Deployment characterization of a floatable tidal energy converter on a tidal channel, Ria Formosa, Portugal

This paper presents the results of a pilot experiment with an existing tidal energy converter (TEC), Evopod 1 kW floatable prototype, in a real test case scenario (Faro Channel, Ria Formosa, Portugal). A baseline marine geophysical, hydrodynamic and ecological study based on the experience collected on the test site is presented. The collected data was used to validate a hydro-morphodynamic model, allowing the selection of the installation area based on both operational and environmental constraints. Operational results related to the description of power generation capacity, energy capture area and proportion of energy flux are presented and discussed, including the failures occurring during the experimental setup. The data is now available to the scientific community and to TEC industry developers, enhancing the operational knowledge of TEC technology concerning efficiency, environmental effects, and interactions (i.e. device/environment). The results can be used by developers on the licensing process, on overcoming the commercial deployment barriers, on offering extra assurance and confidence to investors, who traditionally have seen environmental concerns as a barrier, and on providing the foundations whereupon similar deployment areas can be considered around the world for marine tidal energy extraction.Acknowledgements The paper is a contribution to the SCORE project, funded by the Portuguese Foundation for Science and Technology (FCT e PTDC/ AAG-TEC/1710/2014). Andre Pacheco was supported by the Portu- guese Foundation for Science and Technology under the Portuguese Researchers' Programme 2014 entitled “Exploring new concepts for extracting energy from tides” (IF/00286/2014/CP1234). Eduardo GGorbena has received funding for the OpTiCA project from the ~ Marie Skłodowska-Curie Actions of the European Union's H2020- MSCA-IF-EF-RI-2016/under REA grant agreement n [748747]. The authors would like to thank to the Portuguese Maritime Authorities and Sofareia SA for their help on the deployment.info:eu-repo/semantics/publishedVersio

Beachrock occurrence, characteristics, formation mechanisms and impacts

Beachrocks are hard coastal sedimentary formations consisting of various beach sediments, lithified through the precipitation of carbonate cements. The objectives of this contribution are to (a) collate and review information on the reported occurrences, characteristics and formation mechanisms of beachrocks and (b) consider their impacts on the coastal zone. The analysis of the available information has shown that (a) beachrock formation is a global and diachronic phenomenon and (b) the great majority of beachrocks are found in tropical/subtropical and low temperate latitude, microtidal coasts. The cementing agents of beachrocks are composed predominantly of the metastable carbonate phases High Magnesian Calcite (HMC) and Aragonite (Ar), appearing in a diverse crystalline morphology. It has been suggested that cement precipitation in the coastal environment is controlled by: (i) the physicochemical conditions; (ii) the presence of organic compounds and microbes; (iii) the magnitude and distribution of the wave energy along the coast; and (iv) the textural characteristics of the constituent sediments. Various theories have been proposed to explain beachrock formation itself, linking the phenomenon to either physicochemical or biological processes. These theories, however, do not seem to be of universal validity and acceptance, as each is able to explain only some of the reported occurrences. The presence of beachrocks appears to affect beach morphodynamics by: (i) ‘locking’ the beach profile; (ii) modifying the nearshore hydrodynamics; (iii) changing the porous character of the beach and, thus, its response to wave forcing; and (iv) differential bed erosion at the margins of the beachrock outcrops that can alter significantly the long- and, particularly, the cross-shore sediment transport. Therefore, although relict submerged beachrock outcrops may provide some coastal protection by reducing the wave energy impinging onto the coastline, modern beachrocks may promote offshore loss of unconsolidated beach sediments and buried beachrock outcropping. Finally, the presence of beachrocks may have also significant ecological impacts, as the indigenous (mobile substrate) fauna and flora of the beach is replaced by hard substrate benthic assemblages, which are commonly arranged in hydrodynamically-controlled zones

The use of grain size trend analysis in macrotidal areas with breakwaters: Implications of settling velocity and spatial sampling density

In a macrotidal environment with offshore breakwaters (Elmer, West Sussex) a new approach for the identification of the sediment transport pathways with grain size trend analysis (GSTA) was undertaken using statistical parameters (mean, sorting and skewness) directly derived from settling velocities distributions. The same samples were analysed with sieving (quarter- and half-phi resolution) and GSTA was performed again in order to directly compare the resultant sediment transport directions derived with the two analytical techniques. Furthermore, both regular and irregular sampling distributions were used to recalculate GSTA. Hydrodynamic data were collected in different locations around the breakwaters and net sediment transport directions were calculated in order to assess the accuracy of the sediment transport pathway directions derived with the different analytical techniques.The accuracy of settling velocity in determining the statistical parameters of the grain size distribution is identified, especially for the fine-medium sand sediments. Settling velocities produced better results than the sieving; the quarter-phi resolution producing the poorer results in comparison with the coarser half-phi resolution. The results for the different spatial sampling strategies are found to depend upon the number of samples utilised; that shows that the accuracy of the GSTA is based upon the ability of representing, adequately, the spatial distribution of the sediment parameters.<br/

The role of coastal morphology in influencing sea level variations induced by meteorological forcing in microtidal waters: Examples from the island of crete (Aegean Sea, Greece)

Sea surface variations due to strong (northerly) onshore winds are compared over three different geomorphological settings of the essentially tideless (tidal range &amp;lt; 10 cm) northern coast of Crete (southern Aegean Sea): (i) an open beach zone; (ii) a beach zone with the same offshore characteristics as the previous zone, but protected by a shore-parallel reef; and (iii) a pocket beach located in the cove of a semienclosed gulf. Even though the three beach zones are exposed to similar meteorological forcing (strong northerly winds with speeds &amp;gt; 10 m s-1), they developed different water level variations depending on the local morphological conditions. The beach zone situated in the semienclosed gulf experienced a 3.3 times larger offshore sea surface rise (10 cm) than the unprotected open beach. The presence of the reef, on the third beach, caused a 2.7 times higher increase of the nearshore sea surface elevation (i.e., up to 24.5 cm) than the nearshore sea surface rise (9 cm) measured at the nearby unprotected open coast that experiences similar offshore hydrodynamic conditions. The sea surface variations in the offshore zone are induced primarily by wind forcing and, secondarily, by barometric pressure fluctuations: their corresponding ratios vary from 3.21 in the unprotected open beach, to 2.21 in the pocket beach located in the semienclosed gulf. Sea surface rise within the nearshore zone is controlled mainly by the wave set-up, due to breaking waves; this, at the open coast, is about 1.3 times larger than the wind set-up. Finally, the presence of the reef amplifies sea surface rise along the shoreline, which can easily exceed 0.4 m (15 times the offshore sea surface rise). © 2013 the Coastal Education &amp;amp; Research Foundation (CERF)