scholarly journals The energy yield potential of a large tidal stream turbine array in the Alderney Race

2020 ◽  
Vol 378 (2178) ◽  
pp. 20190502 ◽  
Author(s):  
D. S. Coles ◽  
L. S. Blunden ◽  
A. S. Bahaj
Keyword(s):  
Large Scale ◽  
Tidal Energy ◽  
Yield Potential ◽  
Energy Yield ◽  
Ambient Flow ◽  
Flow Speeds ◽  
Tidal Stream ◽  
Original Array ◽  
Array Performance ◽  
Tidal Stream Turbine

This research provides an updated energy yield assessment for a large tidal stream turbine array in the Alderney Race. The original array energy yield estimate was presented in 2004. Enhancements to this original work are made through the use of a validated two-dimensional hydrodynamic model, enabling the resolution of flow modelling to be improved and the impacts of array blockage to be quantified. Results show that a range of turbine designs (i.e. rotor diameter and power capacity) are needed for large-scale development, given the spatial variation in bathymetry and flow across the Alderney Race. Array blockage causes a reduction in flow speeds in the array of up to 2.5 m s −1 , increased flow speeds around the array of up to 1 m s −1 and a reduction in the mean volume flux through the Alderney Race of 8%. The annual energy yield estimate of the array is 3.18 TWh, equivalent to the electricity demand of around 1 million homes. The capacity factor of the array is 18%, implying sub-optimal array design. This result demonstrates the need for turbine rated speed to be selected based on the altered flow regime, not the ambient flow. Further enhancement to array performance is explored through increases to rotor diameter and changes to device micro-siting, demonstrating the significant potential for array performance improvement. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

scholarly journals Identifying economically viable tidal sites within the Alderney Race through optimization of levelized cost of energy

2020 ◽  
Vol 378 (2178) ◽  
pp. 20190500
Author(s):  
Z. L. Goss ◽  
D. S. Coles ◽  
M. D. Piggott
Keyword(s):  
Large Scale ◽  
Tidal Energy ◽  
Monte Carlo Analysis ◽  
Lessons Learned ◽  
Fixed Costs ◽  
Levelized Cost ◽  
Learning Rates ◽  
Cost Of Energy ◽  
Case Study Site ◽  
Tidal Stream

Costs of tidal stream energy generation are anticipated to fall considerably with array expansion and time. This is due to both economies of volume, where arrays comprising of large numbers of turbines can split fixed costs over a greater number of devices, and learning rates, where the industry matures and so arrays of the same size become cheaper due to lessons learned from previous installations. This paper investigates how tidal energy arrays can be designed to minimize the levelized cost of energy (LCOE), by optimizing not only the location but also the number of devices, to find a suitable balance between decreased costs due to economies of volume and diminishing returns due to global blockage effects. It focuses on the Alderney Race as a case study site due to the high velocities found there, making it a highly suitable site for large-scale arrays. It is demonstrated that between 1 and 2 GW could be feasibly extracted as costs in the tidal industry fall, with the LCOE depending greatly on the assumed costs. A Monte–Carlo analysis is undertaken to account for variability in capital and operational cost data used as inputs to the array optimization. Once optimized, the estimated P50 LCOE of an 80 MW array is £110/MWh. This estimate aligns closely with the level of subsidy considered for tidal stream projects in the Alderney Race in the past. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

Effects on hydrodynamics and ecological costs of climate change and tidal stream energy extraction in a shelf sea

2020 ◽  
Author(s):  
Michela De Dominicis ◽  
Judith Wolf ◽  
Dina Sadykova ◽  
Beth Scott ◽  
Alexander Sadykov ◽  
...  
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Climate Scenario ◽  
Tidal Energy ◽  
Ocean Model ◽  
Future Climate ◽  
Biogeochemical Model ◽  
Energy Extraction ◽  
Shelf Sea ◽  
Tidal Stream

<p>The aim of this work is to analyse the potential impacts of tidal energy extraction on the marine environment. We wanted to put them in the broader context of the possibly greater and global ecological threat of climate change. Here, we present how very large (hypothetical) tidal stream arrays and a ''business as usual'' future climate scenario can change the hydrodynamics of a seasonally stratified shelf sea, and consequently modify ecosystem habitats and animals’ behaviour.</p><p>The Scottish Shelf Model, an unstructured grid three-dimensional ocean model, has been used to reproduce the present and the future state of the NW European continental shelf. While the marine biogeochemical model ERSEM (European Regional Seas Ecosystem Model) has been used to describe the corresponding biogeochemical conditions. Four scenarios have been modelled: present conditions and projected future climate in 2050, each with and without very large scale tidal stream arrays in Scottish Waters (UK). This allows us to evaluate the potential effect of climate change and large scale energy extraction on the hydrodynamics and biogeochemistry. We found that climate change and tidal energy extraction both act in the same direction, in terms of increasing stratification due to warming and reduced mixing, however, the effect of climate change is ten times larger. Additionally, the ecological costs and benefits of these contrasting pressures on mobile predator and prey marine species are evaluated using ecological statistical models.</p>

scholarly journals Accuracy of the actuator disc-RANS approach for predicting the performance and wake of tidal turbines

