Browsing by Author "Nava, Vincenzo"
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Item Installation, operation and maintenance of offshore renewables(Institution of Engineering and Technology, 2019-01-01) Nava, Vincenzo; Ruiz-Minguela, Pablo; Pérez-Morán, Germán; Rodríguez-Arias, Raúl; Lopez-Mendia, Joseba; Villate-Martínez, José Luis; RENOVABLES OFFSHORE; Tecnalia Research & Innovation; GENERALThe chapter deals with the basic concepts of installation, operation and maintenance of offshore renewable energy systems. Whilst focus is given to the offshore wind industry, the extension to ocean energy (wave and tidal) offers a wider perspective on the major issues concerning the installation and maintenance. A reliability-based approach has been adopted for the analysis of the failures, providing an overview about the most common functional decomposition methodologies as well as logistic requirements for the different operations at the various stages of the lifetime of an offshore renewable project. The economic modelling of the operations, based on strategies for their planning, briefly completes the chapter.Item Mooring System Design Approach: A Case Study for MARMOK-A Floating OWC Wave Energy Converter(American Society of Mechanical Engineers (ASME), 2018) Touzon, Imanol; de Miguel, Borja; Nava, Vincenzo; Petuya, Victor; Mendikoa, Iñigo; Boscolo, Francesco; Tecnalia Research & Innovation; RENOVABLES OFFSHOREThis paper presents a methodology and a flowchart of steps to take for a, consistent and rapidly convergent design of catenary mooring systems. It is subsequently applied for a floating Oscillating Water Column WEC MARMOK-A developed by Oceantec Energías Marinas, in order to fulfill the technical requirements of such dynamic systems. The approach, based on the catenary equations, considers the water depth as a design scale factor for the mooring system, leading to an equivalent static mooring performance. In general, a mooring system configuration is described by the number and distribution of lines; thus, as a preprocess in the herein described procedure, a database is built for different line lengths. The main advantage of the procedure is that once that, after characterizing a mooring system configuration at a specific water depth with a specific line mass and axial stiffness, the database built can be used for any other water depth with any line mass and axial stiffness, accelerating the design optimization process. Mooring static properties are derived for a given material elastic modulus, lines’ mass and water depth. The mean offset and horizontal stiffness are afterwards derived with lines pretension and steady environmental forces (mean wave drift, current and wind) as well as maximum offset and characteristic line tensions. Finally, the process is applied for different lines pretensions to achieve an objective horizontal stiffness of the structure. The introduced procedure is presented through its application to the MARMOK-A device at a 90m depth site moored by means of a Karratu named mooring configuration. Results are presented in terms of total lines mass, device maximum expected excursion and required footprint for different horizontal stiffness and lines mass in order to give an insight of the impact on total plant cost indicators.Item Numerical Approaches for Loads and Motions Assessment of Floating WECs Moored by Means of Catenary Mooring Systems(Springer Science and Business Media B.V., 2022) Touzon, Imanol; Petuya, Victor; Nava, Vincenzo; Alonso-Reig, Maria; Mendikoa, Iñigo; Quaglia, Giuseppe; Gasparetto, Alessandro; Petuya, Victor; Carbone, Giuseppe; Tecnalia Research & Innovation; RENOVABLES OFFSHORETechnologies for harvesting offshore renewable energy based on floating platforms, such as offshore wind, wave and tidal energies, are currently being developed with the purpose of achieving a competitive cost of energy. The economic impact of the mooring system is significant within the total cost of such deployments, and large efforts are being carried out to optimize designs. Analysis of mooring systems at early stages generally require a trade-off between quick analysis methods and accuracy to carry out multi-variate sensitivity analyses. Even though the most accurate approaches are based on the non-linear finite element method in the time domain, these can result in being very time consuming. The most widely used numerical approaches for mooring line load estimates are introduced and discussed in this paper. It is verified that accurate line tension estimates require lines drag and inertia forces to be accounted for. A mooring and floating structure coupled model based on the lumped mass finite element approach is also discussed, and it is confirmed that the differences found in the coupled numerical model are mainly produced by the uncertainty on hydrodynamic force estimates on the floating structure rather than by the lumped mass method. In order to enable quick line tension estimates, a linearization of the structure and mooring coupled model is discussed. It shows accurate results in operational conditions and enables modal analysis of the coupled system.Item A numerical study on the hydrodynamic impact of device slenderness and array size in wave energy farms in realistic wave climates(2017) Penalba, Markel; Touzon, Imanol; Lopez-Mendia, Joseba; Nava, Vincenzo; Tecnalia Research & Innovation; RENOVABLES OFFSHOREThe future of wave energy converters lies in the design and realization of farms comprising of several devices, given the level of actual power flow for the individual devices and because of several operational issues. Therefore, not only the hydrodynamics of individual and isolated devices should be analysed, but interactions among devices within an array must also be carefully evaluated. In this paper, the authors attempt to parameterize the behaviour of small-, medium- and