A mapping of wind and wave potentials of the whole Mediterranean basin, aimed at identifying the areas where wind and wave events are not time-correlated, was performed in order to plan offshore ...coupled wind-wave energy extraction. For this purpose, meteorological and marine conditions of the whole Mediterranean basin for the period 1979–2016 were obtained by means of WRF and WaveWatchIII simulations. More promising areas where to plan a hybrid installation for the joint exploitation of wind and wave energy resources were thus selected on the basis of a suitable statistical index. Such an index, combines information on the availability of wind and waves together with the degree of correlation of the occurrence of the two resources. The index will efficiently select the most interesting area in the Mediterranean Sea characterized by non-concomitant-in-time availability of wind and wave thus ensuring an optimized time-availability of the combined resources. Finally the power production of an hypothetical hybrid plant composed by different models of wind rotors and wave energy converters is evaluated for four test sites. The results of this analysis shows that the described index represents a useful tool for preliminary evaluation of areas where combined wind-wave energy extraction could be more profitable.
•Combined wind and wave resource assessment over the whole Mediterranean basin on the basis of high-resolution 38-year hindcast•High resolution in space (0.1° lat/lon) and time (1 hr)•Evaluation of exploitability of the combined wind and wave resources by means of a suitable statistical index•Identification of the best sites for the combined wind and wave exploitation in the Mediterranean Sea
The work investigates the potential of the Mediterranean offshore for wave electricity production, providing basin-scale results useful for future smaller-scale studies on specific areas of interest. ...At this purpose, the performance of a selection of offshore wave energy converters (WECs) is assessed all along the Mediterranean coastline (at 10 km resolution), on the basis of a 37-year hindcasted wave data and public WEC performance data. As the analyzed technologies were designed for more energetic wave climates, smaller devices have been considered, downscaled according to the Froude similarity criterion, in order to match Mediterranean wave conditions. At each location, the best device size is determined by simulating different scaled versions of the WECs and then selecting the scaling factor, which maximizes the mean annual capacity factor.
The results show that large part of the Mediterranean coastline can be successfully exploited by properly downscaled versions of the WECs. More specifically, six of the studied wave power technologies can reach a capacity factor higher than 0.2 along 40% of the coastline and three WECs (AquaBuOY, Pelamis and Wavebob) can operate with a capacity factor exceeding 0.3 at 8% of the studied locations. The coastal regions with the highest WEC performance are of the Gulf of Lion, the Sicily channel, the Alboran Sea, the Libyan coast, Crete and Cyprus. The optimal size of the WECs at these locations is between 1/4 and 1/3 of the full WEC size and the resulting rated powers are between 10 and 30 kW. Noteworthy, a quite low performance is found for the most energetic areas of the Mediterranean (for example in western Sardinia), because a large part of the available energy is provided by extreme and rare events, for which the WEC efficiency is very low.
•The performance of eight WECs is assessed along the Mediterranean coastline.•Downscaled devices are considered to match the Mediterranean climate.•The best device size is determined by maximizing the annual capacity factor.•Capacity factors higher than 0.2 are obtained along 40% of the coastline.•The optimal WEC size ranges between 1/4 and 1/3 of full WEC size.
Abstract
A state-of-the-art regional assessment of future directional wave spectra in the Mediterranean Sea and the projected changes with respect to hindcast is presented. A multi-model EURO-CORDEX ...regional ensemble of bias-adjusted wave climate projections in eleven locations of the Mediterranean are used for the assessment of future seasonal changes in the directional wave spectra under the high-emission scenario RCP8.5. This analysis allows us to identify climate change effects on the spectral energy of the swell and wind-sea systems and their seasonal variability which cannot be captured with the standard integrated wave parameters, such as significant wave height and mean wave direction. The results show an overall robust decrease in the predominant wave systems, resulting in a likely decrease in the significant wave height that is in agreement with previous studies. However, the results depict a robust increase in other less energetic frequencies and directions leading to a projected behavioral change from unimodal to bimodal/multimodal wave climate in many locations which has strong repercussions on the vulnerability of coastal assets and ports operability.
The European Interreg Italy–France 2014–2020 Maritime Project SPlasH! (Stop to Plastics in H
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O!) focused on the study of microplastics (MPs) in the marine port environment to evaluate their ...presence, abundance, and mechanisms of diffusion to the open sea. In the framework of this project, a worldwide review of 74 studies was carried out, providing an overview of MP investigation techniques, focusing on sampling strategies, laboratory methodologies, and identification of MPs collected in seawater, and specifically evaluating their applicability to the marine port environment. Nets were the most commonly used device for MP surface sampling, but their use can be difficult in narrow spaces within the port basins, and they must be coupled to discrete sampling devices to cover all port basins. In the laboratory, density separation (NaCl, ZnCl
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, NaI, sodium lauryl sulfate (SLS)), filtration (polycarbonate, polyamide, glass, cellulose, ANOPORE inorganic membrane filters), sieving, visual sorting, and digestion methods (acidic, enzymatic, alkaline, oxidative) were used to separate MPs from seawater. Digestion becomes essential with water samples with great inorganic and organic loads as deriving from a port. Although many studies are based only on visual MP identification under a microscope, analytical identification techniques unequivocally determine the particle nature and the identity of the plastic polymers and are necessary to validate the visual sorting of MPs. Fourier-transform infrared spectroscopy (FTIR) is the most used analytical identification technique.
