Balancing power production and coastal protection: A bi-objective analysis of Wave Energy Converters

Wave Energy Converters (WECs) have the potential to serve dual purposes, generating power and protecting coastlines. Although traditionally the focus has been on maximizing power generation for cost-effectiveness, growing impacts of climate change have made coastal protection increasingly imperative. However, power production and coastal protection have been addressed separately, missing potential synergies. This paper addresses this gap by conducting a bi-objective analysis to investigate the interactions between power extraction and wave attenuation for a single Oscillating Surge Wave Converter (OSWC) and WEC farms of three and five units. A linear Power Take-Off (PTO) system, with passive and reactive control strategies, is examined. By varying the PTO parameters, we assess their influence on both power production and wave field attenuation. Results demonstrate a significant impact of the PTO choice on wave attenuation, with a similar trend observed for power production. This finding highlights the potential for a trade-off, where maximizing wave attenuation may come at the cost of moderate energy output. Furthermore, the interactions observed within the WEC farms enhance this trend. The study emphasizes the importance of a holistic approach to WEC technology development, promoting sustainable and resilient harnessing of wave energy resources, considering both power generation and coastal protection

Wasserstein model reduction approach for parametrized flow problems in porous media

The aim of this work is to build a reduced order model for parametrized porous media equations. The main challenge of this type of problems is that the Kolmogorov width of the solution manifold typically decays quite slowly and thus makes usual linear model order reduction methods inappropriate. In this work, we investigate an adaptation of the methodology proposed in [Ehrlacher et al., Nonlinear model reduction on metric spaces. Application to one-dimensional conservative PDEs in Wasserstein spaces, ESAIM: Mathematical Modelling and Numerical Analysis (2020)], based on the use of Wasserstein barycenters [Agueh & Carlier, Barycenters in the Wasserstein Space, SIAM Journal on Mathematical Analysis (2011)], to the case of non-conservative problems. Numerical examples in one-dimensional test cases illustrate the advantages and limitations of this approach and suggest further research directions that we intend to explore in the future

Wasserstein model reduction approach for parametrized flow problems in porous media

The aim of this work is to build a reduced-order model for parametrized porous media equations. The main challenge of this type of problems is that the Kolmogorov width of the solution manifold typically decays quite slowly and thus makes usual linear model-order reduction methods inappropriate. In this work, we investigate an adaptation of the methodology proposed in [15], based on the use of Wasserstein barycenters [1], to the case of non-conservative problems. Numerical examples in one-dimensional test cases illustrate the advantages and limitations of this approach and suggest further research directions that we intend to explore in the future.Le but de ce travail est de construire un modèle réduit pour des problèmes d'écoulements en milieux poreux paramétrés. La difficulté principale de ce type de problèmes est que la distance de Kolmogorov de l'ensemble de solutions décroît lentement, rendant ainsi les méthodes de réduction de modèles linéaires usuelles inefficaces. Ici, nous proposons une adaptation de la méthodologie proposée dans [15], utilisant des barycentres de Wasserstein [1], au cas de problèmes non conservatifs. Des tests numériques en dimension 1 permettent d'illustrer les avantages et les limitations de cette approche et d'identifier des pistes de recherche que nous souhaiterons aborder dans un futur travail

Conservation of birds in fragmented landscapes requires protected areas

For successful conservation of biodiversity, it is vital to know whether protected areas in increasingly fragmented landscapes effectively safeguard species. However, how large habitat fragments must be, and what level of protection is required to sustain species, remains poorly known. We compiled a global dataset on almost 2000 bird species in 741 forest fragments varying in size and protection status, and show that protection is associated with higher bird occurrence, especially for threatened species. Protection becomes increasingly effective with increasing size of forest fragments. For forest fragments >50 ha our results show that strict protection (International Union for Conservation of Nature [IUCN] categories I–IV) is strongly associated with higher bird occurrence, whereas fragments had to be at least 175 ha for moderate protection (IUCN categories V and VI) to have a positive effect. This meta-analysis quantifies the importance of fragment size, protection status, and their interaction for the conservation of bird species communities, and stresses that protection should not be limited to large pristine areas

Gaia Early Data Release 3: Structure and properties of the Magellanic Clouds

We compare the Gaia DR2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insights into features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones

On the influence of multidirectional irregular waves on the PeWEC device

International audienceWave energy is a promising renewable resource for its reliability and power density, and many technological milestones have been achieved. Significant efforts are made to design and optimize Wave Energy Converters (WECs); however, analyses are often limited to simplified conditions. Among such restrictive assumptions, waves are frequently described utilizing monodirectional spectra, thus leading to approximate evaluations, also in terms of absorbed power. In real sea conditions, the waves are multidirectional, and the analysis as a 2D superposition of multiple wave components should be investigated. In particular, linear waves can be analyzed as a sum of sine waves characterized by different amplitudes, frequencies, phases and directions. The case study device analyzed in this paper is PeWEC (Pendulum Wave Energy Converter), a rotating mass device that converts energy based on pitch motion, moored through a spread catenary mooring system. The sea states investigated are those of the island of Cyprus. The spectrum is defined as the combination between the JONSWAP frequency spectrum and the cos-2s directional spectrum. To compute the sea elevation components the Deterministic Amplitude Scheme (DAS) method is used. The forcing acting on the device, the mooring loads and the device motions are examined and compared to quantify the error produced by the monodirectional approximations. The time domain solver OrcaFlex is employed to investigate the interaction of the waves with the moored hull. Compared with the multidirectional analysis, the monodirectional approximation generates an overestimation of the pitch by 5% and of the surge by 3%, highlighting the importance of taking spreading into account if the device is directional

Influence of hydrodynamic interactions on the productivity of PeWEC wave energy converter array

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Multiquery analysis of a PeWEC farm

International audienceThe maximization of the power output of an array of wave energy converters (WECs) and its impact on the surrounding area are two fundamental, strictly interconnected, aspects that must be considered in the design of a wave farm. The effect of those two elements combined, usually considered separately, is evaluated, in this study, for a small farm of floating devices. The numerical simulations are performed using a coupled model between the BEM solver Capytaine (near-field solution) and the wave propagation model MILDwave (far-field solution). The farm is located off the coast of Pantelleria Island and is composed of three PeWECs, WECs designed for the Mediterranean Sea. The power output and the perturbed wave field around the PeWEC farm are compared to the single device, for different distances among the WECs. Moreover, a Power Take-Off (PTO) is implemented for assessing the difference in the far-field effects between a controlled and an uncontrolled case. Results show that the wake produced by the PeWEC farm is more prominent and more complex with respect to the single device. The inclusion of the PTO contributes to further attenuate the wave field in the lee of the PeWEC farm