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Osteoid osteoma is a benign tumor that accounts for roughly 10-12% of all benign bone forming tumors. This tumor generally occurs within the first three decades of life and occurs more commonly in males. This lesion is painful and is generally worse at night and has relief of symptoms with the use of NSAIDs. Osteoid osteoma is characterized by the production of osteoid surrounded by a rim of sclerotic bone. These lesions most commonly occur in long bones such as the proximal femur, however they can occur anywhere. Rarely, as with our patient, have these lesions been reported in the acetabulum.

Bisphosphonate (BP) therapy for moderate to severe osteogenesis imperfecta (OI) has become a mainstay of treatment in the last three decades. Given the significant improvements in bone mineral density and theoretical reductions in fracture risk, many patients are treated with bisphosphonates for prolonged periods of time. There currently lacks consensus in the optimal duration of BP therapy for patients with OI, and patients are often treated on a case-by-case basis. Long-term BP therapy has been associated with atypical femur fractures in adult patients treated for osteoporosis. The American Society for Bone and Mineral Research concluded that the median duration of BP therapy in patients with atypical femur fractures was 7 years. The role of long-term BP therapy in OI patients with atypical femur fractures remains unclear. Here, a case report is presented of an adolescent patient with type V OI that sustained a subtrochanteric femur fracture with features of an atypical pattern following treatment with intravenous pamidronate for 10.5 years. At the time of injury, the contralateral femur was also found to have atypical features suggestive of an impending fracture. The completed fracture was treated with closed reduction and cephalomedullary nail fixation. The impending fracture was prophylactically stabilized using the same technique. Prior to the injury, limb-length radiographs obtained to evaluate lower extremity alignment demonstrated features of an impending fracture but went unnoticed. Further studies are needed to clarify the role of long-term BP therapy in patients with OI suffering from atypical femur fractures.

In California offshore waters, sustained northwesterly winds have been identified as a key energy resource that could contribute substantially to California’s renewable energy goals. However, the development of large-scale offshore wind farms has the potential to reduce the wind stress at the sea surface, which could have implications on wind-driven upwelling, nutrient delivery, and ecosystem dynamics. Using atmospheric and ocean circulation models together with a hypothetical upper boundary buildout scenario of 877 turbines spread across three wind energy areas of interest, wind speed reductions in the lee of the wind energy areas of interest are found to enhance horizontal wind stress shear, leading to reduced upwelling on the inshore side of windfarms and increased upwelling on the offshore side. These changes, when expressed in terms of widely used metrics for upwelling volume transport and nutrient delivery, show that while the net upwelling in a wide coastal band changes relatively little, the spatial structure of upwelling within this coastal region can be shifted outside the bounds of natural variability.

Surrogate models maximize information utility by building predictive models in place of computational or experimentally expensive model runs. Marine hydrokinetic current energy converters require large-domain simulations to estimate array efficiencies and environmental impacts. Meso-scale models typically represent turbines as actuator discs that act as momentum sinks and sources of turbulence and its dissipation. An OpenFOAM model was developed where actuator disc k-e turbulence was characterized using an approach developed for flows through vegetative canopies. Turbine-wake data from laboratory flume experiments collected at two influent turbulence intensities were used to calibrate parameters in the turbulence-source terms in the k-e equations. Parameter influences on longitudinal wake profiles were estimated using Gaussian process regression with subsequent optimization minimizing the objective function within 3.1% of those obtained using the full model representation, but for 74% of the computational cost (far fewer model runs). This framework facilitates more efficient parameterization of the turbulence-source equations using turbine-wake data.

Development of alternative energy production in the United States continues at a rapid pace, with significant public and private investment in recent years. Offshore wind energy (herein referred to as offshore wind) has become a significant contributor to the global energy market, and the number of projects in the United States is rapidly increasing. As the technology continues to improve, the ability to deploy offshore wind turbines in deeper waters becomes increasingly feasible; however, differences in deployment environments bring unique challenges. To continue developing offshore wind as a viable renewable energy source, the United States must overcome three critical hurdles: (1) reduce the cost of generating offshore wind electricity, (2) accelerate the deployment and permitting process, and (3) integrate the new electrical source with the national grid. This work aims to help reduce time and costs associated with planning, development, and permitting by accurately predicting environmental responses to the presence of offshore wind arrays. We demonstrate that interactions between offshore wind infrastructure and the environment can be accurately assessed through a focused model development and validation process that considers the interrelationships between ocean waves, circulation, and seabed dynamics. Best practices are recommended to help guide future model development.

