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- Estimating the optimum size of a tidal array at a multi-inlet system considering environmental and performance constraintsPublication . González-Gorbeña Eisenmann, Eduardo; Pacheco, André; Plomaritis, Theocharis; Ferreira, Oscar; Sequeira, ClaudiaThis paper investigates the optimum tidal energy converter array density at a tidal inlet by applying surrogate-based optimisation. The SBO procedure comprises problem formulation, design of experiments, numerical simulations, surrogate model construction and constrained optimisation. This study presents an example for the Faro-Olhão Inlet in the Ria Formosa (Portugal), a potential site for tidal in-stream energy extraction. A 35 kW Evopod™ floating tidal energy converter from Oceanflow Energy Ltd. has been used for array size calculations considering two design variables: (1) number of array rows, and (2) number of tidal energy converter per row. Arrays up to 13 rows with 6–11 tidal energy converters each are studied to assess their impacts on array performance, inlets discharges and bathymetry changes. The analysis identified the positive/negative feedbacks between the two design variables in real case complex flow fields under variable bathymetry and channel morphology. The non-uniformity of tidal currents along the array region causes the variability of the resource in each row, as well as makes it difficult to predict the resultant array configuration interactions. Four different multi-objective optimisation models are formulated subject to a set of performance and environmental constraints. Results from the optimisation models imply that the largest array size that meets the environmental constraints is made of 5 rows with 6 tidal energy converter each and an overall capacity factor of 11.6% resulting in an energy production of 1.01 GWh year−1. On the other hand, a higher energy production (1.20 GWh year−1) is achieved by an optimum array configuration, made of 3 rows with 10 tidal energy converters per row, which maximises power output satisfying environmental and performance restrictions. This optimal configuration permits a good level of energy extraction while having a reduced effect on the hydrodynamic functioning of the multi-inlet system. These results prove the suitability and the potential wide use of the surrogate-based optimisation method to define array characteristics that enhance power production and at the same time respect the environmental surrounding conditions.
- Marine energy prototype testing at Ria FormosaPublication . Pacheco, André; Gorbeña, Eduardo; Sequeira, ClaudiaEconomic growth and increasing human demands are among the most important factors for growing world energy consumption. Energy is present in everything around us: it is a property of all objects and is essential to life. We find various forms of energy in the world around us. When plants grow, for example, they are converting sunlight energy into chemical energy in the form of carbohydrates and other compounds stored in your body (e.g. sugars). The form of energy that man uses most today is the chemical energy contained in fossil fuels, such as oil, coal and natural gas. About 80% of the energy we use comes from these sources. However, these sources are very polluting, since their use releases substances harmful to the environment and to public health. An example of this is the increased concentration of greenhouse gases such as carbon dioxide (CO2) in the atmosphere, which is a cause of climate change. In addition to pollutants, these sources of energy are non-renewable, which means that they are being consumed at a faster rate than is necessary for their production, so their availability is decreasing. Due to the increasing oil and natural gas prices, reduced fuel reserves and the requirement for reduced CO2 emissions to avert climate change, the use of alternative energy sources is both financially unavoidable and environmentally preferable (UN, 2015). Hence, generating renewable energy is nowadays one of the most relevant endeavours for research. Countries worldwide now recognise the need to incorporate renewable energy resources in their energy policy as an alternative to finite fossil fuel resources in order to achieve future energy security and to mitigate the effects of climate change induced by human activities. Today, renewable energy is now firmly entrenched as the world's fastest growing energy sector (IEA, 2017).
- Surrogate-based optimization of tidal turbine arrays: a case study for the Faro-Olhão inletPublication . G-Gorbeña, Eduardo; Pacheco, André; Plomaritis, Theocharis; Ferreira, Oscar; Sequeira, Claudia; Moura, TheoThis paper presents a study for estimating the size of a tidal turbine array for the Faro-Olhão Inlet (Potugal) using a surrogate optimization approach. The method compromises problem formulation, hydro-morphodynamic modelling, surrogate construction and validation, and constraint optimization. A total of 26 surrogates were built using linear RBFs as a function of two design variables: number of rows in the array and Tidal Energy Converters (TECs) per row. Surrogates describe array performance and environmental effects associated with hydrodynamic and morphological aspects of the multi inlet lagoon. After validation, surrogate models were used to formulate a constraint optimization model. Results evidence that the largest array size that satisfies performance and environmental constraints is made of 3 rows and 10 TECs per row.
