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The tidal range energy potential of the West Coast of the United Kingdom
Abstract
With concerns mounting over the UK’s energy future and the effects of climate change, it will soon become paramount that all viable sources of renewable energy are fully exploited. This study has examined the scope for reliable and fully predictable tidal electricity generation from the conjunctive operation of 5 major estuary barrages on the West Coast of the UK in an attempt to establish the potential scale of the extractable resources. Two levels of investigation have been undertaken: simple 0-D (‘two-tank’) modelling of barrage energy generation under different operational modes, using the hydraulic characteristics of turbine performance; and 2-D modelling of tidal hydrodynamics over a wide sea area in a computational grid incorporating the barrages with turbines and sluices. It has been demonstrated that more than 33TWh per year of electricity should be attainable, from 22GW of installed capacity, this representing close to 10% of present UK demand.
... Tidal power stations have been using artificially created tidal phase differences and flowing through turbines to generate electricity for a relatively long time [6,7]. Early studies on tidal power stations focused on traditional one-way or two-way operations without a pump mode [8][9][10]. However, as tidal power stations have further developed, scholars have studied the potential energy gains that can result from the pump mode [11,12]. ...
... Water 2023, 15, x FOR PEER REVIEW 2 of 20 a pump mode [8][9][10]. However, as tidal power stations have further developed, scholars have studied the potential energy gains that can result from the pump mode [11,12]. ...
... The change in sea level in a day is roughly like a sine wave, and the tidal power station will adjust the reservoir water level to generate power according to the change in sea-water level. Most of the current units used in tidal power plants are reversible pump-turbines, which have six functions, including two-way power generation, two-way pumping, and two-way sluice, as shown in Figure 1 [9]. This helps to balance the grid and ensure a steady supply of energy. ...
The focus of this paper is to investigate how various numbers of blades impact the performance of a two-way contra-rotating axial-flow pump-turbine when operating in pump mode. In order to meet the two-way operation of the pump-turbine, the front and rear impellers are mirror-symmetric with the same hydraulic model, which ensures the consistent performance of the forward and reverse working conditions. However, when the two-stage impellers have the same number of blades, the dynamic–dynamic interference can be severe, which can threaten the stability of the unit. The present study explores the use of two-stage impellers with varying numbers of blades as a means of enhancing the performance of tidal energy units. By conducting numerical simulations on the front and rear impellers under different flow rates in pump mode, the impact of increasing the number of blades in each stage on the external characteristics of the pump-turbine is revealed. The internal flow characteristics of different models are analyzed, and the impact of the number of blades on the vortex is studied. Different blade numbers will have a certain impact on the internal flow of the two-way contra-rotating axial-flow pump–turbine. Increasing the number of blades will affect the development of tip-leakage vortices and promote their intersection with the wake. In addition, changes in the number of blades will have an impact on the location of the leading edge (LE) water impact on the rear impeller, which in turn affects the contours of vorticity of the rear impeller near the LE and the location of the suction surface (SS) flow separation. The findings of this study offer valuable insights for future research on the operation of contra-rotating axial-flow pump-turbines.
... In particular, tidal forcing at model boundary conditions is typically informed by a limited set of constituents that varies between studies (Table 1). Furthermore, simulations are typically conducted over short timeframes (i.e. in the order of weeks or months) given computational and practical constraints when running hydrodynamic models [8,9]. When using hydrodynamic modelling that introduces tangible computational constraints, these assessments tend to simulate finite periods in the order of a lunar month (i.e., ≈29.53 days [10,11]). ...
... Burrows et al. [9] considered the conjunctive operation of five major tidal barrages on the west coast of the UK. The addition of three constituents aside from the principal M 2 and S 2 (which were used in their analysis), provide noticeable changes to the energy source, indicating that these should be considered for more accurate resource assessments. ...
... where is the expected generation efficiency, is the mean annual tidal range and is a capacity factor. We set = 0.40 following the estimate of 37% by Burrows et al. [9] for two-way operation. In turn, acknowledging economic feasibility constraints we choose = 0.20, providing a break even target for the installed capacity. ...
Tides exhibit variability over time. This study proposes a methodology for selecting a representative timeframe for tidal range energy analyses, when constrained to a typical, short-term, lunar month-long period. We explore how the selection of particular timeframes skews findings of energy assessments, especially for cross-comparisons across studies. This exercise relies on metrics assessing the magnitude and variability of a tidal signal relative to longer-term nodal cycle quantities. Results based on UK tide gauges highlight that tide characteristics exhibit significant variations temporally within a lunar month. Relative to quantities of tidal elevation standard deviation or average potential energy, values can vary by 15% and 30% respectively. For each lunar month, interquartile range values for tidal height and energy can deviate by 45% from the mean. Spatially, we observe a satisfactory correlation only once sufficient constituents are considered. In that case, a representative timeframe can be identified for comparative tidal range scheme assessments within the same tidal system. In contrast, timeframes with high tidal variability distort individual project performance, particularly under fixed operation. The methodology, if integrated to marine energy resource and environmental impact assessments, would deliver marine power generation insights over a project lifetime that enable robust design comparisons across sites
... The linked-basin configuration only captures $15% of the resource . For realistic sites, relatively conservative empirical efficiency estimates for ebb and two-way generation are expected (27% and 37%, Burrows et al., 2009). Two-way generation with pumping can perform even better for small to medium sized schemes, increasing the energy output beyond 50% for idealized scenarios . ...
... Coupling operational and hydrodynamics models allows for changes to the local tidal dynamics to be fully accounted for. Hydrodynamic modelling studies highlight how 0-D models may overestimate the energy output by as much as 50% (Angeloudis and Falconer, 2017;Yates et al., 2013;Burrows et al., 2009). The level of overestimation depends on the manner in which designs interfere with established tidal dynamics. ...