Increasing interest in power production from ocean, tidal, and river currents has led to significant efforts to maximize energy conversion through optimal design and siting and to minimize effects on the environment. Turbine-based, current-energy-converter (CEC) technologies remove energy from current-driven systems and in the process generate distinct wakes, which can interact with other CEC devices and can alter flow regimes, sediment dynamics, and water quality. This work introduces Sandia National Laboratories-Environmental Fluid Dynamics Code CEC module and verifies it against a two-dimensional analytical solution for power generation and hydrodynamic response of flow through a CEC tidal fence. With a two-dimensional model that accurately reflects an analytical solution, the effort was extended to three-dimensional models of three different laboratory-flume experiments that measured the impacts of CEC devices on flow. Both flow and turbulence model parameters were then calibrated against wake characteristics and turbulence measurements. This is the first time that turbulence parameter values have been specified for CEC devices. Measurements and simulations compare favorably and demonstrate the utility and accuracy of this numerical approach for simulating the impacts of CEC devices on the flow field. The model can be extended to future siting and analyses of CEC arrays in complex domains.

Variability 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. The research leading to this publication is part of the DTOceanPlus project which has received funding from the EuropeanUnion's Horizon 2020 research and innovation programme under grant agreement No 785921. Funding was also received from the European Community's Seventh Framework Programme for the DTOcean Project (grant agreement No. 608597). The contribution of Sandia National Laboratories was funded by the U.S. Department of Energy's Water Power Technologies Office. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. The image of the RM3 device, in Fig. 7, was reproduced with the permission of Sandia National Laboratories

Hydrokinetic tidal energy converter (TEC) technology is yet to become cost competitive with other renewable energy sources. Understanding the interaction between energy production and the costs incurred harvesting that energy may unlock the economic potential of this technology. Although hydrodynamic simulation of TEC arrays has matured over time, including demonstration of how small and large arrays affect the resource, integration of cost modelling is often limited. The advanced ocean energy array techno-economic modelling tool `DTOcean&rsquo, enables designers to calculate and improve the levelised cost of energy (LCOE) of an array through parametric simulation of the energy extraction, design of the electrical network, moorings and foundations, and simulation of the installation and lifetime operations and maintenance of the array. This work presents a verification of DTOcean&rsquo, s ability to simulate the techno-economic performance of TEC arrays by reproducing the hypothetical RM1 reference model, a semi-analytical model of a TEC array based in the Tacoma Narrows of Washington state, U.S.A. It is demonstrated that DTOcean can produce a reasonable estimate to the LCOE predicted by the reference model, giving (in Euro cents per kiloWatt hour) 36.69 &cent, /kWh against the reference model&rsquo, s 34.612 &cent, /kWh for 10 TECs, while for 50 TECs, DTOcean calculated 20.34 &cent, /kWh compared to 17.34 &cent, /kWh for the reference model.

The marine and hydrokinetic (MHK) industry plays a vital role in the U.S. clean energy strategy by providing a renewable, domestic energy source that may offset the need for traditional energy sources. The first MHK deployments in the U.S. have incurred very high permitting costs and long timelines for deploying projects, which increases project risk and discourages investment. A key challenge to advancing an economically competitive U.S. MHK industry is reducing the time and cost required for environmental permitting and compliance with government regulations. Other industries such as offshore oil and gas, offshore wind energy, subsea power and data cables, onshore wind energy, and solar energy facilities have all developed more robust permitting and compliance pathways that provide lessons for the MHK industry in the U.S. and may help inform the global consenting process. Based on in-depth review and research into each of the other industries, we describe the environmental permitting pathways, the main environmental concerns and types of monitoring typically associated with them, and factors that appear to have eased environmental permitting and compliance issues.

The effect a marine hydrokinetic device, or array of devices, has on the environment is a key component of design, permitting, and viability of a project. To accurately understand physical processes and their potential relationship to environmental stressors at a current-energy converter (CEC) site, a numerical model was developed using SNL-Delft3D-CEC-FM to facilitate an understanding of the potential changes to the system . Conceptual flowchart of the modeling methodology. Using turbine and river data provided by the Alaska Hydrokinetic Energy Research Center, a steady-state flow model was constructed for varying river discharge levels. The wakes of University of Alaska at Fairbanks New Energy Systems vertical-axis, 5-kW turbine as well as commensurate changes to the steady-state flow field were simulated. Finally, an example optimization study was undertaken for turbines arranged in various arrays to demonstrate the effects of lateral and downstream interference, wake recovery, and overall momentum removal on the flow conditions and power generation. Considering a distribution of flow conditions over a 10-year period for the Tanana River at Nenana, variations in number of CEC devices and array layout provided insights into power production and environmental effects. Specific quantities of interest included changes in velocity and bed shear stress, which each showed changes in proportion to the number of devices in the array. Using SNL-Delft3D- CEC-FM with calibrated turbulence constants allowed for a design that maximized CEC array power while remaining within constraints of minimally altered environmental conditions. That is, array layouts could be selected to optimize power generation while minimizing flow-field changes. This work highlights the importance of investigating array performance at each site under consideration. These findings are helpful in optimizing turbine arrangements in the Tanana River at Nenana that maximize power production and minimizes undesirable/unintended changes to the river's natural flow (flow depth, velocity, and bottom shear).

