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Browsing Economia de Recursos - ER by Field of Science and Technology (FOS) "Engenharia e Tecnologia::Engenharia Eletrotécnica, Eletrónica e Informática"
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- Experimental investigation of a novel wave energy floating platform for hybrid wind-wave applications: The OctaPlatPublication . Mendonça, Nuno P.; Portillo, Juan C. C.ABSTRACT: The work presents the process of model design and testing and the experimental results for the OctaPlat, a new wave energy floating platform, conceived at IST/ULisboa. A physical model was designed on the basis of the Octaplat concept, which comprises five oscillating water columns (OWCs). The physical model design considered only three of the five OWCs due to infrastructure constraints and was made of acrylic material on a scale of 1:100th scale. The experimental campaign comprised free decay tests and tests under both regular and irregular wave conditions. Different power take-off systems for OWCs (impulse air turbines) were approximated through small orifices. Parameters such as RAO, dimensionless pressure, and the capture width ratio (CWR) were determined and analysed to understand the model performance under different conditions. Under regular waves, the results showed that the coupled hydrodynamic interaction between pitch and surge motions mainly affects the chambers located at the outer edges of the platform. Furthermore, the RAOs of the OWCs seem to be influenced by the natural coupled heave frequency, the natural frequencies of OWC1 and OWC3, and possibly the submultiple of the coupled heave natural frequency (k=1.5). Results also show that the different orifice plates considerably affect the CWR and the peaks' frequencies of its maximum values. Under irregular waves considering full-scale values, for a 2.5 m significant wave height, the peak pneumatic power reached 1.6 MW at 0.077 Hz with an equivalent rotor air turbine diameter of 6.3 m (that is, 30 mm orifice diameter) and 1.9 MW at 0.083 Hz with an equivalent rotor air turbine diameter of approximately 4 m (i.e., 20 mm orifice diameter). For a significant wave height of 3.4 m, the 30 mm orifice produced 3.6 MW at 0.077 Hz, while the 20 mm orifice reached 3.8 MW at 0.091 Hz. These results confirm the platform's feasibility for megawatt-scale wave energy conversion, supporting a key claim of this technology. The experimental results were compared with the numerical ones in terms of CWR. Good agreement was found between both, with a coefficient of determination (R^2) of about 0.94, and the relative difference between them was always less than 20%, except for a few peak deviations.
- Numerical investigation of a novel hybrid wind-wave system and its variable pneumatic chamber volume controlPublication . Marreiros, João; Portillo, Juan C. C.ABSTRACT: This work presents a numerical investigation of a novel control system for a new hybrid wave-wind energy floating platform. It comprises the design of a control system for controlling the variable pneumatic chamber volumes coupled with the hydrodynamics of the floating platform to maximise wave power production. The numerical model is developed in the object-oriented non-casual language Modelica, for which a new module for the control system was integrated into an existing package developed at IST/ULisboa. A sensitivity analysis of the main control parameters in terms of techno-economic parameters is performed and analysed. Results show that the envelope of control parameters’ values for increasing conversion efficiencies and power production is narrow, and an increase of about 30% was achieved with the best case compared with the base case. Moreover, it was observed that the variable volume of the pneumatic chambers shows significant variations on a part of the operational periods typical of the west of Portugal.
- On the Integration of Hydrogen in multipurpose wave energy platformsPublication . Mourão, Guilherme; Portillo, Juan C. C.ABSTRACT: his work presents an integrated numerical modelling approach implemented in Modelica language, which combines a multipurpose wave energy floating platform made of multiple oscillating water columns and the production and storage of green hydrogen in the same platform. The modelling approach comprised the simulation of the platform in WAMIT from which the hydrodynamic coefficients were obtained that serve as input for the integrated model implemented in Modelica. The Cherry Library for electrolysis processes and new modules developed in this work for storage were used and coupled to a model for the five-oscillating-water-column floating platform. The optimisation of hydrogen production based on hydrodynamic performance and energy conversion from waves off the coast of Portugal was conducted to identify optimal green hydrogen production parameters. The operational performance of the system was studied in detail for four representative days of the seasons to estimate optimal production of green hydrogen from ocean waves under those conditions. Dispatch of hydrogen and its conversion to other sustainable fuels, such as methanol or Ammonia are also discussed in terms of the total levelised cost of hydrogen (LCOH). A new tool developed at the National Laboratory for Energy and Geology was implemented to estimate costs. Results are still under progress.
- Techno-economic analysis of a novel hybrid wind-wave floating platform concept: The OctaPlatPublication . Rodrigues, M.B.V.A.; Portillo, Juan C. C.; Henriques, João; Gato, Luís; Mendonça, Nuno P.ABSTRACT: This work focuses on the techno-economic analysis of a novel floating offshore hybrid wind-wave platform. Floating multi-purpose platforms can potentially reduce costs associated with floating offshore wind. This work is based on the OctaPlat, a barge-type hybrid wind-wave floating platform designed at Instituto Superior Técnico, University of Lisbon. The paper presents the concept and numerical model of the floating wave platform, comprising five oscillating water column (OWC) wave energy converters, which was implemented in the object-oriented non-causal Modelica language. The OctaPlat configuration investigated here was equipped with the 15 MW IEA reference wind turbine, whose power output was computed using OpenFAST©. A sensitivity analysis of the geometry was performed, and the best performer design reached an average annual wave turbine power of 2.5 MW and a total wind-wave power of about 10.75 MW for a selected site off the west coast of Portugal. The levelized cost of energy (LCOE) was determined for a farm in the selected location. Various scenarios were assessed, and a Monte Carlo approach resulted in a probable value of LCOE of 135 €/MWh, with LCOE P90 and LCOE P10 values of 99 and 180 €/MWh, respectively. Experimental tests of the wave energy conversion systems were performed on a scale of 1:100, and comparisons with numerical results showed good agreement, with a coefficient of determination (R 2) of approximately 0.94 and relative differences were less than 20%, except for a few peak deviations. These results reveal the potential competitiveness of wind-wave multi-purpose platforms in floating offshore renewable energy projects.