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• For making the tidal barrages cost-effective, new methods should be implemented to increase the produced power of them. For this purpose, this study suggests new techniques for optimally operating of the basin-based tidal units equipped to hydro-pumps. • According to the proposed technique, to increase the produced power and consequently the produced energy of the basin-based tidal units, at each time step, the number of turbines, sluices and hydro-pumps is optimally determined to yield the maximum produced energy of the generation unit using of different heuristic optimization approaches. • For satisfying the effectiveness of the suggested approach, optimal operating of a basin-based tidal unit installed on the estuary of Bacanga is done and impact of optimally dispatching of the turbines, sluices and hydro-pumps on produced energy of tidal unit is studied. Among different renewable energy-based power plants, barrage type tidal power plants with high installed capacity can be integrated in the bulk power systems. However, due to the high investment cost associated to the construction of the barrages and related components, barrage type tidal power plants are less developed than other renewable resources such as wind turbines and photovoltaic farms. In order to economize the production of electricity from barrage type tidal power plants, it is necessary to reduce the cost of generated electricity by these power plants with new methods. For this purpose, the plant is considered to generate the electricity in the ebb mode, and using the hydro-pumps the height of the water in the reservoir is increased in the flood state. Based on this fact, in this paper, to maximize the generated energy of the barrage type tidal power plant, an optimal design is proposed and the effective parameters of the plant including the number of turbines, the number and width of the sluices, the turbine diameters and the number of hydro-pumps are determined using of three optimization techniques including particle swarm optimization method, genetic algorithm and imperial competition algorithm. [ABSTRACT FROM AUTHOR]

In this work, an AI-Driven (autonomous) model representation of the La Rance tidal barrage was developed using novel parametrisation and Deep Reinforcement Learning (DRL) techniques. Our model results were validated with experimental measurements, yielding the first Tidal Range Structure (TRS) model validated against a constructed tidal barrage and made available to academics. In order to proper model La Rance, parametrisation methodologies were developed for simulating (i) turbines (in pumping and power generation modes), (ii) transition ramp functions (for opening and closing hydraulic structures) and (iii) equivalent lagoon wetted area. Furthermore, an updated DRL method was implemented for optimising the operation of the hydraulic structures that compose La Rance. The achieved objective of this work was to verify the capabilities of an AI-Driven TRS model to appropriately predict (i) turbine power and (ii) lagoon water level variations. In addition, the observed operational strategy and yearly energy output of our AI-Driven model appeared to be comparable with those reported for the La Rance tidal barrage. The outcomes of this work (developed methodologies and DRL implementations) are generalisable and can be applied to other TRS projects. Furthermore, this work provided insights which allow for more realistic simulation of TRS operation, enabled through our AI-Driven model. [Display omitted] • A generalisable AI-Driven model for the La Rance tidal barrage is developed. • Methodologies for parametrising La Rance's hydraulic structures are introduced. • A 0D model representation for La Rance is validated against experimental data. • The AI-Driven La Rance model showcases similar behaviour to the real operation. [ABSTRACT FROM AUTHOR]

Korea has developed various new and renewable energy resources since 2000 due to increasing demand for Green Energy around the world. Because the west coast of Korea has an extreme tidal range, many research projects aimed at harnessing tidal energy have been conducted there successfully. Though the study of Dynamic Tidal Power (DTP) was started as a new tidal energy source about 20 years ago, its characteristics are not yet fully understood. DTP has the potential to have less environmental impact than does a conventional barrage type tidal power generator. Its characteristics were analyzed in many test cases using a numerical model. The theoretical maximum tidal power of DTP became the same as the maximum tidal range by controlling the phase difference. This showed that DTP has great potential for a very successful future in the Yellow Sea. Moreover, DTP could provide an attractive energy source even in areas of lower tidal range than indicated in previous studies. [ABSTRACT FROM AUTHOR]

In this study, enhancements to the numerical representation of sluice gates and turbines were made to the hydro-environmental model Environmental Fluid Dynamics Code (EFDC), and applied to the Severn Tidal Power Group Cardiff–Weston Barrage. The extended domain of the EFDC Continental Shelf Model (CSM) allows far-field hydrodynamic impact assessment of the Severn Barrage, pre- and post-enhancement, to demonstrate the importance of accurate hydraulic structure representation. The enhancements were found to significantly affect peak water levels in the Bristol Channel, reducing levels by nearly 1 m in some areas, and even affect predictions as far-field as the West Coast of Scotland, albeit to a far lesser extent. The model was tested for sensitivity to changes in the discharge coefficient, C d , used in calculating discharge through sluice gates and turbines. It was found that the performance of the Severn Barrage is not sensitive to changes to the C d value, and is mitigated through the continual, rather than instantaneous, discharge across the structure. The EFDC CSM can now be said to be more accurately predicting the impacts of tidal range proposals, and the investigation of sensitivity to C d improves the confidence in the modelling results, despite the uncertainty in this coefficient. [ABSTRACT FROM AUTHOR]

