Showing papers on "Wave power published in 2010"
TL;DR: In this article, the development of wave energy utilization since the 1970s is discussed, with a focus on the characterization of the wave energy resource; theoretical background, with especial relevance to hydrodynamics of wave absorption and control; how a large range of devices kept being proposed and studied, and how such devices can be organized into classes; the conception, design, model-testing, construction and deployment into real sea of prototypes.
Abstract: Sea wave energy is being increasingly regarded in many countries as a major and promising resource. The paper deals with the development of wave energy utilization since the 1970s. Several topics are addressed: the characterization of the wave energy resource; theoretical background, with especial relevance to hydrodynamics of wave energy absorption and control; how a large range of devices kept being proposed and studied, and how such devices can be organized into classes; the conception, design, model-testing, construction and deployment into real sea of prototypes; and the development of specific equipment (air and water turbines, high-pressure hydraulics, linear electrical generators) and mooring systems.
2,115 citations
TL;DR: A nationally consistent wave resource assessment is presented for Australian shelf ( −1 (90th percentile of 60-78kW/m −1 ), delivering 800-1100 GJ/m−1 of energy in an average year as mentioned in this paper.
188 citations
Dissertation•
28 May 2010
TL;DR: In this paper, the authors assessed and characterized the substantial wave energy resource of the US Pacific Northwest (i.e., off the coasts of Washington, Oregon and N. California) and found that the sea states with the greatest significant wave heights contribute little to the annual energy, but are critically important when considering reliability and survivability of ocean wave energy converters.
Abstract: The substantial wave energy resource of the US Pacific Northwest (i.e. off the coasts of Washington, Oregon and N. California) is assessed and characterized. Archived spectral records from ten wave measurement buoys operated and maintained by the National Data Buoy Center and the Coastal Data Information Program form the basis of this investigation. Because an ocean wave energy converter must reliably convert the energetic resource and survive operational risks, a comprehensive characterization of the expected range of sea states is essential. Six quantities were calculated to characterize each hourly sea state: omnidirectional wave power, significant wave height, energy period, spectral width, direction of the maximum directionally resolved wave power and directionality coefficient. The temporal variability of these characteristic quantities is depicted at different scales and is seen to be considerable. The mean wave power during the winter months was found to be up to 7 times that of the summer mean. Winter energy flux also tends to have a longer energy period, a narrower spectral width, and a reduced directional spread, when compared to summer months. Locations closer to shore, where the mean water depth is less than 50 m, tended to exhibit lower omnidirectional wave power, but were more uniform directionally. Cumulative distributions of both occurrence and contribution to total energy are presented, over each of the six quantities characterizing the resource. It is clear that the sea states occurring most often are not necessarily those that contribute most to the total incident wave energy. The sea states with the greatest contribution to energy have significant wave heights between 2 and 5 m and energy periods between 8 and 12 s. Sea states with the greatest significant wave heights (e.g.>7 m) contribute little to the annual energy, but are critically important when considering reliability and survivability of ocean wave energy converters.
161 citations
TL;DR: In this article, the authors used the SIMAR-44 dataset, composed of hindcast data spanning 44 years (1958-2001), alongside wave buoy data and numerical modelling to assess the potential of the area around Cape Estaca de Bares (the northernmost point of Iberia) for wave energy exploitation.
149 citations
TL;DR: In this article, the offshore and inshore wave energy resource in Asturias (N Spain) is studied using wave buoy data and a hindcast dataset spanning 44 years (1958-2001).
143 citations
TL;DR: In this paper, the wave energy resource of the SE Bay of Biscay was investigated using wave buoy data and a hindcast data set covering a 44-year period (1958-2001).
139 citations
TL;DR: In this article, the Lysekil project, run by Uppsala University and situated on the Swedish west coast, demonstrates ongoing and future environmental studies to be performed along with technical research and development.
