Tidal Barrage Research Articles

Simulation Model to Assess Electrical Power Generation from Tidal Basin in Coastal Area of Malaysia

This article studies the numerical simulation of power generation in four different tidal stations in the East Coast region of Malaysia. The tidal stations are Tanjung Sedili, Tanjung Gelang, Tioman and Cendering. The simulation model is based on power generation using tidal barrage. Ebb, flood and double-mode generations were studied. The tidal basin area was estimated by approximation to generate sufficient electricity for local community consumption. Thus, a different basin area was estimated for every location as each location has different population size. Single-flow generation was assumed for ebb and floor generations with 40% barrage efficiency while bi-directional generation was assumed for double-mode generation with 30% barrage efficiency. Double-mode generation has the highest power generation among the three different methods. Tanjung Gelang has the highest average tidal range difference. However, Pulau Tioman is more suitable to have the tidal barrage as the local community population is smaller, thus, requiring a smaller basin area to generate sufficient electricity to meet the demand of local community. On average, tidal barrage with a basin area of 0.3km2 in Pulau Tioman will be able to generate 13.74 GWh annually.

Simulation Model to Assess Tidal Potential Energy in East Coast of Malaysia Using GIS

This article studies the GIS simulation of yearly power generation in five different tidal stations in the East Coast region of Malaysia. The tidal stations are Geting, Tanjung Gelang, Tioman, Tanjung Sedili and Cendering. The tidal station in Geting is not analysed in this study because the tidal range is insignificant. After analysing the lagoons nearby to the four tidal stations, Tanjung Gelang and Tanjung Sedili are chosen in this study based on their natural characteristics and geomorphology of lagoons. The simulation model is based on yearly power generation using tidal barrage. This article also looks into the model in terms of mapping using GIS software to obtain bathymetry and tidal range data. Bathymetry data in GIS format is obtained from NOAA (National Oceanic and Atmospheric Administration) and tidal range data is obtained from ‘Jabatan Ukur dan Pemetaan Malaysia’. The latest tidal data up to date is the year 2011. The minimum depth of tidal basin should be 3.0 meter. Using GIS software to analyse bathymetry and tidal range data, the results are then combined to find yearly generation power output in the two tidal stations and are plotted in one map for each tidal station. The area of basin in Tanjung Gelang and Tanjung Sedili are 17.736 km2 and 27.919 km2. The calculation includes the important parameters such as area of basin, tidal range, number of tide cycles per year, and number of hours per tide. From the results and analysis, it is concluded that Tanjung Sedili and Tanjung Gelang produce 1.528 x 108 kWh and 1.294 x 108 kWh as their yearly power generation in 2011.

An assessment of the impacts of a tidal renewable energy scheme on the eutrophication potential of the Severn Estuary, UK

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.

Physical and numerical modelling of the Severn Barrage

The Severn Estuary has one of the largest tidal ranges in the world and has long been the subject of consideration for tidal energy generation. Whilst plans to build a tidal barrage across the estuary have existed in various forms since the 1920s, the 1989 Severn Tidal Power Group (STPG) proposal is commonly referred to as the original Severn Barrage. The UK government abandoned this ebb generation scheme as a public investment project in 2010. However, plans to build a two-way generation scheme were more recently put forward by a private consortium, namely Hafren Power. To assess the impact that a barrage would have on the hydro-environment in the estuary a number of numerical modelling studies have previously been conducted for the STPG scheme. As this design has now been superseded by the Hafren Power proposal, new studies have been conducted to investigate the impact of a two-way scheme. In this study the hydro-environmental impacts of both ebb-only and two-way schemes were assessed using physical and numerical modelling techniques. Scale model barrages were constructed and testing was carried out using a physical model of the Severn Estuary, located in the hydraulics laboratory at Cardiff University. A depth integrated numerical model, namely DIVAST, was applied to the physical model geometry and modifications were made to simulate the effects of the barrage structures. The numerical model predictions showed good agreement with the corresponding laboratory data. The results were consistent with conclusions from previous studies, relating to the ebb-only scheme. These included an increase in the minimum water levels upstream of the barrage, a reduction in the mean water levels downstream of the barrage and a general reduction in tidal velocities. For a two-way scheme changes in the tidal elevations and velocities depended on the exact operating conditions of the barrage. It was found that with no starting head the tidal regime was similar to the natural state, with little change in the elevations and a slight reduction in the mean velocities. As a starting head was introduced there was still little change in elevations downstream of the barrage, however, there was an increase in the minimum water levels upstream of the barrage, and a further reduction in the mean velocities.

