Avalon Submersible Support Structure: Final Project Report

The MBMM, represented by our sponsor Bob McCay, is currently looking for a new way to support the Deep Submergence Rescue Vehicle (DSRV), Avalon, that they have on display. The DSRV is currently sitting on a Short Haul Vehicle (SHV) trailer and the total weight (32 tons) is currently being supported by the SHV’s tires. This is a source of concern for the MBMM due to the weathering the tires have undergone combined with the amount of time that they have been supporting the weight. The MBMM is looking for a support structure that will take the weight off of the tires so that they can be removed at their convenience. Our goal for this senior project, under the direction of our advisor Eileen Rossman, was to design a structure that will allow the museum to support the submersible, keep as much of it visible for viewing as possible, and allow the museum to transport it to its final location at their proposed Interpretive Center in the future. First, background research was conducted regarding both submersible support structures, and other types of structures that support large, heavy objects. Next, idea generation sessions were held, and potential solutions were selected using a combination of go/no-go evaluation, pugh matrices, and a weighted decision matrix. The decision regarding the final design was left to the MBMM, as our weighted decision matrix indicated that aesthetics was the final deciding factor. After the final design was selected, extensive analysis was conducted to determine whether it was feasible. To validate the design, we built a steel scaled model of the most critical portion of our design and tested it under the anticipated load case. We also built a wooden, full-scale model of our design for geometric testing. Our testing on the steel scaled model indicated that the design did not meet the strict seismic requirement in our engineering specifications. After discussing this with the MBMM, they agreed to loosen the seismic requirement. However, before manufacturing begins, we recommend that the MBMM have a structural engineer look over our design and calculations, and verify that our structures will not fail in the event of an earthquake

Technical-economic analysis, modeling and optimization of floating offshore wind farms

