Dissertations / Theses: 'Tidal renewable energy'

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Muchala, Subhash. "Impact of tidal turbine support structures on realizable turbine farm power." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:12db3e87-650b-4784-b68c-c81636e72118.

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This thesis discusses the importance of tidal turbine support structures through analytical and computational modelling. A head-driven analytical channel model was first developed to determine the sensitivity of the flow to the presence and type of support structures. It showed that there was a significant potential reduction in farm power output even when only considering approximate force coefficients for rotor and support structure. To confirm these findings, computational simulations were performed on a full-scale turbine to obtain more accurate force coefficients considering full rotor-support structure interactions. The flow interaction effects between the rotor and its support structure were studied using Computational Fluid Dynamics (CFD) for different support structure shapes for a range of tidal velocities including the power-capping zone. The integrated rotor force coefficients were higher in the presence of the cylindrical support structure than the elliptical support due to the higher opposing thrust from the cylinder in the channel redirecting the flow and increasing the flow velocity over the top half of the rotor. The presence of rotor caused a drop in the stream-wise forces on the support structure. The amplitude of the stream-wise sectional forces along the support structure height was lower in the case of an elliptical than a circular cylinder due to more streamlined shape of the ellipse. At device scale, the computational model was used to study the turbine performance in the power-capping zone by pitching the blades to feather. The influence of pitch-to- feather power-capping strategy was examined by studying the forces and angle of attack on the turbine blades, and the wake at three different blade pitch angles. Increasing blade pitch angle resulted in a significant drop in the average load on the blade. Also since the tidal channel flow has a shear in its velocity profile, the influence of shear on turbine performance was studied by comparing it to the same turbine in a uniform flow. The analytical channel flow model was used to investigate the characteristics of tidal stream energy extraction for large tidal farms deployed in tidal channels with specific focus on the limitations to realizable farm power due to turbine support structure drag and constraints on volume flow rate reduction. The force coefficients dataset from computational modelling was used to obtain a better estimate of the farm power output. Support structures were seen to contribute significantly to the overall resistive force in the channel and thus reduce the overall flow rates in the channel, leading to losses in realizable power. Over a wide range of channel characteristics, realistic levels of support structure drag lead to up to a 10% reduction in realizable power, and an associated reduction in the number of turbines that can be economically installed.

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Bruder, Brittany Lynn. "Assessment of hydrokinetic renewable energy devices and tidal energy potential at Rose Dhu Island, GA." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41198.

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Current hydro-turbines aim to capture the immense energy available in tidal movements, however commonly applied technologies rely on principles more applicable in hydroelectric dams. Tidal stream currents, such as in Coastal Georgia, are not strong enough to make such turbines both efficient and economically viable. This research proposes a novel low-energy vortex shedding vertical axis turbine (VOSTURB) to combat the inefficiencies and challenges of hydro-turbines in low velocity free tidal streams. Some of the energy in tidal streams is extracted naturally from vortex shedding; as water streams past a bluff body, such as pier, low pressure vortices form alternatively on each side, inducing a rhythm of pressure differentials on the bluff body and anything in its wake. VOSTURB aims to capture this energy of the vortices by installing a hydrofoil subsequent to the bluff body. This foil, free to oscillate, translates the vortex energy into oscillatory motion, which can be converted into a form of potential energy. The presented research will act as a 'proof of concept.' It aims to assess such foil motion, or the ability of VOSTURB to capture vortex energy, and begin to assess the amount of tidal energy that can be theoretically harnessed. In this study a small scale model of VOSTURB, a cylindrical bluff body with a hammer shaped hydrofoil, was tested in a hydraulic flume for various mean flow speeds. Tangential accelerations of the foil's center of gravity were obtained through the use of an accelerometer. The acceleration data was analyzed utilizing Fourier analysis to determine the fundamental frequency of the wing oscillations. The available power to be harnessed from the oscillatory motion was then estimated utilizing this fundamental frequency. Ultimately it was found that the frequency of the VOSTURB foil oscillations corresponded highly with the theoretical frequency of vortex shedding for all moderate to high flow speeds. Low speeds were found to produce inconsistent and intermittent small oscillations. This signifies at moderate to high flow speeds, VOSTURB was able to transform some vortical energy into kinetic. The maximum average power obtained 8.4 mW corresponded to the highest flow velocity 0.27 m/s. Scaled to Rose Dhu prototype conditions this represented 50 W at a flow velocity of 0.95m/s, the maximum available at Rose Dhu. Although it was ascertained that VOSTURB could consistently capture some of the vortical energy; the percentage of which could not be calculated with certainty. Thus, the average kinetic power assessments of the foil were compared to the available power of the mean flow for each flow speed calculated by two methods: (1) over the foil's swept area; (2) the area of fluid displaced by the bluff body immediately in front of the foil. The maximum efficiency of the foil, found for the fastest flow speed was at 18% and 45% respectively. It was found that both average foil power, available flow power, and efficiency all decreased with a decrease in flow velocity. This study can serve as only a preliminary study for the effectiveness of VOSTURB as a hydro-turbine for tidal power. In the experiments, the foil was allowed to oscillate freely with little resistance. Future testing of VOSTURB needs to observe whether the vortex energy can overcome the resistive torque introduced by a generator to induce oscillatory motion as well as further optimize the foil design. While the testing in this project assesses the kinetic energy or power of the vortex shedding, this future testing will provide insight into the actual work that can actually be converted into potential energy or power. Complementing this research, both a Harmonic Analysis of Least Squares (HAMELS) and a Complex Empirical Orthogonal Function (CEOF) Analysis was conducted on available surface height and current velocity data separately from an available Regional Ocean Modeling System (ROMS) model of Coastal Georgia. Such analysis were conducted to observe spatial and temporal tidal patterns advantageous to a possible prototype installation of a tidal turbine such as VOSTURB. The more conventional HAMELS analysis, which isolates components of a signal with a certain frequency, identified temporal and spatial patterns attributed to tidal constituents. CEOF analysis, where major patterns of variance are identified not according to prescribed frequencies, was employed to identify any patterns possible not attributed to the tidal constituents. This study was also in part to observe whether the CEOF analysis could identify any patterns of tidal propagation that could not be resolved by the HAMELS analysis. The CEOF and HAMELS analysis of the surface height output produced very similar results: major modes of surface height variation due to the diurnal and semidiurnal tidal constituents propagating up the estuary. The CEOF results did not produce any additional information that could not be found through the HAMELS analysis of the constituents and presented such results in an arguably more convoluted manner. In addition, the surface height analysis provided no direct insight into areas more advantageous to tidal power. The CEOF analysis of the vector current velocity data however did provide some insight. The CEOF of the current data was able to isolate patterns of variance corresponding to the tidal constituents. However, the CEOF was also able to identify local 'hotspots' of high current magnitudes not resolved by HAMELS. These local areas of high current magnitudes, most likely due to changes in hydrodynamic conditions such as channel constrictions, are advantageous for tidal power applications. These general areas could serve as a starting point for the location selection process for a possible prototype installation of VOSTURB if the area was refined more. Ultimately for a prototype installation of VOSTURB, further experimentation and analysis is required for both the turbine design and placement, such as a power conversion methodology for the turbine and a more spatially resolute set of data to perform a CEOF analysis on. With these tasks completed, the prototype installation will be part of a larger effort between the Georgia Institute of Technology and the Girl Scouts of America to create completely sustainable "Eco-Village" on Rose Dhu Island, GA. With an extensive community outreach planned to educate the public, Rose Dhu, along with championing hydrokinetic energy, will serve as a paradigm for sustainable design and energy.

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Atwater, Joel. "Limitations on tidal-in-stream power generation in a strait." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/635.

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In the quest to reduce the release of carbon dioxide to limit the effects of global climate change, tidal-in-stream energy is being investigated as one of many possible sustainable means of generating electricity. In this scheme, turbines are placed in a tidal flow and kinetic energy is extracted. With the goal of producing maximum power, there is an ideal amount of resistance these turbines should provide; too little resistance will not a develop a sufficient pressure differential, while too much resistance will choke the flow. Tidal flow in a strait is driven by the difference in sea-level along the channel and is impeded by friction; the interplay between the driving and resistive forces determines the flow rate and thus the extractible power. The use of kinetic energy flux, previously employed as a metric for extractible power, is found to be unreliable as it does not account for the increased resistance the turbines provide in retarding the flow. The limits on extraction from a channel are dependant on the relationship between head loss and velocity. If head loss increases with the square of the velocity, a maximum of 38% of the total fluid power may be extracted; this maximum decreases to 25\% if head loss increases linearly with velocity. Using these values, the estimated power potential of BC's Inside Passage is 477MW, 13% of previous assessments. If a flow has the ability to divert through a parallel channel around the installed turbines, there are further limits on production. The magnitude of this diversion is a function of the relative resistance of impeded and diversion channels. As power extraction increases, the flow will slow from its natural rate. This reduction in velocity precipitously decreases the power density the flow, requiring additional turbine area per unit of power. As such, the infrastructure costs per watt may rise five to eight times as additional turbines are installed. This places significant economic limitations on utility-scale tidal energy production.

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Schluntz, Justine Oakley. "Tidal turbine array modelling." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b342fda1-a311-4783-8249-9b1515e0ad62.

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Computational fluid dynamics (CFD) is used in this thesis to model wind and tidal stream turbines and to investigate tidal turbine fence performance. There are two primary objectives of this work. The first is to develop and validate an actuator line method for the simulation of wind and tidal turbines which applies the blade forces to the flow field without the need for a regularisation kernel. The second is to examine tidal fences using, in part, the newly developed actuator line method. A potential flow equivalence method for determining the relative velocity to the blade chord and flow angle at the rotor blades in the actuator line method is proposed and validated. Results for simulations using this method compare favourably with those from both experiments and alternative computational methods, although the present model’s results deviate from experimental results in the vicinity of the blade tips. A CFD-embedded blade element-momentum tool is used to design rotors for operation in infinitely wide tidal fences spanning a tidal channel. Rotors are designed for fences with several different blockage ratios, with those designed for high blockage flows having greater solidity than those designed for operation in fences with lower blockage. It is found that designing rotors for operational blockage conditions can significantly improve the power output achieved by a tidal fence. Improved power output for higher blockage conditions is achieved by the application of greater thrust to the flow. Actuator line simulations of short (up to 8 turbines) fences with varying intra-rotor spacing and number of rotors confirm that hydrodynamic performance of the rotors improves as the spacing is reduced and as rotors are added to a fence. The position of a rotor within the fence impacts its performance; rotors at the ends of a fence extract reduced power compared to those at the centre of the fence, particularly for tip speed ratios greater than the design tip speed ratio.

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Moreira, Tulio Marcondes. "Augmented Tidal Resonant System: Design for Uninterrupted Power Generation." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1462460475.

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Brammer, James. "Physical and numerical modelling of Marine Renewable Energy technologies, with particular focus on tidal stream and tidal range devices." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/58699/.

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The past decade has seen a significant rise in the interest of deploying Marine Renewable Energy technologies. Tidal stream technology is developing rapidly, and developers are favouring horizontal axis turbines (HAT’s). However, vertical axis turbines (VAT’s) are better suited for shallow waters, and higher efficiencies can potentially be gained by utilising shallow water blockage effects. The Severn Estuary is an ideal deployment area in this context. Additionally, due to a large tidal range the estuary has long been the subject of tidal barrage proposals. The original ebb-only STPG barrage has recently been superseded by a two-way generation scheme, therefore the need exists for renewed research into the hydrodynamic impacts of this proposal. Furthermore, little is known about the interaction between tidal range and tidal stream technologies, and if they could coexist in the Severn Estuary. This thesis uses physical and numerical modelling techniques to assess a range of MRE technologies, with particular focus on their deployment in the Severn Estuary. Physical model tests of a number of VAT’s were conducted in a recirculating flume. Device performance and the wake characteristics were assessed, and it was demonstrated that VATS’s could potentially provide competitive performance values if deployed in shallow waters. The CFD code ANSYS CFX was used to predict the unsteady turbine behaviour at the physical model scale; good agreement was achieved with the laboratory data, particularly in predicting the wake behaviour. The CFD model TRIVAST was then applied to the Severn Estuary. Comparisons were made of the Severn Barrage schemes, as well as two hypothetical HAT and VAT arrays. The model results confirmed that vertical axis turbines are better suited to the Severn Estuary, provided that the technology is feasible. Finally, whilst the Severn Barrage proposals would eradicate the HAT resource, a lesser impact on the VAT resource was observed.