Abstract: Generating electricity from waves is predicted to be a new source of renewable energy conversion expanding significantly, with a global potential in the range of wind and hydropower. Several wave power techniques are on the merge of commercialisation, and thus evoke questions of environmental concern. Conservation matters are to some extent valid independent of technique but we mainly focus on point absorbing linear generators. By giving examples from the Lysekil project, run by Uppsala University and situated on the Swedish west coast, we demonstrate ongoing and future environmental studies to be performed along with technical research and development. We describe general environmental aspects generated by wave power projects; issues also likely to appear in Environmental Impact Assessment studies. Colonisation patterns and biofouling are discussed with particular reference to changes of the seabed and alterations due to new substrates. A purposeful artificial reef design to specially cater for economically important or threatened species is also discussed. Questions related to fish, fishery and marine mammals are other examples of topics where, e.g. no-take zones, marine bioacoustics and electromagnetic fields are important areas. In this review we point out areas in which studies likely will be needed, as ventures out in the oceans also will give ample opportunities for marine environmental research in general and in areas not previously studied. Marine environmental and ecological aspects appear to be unavoidable for application processes and in post-deployment studies concerning renewable energy extraction. Still, all large-scale renewable energy conversion will cause some impact mainly by being area demanding. An early incorporation of multidisciplinary and high quality research might be a key for new ocean-based techniques.
130 citations
TL;DR: In this paper, wave farms composed of two either surging or heaving wave energy converters are considered and the impact on the absorbed wave power of the separating distance between the two systems and the wave direction is studied.
113 citations
TL;DR: In this article, the authors investigated the wave resource of La Palma using a 44-year hindcast dataset obtained through numerical modeling and validated with wave buoy records. And they found that the bulk of the energy is provided by waves between 9.5 and 13.5 meters.
81 citations
TL;DR: In this paper, the results from the hydraulic linear wave simulator, using a real wave profiles captured at a location in the UK using an ultrasound system, were shown that a ± 0.8 m wave at 10 s time period, produced a conditioned power output of approximately 22 kW at optimum load conditions for the tested 3-phase 44 kW permanent magnet generator type STK500.
68 citations
TL;DR: In this article, the authors present a set of robust approximations to the solutions of the linear Alfven wave reflection equations, and compare the results to exact solutions of wave transport equations in several cases relevant to the fast and slow solar wind.
Abstract: The origins of the hot solar corona and the supersonically expanding solar wind are still the subject of debate. A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a physically motivated way of specifying the coronal heating rate. Recent one-dimensional models have been found to reproduce many observed features of the solar wind by assuming the energy comes from Alfven waves that are partially reflected, then dissipated by magnetohydrodynamic turbulence. However, the nonlocal physics of wave reflection has made it difficult to apply these processes to more sophisticated (three-dimensional) models. This paper presents a set of robust approximations to the solutions of the linear Alfven wave reflection equations. A key ingredient of the turbulent heating rate is the ratio of inward-to-outward wave power, and the approximations developed here allow this to be written explicitly in terms of local plasma properties at any given location. The coronal heating also depends on the frequency spectrum of Alfven waves in the open-field corona, which has not yet been measured directly. A model-based assumption is used here for the spectrum, but the results of future measurements can be incorporated easily. The resulting expression for the coronal heating rate is self-contained, computationally efficient, and applicable directly to global models of the corona and heliosphere. This paper tests and validates the approximations by comparing the results to exact solutions of the wave transport equations in several cases relevant to the fast and slow solar wind.
TL;DR: In this article, a large circular oscillating water column (OWC) installed at the tip of a coastal corner is examined under the assumption of irrotational flow, and a linear theory is employed.
TL;DR: In this paper, the authors examined theoretically power extraction by a compact array of small buoys, that do not resonate but possess many degrees of freedom, and showed that such systems have certain advantages over a single large buoy.
Abstract: Wave energy converters are usually designed to achieve maximum efficiency by impedance matching with the incoming waves One of the simplest design is a buoy attached to an energy absorber (power-takeoff devise) For maximum efficiency, the buoy must be large enough in order to resonate at the peak frequency of the incident sea, and the extraction rate is the same as the rate of radiation damping With one or few degrees of freedom the resonance peak(s) is(are) usually band-limited The latter feature is common to all wave-power absorbers based on impedance matching Inspired by the FO3 system being developed in Norway by Fred Olsen and ABB Associates, and the Manchester Bobber from UK, the authors examine theoretically power extraction by a compact array of small buoys, that do not resonate but possess many degrees of freedom It is shown that such systems have certain advantages over a single large buoy
Patent•
06 Oct 2010
TL;DR: In this paper, a wave energy conversion device for relatively shallow water, which has a base portion for anchoring to the bed of a body of water and an upstanding flap portion (8 ) pivotally connected to the base portion, is described.