2013 ◽  
Vol 371 (1985) ◽  
pp. 20120293 ◽  
Author(s):  
W. M. J. Batten ◽  
M. E. Harrison ◽  
A. S. Bahaj
Keyword(s):  
Large Scale ◽  
Scale Effects ◽  
Tidal Energy ◽  
Rans Model ◽  
Tidal Turbines ◽  
Actuator Disc ◽  
Element Approach ◽  
Tidal Stream ◽  
Turbine Wake ◽  
Horizontal Axis Turbine

The actuator disc-RANS model has widely been used in wind and tidal energy to predict the wake of a horizontal axis turbine. The model is appropriate where large-scale effects of the turbine on a flow are of interest, for example, when considering environmental impacts, or arrays of devices. The accuracy of the model for modelling the wake of tidal stream turbines has not been demonstrated, and flow predictions presented in the literature for similar modelled scenarios vary significantly. This paper compares the results of the actuator disc-RANS model, where the turbine forces have been derived using a blade-element approach, to experimental data measured in the wake of a scaled turbine. It also compares the results with those of a simpler uniform actuator disc model. The comparisons show that the model is accurate and can predict up to 94 per cent of the variation in the experimental velocity data measured on the centreline of the wake, therefore demonstrating that the actuator disc-RANS model is an accurate approach for modelling a turbine wake, and a conservative approach to predict performance and loads. It can therefore be applied to similar scenarios with confidence.

scholarly journals Characterization of the vertical evolution of the three-dimensional turbulence for fatigue design of tidal turbines

2020 ◽  
Vol 378 (2178) ◽  
pp. 20190495 ◽  
Author(s):  
Maxime Thiébaut ◽  
Jean-François Filipot ◽  
Christophe Maisondieu ◽  
Guillaume Damblans ◽  
Christian Jochum ◽  
...  
Keyword(s):  
Turbulence Intensity ◽  
Large Scale ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Tidal Energy ◽  
Tidal Turbines ◽  
Tidal Stream ◽  
Vertical Evolution ◽  
Tidal Stream Energy ◽  
Scale Turbulence

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’.

scholarly journals Lateral Effluent Discharge Apparatus for a Tidal Turbine (Where Does the Water Go?)

2017 ◽  
Vol 51 (6) ◽  
pp. 86-94
Author(s):  
George McBride ◽  
Chayut Teeraratkul
Keyword(s):  
Patent Application ◽  
Tidal Energy ◽  
Flow Speed ◽  
The Novel ◽  
Ambient Flow ◽  
Tidal Turbine ◽  
Acceleration Zone ◽  
Tidal Stream ◽  
Effluent Discharge ◽  
The University

AbstractTidal energy harvested from flowing ocean waters is a promising sector of renewable energy in many coastal areas of the world. Challenges of cost mean that more efficient turbines are required to make tidal energy comparable with other energy sources. Downeast Turbines is developing a shrouded tidal turbine with patented rotor and channel system that concentrates ocean currents flowing through. Flow goes in with energy and comes out “spent,” its energy removed. Discharging spent flow back into the tidal stream is not an easy matter to perform, and two problems are commonly encountered: impaired efficiency of the turbine and impaired efficiency of a tidal turbine farm. Downeast Turbines' Lateral Effluent Discharge Apparatus, with patent application published and patent recently issued, addresses these two problems. It provides a means to discharge turbine effluent laterally into an acceleration zone of the stream that passes by, instead of directly to the wake downstream.In 2017, a series of two-dimensional computer simulations (2-D CFD) was performed at the University of Rochester to assess how the novel apparatus works. Nine configuration variations were modeled and tested in varying conditions of ambient flow speed and turbine load. Over 250 simulations were performed, and sample results are provided in figures and a table to show how the novel apparatus performed. Color maps of pressure, velocity and streamline vectors, and CP performance calculations, all suggest the novel apparatus works. Benefits of the apparatus might improve performance for any shrouded tidal turbine, not just Downeast Turbines' own.