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Olczak, Alexander. "The influence of waves on tidal stream turbine arrays." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-influence-of-waves-on-tidal-stream-turbine-arrays(3ed6653f-1cc3-4e3b-ba03-5e5094a15ecc).html.

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The aim of this research was to quantify the influence of waves on arrays of tidal turbines. Experiments measured the wake of a turbine operating in combined wave-current flows, these were found to reduce velocity deficit as opposed to current only flow. The vertical region of the wake affected was dependant on the wave depth parameter, kd.RANS-BEM and Actuator Line methods were implemented within a commercial CFD code to provide computationally efficient methodologies for the simulation of both large turbine arrays and a turbine subjected to unsteady flow. For scaled experiments thrust coefficient was within 7% and 1% of the flume experiments for the RANS-BEM and Actuator Line methods respectively. The methods were found to give good prediction of a single turbine wake at distances greater than four diameters downstream, provided values of inlet turbulence intensity and length scale were equal to those measured experimentally.An unsteady Actuator Line method was used to quantify rotor loads and wake generation for a turbine operating within combined wave-current flow. The use of a streamwise pulsatile flow was found to give similar rotor and blade loads to simulations using a wave in a two phase volume of fluid simulation. The control strategy adopted by the turbine was found to greatly influence the computed rotor loads and blade bending moments. The wake generated by an Actuator Line method showed a reduction in velocity, however this was smaller than that measured experimentally for equivalent wave conditions.The accuracy with which the RANS-BEM method computed turbine loads and wakes was quantified for a number of one, two and three row arrays. The square of the disk averaged velocity encountered by turbines downstream of a single row of five turbines was found to be predicted to within 5% and 28% for an aligned and staggered arrangement respectively. For the two row arrays, the thrust of individual turbines was within 31% of the experimental measurements. The merged wake downstream of the multiple turbines was well predicted.Measurements of the wake of five porous disks showed combined wave-current flow did not alter the wake in the same manner as a single isolated disk. Measurement of wave energy over the wake showed the downstream current field altered wave propagation, causing a reduction in wave energy over the wake but an increase over the bypass flow. The accuracy of the wave model SWAN was assessed for the calculation of this change in wave characteristics. The model gave good prediction of the lateral variation of wave height over the far wake, however discrepancies in the near wake and upstream of the disk occurred.

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Defne, Zafer. "Multi-criteria assessment of wave and tidal power along the Atlantic coast of the southeastern USA." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33864.

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The increasing demand for energy and the increased depletion rate of nonrenewable energy resources call for research on renewable alternatives. Mapping the availability of these resources is an important step for development of energy conversion projects. For this purpose, the wave power potential along the Atlantic coast of the southeastern USA, and the tidal stream power along the coast of Georgia are investigated in this study. Wave power potential is studied in an area bounded by latitudes 27 N and 38 N and longitudes 82 W and 72 W (i.e. North Carolina, South Carolina, Georgia, and northern Florida). The available data from National Data Buoy Center wave stations in the given area are examined. Power calculated from hourly significant wave heights and average wave periods is compared to power calculated using spectral wave energy density. The mean power within 50 km of the shore is determined to be low, whereas higher power is available further offshore beyond the 3500 m contour line. The tidal stream power potential along the coast of the state of Georgia is evaluated based on the NOAA tidal predictions for maximum tidal currents and three dimensional numerical modeling of the currents with Regional Ocean Modeling System (ROMS). The modeling results are validated against the available measurements. This region has low to moderate average tidal currents along most of the coast, but with the possibility of very strong local currents within its complex network of tidal rivers and inlets between barrier islands. Tidal stream power extraction is simulated with a momentum sink in the numerical models at the estuary scale to investigate effect of power extraction on the estuarine hydrodynamics. It is found that different power extraction schemes might have counterintuitive effects on the estuarial hydrodynamics and the extraction efficiency. A multi-criteria method that accounts for the physical, environmental and socioeconomic constraints for tidal power conversion schemes is proposed to select favorable locations and to rank them according to their suitability. For this purpose, the model results are incorporated into a Geographical Information System (GIS) database together with other geospatial datasets relevant to the site selection methodology. The methodology is applied to the Georgia coast and the candidate areas with potential are marked.

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Abdul, Rahman Anas. "Numerical modelling of full scale tidal turbines using the actuator disc approach." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31246.

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In recent years, the actuator disc approach which employs the Reynolds-Averaged Navier-Stokes (RANS) solvers has been extensively applied in wind and tidal energy field to estimate the wake of a horizontal axis turbine. This method is simpler to administer and requires moderate computational resources in modelling a tidal turbines rotor. Nonetheless, the use of actuator disc approximation in predicting the performance of tidal devices has been limited to studies involving an extremely small disc (e.g. rotor diameter of 0.1 meter). The drawback of a small scale actuator disc model is the overestimation of essential parameters such as the mesh density and the resolution of the vertical layers, making them impractical to be replicated in a regional scale model. Hence, this study aims to explore the methodology on implementation of the Three- Dimensional (3D) actuator disc-RANS model in an ocean scale simulation. Additionally, this study also aspires to examine the sensitivity of the applied momentum source term and its validity in representing full-size tidal devices. Nonetheless, before the effectiveness of an actuator disc in a regional model can be tested, tidal flow models for the area of interest needed to be set up first. This was essential for two reasons: (a) to ensure accurate hydrodynamic flow conditions at the deployment site were replicated, (b) to give confidence in the outputs produced by the regional scale actuator disc simulations, since in-situ turbine measurement data from a real deployment site were difficult to source. This research was undertaken in two stages; in the first stage, a numerical model which can simulate the tidal flow conditions of the deployment sites was constructed, and, in the second stage, the actuator disc method which is capable of modelling an array of real scale-sized tidal turbines rotors has been implemented. In the first stage, tidal flow simulations of the Pentland Firth and Orkney Waters (PFOW) were conducted using two distinct open-source software - Telemac3D, which is a finite element based numerical model, and Delft3D, which is a finite difference based model. Detailed methodologies in developing a 3D tidal flow model for the PFOW using both numerical models were presented, where their functionality, as well as limitations were explored. In the calibration and validation processes, both models demonstrated excellent comparison against the measured data. However, Telemac3D was selected for further modelling of the actuator disc considering the model's capability to perform parallel computing, together with its flexibility to combine both structured and unstructured mesh. In the second stage, to examine the actuator disc's accuracy in modelling a full size tidal device, the momentum source term was initially applied in an idealised channel study, where the presence of a 20-meter diameter turbine was simulated for both single and array configurations. The following parameters were investigated: (i) size of the unstructured mesh utilised in the computational domain, (ii) variation in disc's thickness, (iii) resolution of the imposed structured grid to represent turbine's enclosure, (iv) variation in the vertical layers, and (v) influence of hydrostatic and non-hydrostatic formulations on the models' outputs. It is to be noted that the turbine's support structures have not been included in the modelling. The predicted velocities and computed turbulence intensities from the models were compared against laboratory measurement data sourced from literature, where excellent agreement between the model outputs and the data from literature was observed. In essence, these studies highlighted the efficiency and robustness of the applied momentum source term in replicating the wake profiles and turbulence characteristics downstream of the disc, hence providing credence in implementing the actuator disc method for a regional scale application. Subsequently, the validated actuator disc method was applied to the Inner Sound region of the Pentland Firth to simulate arrays of up to 32 tidal turbine rotors. The wake development, flow interactions with the rotor arrays, and flow recovery at the Inner Sound region have been successfully mapped. Also, this study highlighted the importance of employing optimal numerical margins, specifically for the structured grid and horizontal planes, as both parameters were relevant in defining the disc's swept area. As published materials on the implementation of actuator disc approach within a regional scale model is still scarce, it was aspired that this work could provide some evidence, guidance and examples of suggested best practice in effort to fill the research gap in modelling tidal turbine arrays using the actuator disc approach.

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Martinez, Fabien. "Drag study of the nacelles of a tidal stream device using CFD." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/7440.

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Nowadays, renewable energy is in full growth. In particular, offshore wind farms will be at the centre of UK energetic strategy in the coming years. However, other types of marine renewable are still at an early development stage. That is the case for tidal energy. Many projects have been undertaken but there is no candidate for competitive commercial applications yet. Deltastream is one of these numerous pioneering projects. It consists of a set of three marine current turbines mounted on a triangular base put down onto the seabed. The device is not moored and no harm is done to the environment. However, that makes the structure more sensitive to water flows. And it is important to ensure that it will remain at its location and not being carried along with the tidal streams. Using CFD, the present study aims to evaluate the drag on the nacelles of the structure and come up with solutions to reduce it as much as possible.

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Fleming, Conor F. "Tidal turbine performance in the offshore environment." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:f51fd313-1589-4e9c-98cc-ae6e64c1184b.

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A three dimensional computational model of a full scale axial flow tidal turbine has been used to investigate the effects of a range of realistic environmental conditions on turbine performance. The model, which is based on the Reynolds averaged Navier-Stokes equations, has been developed using the commercial flow solver ANSYS Fluent. A 1:30 scale tidal turbine is simulated in an open channel for comparison to existing experimental data. The rotor blades are directly resolved using a body-fitted, unstructured computational grid. Rotor motion is enabled through a sliding mesh interface between the rotor and the channel boundaries. Reasonably good agreement in thrust and power is observed. The computed performance curves are offset from the measured performance curves by a small increment in rotor speed. Subsequently, a full scale axial flow turbine is modelled in a variety of conditions representative of tidal channel flows. A parametric study is carried out to investigate the effects of flow shear, confinement and alignment on turbine performance, structural loading, and wake recovery. Mean power and thrust are found to be higher in sheared flow, relative to uniform flow of equivalent volumetric flow rate. Large fluctuations in blade thrust and torque occur in sheared flow as the blade passes through the high velocity freestream flow in the upper portion of the profile and the lower velocity flow near the channel bed. A stronger shear layer is formed around the upper portion of the wake in sheared flow, leading to enhanced wake mixing. Mean power and thrust are reduced when the turbine is simulated at a lower position in a sheared velocity profile. However, fluctuations in blade loading are increased due to the higher velocity gradient. The opposite effects are observed when the turbine operates at greater heights in sheared flow. Flow misalignment has a negative impact on mean rotor thrust and power, as well as on unsteady blade loading. Although the range of unsteady loading is not increased significantly, additional perturbations are introduced due to interactions between the blade and the nacelle. A deforming surface is introduced using the volume-of-fluid method. Linear wave theory is combined with the existing free surface model to develop an unsteady inflow boundary condition prescribing combined sheared flow and free surface waves. The relative effects of the sheared profile and wave-induced velocities on turbine loading are identified through frequency analysis. Rotor and blade load fluctuations are found to increase with wave height and wave length. In a separate study, the performance of bi-directional ducted tidal turbines is investigated through a parametric study of a range of duct profiles. A two dimensional axi-symmetric computational model is developed to compare the ducted geometries with an unducted device under consistent blockage conditions. The best-performing ducted device achieves a peak power coefficient of approximately 45% of that of the unducted device. Comparisons of streamtube area, velocity and pressure for the flow through the ducted device shows that the duct limits the pressure drop across the rotor and the mass flow through the rotor, resulting in lower device power.

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Banerjee, S. "Ocean energy assessment : an integrated methodology." Thesis, Coventry University, 2011. http://curve.coventry.ac.uk/open/items/16196d0d-e671-489a-ba71-f20cdb6c8df3/1.