This work proposes a new general procedure to stochastically analyze multi-model multivariate wave climate time series projections at different temporal scales. For every projection, it characterizes ...significant wave height, peak period and mean direction by means of univariate non-stationary distributions capable of capturing cyclic climate behavior over a reference time interval duration. The temporal dependence between the values at a given sea state and previous short-term wave climate is described with a vector autoregressive model (VAR). The multi-model ensemble wave climate characterization is based on a compound distribution of the individual non-stationary distributions and a weighted averaged VAR model. The methodology is applied to bias-adjusted wave climate projections derived using WaveWatch III forced by wind field data from EURO-CORDEX models at a location close to the Mediterranean Spanish coast. Results are compared to hindcast data which shows a clear bi-seasonal behavior. Different temporal references were considered, starting with a 1-year reference period to analyze overall changes in wave climate at scales ranging from days, months and seasons with respect to historic conditions. The results show that the projected wave climate has a very different temporal behavior than hindcast data, delaying and widening/shortening the start and duration of the two main seasons and including shorter term variations. Regarding the energetic content of the sea states, the compound variable highest percentiles of the significant wave height present lower values than the hindcast (≈3−10%) during the traditionally more severe period (November–March) but higher values (≈10−35%) during the calmer months. The projected peak period presents a similar temporal pattern to the hindcast data, while the mean wave direction shows a significant change from the historical bi-modal behavior towards more likely easterly waves throughout the year. Additionally, a 10-year analysis is done to find larger temporal variabilities such as decadal variations associated with the North Atlantic Oscillation. The observed temporal variability in the yearly seasonal pattern throughout the century is addressed by analysing 20-year rolling windows in all the model projections and in the compound variable. The compound distribution shows significant temporal variabilities throughout the century with the most severe periods and more likely severe waves during summer at the end of the century.
Extreme atmospheric-marine events, known as medicanes (short for "Mediterranean hurricanes"), have affected the Mediterranean basin in recent years, resulting in extensive coastal flooding and storm ...surges, and have occasionally been responsible for several casualties. Considering that the development mechanism of these events is similar to tropical cyclones, it is plausible that these phenomena are strongly affected by sea surface temperatures (SSTs) during their development period (winter and autumn seasons). In this study, we compared satellite data and the numerical reanalysis of SSTs from 1969 to 2023 with in situ data from dataloggers installed at different depths off the coast of southeastern Sicily as well as from data available on Argo floats on the Mediterranean basin. A spectral analysis was performed using a continuous wavelet transform (CWT) for each SST time series to highlight the changes in SSTs prior to the occurrence of Mediterranean Hurricanes as well as the energy content of the various frequencies of the SST signal. The results revealed that decreases in SST occurred prior to the formation of each Mediterranean hurricane, and that this thermal drop phenomenon was not observed in intense extra-tropical systems. The spectral analyses revealed that high CWT coefficients representing high SST energy contents were observed before the occurrence of a Mediterranean hurricane. This information may provide a useful fingerprint for distinguishing Mediterranean hurricanes from common seasonal storms at the onset of these events.
Coastal resilience is often achieved by traditional civil engineering projects, such as dikes and breakwaters. However, given the pressing nature of Climate Change, integrating energy converters in ...“classical” structures can enhance innovation, and help in pursuing decarbonisation targets. In this work, we present an alternative for integrating a wave energy converter at a vertical wall breakwater, following past successful projects. Our approach is based on a high spatio-temporal wave dataset to properly quantify expected energy production, but also focus on the hours for which other time-dependent renewables cannot produce, i.e., solar. Our analysis evaluates the power performance and assesses the economic parameters and viability of the proposed installation. Our integrated solution shares the main capital with the breakwater and can produce from 390 MWh–2300 MWh/year, displacing more than 1760 Tn of CO2 annually. In addition to power generated, we estimated the payback period for most cases being approximately 10–15 years, but when accounting avoided oil CO2 emissions, the installation is highly attractive with payback in less than 9 years, with favourable financing indicating 3.4 years.
Absolute and relative dispersion are fundamental quantities employed in order to assess the mixing strength of a basin. There exists a time scale called Lagrangian Integral Scale associated to ...absolute dispersion that highlights the occurrence of the transition from a quadratic dependence on time to a linear dependence on time. Such a time scale is commonly adopted as an indicator of the duration needed to lose the influence of the initial conditions. This work aims to show that in a semi-enclosed basin the choice of the formulation in order to calculate the absolute dispersion can lead to different results. Moreover, the influence of initial conditions can persist beyond the Lagrangian Integral Scale. Such an influence can be appreciated by evaluating absolute and relative dispersion recursively by changing the initial conditions. Furthermore, finite-size Lyapunov exponents characterize the different regimes of the basin.
Fluid flows reveal a wealth of structures, such as vortices and barriers to transport. Usually, either an Eulerian or a Lagrangian frame of reference is employed in order to detect such features of ...the flow. However, the two frameworks detect structures that have different properties. Indeed, common Eulerian diagnostics (Hua-Klein and Okubo-Weiss criterion) employed in order to detect vortices do not always agree with Lagrangian diagnostics such as finite-time Lyapunov exponents. Besides, the former are Galilean-invariant whereas the latter is objective. However, both the Lagrangian and the Eulerian approaches to coherent structure detection must show some links under any inertial-frame. Compound channels flows have been accurately studied in the past, both from a Lagrangian and an Eulerian point of view. The features detected do not superimpose: Eulerian vortices do not coincide with barriers to transport. The missing link between the two approaches is here recovered thanks to a spectral analysis.
The quality of wind data is being improved, which leads to generating the wave climate with higher accuracy. ...improvements in wind predictions are of prime interest. The results of the analysis ...indicate that binary typhoons not only lead to an increase in significant wave height (Hs), but also result in an enhancement of one-dimensional wave energy and two-dimensional directional wave spectra. According to their findings, the regions with the highest potential for wave energy were located in the westerlies of both hemispheres. ...when taking into account sea level rise, the simulation showed that under storm surge conditions, the wave height is expected to double in the near future (mid-century), and the wave period may also increase by around 1.5 seconds.
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