... These updated the annual production to $19 TWh (Watson and Shaw, 2007). Given the wide variation and uncertainty of the predictions, hydrodynamic modelling has been applied to revise these estimates with values obtained ranging between 10.5 and 17.5 TWh (Xia et al., 2012;Burrows et al., 2009;Zhou et al., 2014a) for the Severn Barrage STPG scheme. The hydrodynamic model variations on annual energy output predictions are attributed to different simulation periods, hydrodynamic modelling assumptions and operation parametrizations. ...
Tides present enormous opportunities to serve as a source of marine renewable energy. This chapter outlines resource and exploitation considerations associated with the marine energy available in areas exhibiting a high tidal range. Initially, a brief introduction to this particular form of tidal power is presented, highlighting the characteristics of the resource and its global distribution. In turn, key elements of the technology required to harness this resource are described, demonstrating both progress made to-date and drivers towards the development of tidal range projects. An overview of existing tidal range power plants is provided as well as a summary of recent proposals for locations where the technology can be deployed. The focus then shifts towards technical constraints and feasibility challenges that must be considered, followed by the methods currently used to address these. Finally, further aspects of tidal range energy assessment are discussed by means of practical case studies.
... The eastern coast of the Irish Sea, UK, experiences some of the highest tidal ranges globally [2]. It is seen as a suitable location for the exploitation of this tidal range resource [10,11]. Nonetheless, the need to mitigate the typically high capital costs [12] whilst minimising the potentially significant environmental impact [13][14][15] has thus far hindered the commercial progress of UK-based proposals to date [1]. ...
... Most tidal power plant assessment studies assume a similarly incentivised economic model. Design optimisation typically centres on the characteristics and number of hydraulic structures (turbines, sluices, pumps), with the embankment path generally based on existing proposals and/or practical geographical limitations [10,20]. Meanwhile, the subsequent operational optimisation typically assumes an inflexible scheduling regime, where interval timings or water heads triggering operation mode transitions are fixed at all tidal cycles [21,22]. ...
... Such a system could be supplemented by other technologies, e.g., tidal stream farms, in order to generate continuously [10,21]. To the best of the authors' knowledge, investigation of the flexible operation of a fleet of tidal range power plants has yet to be conducted in terms of their combined energy output and economic characteristics. ...
The extraction of tidal energy from head differences represents a predictable and flexible option for generating electricity. Here, we investigate the generation potential of prospective tidal power plants in the UK. Originally conceived as separate projects, operating these schemes as a cooperative system could prove beneficial. Combined with the inherent operational flexibility of tidal range-based schemes, a notable tidal phase difference in selected sites allows for the system to spread power generation over a larger proportion of the day. Using depth-averaged modelling and gradient-based optimisation techniques, we explore how a flexible cumulative operation schedule could be applied to provide a degree of continuous supply if desirable. While fully continuous operation is not achieved, a number of different optimisation schedules deliver cumulative continuous supply for over half of the year. The average minimum cumulative power output on these days is consistently over 500 MW out of a total installed capacity of 6195.3 MW. Furthermore, by introducing financial incentives associated with reliable, baseload supply, we provide an economic assessment of the tidal power plant system. The daily minimum cumulative power output determines income in the modelled idealised baseload market, while excess supply is traded in an hourly variable wholesale energy market. Results indicate that subsidies would be required in order to make a pursuit of continuous generation financially advantageous over energy maximisation strategies.
... Such limitations together with advances in computational resources has driven the development of multi-dimensional (1-D, 2-D, 3-D) hydro-environmental models [11,12] coupled with operation algorithms of single-basin power plants [13][14][15][16]. In particular, these coupled modelling results highlight how 0-D models may overestimate the energy output by as much as 50% [17][18][19]. The level of overestimation depends on the way designs interfere with established tidal dynamics. ...
... • The effect of tidal amplitude (α) on extractable energy over an annual period. In principle, the potential energy available is determined from Eq. (1), with empirical efficiency estimates of 27% and 37% for ebb and two-way respectively, as per [19]. However, more recent optimisation studies suggest that these percentages can vary [14]. ...
... Firstly, predictions of normalised energy outputs for single-basin plants using fixed-control configurations (SB-EBB-C, SB-TW-C) are aligned with previous studies. For example, the [19] estimates of 27% and 37% for ebb-only and two-way generation are close to our predictions of 29.8% and 36.9% respectively. ...
Single-basin tidal range power plants have the advantage of predictable energy outputs, but feature non-generation periods in every tidal cycle. Linked-basin tidal power systems can reduce this variability and consistently generate power. However, as a concept the latter are under-studied with limited information on their performance relative to single-basin designs. In addressing this, we outline the basic principles of linked-basin power plant operation and report results from their numerical simulation. Tidal range energy operational models are applied to gauge their capabilities relative to conventional, single-basin tidal power plants. A coastal ocean model (Thetis) is then refined with linked-basin modelling capabilities. Simulations demonstrate that linked-basin systems can reduce non-generation periods at the expense of the extractable energy output relative to conventional tidal lagoons and barrages. As an example, a hypothetical case is considered for a site in the Severn Estuary, UK. The linked-basin system is seen to generate energy 80–100% of the time over a spring-neap cycle, but harnesses at best ≈ 30% of the energy of an equivalent-area single-basin design.
... Such limitations together with advances in computational resources has driven the development of multi-dimensional (1-D, 2-D, 3-D) hydro-environmental models [11,12] coupled with operation algorithms of single-basin power plants [13,14,15,16]. In particular, these coupled 30 modelling results highlight how 0-D models may overestimate the energy output by as much as 50% [17,18,19]. The level of overestimation depends on the way designs interfere with established tidal dynamics. ...
... • The effect of tidal amplitude (α) on extractable energy over an annual period. In principle, the potential energy available is determined from Eq. (1), with empirical efficiency estimates of 27% and 37% for ebb and two-way respectively, as per Burrows et al. [19]. However, more recent 240 optimisation studies suggest that these percentages can vary [14]. ...