The offshore wind sector has grown significantly during the last decades driven by the increasing demand for clean energy and to reach defined energy targets based on renewable energies. As the wind speeds tend to be faster and steadier offshore, wind farms at sea can reach higher capacity factors compared to their onshore counterparts. Furthermore, fewer restrictions regarding land use, visual impact, and noise favors the application of this technology. However, most of today's offshore wind farms use bottom-fixed foundations that limit their feasible application to shallow water depths. Floating substructures for offshore wind turbines are a suitable solution to harness the full potential of offshore wind as they have less constraints to water depths and soil conditions and can be applied from shallow to deep waters. As several floating offshore wind turbine (FOWT) concepts have been successfully tested in wave tanks and prototypes have been proven in open seas, floating offshore wind is now moving towards the commercial phase with the first floating offshore wind farm (FOWF) commissioned in 2017 and several more are projected to be constructed in 2020. This transition increases the need for comprehensive tools that allow to model the complete system and to predict its behavior as well as to assess the performance for different locations. The aim of this thesis is to analyze from a technical and economic perspective commercial scale FOWFs. This includes the modeling of FOWTs and the study of their dynamic behavior as well as the economic assessment of different FOWT concepts. The optimization of the electrical layout is also addressed in this thesis. The first model developed is applied to analyze the performance of a Spar type FOWT. The model is tested with different load cases and compared to a reference model. The results of both models show an overall good agreement. Afterwards, the developed model is applied to study the behavior of the FOWT with respect to three different offshore sites. Even at the site with the harshest conditions and largest motions, no significant loss in energy generation is measured, which demonstrates the good performance of this concept. The second model is used to perform a technical-economic assessment of commercial scale FOWFs. It includes a comprehensive LCOE methodology based on a life cycle cost estimation as well as the computation of the energy yield. The model is applied to three FOWT concepts located at three different sites and considering a 500MW wind farm configuration. The findings indicate that FOWTs are a high competitive solution and energy can be produced at an equal or lower LCOE compared to bottom-fixed offshore wind or ocean energy technologies. Furthermore, a sensitivity analysis is performed to identify the key parameters that have a significant influence on the LCOE and which can be essential for further cost reductions. The last model is aimed to optimize the electrical layout of FOWFs based on the particle swarm optimization theory. The model is validated against a reference model at first and is then used to optimize the inter-array cable routing of a 500MW FOWF. The obtained electrical layout results in a reduction of the power cable costs and a decrease of the energy losses. Finally, the use of different power cable configurations is studied and it is shown that the use of solely dynamic power cables in comparison to combined dynamic and static cables results in decreased acquisition and installation costs due to the avoidance of cost-intensive submarine joints and additional installation activities.El sector eólico marino ha crecido significativamente durante las últimas décadas impulsado por la creciente demanda de energía limpia. Los parques eólicos en el mar pueden alcanzar factores de capacidad más altos en comparación a los parques eólicos en la tierra debido a que las velocidades del viento tienden a ser más altas y constantes en el mar. Ademas, existen menos restricciones con respecto al uso de la tierra, el impacto visual y el ruido. Sin embargo, la mayoría de los parques eólicos actuales utilizan subestructuras fijas que limitan su aplicación factible a aguas poco profundas. Las subestructuras flotantes para turbinas eólicas marinas (FOWTs en inglés) son una solución adecuada para aprovechar todo el potencial de la energía eólica, ya que tienen menos restricciones para las profundidades del agua y el fondo marino. Dado que varios prototipos de FOWTs se han probado con éxito en el mar, la industria ahora esta entrando a la fase comercial con el primer parque eólico flotante (FOWF en inglés) operativo y se proyecta que se pondrán en marcha más en los próximos anos. Esta transición aumenta la necesidad de herramientas integrales que permitan modelar el sistema completo y predecir su comportamiento, así como evaluar el rendimiento para diferentes lugares. El objetivo de esta tesis es analizar desde una perspectiva técnica y económica los FOWFs a escala comercial. Esto incluye el modelado de FOWTs, el estudio de su comportamiento dinámico, y la evaluación económica de diferentes conceptos. La optimización del diseño eléctrico también se aborda en esta tesis. El primer modelo desarrollado se aplica para analizar el rendimiento de un FOWT tipo Spar. El modelo se prueba con diferentes tipos de carga y se compara con un modelo de referencia. Los resultados de ambos modelos muestran una buena concordancia. Posteriormente, el modelo se aplica para estudiar el comportamiento con respecto a tres lugares diferentes. Los resultados muestran que incluso en el sitio con las condiciones más severas, no se mide ninguna pérdida significativa en la generación de energía, lo que demuestra el buen rendimiento de este concepto. El segundo modelo se utiliza para realizar una evaluación técnico-económica de los FOWF a escala comercial. Esto incluye una metodología integral del costo nivelado de energía (LCOE en ingles). El modelo se aplica a tres conceptos de FOWTs ubicados en tres lugares diferentes y considerando un parque eólico de 500MW. Los resultados indican que los FOWTs son una solución altamente competitiva y que la energía se puede producir con un LCOE igual o inferior en comparación con los parques eólicos con subestructuras fijas o las tecnologías de energía oceánica. Asimismo, se realiza un análisis de sensibilidad para identificar los parámetros claves que tienen una influencia significativa en el LCOE y que pueden ser esenciales para reducciones de costos. El último modelo se aplica para optimizar el diseño eléctrico en función de la teoría de optimización por enjambre de partículas. Inicialmente el modelo se valida contra un modelo de referencia y luego se utiliza para optimizar la conexión de los cables entre los FOWTs. El diseño eléctrico obtenido da como resultado una reducción de los costos de cables y una disminución de las pérdidas de energía. Finalmente, se estudia el uso de diferentes configuraciones de cables y se demuestra que el uso de cables únicamente dinámicos en comparación con los cables dinámicos y estáticos combinados da como resultado una disminución de los costos de adquisición e instalación debido a que evitan la necesidad de juntas submarinas costosas y costos adicionales de instalación.Postprint (published version

Probabilistic assessment of floating wind turbine access by catamaran vessel

In this work, it is evaluated the accessibility of a floating platform, by means of a catamaran vessel equipped with a fender. The two bodies are modelled as a constrained multi-body system in the frequency domain. Transfer functions are calculated for the motions and forces of the system. Access is possible when no slip conditions occur at the fender, and when the relative rotations between the two bodies are within certain tolerance limits. Four response variables are defined to impose such conditions. In a short-term sea state the extreme maximum crest height of these variables is computed, assuming that response crest heights follow a Rayleigh distribution. Each of the extreme values is compared to a specific threshold, to determine whether access is possible or not. Accessibility is calculated for a sample platform located off the coast of Scotland using hindcast data for the period 1980-2013. Average accessibility resulted to be 23.7%. A strong seasonality is ascertained, together with a large variation of accessibility, due to the variability of wave climate.The authors would like to acknowledge the projects “OceaNET”, which received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 607656, and “Plataformas multiuso para aplicaciones offshore” of the University of Cantabria (code: 56.JS05.64061)