Abstract: The present invention relates to a wave energy conversion device ( 1 ), for use in relatively shallow water, which has a base portion ( 2 ) for anchoring to the bed of a body of water ( 6 ) and an upstanding flap portion ( 8 ) pivotally connected ( 12 ) to the base portion. The flap portion is biased to the vertical and oscillates, backwards and forwards about the vertical in response to wave motion acting on its faces. Power extraction means extract energy from the movement of the flap portion. When the base portion ( 2 ) is anchored to the bed of a body of water ( 6 ) with the flap portion ( 8 ) facing the wave motion, the base portion ( 2 ) and the flap portion ( 8 ) extend vertically through at least the entire depth of the water, to present a substantially continuous surface to the wave motion throughout the full depth of water from the wave crest to the sea bed. A plurality of devices can be interconnected to form one system. The distance between the plurality of flaps is dependent on the wavelength.
TL;DR: In this paper, an asymptotic theory of scattering and radiation by a linear array of heaving buoys in a channel and attached to power-takeoff devices is presented.
Abstract: Future designs of systems for power extraction from ocean waves will likely involve a periodic array of absorbing units. We report an asymptotic theory of scattering and radiation by a linear array of heaving buoys in a channel and attached to power-takeoff devices. The spacing between buoys is assumed to be comparable to the incident wavelength and sea depth but much greater than the buoy size. The effects of extraction rate on the buoy motion, transmission and reflection coefficients for a range of frequencies in and outside the band gap are studied. It is found that strong reflection for frequencies inside the band gap of Bragg resonance reduces the extraction efficiency significantly. For comparison an alternate theory for the efficiency away from the band gap is derived by using Froude-Krylov approximation. The predictions confirms and complements the asymptotic theory.
TL;DR: In this article, the hydrodynamic functioning of an oscillating water column (OWC) in the presence of an underwater tri-dimensional mound (UTDM) through large-scale ocean engineering basin experiments is described.
TL;DR: In this paper, the authors used the Lyon-Fedder-Mobarry magnetohydrodynamic (LFM) code to quantify the wave power of the ULF wave in the radiation belt.
Abstract: [1] To provide critical ULF wave field information for radial diffusion studies in the radiation belts, we quantify ULF wave power (f = 0.5–8.3 mHz) in GOES observations and magnetic field predictions from a global magnetospheric model. A statistical study of 9 years of GOES data reveals the wave local time distribution and power at geosynchronous orbit in field-aligned coordinates as functions of wave frequency, solar wind conditions (Vx, ΔPd and IMF Bz) and geomagnetic activity levels (Kp, Dst and AE). ULF wave power grows monotonically with increasing solar wind Vx, dynamic pressure variations ΔPd and geomagnetic indices in a highly correlated way. During intervals of northward and southward IMF Bz, wave activity concentrates on the dayside and nightside sectors, respectively, due to different wave generation mechanisms in primarily open and closed magnetospheric configurations. Since global magnetospheric models have recently been used to trace particles in radiation belt studies, it is important to quantify the wave predictions of these models at frequencies relevant to electron dynamics (mHz range). Using 27 days of real interplanetary conditions as model inputs, we examine the ULF wave predictions modeled by the Lyon-Fedder-Mobarry magnetohydrodynamic code. The LFM code does well at reproducing, in a statistical sense, the ULF waves observed by GOES. This suggests that the LFM code is capable of modeling variability in the magnetosphere on ULF time scales during typical conditions. The code provides a long-missing wave field model needed to quantify the interaction of radiation belt electrons with realistic, global ULF waves throughout the inner magnetosphere.
