Three-dimensional modelling of turbine wake interactions at a tidal stream energy site

A system of two coupled four-beam acoustic Doppler current profilers was used to collect turbulence measurements over a 36-h period at a highly energetic tidal energy site in Alderney Race. This system enables the evaluation of the six components of the Reynolds stress tensor throughout a large proportion of the water column. The present study provides mean vertical profiles of the velocity, the turbulence intensity and the integral lengthscale along the streamwise, spanwise and vertical direction of the tidal current. Based on our results and considering a tidal-stream energy convertor (TEC) aligned with the current main direction, the main elements of turbulence prone to affect the structure (material fatigue) and to alter power generation would likely be: (i) the streamwise turbulence intensity ( I x ), (ii) the shear stress, v ′ w ′ ¯ , (iii) the normal stress, u ′ 2 ¯ and (iv) the vertical integral lengthscale ( L z ). The streamwise turbulence intensity, ( I x ), was found to be higher than that estimated at other tidal energy sites across the world for similar height above bottom. Along the vertical direction, the length ( L z ) of the large-scale turbulence eddies was found to be equivalent to the rotor diameter of the TEC Sabella D10. It is considered that the turbulence metrics presented in this paper will be valuable for TECs designers, helping them optimize their designs as well as improve loading prediction through the lifetime of the machines. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

Download Full-text

The Tidal Stream Energy Resource of the Fromveur Strait—A Review

Journal of Marine Science and Engineering ◽

10.3390/jmse8121037 ◽

2020 ◽

Vol 8 (12) ◽

pp. 1037

Author(s):

Nicolas Guillou ◽

Jean-Frédéric Charpentier ◽

Mohamed Benbouzid

Keyword(s):

Energy Resource ◽

Tidal Energy ◽

Energy Output ◽

Wake Interactions ◽

Tidal Stream ◽

Technical Specifications ◽

Tidal Stream Energy ◽

Key Steps ◽

A Site

Refined assessments of the available tidal stream energy resource are required to optimize turbines design and guarantee successful implementations and operations of devices in the marine environment. Investigations primary focused on identifying areas with maximum current speeds. However, further information may be reached by exhibiting (i) resource temporal variability, (ii) superimposed effects of meteo-oceanographic conditions (including especially wind-generated surface-gravity waves), and (iii) potential environmental impacts of operating turbines at the regional (e.g., changes in sediment transport and surrounding seabed features, effects on marine water quality, etc.) and local (wake-wake interactions and energy output) scales. These aspects are here investigated by reviewing a series of research studies dedicated to the Fromveur Strait off western Brittany, a region with strong potential for tidal array development along the coast of France. Particular attention is dedicated to the exploitation of combined in-situ and remote-sensing observations and numerical simulations. Beyond a site specific characterization of the tidal stream energy resource, this review promotes a series of original approaches and analysis methods for turbines optimization, thus complementing technical specifications to secure the key steps of a tidal energy project and promote the growth of a reliable tidal stream energy exploitation.

Download Full-text

Investigation of Three Dimensional Tidal Stream Energy in Surrounding Water Areas of ZTD, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.774-776.262 ◽

2013 ◽

Vol 774-776 ◽

pp. 262-266

Author(s):

Bing Chen Liang ◽

Tao Tao Zhang ◽

Hong Da Shi

Keyword(s):

Numerical Modeling ◽

Energy Density ◽

Tidal Current ◽

Current Model ◽

Three Dimensional ◽

Coastal Zones ◽

Surrounding Water ◽

Tidal Current Velocity ◽

Tidal Stream ◽

Tidal Stream Energy

In the present work, the tidal stream energy in surrounding coastal zones of ZTD is calculated. The tidal current velocity is gotten by three dimensional numerical modeling. The tidal current model is validated by measurement of tidal current observed in 4 points surrounding ZTD. The numerical results given by the tidal current model already shows that: the tidal current velocities given by the model agree with the measured velocities generally. The characteristics of tidal currents around ZTD are analyzed and the following tidal stream energy density is calculated. The maximum tidal stream energy flux of unit width occurs around the middle locations of ZTD southern areas.

Download Full-text

Tidal stream energy site assessment via three-dimensional model and measurements

Applied Energy ◽

10.1016/j.apenergy.2012.08.040 ◽

2013 ◽

Vol 102 ◽

pp. 510-519 ◽

Cited By ~ 35

Author(s):

Paul A. Work ◽

Kevin A. Haas ◽

Zafer Defne ◽

Thomas Gay

Keyword(s):

Three Dimensional ◽

Dimensional Model ◽

Three Dimensional Model ◽

Site Assessment ◽

Tidal Stream ◽

Tidal Stream Energy

Download Full-text

Hydrokinetic turbine array modeling for performance analysis and deployment optimization

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2017-0088 ◽

2018 ◽

Vol 42 (4) ◽

pp. 370-381 ◽

Cited By ~ 2

Author(s):

Sébastien Bourget ◽

Olivier Gauvin-Tremblay ◽

Guy Dumas

Keyword(s):

Cfd Simulation ◽

Three Dimensional ◽

Free Surface Flows ◽

Navier Stokes ◽

Cfd Simulations ◽

Power Extraction ◽

Hydrokinetic Turbine ◽

Wake Interactions ◽

Array Optimization ◽

Turbine Wake

The promising preliminary results of an ongoing investigation aimed at developing a turbine array optimization tool are presented. This tool uses three-dimensional Reynolds-averaged Navier–Stokes (3D RANS) CFD simulations of free-surface flows to capture blockage effects and turbine-wake interactions present in dense river arrays. Turbines are represented individually into the river model using actuating regions inside which momentum source terms are distributed non-uniformly and scaled with turbine force coefficients (defined with regards to a local velocity scale). These data are derived from a high-fidelity CFD simulation of the specific turbine operating near maximum power extraction.

Download Full-text

Minimising turbine thrust variation in multi-rotor tidal fences

Journal of Ocean Engineering and Marine Energy ◽

10.1007/s40722-020-00174-8 ◽

2020 ◽

Vol 6 (3) ◽

pp. 293-302

Author(s):

T. F. L. Stephenson ◽

C. R. Vogel

Keyword(s):

Performance Enhancement ◽

Three Dimensional ◽

Navier Stokes ◽

Recent Analysis ◽

Minimal Impact ◽

Energy Devices ◽

Tidal Turbines ◽

Significant Performance ◽

Tidal Stream ◽

Tidal Stream Energy

Abstract Recent analysis of tidal stream energy devices has focussed on maximising power output. Studies have shown that significant performance enhancement can be achieved through the constructive interference effects that develop between tidal stream turbines by deploying them close together. However, this results in variation in the flow incident on the turbines and hence leads to thrust variation across the turbine fence. This may lead to varying damage rates across the fence with adverse impacts on operation and maintenance costs over the turbine lifetime. This study investigates strategies to reduce thrust variation across fences of tidal turbines using three-dimensional Reynolds-Averaged Navier–Stokes simulations. It is shown that the variation in turbine thrust across a fence of eight turbines can be reduced to within 1% with minimal impact on the fence power. Furthermore, by reducing the rotational speed of inboard turbines, or varying the blade pitch angle of the turbines across the fence, it is possible to reduce overall turbine loads and increase the power to thrust ratio of the turbines.

Download Full-text