205,541 research outputs found

    Visualizing characteristics of ocean data collected during the Shuttle Imaging Radar-B experiment

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    Topographic measurements of sea surface elevation collected by the Surface Contour Radar (SCR) during NASA's Shuttle Imaging Radar (SIR-B) experiment are plotted as three dimensional surface plots to observe wave height variance along the track of a P-3 aircraft. Ocean wave spectra were computed from rotating altimeter measurements acquired by the Radar Ocean Wave Spectrometer (ROWS). Fourier power spectra computed from SIR-B synthetic aperture radar (SAR) images of the ocean are compared to ROWS surface wave spectra. Fourier inversion of SAR spectra, after subtraction of spectral noise and modeling of wave height modulation, yields topography similar to direct measurements made by SCR. Visual perspectives on the SCR and SAR ocean data are compared. Threshold distinctions between surface elevation and texture modulations of SAR data are considered within the context of a dynamic statistical model of rough surface scattering. The result of these endeavors is insight as to the physical mechanism governing the imaging of ocean waves with SAR

    Catching the Right Wave: Evaluating Wave Energy Resources and Potential Compatibility with Existing Marine and Coastal Uses

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    Many hope that ocean waves will be a source for clean, safe, reliable and affordable energy, yet wave energy conversion facilities may affect marine ecosystems through a variety of mechanisms, including competition with other human uses. We developed a decision-support tool to assist siting wave energy facilities, which allows the user to balance the need for profitability of the facilities with the need to minimize conflicts with other ocean uses. Our wave energy model quantifies harvestable wave energy and evaluates the net present value (NPV) of a wave energy facility based on a capital investment analysis. The model has a flexible framework and can be easily applied to wave energy projects at local, regional, and global scales. We applied the model and compatibility analysis on the west coast of Vancouver Island, British Columbia, Canada to provide information for ongoing marine spatial planning, including potential wave energy projects. In particular, we conducted a spatial overlap analysis with a variety of existing uses and ecological characteristics, and a quantitative compatibility analysis with commercial fisheries data. We found that wave power and harvestable wave energy gradually increase offshore as wave conditions intensify. However, areas with high economic potential for wave energy facilities were closer to cable landing points because of the cost of bringing energy ashore and thus in nearshore areas that support a number of different human uses. We show that the maximum combined economic benefit from wave energy and other uses is likely to be realized if wave energy facilities are sited in areas that maximize wave energy NPV and minimize conflict with existing ocean uses. Our tools will help decision-makers explore alternative locations for wave energy facilities by mapping expected wave energy NPV and helping to identify sites that provide maximal returns yet avoid spatial competition with existing ocean uses

    Relations for a periodic array of flap-type wave energy converters

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    This paper investigates the interaction of plane incident waves with a wave farm in the open ocean. The farm consists of a periodic array of large flap-type wave energy converters. A linear inviscid potential-flow model, already developed by the authors for a single flap in a channel, is considered. Asymptotic analysis of the wave field allows to obtain new expressions of the reflection, transmission and radiation coefficients of the system. It is shown that, unlike a line of heaving buoys, an array of flap-type converters is able to exploit resonance of the system transverse modes in order to attain high capture factor levels. Relations between the hydrodynamic coefficients are derived and applied for optimising the power output of the wave farm.Comment: Accepted for publication on Applied Ocean Research, 26 Sept 201

    Designing an Accessible Wave Energy Conversion Device for Powering Ocean Sensors

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    Currently, less than 5% of our oceans are comprehensively monitored and much more ocean data is needed to facilitate understanding of ocean physics, carbon cycling, and ocean ecosystems. Today, most autonomous ocean sensors are powered by primary battery, which have both limited capacity and lifetime. The goal of this research is to design a small, accessible renewable wave energy device to power autonomous free-floating ocean sensors. By designing a cheap, accessible, and simple wave energy converter, this work hopes to make ocean sensor deployment easier and cheaper for researchers, increase the lifetime of autonomous ocean sensors, and reduce the reliance on non-renewable battery power sources. This work presents the final mechanical and electrical designs for a linear point absorber wave energy converter to power a range of ocean sensors

    Using pressure and seismological broadband ocean data model shear wave velocities in the North Atlantic

