Marine Energy Technology Symposium

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https://hdl.handle.net/10919/49096

The Marine Energy Technology Symposium, http://www.globalmarinerenewable.com/mets/, is held in conjunction with The Global Marine Renewable Energy Conference (GMREC). All METS papers are peer-reviewed and authors whose papers are accepted to METS will have the opportunity to give a technical presentation at METS. Note that authors must present their paper in-person at METS in order to have their work included in the conference proceedings.

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Experimental and Numerical Analysis of a Scale-Model Horizontal Axis Hydrokinetic Turbine
Javaherchi, Teymour; Seydel, Joseph; Stelzenmuller, Nick; Aliseda, Alberto (2014-04)
This paper presents an experimental/numerical study of a scale-model Horizontal Axis Hydrokinetic Turbine (HAHT). The model turbine is based on the DOE Reference Model 1 (DOE RM1), with a modified geometry to reproduce performance at the flume scale Reynolds numbers. These modifications were necessary to overcome the strong Reynolds number effect on the NACA–6 airfoil family used on the design, and therefore on the device performance in experimental analysis. The performance and wake structure of a single turbine was analyzed with measurements conducted on a 45:1 scale physical model of the modified design of the DOE RM1 rotor. The details of the rotor flow field and wake evolution are analyzed from numerical solution of the RANS equations solved around a computational model of the scale-model turbine. A comparison between the experimental and numerical results is presented. These comparisons highlight the strengths as well as limitations of the experimental and numerical analysis for these types of HAHT characterizations. On a more general sense, these comparisons provide useful guidelines for developing a set of experimental flume scale data and to use it to validate numerical tools, and as pilot projects start to go in the water in the US, to perform a similar type of analysis and design validation of full scale devices.
A Methodology for Wave-to-Wire WEC Simulations
Bailey, Helen; Ortiz, Juan P.; Robertson, Bryson; Buckham, Bradley J.; Nicoll, Ryan S. (2014-04)
This paper looks at the methodology of building a full wave-to-wire WEC (Wave Energy Convertor) simulation and presents examples of its use for a variety of different types of WEC. Wave resource information from the West Coast of Vancouver Island is considered. A detailed wave-body interaction model is generated using ProteusDS software. This model is linked to Simulink, which allows a detailed PTO (Power Take Off) model to be simulated, which will feedback into the motions of the WEC. Three different examples are presented for different WECs. These WECs are Resolute Marine Energy's Surging flap, Seawood Designs' SurfPower and an internal University of Victoria two-body concept.
Initial Characterization of the Wave Resource at Several High Energy U.S. Sites
Dallman, Ann; Neary, Vincent S. (2014-04)
Wave energy resource characterization efforts are critical for developing knowledge of the physical conditions experienced by wave energy converter (WEC) devices and arrays. Developers are lacking a consistent characterization of possible wave energy test sites, and therefore Sandia National Laboratories (SNL) has been tasked with developing a catalogue characterizing three high energy U.S. test sites. The initial results and framework for the catalogue are discussed in this paper.
Annex IV - Investigating Environmental Effects of Wave and Tidal Devices Through International Cooperation
Copping, Andrea; Hanna, Luke; Battey, Hoyt (2014-04)
The pace of development for marine energy projects worldwide continues to be hindered by uncertainty surrounding potential environmental effects of wave and tidal devices and the balance of system. In response to this continued uncertainty, member nations of the Ocean Energy Systems (OES) developed a collaborative project – Annex IV – to increase collection and sharing of knowledge, research collaborations around high priority environmental interactions, and relevancy of the information to permitting (consenting) processes. The culmination of Annex IV Phase 1 is a searchable database of current literature and reports on environmental effects of marine energy development, and an analysis of three key interactions of devices and the marine environment.
Testing and Accelerated Aging of Conductive Antifouling Paints for Marine Applications
Bunn, Malachi; Yokochi, Alex (2014-04)
Marine hydrokinetic (MHK) device survivability is necessary to understand in order to develop the vast renewable wave and tidal energy resource. Antifouling coatings serve to ensure device longevity by preventing degradation associated with mollusk adhesives and general performance degradation due to hydrodynamic surface changes, clogged pinch points, and added drag. Coatings developed to serve the shipping industry are generally insufficient for MHK service due to finite biocide content, short service life, and operating condition requirements such as continuous movement at elevated speeds. Electrochemical antifouling methods have been shown to be effective in the prevention of fouling organism growth on objects submerged in seawater.[1] Service life has been provided in one study as 8 months with failure due to binder paint film degradation.[2] Appropriate selection of paint binder systems and rigid substrates may extend this time significantly. Degradation of the conductive pigment filler, in this work graphite, may also lead to performance loss and ultimately to system failure. The specific goal of the current work is to model the antifouling process at a charged graphite filled paint electrode and the degradation of system performance due to degradation of the graphite filler. Under accelerated aging conditions no significant degradation has been observed with simulated aging to 20 years of service life.