A methodology for the assessment of local-scale changes in marine environmental benefits and its application

Local-scale planning decisions are required by the existing Environmental Impact Assessment process to take account of the implications of a development on a range of environmental and social factors, and could therefore be supported by an ecosystem services approach. However, empirical assessments at a local scale within the marine environment have focused on only a single or limited set of services. This paper tests the applicability of the ecosystem services approach to environmental impact appraisal by considering how the identification and quantification of a comprehensive suite of benefits provided at a local scale might proceed in practice. A methodology for conducting an Environmental Benefits Assessment (EBA) is proposed, the underlying framework for which follows the recent literature by placing the emphasis on ecosystem benefits, as opposed to services. The EBA methodology also proposes metrics that can be quantified at local scale, and is tested using a case study of a hypothetical tidal barrage development in the Taw Torridge estuary in North Devon, UK. By suggesting some practical steps for assessing environmental benefits, this study aims to stimulate discussion and so advance the development of methods for implementing ecosystem service approaches at a local scale.

Shifts in fish assemblages indicate failed recovery of threatened species following prolonged drought in terminating lakes of the Murray–Darling Basin, Australia

Freshwater fishes are vulnerable to changes in water quality, physical habitat and connectivity resulting from drought, particularly in regulated rivers. When adequate river flows return, the recovery of populations might depend on the duration and consequences of drought. Rivers of the highly regulated Murray–Darling Basin in south-eastern Australia terminate at two large, shallow lakes that are separated from the estuary by tidal barrages. Over-abstraction of water and widespread prolonged drought (1997–2010) placed the lakes under severe environmental stress, culminating in critical water level recession from 2007 to 2010. Concurrently, most freshwater fish populations collapsed. We investigate shifts in fish assemblages resulting from habitat inundation in the lakes following the drought. The inundation and re-connection of the lakes and fringing habitats led to a substantial reduction of salinity throughout the region, and aquatic vegetation shifted from salt-tolerant to freshwater species. Fish assemblages became increasingly characterized by common freshwater taxa (ecological generalists), including high proportions of alien species. There were no indications of population recovery for three threatened species. The findings emphasize that short-lived fishes with specialized habitat requirements are vulnerable to severe population declines during prolonged drought in regulated rivers, which might restrict their recovery when adequate flows return.

An Evaluation of Seawater Pumped Hydro Storage for Regulating the Export of Renewable Energy to the National Grid

A seawater inlet with a surface area of 6 km2 was assessed for the potential to be used as a 100 MW, low head, high flow, sea water pumped hydro energy storage system. The capital cost was estimated to be recouped after a number of years and the plant has a predicted energy storage capacity of 320 MWh.National and international policies are driving the increased penetration of solar and wind energy onto the electricity networks, in an effort to reduce carbon emissions. Transmissions System Operators depend on ancillary services such as spinning reserve from thermal generators or pumped hydro systems to enhance grid stability. The increased penetration of renewable energy onto the electricity grid is driving a demand for greater capacity in the area of energy storage.This research presents a case study, which is a technical and economical appraisal of using an inland sea water reservoir to store energy. This project involves building a seawater dam around an existing natural inlet, and placing turbines at the mouth of the inlet. As part of the study an evaluation of current pumped hydro, seawater storage, and tidal barrages was carried out. The optimum design of the low head, high flow rate seawater energy storage facility was determined for the seawater inlet and different scenarios for the optimum head and flow rates are presented for analysis.Using low-head, high-flow seawater storage near the coast, greatly reduces the danger of contamination of inland freshwater supplies, thus reducing the environmental impact of pumped seawater energy storage.This research indicates that sea water pumped hydro energy storage with a high flow rate and low head is technically and economically feasible for increasing the ability of national grids to allow high penetration of intermittent renewable energy.