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The huge natural energy resources available in the world’s oceans are attracting increasing commercial and political interest. In order to evaluate the status and the degree of acceptability of future Ocean Energy (OE) schemes, it was considered important to develop an Integrated Assessment Methodology (IAM) for ascertaining the relative merits of the competing OE devices being proposed. Initial studies included the gathering of information on the present status of development of the ocean energy systems on wave, OTEC and tidal schemes with the challenges faced for their commercial application. In order to develop the IAM, studies were undertaken for the development and standardization of the assessment tools focussing on: • Life Cycle Assessment (LCA) on emission characteristics. • Energy Accounting (EA) studies. • Environmental Impact Assessment (EIA) over different environmental issues. • Resource captures aspects. • Defining economy evaluation indices. The IAM developed from such studies comprised of four interrelated well defined tasks and six assessment tools. The tasks included the identification of the modus operandi on data collection to be followed (from industry) for assessing respective OE devices, and also advancing relevant guidelines as to the safety standards to be followed, for their deployment at suitable sites. The IAM as developed and validated from case studies in ascertaining relative merits of competing OE devices included: suitable site selection aspects with scope for resource utilisation capability, safety factors for survivability, scope for addressing global warming & energy accounting, the environmental impact assessment both qualitatively and quantitatively on different environmental issues, and the economic benefits achievable. Some of the new ideas and concepts which were also discovered during the development of the IAM, and considered useful to both industry and researchers are given below: • Relative Product Cost (RPC) ratio concept- introduced in making an economic evaluation. This is considered helpful in sensitivity analysis and making design improvements (hybridising etc) for the cost reduction of OE devices. This index thus helps in making feasibility studies on R&D efforts, where the capital cost requirement data and life span of the device is not well defined in the primary stages of development. • Determination of the threshold limit value of the barrage constant - considered useful in determining the efficacy of the planning process. The concept ascertained the relative efficiency achieved for various barrage proposals globally. It could also be applied to suggest the revisions required for certain barrage proposals and also found useful in predicting the basin area of undefined barrage proposal for achieving economic viability. • Estimations made on the future possibility of revenue earnings from the by-products of various OTEC types, including the scope of chemical hubs from grazing type OTEC plants. • Determination of breakeven point- on cost versus life span of wave and OTEC devices studied, which is useful in designing optimum life of the concerned devices. The above stated multi-criterion assessment methodology, IAM, was extended leading to the development of a single criterion model for ascertaining sustainability percent achievable from an OE device and termed IAMs. The IAMs was developed identifying 7 Sustainability Development Indices (SDI) using some the tools of the IAM. A sustainability scale of 0-100 was also developed, attributing a Sustainability Development Load Score (SDLS) percentage distribution pattern over each SDIs, depending on their relative importance in achieving sustainability. The total sum of sustainability development (SD) gained from each SDI gave the IAMs (for the concerned device), indicating the total sustainable percentage achieved. The above IAMs developed, could be applied in ranking OE devices alongside the unsustainable coal power station. A mathematical model of estimating the IAMs was formulated, in order to ascertain the viability to the sustainable development of any energy device. The instruments of IAM and IAMs which have been developed would be helpful to the OE industry in ascertaining the degree of acceptability of their product. In addition it would also provide guidelines for their safe deployment by assessing the relative merits of competing devices. Furthermore, IAM and IAMs would be helpful to researchers undertaking feasibility studies on R&D efforts for material development research, ‘hybridization studies’ (as also new innovations), cost reduction, the performance improvement of respective devices, and any economic gains. With future advancements in OE systems and the availability of field data from large scale commercial applications, the specific values/data of the IAM & IAMs may be refined, but the logic of the models developed in this research would remain the same.

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Buckland, Hannah. "Combined current, wave and turbulent flows and their effects on tidal energy devices." Thesis, Swansea University, 2014. https://cronfa.swan.ac.uk/Record/cronfa42509.

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This thesis considers the effect of disruptive waves and turbulence on a horizontal axis tidal stream turbine (TST), in terms of performance and survivability. The TST reaction to transient fluid flow is modelled analytically using Blade Element Momentum Theory (BEMT). Standard BEMT corrections are evaluated for the TST application and an alternative optimisation method is proposed for the steady state BEMT, improving compatibility with transient and depth dependent inflow, as well as the non-dimensionalisation constant needed to calculate the performance coefficients. Also, an alternative BEMT tip and hub loss implementation has led to a significant improvement of the turbine axial force prediction and in the high induction region. Validation studies are presented for BEMT coupled with regular, nonlinear wave theory and good agreement is found with published experimental data. A novel method to simulate irregular sea states is developed to couple with BEMT and a combined reactive coupling of waves and current is implemented. The TST performance in an irregular sea state is considered against turbine performance with real ADCP data and a good agreement is found. This work evaluates the BEMT implementation for the specific application of modelling TST's and significantly improves the fundamental theory, applicability and quality of results in this case.

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Toupin, Mathieu. "Scientific Validation of Standards for Tidal Current Energy Resource Assessment." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34212.

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The tidal current energy resource is challenging to assess with accuracy and precision. An accepted standard methodology is lacking, which in turn perpetuates uncertainty and hinders the industry’s development. Technical Committee 114 of the International Electro-technical Commission (IEC-TC-114) is working to develop a standard for emerging tidal energy conversion systems. The draft standard prescribes methods for determining, objectively and reliably, the scale and character of tidal current energy resources at a site. The IEC-TC-114 draft standard for tidal energy resource assessment and characterisation has not yet been tested in a real world case study. Hence, it is not yet known whether the proposed methods will yield the desired outcome. This research has adopted the Fundy Ocean Research Center for Energy (FORCE) project in Minas Passage, Nova Scotia, for pilot application of the draft standard on tidal current resource assessment. The Bay of Fundy, located on the Atlantic coast of North America between the Canadian provinces of New Brunswick and Nova Scotia, is known for having the highest tidal range in the world and has long been recognised as an ideal stage for tidal energy development. The thesis is presented in three main parts. Firstly, the latest peer-reviewed scientific literature is summarised and the standard is reviewed in view of lessons learned. The aim of this exercise is to establish a scientific basis for and to develop suggestions towards improving and extending future revisions of the standard. Secondly, a comprehensive assessment of the tidal current energy resource at the FORCE project site is conducted in a manner that is consistent with IEC-TC-114 protocol based on available measurements from static current profiler surveys and a two-dimensional hydrodynamic model of the upper Bay of Fundy developed for this study. Thirdly, a sensitivity analysis is performed to determine the main sources of error and uncertainty affecting resource assessment, a topic which has yet to be addressed in the literature.

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Stringer, Robert. "Numerical investigation of cross-flow tidal turbine hydrodynamics." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760981.

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The challenge of tackling global climate change and our increasing reliance on power means that new and diverse renewable energy generation technologies are a necessity for the future. From a number of technologies reviewed at the outset, the cross-flow tidal turbine was chosen as the focus of the research. The numerical investigation begins by choosing to model flow around a circular cylinder as a challenging benchmarking and evaluation case to compare two potential solvers for the ongoing research, ANSYS CFX and OpenFOAM. A number of meshing strategies and solver limitations are extracted, forming a detailed guide on the topic of cylinder lift, drag and Strouhal frequency prediction in its own right. An introduction to cross-flow turbines follows, setting out turbine performance coefficients and a strategy to develop a robust numerical modelling environment with which to capture and evaluate hydrodynamic phenomena. The validation of a numerical model is undertaken by comparison with an experimentally tested lab scale turbine. The resultant numerical model is used to explore turbine performance with varying Reynolds number, concluding with a recommended minimum value for development purposes of Re = 350 × 103 to avoid scalability errors. Based on this limit a large scale numerical simulation of the turbine isconducted and evaluated in detail, in particular, a local flow sampling method is proposed and presented. The method captures flow conditions ahead of the turbine blade at all positions of motion allowing local velocities and angles of attack to be interrogated. The sampled flow conditions are used in the final chapter to construct a novel blade pitching strategy. The result is a highly effective optimisation method which increases peak turbine power coefficient by 20% for only two further case iterations of the numerical solution.

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Krehnovi, Emily M. "Resonate Energy Conversion: Analysis of a Lunar Tide Power Plant Using a Variable Area Pipe." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1366991503.

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Cousineau, Julien. "Hydrodynamic Impacts of Tidal Lagoons in the Upper Bay of Fundy." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/23060.

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Among sources of renewable energy, development of tidal energy has traditionally been plagued by relatively high costs and limited availability of sites with sufficiently high tidal amplitudes or flow velocities. However, many recent technology developments and improvements, both in design (e.g. dynamic tidal power, tidal lagoons) and turbine technology (e.g. new axial turbines, crossflow turbines), showed that the economic and environmental costs may be brought down to competitive levels comparing to other conventional energy sources. It has long been identified that the Bay of Fundy is one of the world’s premier locations for the development of tidal power generating systems, since it has some of the world’s largest tidal ranges. Consequently, several proposals have been made in the recent years to find economical ways to harness the power of tides. Presently, there is considerable interest in installing tidal lagoons in the Bay of Fundy. The lagoon concept involves temporarily storing seawater behind an impoundment dike and generating power by gradually releasing the impounded seawater through conventional low-head hydroelectric turbines. A tidal lagoon will inherently modify the tides and tidal currents regime in the vicinity of the lagoon, and possibly induce effects that may be felt throughout the entire Bay of Fundy. The nature of these hydrodynamic impacts will likely depend on the size of the tidal lagoon, its location, and its method of operation. Any changes in the tidal hydrodynamics caused by a tidal lagoon may also impact on the transport of sediments throughout the region and upset ecosystems that are well adapted to existing conditions. The scale and character of the potential hydrodynamic impacts due to tidal lagoons operating in the Bay of Fundy have not been previously investigated. The present study endeavours to investigate these potential impacts to help the development of sustainable, science-based policies for the management and development of clean energy for future generations. After outlining fundamental aspects of tidal power projects taken in consideration in the Bay of Fundy, an analysis of present knowledge on tidal lagoons was conducted in order to provide a focus for subsequent investigations. Hydrodynamic modeling was used to quantify any of the potential hydrodynamic changes induced in the Bay of Fundy due to the presence of tidal lagoons. In the last part of the thesis, new relationships were derived in order to describe the amount of energy removed from tidal lagoons associated with its hydrodynamic impacts.

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Berry, Matthew James. "Hydrodynamic analysis of the momentum-reversal and lift tidal turbine." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/29541.

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Tidal energy has the potential to make a valuable contribution to meeting future global energy demands. Converting the energy of tidal streams into useful electricity can be achieved with use of tidal-stream turbines, such as the Momentum-Reversal and Lift (MRL) device. This turbine utilises a blade motion where each blade rotates continuously through 180° about its own axis for every 360° of turbine rotation. The aim of the design is to harness both useful lift and drag forces when rotating at relatively slow speeds. However, no detailed analysis of the time-varying fluid dynamic behaviour of the turbine has been undertaken before this study. The primary aim of this study has been to further understanding of the performance characteristics of the MRL turbine design, focusing on a laboratory- scale device. The study has analysed both the time-averaged and time-varying torque and power output, and the associated fluid-dynamic structure of flow through the turbine. A secondary aim was to generate data that can be used by other researchers who focus on the wake generation of the MRL tidal turbine. This study has used OpenFOAM to develop a time-dependent RANS CFD model and investigate the performance of the MRL turbine. To allow validation of the CFD model, experiments were firstly undertaken in order to measure the cycle-mean torque and power output of the turbine when operating in a laboratory flume. Measurements of the flow velocity at a number of upstream and downstream locations were also taken, in order to allow comparison with the CFD simulation results, where appropriate. Also, in order to allow validation of the CFD approach against time-varying data, the motion of the turbine blades was analysed. This allowed suitable experimental test cases to be identified from the literature and CFD simulation results have been compared to these. A detailed sensitivity analysis of the MRL turbine CFD model was carried out, followed by two-dimensional simulations of the turbine involving a single-blade and three-blades. Three-dimensional simulations were also undertaken, with results compared to the gathered experimental results. Finally, the effect of varying turbine solidity was investigated with the CFD model. Overall it was found that the CFD simulations successfully reproduce the rotational speed at which maximum torque and power are developed. However, the three-dimensional simulations significantly over-predict the magnitude of results in comparison to the gathered experimental results. Regardless, the two- and three-dimensional simulations have allowed detailed analysis of the flow behaviour and structures that are responsible for the development of blade forces and turbine torque.