Control of a Helical Cross‐Flow Current Turbine
Cavagnaro, Robert; Fabien, Brian; Polagye, Brian (2014-04)
Adaptive control strategies utilizing preview information of upstream velocity are promising approaches for enhancing performance and reducing loads on hydrokinetic turbines. A control scheme relating a turbine's characteristic performance curve and rotation rate to an optimal torque setpoint is implemented experimentally and in simulation for a laboratory‐scale helical cross‐flow turbine. Energy extraction performance for schemes employing adaptive/preview techniques is compared to performance under constant speed and non‐adaptive control. Results in simulation indicate significant improvement over constant speed operation and modest improvement over non‐adaptive strategies. Experimental results for adaptive strategies are comparable to non‐adaptive strategies, due to uncertainty in instantaneous performance curves.
CACTUS Open Source Code for Hydrokinetic Turbine Design and Analysis: Model Performance Evaluation and Public Dissemination as Open Source Design Tool
Michelen, Carlos; Murray, Jonathan C.; Neary, Vincent S.; Barone, Mathew (2014-04)
Sandia National Laboratories recently released an open source code for design and analysis of axial‐flow and cross‐flow marine and hydrokinetic (MHK) turbines, CACTUS (Code for Axial and Cross‐flow TUrbine Simulation), and has initiated an outreach effort to promote its use among MHK researchers and developers. Our aim in this paper is to summarize the recent developments in CACTUS, and present model performance evaluation results that demonstrate CACTUS's potential use as a design and optimization tool for marine hydrokinetic turbines. We present several model validation tests to evaluate the model's ability to predict MHK turbine performance. The results show both the potential use of CACTUS as a design tool and its current limitations. At least two more model validation tests are planned for 2014 as part of this effort: scaled model tests of DOE's Reference Model 1(RM1) and Reference Model 2 (RM2) turbines in 2014 at the University of Minnesota's St. Anthony Falls Laboratory (SAFL).
Dynamic Modelling of Compliant-Moored Submerged Systems with Applications to Marine Energy Converters
Nichol, Tyler; DuBuque, Geoff; Fabien, Brian (2014-04)
This paper presents a full‐range‐of‐motion numerical model of the dynamic characteristics of compliant‐moored submerged systems in unsteady fluid flow using a first‐principles approach. The program, implemented using the MATLAB software package, is in development with the primary intention of being applicable to in‐stream hydrokinetic turbines, though many wave energy converter and offshore wind turbine platform systems will also be capable of being modeled. A Lagrangian frame of reference is adopted to generate the equations of motion of a given system. The external forces presently considered in the model are those of gravity, buoyancy, and fluid drag, with plans to include more sophisticated fluid effects as the project advances. The development of the kinematic system and the body drag model are discussed. Additionally, two validation tests are presented. The results of the validation tests provide confidence that the methods employed have the potential to realistically simulate the dynamic behavior of compliant-moored systems once more detailed effects of fluid loading are accounted for.
Superstorm Sandy and the Verdant Power Rite Project
Corren, Dean; Colby, Jonathan; Adonizio, Mary Ann (2014-04)
On October 29, 2012 Superstorm Sandy (formerly Hurricane Sandy) made landfall in New Jersey. With unprecedented size, extreme central low pressure, and full-moon timing , it created a storm surge that inundated New York City with record-breaking water levels, resulting in tremendous destruction of buildings and infrastructure. All along the East River, large areas of the adjacent boroughs were impacted by Sandy, including flooding of the subway tunnels under the river. When Sandy struck, Verdant Power was operating two acoustic Doppler current profilers (ADCPs) at its Roosevelt Island Tidal Energy (RITE) Project in New York City's East River, measuring water velocities and depth. The East River water speed and level data acquired during Sandy is revelatory, not only indicating the extent and timing of the extraordinarily high levels, but also significant changes to the very sense of the tidal flows. As a Federal Energy Regulatory Commission (FERC) licensee for a commercial pilot project to install up to 30 turbines in the East River, Verdant is keenly interested in the effects such an extreme storm could have on turbines, instruments and navigational aids. This unique observational data provides a valuable insight for Verdant Power and the marine and hydrokinetic (MHK) industry.In this paper, Verdant first presents the East River data collected during Superstorm Sandy, indicating what actually happened during the storm. The potential for yet more extreme water levels with a different storm timing relative to the astronomical tides is then examined. Finally, of interest to a kinetic hydropower developer, the data is analyzed to estimate how a different storm timing could affect the water velocities through the river. These findings are related to the design criteria for Verdant's equipment and the potential impact of an extreme storm on a commercial array of kinetic hydropower turbines.