... Firstly, predictions of normalised energy outputs for single-basin plants using fixed-385 control configurations (SB-EBB-C, SB-TW-C) are aligned with previous studies. For example, the Burrows et al. [19] estimates of 27% and 37% for ebb-only and two-way generation are close to our predictions of 29.8% and 36.9% respectively. ...
Single-basin tidal range power plants have the advantage of predictable energy outputs, but feature non-generation periods in every tidal cycle to facilitate the essential turbine driving head difference. Linked-basin tidal power systems can reduce this variability and consistently generate power. However, as a concept the latter are under-studied with research and information on their potential performance relative to single-basin designs being limited. In an effort to address this, we outline the basic principles of linked-basin power plant operation and report results from their numerical simulation. Lagoon operational models are applied to gauge their capabilities relative to conventional, single-basin tidal power systems. A coastal ocean model (Thetis) has in turn been equipped with linked-basin modelling capabilities in addition to single-basin tidal power plant operation strategies. Simulations demonstrate that deployment of linked-basin systems can lead to non-generation times being substantially reduced at the expense of the overall energy output relative to conventional tidal lagoons and barrages. As an example, a hypothetical case is considered for a site in the Severn Estuary, UK. A linked-basin system is shown to be able to generate energy 80--100\% of the time over a spring-neap cycle, but harnesses ~30% of the energy of an equivalent-area single-basin design.
... In Europe, the UK possesses the largest resource with around 44-50 TWh/a, which amounts to about half the total European potential [8]. If the major tidal sites at the coasts of the UK are realized, up to 6 GW of tidal power could be generated during spring tides, resulting in an annual energy output of around 30 TWh/a [17]. ...
... In a case study at Morecambe Bay, England it was confirmed that energy gains from pumping are proportionally higher when the turbine number increases. With a pumping efficiency of only 40 % "...the net annual energy gains were found to be approximately 7 %, 13 % and 1 % for ebb, flood and dual modes, respectively" [17]. ...
... These projects would not only be interesting on their own, but the combination and conjunctive operation of the multiple sites could have the benefit of creating a longer generation window from tidal power, as the tidal cycles along the coast are phase shifted in time. This idea is proposed by [17] as a case study, where five tidal barrages, located at the Solway Firth, the Morecambe Bay, and the Mersey, Dee, and Severn estuaries are combined. In total, this scheme with an installed capacity of 21 GW could produce 33 TWh of electrical energy per year, which is at least 10 % of the annual electricity demand of the United Kingdom. ...
The present study describes the development of an axial water turbine with ring generator
for use in tidal range power plants. The turbine’s very compact design makes it
possible to integrate all components into a reversible cylinder. Thus, the turbine can
be optimized for one flow direction and by reversing the cylinder identical operating
characteristics such as efficiency and unit discharge can be achieved in the opposite
flow direction. As the turbine can be used also as a pump, it achieves an efficient
four-quadrant operation, which can increase the energy output of tidal power schemes
that are designed for a two-way operation with pumping.
This thesis gives an overview of the tidal range technology, its history, and state of
the art. The new turbine concept is described in detail and the identified development
targets are defined. A literature study gives insight into how much the new concept
could increase the energy production of tidal power plants. Following this, the basis for
the initial design is illustrated and the subsequent optimization process is described,
which is based on three-dimensional computational fluid dynamics simulations with
the software ANSYS CFX.
The operating characteristics of the final geometry are simulated over a wide range
of unit speeds and unit discharges in both the turbine and pumping mode. The results
show that the turbine concept is feasible and can achieve good operating conditions.
However, the unusual concept brings with it some special requirements that lead to
some restrictions. In particular the axial arrangement of the components induces a
swirl distribution ahead of the runner that can only be mitigated by specially designed
guide vanes.
... The efficiency of tidal power plants in harnessing the available potential energy during a given tidal cycle is heavily dependent on the control of the constituent hydraulic structures [16,17,18,15,19]. A generalised illustration of how a plant can be regulated is presented in Fig. 1, with t i , i = 1, . . . ...
... Similar expressions are imposed when closing the hydraulic structures. The flow through turbine caissons is not reliably calculated using (3) as found previously [18]. Instead hill chart parametrisations are preferable whilst power is generated to reflect the installed turbine characteristics [20]. ...
... The simulation of the tidal power plant performance can be accomplished in several ways [18,22,23]. Essentially, the problem is split into downstream and upstream sub-domains connected at the hydraulic structure location. ...
Tidal range power plants represent an attractive approach for the large-scale generation of electricity from the marine environment. Even though the tides and by extension the available energy resource are predictable, they are also variable in time. This variability poses a challenge regarding the optimal transient control of power plants. Here we consider simulation methods which include the main modes of operation of tidal power plants, along with algorithms to regulate the timing of these.This paper proposes a framework where simplified power plant operation models are coupled with gradient-based optimisation techniques to determine the optimal control strategy over multiple tidal cycles. The optimisation results in turn inform coastal ocean simulations that include tidal power plants to gauge whether the benefits of an adaptive operation are preserved once their hydrodynamic impacts are also taken into consideration. The combined operation of two prospective tidal lagoon projects within the Bristol Channel and the Severn Estuary is used as an example to demonstrate the potential benefits of an energy maximisation optimisation approach.For the case studies considered, the inclusion of pumping and an adaptive operation is shown to deliver an overall increase in energy output of 20-40 % compared to a conventional two-way uniform operation. The findings also demonstrate that smaller schemes stand to gain more from operational optimisation compared to designs of a larger scale.
... The operation can be modelled using a water level time series as input, governed by the transient downstream water elevations at the site location ( Fig. 1). This is known as 0D modelling, and has been deemed sufficient under certain conditions, e.g. for smaller lagoons and barrages, as explored in the literature [28,34,35,38]. ...
... Refs. [27,34,39]. However, one commonly used technique is the backward-difference numerical model, developed according to the continuity equation. ...
... Refs. [28,30,34,35]. ...