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Lande-Sudall, David. "Co-located offshore wind and tidal stream turbines." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/colocated-offshore-wind-and-tidal-stream-turbines(72acb21d-1b88-45ad-b944-3f9664330420).html.

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Co-location of offshore wind turbines at sites being developed for tidal stream arrays has been proposed as a method to increase capacity and potentially reduce the cost of electricity compared to operating either technology independently. This research evaluates the cost of energy based on capital expenditure and energy yield. It is found that, within the space required around a single 3 MW wind turbine, co-location provides a 10-16% cost saving compared to operating the same size tidal-only array without a wind turbine. Furthermore, for the same cost of electricity, a co-located farm could generate 20% more yield than a tidal-only array. These results are based on analysis of a case-study site in the Pentland Firth. Wind energy is assessed using an eddy viscosity wake model in OpenWind, with a 3 MW rated power curve and thrust coefficient from a Vestas V90 turbine. Three years of wind resource data is from the UK Met Office UK Variable (UKV) 1.5 km numerical model and corrected against a 400 m Weather Research and Forecasting (WRF) model run over the site. Tidal stream energy is modelled using a semi-empirical superposition of self-similar plane wakes, with a generic 1 MW rated power curve and thrust based on a full-scale, fixed-pitch turbine. Coincident tidal resource data is from the Forecasting Ocean Assimilation Model (FOAM) at 7.5 km resolution and correlated with a 150 m ADvanced CIRCulation model (ADCIRC). Wave parameters are corrected from ERA-Interim data with six months of wave buoy data. Multiple tidal turbine array layouts are considered, with maximum tidal energy generated for a staggered array with spacing of 20 tidal turbine diameters, Dt , streamwise and 1.5Dt cross-stream. However, cheapest cost of electricity from the tidal-only array, was found for a single row of turbines, due to minimal wake effects. Laboratory experiments were undertaken to validate the superposition wake model for use with large, shared support structures. Two rotors mounted either side of a central tower generate a peak wake velocity deficit 70% greater than predicted by superposition. This was due to high local blockage and a complex near-wake structure, with a corresponding increase in tower drag of 9%. Further experiments evaluated the impact of oblique inflow on turbines yawed at +/-15 degrees. These results validated a theoretical cosine correction for thrust coefficient and characterised the centreline wake drift with downstream distance. Extreme environmental loads for a shared support structure, compared to structures for wind-only and tidal-only, have also been modelled. A non-linear wave model was used to represent a single wave form with 1% occurrence for each hour of time-series data. Overturning moment about the base of a shared support, with one wind and two tidal turbines, was found to be 4.5% larger than for a wind-only turbine in strong current and with turbines in different operational states. Peak loads across the tidal array were found to vary by 2.5% and so little load reduction benefit could be gained by locating a shared support in a more sheltered area of the array.

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Grabbe, Mårten. "Hydro-Kinetic Energy Conversion : Resource and Technology." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-195942.

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The kinetic energy present in tidal currents and other water courses has long been appreciated as a vast resource of renewable energy. The work presented in this doctoral thesis is devoted to both the characteristics of the hydro-kinetic resource and the technology for energy conversion. An assessment of the tidal energy resource in Norwegian waters has been carried out based on available data in pilot books. More than 100 sites have been identified as interesting with a total estimated theoretical resource—i.e. the kinetic energy in the undisturbed flow—in the range of 17 TWh. A second study was performed to analyse the velocity distributions presented by tidal currents, regulated rivers and unregulated rivers. The focus is on the possible degree of utilization (or capacity factor), the fraction of converted energy and the ratio of maximum to rated velocity, all of which are believed to be important characteristics of the resource affecting the economic viability of a hydro-kinetic energy converter. The concept for hydro-kinetic energy conversion studied in this thesis comprises a vertical axis turbine coupled to a directly driven permanent magnet generator. One such cable wound laboratory generator has been constructed and an experimental setup for deployment in the river Dalälven has been finalized as part of this thesis work. It has been shown, through simulations and experiments, that the generator design at hand can meet the system requirements in the expected range of operation. Experience from winding the prototype generators suggests that improvements of the stator slot geometry can be implemented and, according to simulations, decrease the stator weight by 11% and decrease the load angle by 17%. The decrease in load angle opens the possibility to reduce the amount of permanent magnetic material in the design.

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Foran, Derek. "Experimental and Numerical Modeling of a Tidal Energy Channeling Structure." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32387.

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Tidal power, or the use of tides for electricity production, exists in many forms including tidal barrages, which exploit tidal head differentials, and turbines placed directly in regions with large tidal current velocities. The latter is actively being investigated in many countries around the world as a means of providing renewable and wholly predictable electricity (cf. wind, solar and wave power). The expansion of the in-stream tidal industry is hindered however by several factors including: turbine durability, deployment and maintenance costs, and the lack of abundant locations which meet the necessary current velocities for turbine start-up and economic power production. A new novel type of augmentation device, entitled the ‘Tidal Acceleration Structure’ or TAS (Canadian patent pending 2644792), has been proposed as a solution to the limited number of coastal regions which exhibit fast tidal currents. In preliminary investigations, the TAS, a simple Venturi section consisting of walls extending from the seafloor to above the high water mark in an hourglass shape, was found as able to more than double current velocities entering the device. The results indicated a significant advantage over other current channeling technologies and thus the need for more in-depth investigations. The main objective of the present study was to optimise the design of the TAS and to predict the power that a turbine placed within it could extract from flow. To do this, two principal methods were employed. Firstly, a 1:50 scale model of the TAS was tested and its shape optimised in a 1.5 m wide flume. Secondly, a 3D numerical model (ANSYS Fluent) was used for comparison with the experimental results. During the tests, a TAS configuration was found that could accelerate upstream velocities by a factor of 2.12. In separate tests, turbines were simulated using Actuator Disc Theory and porous plates. The TAS-plate combination was found to be able to extract up to 4.2 times more power from flow than the stand-alone plate, demonstrating that the TAS could provide turbines with a significant advantage in slower currents. Though further research is needed, including the testing of a larger TAS model in conjunction with a small in-stream turbine, the results of this thesis clearly demonstrate the potential of the TAS concept to unlock vast new areas for tidal energy development.

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Osu, Victor Richard. "A critical evaluation of the prospects for a transition towards ocean based renewable energy development in Nigeria." Thesis, Robert Gordon University, 2017. http://hdl.handle.net/10059/2455.

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The move towards addressing two pertinent energy challenges that is access to electricity and climate change has seen the transition towards sustainable forms of energy including Ocean Based Renewable Energy (OBRE). However, much work remains to be done in understanding the critical success factors that could enable such potential transition, especially in the area of OBRE electricity generation. This research addresses this concern by drawing on transition theory and frameworks to critically evaluate the prospects towards OBRE development in Nigeria. The rationale for the study stems from issues around the inadequate supply of electricity, which has become a profound concern and, where its absence is mostly observed in rural and remote areas including coastal communities. Based on an interpretative philosophical stance, the study adopted a qualitative approach for conducting the research. In-depth semi-structured interviews were used to collect data from twenty-seven research participants. The research findings revealed that there is scope for transitioning towards OBRE electricity generation. However, this potential may be hindered by key features of the incumbent socio-technical regime: inconsistency of statements in formal policy documents; unclear institutional arrangements to foster renewable energy development; and lack of regulatory and market support mechanisms, which keep renewable energy development at the margins. Nevertheless, the study found certain perceived critical success factors that when considered could aid in facilitating OBRE development in Nigeria. These included, in particular, meaningful stakeholder engagement that aimed to harmonise the diverse interests of key actors’ and the role of adequate political governance to facilitate OBRE design and implementation. The research concludes by developing a conceptual intervention model called the OBRE Transition Model. This model argues that through more meaningful engagement with pertinent stakeholders’ and stronger political commitment, the prospect for a transition towards OBRE development in Nigeria could be accomplished. This thesis is the first of its kind to study the prospects for a transition towards OBRE innovation in West Africa. Additionally, the model that has been developed is now going to be corroborated in an OBRE project in Nigeria, thus, forming the evidence on the model’s potential applicability for future study.

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Lalander, Emilia, Mårten Grabbe, and Mats Leijon. "On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers." Uppsala universitet, Elektricitetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-195499.

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Tidal currents and rivers are promising sources of renewable energy given that suitable turbines for kinetic energy conversion are developed. To be economically and technically feasible, a velocity distribution that can give a high degree of utilization (or capacity factor), while the ratio of maximum to rated velocity is low would be preferable. The rated velocity is defined as the velocity at which rated power is achieved. Despite many attempts to estimate the resource, however, reports on the possible degree of utilisation from tidal currents and rivers are scarce. In this paper the velocity distribution from a number of regulated rivers, unregulated rivers and tidal currents have been analysed regarding the degree of utilisation, the fraction of converted energy and the ratio of maximum to rated velocity. Two methods have been used for choosing the rated velocity; one aiming at a high fraction of converted energy and one aiming at a high degree of utilisation. Using the first method, with a rated velocity close to the maximum velocity, it is unlikely that the turbine will reach the cut-out velocity. This results in, on average, a degree of utilisation of 23% for regulated rivers, 19% for unregulated rivers and 17% for tidal currents while converting roughly 30-40% of the kinetic energy. Choosing a rated velocity closer to the mean velocity resulted in, on average, a degree of utilisation of 57% for regulated rivers, 52% for unregulated rivers and 45% for tidal currents. The ratio of maximum to rated velocity would still be no higher than 2.0 for regulated rivers, 1.2 for unregulated rivers and 1.6 for tidal currents. This implies that the velocity distribution of both rivers and tidal currents is promising for kinetic energy conversion. These results, however, do not include weather related effects or extreme velocities such as the 50-year velocity. A velocity factor is introduced to describe what degree of utilisation can be expected at a site. The velocity factor is defined as the ratio U-max/U-rate at the desired degree of utilisation, and serves as an early indicator of the suitability of a site.

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Mcnaughton, James. "Turbulence modelling in the near-field of an axial flow tidal turbine in Code_Saturne." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/turbulence-modelling-in-the-nearfield-of-an-axial-flow-tidal-turbine-in-codesaturne(54c9b513-2472-4c61-a521-8ef73428465b).html.

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This Thesis presents simulation of flow past laboratory-scale and full-scale tidal stream turbines (TST) using EDF's open-source CFD solver Code_Saturne. The work shows that detailed results may be obtained with confidence and that greater information on the loading and wake structure is available than other methods, such as blade element momentum theory.Results are obtained using a new sliding-mesh method that has been implemented in Code_Saturne as part of this work. The sliding-mesh method uses internal Dirichlet boundary conditions with values on the interface prescribed via a halo-point method. Parallel performance is optimised by a carefully-chosen method of exchanging information between specific processes. Validation is provided for flow past a rotating cylinder and a sphere.For the laboratory-scale TST, Reynolds-Averaged Navier-Stokes models are used to model turbulence. The k-omega-SST and Launder-Reece-Rodi (LRR) models yield good agreement with experimental values of power and thrust coefficients as a function of tip-speed ratio (TSR). The standard k-epsilon model is shown to perform poorly due to an overprediction of turbulent kinetic energy upstream of the rotor plane. The k-omega-SST model is then used to examine wake behaviour for parametric studies of turbulence intensity and TSR. Increased turbulence levels are shown to reduce the downstream propagation of the wake because of increased mixing. The near wake is influenced by the TSR, whilst the far wake is independent of TSR.The predicted effect of tidal conditions typical of the EMEC test site are considered for flow past Tidal Generation Limited's 1MW TST. The effect of sheared-velocity profiles leads to an increase in loading on an individual turbine blade at the point of a rotation where velocity shear is greatest. The effect of increased yaw angle leads to large fluctuations of the power coefficient, but smaller fluctuations of the thrust coefficient. Mean values of thrust and power decrease as a function of the cosine of the yaw angle and yaw angle squared respectively.

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Mashayekh, Poul Hossein [Verfasser], and Jan [Akademischer Betreuer] Backhaus. "Modelling tidal processes in the Persian Gulf : With a view on Renewable Energy / Hossein Mashayekh Poul. Betreuer: Jan Backhaus." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1111778558/34.