Pneumatic Performance of a Non-Axisymmetric Floating Oscillating Water Column Wave Energy Conversion Device in Random Waves
Bull, Diana (2014-04)
A stochastic approach is used to gain a sophisticated understanding of a non-axisymmetric floating oscillating water column's response to random waves. A linear, frequency-domain performance model that links the oscillating structure to air-pressure fluctuations with a Wells Turbine in 3-dimensions is used to study the device performance at a northern California deployment location. Both short-term, sea-state, and long-term, annual, predictions are made regarding the devices performance.
Experimental Study of Tribological Performance of Bearing-Seal Assembly of Hydrokinetic Devices in Sedimented Water
Ali, Muhammad; Ravens, Thomas M.; Petersen, Todd H.; Bromaghin, Angus F.; Jenson, Sean R. (2014-04)
In this study, wear of polymer and ceramic coated bearings for use in hydrokinetic devices were investigated in sedimented water under the loading conditions similar to those expected in the field using a customized flume. This work is a continuation of the study performed in [1, 2] in which three polymer bearings, namely Vesconite, CIP, Feroform T814, and one ceramic coated bearing, namely Poly Crystalline Diamond Coated (PCD) along with two mechanical seals were tested in clean water for 60 hours. The results showed that PCD bearings experienced least amount of wear followed by Feroform T814, CIP, and Vesconite. The load side surfaces of polymer bearings exhibited a circular wear pattern whereas PCD bearings did not show any distinctively identifiable wear pattern. Following the same testing methodology, 60 hours long tests were conducted in fresh sedimented water on the same types of (new) bearings and seals. The data showed that bearings had similar (or less) total wear in sedimented water as compared to clean water, however, the drive shaft experienced a significant surface wear. In addition, the loading side of polymer bearing surfaces developed a circular wear pattern with significantly higher wear on the edge surfaces.
Stability and Loads Validation of an Ocean Current Turbine
Swales, Henry; Coackley, Dave; Gupta, Sandeep; Way, Stephen (2014-04)
The design of a moored ocean current turbine presents many engineering challenges; among them are accurately predicting the stability and loads of the device. To validate computational loads and stability prediction tools, Aquantis Inc. designed, built, and tested a 1/25th scale model of their ‘C‐Plane' dual‐rotor moored ocean current turbine. This effort was conducted in cooperation with the US Naval Surface Warfare Center at the David Taylor Model Basin and was funded in part under a grant awarded to Dehlsen Associates by the U.S. Department of Energy. This multi‐stage testing effort included both a captured singlerotor test and a dynamic, moored test of the complete dual‐rotor C‐Plane. The test data is subsequently used to validate a variety of stability and loads simulations including the Navy's DCAB Code and Tidal Bladed v4.4. Specialized testing methodologies were developed for this purpose and the results are compared with computational model predictions. This testing effort investigates many aspects of moored ocean current turbine design. The captured test was essential to characterize rotor loads and stability coefficients at various blade pitch and cone angles, as well as measure rotational stall delay and unsteady rotor loads due to upstream structure wakes. The dynamic test validated stability and loads predictions of all anticipated modes of deployment and operation, depth keeping and loads avoidance, yawed flow behavior, and various failure modes. An extensive suite of sensors is employed on the C‐Plane test model including: 6 degree‐of‐freedom (DOF) load cells, 6‐DOF inertial measurement and heading sensors, rotor torque, rotor rpm, rotor position, static pressure/depth, tow speed, and mooring tension. These sensors provide a comprehensive understanding of the C‐Plane motion and essential loads during testing. A 400Hz sample rate is utilized to accurately capture transient events. The model rotors have a high degree of controllability including rampup/ ramp‐down, counter‐rotating synchronization and phase‐shift, and constant tip‐speed‐ratio regulation. Many challenging aspects of testing a moored ocean current turbine have been addressed in this effort, such as: very low Reynolds number scaled rotor design and fabrication, development of a mooring test rig capable of yawed flow, and simulating the motions of a dual rotor moored device. This test program has proven that the CPlane design has a high degree of stability in a wide range of flow conditions and computational models are capable of accurately predicting CPlane behavior.