Tidal energy is one of the most predictable forms of renewable energy. Although there has been much commercial and R&D progress in tidal stream energy, tidal range is a more mature technology, with tidal range power plants having a history that extends back over 50 years. With the 2017 publication of the "Hendry Review" that examined the feasibility of tidal lagoon power plants in the UK, it is timely to review tidal range power plants. Here, we explain the main principles of tidal range power plants, and review two main research areas: the present and future tidal range resource, and the optimization of tidal range power plants. We also discuss how variability in the electricity generated from tidal range power plants could be partially offset by the development of multiple power plants (e.g. lagoons) that are complementary in phase, and by the provision of energy storage. Finally, we discuss the implications of the Hendry Review, and what this means for the future of tidal range power plants in the UK and internationally.
... The operation can be modelled using a water level time series as input, governed by the transient downstream water elevations at the site location ( Fig. 1). This is known as 0D modelling, and has been deemed sufficient under certain conditions, e.g. for smaller lagoons and barrages, as explored in the literature [28,34,35,38]. ...
... Refs. [27,34,39]. However, one commonly used technique is the backward-difference numerical model, developed according to the continuity equation. ...
... Refs. [28,30,34,35]. ...
Tidal energy is one of the most predictable forms of renewable energy. Although there has been much commercial and R&D progress in tidal stream energy, tidal range is a more mature technology, with tidal range power plants having a history that extends back over 50 years. With the 2017 publication of the "Hendry Review" that examined the feasibility of tidal lagoon power plants in the UK, it is timely to review tidal range power plants. Here, we explain the main principles of tidal range power plants, and review two main research areas: the present and future tidal range resource, and the optimization of tidal range power plants. We also discuss how variability in the electricity generated from tidal range power plants could be partially offset by the development of multiple power plants (e.g. lagoons) that are complementary in phase, and by the provision of energy storage. Finally, we discuss the implications of the Hendry Review, and what this means for the future of tidal range power plants in the UK and internationally.
... Previous studies of tidal range power, including Prandle [8], Wolf et al. [5], Burrows et al. [9], Xia et al. [10,11], Falconer et al. [12], Cornett et al. [13], generally focused on: (a) conventional ebb-only/flood-only generation or twoway operation without pumping options; and (b) assumed that the operation remained uniform over varying tidal conditions. Very little has been reported in terms of optimisation; the study of Aggidis and Benzon [6] considered that the optimum head difference might vary subject to the tidal range present in an ebb-only strategy, which effectively corresponds to a single-variable optimisation problem. ...
... The total amount of energy resource that can be extracted from a tidal power plant in each tidal cycle is related to (a) turbine technology capabilities, (b) the spring-neap (and longer period) tidal variations at the site and (c) the design of the structure and its interaction with local hydrodynamics. The efficiency of tidal power plants in harnessing the available potential energy during a given tidal cycle is heavily dependent on the control of the constituent hydraulic structures [10,20,9,8,21]. A generalised illustration of how a plant can be regulated is presented in Fig. 1, with t i , i = 1, . . . , n forming the main control variables. ...
... For regional and far-field scale coastal ocean models a sensitivity test to the parameter C d can be found in Bray et al. [24]. Nonetheless, a value of unity is normally selected within regional scale models [9,13] and this practice has been adopted here. A sinusoidal ramp function taking the values r(t) = sin(π/2 × (t − t m )/t r ) for t ∈ [t m , t m + t r ], and unity otherwise, is employed here to represent the transition at the beginning of a mode where t r is the interval expected when opening hydraulic structures and t m the time when the current mode was triggered. ...
Tidal range power plants represent an attractive approach for the large-scale generation of electricity from the marine environment. Even though the tides and by extension the available energy resource are predictable, they are also variable in time. This variability poses a challenge regarding the optimal transient control of power plants. Here we consider simulation methods which include the main modes of operation of tidal power plants, along with algorithms to regulate the timing of these. This paper proposes a framework where simplified power plant operation models are coupled with gradient-based optimisation techniques to determine the optimal control strategy over multiple tidal cycles. The optimisation results in turn inform coastal ocean simulations that include tidal power plants to gauge whether the benefits of an adaptive operation are preserved once their hydrodynamic impacts are also taken into consideration. The combined operation of two prospective tidal lagoon projects within the Bristol Channel and the Severn Estuary is used as an example to demonstrate the potential benefits of an energy maximisation optimisation approach.For the case studies considered, the inclusion of pumping and an adaptive operation is shown to deliver an overall increase in energy output of 20-40 % compared to a conventional two-way uniform operation. The findings also demonstrate that smaller schemes stand to gain more from operational optimisation compared to designs of a larger scale.
... In particular, tidal power stations have a relatively long history of using artificially created tidal phase differences and flowing through turbines to generate energy in the form of electricity (Neill et al. 2018;Angeloudis and Falconer 2017). Early tidal studies have concentrated on traditional one-way or two-way operation but without the option of pumping (Prandle 1984;Burrows et al. 2009;Xia et al. 2010). With the further development of tidal power stations, several scholars have studied energy gains that can result from pumping conditions (Mackay and Hafemeister 2010;Yates et al. 2013). ...
... From an economic point of view, it can pump water at low price times to store energy for use at high prices (Harcourt et al. 2019). Therefore, current units used in tidal power plants are mostly reversible pump-turbines, which have six functions of two-way power generation, two-way pumping, and two-way sluice, as shown in Fig. 1 (Burrows et al. 2009). ...
This paper investigated the variable speed operation of a two-way contra-rotating axial flow pump–turbine in pump mode. When counter-rotating impellers operate at the same speed, a significant difference exists in the shaft power of the two impellers, thereby causing difficulties in motor selection. However, the same motor is required for both impellers in two-way pump–turbines. To solve this problem, this paper aims to determine the appropriate speed at which the two impellers operate with a similar shaft power. Accordingly, improving the performance of the tidal unit while enabling the basic functions of the pump–turbine is of considerable engineering and academic significance. An analysis of performance variations of the front and rear impellers in the pump mode reveals the law of power variation for each impeller at different speeds of the rear impeller. Under different flow conditions, shaft power of the rear impeller is found to be at least 31% higher compared with that of the front impeller. This result provides practical reference for further research on the operation of counter-rotating axial flow pump–turbine.