- Assessing the effects of Tidal Energy Converter array size on hydrodynamics of Ria Formosa (Portugal)Publication . G-Gorbeña, Eduardo; Pacheco, André; Plomaritis, Theocharis A.; Sequeira, ClaudiaThis paper investigates the effects of Tidal Energy Converter (TEC) array size at a tidal channel on flood/ebb discharges at multi-inlet coastal lagoon by applying numerical modelling. The paper presents a case study for the Faro-Olhão inlet in the Ria Formosa (Portugal), a potential site for tidal in-stream energy extraction. Arrays of up to 11 rows with 5 TECs each were studied to assess impacts on inlets discharges changes. For the particular cases assessed the results show that tidal energy extraction will have a greater impact on Ancão and Armona inlets discharges together with the Faro-Olhão inlet. Future work is directed to include impacts on sediment dynamics and optimise TEC array size as a function of multiple design variables subject to environmental constraints.
- Analysis of the efficiency of wind turbine gearboxes using the temperature variablePublication . Sequeira, Claudia; Pacheco, André; Galego, P.; González-Gorbeña Eisenmann, EduardoThe aim of this paper is to evaluate how lubricant selection affects gearbox efficiency and overall energy production by analysing real data from wind farms, monitored and controlled by a Supervisory Control and Data Acquisition (SCADA system). The turbines analysed worked with two or more oil types for the same amount of hours, which allowed to establish relations between the active power curves and wind velocity; oil temperature inside gearboxes and wind velocity; and oil temperature inside gearboxes and active power production. The results of this study evidenced a direct relation between oil characteristics and energy efficiency i.e. gearboxes working with mineral oil perform better then gearboxes working with synthetic oils. Those differences can be significant in terms of active power production. Also, it was observed oil degradation as function of temperature increase, with changes on viscosity, which reveals that temperature behaviour along the active power curve is strongly related to oil' characteristics. (C) 2018 Elsevier Ltd. All rights reserved.
- Deployment characterization of a floatable tidal energy converter on a tidal channel, Ria Formosa, PortugalPublication . Pacheco, André; G-Gorbeña, Eduardo; Plomaritis, Haris; Garel, Erwan; Gonçalves, J. M. S.; Bentes, L.; Monteiro, P.; Afonso, Carlos; Oliveira, Frederico; Soares, C.; Zabel, F.; Sequeira, ClaudiaThis paper presents the results of a pilot experiment with an existing tidal energy converter (TEC), Evopod 1 kW floatable prototype, in a real test case scenario (Faro Channel, Ria Formosa, Portugal). A baseline marine geophysical, hydrodynamic and ecological study based on the experience collected on the test site is presented. The collected data was used to validate a hydro-morphodynamic model, allowing the selection of the installation area based on both operational and environmental constraints. Operational results related to the description of power generation capacity, energy capture area and proportion of energy flux are presented and discussed, including the failures occurring during the experimental setup. The data is now available to the scientific community and to TEC industry developers, enhancing the operational knowledge of TEC technology concerning efficiency, environmental effects, and interactions (i.e. device/environment). The results can be used by developers on the licensing process, on overcoming the commercial deployment barriers, on offering extra assurance and confidence to investors, who traditionally have seen environmental concerns as a barrier, and on providing the foundations whereupon similar deployment areas can be considered around the world for marine tidal energy extraction.
- An evaluation of offshore wind power production by floatable systems: a case study from SW PortugalPublication . Pacheco, André; González-Gorbeña Eisenmann, Eduardo; Sequeira, Claudia; Jerez, S.The challenge for floating offshore wind structures is to reduce costs. The industry needs a wind turbine support solution that can be fabricated and deployed from existing shipyards and port facilities, while investors need accurate estimations and forecasts of wind resources and quantified information on the inherent variability in wind power generation. This paper merges hindcast model data with observed in situ data to characterize the wind resource potential off the SW coast of Portugal. The validation procedure adopted allows an estimation of the coefficient used for power-law extrapolation of the wind measurements and a reduction in the uncertainty of the power density calculations. Different types of turbine model are compared and site metocean characteristics are examined as a basis for choosing between existing wind floatable solutions. The calculations using four different wind turbine models indicate a preferable installed capacity of 3-4 MW for a hub height of 90-120 m (i.e., representing the best capacity factor and load hours). There is a consistent difference in power density of about 20% from a location 5 nautical miles (NM) offshore to one 10 NM offshore, which represents an increment of 20% -25% in energy production depending on the particular wind turbine capacity factor. (C) 2017 Elsevier Ltd. All rights reserved.
- Assessing the effects of Tidal Energy Converter array size on hydrodynamics of Ria Formosa (Portugal)Publication . González-Gorbeña, Eduardo; Pacheco, André; Plomaritis, Theocharis A.; Sequeira, Claudia