is very high due to its minor impact on temporal stability. Finally, joint exploitation significantly reduces diurnal power fluctuations compared with OW alone, which is crucial for the steady operation of power grids, power sufficiency, and controllability in periods with low or no wind.

Abstract Marine currents may represent a renewable energy source characterized by a limited environmental impact. In Italy, the Strait of Messina seems to be suited for exploitation of this energy source. A vertical axis turbine, with blades oscillating about the pivotal axis according to the Voith–Schneider system, has been considered. This paper presents a preliminary theoretical investigation of the performance of this kind of turbine that may be employed to tap marine currents energy sources. The investigation is conducted by means of a simple momentum model based on the “single-disk single-streamtube” approach. The theoretical results are compared with experimental measurements. The adequate agreement between experimental and theoretical results shows that such a simple model may be able to predict the power coefficient and the operating range of the turbine.

It is increasingly evident that a sustainable use of the sea and of technologies and services that support this sustainability are fundamental for the impact they have also on the sustainability of the mainland. The Blue Growth, a knowledge driven exploitation of the marine resources, is a target that EU and many other countries have set to improve the societal wellbeing. In particular the Mediterranean has still unexploited potentials to provide very specific ecosystem services and new technologies in order to contribute to economic growth. To this aim, the European Commission funded the Bluemed project (2016-2020), which involves nine different European countries (Croatia, Cyprus, France, Greece, Italy, Malta, Portugal, Slovenia, Spain) and their relevant stakeholders in the definition of shared strategies at national and international level; the Italian National Research Council (CNR) coordinates Bluemed. Given this framework, the present paper, starts from the main outcomes of Bluemed on research and innovation in the Mediterranean, through a detailed analysis of the most relevant activities and thematic objectives for some of the main marine and maritime socio-economic drivers (transport, tourism, energy have been chosen). Then, on that basis and with the support of a deep literature overview, it tries to understand the present status of some relevant sectors for their potential impact on technology and innovation on this maritime area, highlighting the main obstacles to the fulfilment of the planned priorities and proposing possible strategies to overcome them; all this starting from an Italian perspective. The emphasis is put just on the gaps and barriers to Blue Growth, and on the ways to overcome them, to help the identification of cross-cutting high-level priorities and actions for research and innovation, to be shared at national and Mediterranean level. The main contribution of the work presented here is the recognition that concrete steps towards a "Blue" economy can be achieved only by going beyond the identification of research and innovation challenges and priorities for specific sectors, since they necessarily reflect a partial, sectorial view, and that the main effort must be directed towards an integrated view of how different activities, often conflicting, might coexists. Another finding is the planning of roadmaps to follow so that new technologies/knowledge could overcome those conflicts. As a consequence, the aim and the output of the paper is not proposing a further detailed list of Research and Innovation priorities, but is instead trying to identify how the most relevant R&I challenges for Blue Growth already available can be more efficiently pursued following the roadmaps proposed in the paper.

Blue Energy (BE) is expected to play a strategic role in the energy transition of Europe, particularly toward the 2050 horizon. It refers to a set of Marine Energy Sources (MES), including offshore wind, waves, tides, marine currents, sea thermal energy, salinity gradients, and marine biomass, which are exploited by different BE technologies. Nevertheless, the implementation of integrated solutions to exploit MES in marine areas does not just concern technological issues; it requires inclusive planning practices considering different aspects regarding climate and environmental impacts, landscape compatibility, interference with other marine activities (such as shipping, fishing, and tourism), and social acceptance. A replicable BE planning framework has been developed based on interdisciplinary knowledge in three Mediterranean sites in Greece, Croatia, and Cyprus, under the scope of the Interreg Med BLUE DEAL project. It has been implemented by some interdisciplinary experts through a collaborative and iterative process of data elaboration, mapping, evaluation, and visualization. Results concern the localization of suitable sites to install BE plants and the estimation of potential energy production and avoided emissions in selected scenarios. Together with visual simulations, this study shows the potential effects of the implementation of BE in specific marine areas, with a special focus on the most promising offshore floating wind farms and wave energy converters (WECs), as basic information for participative design and stakeholder engagement initiatives, including public authorities, businesses, and citizens.

The strict emission standards for port approach and coastal navigation, and the fuel-saving requirements, in the marine sector, are pushing the manufactures to consider more advanced and alternative propulsion systems. In this context, this study deals with the design and management of an innovative hybrid thermal-electric propulsion system. The evaluations are referred to the case study of a leisure boat, which is used for passenger transportation in tourist areas. Experimental tests are carried out on single components, with a particular focus on re-calibration of the thermal engine, for its homologation and optimal use in the proposed hybrid architecture. The identification of proper management strategies is performed on the basis of a boat simulation model, which is set up starting from experimental data and characteristics of components. In this regard, an optimization procedure, based on the use of genetic algorithms, is performed in order to set the parameters of onboard energy management strategies and pursue the double objective of extending battery pack cycling life and reducing exhaust emissions. The obtained simulation results highlight the benefits of the proposed architecture showing sensible improvements in comparison with a traditional ICE based configuration. The methodology proposed in this paper enables reliable evaluations and preliminary optimization of energy management strategies, with a drastic reduction in experimentation time and general costs.

This report describes the realization of a comprehensive digital model of the Calm Water Towing (CWT) tank facility at the Institute of Marine Engineering (CNR-INM). The digital model describes the full infrastructure, including the tank and the towing carriage, and provides a digital twin that allows to simulate the various phases in preparation, execution and decommissioning of experimental activities in the facility. The digital twin has been developed in a Solid Works software environment and consists in a digital project, with drawings, previews, rendering and animations that can be downloaded in the most popular formats. In the report, the methodology has been described and examples of applications of the digital tool to ongoing and future activities are described. The activity has been undertaken and partially funded in the framework of the CNR Project ULYSSES 2030 (Underpinning Laboratory for Sea Energy Systems) and of the EU-funded project, H2020 CRIMSON, dealing with the demonstration of innovative hydrokinetic turbines for the exploitation of tidal and river energy. Nonetheless, the validity of the digital twin is general, with application to all types of testing programs in the facility.