... There have been many investigations around the tidal range generation. There are studies on the tidal range resources, such as the approximation of extractable tidal energy around the Great Britain coastline [6] or from a single tidal range proposal [7]. The impacts of tidal range generation have been evaluated, including the hydrodynamic interference [8], the effect on nature conservation [9], the eutrophication risk [10]. ...
... The 0-D models have been found to produce higher yield estimates than 2-D models (by up to 12% in the case of [19]), however the relative reduction in computational cost has been accepted to outweigh this deviation, leading to the use of 0-D becoming standard. In this model, the hydrodynamics of a TRPS is represented by a 0-D model [6]. The relationship between hydraulics and generation is described by the equations below. ...
With the global trend to exploit more renewable energy sources, tidal range energy has been gaining more attention recently. This power generation technology is expected to reduce the share of fossil fuels and provide flexibility to the power system. With a pioneering tidal range generation project just granted in Wales and more proposals planned in Great Britain, it is important to study how the incorporation of multiple tidal range power stations will affect power system operation. In this paper, the role of tidal range energy generation in the future Great Britain power system is investigated based on a day-ahead scheduling model of power system incorporating multiple tidal range power stations. In the proposed model, tidal range power stations situated at different sites operate flexibly and in coordination, supporting the power system to reach the minimum operating cost. A case study based on the Great Britain electricity transmission system in 2030 with one tidal barrage and one tidal lagoon was investigated. The results showed that the coordination of flexible tidal range power stations can reduce the power system's operating cost. Furthermore, the energy-storage feature of tidal range power stations can act as a stable source of flexibility in the power system.
... Over a single tidal cycle therefore here there are at least eight operational parameters that could be optimized. global blockage problem is an all-encompassing aspect that needs to be addressed in terms of impacts and regional scale changes to tidal dynamics Burrows et al., 2009a;Yates et al., 2013a;Ahmadian et al., 2014;Xia et al., 2010b,c). For lagoons, similar competition and cumulative impact effects as for arrays need to be considered (Angeloudis and Falconer, 2017;Mackie et al., 2020). ...
... The operational performance of a tidal range power plant depends intimately on how the hydraulic structures are controlled in light of the tidal elevation either side of the impoundment (Xia et al., 2010a;Angeloudis et al., 2016;Burrows et al., 2009b;Prandle, 1984;Baker, 1987). Angeloudis et al. (2018) consider the modes of operation portrayed in Fig. 3. ...
Optimizing marine renewable energy systems to maximize performance is key to their success. However, a range of physical, environmental, engineering, economic as well as computational challenges means that this is not straightforward. This article considers this topic, focusing on those systems whose performance is coupled to the hydrodynamics providing the resource; tidal power represents a clear example of this. In such cases system design must be optimal in relation to the resource's magnitude as well as its spatial and temporal variation, which are all dependent on the system's configuration and operation and so cannot be assumed to be known at the design stage.
Designing based on the ambient resource could lead to under-performance. Coupling between the design and the resource has implications for the complexity of the optimization problem and potential hydrodynamical and environmental impacts. This coupling distinguishes many marine energy systems from other renewables which do not impact in any significant manner on the resource. The optimal design of marine energy systems thus represents a challenging and somewhat unique problem. However, feedback also opens up a number of possibilities where the resource can be ‘controlled’, to maximize the cumulative power obtained from multiple devices or plants, or to achieve some other complementary goal.
Design optimization is thus critical, with many issues to consider. Due to the complexity of the problem a computational based solution is a necessity in all but the simplest scenarios. However, the coupled feedback requires that an iterative solution approach be used, which combined while the vast range of spatial and temporal scales means that methodological compromises need to be made. These compromises need to be understood, with the correct computational tool used at the appropriate point in the design process. This article reviews these challenges as well as the progress that has been made in addressing them.
... Tidal range energy represents a vast and unexploited worldwide resource. The UK has the potential to generate large amounts of renewable energy from the tidal range (Burrows et al., 2009), with a theoretical estimate in the region of 120 TWh/year (The Crown Estate, 2012). However, within the UK there are as yet no attempts to exploit the UK's large tidal range resource with tidal barrages. ...
... There have been a number of studies assessing the potential energy generation from a tidal barrage on the Mersey estuary using a variety of different models, barrage parameters and operational modes. The Department of Energy carried out a study in 1984 (Department of Energy and UKAEA, 1984), followed by Mersey Barrage Company in 1992 (Mersey Barrage Corporation, 1992), the "Joule" Project by the University of Liverpool and Proudman Oceanographic Laboratories in 2009 (Burrows et al., 2009) and the Peel Energy Limited and Northwest Regional Development Agency feasibility study in 2011 (Libaux, 2011). A recent study at Lancaster University (Aggidis and Benzon, 2013) reviewed the predicted energy outputs of the studies described in Table 2 using the latest double regulated turbine technology from Andritz Hydro (Aggidis and Feather, 2012) and improved bathymetric data. ...
Currently there is renewed interest in harnessing the vast tidal resource to combat the twin challenges of climate change and energy security. However, within the UK no tidal barrage proposals have passed the development stage, this is due to a combination of high cost and environmental concerns. This paper demonstrates how a framework, such as the North West Hydro Resource Model can be applied to tidal barrages, with the Mersey barrage as a case study. The model materialised in order to provide developers with a tool to successfully identify the capacity of hydropower schemes in a specific location. A key feature of the resource model is the understanding that there is no single barrier to the utilisation of small hydropower but several obstacles, which together impede development. Thus, this paper contributes in part to a fully holistic treatment of tidal barrages, recognising that apart from energy generation , other environmental, societal and economic opportunities arise and must be fully investigated for robust decision-making. This study demonstrates how considering the societal needs of the people and the necessity for compensatory habitats, for example, an organic architectural design has developed, which aims to enhance rather than detract from the Mer-sey.