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    EGU2010-10518 Seafloor compliance is the transfer function between pressure and vertical displacement at the seafloor Infragravity waves in the oceanic layer have long periods in the range of 30 – 500 s and obey a simple frequencywavenumber relation. Seafloor compliance from infragravity waves can be analyzed with single station recordings to determinate sub-seafloor shear wave velocities. Previous studies in the Pacific Ocean have demonstrated that reliable near-surface shear wave profiles can be derived from infragravity wave compliance. However, these studies indicate that, beside the water depth the compliance measurements are limited by instrument sensitivity, calibration uncertainties and possibly other effects. In this work seafloor compliance and infragravity waves are observed at two different locations in the Atlantic Ocean: the Logatchev hydrothermal field at the Mid Atlantic Ridge and the Azores (Sao Miguel Island). The data was acquired with the broadband ocean compliance station developed at the University of Hamburg as well as ocean station from the German instrument pool for amphibian seismology (DEPAS) equipped with broadband seismometers and pressure sensors. Vertical velocity and pressure data were used to calculate power spectral densities and normalized compliance along two profiles (one in each location). Power spectral densities show a dominant peak at low frequencies (0.01-0.035Hz) limited by the expected cut-off frequency, which is dependent on the water depth at each station. The peak has been interpreted as a strong infragravity wave with values between 10-14 and 10-11 (m/s2)2/Hz and 104 and 106 (Pa2)2/Hz for acceleration and pressure respectively. The results show compliance values between 10-10 and 10-8 1/Pa and its estimations take into account the coherence between seismic and pressure signals in order to confirm that the seismic signals in the infragravity waves are caused by pressure sources. Shear wave velocity models, with depth resolution from 200 to 2500 m for the deep water stations, were derived from compliance. Preliminary results indicate shear wave velocity increasing from 200 to 3500 m/s

    Towards Blue Energy: The Design, Dynamics, and Control of an Innovative Power Take Off for Ocean Wave Energy Harvesting

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    The ocean wave energy potential along US coastline is 64% of the electricity generated from all sources in the US. Over 53% of the population live with 50 miles off the coasts, so ocean waves offer ready opportunity to provide electricity without long-distance electricity transmission. However, the ocean wave energy harvesting is still in its infant stage worldwide. The power takeoff (PTO), the machinery to convert the mechanical energy into electricity, is widely considered as the single most important element in wave energy technology, and underlies many of the failures to date (A. Falcao 2010). Revolutionary power takeoff beyond the direct and indirect drives is urgently needed in order to realize the vast blue energy potential from the ocean. This talk will present the design, dynamics modelling, power electronics control, lab test, wave tank test, and ocean trial of a mechanical motion rectifier based power takeoff, which converts the irregular oscillatory wave motion into regular unidirectional rotation of the generator. Lab tests show that up to 80% mechanical energy conversion efficiency was achieved with reduced force in the PTO motion system. The rotatory inertia and two-body system design can further increase the power output in a large frequency range. Wave tank test and ocean trail also validated the high efficiency and reliability. Please click Additional Files below to see the full abstract

    Ocean energy:the wave of the future

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    The power point presentation discussed the developing technology of ocean energy with design convergence on tidal but not on wave. Today's technologies will help solve the immediate needs, but we need to work hard nurturing tomorrow's low carbon technologies today. Ocean energy represents one of the more difficult forms of renewable energy to harness. The UK is leading internationally in the development of marine energy but further development investment is needed to move the technology forward. Marine energy could supply up to 2 GW of UK electricity demand by 2020 and significantly more than this by 2050. The development of ocean energy and promising ocean driven machines are briefly reviewed, their operating conditions and the suitability of different types of hydro turbines for use as power take off options, the recent international experience, and how the technology is developing

    Evaluation of spatio-temporal variability of ocean wave power resource around Sri Lanka

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    The paper presents a detailed analysis of the spatio-temporal variability of wave power resource around Sri Lanka, using computationally simulated 25 years of wave data that represents the prevailing ocean climate in the region. The computational wave model was validated against a measured wave dataset collected over a 44-month period at 70 m water depth off the coast of the south-west of Sri Lanka and compared with ERA-Interim Reanalysis wave data and, good agreement found. The analysis reveals that the ocean around Sri Lanka from the south-west to south-east have a substantial wave power resource. The available offshore wave power resource remains between 10 and 20 kW/s throughout the year although it is significantly modulated by the south-west monsoon which falls between May and September thus increasing the power up to around 30 kW/m. The inter-annual to decadal scale variability of wave power resource remains small. Wave power reduces when waves travel from the margin of the narrow continental shelf around Sri Lanka to shallow water areas closer to the shoreline. A significant longshore variability of wave power is also observed where the south-west coast of Sri Lanka has the highest available power under the prevailing ocean climate
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