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Alkeaid, Majed Mohammed G. "Study of NEOM city renewable energy mix and balance problem." Thesis, KTH, Elkraftteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235535.

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It is important for NEOM management in the contemporary world to put in place NEOM projects using the available resources. The region in which the NEOM project is spacious and vast with conditions suited to generate energy from solar and wind. The NEOM projectis expected to be set up in the very resourceful state of Saudi Arabia. The purpose of the study is to assist in setting up a sustainable city through the exploitation of solar and wind energy. The aim of the study was to assist in the generation of more than 10 GW renewable energy to replace approximately 80,000 barrels of fossil energy. The problem of coming up with renewable and sustainable energy from the unexploited sources is addressed. The renewable city is expected to be a technological hub based on Green Energy with 100% renewable energy, which is correspond to 72:4GW. Freiburg and Masdar as renewable cities are used as case studies in the research. NEOM power generation capacity is capable to cover Saudi Arabia power generation capacity (approximately 71GW), which is more than enough for a city. The study reveals that the total power generation from wind farms, tidal farms, solar stations, and solar power tower stations are 9:1373GW, 4:76GW, 57:398GW and 1:11GW respectively. Saudi Arabia has plans to set up 16 nuclear plants (17 GW each) for energy purposes (total of 272 GW), which will be part of Saudi Arabia national grid and will be more than enough to cover NEOM electricity demand in case NEOM does not reach demand capacity. In case NEOM energy does not meet the demand, electricity generation from 16 Nuclearpower plants generating 17GW each, and 6 Natural underground batteries with a capacity of 120MW each are recommended. The study results can be applied in NEOM Institute of Science and Technology for further research on renewable energy. The findings can also be used for research extension of HVDC transmission lines between NEOM and Saudi Arabia main grid, Egypt, and Jordan.
Det är viktigt för NEOM projektets ledning att planera och införa projektet med hjälp av förnybara energiresurser på plats. Regionen är rymligt och stort och är en lämplig plats för att kunna generera tillräcklig med energi från sol och vind för energiförsörjning av området. Syftet med studien är att studera en pågående planering och byggnation av en hållbar stad med upp till 10 GW förnybar energi som motsvarar cirka 80 000 fat fossil bränsle. Problem och utmaningar för att försörja en hel stad med förnybara energiresurser kommer att diskuteras. Den förnybara staden förväntas vara ett föredöme för 100% förnybar energi, vilket i kapacitetssammanhang motsvarar 72:4GW, vilket är mer tillräckligt än behovet för NEOM staden. Freiburg och Masdar städer används som fallstudier i examensarbetet. NEOMs kraftproduktionskapacitet kan täcka behovet av hela landet som uppgår till 71GW. Studien visar att den totala kraftproduktionskapaciteten från olika förnybara energiresurser såsom vindkraftparker, tidvattenanläggningar, solcellkraftverk och soltornskraftverk med en kapacitet av 9:1373GW,4:76GW, 57:398GW och 1:11GW respektive kan uppgå till 72:4GW. Saudiarabien har planer på att skaffa 16 kärnkraftverk (17GW vardera) med en total kapacitet på 272GW som kommer att ingå i Saudiarabiens nationella satsningar för framtidens elproduktion och det kan täcka elbehovet om NEOM inte når efterfrågekapaciteten. Utöver ovan har studien föreslagit 6 underjordiska batterier med en kapacitet på 120MW per batteri. Studieresultaten kan användas för kompetensuppbyggnad och vidare forskning om förnybara energiresurser för NEOM Institute of Science and Technology. Resultaten kan också användas för teknikutveckling och forskning inom HVDC- överföringsledningar mellan NEOM, Saudiarabiens huvudnät, Egypten och Jordanien.

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Yuen, Katarina. "System Perspectives on Hydro-Kinetic Energy Conversion." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-181555.

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Free-flowing water currents such as tides and unregulated water courses could contribute to world electricity production given the emergence of robust technical solutions for extracting the energy. At Uppsala University, a concept for converting the energy in water currents to electricity using a vertical axis turbine with fixed blade-pitch and a direct-drive permanent magnet generator is studied. Technological equipment for extracting energy from water currents can be studied at desktop to some extent, but physical realizations, first in a laboratory setting, and later in a natural aquatic setting, are necessary. For this reason, a laboratory generator has been constructed and evaluated, and an experimental setup comprising turbine, generator and control system has been constructed. The turbine and generator are to be deployed in the Dalälven River in Söderfors, and operated from an on-land control station. The author has worked with constructing and evaluating the low-speed laboratory generator, participated in the design and construction of the Söderfors generator, and designed and constructed the control system for Söderfors. The generator design incorporates a low rotational speed, permanent magnets, and many poles, in order to adapt the generator to the nature of water currents. Simulations and experimental data for the laboratory prototype have been compared and show that the simulation tool used is adequate for design studies of this type of generator. The generator has also been shown to be able to operate with the intended turbine design and range of water velocities. The control system to be used in Söderfors has been tested in a laboratory environment. Simulations of the control system show that it should be able to operate the turbine and generator at the desired rotational speeds in water velocities up to about 1.8 m/s. Simulations of the system have also shown that maximizing system power output may not correspond with maximizing turbine power.

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Vieira, Michelle Ann. "An Integrated Closed Convergent System for Optimal Extraction of Head-Driven Tidal Energy." UNF Digital Commons, 2018. https://digitalcommons.unf.edu/etd/848.

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As the demands for energy increased with the global increase in population, there is a need to create and invest in more clean and renewable energy sources. Energy derived from the movement of the tides is an ancient concept that is currently being harnessed in a handful of large tidal range locations. However, the need to move from fossil fuel driven energy sources to those that are clean and non-polluting is a priority for a sustainable future. Globally, hydropower potential is estimated to be more than 16,400-Terawatt hours annually. Given that the electricity consumption worldwide was at 15,068-Terawatt hours in 2016, if properly utilized, hydropower could supply a substantial percentage of current demand. Most of the current hydropower supply is drawn from well-established dams and tidal barrage systems. However, tidal power plants that harness the change in water height and flow along the coast (i.e. using tidal energy) have the potential to push these figures even higher. Although there is no exact number for lengths of global coastlines, there are estimates that put that number between 220,000 and 880,000 miles of coasts. These opportunities in tidal energy technologies that harness energy from the sea may one day be the key to solving our energy crises. This research explored in detail a closed, convergent system for optimal extraction of head-driven tidal energy with minimal adverse environmental effects. The long-term goal of this project is to create a system that is viable in low tidal range locations traditionally not considered for locations of tidal energy systems, therefore increasing the overall global tidal energy portfolio. By implementing a closed system of ‘bladders’ and convergent nozzles to optimize the flow rate of the contained fluid, the proposed system can 1) derive tidal energy in low tidal range geographies 5 2) avoid typical hazards like system biofouling, marine life propeller impacts, and 3) allow for ease of installation, operation, and maintenance.

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Allsop, Steven Christopher. "Hydrodynamic modelling for structural analysis of tidal stream turbine blades." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/33219.

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The predictable nature of the tides offers a regular, reliable source of renewable energy that can be harnessed using tidal stream turbines (TSTs). The UK's practically extractable tidal stream energy resource has the potential to supply around 7 % of the country's annual electricity demand. As of 2016, the world's first commercial scale arrays have been deployed around the UK and France. The harsh nature of the marine operating environment poses a number of engineering challenges, where the optimal turbine design solution remains under investigation. In this thesis, a numerical model is developed to assess the power production and hydrodynamic behaviour of horizontal axis tidal turbines. The developed model builds upon well established and computationally efficient Blade Element Momentum Theory (BEMT) method for modern three-bladed wind turbines. The main novel contribution of this thesis is extending the application to an alternative design of a ducted, high solidity and open centre TST. A validation study using measurements from multiple different scale model experimental tank tests has proven the applicability of the model and suitability of the imposed correction factors. The analytical modifications to account for ducted flow were subsequently indirectly verified, where predictions of turbine power and axial thrust forces under optimal operating speeds were within 2 % of those using more advanced computational fluid dynamics (CFD) methods. This thesis presents a commercial application case of two turbines designed by OpenHydro, examining the BEMT performance with a sophisticated blade resolved CFD study. A comparison of results finds that the model is capable of predicting the average peak power to within 12 %, however it under predicts thrust levels by an average of 35 %. This study concludes that the model is applicable to ducted turbine configurations, but is limited in capturing the complex flow interactions towards the open centre, which requires further investigation. The computational efficiency of the newly developed model allowed a structural analysis of the composite blades, thus demonstrating it is suitable to effectively evaluate engineering applications. Stresses are seen to be dominated by flap-wise bending moments, which peak at the mid-length of the blade. This tool will further enable EDF to perform third party assessments of the different turbine designs, to aid decision making for future projects.

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Simon, Peter. "Assessment of Embodied Energy and Carbon Emissions of the Swansea Bay Tidal Lagoon from a Life Cycle Perspective." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-25145.

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In the pursuit of low-carbon, renewable energy sources one option with great potential in the UK is tidal energy. Specifically the proposed construction of the Swansea Bay Tidal Lagoon (SBTL) in South Wales has become one such discussed option. With a potential net annual output of 400 GWh and a 120-year lifetime the scheme represents a long-term and large-scale electricity production option. An assessment of carbon emissions and embodied energy (EE) of the lagoon’s life cycle was carried out. Total lifetime carbon emissions for the SBTL are in the region of 470,000 tCO2e and EE was found to be around 7,800 TJ. The assessment shows that the SBTL has significantly lower emissions per year than the existing National Grid mix and with emissions of around 0.01 kgCO2e/KWh is significantly lower than the UK emissions target of 0.07 kgCO2e/KWh. Energy payback of the SBTL was found to be in the region of 5.5 years. The use of dredged ballast infill sourced from within the area of the lagoon plays an important role in keeping emissions and energy use low; and is a key consideration when planning future tidal lagoon structures.

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Ashglaf, Mohmed Omran. "Development of Hybridization concept for horizontal axis wind / tidal systems using functional similarities and advanced real-time emulation methods." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH07/document.