... In practice, the extractable energy from a tidal power plant in each tidal cycle is additionally related to (a) the installed turbine technology capabilities, (b) the spring-neap (and longer period) tidal and plan surface area variations at the site and (c) the design of the structure and its interaction with local and far-field hydrodynamics. The efficiency of tidal power plants in harnessing the available potential energy during a given tidal cycle is heavily dependent on the control of the constituent hydraulic structures [14,15]. A generalised illustration of how a plant can be regulated is presented in Fig. 1 , are the main control variables that essentially dictate the operation strategy for a given cycle i. ...
... There is potential to re-evaluate the role multiple tidal range projects operating flexibly could play in the UK electricity system. A previous study indicated base-load power was not achievable given the tidal phasing of potential projects in the UK [14]. However, by utilising flexible operation this might be possible. ...
Tidal range renewable power plants have the capacity to deliver predictable energy to the electricity grid, subject to the known variability of the tides. Tidal power plants inherently feature advantages that characterise hydro-power more generally, including a lifetime exceeding alternative renewable energy technologies and relatively low Operation & Maintenance costs. Nevertheless, the technology is typically inhibited by the significant upfront investment associated with capital costs. A key aspect that makes the technology stand out relative to other renewable options is the partial flexibility it possesses over the timing of power generation. In this study we provide details on a design methodology targeted at the optimisation of the temporal operation of a tidal range energy structure, specifically the Swansea Bay tidal lagoon that has been proposed within the Bristol Channel, UK. Apart from concentrating on the classical incentive of maximising energy, we formulate an objective functional in a manner that promotes the maximisation of income for the scheme from the Day-Ahead energy market. Simulation results demonstrate that there are opportunities to exploit the predictability of the tides and flexibility over the precise timing of power generation to incur a noticeable reduction in the subsidy costs that are often negotiated with regulators and governments. Additionally, we suggest that this approach should enable tidal range energy to play a more active role in ensuring security of supply in the UK. This is accentuated by the income-based optimisation controls that deliver on average more power over periods when demand is higher. For the Swansea Bay tidal lagoon case study a 23% increase is observed in the income obtained following the optimisation of its operation compared to a non-adaptive operation. Similarly, a 10% increase relative to an energy-maximisation approach over a year's operation suggests that simply maximising energy generation in a setting where power prices vary may not be an optimal strategy.
... The efficiency of tidal power plants in harnessing the available potential energy during a given tidal cycle is heavily dependent on the control of the constituent hydraulic structures [14,15]. A generalised illustration of how a plant can be regulated is presented in Fig. 1, where t p,e , t g,e , t h,e , t p,f , t g,f , t h,f are the main control variables that essentially dictate the operation strategy for a given tidal cycle i. ...
... There is potential to re-evaluate the role multiple tidal range projects operating flexibly could play in the UK electricity system. A previous study indicated base-load power was not achievable given the tidal phasing of potential projects in the UK [14]. However, by utilising flexible operation this might be possible. ...
Tidal range renewable power plants have the capacity to deliver predictable energy to the electricity grid, subject to the known variability of the tides. Tidal power plants inherently feature advantages that characterise hydro-power more generally, including a lifetime exceeding alternative renewable energy technologies and relatively low Operation & Maintenance costs. Nevertheless, the technology is typically inhibited by the significant upfront investment associated with capital costs. A key aspect that makes the technology stand out relative to other renewable options is the partial flexibility it possesses over the timing of power generation. In this study we provide details on a design methodology targeted at the optimisation of the temporal operation of a tidal range energy structure, specifically the Swansea Bay tidal lagoon that has been proposed within the Bristol Channel, UK. Apart from concentrating on the classical incentive of maximising energy, we formulate an objective functional in a manner that promotes the maximisation of income for the scheme from the Day-Ahead energy market. Simulation results demonstrate that there are opportunities to exploit the predictability of the tides and flexibility over the precise timing of power generation to incur a noticeable reduction in the subsidy costs that are often negotiated with regulators and governments. Additionally, we suggest that this approach should enable tidal range energy to play a more active role in ensuring security of supply in the UK. This is accentuated by the income-based optimisation controls that deliver on average more power over periods when demand is higher. For the Swansea Bay tidal lagoon case study a 23% increase is observed in the income obtained following the optimisation of its operation compared to a non-adaptive operation. Similarly, a 10% increase relative to an energy-maximisation approach over a year's operation suggests that simply maximising energy generation in a setting where power prices vary may not be an optimal strategy.
... turbines and sluice gates), it is possible to simulate the performance of a tidal range structure [11], [12]. The plant operation can be modelled using a water level time series representing the transient downstream water elevations at the site location [3], [13], [14]. In the classical study of [9], it was assumed that (i) the flow through the turbines is at a constant flow rate Q and that (ii) power generation starts and stops at the same prescribed minimum head h min . ...
... In the classical study of [9], it was assumed that (i) the flow through the turbines is at a constant flow rate Q and that (ii) power generation starts and stops at the same prescribed minimum head h min . Since then, developments in 0-D modelling for tidal range structures have been presented by [11], [13]- [15] so that: ...
Tidal range energy projects present an attractive means for the predictable and large-scale generation of electricity from the marine environment. In particular, proposals are under consideration in UK waters, with their feasibility currently being under high levels of scrutiny. This is due to a combination of potential environmental and socio-economic impacts that are challenging to quantify in the absence of a standardised methodology. At present, numerical models are being developed to provide robust resource/impact assessments and inform future designs. However, modelling inconsistencies in the representation of tidal power plants, operational algorithms, and turbine technology parameters can be observed in the studies to-date. This has made comparisons between proposed designs difficult to accomplish and rely upon. We present a series of models that progressively and consistently introduce spatial dimensions in resource prediction applications. The capabilities and limitations of each of these models are discussed with regard to the evaluation of energy resource and potential hydrodynamic impacts of tidal power plant proposals. Results highlight that a range of hydrodynamic scales should be considered, employing updated parametric models relating to the turbine technology capabilities. These steps will inform optimisation analyses and the robustness of tidal power plant proposals.