TL;DR: In this article, the electrical power integration of a heaving point absorber wave energy converter to a remote island community of population 100 is investigated, taking into account the local geography.
TL;DR: In this article, the sensitivity of a wave power system to variations in still water levels and significant wave heights was investigated, and a theoretical expression to describe this effect was derived, and compared to measured experimental values for the wave energy converter L1 at the Lysekil research site.
Abstract: This paper investigates the sensitivity of a wave power system to variations in still water levels and significant wave heights. The system consists of a floating point absorber connected to a linear generator on the seabed. Changing still water levels are expected to affect the power absorption, since they will displace the equilibrium position for the generator translator. Similarly, changing significant wave heights will affect the rate at which the translator leaves the stator. Both these effects will in some cases result in a smaller active area of the stator. A theoretical expression to describe this effect is derived, and compared to measured experimental values for the wave energy converter L1 at the Lysekil research site. During the time of measurements, the still water levels at the site were in the range of [-0.70 m, +0.46 m ], and the significant wave heights in the range of [0 m, 2.7 m]. The experimental values exhibit characteristics similar to those of the theoretical expression, especially with changing significant wave heights.
TL;DR: In this article, the performance of an array of closely spaced point absorbers is numerically assessed in a frequency domain model, where each point absorber is restricted to the heave mode and is assumed to have its own linear power take-off (PTO) system.
Abstract: The performance of an array of closely spaced point absorbers is numerically assessed in a frequency domain model. Each point absorber is restricted to the heave mode and is assumed to have its own linear power take-off (PTO) system. Unidirectional irregular incident waves are considered, representing the wave climate at Westhinder on the Belgian Continental Shelf. The impact of slamming, stroke and force restrictions on the power absorption is evaluated and optimal PTO parameters are determined. For multiple bodies optimal control parameters (CP) are not only dependent on the incoming waves, but also on the position and behaviour of the other buoys. Applying the optimal control values for a single buoy to multiple closely spaced buoys results in a suboptimal solution for the array. Other ways to determine the PTO parameters are diagonal optimisation (DO) and individual optimisation. These methods are applied to two array layouts consisting of 12 buoys in a staggered grid and 21 buoys in an aligned grid. Compared to DO, it was found that individually optimising the CP increased the energy absorption at Westhinder with about 16-18% for the two layouts, respectively.
01 Jul 2010
TL;DR: In this article, the authors presented an assessment on whether it is feasible to integrate the wave energy systems into the current Turkish Energy Program, which has been conducted by using RETScreen® International, “Small Hydro” in order to find out the cost effectiveness of a wave power converter system to harness the sea power from Turkish waters having a mild climate.
Abstract: As long as it is economical, Turkey, which is encircled on three sides by the seas, should have the utmost benefit of using her existing potential of the wave motion. This paper presents our assessment on whether it is feasible to integrate the wave energy systems into the current Turkish Energy Program. The data required for calculating the approximate wave energy densities at many sites along the Turkish coasts have been derived from “Wind and Deep Water Wave Atlas of the Turkish Coast”, MEDCOAST Publications, have been used in a wave energy project analysis, which has been conducted by using RETScreen® International, “Small Hydro” in order to find out the cost effectiveness of a wave power converter system to harness the sea power from Turkish waters having a mild climate. The technically available resource has been estimated approximately 10 TWh/year with an annual wave power between 4 and 17 kW/m. This is 7.8 % of the economically feasible potential of current
TL;DR: In this article, a simplified pitch-catch model of power and energy transduction of piezoelectric wafer active sensors (PWAS) attached to structure is presented.
