Numerical modelling of hydrodynamics and tidal energy extraction in the Alderney Race: a review

Thiebot, Jérôme; Coles, Daniel; Bennis, Anne-Claire; Guillou, Nicolas; Neill, Simon P.; Guillou, Sylvain; Piggott, Matthew D.

doi:10.1098/rsta.2019.0498

Cited by 17 publications

(12 citation statements)

References 58 publications

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“…With current magnitude exceeding 5 m/s and depth suitable to deploy tidal turbines, this 15 km wide strait is one the most promising sites for tidal stream energy exploitation in the world [2]. Numerous investigations have therefore been performed to assess the potential annual energy production of the site, with the most optimistic estimates exceeding 10 TWh/year [16][17][18].…”

Section: Site Description-scenarios Of Tidal Stream Energy Extractionmentioning

confidence: 99%

The Efficiency of a Fence of Tidal Turbines in the Alderney Race: Comparison between Analytical and Numerical Models

et al. 2021

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Assessing the efficiency of a tidal turbine array is necessary for adequate device positioning and the reliable evaluation of annual energy production. Array efficiency depends on hydrodynamic characteristics, operating conditions, and blockage effects, and is commonly evaluated by relying on analytical models or more complex numerical simulations. By applying the conservations of mass, momentum, and energy in an idealized flow field, analytical models derive formulations of turbines’ thrust and power as a function of the induction factor (change in the current velocity induced by turbines). This simplified approach also gives a preliminary characterization of the influence of blockage on array efficiency. Numerical models with turbines represented as actuator disks also enable the assessment of the efficiency of a tidal array. We compare here these two approaches, considering the numerical model as a reference as it includes more physics than the analytical models. The actuator disk approach is applied to the three-dimensional model Telemac3D in realistic flow conditions and for different operating scenarios. Reference results are compared to those obtained from three analytical models that permit the investigation of the flow within tidal farm integrating or excluding processes such as the deformation of the free surface or the effects of global blockage. The comparison is applied to the deployment of a fence of turbines in the Alderney Race (macro-tidal conditions of the English Channel, northwest European shelf). Efficiency estimates are found to vary significantly from one model to another. The main result is that analytical models predict lower efficiency as they fail to approach realistically the flow structure in the vicinity of turbines, especially because they neglect the three-dimensional effects and turbulent mixing. This finding implies that the tidal energy yield potential could be larger than previously estimated (with analytical models).

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Section: Site Description-scenarios Of Tidal Stream Energy Extractionmentioning

confidence: 99%

The Efficiency of a Fence of Tidal Turbines in the Alderney Race: Comparison between Analytical and Numerical Models

et al. 2021

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“…Tidal turbines are represented in MIKE21/3 as a sub-grid object with their influence on the hydrodynamics based on actuator disc theory. The turbines are modelled as a momentum sink terms which are related to the thrust exerted by the turbine, method commonly applied for the study of tidal farm energy extraction [28,29,30,31,32,33]. For each mesh layer the influence of turbines is modelled by calculating the current induced drag and lift force on each layer [25].…”

Section: General Descriptionmentioning

confidence: 99%

Variability of sediment processes around a tidal farm in a theoretical channel

et al. 2021

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Sediment transport plays a crucial role in coastal ecosystems and is one of the least known parameters in high energy sites. The recent development of tidal energy projects challenges the scientific community to better understand this natural phenomenon and the interactions with tidal turbines. Using MIKE21/3 software from DHI, a benchmark for sediment transport model was developed with simulations with and without a tidal farm in idealised two and three-dimensional tidal channels. Results reveal that a 2D approach is sufficient for regional scale morphological assessments, however 3D models allow for a closer examination of influences around the tidal farm. Differences in calculating sediment transport rates based on approaches after Engelund & Fredsøe and Van Rijn formulae illustrate the degree of uncertainty in modelling sediment transport rates. Results for the Engelund & Fredsøe models also show that they are sensitive to mesh resolution in equilibrium conditions and are more stable in non-equilibrium conditions for the bed level change rates. Tests have also demonstrated that models using Engelund & Fredsøe formulae are more sensitive to physical characteristics than models based on Van Rijn, accentuating the necessity to evaluate sediment transport formulae with field data before making a choice of model.

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“…Among different types of marine renewable energies, tidal energy, due to its high level of consistency and predictability, is one of the most feasible and promising sources of energy for future development and investment [1]. Moreover, it has limited visual impact, which eases its social acceptance [2]. Tidal energy resources can be exploited using the kinetic energy of moving water (i.e., tidal stream energy) and the potential energy of the difference in water levels (i.e., tidal potential energy).…”

Section: Introductionmentioning

confidence: 99%

A Numerical Methodology to Predict the Maximum Power Output of Tidal Stream Arrays

et al. 2022

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Due to its high level of consistency and predictability, tidal stream energy is a feasible and promising type of renewable energy for future development and investment. Numerical modeling of tidal farms is a challenging task. Many studies have shown the applicability of the Blade Element Momentum (BEM) method for modeling the interaction of turbines in tidal arrays. Apart from its well-known capabilities, there is a scarcity of research using BEM to model tidal stream energy farms. Therefore, the main aim of this numerical study is to simulate a full-scale array in a real geographical position. A fundamental linear relationship to estimate the power capture of full-scale turbines using available kinetic energy flux is being explored. For this purpose, a real site for developing a tidal farm on the southern coasts of Iran is selected. Then, a numerical methodology is validated and calibrated for the established farm by analyzing an array of turbines. A linear equation is proposed to calculate the tidal power of marine hydrokinetic turbines. The results indicate that the difference between the predicted value and the actual power does not exceed 6%.

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Numerical modelling of hydrodynamics and tidal energy extraction in the Alderney Race: a review

Cited by 17 publications

References 58 publications

The Efficiency of a Fence of Tidal Turbines in the Alderney Race: Comparison between Analytical and Numerical Models

The Efficiency of a Fence of Tidal Turbines in the Alderney Race: Comparison between Analytical and Numerical Models

Variability of sediment processes around a tidal farm in a theoretical channel

A Numerical Methodology to Predict the Maximum Power Output of Tidal Stream Arrays

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