... turbines and sluice gates), it is possible to simulate the performance of a tidal range structure [11], [12]. The plant operation can be modelled using a water level time series representing the transient downstream water elevations at the site location [3], [13], [14]. In the classical study of [9], it was assumed that (i) the flow through the turbines is at a constant flow rate Q and that (ii) power generation starts and stops at the same prescribed minimum head h min . ...
... In the classical study of [9], it was assumed that (i) the flow through the turbines is at a constant flow rate Q and that (ii) power generation starts and stops at the same prescribed minimum head h min . Since then, developments in 0-D modelling for tidal range structures have been presented by [11], [13]- [15] so that: ...
Tidal range energy projects present an attractive means for the predictable and large-scale generation of electricity from the marine environment. In particular, proposals are under consideration in UK waters, with their feasibility currently being under high levels of scrutiny. This is due to a combination of potential environmental and socioeconomic impacts that are challenging to quantify in the absence of a standardised methodology. At present, numerical models are being developed to provide robust resource/impact assessments and inform future designs. However, modelling inconsistencies in the representation of tidal power plants, operational algorithms, and turbine technology parameters can be observed in the studies to-date. This has made comparisons between proposed designs difficult to accomplish and rely upon. We present a series of models that progressively and consistently introduce spatial dimensions in resource prediction applications. The capabilities and limitations of each of these models are discussed with regard to the evaluation of energy resource and potential hydrodynamic impacts of tidal power plant proposals. Results highlight that a range of hydrodynamic scales should be considered, employing updated parametric models relating to the turbine technology capabilities. These steps will inform optimisation analyses and the robustness of tidal power plant proposals.
... Climate change targets require the UK's carbon-free electricity production capacity to increase from 42% (in 2022) to 100% by 2035 [13], therefore TRS proposals have received a renewed surge of attention from industry [14], academia and government [15,16]. It is estimated that, a fleet of TRSs could supply 10% of the UK's annual electricity demand (based on 22 GW of installed capacity supplying 33 TWh per year, see Ref. [17]). However, despite the general success of tidal range projects abroad (e.g. the La Rance Tidal Power Station in France was commissioned in 1966 [18]), the UK is yet to deploy any form of TRS. ...
... Zerodimensional modeling is a parameterized numerical method that requires a few input data for simulating the overall performance of a tidal range plant, i.e., the known tidal conditions, the plan operation sequence, and the formulae representing the hydraulic structures [19]. Several applications of 0D modeling in small lagoons and barrages have been found in recent research [20][21][22][23]. One-dimensional modeling vertically and horizontally integrates the flow in an estuary, which eases the simulation of tidal lagoons and barrages and their effects on the hydrodynamics [21]. ...
Recent research revealed the potential of tidal energy in the central coastal region of the Colombian Pacific. Buenaventura City, located in the Valle del Cauca department in Colombia, has an important opportunity to develop tidal power technologies near its marine coastal areas. This research implemented a 3D hydrodynamic model for simulating the hydrodynamics of the Buenaventura Bay to provide data as input for evaluating the hydraulics of a tidal barrage without sluicing through CFD modeling. According to the results, the velocities across the gates during Syzygy (April 2021) showed impressive velocities between 9 and 11 m/s, which suggest a high possibility of producing electricity through tidal turbines. The mean behavior of velocities in the gates pointed to values of 3 and 5 m/s in most of the cases. The results during the Stoa condition were interesting because flow velocities higher than 1 m/s were not expected. This is promising because the plant might produce electricity even during the Stoa condition. For the first time, the results of this research suggest that there exists a high possibility of implementing tidal barrage plants in Buenaventura City, Colombia.
... Fig. 10. Example of a Hill chart for a bulb turbine [73]. ...
Tidal barrage power plants utilise the tidal range variation to generate clean electricity. Although there are several operating tidal barrage schemes around the globe, there is still potential to expand the installed capacity. Given their inherent storage and the high predictability of the tides, tidal barrages can be operated with more flexibility than many other renewables. This means that the control objective of a barrage operation can vary from energy maximisation to constant power output, or demand-matching objectives. The operation of a barrage also influences its impact on the environment and economic activity of the site where it is located, which is a major cause for the slow deployment of such power plants. The aim of this study is to provide a comprehensive and critical analysis of the different strategies considered to date to optimise the operation of tidal barrages, with a focus on an in-depth analysis of the optimisation schemes employed, the barrage models utilised, and opportunities for further improvement.
... Fig. 10. Example of a Hill chart for a bulb turbine [73]. ...
Tidal barrage power plants utilise the tidal range variation to generate clean electricity. Although there are several operating tidal barrage schemes around the globe, there is still potential to expand the installed capacity. Given their inherent storage and the high predictability of the tides, tidal barrages can be operated with more flexibility than many other renewables. This means that the control objective of a barrage operation can vary from energy maximisation to constant power output, or demand-matching objectives. The operation of a barrage also influences its impact on the environment and economic activity of the site where it is located, which is a major cause for the slow deployment of such power plants. The aim of this study is to provide a comprehensive and critical analysis of the different strategies considered to date to optimise the operation of tidal barrages, with a focus on an in-depth analysis of the optimisation schemes employed, the barrage models utilised, and opportunities for further improvement.
... Spring tides also generate significantly more power due to their higher head. High tides occur at different times of day in different locations around GB; a chain of carefully selected sites could produce some measure of continuous daily generation [4]. For today's electricity demand profile, and, without efficient storage, conventional wisdom prescribes that generation should match demand. ...
