WavEC Offshore Renewables

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WavEC Offshore Renewables

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Limpo J.,University of Lisbon | Castro R.,University of Lisbon | Sarmento A.,WavEC Offshore Renewables | Raventos A.,WavEC Offshore Renewables | Correia C.,Vestas Inc.
Journal of Ocean and Wind Energy | Year: 2014

It is now apparent that offshore wind farms will become an important source of electricity to explore further in the near future, providing an increasing integration of the seas. Therefore, new challenges concerning the electrical network design, the operation of offshore wind farms with large installed capacities, and their economic aspects are expected to arise. The main target of this paper is to present and discuss the main steps towards an electrical and economic assessment of offshore wind energy in shallow waters. The methodologies are applied to an offshore wind farm case study, composed of 54 V112-3 MW wind turbines located in the Portuguese coastal zone at 20 to 40 m depth and about 10 km from the shore. From an electrical point of view, the main technical options are revised, and the basic options are made regarding the configuration and design of the collection and transmission systems. A financial analysis is also conducted after the energy yield computation and the identification of the CAPEX and OPEX cost components are performed. A comparative study using the Feed-in Tariffs (FITs) currently in force in eight European countries is carried out, enabling the conclusion that the Belgium and UK support schemes are the most favorable. © 2014. The International Society of Offshore and Polar Engineers.

Henriques J.C.C.,University of Lisbon | Candido J.J.,WavEC Offshore Renewables | Pontes M.T.,University of Lisbon | Falcao A.F.O.,University of Lisbon
Energy | Year: 2013

The objective of this paper is to present the wave energy resource assessment having in view the construction of an OWC (oscillating water column) to be integrated into a new breakwater at the mouth of the Douro River in Porto (northern Portugal). The paper starts with the evaluation of the offshore wave energy resource from measured data. This is followed by the wave transformation from offshore conditions to the plant location in about 11m water-depth. Such transformation was carried out using an inverse-ray refraction model that is described in detail. As expected, the wave power level is lower, whereas the wave energy period is higher, at the plant coastal site as compared with deep water conditions. The average wave direction rotates from approximately NW offshore to nearly West at the plant location, and the directional spread becomes smaller, which are effects of refraction as the waves propagate in waters of decreasing depth. © 2013 Elsevier Ltd.

Vieira M.,University of Lisbon | Sarmento A.,WavEC Offshore Renewables | Reis L.,University of Lisbon
Engineering Failure Analysis | Year: 2015

The working principle of the Wells turbine, used in the ocean energy extraction, can sometimes lead to stall in the turbine blades and stators' vanes, which is an unintended action considering that creates potentially damaging conditions to the mechanical components, plus reducing the efficiency of the take-off system. This work focused on the cracking damage caused to the earth-side guide vanes of the Pico Island Wave Power Plant due to the loading from turbulent air flow and consequent vibrations, as a result of turbine stall. Comprehensive analysis of the design and manufacturing phases, as well as of the constitutive metal properties (AISI 316L stainless steel), including the consequences of welding, was carried out. Strain gages were used to evaluate the loading profile in real-sea working conditions and different suggestions were made in order to postpone and prevent crack nucleation and propagation. The appearance of cracks seems to have been caused by mistakes made at both design and manufacturing phases, eliminating from the guide vanes the ability to endure the aggressive loads which they were subjected to. The lack of an active control strategy on the power plant resulted in consistent turbine stall events, thus contributing to the excessive loadings imposed to the vanes. © 2015 Elsevier Ltd.

George J.,University of Lisbon | Sarmento A.,WavEC Offshore Renewables | Godreau C.,University of Lisbon
Renewable Energies Offshore - 1st International Conference on Renewable Energies Offshore, RENEW 2014 | Year: 2015

The present study reports the evaluation of two different floating semi-submersible platform designs to support large offshore wind turbines. Based on the 5MW-platform used in the OC4-project (Offshore Code Comparison Collaboration Continuation), two different models -straight upscale, and draft limited upscale were developed to carry 7.5MW and 10MW rated wind turbines. The main focus is set on the analysis and comparison of the platforms’ stability, for various load cases representing European offshore conditions in time and frequency domains, based on numerical simulations. In pitch-motion, larger platforms show a slightly higher response to acting forces. In general, the modified platforms with reduced draft show a better stability compared to the straight upscaled platforms. The infrastructural and natural conditions, seem to allow an implementation of such platforms. However, limitations apply to the biggest platforms. A brief economical evaluation indicates that the economies of scale might justify the deployment of such systems. © 2015 Taylor & Francis Group, London.

Gomes R.P.F.,University of Lisbon | Lopes M.F.P.,WavEC Offshore Renewables | Henriques J.C.C.,University of Lisbon | Gato L.M.C.,University of Lisbon | Falcao A.F.O.,University of Lisbon
Ocean Engineering | Year: 2015

This paper presents a numerical study on the hydrodynamics of bottom-hinged plate wave energy converters in regular and irregular waves. A parametric analysis of the plate width and height was performed. Both fully submerged and surface-piercing plates were considered. Two distinct models were developed based on linear hydrodynamics. The first one, in the frequency domain, assumes linear forces. The second one, incorporates fluid viscous and other nonlinear effects. For efficient wave power extraction, fully-submerged plates require amplitudes of motion larger than the surface-piercing ones. Such amplitudes may be unrealistically large close to resonance conditions, which in practice can negatively affect the efficiency. The adjustment of the plate natural period through the modification of the system inertia was tested without any significant improvement in the hydrodynamic efficiency. Resonance design criteria, used in heaving point absorbers, seem to be less effective in this case due to the large viscosity-induced damping and constraints in the plate displacement amplitude. Results show that a hydrodynamic efficient plate should have a width-to-water-depth ratio between 2 and 5, presenting a capture width per unit plate width of approximately 0.8 for regular waves and 0.65 for irregular waves, considering the most usual wave periods. © 2014 Elsevier Ltd.