The potential impacts of ebb-only (one-way) and flood-ebb (two-way) modes of operation of a tidal barrage on the eutrophication potential of the Severn Estuary were investigated in this study using the simple modelling approach adopted by the UK’s Comprehensive Studies Task Team (CSTT). The model predictions were compared against CSTT thresholds for assessing eutrophication in estuaries and coastal waters. For the no barrage scenario, as well as the ebb-only and flood-ebb operating modes, the estuary was found to be potentially eutrophic as the predicted equilibrium nutrient concentrations and potential maximum phytoplankton biomass chlorophyll concentrations exceeded the threshold limits. Potential maximum phytoplankton primary productivity under both ebb-only and flood-ebb operating modes were found to be noticeably higher than that for the no barrage scenario. This is believed to be due to a combination of increased water residence time and greater light availability behind the barrage. However, the conditions for phytoplankton production are likely to be more favourable under ebb-only operating mode as the potential for maximum phytoplankton primary production was found to be significantly increased under ebb-only operating mode, with largely decreased suspended particulate matter concentration compared to flood-ebb operating mode where only a small reduction in suspended particulate matter concentration is predicted. [ABSTRACT FROM AUTHOR]

Abstract: Some previous work has made optimistic claims about the potential energy gains that could be made by using pumping with tidal range structures (barrages, lagoons and offshore tidal impoundments). This paper explores the factors influencing whether such gains can be realised for positive head pumping (pumping once water levels have equalised), using 0-D modelling concepts. [Copyright &y& Elsevier]

Abstract: In recent years, there have been growing international challenges relating to climate change and global warming, with a conflict developing between the need to create a low-carbon economy and rapid depleting reserves of fossil fuels. In addition to these challenges there continues to be the added complexity of a significant global increase in energy demand. Marine renewable energy from tidal barrages is carbon-free and has the potential to make a significant contribution to energy supplies now and in the future. Therefore, it is appropriate to evaluate the total energy that can be extracted from such barrages. In this study two different methods are proposed to estimate the total annual energy output from a barrage, including a theoretical estimation based on the principle associated with tidal hydrodynamics, and a numerical estimation based on the solutions obtained from a 2D hydrodynamic model. The proposed Severn Barrage in the UK was taken as a case study, and these two methods were applied to estimate the potential annual energy output from the barrage. The predicted results obtained using the two methods indicate that the magnitude of the annual energy output would range from 13 to 16TWh, which is similar to the value of 15.6TWh reported by the Department of Energy and Climate Change, in the UK. Further investigations show that the total annual energy output would increase by about 15% if a higher discharge coefficient were to be adopted for the sluice gates, or if the turbine performance were to be improved. However, the estimated annual energy output could exceed the value of 16TWh if future technological advances in both sluice gate construction and turbine performance are included. [Copyright &y& Elsevier]

Abstract: The Severn Estuary has a spring tidal range approaching 14m and is regarded as having one of the highest tidal ranges in the world. Various proposals have been made regarding the construction of a tidal barrage across the estuary to enable tidal energy to be extracted. The barrage scheme originally proposed by the Severn Tidal Power Group (STPG) would be the largest project for tidal power generation in the world if built as proposed. Therefore, it is important to study the impact of different operating modes for this barrage on the tidal power output and flood inundation extent in the estuary. In this paper, an existing two-dimensional hydrodynamic model based on an unstructured triangular mesh has been integrated with a new algorithm developed for the estimation of tidal power output, which can account for three barrage operating modes, including ebb generation, flood generation, and two-way generation. The refined model was then used to investigate the impact of different barrage operating modes on the tidal power output and the associated extent of flood inundation along the Severn Estuary. Predicted results indicate that the mode of flood generation would produce the least electrical energy and cause a larger reduction in the maximum water levels upstream of the barrage. Two-way generation would provide an improvement to these conditions, and produce an equivalent amount of electricity to that from ebb generation, with a low installed capacity and a small loss of intertidal zones. Therefore, the mode of ebb generation or two-way generation would appear to be a preferred option for power generation, because both would offer benefits of acceptable electrical energy and reduced flood risk. [Copyright &y& Elsevier]