Abstract: This paper presents a systematic investigation of power and energy transduction in piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM). After a literature review of the state of the art, the paper develops a simplified pitch-catch model of power and energy transduction of PWAS attached to structure. The model assumptions include: (a) 1-D axial and flexural wave propagation; (b) ideal bonding (pin-force) connection between PWAS and structure; (c) ideal excitation source at the transmitter PWAS and fully-resistive external load at the receiver PWAS. Frequency response functions are developed for voltage, current, complex power, active power, etc. First, we examined PWAS transmitter and determined the active power, reactive power, power rating of electrical requirement under harmonic voltage excitation. It was found that the reactive power is dominant and defines the power requirement for power supply / amplifier for PWAS applications. The electrical and mechanical power analysis at the PWAS structure interface indicates all the active electrical power provides the mechanical power at the interface. This provides the power and energy for the axial and flexural waves power and energy that propagate into the structure. The sum of forward and backward wave power equals the mechanical power PWAS applied to the structure. The parametric study of PWAS transmitter size shows the proper size and excitation frequency selection based on the tuning effects. Second, we studied the PWAS receiver structural interface acoustic and electrical energy transduction. The parametric study of receiver size, receiver impedance and external electrical load gives the PWAS design guideline for PWAS sensing and power harvesting applications. Finally we considered the power flow for a complete pitch-catch setup. In pitch-catch mode, the power flows from electrical source into piezoelectric power at the transmitter; the piezoelectric conduction converts the electrical power into the mechanical interface power at the transmitter PWAS and then into the acoustic wave power travelling in the structure. The wave power arrives at the receiver PWAS and is captured at the mechanical interface between the receiver PWAS and the structure; the captured mechanical power is converted back into electrical power at the receiver PWAS and measured by the receiver electrical instrument. Our numerical simulation and graphical chart show the trends in the power and energy flow behavior with remarkable peaks and valleys that can be exploited for optimum design.
TL;DR: In this paper, a mixed integer optimization model of the Haida Gwaii network is used to develop an operational strategy indicative of realistic operator behaviour for capturing wave energy to potentially reduce energy costs.
01 Jan 2010
TL;DR: In this article, a system for operation of directly driven offshore wave energy converters is described, which includes laboratory testing of a permanent magnet linear generative model for wave energy conversion.
Abstract: This thesis deals with a system for operation of directly driven offshore wave energy converters. The work that has been carried out includes laboratory testing of a permanent magnet linear generat ...
01 Jan 2010
TL;DR: In this article, a mechanical oscillator model was proposed in order to examine this relationship for the heave motion of a floating wave energy conversion device, and the effect of relative OWC and floating structure natural frequencies, the phase relationships of the various system components and the optimal power take-off damping of the system was determined.
Abstract: The study of floating oscillating water column (OWC) wave energy conversion (WEC) device performance includes analysis of the dynamic coupling of the water column and the floating structure. In the present investigation, a mechanical oscillator model was proposed in order to examine this relationship for the heave motion of a floating wave energy conversion device. Characterisation of the dynamic system optimal behaviour was performed by examining the effect of relative OWC and floating structure natural frequencies, the phase relationships of the various system components and the optimal power take-off damping of the system. It was determined that separation of the natural frequencies results in significant increases in maximum power capture. When the OWC and structure natural frequencies are coincident the motions are essentially in phase and limited power capture is achieved. For optimal power capture the separation of the natural frequencies should be such that the floating structure has the lower natural frequency. This should also generally result in improved alignment of the system resonant response with the available wave power. The model also provides evidence of the capacity of power take-off damping control to improve the nonresonant performance ofthe OWC WEC device in a spectrally distributed wave environment.
TL;DR: In this article, the performance of a newly developed direct drive hydro turbine (DDT), which will be built in a caisson for a wave power plant, was investigated, and the results showed that the DDT obtains fairly good turbine efficiency in cases with and without wave conditions.
Abstract: Clean and renewable energy technologies using ocean energy give us non-polluting alternatives to fossil-fueled power plants as a countermeasure against global warming and growing demand for electrical energy. Among the ocean energy resources, wave power takes a growing interest because of its enormous amount of potential energy in the world. Therefore, various types of wave power systems to capture the energy of ocean waves have been developed. However, a suitable turbine type is not yet normalized because of relatively low efficiency of the turbine systems. The purpose of this study is to investigate the performance of a newly developed direct drive hydro turbine (DDT), which will be built in a caisson for a wave power plant. Experiment and CFD analysis are conducted to clarify the turbine performance and internal flow characteristics. The results show that the DDT obtains fairly good turbine efficiency in cases with and without wave conditions. Most of the output power is generated at the runner passage of Stage 2. Relatively larger amount of the decreased tangential velocity at Stage 2 produces more angular momentum than that at Stage 1 and thus, the larger angular momentum at the Stage 2 makes a greater contribution to the generation of total output power in comparison with that at Stage 1. Large vortex existing in the upper-left region of the runner passage forms a large recirculation region in the runner passage, and the recirculating flow consumes the output power at Region 2.
