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The point absorber is one of the most popular types of ocean wave energy converter (WEC) that harvests energy from the ocean. Often such a WEC is deployed in an ocean location with tidal currents or ocean streams, or serves as a mobile platform to power the blue economy. The shape of the floating body, or buoy, of the point absorber type WEC is important for the wave energy capture ratio and for the current drag force. In this work, a new approach to optimize the shape of the point absorber buoy is developed to reduce the ocean current drag force on the buoy while capturing more energy from ocean waves. A specific parametric modeling is constructed to define the shape of the buoy with 12 parameters. The implementation of neural networks significantly reduces the computational time compared to solving hydrodynamics equations for each iteration. And the optimal shape of the buoy is solved using a genetic algorithm with multiple self-defined functions. The final optimal shape of the buoy in a case study reduces 68.7% of current drag force compared to a cylinder-shaped buoy, while maintaining the same level of energy capture ratio from ocean waves. The method presented in this work has the capability to define and optimize a complex buoy shape, and solve for a multi-objective optimization problem. Master of Science The marine kinetic energy includes ocean waves power, tidal power, ocean current power, ocean thermal power and river power. The total potential marine kinetic energy in 2021 is 2300 TWh/year, where 1400 TWh/year is from the ocean wave power. To discover and harvest the huge potential power from the marine, researchers have been developed for different types of WECs for several decades. One of the most successful concepts is the point absorber typed WEC, which can extract waver energy from the heaving vibration motion of a floating body and convert the kinetic energy into electrical energy. This thesis presents an optimization strategy to optimize the shape of the floating body to improve power extraction and reduce the installation cost by implementing the machine learning tool and genetic algorithm. Compared with the state-of-the-art optimization strategies, the proposed optimization method allows the floating body to have more parameters in shape changes and reduces the computational cost from minutes to milliseconds. The final optimized floating body shape performs extraordinarily compared to the other two state-of-the-art floating body shapes.

Cuttlebone, the endoskeleton of cuttlefish, offers an intriguing biological structural model for designing low-density cellular ceramics with high stiffness and damage tolerance. Cuttlebone is highly porous (porosity ~93%) and lightweight (density less than 20% of seawater), constructed mainly by brittle aragonite (95 wt%), but capable of sustaining hydrostatic water pressures over 20 atmospheres and exhibits energy dissipation capability under compression comparable to many metallic foams (~4.4 kJ/kg). Here we computationally investigate how such a remarkable mechanical efficiency is enabled by the multiscale structure of cuttlebone. Using the common cuttlefish, Sepia Officinalis, as a model system, we first conducted high-resolution synchrotron micro-computed tomography (µ-CT) and quantified the cuttlebone's multiscale geometry, including the 3D asymmetric shape of individual walls, the wall assembly patterns, and the long-range structural gradient of walls across the entire cuttlebone (ca. 40 chambers). The acquired 3D structural information enables systematic finite-element simulations, which further reveal the multiscale mechanical design of cuttlebone: at the wall level, wall asymmetry provides optimized energy dissipation while maintaining high structural stiffness; at the chamber level, variation of walls (number, pattern, and waviness amplitude) contributes to progressive damage; at the entire skeletal level, the gradient of chamber heights tailors the local mechanical anisotropy of the cuttlebone for reduced stress concentration. Our results provide integrated insights into understanding the cuttlebone's multiscale mechanical design and provide useful knowledge for the designs of lightweight cellular ceramics. Upon the prior curvature analysis of the cuttlebone walls, we discovered that the walls were primarily "saddle-shaped". Thus, the characterization of different curvatures, varying between flat, domed, saddled, or cylindrical surfaces, were explored. A mathematical model was utilized to generate multiple walls with different curvature characteristics. We observed the mechanical performance of these walls via finite-element analysis and formulated different techniques for designing effective ceramic structures through incorporation of curvature. Master of Science The cuttlefish is a marine species that instead of having an inflatable swim bladder like fish, is a mollusk capable of swimming by utilizing their skeleton, called the cuttlebone. The cuttlefish can freely traverse the waters by controlling the flow of water in and out of their brittle skeletons, changing their buoyancy. For this reason, the cuttlebone must be very porous yet strong to withstand the deep-water pressures, enticing an interest for closer observation of the structure which may be useful in engineering applications involving ceramic structures. In this study, we examined an actual cuttlebone structure to better visualize its features with high-resolution synchrotron micro-computed tomography (µ-CT) and tabulated its mechanical performance through a variety of tests using computational software. The skeletal design of the cuttlebone consists of multiple layered chambers supported by wavy, pillar-like walls. It was revealed that the cuttlebone is remarkable due to its multiscale design: the asymmetric geometry of the walls are designed to tolerate considerable amounts of energy while a stiff construction; at the chamber level, variation of walls (number, pattern, and waviness amplitude) helps avoid complete destruction of the structure in the event of an excessive force; at the entire skeletal level, various of chamber heights reduces inflicted stress in concentrated regions of the cuttlebone. The wavy walls were also observed to retain a saddle-shaped curviness, versus simple flat, domed, or cylindrical shaped walls. This created an incentive to explore the effects of curvature on the structural integrity of brittle ceramic structures. We developed an effective way for generating walls with different curvatures and observed the mechanical performance of each wall by crushing them in computer simulations. It was identified that adding curvature to brittle walls prolonged the failure period significantly. While the cylindrical walls were found to be rather stiff, saddle-shaped walls, although not capable of withstanding as much force as flat or cylindrical walls, has a more progressive failure behavior meanwhile maintaining high energy absorption, hence the saddled walls of the cuttlebone to allow maintenance and self-repair in damaged regions.