Abstract: The Severn Estuary, located in the UK between south east Wales and south west England, is an ideal site for tidal renewable energy projects, since this estuary has the third highest tidal range in the world, with a spring tidal range approaching 14m. The UK Government recently invited proposals for tidal renewable energy projects from the estuary and many proposals were submitted for consideration. Among the proposals submitted and subsequently shortlisted were: the Cardiff–Weston Barrage, the Fleming Lagoon and the Shoots Barrage, all three of which are nationally public interest. Therefore a two-dimensional finite volume numerical model, based on an unstructured triangular mesh, has been refined to study the hydrodynamic impact and flood inundation extent, post construction, of all three of these proposed tidal power projects. The model-predicted hydrodynamic processes have been analysed in detail, both without and with the structures, including the discharge processes at key sections, the contours of maximum and minimum water levels, the envelope curves of high and low water levels, the maximum tidal currents, the local velocity fields around the structures and the mean power output curves. Simulated results indicate that: (i) although the construction of the Cardiff–Weston Barrage would have an adverse impact on a range of environmental aspects, due to there being approximately a 50% decrease in the peak discharge entering the upstream region, it would reduce the maximum water levels upstream of the barrage by typically 0.3–1.2m, which could be positive in respect of coastal flooding; (ii) the construction of the Fleming Lagoon would have little influence on the hydrodynamic processes in the Severn Estuary; and (iii) the construction of the Shoots Barrage would decrease the maximum water levels upstream of the M4 bridge by between 0.3 and 1.0m, but it could lead to an increase in the maximum water levels downstream of the barrage by typically 20–30cm. [Copyright &y& Elsevier]

The sudden rise in oil price in 1970s led various countries around the world to turn to renewable energy resources for electric power generation instead of fossil fuel-based power plants. Among different renewable power generations, wind and solar power plants have reached maturity and have been able to make a significant contribution to electricity supply. Tidal power plants have grown less due to high cost of investment. Hence, their share of electricity generation has been lower than that of wind and solar power plants. The potential of tidal energy is high and it is expected that tidal energy can play a key role for electricity production in the future power-system due to its accurate predictability. Two types of tidal power plants including barrage-type and current-type tidal power plants are developed for energy extracting from tides. The current-type tidal power plant generates electricity from the kinetic energy of tidal-currents in a way similar to wind-turbines, while the barrage-type tidal power plants are equipped with dam, barrage and reservoir in order to generate electricity from the potential energy of water stored in the reservoir. This paper proposes several methods for enhancing the generated power of barrage-type tidal power plants, which result in cost reduction of electricity generated by tidal power plants. At first, an optimum design procedure for calculating the optimum values of number of turbines, number of gates, sluice width, turbine tip diameter and turbine hub diameter is established based on the particle-swarm-optimization-algorithm, aiming to maximize the yearly produced energy. Then, the hourly optimum number of gates and turbines are calculated in the operation studies for maximizing the daily produced energy. Also, the utilization of hydro-pump is simulated as the third method of generated power enhancement. In addition, three operation modes of barrage-type power plants, including ebb-generation, flood-generation and double-effect generation are simulated and the best operation mode in terms of power generation is determined. [ABSTRACT FROM AUTHOR]

• Remaining useful life and fatigue analysis of the blades have been discussed. • Most dangerous operating conditions for crack propagation have been determined. • The conclusions of these study could be contrasted with real cracks observed in prototypes. • CFD coupled with structural FEM considering an initial defect has been used. • Characteristics of pressure fluctuations and dynamic stresses have been presented. Tidal energy systems and specifically tidal barrages are renewable energy systems, that use the potential energy of tides to produce electricity. Actually, there are few tidal power stations operating, although recent studies show the potentiality of installing new units in a recent future due to the constant improvement of the technology related. As in other conventional hydropower systems, the runner is one of the critical components of the unit as it has to withstand an extreme wide range of relative head and two main operating modes (ebb and flood). Therefore, fatigue problems and undesirable failures are more likely to occur. Based on the analysis of a crack found in one of the blades of a prototype, this paper analyzes and discusses under which operating conditions the runner is more likely to suffer from fatigue problems. CFD and FEM simulation models have been used to determine the stress hotspots, which approximate very well the point where the real crack was initiated. Based on a probabilistic approach of an existing initial defect or flaw, the reliability of the blades, or the probability of not growing a crack and therefore last an infinite life, has been calculated for a wide range of operating conditions. While fatigue problems have been deeply discussed and analyzed in conventional turbines, the flow excitation characteristics in these units exhibit important differences and therefore the discussion and results provided in this paper could be useful for future designs and fatigue analyses of tidal turbines. [ABSTRACT FROM AUTHOR]