Effects of open boundary location on the far-field hydrodynamics of a Severn Barrage

The Severn Estuary has the second largest tide range in the world and a barrage across the estuary from Cardiff in South Wales to Weston in South West England has been proposed for over half a century, to extract large amounts of tidal energy from the estuary. To assess the environmental impacts of the proposed tidal barrage requires accurate model predictions of both the near-field and far-field hydrodynamics, which can strongly depend on the model area and the appropriate boundary forcing. In this paper two models, based on the Environmental Fluid Dynamics Code (EFDC) numerical model with a recently-developed Barrage module (EFDC_B), were set up with different computational domains. The Continental Shelf model, which was centred on the Bristol Channel, has its open boundary extended to beyond the Continental Shelf. The Irish Sea model, which was also centred around the Bristol Channel, only has its open boundary extended to the Celtic Sea in the south and the Irish Sea in the north. In order to investigate the effects of the open boundary conditions imposed in the models on the near and far-field hydrodynamics for the case of the Severn Barrage, the Continental Shelf model was first run with and without the operation of the Severn Barrage. The Irish Sea model was then run, also with and without the operation of the Severn Barrage, and with the open boundary conditions provided by the Continental Shelf model. The results from both models were then analysed to study the impact of the tidal barrage on the near-field and far-field hydrodynamics in the Bristol Channel and Irish Sea. Detailed comparisons of the model results indicate that the hydrodynamic conditions along the open boundaries of the Irish Sea model are affected by the tidal barrage and that the open boundary conditions also have noticeable impacts on the far-field hydrodynamics, especially in the Irish Sea, with approximately an average 4–7cm difference in the maximum water levels predicted in Cardigan Bay and with a maximum difference of 9cm in the northern part of Cardigan Bay.

Coastal hydrodynamics – present and future

This paper gives a personal view of the state of coastal hydrodynamics, mainly from a modelling perspective. The traditional areas of tidal flows and wave propagation are highlighted first. Their impact is evolving due to climate change generally and sea level rise particularly with massive economic and human consequences, raising the importance of coastal hydrodynamics. The emerging renewable energy technologies of offshore wind, tidal stream, wave and possibly tidal barrage will further dramatically expand the coastal hydrodynamics domain in the near future. The emerging methods of smoothed particle hydrodynamics for fluid-solid interaction and adjoint modelling for improved surge and tidal prediction are considered. Some of the broader issues of large-scale morphodynamics are also discussed.

Operational optimisation of a tidal barrage across the Mersey estuary using 0-D modelling

With the operational lifetime of a tidal barrage stretching up to 120 years, it is important to be able to change the level of energy generation with varying trends in energy demand. Unlike other technologies, the energy generation level and sequence of a tidal barrage can be significantly altered without any physical change to the barrage by varying only the operational parameters. In order to explore this, a computational model which calculates the energy generation for a barrage across the Mersey estuary was developed. The model uses cutting edge double regulated turbine technology and bathymetric data and explores how this can be achieved without changing the physical parameters of the barrage. The derived results were compared to previous studies and found to match and exceed the results of past predictions.

Modeling effects of a tidal barrage on water quality indicator distribution in the Severn Estuary

In this study, emphasis has focused on assessing the potential hydro-environmental impacts of a barrage across the Severn Estuary, with a numerical model being developed and applied to the estuary to assess the impacts of proposed Severn Barrage on the hydrodynamic, sediment transport and faecal indicator organism distribution within the estuary. The results show that the Severn Barrage has the potential to reduce the tidal currents in a highly dynamic estuary. This leads to the reduction of suspended sediment concentrations, which in turn affects the bacterial transport processes which is highly related to the sediment transport processes.

Harnessing Tidal Energy Using Vertical Axis Tidal Turbine

An overview of the current design practices in the field of Renewable Energy (RE) is presented; also paper delineates the background to the development of unique and novel techniques for power generation using the kinetic energy of tidal streams and other marine currents. Also this study focuses only on vertical axis tidal turbine. Tidal stream devices have been developed as an alternative method of extracting the energy from the tides. This form of tidal power technology poses less threat to the environment and does not face the same limiting factors associated with tidal barrage schemes, therefore making it a more feasible method of electricity production. Large companies are taking interest in this new source of power. There is a rush to research and work with this new energy source. Marine scientists are looking into how much these will affect the environment, while engineers are developing turbines that are harmless for the environment. In addition, the progression of technological advancements tracing several decades of R & D efforts on vertical axis turbines is highlighted.

