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- Numerical and experimental analysis of a hybrid wind-wave offshore floating platform’s hullPublication . Hallak, Thiago S.; Gaspar, José F.; Kamarlouei, Mojtaba; Calvário, Miguel; Gonçalves Cavaco Mendes, Mário José; Thiebaut, Florent; Guedes Soares, CarlosThis paper presents a study regarding a novel hybrid concept for both wind and wave energy offshore. The concept resembles a semi-submersible wind platform with a larger number of columns. Wave Energy Devices such as point absorbers are to be displayed around the unit, capturing wave energy while heaving and also enhancing the stability of the platform. In this paper, a first numerical study of the platform’s hull, without Wave Energy Converters, is carried out. Experiments in wave basin regarding the same unit have been conducted and the results are presented and compared to the numerical ones. Both stability and seakeeping performances are assessed and compared.
- Experimental study of an onshore dual chamber oscillating water column devicePublication . Gadelho, Jorge; Rezanejad, Kourosh; Guedes Soares, Carlos; Santos, João Alfredo; Anastas, Gael; Fortes, ConceiçãoA wave flume is used to study a scaled model of a stepped bottom dual-chamber Oscillating Water Column (OWC) installed onshore. Compared to traditional single-chamber OWCs, the use of dual-chambers is expected to widen the range of sea states in which the OWC is more efficient, and the step, in front of the first chamber, boosts the capturing energy capacity of the device. The Power Take-Off (PTO) system is modelled as an air opening in the pneumatic chambers. Several experiments combining regular incident waves and PTO damping conditions are performed. Results of the amplitudes of the free surface elevations inside the chambers show that the device can amplify the incident wave amplitude up to 1.57 times in chamber 2. Results of the primary ef ficiency show that the device is highly dependent on the PTO damping characteristics and can reach around 40% for a wide range of wave periods. Results of the reflection analysis show that the reflection coefficient is also dependent on the PTO damping characteristics but remain lower than 0.6 for all the studied cases. Sloshing phenomenon (mostly in the cross-section direction) was observed for a wavelength close to the cross-section dimension, impacting negatively on the device pneumatic performance.
- On the experimental study of a concentric wave energy array adapted to an offshore floating platformPublication . Kamarlouei, Mojtaba; Gaspar, José F.; Calvário, Miguel; Hallak, Thiago S.; Mendes, Mário J. G. C.; Thiebaut, Florent; Guedes Soares, CarlosExperimental results of the dynamics of a small scale concentric wave energy converter array adapted to a floating offshore platform are presented. A small scale prototype is tested without and with twelve conical heaving point absorbers. The free decay and regular wave tests are carried out in an ocean basin to understand the hydrodynamic interactions between various elements of the floating offshore platform and wave energy converter array. Meanwhile, the heave motions of the buoys are observed in regular waves with and without dampers for the initial estimation of power take-off damping as a pitch control module. The results show the improvements in heave, pitch, and roll performance of the platform due to the interaction between the buoys and platform.
- Fire safety barrier availability analysisPublication . Sobral, José; Carlos Guedes SoaresThis paper shows several ways to analyse the performance of a safety barrier, depending on the objective to be achieved and present a method to analyse binary components usually present on sensor systems of safety barriers. An application example of a water-based fire system is presented and the Probability of Failure on Demand (PFD) of the sensor system is determined based on the analysis of pressure switches installed in this safety barrier. The knowledge of such information will allow the determination of safety barrier’s availability.
- Numerical and experimental study of ship-generated wavesPublication . Rodrigues, Sara; Guedes Soares, Carlos; Santos, João AlfredoThis paper presents the results of the numerical and experimental study on the propagation of ship-generated waves. In the numerical modified FUNWAVE code, which is able to reproduce most of the phenomena involved in wave propagation, the ship is represented by a moving pressure distribution function at the free surface. The experimental tests were carried out with a ship model at a 1: 50 scale that moving at constant speed across a constant depth region. The values of wave heights obtained in the scale ship model 1: 50 were used to compare with the predictions of wave heights provided by the numerical code. The comparison of the results obtained by the numerical code and the experimental tests shows very similar values for the maximum wave height.
