Browsing by Author "Soares, C. Guedes"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item On the assessment of extreme forces on a floating spar wind turbine(CRC Press, 2013-01-01) Nava, V.; Soares, C. Guedes; Arena, F.; RENOVABLES OFFSHOREA model based on the Quasi-Determinism theory is used in this paper to evaluate the most probable extreme excitations and their time histories on a 3-degree-of-freedom (i.e. surge, heave and pitch motions) model of a floating spar-type 5 MW wind turbine. Numerical simulations of forces in the time domain on the hull and tower of the structure have been carried out using FAST, accounting for the hydrodynamic characteristics of the floater by means of WAMIT. Sea wave forces and joint wave and wind forces have been calculated, under the hypothesis of typical wave surface elevation and wind velocity power density functions. In particular, different case studies have been chosen accounting for operational conditions of significant wave height and wind speed in a site in the Atlantic Ocean. An approach based on the Quasi-determinism theory is then used in order to assess, for each case study, the time history of all the components of the excitations when the maximum of one component of the forces occurs. Studies about the validity of the model and the qualitative and quantitative anomaly of the simulations with respect to the herein presented approach are also included.Item Speed control of oil-hydraulic power take-off system for oscillating body type wave energy converters(2016-11-01) Gaspar, José F.; Kamarlouei, Mojtaba; Sinha, Ashank; Xu, Haitong; Calvário, Miguel; Faÿ, François Xavier; Robles, Eider; Soares, C. Guedes; RENOVABLES EFICIENCIA ENERGETICA Y CIRCULARIDAD; RENOVABLES OFFSHOREThe variable displacement oil-hydraulic pumps for the Power Take-Off (PTO) of wave energy converters must work above 80% of maximum displacement in order to have an overall efficiency of approximately 94.5%. This is achieved by controlling their rotational speed when the oil-hydraulic power fluctuates in time. Three speed control strategies have been presented, the first fixing the maximum possible speed in each sea state, the second by slowly varying the pump speed between speed peak values and average ones, and the third by working with highly variable speed reference values. The worst pump efficiency is achieved with the first strategy while the best one with the third strategy. However, the first has less impact than the third one in the pump lifecycle. On the other hand, the second strategy is used to make a trade-off between pump efficiency and lifecycle. However, this paper presents a fourth speed control strategy, which is a hybrid of the second and third strategies. So, the objectives of this paper were to know if these strategies are implementable in a test rig and also on a new PTO concept and determining what modifications should be introduced in these PTO strategies and hardware. This paper also contributes with the application of new methodologies in this field of research for the modelling of pump efficiency and pressure control, such as Neuro-Fuzzy modelling and Fuzzy Logic control systems.