Search results for "Shore"
showing 10 items of 263 documents
Seawater carbonate chemistry and fish communities properties off CO2 seeps in Japan
2020
Ocean acidification will likely change the structure and function of coastal marine ecosystems over coming decades. Volcanic carbon dioxide seeps generate dissolved CO2 and pH gradients that provide realistic insights into the direction and magnitude of these changes. Here, we used fish and benthic community surveys to assess the spatio-temporal dynamics of fish community properties off CO2 seeps in Japan. Adding to previous evidence from ocean acidification ecosystem studies conducted elsewhere, our findings documented shifts from calcified to non-calcified habitats with reduced benthic complexity. In addition, we found that such habitat transition led to decreased diversity of associated …
Seawater carbonate chemistry and coralline algal diversity
2021
Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and …
Structural Safety Assessment of Marine Operations From a Long-Term Perspective: A Case Study of Offshore Wind Turbine Blade Installation
2019
Abstract A marine operation is a complex non-routine activity of limited duration carried out in offshore environment. Due to safety reasons, these operations are normally performed within specific sea state limits, which are derived from numerical modelling and analysis of hazardous events. In view of the uncertainties in the assessment of structural responses under stochastic environmental conditions, these limiting curves correspond to a target structural failure probability recommended in offshore standards (for example, 10−4 per operation as specified by DNV-GL). However, one of the main limitations is that these curves do not reflect site-specific safety assessment. The current paper …
Numerical study of a concept for major repair and replacement of offshore wind turbine blades
2020
Repair and replacement of offshore wind turbine blades are necessary for current and future offshore wind turbines. To date, repair activities are often conducted using huge jack-up crane vessels and by applying a reverse installation procedure. Because of the high costs associated with installation and removal of offshore wind turbine components and the low profit margin of the offshore wind industry, alternative methods forinstallation and removal are needed. This paper introduces a novel concept for replacement or installation of offshore windturbine blades. The concept involves a medium-sized jack-up crane vessel and a tower climbing mechanism. This mechanism provides a stable platform …
Optimal maintenance system for offshore wind turbines
2010
In the last years, the industry of wind power generators has developed in many aspects. The offshore plants have some benefits over the onshore ones but their implementation is really expensive.Based in that cost, this paper describes the importance of applying an optimal maintenance based in priorities and cost. It also studies the maintenance types and proposes a scheme of maintenance for offshore plants.
Effect of a Passive Tuned Mass Damper on Offshore Installation of a Wind Turbine Nacelle
2021
Abstract Although the installation of offshore wind turbines takes place in calm seas, successful mating of wind turbine components can be challenging due to the relative motions between the two mating parts. This work investigates the effect of a passive tuned mass damper on the mating processes of a nacelle for a 10-megawatt (MW) offshore wind turbine. A nacelle with lifting wires and a monopile with a mass damper are respectively modelled using the multibody formulation in the HAWC2 program. A single mass damper is tuned to target at the first natural period of the monopile and is coupled to the main program using a dynamic link library. Afterwards, numerical simulations were carried out…
PRELIMINARY INVESTIGATIONS ON THE FLORA OF THE PERMANENT BANQUETTES IN WESTERN SICILY
2016
The banquettes, landed clusters of dead leaves of Posidonia oceanica (L.) Delile, represent a deposited biomass from sea to land that protects the shoreline from wind and sea erosion as well as constitutes a reserve of nutrients and organic matter for sea prairies. These wracks can become a potential biodiversity hotspot as indicated by a recent investigation on invertebrates that has shown high levels of consumption of detritus (1). This biodiversity, greater than that found in coastal areas without such accumulations, can be explained by the margin effect between the marine and the terrestrial environment. The banquette can therefore be considered an ecotone (2, 3) where communities of su…
Wind energy potential assessment in order to produce electrical energy for case study in Divandareh, Iran
2014
This paper evaluates the electricity production at Divandareh, a place located at Kurdistan, Iran through wind energy assessment using wind data of the site recorded in duration of a year at three different heights of 10, 30 and 50 meters. For this purpose, a statistical analysis of the measured wind data is performed. According to the US standards, the site is found to be a class-3 wind power site with power density of 336.18 W/m2 at 50 m height. Moreover, dominant flow direction of wind is checked through wind rose plotting. It has been shown that the site is suitable for wind energy development by installing wind turbines with tall towers. Thereupon, four different commercial wind turbin…
Evaluating the Performances of Small Wind Turbines: A Case Study in the South of Italy
2012
AbstractAmong renewable energy resources, wind energy became more attractive in the last decade. Wind farms installations dramatically increased in areas where climatic conditions, topography and environment have allowed their development. The installation of wind turbines, usually carried out in remote areas, recently began to cover areas identified by a complex terrain such as urban and suburban zones. Although these new sites’ choices are characterized by lower productivity there is increasing interest in wind energy production in both urban and suburban area. In this work the authors have carried out an energy analysis developed from a sample of small wind turbines available on the mark…
The opportunity of using wave energy converters in a Mediterranean hot spot
2022
The opportunity of using wave energy converter arrays in a hot spot area of the Mediterranean sea was investigated. For this purpose, numerical simulations of wave energy converters together with a simple cost-effective analysis were carried out. The selected study area is one of the most energetic inside the Sicilian channel (Italy). The numerical simulations were performed using the SNL-SWAN (“Sandia National Laboratories – Simulating WAves Nearshore”) spectral model with an unstructured mesh. The power absorbed from thirteen Wave Energy Converter (WEC) devices was computed. In particular, Pelamis, Wave Dragon, Oyster 2, Wavestar, B-HBA, B-OF, Bref-HB, Bref-SHB, F–2HB, F–3OF, F-HBA and F-…