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La capacité des systèmes conventionnels de production d'énergie éolienne et marémotrice à fournir au réseau une énergie fiable et stable à tout moment est un nouveau défi en raison des fluctuations météorologiques, qui ont un impact significatif et direct sur la production d'énergie. C'est pourquoi l'hybridation des systèmes de production d'énergie éolienne et hydrolienne ont été étudiées pour améliorer l'intégration des énergies éolienne et marémotrice sur le réseau électrique.Cette étude nous a amené à développer des contributions liées à deux axes principaux :Le premier axe est focalisé sur un nouveau concept d'hybridation de deux sources énergétiques différentes en termes de propriétés physiques, l’éolien et l’hydrolienne à axe horizontal, basé sur un couplage électromécanique de ces deux systèmes. Les deux ressources sont l’énergie éolienne et l’énergie des courants marins. Le concept est développé en utilisant les similitudes fonctionnelles des turbines et les similarités en conversion d’énergie de leurs chaînes énergétiques. Pour appliquer ce concept en premier lieu, les paramètres de la génératrice asynchrone à double alimentation installée dans l’émulateur du GREAH sont identifiés. Ensuite, la chaîne de conversion de puissance est modélisée mathématiquement et simulée dans un environnement MATLAB / SIMULINK. Nous avons développé deux stratégies de commande.Une stratégie à vitesse fixe appelé "Contrôle direct de la vitesse", et une stratégie à vitesse variable basée sur la recherche de puissance maximale, dénommée "Contrôle indirecte de vitesse". Enfin, ce concept a été implémenté pratiquement sur l’émulateur en temps réel du laboratoire. Les résultats obtenus ont été analysés et discutés suite à ces travaux.Le deuxième axe est consacré à un concept que l’on appelle «temps accélérée» de simulation ou « temps virtuel ». Par la suite, ce concept a été mis en œuvre sur l’émulateur multi physique disponible au laboratoire GREAH. Ce concept (temps accélérée) est basé sur la réduction des échantillons de profil de vent afin de diminuer le temps de simulation et faciliter la commande en temps réel.Les résultats principaux sont obtenus d’abord dans MATLAB / SIMULINK, puis ont été vérifiés sur l’émulateur en temps réel. L’objectif principal de cette thèse est d’étudier le concept d’hybridation éolienne offshore / éolienne basée sur la flexibilité d’un émulateur multifonctions permettant diverses architectures d’émulation : éoliennes, éoliennes, et systèmes hybrides éoliennes - éoliennes. Nous analysons son impact sur la puissance de sortie du système. Les résultats obtenus sont corrélés aux profils de vitesse du vent et des marées, dans lesquels les propriétés statistiques ayant un impact sur les chaînes énergétiques mondiales pourraient être complémentaires et en particulier en fonction des sites donnés.Contributions principales et perspectives- Développement du concept de couplage électromécanique. Lorsque deux sources d’énergie renouvelables sont « intégrées », on stabilise la fluctuation rapide de la puissance générée, mais sous certaines conditions telles que la présence d’unités de stockage ou d’un système d’embrayage automatique.- Le concept temps accéléréeCette méthode est utilisée pour réduire la taille des données enregistrées du vent ou des courant marins, afin d’accélérer le temps de simulation des unités de production d'énergie avec des résultats raisonnables qui se rapprochent pertinemment des situations réelles.- Etudier et développer le concept de régime d’arbre électrique :Si le couplage électromécanique est difficile à réaliser du point de vue mécanique et que les découplages à arbre unique sont trop fréquents et que les contraintes mécaniques sont élevées, on peut étudier le régime de l'arbre électrique avec deux machines à induction DFIG. Le système peut fonctionner en mode synchrone avec des structures et configurations spécifiques
The ability of conventional wind and tidal generation systems to provide the grid with reliable and stable power at all times is a new challenge due to weather fluctuations, which have a significant and direct impact on energy production. This is why the hybridization of wind and tidal power generation systems has been studied to improve the integration of wind and tidal power into the electricity grid.This study led us to develop contributions related to two main axes:The first axis is focused on a new concept of hybridization of two different energy sources in terms of physical properties, wind and horizontal axis turbines, based on an electromechanical coupling of these two systems. The two resources are wind energy and marine energy. The concept is developed using the functional similarities of turbines and similarities in energy conversion of their energy chains. To apply this concept first, the parameters of the double fed asynchronous generator installed in the GREAH emulator are identified. Then, the power conversion chain is modeled mathematically and simulated in a MATLAB / SIMULINK environment. We have developed two control strategies.A fixed speed strategy called "Direct Speed Control", and a variable speed strategy based on the search for maximum power, called "Indirect Speed Control". Finally, this concept has been implemented practically on the real-time emulator of the laboratory. The results obtained were analyzed and discussed following this work.The second axis is devoted to a concept called "accelerated time" simulation or "virtual time". Subsequently, this concept was implemented on the multi-physics emulator available at the GREAH laboratory. This concept (accelerated time) is based on reducing wind profile samples in order to decrease simulation time and facilitate real-time control.The main results are obtained first in MATLAB / SIMULINK, then verified on the emulator in real time.The main objective of this thesis is to study the concept of offshore wind / tidal turbine hybridization based on the flexibility of a multi-function emulator that allows various emulation architectures: wind turbines, tidal turbines, and hybrid wind - tidal turbines systems. We analyze its impact on the output power of the system; the obtained results are correlated with wind and tidal speed profiles, in which statistical properties impacting global power chains could be complementary and in particular in function of the given sites. Main contributions and perspectives- Development of the concept of electromechanical coupling.When two renewable energy sources are "integrated", the rapid fluctuation of the power generated is stabilized, but under certain conditions such as the presence of storage units or an automatic clutch system.- The accelerated time conceptThis method is used to reduce the size of the recorded wind or sea current data, to speed up the simulation time of the power generation units with reasonable results that are close to actual situations.- Study and develop the concept of electric shaft regime: If the electromechanical coupling is difficult to achieve from the mechanical point of view and the single shaft decouples are too frequent so high mechanical stress, one can study the electric shaft regime with two DFIG induction machines.There is a regime in which the ratios between the speeds of the different machines are rigorously constant. The system can operate in synchronous mode with specific structures and configurations

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LEITE, NETO Pedro Bezerra. "OTIMIZAÇÃO DA GERAÇÃO DE ELETRICIDADE A PARTIR DE FONTE MAREMOTRIZ." Universidade Federal do Maranhão, 2012. http://tedebc.ufma.br:8080/jspui/handle/tede/1869.

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CNPQ, CAPES
The challenges on the world’s energy sector, such as environmental questions and the rising on demand, has been stimulated the use of several kind of energy sources, such as tidal energy. These challenges associated to development of the technologies used in electromechanical devices enable the tidal exploitation attractive under technological and economic aspects. In this work, a methodology to estimating the energetic performance of a tidal power plant on the estuary of Bacanga is presented. Moreover, a dispatch strategy based on Genetic Algorithms was developed to maximize the total energy generated by the plant through an optimal scheduling of the turbines during the generation process. By modeling components and tidal cycle, several generation scenarios were simulated and analyzed considering single-effect and double-effect operation over one year of operation. From results obtained, it can be concluded that, although some constraints to the full exploitation of the potential of the estuary, it is still possible to exploit a significant amount of energy. This is due to improvements in efficiency of electromechanical devices currently available that allow the exploitation of energy in very low heads, as is the case of Bacanga.
Os grandes desafios do setor energético mundial tais como questões ambientais e a crescente demanda por energia, têm estimulado a utilização de diversas fontes alternativas de energia, inclusive as marés. Tais desafios associados ao desenvolvimento das tecnologias utilizadas em dispositivos eletromecânicos tornaram a exploração da energia das marés atrativa sob os aspectos tecnológicos e econômicos. Neste trabalho, é apresentada uma metodologia para a estimação de indicadores energéticos de uma usina maremotriz. Foi desenvolvida uma estratégia de despacho baseada em Algoritmos Genéticos visando-se maximizar a energia total gerada pela usina através do despacho ótimo das turbinas durante o processo de geração. Através da modelagem de componentes e do ciclo de mares, foram simulados e analisados cenários de geração em efeito-simples e efeito-duplo para um ano de operação. Como estudo de caso foi considerado o estuário do Bacanga, localizado na área urbana de São Luís, Maranhão. Dos resultados obtidos pode-se concluir que, embora algumas restrições impeçam o pleno aproveitamento do potencial do estuário, ainda é possível um aproveitamento significativo do mesmo. Isto se deve em grande parte às melhorias, em termos de eficiência, dos equipamentos eletromecânicos disponíveis atualmente, que possibilitam a exploração energética de baixíssimas quedas, como é o caso do Bacanga.

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33

Xin, Bai. "Numerical simulation of a marine current turbine in turbulent flow." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/7900.

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The marine current turbine (MCT) is an exciting proposition for the extraction of renewable tidal and marine current power. However, the numerical prediction of the performance of the MCT is difficult due to its complex geometry, the surrounding turbulent flow and the free surface. The main purpose of this research is to develop a computational tool for the simulation of a MCT in turbulent flow and in this thesis, the author has modified a 3D Large Eddy Simulation (LES) numerical code to simulate a three blade MCT under a variety of operating conditions based on the Immersed Boundary Method (IBM) and the Conservative Level Set Method (CLS). The interaction between the solid structure and surrounding fluid is modelled by the immersed boundary method, which the author modified to handle the complex geometrical conditions. The conservative free surface (CLS) scheme was implemented in the original Cgles code to capture the free surface effect. A series of simulations of turbulent flow in an open channel with different slope conditions were conducted using the modified free surface code. Supercritical flow with Froude number up to 1.94 was simulated and a decrease of the integral constant in the law of the wall has been noticed which matches well with the experimental data. Further simulations of the marine current turbine in turbulent flow have been carried out for different operating conditions and good match with experimental data was observed for all flow conditions. The effect of waves on the performance of the turbine was also investigated and it has been noticed that this existence will increase the power performance of the turbine due to the increase of free stream velocity.

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Déporte, Astrid. "Caractérisation du fonctionnement d'une hydrolienne à membrane ondulante pour la récupération de l'énergie des courants marins." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0031/document.

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Cette thèse présente les trois approches : analytique, expérimentale et numérique développées pour étudier le comportement d'une hydrolienne à membrane ondulante. Cette technologie, portée par l'entreprise EEL Energy, est basée sur les déformations périodiques d'une structure flexible pré-contrainte. Des convertisseurs d'énergie, positionnés de part et d'autre du système, sont actionnés par le mouvement d'ondulation.Analytiquement, la membrane est représentée par un modèle linéaire de poutre à une dimension et l'écoulement par un fluide potentiel 3D. L'action du fluide sur la membrane est évaluée par la théorie des corps élancés. L'énergie est dissipée de façon continue sur la longueur de la membrane. Expérimentalement, un prototype à l'échelle 1/20ième a été développé, des micro-vérins permettent de simuler l'énergie produite. Les essais avec le prototype1/20ième ont permis de valider le concept d'hydrolienne à membrane ondulante et le mode de récupération d'énergie. Un modèle numérique 2D éléments finis a été mis au point. Chaque élément constitutif de la membrane y est reproduit, la dissipation d'énergie est réalisée par des éléments dissipatifs mais la loi d'amortissement est limitée à un amortissement linéaire en vitesse.La comparaison des résultats issus de ces trois modèles a permis de valider leur bonne capacité à reproduire le comportement de la membrane sans conversion d'énergie. La dissipation d'énergie appliquée avec le modèle analytique se distingue clairement des deux autres modèles de part sa localisation mais aussi par la loi d'amortissement utilisée. Les autres modèles sont cohérents entre eux et si on ne parvient pas à corréler les résultats de puissance dissipée, le comportement du système et la répartition de la puissance dissipée le long de la membrane sont semblables. Ces trois approches ont permis de mettre en avant les paramètres clés dont dépend le comportement de la membrane et l'étude paramétrique démontre la complémentarité et l'intérêt du développement conjoint des modèles dans un souci industriel d'optimisation du système. Le développement d'un prototype à l'échelle supérieure (1/6ème), devant faire le lien entre les essais en bassin et les essais en mer, a permis de travailler sur les effets d'échelle. Des différences de comportements sont observées entre ces deux prototypes mais elles sont dues en partie à des différences de conditions aux limites et en partie à des effets de confinements très importants. Pour évaluer la tenue sur le long terme du prototype, ses composants (composite, élastomère) ont été caractérisés précisément et des essais de vieillissement accéléré par température ainsi que des essais de fatigue ont été mis en place sur des échantillons de matière
This manuscript presents three approaches : analytical, experimental and numerical, to study the behavior of a flexible membrane tidal energy convertor. This technology, developed by the EEL Energy company, is based on periodic deformations of a pre-stressed flexible structure. Energy convertors, located on each side of the device, are set into motion by the wave-like motion.In the analytical model, the membrane is represented by a linear beam model at one dimension and the flow by a 3 dimensions potential fluid. The fluid forces are evaluated by the elongated body theory. Energy is dissipated all over the length of the membrane. A 20th scale experimental prototype has been designed with micro-dampers to simulate the power take-off. Trials have allowed to validate the undulating membrane energy convertor concept. A numerical model has been developed. Each element of the device is represented and the energy dissipation is done by dampers element with a damping law linear to damper velocity.Comparison of the three approaches validates their ability to represent the membrane behavior without damping. The energy dissipation applied with the analytical model is clearly different from the two other models because of the location (where the energy is dissipated) and damping law. The two others show a similar behavior and the same order of power take off repartition but value of power take off are underestimated by the numerical model. These three approaches have allowed to put forward key-parameters on which depend the behavior of the membrane and the parametric study highlights the complementarity and the advantage of developing three approaches in parallel to answer industrial optimization problems.To make the link between trials in flume tank and sea trials, a 1/6th prototype has been built. To do so, the change of scale was studied. The behavior of both prototypes is compared and differences could be explained by differences of boundary conditions and confinement effects. To evaluated membrane long-term behavior at sea, a method of aging accelerated by temperature and fatigue tests have been carried out on prototype materials samples immerged in sea water

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Paillard, Benoît. "Simulation numérique et optimisation d'une hydrolienne à axe transverse avec contrôle actif de l'angle de calage." Brest, 2011. http://www.theses.fr/2011BRES2069.