Ocean Stream Power Generation: Unlocking a Source of Vast, Continuous, Renewable Energy
Bolin, William D. (2014-04)
This paper presents the challenges of harnessing the immense continuous kinetic energy of the flowing ocean currents. This kinetic energy has been known for centuries, but to date, no economical installation has been established that provides a continuous renewable power source to a land based power grid system. Discussed are the actions that have been taken to develop a submerged ocean system with a workable propeller. A completed scale model performance test was carried out in the sea making this system a technical readiness level TRL 7. The paper identifies some of the obvious high kinetic energy ocean locations near populated shore lines that make continuous renewable energy possible and practical.
Scaling of Spatial and Temporal Biological Variability at Marine Renewable Energy Sites
Jacques, Dale A.; Horne, John K. (2014-04)
Baseline characterization of fish and macrozooplankton is required for marine renewable energy (MRE) site developments such as offshore wind, surface wave, and tidal power. Baseline measurements typically cover a small proportion of the total project area and need to be scaled to develop monitoring programs at pilot and commercial sites after installation. Spatial representativeness, the range to which observations from a point source can be interpolated, can be used to calculate the density of point source monitoring instruments. We demonstrate a framework for calculating the spatial representativeness of stationary splitbeam echosounders used to monitor pelagic fish and macrozooplankton at MRE sites by comparing observed variability between mobile and stationary acoustic surveys at a proposed MRE tidal site in Puget Sound, WA. Three approaches were used to test the consistency of spatial representativeness estimates. First, stationary observations of nekton variability were compared to mobile observations at different spatial scales to identify the scale at which similar patterns and variability were measured. Second, correlation coefficient models generated from spatial and temporal variograms and autocorrelation were used to describe the representativeness of point sources as a function of range. Spatial Autocorrelation was used to show that nekton abundance measurements became independent at 300m, while temporal measurements became independent within 24 seconds. Third, an equation translating power law slopes of the spatial and temporal global wavelet spectrums, analogous to spectral densities, was used to translate variability between spatial and temporal measurement scales. Preliminary results indicate that spatial (Log₁₀ (Wavelet Power) = 1.24 + 0.223log₁₀(meters)) and temporal (Log₁₀(Wavelet Power) = 0.74 + 0.405log₁₀(hours) power laws are equivalent at scales of approximately one month and 1 km. Subtracting these equations gives a scalar equation to translate between spatial and temporal variability across measurement scales. A standardized spatial representativeness calculation provides an objective technique to determine minimum monitoring effort, maximizes the cost effectiveness of monitoring for developers, and ensures adequate monitoring resolution for environmental monitors.
Development of an Adaptable Monitoring Package for Marine Renewable Energy Projects Part II: Hydrodynamic Performance
Joslin, James; Rush, Ben; Stewart, Andrew; Polagye, Brian (2014-04)
The Adaptable Monitoring Package (AMP), along with a remotely operated vehicle (ROV) and custom tool skid, is being developed to support near-field (≤10 meters) monitoring of hydrokinetic energy converters. The AMP is intended to support a wide range of environmental monitoring in harsh oceanographic conditions, at a cost in line with other aspects of technology demonstrations. This paper, which is the second in a two part series, covers the hydrodynamic analysis of the AMP and deployment ROV given the strong waves and currents that typify marine renewable energy sites. Hydrodynamic conditions from the Pacific Marine Energy Center's wave test sites (PMEC) and Admiralty Inlet, Puget Sound, Washington are considered as early adoption case studies. A methodology is presented to increase the AMP's capabilities by optimizing its drag profile through a combination of computational fluid dynamic (CFD) modeling and sub-scale experiments. Preliminary results suggest that AMP deployments should be possible in turbulent environments with a mean flow velocity up to 1 m/s.
Design and Initial Component Tests of an integrated Avian and Bat Collision Detection System for Offshore Wind Turbines
Flowers, Jeremy; Albertani, Roberto; Harrison, Trevor; Polagye, Brian; Suryan, Robert M. (2014-04)
We describe the development and initial testing of a multi‐sensor instrumentation package capable of detecting avian and bat interactions with offshore wind turbines. The system design emphasizes the ability to detect collisions with the blades, tower, and nacelle of a turbine and to provide taxonomic classification of the animal involved in the collision. This system will allow the environmental impacts of offshore wind turbines to be remotely monitored and help ensure that the benefits of renewable power generation are not outweighed by mortality of protected species. Conceptual design of the complete system, initial testing of vibration sensors, and proof of concept for sensor integration and event detection are presented.