Estimation of the Energy Potential of the Euripus' Gulf Tidal Stream Using Channel Sea-surface Slope

2015 ◽  
Vol 3 (4) ◽  
pp. 23-42 ◽  
Author(s):  
Aphrodite Ktena ◽  
Christos Manasis ◽  
Dimitrios Bargiotas ◽  
Vasilis Katsifas ◽  
Takvor Soukissian ◽  
...  
Keyword(s):  
Sea Level ◽  
Tidal Energy ◽  
Energy Yield ◽  
Energy Extraction ◽  
Low Velocity ◽  
Energy Potential ◽  
Yield Data ◽  
Island Communities ◽  
Tidal Stream ◽  
Harmonic Analysis Method

Potential energy extraction from tidal currents is investigated in this work. Recordings on the streams' velocity and the sea level in the Euripus' strait in Evia, Greece are used to calculate the energy yield. Data on sea level measurements were used to extract information for the current velocity profile through harmonic analysis method. Requirements, limitations and possible new designs that will improve the energy extraction from the low velocity tidal current of the area are discussed. Also, exploitation of tidal energy in cooperation with RES microgrid is proposed for areas where the abundance of sun, wind, island communities and coast areas such as the Mediterranean.

scholarly journals Using Blade Element Momentum Theory to Predict the Effect of Wave-Current Interactions on the Performance of Tidal Stream Turbines

2021 ◽  
Vol 4 (1) ◽  
pp. 25-36
Author(s):  
Song Fu ◽  
Stephanie Ordonez-Sanchez ◽  
Rodrigo Martinez ◽  
Cameron Johnstone ◽  
Matthew Allmark ◽  
...  
Keyword(s):  
Experimental Work ◽  
Numerical Solutions ◽  
Tidal Energy ◽  
S Wave ◽  
Flow Speeds ◽  
Wave Heights ◽  
Tidal Stream ◽  
Thrust And Torque ◽  
Good Agreement ◽  
Blade Element

The non-uniformity and dynamics of the environment tidal stream turbines need to operate within will significantly influence the durability and reliability of tidal energy systems. The loadings on the turbine will increase substantially when the turbine is deployed in high magnitude waves with non-uniform tidal currents. The limitations of numerical solutions will be understood when the outcomes are verified with empirical data from system operations.  In this paper, a Blade Element Momentum model is used to predict and compare the performance of a scaled turbine within a flume and a tow tank. Firstly, the numerical and experimental work is analysed for a turbine operating at flow speeds of 0.5m/s amd 1.0 m/s, wave heights of 0.2 m and 0.4 m and wave periods of 1.5 s and 1.7 s. Good agreement between the model and the experimental work was observed. However, in low TSRs the model tends to under predict the thrust, and the variation between the maximum and minimum values obtained within the experiments. Secondly, a turbine operating at flow speeds of 1.0 m/s and 4 different inflow profiles is analysed, where the wave heights for these cases were 0.09 m and 0.19 m and with wave periods of 2 s and 1.43 s. In this evaluation, the model tends to over predict the values of Ct and Cp when compared to those calculated from the experimental data. However, when investigating the values used to calculating both the thrust and torque coefficients, there is better agreement with these, which means the methodology used to determine these coefficients with inflow profiles should be revised. 

scholarly journals Tidal Energy: The benthic effects of an operational tidal stream turbine

2017 ◽  
Vol 129 ◽  
pp. 277-290 ◽  
Author(s):  
J.P.J. O'Carroll ◽  
R.M. Kennedy ◽  
A. Creech ◽  
G. Savidge
Keyword(s):  
Tidal Energy ◽  
Tidal Stream ◽  
Tidal Stream Turbine

scholarly journals A Combined Approach for Model-Based PV Power Plant Failure Detection and Diagnostic

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1261
Author(s):  
Christopher Gradwohl ◽  
Vesna Dimitrievska ◽  
Federico Pittino ◽  
Wolfgang Muehleisen ◽  
András Montvay ◽  
...  
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Failure Detection ◽  
Energy Yield ◽  
Combined Approach ◽  
Levelized Cost Of Electricity ◽  
Term Operation ◽  
Model Based

Photovoltaic (PV) technology allows large-scale investments in a renewable power-generating system at a competitive levelized cost of electricity (LCOE) and with a low environmental impact. Large-scale PV installations operate in a highly competitive market environment where even small performance losses have a high impact on profit margins. Therefore, operation at maximum performance is the key for long-term profitability. This can be achieved by advanced performance monitoring and instant or gradual failure detection methodologies. We present in this paper a combined approach on model-based fault detection by means of physical and statistical models and failure diagnosis based on physics of failure. Both approaches contribute to optimized PV plant operation and maintenance based on typically available supervisory control and data acquisition (SCADA) data. The failure detection and diagnosis capabilities were demonstrated in a case study based on six years of SCADA data from a PV plant in Slovenia. In this case study, underperforming values of the inverters of the PV plant were reliably detected and possible root causes were identified. Our work has led us to conclude that the combined approach can contribute to an efficient and long-term operation of photovoltaic power plants with a maximum energy yield and can be applied to the monitoring of photovoltaic plants.

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