Valverde P.S.,EDP Energias de Portugal | Sarmento A.J.N.A.,University of Lisbon | Alves M.,WavEC Offshore Renewables
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2013

Offshore Wind is one of the most promising renewable energy sources but the cost is still too high to be competitive. Optimizing the layout of a wind farm may help to improve the competitiveness, but it presents a significant engineering challenge. This paper presents the state of the art of offshore wind farm layout and identifies the main criteria used for its optimization with respect to a number of parameters such as the cost of energy and annual energy production. Used methodologies in farm design as well as key aspects of a wind farm that are subject to optimization will be analyzed. Available commercial software for wind farm design will also be presented and characterized and their limitations identified. The paper concludes with suggestion for further investigation. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).

Paparella F.,National University of Ireland, Maynooth | Monk K.,University of Plymouth | Winands V.,Duespan Wave Engineering | Lopes M.F.P.,WAVEC Offshore Renewables | Conley D.,University of Plymouth
IEEE Transactions on Sustainable Energy | Year: 2015

The real-time control of wave energy converters (WECs) requires the prediction of the wave elevation at the location of the device in order to maximize the power extracted from the waves. One possibility is to predict the future wave elevation by combining its past history with the spatial information coming from a sensor which measures the free surface elevation up-wave of the WEC. As an application example, this paper focuses on the prediction of the wave elevation inside the chamber of the oscillating water column (OWC) for the Pico OWC plant in the Azores, and two different sensors for the measurement of the free surface elevation up-wave of the OWC were tested. The study showed that the use of the additional information coming from the up-wave sensor does not significantly improve the linear prediction of the chamber wave elevation given by a forecasting model based only on the past values of the chamber wave elevation. © 2014 IEEE.

Melo A.B.,WavEC Offshore Renewables | Sweeney E.,Marine Institute of Ireland | Villate J.L.,Tecnalia
Marine Technology Society Journal | Year: 2013

Ocean energy is regarded as an important future source of energy generation in many countries for transition to a low-carbon future. While commercial interest in ocean energy is growing significantly at a global level, there are considerable investment costs and bottlenecks that will need to be overcome. Research and funds are spread over many different wave and marine current energy concepts under development, and there is still no technology convergence, in contrast to what happened in wind energy. Although an important marine energy resource, discussion of offshore wind energy is not included in this manuscript. This article focuses on the latest developments in ocean energy-in particular, open-sea testing facilities set up by several countries as a measure to encourage deployment and streamlining procedures-and gives an overview of projects going into the water this past year. In addition, the article highlights the importance of collaborative research and development on ocean energy projects and the unique role of the Ocean Energy Systems Implementing Agreement as an intergovernmental organization promoting the use of ocean energy (wave, marine currents, tidal, ocean thermal gradients and salinity gradients) for energy extraction.

Iturrioz A.,University of Cantabria | Guanche R.,University of Cantabria | Armesto J.A.,University of Cantabria | Alves M.A.,WavEC Offshore Renewables | And 2 more authors.
Ocean Engineering | Year: 2014

A simplified time-domain model for a fixed detached Oscillating Water Column (OWC) device is presented as a first step towards modeling a floating multi-chamber OWC device. The motion of a floating body in the time-domain is expressed by Cummins integro-differential equation, and based on it, water mass motion inside the chamber has been modeled here as a piston-like motion. Radiation, hydrostatic, excitation and viscous forces have been considered, as well as the added mass of the water in the chamber and the effect of the air pressure inside it. The equation of the floating body in the time domain has been approximated by a state-space method, which comes from the extension of the state-space system corresponding to the convolution integral of the radiation force. Experimental data have been used for model calibration and validation. Furthermore, the model has also been validated with a widely used Computational Fluid Dynamics (CFD) model (IH-2VOF). These show that the model presented is reliable and computationally efficient allowing for massive simulations for a statistical design or economic feasibility studies. © 2013 Elsevier Ltd. All rights reserved.

Debruyne Y.,WavEC Offshore Renewables | Alves M.,WavEC Offshore Renewables | Sarmento A.,WavEC Offshore Renewables
Renewable Energies Offshore - 1st International Conference on Renewable Energies Offshore, RENEW 2014 | Year: 2015

This paper introduces a novel numerical model to estimate the power production of farms of floating offshore wind turbines (FOWTs).A hydrodynamic model of the platforms which includes the influence of the turbines through dynamic table look-up was developed. The effect of the turbines’ wakes on the farm power production is also taken into account through Jensen’s theory. The first objective of this paper is to evaluate the accuracy of this model when used to estimate the power production of a single FOWT. For this purpose, and because of a lack of accessible field data, a code-to-code comparison is realized. Then, the effect of agglomeration is also evaluated to understand whether this model is suitable to estimate the dynamic power production of a farm of FOWTs. Finally, a short study-case shows how this model could help to plan and optimize the farm O&M strategy. © 2015 Taylor & Francis Group, London.

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