Results 1 - 10 of 136
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[en] The wave- or thalasso-energy, potentially as promising as wind energy, have started to develop in Europe. Great Britain has already a good experience in this domain but France shows also ambitions in this beginning industry with several projects in progress. This article makes an overview of the existing tide-, current- and wave-powered generators: tide mills, underwater hydro-turbines, immersed linear generators, air-compression systems, buoy systems, etc. (J.S.)
[en] The problem of sizing an electricity storage for a 5000 inhabitants island supplied by both marine renewables (offshore wind and waves) and the mainland grid is addressed by a case study based on a full year resource and consumption data. Generators, transmission lines and battery storage are accounted for through basic simplified models while the focus is put on electricity import/export budget. Self-sufficiency does not seem a reasonable goal to pursue, but partial autonomy provided by renewable sources and a medium size storage would probably be profitable to the island community. (author)
[en] A case is made for the inclusion of marine-derived energy to be a part of the energy mix which will deliver clean secure energy in the future. But at present, in Europe, only the United Kingdom and Portugal are offering the necessary incentives to realise the marine renewable energy potential. The UK government's views were expressed in May 2005 in a paper called Wave and Tidal Energy Demonstration Scheme. The government's policy is to encourage a large number of small diverse projects rather than a small number of large projects. Details of the financial incentives on offer are given. It is concluded that in the UK at least, policymakers must guarantee a smooth path to resource for first arrays or risk losing what could be their last chance to build an indigenous energy industry for a significant international market
[en] Wave turbine technology is reaching maturity. The scottish firm, Wavegen, one of the world leaders in the sector, has installed its first commercial model, ''limpet'' in the faroe islands. This document presents an economic evaluation of the project and discusses also on the crucial problem of this produced electricity transport and deliver. (A.L.B.)
[en] Marine renewable energy is an emergent sector in Canada. Although supply chain studies have been performed on the United Kingdom and the United States markets, no study has been conducted yet in Canada. The aim of this study was therefore to perform a supply chain analysis in Canada to assess the maturity, strengths, and weaknesses of the sector and determine where the opportunities lie. The study emphasises that the sector is still at the prototype stage in Canada and that the industry must learn to improve its technology and begin to take on large scale projects. Canada has several strengths in the marine renewable energy sector, mainly in terms of resources and facilities, but there are also weaknesses pertaining to technology development and experience. The study concluded that the development of the sector must be centered on a solid vision; in the near term, technological innovation is needed to reach pre-commercialization while in the long term, the sector should aim for commercial application.
[en] Parasitic capillary ripples generated on the forward face of the gravity-capillary waves are investigated experimentally. Using the optical technique, the slope angle of the wave is measured with sufficient space and time resolution to characterize the small ripple fluctuations. The ripple generation and its steepness is considered from the point of dominant wave asymmetry. The unsteady motion of ripples is analyzed by the two-points optical measurements. Dominant wave has the same phase speed with ripple on average, however the relative distance to the dominant wave fluctuates which can't be negligible comparing with the ripple wavelength. That is, the non-linear interactions with the dominant wave assumed to be essential. (authors)
[en] The world's first tidal power station is scheduled for stat-up in the spring of 2003. It is located in Kvalsundet, off Hammerfest, Norway. This is a pilot installation of a 300 kW tidal turbine at a depth of 50 metres. When fully developed in 2007, the tidal power plant will deliver 32 GWh per year. Hammerfest Stroem has patented the energy and the company hopes to be able to install similar power stations both in Norway and abroad. The potential worldwide is claimed to be more than 450 TWh per year
[en] Recent rapid advances of tidal current energy extraction (TCEE) technologies and resource analyses suggest in excess of 20,000 GWh/annum of electricity may be realistically exploitable in the near term off Canada's West Coast. Moreover, because tidal currents have a semidiurnal (or, in some locations, diurnal) periodicity, and can be predicted and quantified on a spatial and temporal basis, this resource confers a distinct advantage over most other renewables, and, therefore, may achieve supply security. In this study, TCEE technologies are assessed on the basis of energy delivered, environmental intrusion and economic viability. As such, relevant issues including resource characteristics, site selection, conversion efficiencies, capacity factors, power densities, hydrodynamic feedbacks, and grid integration are addressed. (author)
[en] ISWEC (Inertial Sea Wave Energy Converter) is a floating marine device able to harvest sea waves energy by the interaction between the pitching motion of a floater and a spinning flywheel which can drive an electric PTO. In the ISWEC the hull dynamics is governed and controlled by the gyroscopic torque. The optimal control logic results in tuning the floater dynamics to the incoming waves in order to maximize the power transfer from the waves to the floater. In this paper the control problems of the ISWEC are stated and a control scheme based on the sub-optimal stochastic control logic is presented. The control scheme here presented has been tested using real wave records acquired at the deployment location in Pantelleria Island, which is one of the most energetic sites of the Mediterranean Sea.
[en] Two successive wave heights are modeled by a Gaussian copula, which is referred to as the Nataf model. Results with two initial distributions for the transformation are presented, the Naes model [Naes A. On the distribution of crest to trough wave heights. Ocean Engineering (1985);12(3):221-34] and a two-parameter Weibull distribution, where the latter is in best agreement with data. The results are compared with existing models. The Nataf model has also been used for modeling three successive wave heights. Results show that the Nataf transformation of three successive wave heights can be approximated by a first order autoregressive model. This means that the distribution of the wave height given the previous wave height is independent of the wave heights prior to the previous wave height. Thus, the joint distribution of three successive wave heights can be obtained by combining conditional bivariate distributions. The simulation of successive wave heights can be done directly without simulating the time series of the complete surface elevation. Successive wave periods with corresponding wave heights exceeding a certain threshold have also been studied. Results show that the distribution for successive wave periods when the corresponding wave heights exceed the root-mean-square value of the wave heights, can be approximated by a multivariate Gaussian distribution. The theoretical distributions are compared with observed wave data obtained from field measurements in the central North Sea and in the Japan Sea, with laboratory data and numerical simulations. (author)