large-arrays of wave energy converters, in a particular staggered configuration, at four different locations characterized by realistic wave climates. The arrays studied in the present paper consist of heaving cylinders of different slenderness ratios. It turns out that for arrays of very short inter-device distances, regardless of the cylinder and array size, interactions are strong and lead to not negligible effects of destructive interference (total power reduction compared to the sum of isolated devices). Under these conditions, the bigger the array, the stronger the interactions and the higher the loss of power. However, a range of inter-device distances, referred to as intermediate region, where the power absorption is consistent and the interaction effect appears to be positive, has been found. This intermediate region is easily detectable for small arrays, but loses its ideal characteristics with the increase of the size of the array.Item Reducing variability in the cost of energy of ocean energy arrays(2019-09) Topper, Mathew B.R.; Nava, Vincenzo; Collin, Adam J.; Bould, David; Ferri, Francesco; Olson, Sterling S.; Dallman, Ann R.; Roberts, Jesse D.; Ruiz-Minguela, Pablo; Jeffrey, Henry F.; Tecnalia Research & Innovation; RENOVABLES OFFSHOREVariability in the predicted cost of energy of an ocean energy converter array is more substantial than for other forms of energy generation, due to the combined stochastic action of weather conditions and failures. If the variability is great enough, then this may influence future financial decisions. This paper provides the unique contribution of quantifying variability in the predicted cost of energy and introduces a framework for investigating reduction of variability through investment in components. Following review of existing methodologies for parametric analysis of ocean energy array design, the development of the DTOcean software tool is presented. DTOcean can quantify variability by simulating the design, deployment and operation of arrays with higher complexity than previous models, designing sub-systems at component level. A case study of a theoretical floating wave energy converter array is used to demonstrate that the variability in levelised cost of energy (LCOE) can be greatest for the smallest arrays and that investment in improved component reliability can reduce both the variability and most likely value of LCOE. A hypothetical study of improved electrical cables and connectors shows reductions in LCOE up to 2.51% and reductions in the variability of LCOE of over 50%; these minima occur for different combinations of components.Item Review of Systems Engineering (SE) Methods and Their Application to Wave Energy Technology Development(2020-10-20) Ruiz‐minguela, Pablo; Nava, Vincenzo; Hodges, Jonathan; Blanco, Jesús M.; RENOVABLES OFFSHOREThe design of effective and economically viable wave energy devices involves complex decision-making about the product based on conceptual design information, including stakeholder requirements, functions, components and technical parameters. The great diversity of concepts makes it extremely difficult to create fair comparisons of the relative merits of the many different designs. Conventional design approaches have proved insufficient to guarantee wave energy technologies meet their technical and economic goals. Systems engineering can provide a suitable framework to overcome the obstacles towards a successful wave energy technology. The main objective of this work is to review the well-established systems engineering approaches that have been successfully implemented in complex engineering problems and to what extent they have been applied to wave energy technology development. The paper first reviews how system information can be organised in different design domains to guide the synthesis and analysis activities and the definition of requirements and metrics, as well as the search for solutions and decision-making. Then, an exhaustive literature review on the application of systems engineering approaches to wave energy development is presented per design domain. Finally, a set of conclusions is drawn, along with some suggestions for improving the effectiveness of wave energy technology development.Item Technology-Agnostic Assessment of Wave Energy System Capabilities(2022-04-03) Ruiz-Minguela, Pablo; Blanco, Jesus M.; Nava, Vincenzo; Jeffrey, Henry; Tecnalia Research & Innovation; RENOVABLES OFFSHOREDeveloping new wave energy technologies is risky, costly and time-consuming. The large diversity of concepts, components and evaluation criteria creates a vast design space of potentially feasible solutions. This paper aims to introduce a novel methodology for the holistic assessment of wave energy capabilities in various market applications based on sound Systems Engineering methods. The methodology provides a consistent hierarchy of performance metrics relevant to the given system of reference, design activity and development stage under consideration as a means to scrutinise wave energy requirements. Full traceability of system requirements and performance metrics is then facilitated by multi-criteria decision tools and aggregation logic, respectively. The qualitative assessment in the case studies has resulted in very different rankings of System Drivers and Stakeholders for the two market applications considered. However, the Stakeholder Requirements and Functional Requirements present a small variation in the weights for the two application markets which results in a quantitative assessment with very similar Global Merit. Finally, the performance benchmark using the Commercial Attractiveness and Technical Achievability concepts enables a more objective comparison in the utility-scale and remote generation markets and a way to concentrate innovation efforts before proceeding to the next development stage.