- Review on hardware-in-the-loop simulation of wave energy convertersPublication . Gaspar, J. F.; Pinheiro, R. F.; Kamarlouei, M.; Guedes Soares, Carlos; Gonçalves Cavaco Mendes, Mário JoséThis paper presents a review of the state-of-the-art of the Hardware-In-The-Loop (HIL) technique applied to the development of wave energy converters (WEC) and power take-off systems (PTO). The presentation discusses existing frameworks and the technologies involved. In addition, a case study is discussed in order to exemplify the HIL concept applied to a WEC-PTO.
- Experimental analysis of wave energy converters concentrically attached on a floating offshore platformPublication . Kamarlouei, M.; Gaspar, José; Calvário, Miguel; Hallak, T. S.; Mendes, Mário J. G. C.; Thiebaut, F.; Soares, Carlos GuedesThis paper presents an initial experimental study of wave energy converters concentrically arranged and attached on a floating offshore platform model. The 1:27 scale model, has been designed, built and tested, in two main situations, without and with twelve cone shape wave energy converters. To simulate the power take-off system in each wave energy converter, rotational friction dampers have been installed on the joints of the floaters arms to the platform deck. The experimental results show that the interaction between buoys and platform have a positive effect on the platform heave and pitch motions. However, the reduction in heave and pitch motions of the platform, after installing the wave energy converter array, depends on the damping of the equivalent power take-off system. Thus, the effect of dampers in the motion of buoys is presented to allow an initial understanding of the required damping range of the power take-off system and related control strategies.
- Experimental study of wave energy converter arrays adapted to a semi-submersible wind platformPublication . Kamarlouei, M.; Gaspar, José; Calvário, Miguel; Hallak, T. S.; Mendes, Mário J. G. C.; Thiebaut, F.; Guedes Soares, CarlosThe design of an offshore wind turbine floating platform seeks to minimize platform pitching motions that otherwise generate large accelerations and loads on the turbine, nacelle and blades, and decrease their lifetime. This objective is harder to achieve as the upscaling to more powerful wind turbines amplify the effects of pitching motions since the wind turbines’ height and mass are higher. Thus, innovative solutions to control the pitching motions should be developed. This study presents a solution based on a concentric array of wave energy converters which was originally designed to be attached on a floating platform to generate wave energy. Meanwhile, it was found that the concept may provide bigger restoring moments for platforms, amplified by its lever type arms, which are useful to control the pitching motions. Thus, a wind thrust simulator is adapted to the original experimental model and tests performed to understand the advantage of using these converters in the control of the pitching motions of a wind turbine platform. The experimental results indicate that platform motions are controllable by the wave energy converters however must be optimized to achieve better performance. These results also provide some design knowledge to test the concept at bigger rated power wind turbines.
- Preventive maintenance of critical assets based on degradation mechanisms and failure forecastPublication . Sobral, José; Guedes Soares, CarlosWhen dealing with critical physical assets it is very important to monitor some parameters just to observe and predict the potential time to failure and thus establish a preventive maintenance activity avoiding the unwanted failure occurrence and its consequences. According to periodic (or continuous) data gathered along the time concerning selected parameters it is possible to observe tendencies and determine time to failure, assuming a pre-defined value as the critical one, corresponding to asset failure. The present paper deals with this type of condition monitoring outlining the importance of predicting time to failure and illustrating it with an example where the evolution of a degradation parameter on time for several similar assets is observed and, based on that, the time to failure is determined, allowing to establish the right moment for maintenance for these type of assets operating in these conditions.
- Prototyping and wave tank testing of a floating platform with point absorbersPublication . Kamarlouei, Mojtaba; Gaspar, José F.; Calvário, M.; Hallak, Thiago S.; Soares, Carlos Guedes; Mendes, Mário J. G. C.; Thiebaut, FlorentThe main aim of this paper is to present the experimental results of a concept of a platform, with several point energy absorbers. A floating circular array of point absorbers, in 1-27 scale, was tested in the wave tank. The hydrodynamic behavior of the platform was studied in different configurations. Moreover, the performance of the platform was assessed in different sea states with and without point absorbers attached to the platform.