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Cette thèse s’inscrit dans le contexte de la simulation d’efforts et d’écoulement dynamiques autour d’un profil en mouvement complexe dans un écoulement uniforme : la combinaison d’une rotation autour d’un axe distant et d’un tangage classique autour du quart de corde. Elle vise à mettre en place des méthodes de simulation simples de dimensionnement et de prédiction de performance d’une turbine Darrieus à contrôle actif de pas ; elle vise également à proposer une méthode de calcul permettant la simulation de l’écoulement et l’optimisation de ce type de turbine dont les pales ont leur calage qui varie cycliquement. Elle trouve son application dans l’étude et le développement des énergies marines renouvelables, et plus particulièrement des machine d’extraction d’énergie cinétique de courants de marée ou fluvial à axe transverse. L’objectif est de construire des outils de simulation permettant une étude approfondie des possibilités des systèmes à axe transverse avec variation cyclique active de pas. Pour répondre à cela deux stratégies de modélisation ont été suivies. D’une part l’adaptation du pas variable à une méthode énergétique couplée à différents modèles de prédiction des efforts instationnaires sur un profil; et d’autre part une simulation URANS avec maillage tournant/déformant pour prendre en compte cette variation de pas. La variation d’angle de calage a permis d’obtenir me augmentation de performance maximal de 52%. L’essai des différents modèles fluides disponibles a mis en évidence l’efficacité du modèle turbulent. Le modèle de transition, pourtant prometteur et semblant plus adapté aux cas d’application considérés, s’est révélé peu performant, mais aucune investigation supplémentaire n’a été effectuée. La comparaison avec l’expérience dans le cas turbulent avec modèle de turbulence kw - SST s’est révélée encourageante, notamment pour les rapports de vitesse périphériques opérationnels, autour de ʎ = 5. Pour les ʎ plus faibles les résultats sont en moyenne similaires mais le modèle peine à reproduire les variations aux fréquences naturelles du décrochage, dues aux lâchers tourbillonnaires. La continuité de cette étude réside d’une part dans l’étude d’autres lois de calage, et d’autre part dans l’application à un système concret pour pouvoir aboutir à des systèmes transverses plus efficace
This work describes the numerical simulation of an acti4e variable pitch Darrieus turbine with two methods, one of which is derived from momentum theory and ONERA-EDLIN unsteady model, and the other is 0Ff). Though almost no Darrieus turbine produced electrical power from wind since early 90s, a renewed interest arose from the development of water turbines because most drawbacks which prevented this system from becoming a major wind turbine system do not exist in water. For this reason many publications tackling various issues in water crossflow turbines were written in the past few years. Dynamic and static stall characteristics of an airfoil have a very strong influence on the turbine performance. Considering how the vortex method could not predict it accurately, and the complexity of a CFD simulation in an optimisation process, the ONERA-EDLIN model is a very interesting compromise. On top of that, it has the ability to model any special kinematics and not just only pitch; it can predict installed dynamic behavior based on a potential formulation; and it can calculate dynamic stall for the moments, which is interesting in the case of variable pitch. An URANS method was then used, using the solver ANSYS-CFX. The spatial and temporal discretization have been studied to be used in future simulations. Blades’ motion was obtained through mesh deformation for pitch modification, and the main rotation was implemented through global rotation of a circular mesh domain, with general grid interface model at its boundaries. The following turbulence models were used laminar, kw - SST. And Langtry Menter transition model. Five experimental cases were used to assess models’ performance. Comparison was best for kw - SST. The two others predicted early stalls, especially the laminar model. Further simulations, for other conditions and pitch function are needed and are currently being carried out. Agreement with experimental data was found to be fairly good, event though discrepancies exist in some specific cases. Agreement level could not be related to a particular operational condition. Variable pitch was implemented for a tip speed ratio of 5, aiming at performance improvement primarily. Sinusoidal functions of different orders were tested. One of them obtained a performance increase of 52%. For this regime optimal pitch variation seems to require a very slight recirculation and an incidence decrease on upwind section, and an incidence increase on downwind section. The flow deceleration through turbine was found to be a primary factor in function performance evaluation. Finally torque required to set blades into motion around their quarter chord was compared with power coefficient. Its influence was found to be close to 0, or even positive

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Gaurier, Benoît. "Etude expérimentale des performances d'une hydrolienne, soumise aux effets de la turbulence et de l'intéraction houle-courant." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMLH11.

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Dans le contexte actuel du réchauffement climatique, l’extraction de l’énergie des courants marins par des hydroliennes se doit d’intégrer le mix énergétique de demain. Ces machines étant confrontées à un environnement marin difficile, il est nécessaire de connaître leur comportement dans des conditions de fonctionnement réaliste pour garantir une utilisation optimale. Dans ces travaux, les performances d’une hydrolienne sont étudiées, quand la machine est soumise à un courant turbulent ou aux effets combinés de la houle et du courant. La représentation physique des essais à échelle réduite est d’abord abordée, en se focalisant sur la caractérisation de l’écoulement incident et ses effets sur une maquette d’hydrolienne à l’échelle 1/20. La position et le type de mesure de la vitesse amont sont discutés afin de définir avec précision ses performances et sa réponse temporelle et spectrale. Ces éléments sont essentiels dans la définition des standards de certification des modélisations expérimentales. La représentation de variations bathymétriques permet de générer des écoulements turbulents, caractérisés par le passage de structures tourbillonnaires de la taille du rotor. La réponse de la machine est déterminée de manière globale et locale, pour plusieurs positions relatives de la machine par rapport aux obstacles. Les effets combinés de la houle et du courant sur le comportement de la machine sont étudiés à partir de résultats de mesures obtenues dans trois infrastructures d’essais. Des différences significatives entre les bassins apparaissent et une discussion sur leur origine est menée
In the context of global warming, the extraction of energy by tidal turbines from marine currents must be integrated into the future energetic mix. Being confronted with a difficult marine environment, it is required to know the turbines’ behaviour when they are submitted to realistic solicitations to guarantee an optimal use. In this work, the marine turbine performance is studied when the machine is submitted to a turbulent current or a combined wave-current effect. The physical representation of trials at reduced scale is first described focusing on the incoming flow characterisation and its effects on a turbine model at 1:20 scale. The locationand measurement type of the upstream velocity are discussed to accurately define its performance and its temporal and spectral response. Such parameters are essential in the definition of certification standards for experimental modelling. The bathymetric variation representation enables turbulent flow to be generated. They are mainly characterized by large eddies with a size corresponding to the rotor. The turbine response is determined in a global and local way for many relative turbine locations versus the obstacles. The combined wave and current effects on the turbine behaviour are studied from measurement results carried out in three facilities. Significant differences between the tanks appear and a discussion on their origin is proposed

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Fakhri, Eyman. "Contribution à l'optimisation de l'architecture de parcs d'hydroliennes." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC224.

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Pour faire face au réchauffement climatique, une transition énergétique de grande ampleur est impérative. Pour les pays disposant de vastes zones maritimes, comme la France, les Energies Marines Renouvelables (EMRs) peuvent constituer une part significative d’énergie à bas carbone. Les EMRs peuvent être produites à partir de la houle, du vent, des gradients de salinité… Dans cette thèse, nous nous focalisons sur l’énergie des courants de marée et leur exploitation par les hydroliennes. Cette technologie est aujourd’hui en phase pré-industrielle.Dans ce travail de thèse, un outil d’aide à la décision destiné à l’optimisation de l’architecture des parcs d’hydroliennes est développé. Cet outil nommé OPTIFARM tient compte de l’hydrodynamique du site, des coûts d’investissement et des opérations de maintenance, des pertes d’énergie de production dues aux effets de sillage ainsi que des pertes d’énergies dans le réseau électrique. L’outil permet de déterminer de manière optimale le nombre et les positions des hydroliennes et des sous-stations électriques offshores ainsi que la topologie de raccordement électrique en AC. OPTIFARM est basé sur un algorithme génétique et un algorithme d’optimisation par essaim particulaire. La méthode d'optimisation développée est appliquée à deux sites hydroliens français : le Raz-Blanchard (situé entre l'île d'Aurigny et le Cap de la Hague) et le passage du Fromveur (situé en mer d'Iroise) qui représentent respectivement le premier et le deuxième plus grand gisement hydrolien en France. Les résultats montrent que le coût de production de l'énergie diffère considérablement d'un site à l'autre et qu'il dépend fortement de la taille du parc
Renewable Energies (MREs) can contribute significantly to the energy mix. MREs can be produced from different sources, among them tidal energy – the focus of this work – has aroused major interest from industrialists and decision-makers.In this thesis, a decision support tool for the optimization of the architecture of tidal farms is developed. The optimization tool, named OPTIFARM, takes into account the hydrodynamics of the site, the investment and maintenance costs, the loss of production caused by the wake effect and the energy loss in the electrical network. The tool allows determining the optimal number and positions of tidal turbines and offshore substations in the farm as well as the optimal AC electrical connection topology of the tidal farm network. The optimization tool relies on a genetic and a particle swarm optimization algorithms. OPTIFARM is applied to two French tidal energy sites: the Alderney Race located between the Alderney Island and Cap de la Hague, and the Fromveur Strait located in the sea of Iroise. Those sites represent respectively the first and the second greatest tidal potential in France. The results show that the energy production cost considerably differs from one site to another and it strongly depends on the size of the farm

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Lafleur, Charlotte. "Methods for assessing the economic viability of stand-alone hybrid renewable energy systems." Thesis, 2019. http://hdl.handle.net/1828/11099.

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The addition of renewable energy in a previously diesel-powered off-grid micro-grid results in what is known in the field as a Stand-Alone Hybrid Renewable Energy System (HRES). Such initiative is a near-term target of both federal and provincial governments in Canada. Not only does it reduce environmental hazards like leaks, spills and air pollution, but the combination of renewable energy and fossil fuel generators can increase stability and lower the cost of electricity. It is deemed a crucial step towards a clean energy future, but also a necessity in the reconciliation process with Indigenous Peoples of Canada - many of who inhabit off-grid communities. The addition of renewable energy can greatly increase the independence of a community by reducing reliability on external diesel suppliers and creating job opportunities. To be successful, HRES need to be carefully planned; the variable and uncertain behaviour of natural resources add a level of complexity to the preliminary design stage. Energy systems are therefore simulated and optimized to estimate the lifecycle cost by determining the nature and capacity of their components and their operational strategy. Chapter 2 goes over the preliminary design stage of two HRES in British Columbian communities. Many modelling tools are available, ranging from full-factorial and linear optimization techniques that can solve single-objective problems, to meta-heuristic algorithms. One of the distinctions between different HRES modelling tools is the foresight horizon being used. Linear programming tools commonly have a perfect foresight over the typical year analysed, for both demand and natural resources. This can lead to an overly optimistic prediction of the lifecycle cost of a system when the reality of implementations comes with uncertainties. On the other hand, tools that use myopic foresight, or no knowledge of future parameters, can lead to pessimistic lifecycle cost estimates since the demand and power output of certain renewable energy technologies, like solar panels, can be known within a few hours. The purpose of Chapter 3 of this thesis is to guide readers towards the right tool in the context of energy system modelling for the preliminary design of HRES. It was found that the degree of importance of choosing the appropriate foresight approach is a function of renewable energy penetration, autocorrelation, and storage capacity. A system with a high renewable energy share, a low short-term (few hours) autocorrelation, and an optimal storage size will result in the highest NPC difference between the two methods. When planning for long-term HRES design, the choice of the foresight horizon can either be representative of a lower/upper cost boundary (perfect and myopic foresight respectively) or of the real-time predictability of the power output of the chosen renewable energy power source. The use of energy system modelling tools is often reserved for highly qualified personnel and is therefore costly for prospective communities. To improve community readiness with minimal investment, a simple alternative to energy system modelling is proposed in Chapter 4 for the integration of tidal stream turbines in British Columbia. A series of three logical conditions was demonstrated to inform on the viability of a project in terms of cost reduction in comparison to the business as usual scenario. These conditions were found to also be useful for determining the minimum scale, or the economic break-in scale, for a tidal stream turbine given a remote community. In this context, communities are found to be best described by the local price of diesel fuel as an easily accessible metric to represent the current cost of electricity, their electrical load scale, and the local tidal current resource. Ten British Columbian communities were selected to validate the results by comparing the set of conditions to a complete energy system modelling approach and four were found to reach savings of 10 % or more as compared to the business as usual scenario. The long-term objective of this work is to provide remote communities with an integrated, affordable, and turnkey solution for the displacement of diesel in their energy systems. The next steps in achieving this include augmented optimization tools to quantify and capture non-monetary value so that the modelling and multi-criteria decision-making steps of the design process can be bridged together.
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Javidsharifi, M., T. Niknam, J. Aghaei, and Geev Mokryani. "Multi-objective short-term scheduling of a renewable-based microgrid in the presence of tidal resources and storage devices." 2017. http://hdl.handle.net/10454/15243.