Reduced-order models for mesoscale current energy converter (CEC) modeling allow for tractable computation times for investigations of array configurations on power performance and environmental effects to support design optimization. The CEC representation in these models take the form of actuator discs in codes such as SNL-Delft3D-CEC-FM treating the rotating CEC blades as momentum sinks. In the first-of-its-kind, whole-plant optimization software, DTOcean, the hydrodynamic modelling of CECs is reduced one step further by superimposing wake models based on normalized CFD simulations onto a set of pre-computed velocity fields, to provide power estimates. DTOcean is a new tool and the amount of verification and validation evidence gathered is presently limited. To gain additional confidence and industry buy-in to the software penetration, this study investigated a primary component of levelized cost of electricity (LCOE) calculation, annual energy production (AEP), through an analytic calculation of power using the results of an identical simulation in SNL-Delt3D-CEC-FM. Three configurations of an 8-turbine array are studied with DTOcean where two rows of 4-turbines are spaced (unstaggered) 5-, 10-, and 20-Diameters apart and the AEP was calculated; The energy calculation in SNL-Delft3D-CEC-FM were more computationally expensive for the mesoscale domain making the optimization of solely an arrays power production using the wake superposition method implemented DTOcean attractive. The codes however are complementary as SNL-Delft3D-CEC-FM simultaneously investigates environmental effects of varying array configurations while DTOcean considers all aspects of array costs through its lifetime to optimize LCOE from a whole-plant perspective.

Integration of renewable power sources into grids remains an active research and development area, particularly for less developed renewable energy technologies such as wave energy converters (WECs). WECs are projected to have strong early market penetration for remote communities, which serve as natural microgrids. Hence, accurate wave predictions to manage the interactions of a WEC array with microgrids is especially important. Recently developed, low-cost wave measurement buoys allow for operational assimilation of wave data at remote locations where real-time data have previously been unavailable. This work includes the development and assessment of a wave modeling framework with real-time data assimilation capabilities for WEC power prediction. The availability of real-time wave spectral components from low-cost wave measurement buoys allows for operational data assimilation with the Ensemble Kalman filter technique, whereby measured wave conditions within the numerical wave forecast model domain are assimilated onto the combined set of internal and boundary grid points while taking into account model and observation error covariances. The updated model state and boundary conditions allow for more accurate wave characteristic predictions at the locations of interest. Initial deployment data indicated that measured wave data from one buoy that were assimilated into the wave modeling framework resulted in improved forecast skill for a case where a traditional numerical forecast model (e.g., Simulating WAves Nearshore; SWAN) did not well represent the measured conditions. On average, the wave power forecast error was reduced from 73% to 43% using the data assimilation modeling with real-time wave observations.

The primary objectives of this study are to evaluate the levelized cost of energy (LCOE) for different wave energy conversion strategies and to examine cost reduction pathways such that wave energy conversion projects are competitive, relative to alternative energy industries. The energy production of six different WEC devices was estimated for four sites along the U.S. Pacific coast. The LCOE of pilot-scale wave energy conversion projects was estimated to range between $0.07/kWh and $0.92/kWh higher than the target LCOE of those for early-market offshore wind energy projects. Device capacity factors were generally below the commonly assumed value of 30%. Methods of cost reduction to the target LCOE of $0.30/kWh were explored, including decreasing capital and operational expenditures (CAPEX and OPEX) and increasing annual energy production (AEP) through improvements in the wave energy resource and WEC and WEC array performance, and advanced controls. Results indicate that CAPEX and OPEX should be reduced by at least 45% and AEP should be increased by 200%. A reduction of CAPEX and OPEX by 75%, combined with array evaluation and control strategies capable of increasing AEP by 12%–55% could also result in LCOE for wave energy conversion projects of less than $0.30/kWh.