A Framework for Optimizing the Placement of Current Energy Converters
Roberts, Jesse; Nelson, Kurt; Jones, Craig; James, Scott C. (2014-04)
This study investigates the potential environmental impacts and performance of a small array of tidal energy converters (TECs) in Cobscook Bay, ME; TECs are a subset of current energy converters (CECs) that are specifically deployed in tidal channels. A previously constructed coarse-grid, regional-scale hydrodynamic model of Cobscook Bay was coupled to a refined domain centered on a proposed TEC deployment location. All models were developed with Sandia National Laboratories-Environmental Fluid Dynamics Code (SNL-EFDC). An optimization framework was then constructed that used results from the refined model to determine optimal device placement locations that maximize array performance and minimize potential environmental effects. Within the framework, environmental constraints can be included to limit CEC-induced changes in flow, sediment transport, or other physical phenomena that might affect the health of aquatic species (i.e., altering fish-swimming behavior and sediment-transport trends that could affect benthic habitat or the stability of the CEC infrastructure). Simulation results were compared between model runs with optimized array configurations, and the originally proposed deployment locations. The optimized array had roughly a 17% increase in power generation. The framework developed also provides regulators and developers with a tool to assess environmental impacts and device-performance parameters for the deployment of CEC devices.
Mooring Anchors for Marine Renewable Energy Foundations
Stevens, Robert F.; Rahim, Amir (2014-04)
With the increasing use of offshore wind turbines, it has become necessary to explore deep-water sites for locating wind farms. Floating turbines are an ideal choice for these locations. Such turbines are anchored with mooring chains to the sea floor using suction anchors, driven piles or gravity foundations. This paper presents design methods for these types of foundations. Moored gravity foundations have been used for the much larger floating oil and gas installations. These concrete foundations resist the applied wind and wave loads through the dead weight of the concrete base combined with a short skirt along the periphery. A competent bearing stratum at seabed level is necessary to facilitate a gravity base.
Array Optimization for Tidal Energy Extraction in a Tidal Channel – A Numerical Modeling Analysis
Yang, Zhaoqing; Wang, Taiping; Copping, Andrea (2014-04)
This paper presents an application of a hydrodynamic model to simulate tidal energy extraction in a tidal dominated estuary in the Pacific Northwest coast. A series of numerical experiments were carried out to simulate tidal energy extraction with different turbine array configurations, including location, spacing and array size. Preliminary model results suggest that array optimization for tidal energy extraction in a real-world site is a very complex process that requires consideration of multiple factors. Numerical models can be used effectively to assist turbine siting and array arrangement in a tidal turbine farm for tidal energy extraction.
Analysis and Proof‐of‐Concept Experiment of Liquid‐Piston Compression for Ocean Compressed Air Energy Storage (OCAES) System
Park, Joong-kyoo; Ro, Paul I.; He, Xiao; Mazzoleni, Andre P. (2014-04)
An analysis and a proof‐of‐concept experiment of liquid‐piston compression were conducted for a table‐top Ocean Compressed Air Energy Storage (OCAES) prototype. A singlecylinder‐ type piston surrounded by water was modeled and analyzed based on convection heat transfer with fully developed internal flow, the assumption adopted by earlier liquid piston study in literature. Transient numerical results of this model were calculated for a polytropic compression with different polytropic index values for 2.5‐second stroke. Also, an experimental model of the liquid piston was built with two different materials, polycarbonate and aluminum alloy, for a compression chamber. Temperature data were measured at six different stroke times to examine any difference in heat transfer rates affected by stroke frequency. The temperature within each cycle was measured during compression from 1 bar to 2.2 bars. It was found that longer stroke time induces smaller temperature rise in the air. The local temperature rise was observed to be 80 °C at 2.5‐second stroke and 7 °C at 40‐second stroke. While the simulations predict a temperature rise of 48.6 °C for a compression stroke time of 2.5 seconds, the temperature rise calculated for adiabatic compression was found to be 98.8 °C. This implies that the heat transfer characteristics of a liquid piston compression process are effective in reducing the air temperature. The experimental results with longer stroke times proved a nearisothermal nature of the liquid piston compression system. Overall, the experimental study outlined in this paper not only confirms the near‐isothermal nature of the liquid piston system but also enables further study of the expansion cycle using the liquid‐piston concept. More importantly, the current study paves a way for future work on a larger scale OCAES system demonstration based on liquid‐piston concept.

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