Dynamic Model for Simulating Motion of the Right Ventricle

This report documents all the research, ideation, and mockups used to determine right ventricle motion and develop a system capable of reproducing that motion on a tissue sample. The model is intended for evaluating anchoring systems being developed by Edwards Lifesciences for use with tricuspid valve therapies. Several design solutions were considered for the primary functions of recreating motion of the right ventricle and attaching tissue to the device. From these ideas a primary means of producing motion and attaching tissue was selected. These ideas were then developed over the course of a school year to become the final system hardware delivered to the project sponsor. This document covers the design process including multiple iterations both in CAD and of structural prototypes. The document concludes by discussing the final hardware and the next steps proposed to improve upon the final design

Optimization of a Lightweight Floating Offshore Wind Turbine with Water-Ballast Motion Mitigation Technology

Floating offshore wind turbines are a promising technology to address energy needs utilizing wind resources offshore. The current state of the art is based on heavy, expensive platforms to survive the ocean environment. Typical design techniques do not involve optimization because of the computationally expensive time-domain solvers used to model motions and loads in the ocean environment. However, this project uses an efficient frequency domain solver with a genetic algorithm to rapidly optimize the design of a novel floating wind turbine concept. The concept utilizes liquid ballast mass to mitigate motions on a lightweight post-tensioned concrete platform, with a target of half the levelised cost of energy of current technologies. This thesis will present the optimization methodology for the cruciform hull design with tuned mass dampers and IEA 15 MW turbine. The need for lowering the levelised cost of energy of offshore wind technologies is explained, along with the challenges of reducing cost in these floating systems. A method utilizing a staged constraint handling technique coupled with a genetic algorithm is developed, encompassing input variable selection, hydrostatic constraints, and dynamic constraints. Finally, results of the optimization are presented, including wind and wave conditions, hull and turbine specifications, and convergence criteria. Finally, a conclusion on the results of the optimization is made and suggestions for future work are presented

The effects of wind-induced inclination on the dynamics of semi-submersible floating wind turbines in the time domain

This study focusses on the coupling effects arising from the changes in the hydrodynamic behaviour of a semi-submersible floating wind turbine when it undergoes large inclinations under wind loading. By means of a range of time-domain simulations, it is shown that both the hull geometric nonlinearity effect and the alteration of viscous hydrodynamic forces can significantly affect the dynamics of a typical floating wind turbine operating in waves at rated conditions. The consequences of said effects for both aligned and misaligned wind and waves are explored. In general terms inclinations are found to increase motions, where the modes that are more affected depend on the relative direction between incident wind and waves. Understanding the sources of aero-hydrodynamic coupling is key to providing sound design and modelling guidelines for the coming generation of floating wind turbines

Energy Demonstration Trailer: Spreading Renewable Energy and Energy Efficiency throughout Namibia

Namibia has few power plants to produce electricity of its own and imports 50% of its electricity from South Africa. For this reason, Namibia will need to begin researching and developing other methods of energy generation. Renewable energy (RE) and energy efficiency (EE) are alternatives that could alleviate Namibia\u27s energy problem. Unfortunately members of both rural and urban communities have very little knowledge about RE and EE and therefore are unable to employ any of these technologies or techniques to conserve energy. In an effort to disseminate information on these topics and find new energy efficient materials, four students from Worcester Polytechnic Institute in conjunction with Habitat Research and Development Centre designed a demonstration trailer, which will be used to travel to settlements, schools, villages and farms spreading RE and EE concepts and products. This proposal provides background information and methodology for creating the trailer as well information on RE and EE technologies and materials