Survivability is by no means a new concept to ocean engineering; ships must remain stable and structurally intact in violent sea states; the same is true for offshore oil and gas structures. While knowledge from the ship and offshore sectors can be valuable for designing wave energy converters (WECs) for survival in rough seas, the unique scale, siting and operational characteristics of WECs pose a distinct set of engineering challenges. This paper seeks to provide a review of methods for modeling the loading and dynamic response of WECs and analogue marine structures, such as ships and offshore structures, in large nonlinear waves. We identify current knowledge gaps in our understanding of WEC survivability and provide recommendations for future research to close these gaps. U.S. Department of Energy Wind and Water Power Program

This paper provides a global ocean circulation model based world-wide assessment of two flow characteristics and presents a direct comparison between model based predictions and in situ measurements in two regions. Four years (2009-2012) of HYbrid Coordinate Ocean Model (HYCOM)-generated data were used to estimate the average kinetic energy flux and flow direction variability in eight regions with time-averaged power density of at least 500 W/m². A direct comparison was then made between model calculated flow statistics those calculated from Acoustic Doppler Current Profiler data in both South Africa and the Southeast United States. Included analysis and discussion is intended to provide model predictions of the ocean current resource and assess the accuracy that can be expected when this model is used for making these predictions. This paper focuses on model predicted kinetic energy flux, flow speeds, and current direction variability, as these are important to the development and installation of OCT devices. Florida U.S. Department of Energy

Garrett Hardin s lifeboat metaphor is used to illustrate the problems of overpopulation and finite resources. Sea levels are rising due to excess atmospheric greenhouse gases that melt glaciers and warm the oceans. With anthropogenic greenhouse gas emissions continuing to increase, humankind has placed human culture and individuals at serious risk. Rising sea levels will soon make some low-lying islands uninhabitable.

Hardin s lifeboat metaphor simplifies the issues involved in living on a finite planet with finite resources. If humankind hopes to remain on Earth for many generations, then humans need to understand and cope with the limits of a finite planet. Also, the rights and responsibilities of achieving the sustainable use of the planet must be congruent, equal effort from every country.

Verdant Power, LLC (Verdant) is licensed to operate an array of up to 30 kinetic hydropower turbines in East River, NY. During the licensing process, National Marine Fisheries Service (NMFS), the federal regulatory agency responsible for protecting Endangered Species Act (ESA)‐listed Atlantic and shortnose sturgeons, expressed concern regarding the potential interaction of these species with the turbines. To advance understanding of potential interactions, Verdant, partnering with the marine fishery community through the Atlantic Cooperative Telemetry (ACT) Network, installed 3 VEMCO fixed detection devices near the Project to collect presence and distribution data on sturgeon tagged by the ACT researchers. During the 25 months that the receivers have been deployed, 22 tagged fish ranging in size from 150 cm have been detected including 15 Atlantic sturgeon. These data have provided valuable spatial and temporal distribution information and represent the first documented proof that sturgeon migrate through the East River.

An informed, and accurate, characterization of the wave energy resource is an essential aspect selection of suitable sites for the first commercial installations of wave energy converters. This paper describes a detailed study on the variability of wave climate and measured spectral shapes and how they differ from the standard formulations prescribed by theory. In particular dissonance between the ratio of the energy period (TE) to the average zero-crossing period (T₀₂) is investigated at a range of open ocean locations. This relationship is important in the context of resource assessment as many previous works, lacking in detailed spectral data, have often assumed an incorrect ratio. This in turn has influenced the accuracy of the resulting estimates of wave energy. It is demonstrated that the earlier use of the frequently-employed wave period ratios is erroneous and more suitable relationships are presented for the Bretschneider and JONSWAP theoretical spectra. Furthermore, analysis of measured buoy data from real sea-states is used to illustrate that this relationship can in fact vary significantly in practice, depending on geographical location and the prevalent wave conditions. The variability that exists in spectral shape and bandwidth, and the effect this has on the relationship between TE and T₀₂, is illustrated through the comparison of recorded spectra with the Bretschneider spectrum. Analysis of a fifteen year dataset measured by a buoy off the coast of Southern California is presented to illustrate how the wave period ratio fluctuates on a seasonal and interannual basis, while it is also shown that previous studies of the Irish wave energy resource may have underestimated the theoretical power available by as much as 18%. Irish Research Council for Science Engineering and Technology Science Foundation Ireland Charles Parsons Research Award

Metadata only record Intensive upland agriculture and fishing are the major income producers for those individuals living around Singkarak Lake. Poor agricultural management, over fishing, and hydroelectric draw downs are negatively impacting the lake. The local communities are becoming aware of the environmental issues and are currently working on a reforestation project. Potential environmental services buyers are the state hydropower company and the international community. PES-1 (Payments for Environmental Services Associate Award)

Some claim that humans are too numerous to become extinct. However, passenger pigeon, once the most numerous birds on the planet, are now extinct. For years, humankind has been damaging its habitat, discharging toxic chemicals into the environment, and having harmful effects on agricultural productivity due to climate change. Humankind s extinction depends on the continuation of various human activities including economic growth, addiction to fossil fuel, over consumption, overpopulation, ocean acidification, and use of toxicants. If humankind wants to remain on this planet, it must start preparing for a vastly different environment on Earth.