Marine hydrokinetic (MHK) devices generate electricity from the motion of tidal and ocean currents, as well as ocean waves, to provide an additional source of renewable energy available to the United States. These devices are a source of anthropogenic noise in the marine ecosystem and must meet regulatory guidelines that mandate a maximum amount of noise that may be generated. In the absence of measured levels from in situ deployments, a model for predicting the propagation of sound from an array of MHK sources in a real environment is essential. A set of coupled, linearized velocity-pressure equations in the time-domain are derived and presented in this paper, which are an alternative solution to the Helmholtz and wave equation methods traditionally employed. Discretizing these equations on a three-dimensional (3D), finite-difference grid ultimately permits a finite number of complex sources and spatially varying sound speeds, bathymetry, and bed composition. The solution to this system of equations has been parallelized in an acoustic-wave propagation package developed at Sandia National Labs, called Paracousti. This work presents the broadband sound pressure levels from a single source in two-dimensional (2D) ideal and Pekeris wave-guides and in a 3D domain with a sloping boundary. The paper concludes with demonstration of Paracousti for an array of MHK sources in a simple wave-guide.

As the technology of hydrokinetic tidal energy conversion looks to exploit smaller markets in the wider ‘blue economy’, innovation is still required to ensure cost competitiveness with other energy sources. A typical assumption of existing techno-economic models of tidal energy converter (TEC) arrays is that TECs positioned to minimise negative hydrodynamic interactions will maximise economic return. That the number of TECs within an array should be chosen to maximise the annual energy production, follows from this assumption. To examine the validity of these assertions for small, area-constrained arrays, a hypothetical model of the relationship of levelised cost of energy (LCOE) to the mean mechanical annual energy production (MMAEP) is developed. The model exhibits three classes of behaviour, determined by the rate of energy lost to interactions as TECs are added to an optimally positioned array; significantly, only one class has greatest MMAEP corresponding to lowest LCOE. To test this model, a contemporary optimisation algorithm is added to the advanced ocean energy techno-economic simulation tool ‘DTOcean’ and applied to arrays of TECs constrained by a 2 ha deployment area. It is shown that the hypothetical LCOE model accurately describes the DTOcean results up to and including 12 TECs deployed. At 13 TECs deployed, the level of TEC interaction increases dramatically, invalidating the hypothetical model. Notably, however, the LCOE is shown to reduce significantly by allowing negative interactions between TECs, reducing by 47.8% from the best non-interacting array. Thus, subject to an improved understanding of the relationship between the environment, TEC reliability and costs, the results indicate that allowing negative interactions between TECs may increase the economically extractable resource of small area-constrained tidal energy sites.

The marine renewable energy (MRE; renewable energy captured from waves, tides, ocean currents, the natural flow of water in rivers, and marine thermal gradients, without building new dams or diversions) industry has a vital role in the U.S. clean energy strategy as we progress to meet U.S. electricity and blue economy needs with renewable, domestic energy sources. However, a thorough assessment of the U.S. marine energy permitting process from the viewpoints of both developers that propose projects and regulators that permit them has not been performed. Sharing practical experiences in this new industry is vital to increase the efficiency and effectiveness of the permitting process, identify data and information gaps, develop lessons learned, and advance the industry. This paper is a case study of qualitative findings, lessons learned, and recommendations from guided discussions, workshops, and webinars with both marine renewable energy developers and state and federal regulators that have experience in the permitting process in the U.S.

In this study, systems engineering techniques are applied to wave energy to identify and specify stakeholders’ requirements for a commercially successful wave energy farm. The focus is on the continental scale utility market. Lifecycle stages and stakeholders are identified. Stakeholders’ needs across the whole lifecycle of the wave energy farm are analyzed. A list of 33 stakeholder requirements are identified and specified. This list of requirements should serve as components of a technology performance level metric that could be used by investors and funding agencies to make informed decisions when allocating resources. It is hoped that the technology performance level metric will accelerate wave energy conversion technology convergence.

A modelling framework identifies deployment locations for current-energy-capture devices that maximise power output while minimising potential environmental impacts. The framework, based on the Environmental Fluid Dynamics Code, can incorporate site-specific environmental constraints. Over a 29-day period, energy outputs from three array layouts were estimated for: (1) the preliminary configuration (baseline), (2) an updated configuration that accounted for environmental constraints, (3) and an improved configuration subject to no environmental constraints. Of these layouts, array placement that did not consider environmental constraints extracted the most energy from flow (4.38 MW-hr/day), 19% higher than output from the baseline configuration (3.69 MW-hr/day). Array placement that considered environmental constraints removed 4.27 MW-hr/day of energy (16% more than baseline). This analysis framework accounts for bathymetry and flow-pattern variations that typical experimental studies cannot, demo...