Patent•
24 Nov 2010
TL;DR: In this article, a method for maneuvering a buoyant body (11) of a wave power converter (12), including a mechanical-electric, mechanical-hydraulic or piezo-electric energy converter (16), is presented.
Abstract: Method for maneuvering a buoyant body (11) of a wave power converter (12), said wave power converter (12) including a mechanical-electric, mechanical-hydraulic or piezo-electric energy converter (16) which is arranged in the sea under the buoyant body (11), said buoyant body (11) and wave power converter (12) being connected by a wire (13), and which buoyant body (11) is provided with at least one ballast tank (22) for controlling the buoyancy of the buoyant body (11), where the method includes, by means of measuring equipment acquiring information regarding wire (13) tension, filling level/pressure in the ballast tank (22) and stroke of the energy converter (16), and based on this information controlling the buoyancy of the buoyant body (11) by supplying/discharging water/air to/from the ballast tank (22) while at the same time adjusting the tension of the wire (13) by operating a winch (24) arranged in the buoyant body (11). The object of this controlling is to lower or raise the buoyant body (11) without removing the wire tension, and to provide optimal strokes for the energy converter (16) in relation to the wave movements at the surface affecting the buoyant body (11). The invention also relates to a wave power plant for executing the method.
TL;DR: A scaling model based on the dissipated wave power and a surf similarity parameter is proposed and compared to measurements and the predictions show satisfactory agreement to the measurements.
Abstract: This paper describes a semi-empiric model and measurements of air-borne sound generated by breaking sea waves. Measurements have been performed at the Baltic Sea. Shores with different slopes and sediment types have been investigated. Results showed that the sound pressure level increased from 60 dB at 0.4 m wave height to 78 dB at 2.0 m wave height. The 1/3 octave spectrum was dependent on the surf type. A scaling model based on the dissipated wave power and a surf similarity parameter is proposed and compared to measurements. The predictions show satisfactory agreement to the measurements.
Patent•
08 Apr 2010
TL;DR: In this paper, a wave power plant with floating chambers moving relative to each other and following the undulating water surface is described, over which two joint connections are fixed to the floating chambers in a rotating manner.
Abstract: The wave power plant (1) has floating chambers (2) moving relative to each other and follow the undulating water surface (8). A bar element (6) and a kinetic energy receiving energy transformation unit (4) are provided between floating chambers, over which two joint connections (12,14) are fixed to the floating chambers in a rotating manner.
28 Dec 2010
TL;DR: In this article, the inertial effects of the gyroscope are activated by the float motion and are used to drive a generator, and the whole system operates in the clean environment inside the float.
Abstract: The extraction of energy from ocean waves has been investigated in Europe since the 1970s. During the research process hundreds of devices have been proposed and a few of them have been built full scale and deployed to the ocean. Unlike other renewable energies, so far there has not been a device standing out to be the most suitable to exploit wave power. One of the practical problems to be solved in a Wave Energy Converter (WEC) is durability in the harsh marine environment. This could be critical if parts of the converter such as turbine rotors or auxiliary floats are needed to move or to react while exposed to seawater and spray. One method to solve the problem is to use a WEC composed just by one sealed floating body carrying a gyroscope. The inertial effects of the gyroscope are activated by the float motion and are used to drive a generator. The whole system operates in the clean environment inside the float. In this work a procedure to design the ISWEC device (Inertial Sea Wave Energy Converter) is outlined. The mechanical equations describing the system are linearized, studied in the frequency domain and used as a mathematical tool in the design process. The method is then applied iteratively to design a scaled prototype model to be tested in the wave tank at the University of Naples. The final version of the prototype model is then scaled up to evaluate the performances of a full scale device.Copyright © 2010 by ASME