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Yes
Daily increasing use of tidal power generation proves its outstanding features as a renewable source. Due to environmental concerns, tidal current energy which has no greenhouse emission attracted researchers’ attention in the last decade. Additionally, the significant potential of tidal technologies to economically benefit the utility in long-term periods is substantial. Tidal energy can be highly forecasted based on short-time given data and hence it will be a reliable renewable resource which can be fitted into power systems. In this paper, investigations of effects of a practical stream tidal turbine in Lake Saroma in the eastern area of Hokkaido, Japan, allocated in a real microgrid (MG), is considered in order to solve an environmental/economic bi-objective optimization problem. For this purpose, an intelligent evolutionary multi-objective modified bird mating optimizer (MMOBMO) algorithm is proposed. Additionally, a detailed economic model of storage devices is considered in the problem. Results show the efficiency of the suggested algorithm in satisfying economic/environmental objectives. The effectiveness of the proposed approach is validated by making comparison with original BMO and PSO on a practical MG.
Iran National Science Foundation; Royal Academy of Engineering Distinguished Visiting Fellowship under Grant DVF1617\6\45

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Blanchfield, Justin. "The extractable power from tidal streams, including a case study for Haida Gwaii." Thesis, 2007. http://hdl.handle.net/1828/302.

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Interest is growing worldwide among utility companies and governments of maritime countries in assessing the power potential of tidal streams. While the latest assessment for Canadian coastlines estimates a resource of approximately 42 GW, these results are based on the average kinetic energy flux through the channel. It has been shown, however, that this method cannot be used to obtain the maximum extractable power for electricity generation. This work presents an updated theory for the extractable power from a channel linking a bay to the open ocean. A mathematical model is developed for one-dimensional, non-steady flow through a channel of varying cross-section. Flow acceleration, bottom drag, and exit separation effects are included in the momentum balance. The model is applied to Masset Sound and Masset Inlet in Haida Gwaii, a remote island region, to determine the extractable power and its associated impacts to the tidal amplitude and volume flow rate through the channel.

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Menéndez, Arán David Hernán. "Hydrodynamic optimization and design of marine current turbines and propellers." 2013. http://hdl.handle.net/2152/21497.

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This thesis addresses the optimization and design of turbine and propeller blades through the use of a lifting line model. An existing turbine optimization methodology has been modified to include viscous terms, non-linear terms, and a hub model. The method is also adapted to the optimization of propellers. Two types of trailing wake geometries are considered: one based on helical wakes which are aligned at the blade (using the so-called "moderately loaded propeller'' assumption), and a second one based on a full wake alignment model in order to represent more accurately the wake geometry and its effect on the efficiency of the rotor. A comparison of the efficiencies and the loading distributions obtained through the present methods is presented, as well as convergence and numerical accuracy studies, and comparisons with existing analytical results. In the case of turbines, various types of constraints are imposed in the optimization method in order to avoid abrupt changes in the designed blade shape. The effect of the constraints on the efficiency of the turbines is studied. Once the optimum loading has been determined, the blade geometry is generated for given chord, thickness and camber distributions. Finally, a low-order potential-based boundary element method and a vortex-lattice method are used to verify the efficiency of the designed turbines.
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Boronowski, Susan M. "Integration of wave and tidal power into the Haida Gwaii electrical grid." Thesis, 2009. http://hdl.handle.net/1828/1704.

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Rising energy demand, fossil fuel costs, and greenhouse gas emissions have led to a growing interest in renewable energy integration. Remote communities, often accompanied by high energy costs and abundant renewable energy resources, are ideal cases for renewable energy integration. The Queen Charlotte Islands, also known as Haida Gwaii, are a remote archipelago off the northwest coast of British Columbia, Canada that relies heavily on diesel fuel for energy generation. An investigation is done into the potential for electricity generation using both tidal stream and wave energy in Haida Gwaii. A mixed integer optimization network model is developed in a Matlab and GAMS software environment, subject to set of system constraints including minimum operational levels and transmission capacities. The unit commitment and economic dispatch decisions are dynamically solved for four periods of 336 hours, representing the four annual seasons. Optimization results are used to develop an operational strategy simulation model, indicative of realistic operator behaviour. Results from both models find that the tidal stream energy resource in Haida Gwaii has a larger potential to reduce energy costs than wave energy; however, tidal steam energy is more difficult to integrate from a system operation point of view and, in the absence of storage, would only be practical at power penetration levels less than 20%.

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Richardson, Riley L. "Developing a holistic framework to investigate the environmental, social, and economic suitability of tidal stream energy in British Columbia’s remote coastal diesel reliant First Nations Communities." Thesis, 2020. http://hdl.handle.net/1828/12529.

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This thesis holistically examines the potential for tidal stream turbine (TST) integration to displace diesel generated electricity in remote coastal First Nations communities within the Marine Plan Partnership for the North Pacific Coast region of British Columbia. This thesis utilizes a combination of spatial analysis (GIS Multi-Criteria Decision Analysis) to identify sites; stakeholder engagement to assess TST suitability, bridge knowledge gaps, and understand desired characteristics of community energy systems; and Levelized Cost of Energy (LCOE) analyses for existing diesel and externality included scenarios along with potential TST costs in a candidate community. Results illustrate the need for information within these communities, from resource quantification to characteristics of renewable energy technologies and system feasibility; self-sufficiency as being the primary transition driver; and funding/human resource capacity as being substantial barriers. Within the study region ≈89.8 km2 of feasible resource was identified, with ≈22 km2 of potentially suitable tidal resource in proximity to nine communities. The COVID-19 pandemic resulted in difficulties contacting and arranging interviews with the most suitable communities. Driven by the holistic research mandate requiring community stakeholder engagement to occur in tandem with the economic analyses, Queen Charlotte Village and Skidegate Landing on Haida Gwaii were chosen as the candidate communities, despite not being the most suitable identified communities. The community interviews revealed TSTs as being an acceptable renewable energy technology. Furthermore, the identified site in Skidegate Inlet (SI) was found to have favourable Marine Spatial Planning (MSP) for TST development. Existing diesel generation carries a LCOE of $0.63/kWh, being $0.08-0.14 more per kWh than the literature cited LCOE range for TSTs. The LCOE for CO2 equivalent externalities at current carbon tax prices was found to be an additional $0.02/kWh. Despite having a technically viable peak spring current speed, the SI site was financially unviable for 284 kW of rated capacity across all diesel LCOE scenarios driven by capacity factor (1.62%), high cabling costs (approximately one third of capital costs), and outdated data/assumptions within the Natural Resources Canada Tidal Project Cost Estimation tool used in the tidal LCOE calculations. This work contributes to the progression of tidal energy development on BCs coast along with demonstrating the utility of holistic assessment frameworks for RETs across environmental, social, and economic considerations. The results of this thesis can inform existing MSP efforts in the Marine Plan Partnership for the North Pacific region and the framework developed can be built upon and altered for global use in pursuit of sustainable energy transitions.
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Carpman, Nicole. "Resource characterization and variability studies for marine current power." Doctoral thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-319033.

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Producing electricity from marine renewable resources is a research area that develops continuously. The field of tidal energy is on the edge to progress from the prototype stage to the commercial stage. However, tidal resource characterization, and the effect of tidal turbines on the flow, is still an ongoing research area in which this thesis aims to contribute. In this thesis, measurements of flow velocities have been performed at three kinds of sites. Firstly, a tidal site has been investigated for its resource potential in a fjord in Norway. Measurements have been performed with an acoustic Doppler current profiler to map the spatial and temporal characteristics of the flow. Results show that currents are in the order of 2 m/s in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus has potential for in-stream energy conversion. Secondly, a river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydro power plant, making the site suitable for experiments on the performance of the vertical axis turbine in a natural environment. The turbine was run in steady discharge flows and measurements were performed to characterize the extent of the wake. Lastly, at an ocean current site, the effect that transiting ferries may have on submerged devices was investigated. Measurements were conducted with two sonar systems to obtain an underwater view of the wake caused by a propeller and a water jet thruster respectively. Furthermore, the variability of the intermittent renewable sources wind, solar, wave and tidal energy was investigated for the Nordic countries. All of the sources have distinctly different variability features, which is advantageous when combining power generated from them and introducing it on the electricity grid. Tidal variability is mainly due to four aspects: the tidal regime, the tidal cycle, local bathymetry causing turbulence, asymmetries etc. and weather effects. Models of power output from the four sources was set up and combined in different energy mixes for a “highly renewable” and a “fully renewable” scenario. By separating the resulting power time series into different frequency bands (long-, mid-, mid/short-, and short-term components) it was possible to minimize the variability on different time scales. It was concluded that a wise combination of intermittent renewable sources may lower the variability on short and long time scales, but increase the variability on mid and mid/short time scales. The tidal power variability in Norway was then investigated separately. The predictability of tidal currents has great advantages when planning electricity availability from tidal farms. However, the continuously varying tide from maximum power output to minimum output several times per day increases the demand for backup power or storage. The phase shift between tidal sites introduces a smoothing effect on hourly basis but the tidal cycle, with spring and neap tide simultaneously in large areas, will inevitably affect the power availability.

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Mullan, Sean. "Tidal sedimentology and geomorphology in the central Salish Sea straits, British Columbia and Washington State." Thesis, 2017. https://dspace.library.uvic.ca//handle/1828/8943.

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Intra-archipelago waterways, including tidal strait networks, present a complex set of barriers to, and conduits for sediment transport between marine basins. Tidal straits may also be the least well understood tide-dominated sedimentary environment. To address these issues, currents, sediment transport pathways, and seabed sedimentology & geomorphology were studied in the central Salish Sea (Gulf and San Juan Islands region) of British Columbia, Canada and Washington State, USA. A variety of data types were integrated: 3D & 2D tidal models, multibeam bathymetry & backscatter, seabed video, grab samples, cores and seismic reflection. This dissertation included the first regional sediment transport modelling study of the central Salish Sea. Lagrangian particle dispersal simulations were driven by 2D tidal hydrodynamics (~59-days). It was found that flood-tide dominance through narrow intra-archipelago connecting straits resulted in the transfer of sediment into the inland Strait of Georgia, an apparent sediment sink. The formative/maintenance processes at a variety of seabed landforms, including a banner bank with giant dunes, were explained with modelled tides and sediment transport. Deglacial history and modern lateral sedimentological and morphological transitions were also considered. Based on this modern environment, adjustments to the tidal strait facies model were identified. In addition, erosion and deposition patterns across the banner bank (dune complex) were monitored with 8-repeat multibeam sonar surveys (~10 years). With these data, spatially variable bathymetric change detection techniques were explored: A) a cell-by-cell probabilistic depth uncertainty-based threshold (t-test); and B) coherent clusters of change pixels identified with the local Moran's Ii spatial autocorrelation statistic. Uncertainty about volumetric change is a considerable challenge in seabed change research, compared to terrestrial studies. Consideration of volumetric change confidence intervals tempers interpretations and communicates metadata. Techniques A & B may both be used to restrict volumetric change calculations in area, to exclude low relative bathymetric change signal areas.
Graduate
2018-12-07

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Dissertations / Theses on the topic 'Tidal renewable energy'

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