Exploring the Effect of Length and Angle on NACA 0010 for Diffuser Design in Tidal Current Turbines

Tidal energy is one of the most predictable forms of renewable energy.Tides posses both potential and kinetic energy. Tidal energy can be utilized by capturing potential energy i.e. by means of tidal barrage and tidal fence or by capturing kinetic energy i.e. by menas of tidal current technologies. This study is focused on diffuser augmented tidal turbines that capture the kinetic energy. The power generated by a tidal turbine is directly proportional to the cube of velocity of current flow. The role of the diffuser in diffuser augmented tidal turbines is to help accelerate the incoming current velocity. Consequently, the efficiency of the turbine is significantly increasedby using adiffuser. The research community is investing considerable time and financial resources in thisgrowingdomain. The diffuser augmented tidal turbinesresearch datais rather scarce due to their emerging nature, large and costly research & development setup, startup cost and proprietary issues. The purpose of this paper is to study the effect of length and angle on NACA 0010airfoil for diffuser design. Numerical simulation is carried out to investigate velocity and mass flow rate at the throat. The drag force due to diffuser installation is also calculated.

Novel offshore application of photovoltaics in comparison to conventional marine renewable energy technologies

An original proposal for the deployment of photovoltaic (PV) systems in offshore environments is presented in this paper. Crystalline PV panels are considered where they are deployed on pontoon type structures and there are six case study examples precedent practise of such deployments in lakes and reservoirs (but not seas). The authors put forward an alternative based on flexible thin film PV that floats directly on the waterline. The paper then concentrates on the techno-economic appraisal of offshore PV systems in comparison to conventional marine renewable energy technologies. The difficulties of comparing offshore technology projects developed in various countries, using different currencies and in different years are overcome so that such comparisons are made on an equitable basis. The discounted cost of electricity generated by each scheme is determined, including capital expenditure (CAPEX) and yearly operation and maintenance (O&M) costs.Actual wind, tidal (current turbines and barrages) and wave projects were considered in the analysis alongside crystalline and thin film PV. Thin film PV was found to be economically competitive with offshore wind energy projects for latitudes ranging from 45°N to 45°S. The specific yield, assessed in terms of GWh/km2 was higher for thin film PV than for wind, wave and tidal barrage systems. In addition the specific installed capacity, expressed in MW/km2 was also higher than the other conventional technologies considered (excluding tidal current turbines).

An energy and carbon life cycle assessment of tidal power case study: The proposed Cardiff–Weston severn barrage scheme

Under the Kyoto Protocol many countries have targets to reduce carbon emissions and increase renewable energy production. In order to do this effectively the impact and efficacy of differing schemes must be determined. One option for producing electricity is through the use of a tidal barrage. The largest potential barrage scheme considered in the UK is the Cardiff–Weston barrage scheme in the Severn estuary. The scheme would be a single, renewable installation and is predicted to constitute 4% of the UK electricity supply. Therefore a carbon and energy assessment was completed on the Cardiff–Weston Severn barrage scheme. The assessment shows that the energy and carbon intensity of the Severn barrage is small in comparison to the National Grid mix and that, given reasonable assumptions, the Severn barrage can contribute to meeting the UK carbon reduction target. Importantly, the operation stage was identified as both the most energy and carbon intense by a large margin. This is a notable finding as preceding studies have tended to dismiss the consequences of the barrage operation as minimal or nil. Whilst these findings are for the Cardiff–Weston barrage, the implications will be similar for tidal barrages in other sites in the UK and globally.