Design of a Greywater-Fed Hydroponics System

To combat issues of local water insecurity, a hydroponics system was designed in partnership with LEAP 5 High School in Jane Furse, South Africa. Climate change, increasing human population, and continued environmental degradation all threaten access to clean drinking water. Approximately seventy percent of all freshwater is used for agriculture globally, thus threatening food security especially in developing countries where access to water is potentially volatile. The hydroponics garden system utilizes sustainable materials, a self-monitoring temperature controls system, and greywater input, to act as an educational tool for students and significantly reduce freshwater use compared to traditional, in-ground agriculture. An education plan accompanies the implementation of the system to provide an avenue for community engagement and encourage the adoption of alternative, water-saving farming methods. The hydroponics system was developed by observing the strengths of existing hydroponics applications in commercial and educational institutions. The successes of established systems guided rapid prototyping of grow beds, shading structure, and greywater filter. The fully built system reflected all major subsystems and was used to test the effectiveness of a hydroponics garden compared to a traditional soil garden, and the growth of lettuce plants confirmed the benefits of hydroponics. The hydroponics method of farming was found to produce triple the lettuce per the same volume of water when compared with soil faring. Additionally, 30% less energy was required to operate the hydroponics system and the cost of materials was decreased 50% compared to past student projects and existing systems commercially available systems. The greywater-fed hydroponics system proves that an inexpensive, durable design displays significant advantages over standard, soil farming. Educational assembly manuals and tailored education modules designed for the LEAP 5 High School will aid in the adoption of a potentially disruptive farming method to an agriculturally dependent region

Assessment and Nonlinear Modeling of Wave, Tidal and Wind Energy Converters and Turbines

Offshore renewable energy (ORE) sources, such as offshore wind turbines, wave energy converters, and tidal and current turbines, have experienced rapid growth in the past decade. The combination of wave, wind, and current energy devices in hybrid marine platforms that use synergies through proper combinations has been a recent scientific focus. The new concepts and structures being investigated require developing new design and analysis approaches that implement novel numerical modeling tools and simulation methods, thus advancing science, technology, and engineering. ORE structures may be subject to complex loads and load effects, which demand comprehensive and accurate numerical modeling representations of the physics underpinning the problem. Important factors that affect design, functionality, structural integrity, and performance of offshore structures include (but are not limited to): fluid–structure interactions, controller actions, intense dynamic effects, nonlinear loadings, extreme and harsh weather conditions, and impact pressure loads. Furthermore, these factors cannot be considered in isolation, since each factor is potentially coupled with another, requiring fully coupled models. To enable further growth in reliable ORE technologies, more advanced numerical tools and nonlinear modeling are needed

Assessment and Nonlinear Modeling of Wave, Tidal and Wind Energy Converters and Turbines

The Special Issue “Assessment and Nonlinear Modeling of Wave, Tidal, and Wind Energy Converters and Turbines” contributes original research to stimulate the continuing progress of the offshore renewable energy (ORE) field, with a focus on state-of-the-art numerical approaches developed for the design and analysis of ORE devices. Particularly, this collection provides new methodologies, analytical/numerical tools, and theoretical methods that deal with engineering problems in the ORE field of wave, wind, and current structures. This Special Issue covers a wide range of multidisciplinary aspects, such as the 1) study of generalized interaction wake model systems with elm variation for offshore wind farms; 2) a flower pollination method based on global maximum power point tracking strategy for point-absorbing type wave energy converters; 3) performance optimization of a Kirsten–Boeing turbine using a metamodel based on neural networks coupled with CFD; 4) proposal of a novel semi-submersible floating wind turbine platform composed of inclined columns and multi-segmented mooring lines; 5) reduction of tower fatigue through blade back twist and active pitch-to-stall control strategy for a semi-submersible floating offshore wind turbine; 6) assessment of primary energy conversion of a closed-circuit OWC wave energy converter; 7) development and validation of a wave-to-wire model for two types of OWC wave energy converters; 8) assessment of a hydrokinetic energy converter based on vortex-induced angular oscillations of a cylinder; 9) application of wave-turbulence decomposition methods on a tidal energy site assessment; 10) parametric study for an oscillating water column wave energy conversion system installed on a breakwater; 11) optimal dimensions of a semisubmersible floating platform for a 10 MW wind turbine; 12) fatigue life assessment for power cables floating in offshore wind turbines