5,103 research outputs found
Modelling, survivability, assessment, and control of moored wave energy conversion systems
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Parametric modelling of radiation forces for marine offshore renewable energy systems: A Loewner-based approach
No full textMarine offshore renewable energy systems are virtually always modelled by exploiting numerical solvers in the frequency domain, characterising the device hydrodynamics for a finite set of user-defined frequency components. A well-known limitation of this frequency-domain approach, nonetheless, is its inherently non-parametric nature, which complicates its use in time-domain simulation and modern control design. These tasks almost always require compact parametric models--typically in state-space form--to enable system analysis, synthesis, and real-time control implementation. Motivated by this, we present, in this paper, a frequency-domain parameterisation framework for representing the radiation dynamics of floating structures in marine renewable energy systems. The approach, based on the underpinning theory of Loewner matrices, is able to construct reduced-order parametric models directly from raw frequency-domain data, typically obtained from boundary element methods (BEMs). To demonstrate its effectiveness, a detailed case study is presented, based on a hybrid wind–wave energy converter, showcasing the accuracy and versatility of the proposed approach across two major renewable energy sectors. We show that the resulting models successfully capture complex radiation interactions while preserving the essential physical properties of radiation effects
On the optimal flywheel operation for inertial reaction mass wave energy conversion systems
No full textThis paper presents a direct transcription frame-work for optimising the operation of gyroscope-based iner-tial wave energy harvesters (WEH). In contrast to currently adopted procedures, we introduce a tailored optimal map as part of the total flywheel speed of the WEH, designed to maximise energy absorption. Since the target optimisation problem is infinite-dimensional, we derive a direct transcription process accordingly, exploiting tools from the field of moment-based theory. Following a formal derivation, the proposed framework is applied to a gyropendulum - based system, offering a numerical appraisal of the main characteristics underlying the methodology. We show that the procedure offered within this study is able to significantly enhance power absorption, hence contributing towards optimal energy-maximising operation of this family of systems
Powering Our Lives With the Ocean: From Waves to Electricity
Get PDFWe are surrounded by an incredible amount of energy every day! Energy powers our phones, video games, and even our cars. But where does this energy come from? Did you know it can come from waves? All the waves that you see from the beach carry an enormous amount of clean energy, and we can turn this energy into electricity that powers our days. This is achieved by using devices called wave energy converters. Just like a windmill produces power thanks to the blowing wind, wave energy converters generate electricity by harnessing the energy from incoming waves. Curious to know how it works? Dive into this article and discover the world of wave energy
Control synthesis via Impedance-Matching in panchromatic conditions: a generalised framework for moored systems
No full textThis study focuses on addressing the challenge of integrating the tangled mathematical model of the mooring system into an effective control synthesis. The presented synthesis framework utilises the impedance-matching technique to achieve the desired controller performance by adapting the control parameters to align with the dynamic characteristics of the moored wave energy device. By leveraging this technique, the simulation framework provides a means to effectively incorporate the intricate mooring dynamics into the control synthesis process. Furthermore, this paper aims to delve into the concept of defining a representative control action by examining the input-exciting force of the feedback-controlled system. Through a straightforward case study, the authors demonstrate the significant impact of the mooring on the system dynamics and underscore the applicability of the proposed simulation framework. Moreover, the paper verifies the importance of considering the controlled system’s exciting input when addressing control synthesis, particularly in panchromatic conditions
Mooring Influence on the Productivity of a Pitching Wave Energy Converter
Get PDFThe paper aims at investigate the effect of the mooring system on Wave Energy Converter productivity. In this case a pitch resonant device has been considered for the analysis. The non-linearities of the mooring system require generally a computational effort which cannot be considered in the early design stages of a WEC, and seldom the mooring systems are
totally included in WEC models. Driven by those considerations, a nonlinear mooring solvers, MoorDyn, has been used to carry out the effect of the mooring system on energy production. As first step a mooring model has been built to take familiarity with the solver and it has been validated against experimental data, through a static pull-out test and with irregular wave. Then, a semi-taut mooring model has been included in the hydrodynamic model
Input-Unknown Estimation for Arrays of Wave Energy Conversion Systems via LTI Synthesis
Get PDFThe incoming menace of global overheating and depletion of fossil fuels, highlight the need for alternative, renewable, energy sources. In this context, ocean wave energy has a massive potential to contribute towards global decarbonisation. In optimising wave energy converters (WEC) productivity, state-of-the-art, model-based optimal control techniques are fundamental to enhance energy absorption efficiency. However, the vast majority of these optimal approaches inherently require wave excitation force estimators. In particular, in array configurations, the interaction between WEC devices has to be taken into account to achieve a consistent excitation force estimation. In this paper, a linear time-invariant (LTI) estimation approach for a WEC farm is proposed. The technique proposed is based upon the so-called ‘simple and effective estimator’, recently presented in the WEC literature, which reformulates the wave excitation force estimation problem as a traditional tracking loop. The results show that the proposed approach provides accurate estimates of the exciting force for every device in the array, with almost no design effort, and mild computational requirements
Mooring System Design and Analysis for a Floating Offshore Wind Turbine in Pantelleria
Get PDFThe mooring system plays a key role in a floating offshore wind turbine: it connects the floating structure to its anchor on the seabed and it is designed to prevent the platform from drifting under the action of wind, waves and currents. The layout of the mooring system is strictly connected to the installation site: in the first place it depends on the bathymetry and the type of seabed which conditions the type of anchor that can be used; secondly by the wind and waves loads in extreme sea states.
To properly design the mooring system, three different configurations are proposed and discussed, respectively
adapting catenary, taut leg and semi-taut methodologies for a floating offshore wind turbine located near the island of Pantelleria, in Sicily. For each configuration, the Hexafloat foundation, developed by Saipem, is considered. Important design constraints such as how large the nominal sizes are, how long the mooring lines are, how far the anchor points are located, are demonstrated in detail. The material used will range from steel chains and wires to polyester ropes, to grant economically viable solutions
Perspectives on design of floating platforms for offshore airborne wind energy systems
Get PDFThe need for a fast transition towards electricity generation pushed large investments in highrisk, high-impact technologies such as floating Airborne Wind Energy Systems (AWES), which are expected to be highly cost efficient with respect to state-of-the-art offshore wind energy technology. Current research on the matter does not address the design challenge of a tailored floater, necessary to suit at most the unique features of such systems, and foster their industrial and commercial development. The goal of this study is to review the available solutions from traditional floating offshore wind energy systems, and hence to propose a straightforward concept, adapted from current designs, for the deployment of AWESs. Moreover, to provide
insights on how the geometrical parameters influence its motion response, a sensitivity study is performed, testing different design solutions against a wave scatter. In view of a cost-effective solution, a spar-like concept,
adapted to the specific needs of AWESs, is proposed. The sensitivity analysis suggests the need to adopt aspect ratio larger than 4 to effectively mitigate the pitch response; in addition, heave response emerges as a possible design constraint with large impact on the device’s costs
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