Geomorphological analogues for large estuarine engineering projects: A case study of barrages, causeways and tidal energy projects

Two conceptual models have been proposed to predict the response of sediment-laden estuaries to reduced tidal propagation caused by tidal barrages. One argues that reduced tidal energy will increase inter-tidal sedimentation; the other suggests that reduced tidal propagation will trigger a period of erosion before accretion of inter-tidal resumes. This paper investigates the relevance of sills across UK estuaries and causeways and barriers across estuaries in the Bay of Fundy (Nova Scotia, Canada) as possible analogues. Particular attention is paid to the tidal power barrage at Annapolis Royal because it exhibits important features that provide the underpinning evidence for morphological responses within tidal power headponds.The construction of the tidal power plant at Annapolis Royal involved retro-fitting a tidal turbine and re-establishment of tidal influences into a headpond which had been maintained at a relatively constant level for some 24 years previously. The sequence of events at Annapolis Royal shows that headponds behave like river reservoirs, with bank erosion where sediments are weakly consolidated. It also demonstrates how resumption of tidal propagation can accelerate bank erosion; a process that is closely linked to wind-driven wave energy and the establishment of a foreshore profile that is better fitted to this energy regime. This model is very important both in the context of new tidal energy barrages and also for projects to retro-fit turbines into existing causeways. It reinforces the evidence from the Eastern Schelde in The Netherlands where it has been found that reduced tidal propagation has had profound effects on foreshore evolution with serious loss of mudflats and former saltmarshes. Annapolis Royal not only highlights erosionary processes; it also provides initial indications of the timescales required for evolution of more stable inter-tidal profiles.The evidence provided by these various examples has important implications for coastal managers. Firstly, they show how analogues can be used to develop a conceptual geomorphological model of possible responses to causeways, sills and barrages such as some of the options being considered for the Thames Estuary. In addition, they highlight issues that need to be taken into account when pre-project planning considers likely issues and long-term management implications.

Estimation of annual energy output from a tidal barrage using two different methods

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.

Tidal lagoon environmental interactions: regulator perspective, solution options and industry challenges

Tidal range energy is an attractive renewable energy option, particularly in areas of high tidal range, such as the UK. Historically one of the main barriers to tidal range developments in the UK, specifically tidal barrages, has been regulatory environmental concerns and uncertainty surrounding environmental impacts. Tidal lagoons are often suggested as a means of reducing the environmental impact of barrage options. Recent developments in the lagoon sector mean it is now more important than ever to further consider the environmental impacts arising from tidal lagoons and the potential constraints these impacts may pose to the industry's future growth. Environmental impacts and their interactions are complex, often making them difficult to understand and manage. Here, the authors develop a conceptual framework to categorise impacts, present results from consultation with regulatory and policy organisations and discuss potential impact and enhancement solution options. This study includes a number of case studies to present lessons learnt, opportunities, cautions and successful implementation of past solutions. In the absence of operational tidal lagoons, these case studies are based on barrages and other relevant developments.

Renewable energy vs. biodiversity: Policy conflicts and the future of nature conservation

The European Union's (EU) network of nature conservation areas – Natura 2000 – covers almost 18% of EU territory, and is subject to strict legal protection, which is enforced by the European Commission, a supranational authority. Given the Natura 2000 network's size, conflicts between Natura 2000 and renewable energy projects are inevitable, particularly as countries push to meet their 2020 energy and emissions reduction targets by pursuing more – and larger – renewable energy projects. Focusing on two cases in the renewable energy sector – a hydroelectric dam in Portugal's Sabor valley, and a large tidal barrage in the UK's Severn estuary – this article shows that the EU's strict biodiversity protection regime could necessitate the rejection of many large renewable energy projects. That is, it may not be possible as a matter of EU law for national authorities to grant permission for such projects. The potential for such difficulties will be shown to be highly visible to policymakers, and could, this article argues, trigger negative impacts in terms of the rule of law, and negative feedbacks on nature conservation policies in the EU and, by way of precedent, globally. The legal issues presented here should not, this article argues, be regarded as insurmountable problems, nor as a trigger for reforms aimed at weakening biodiversity protections. Rather, these issues are better regarded as an opportunity for an open, informed, global debate regarding the relationship between biodiversity and climate change policies, and the hierarchy, if any, between them.

Capacity Value of Large Tidal Barrages

This paper presents the first detailed capacity value calculation for tidal barrage generation, based on modeling of operational modes for the proposed 8-GW Severn Barrage scheme in Great Britain. The key finding is that the effective load carrying capability is very low as a percentage of installed capacity (less than 10% for the example presented here). This is because of the high probability of having zero available output at time of peak demand, if peak demand occurs on the wrong part of the tidal cycle; this result may be explained transparently using a simple two-state model of the barrage. The prospects for building a probabilistic model of tidal barrage availability are also discussed.