The potential power from coastal tidal range is becoming better appreciated due to the need to mitigate global warming. Great Britain (GB) is ideally situated to exploit tidal power but currently has no operational systems. Historically, estuaries have been proposed as sites for barrages, but more recently coastal lagoons are favoured due to a lower environment impact. To contrast the differences between barrages and lagoons two potential schemes are analysed using the Lancaster 0-D Tidal Range Model. Both schemes were analysed with a range of turbine numbers and generator ratings. The schemes are compared in terms of energy generation, flood protection, navigation, and selected environmental impacts.
The analysis indicates that the schemes are not categorically different, characterised by the shape and alignment of the impoundment. Barrages impoundments across estuaries are generally shorter than lagoons impounding similar volumes, with lower civil engineering costs. Whilst estuaries tend to have slightly higher tidal ranges, they also create unique ecological conditions with diverse natural ecosystems that are increasingly valued. The analysis shows that 2-way generation and pumping can match the full tidal range and help preserve inter-tidal areas.
... The constraints at time t are formulated based on a 0-D representation of a tidal lagoon [9] as below: when water enters the lagoon, these variables stay negative. ...
As the demand for electricity and the need for power systems flexibility grow, it is crucial to exploit more reliable and clean sources of energy to produce electricity when needed most. Tidal lagoons generate renewable electricity by creating an artificial head difference between water levels on the seaside, driven by tides, and water levels inside the basin, controlled by flow through the structure. Depending on the level of seawater, power generation from a tidal lagoon can be controlled, i.e. shifting power generation in time. This paper aims to investigate the operation of a tidal lagoon in response to fluctuating electricity prices. By developing an optimal operation model of a tidal lagoon, its schedule in the day-ahead wholesale electricity market was optimized to achieve maximum revenue. The Swansea Bay tidal lagoon was used as a case study. It was demonstrated that by exploiting the flexibility offered by the tidal lagoon, it can achieve a higher revenue in the day-ahead market, although their total electricity generation is reduced.
... Mesh size increases gradually towards the open boundaries to a resolution of 1600 m. The bathymetry of the model is extracted from a previous model that covers the West Coast of the United Kingdom [29]. Fig. 3 demonstrates the bathymetry of the model with locations of tidal level, tidal current, surface wave and sediment concentration validation datasets imposed. ...
This research aims to implement a three-dimensional regional scale numerical model within a region of the Irish Sea (between 52.808˚N and 53.842˚N) that is suitable for turbine array implementation and impact assessment. This research is based on a three-dimensional wave-current-sediment fully coupled oceanographic model (FVCOM), and modifications made by the authors to the current, turbulence and surface wave modules to simulate the potential impact of tidal turbines. The baseline model, i.e. without turbine implementation, is validated extensively against water level measurements at two tide gauges, tidal current data collected at four locations, and wave climate collected by a WaveNet bouy. In the case study, 18 turbines of 15-20 m diameter are modelled individually in the waterway between Anglesey and the Skerries. Results reveal the potential effects of the turbine farm on flow field, turbulence kinetic energy (TKE), bed shear stress and surface waves. Defining the wake edge as flow recovery to 95% of the baseline case, there are slight wake effects for a distance of around 14 times the array width downstream of the device farm. As a result of the high spatial resolution used, local effects of the turbine farm are revealed by the model, such as flow acceleration on both sides of the turbine farm, flow acceleration near the bed in the vicinity of the turbine farm which leads to enhanced bed shear stress, and locally increased TKE.
... Por outro lado, quando a Lua é Quarto Crescente ou Quarto Minguante as forças gravitacionais se subtraem com a do Sol, ocorrendo assim marés de amplitudes menores, chamadas marés de quadratura (GODEFROID et al., 2018). Para a geração de energia maremotriz é necessário a construção de uma barragem em um estuário, provocando um desnível entre o mar e o reservatório, na qual a energia potencial contida nas marés pode ser convertida em energia elétrica por meio de turbinas hidráulicas (CHAINEUX et al., 2008;BURROWS et al., 2009). Segundo Kadiri et al. (2012), a potência de energia que pode ser extraída de um estuário é definida como: P α AH 2 , onde P é o potencial energético de geração, A é a área do reservatório e H é o desnível de maré. ...
A exploração de energia dos recursos naturais é inevitável, seja ela de uma fonte renovável ou não renovável. Sugere-se, claro, sempre a escolha de fontes de energias renováveis, já que se trata de uma fonte com baixa emissão de CO2, que não depende de combustíveis fósseis e possui baixo impacto ambiental. Neste cenário, a energia maremotriz vem se mostrando como uma fonte de energia promissora, e por este motivo, está sendo alvo de várias pesquisas nos últimos anos. Assim, este trabalho teve por objetivo de realizar a estimativa do potencial de energético das marés em áreas costeiras do Estado do Pará a fim de auxiliar no diagnóstico técnico para projetos de geração de energia elétrica de forma sustentável. Primeiramente foram selecionados os locais com as estações maregráficas disponíveis e que apresentaram viabilidade técnica para geração da energia maremotriz. Após a seleção dos respectivos locais realizou-se a simulação das alturas de marés para então poder estimar o potencial energético dos estuários. Com relação as alturas e amplitudes das marés analisadas, as menores foram nas estações Porto de Belém, Vila do Conde e Cabo Maguari. Já na análise dos dados de maré, de maneira geral, a estação com maior dispersão nos dados foi a Fundeadouro de Salinópolis, o que demostra que estudos das energias de maré para a região merecem maior cautela. Observando as curvas de permanência de maré, as estações que mais se destacaram foram a Ilha dos Guarás, Fundeadouro de Salinópolis e Caeté, apresentando um maior potencial para aproveitamento deste tipo. Também foi possível verificar que a geração anual de energia (mesmo em baixa operação) demonstra que esta fonte de energia é firme e estratégica para suprir a demanda de energia a longo prazo.
... The objective of this study is to prepare a flexible but stable model/procedure that will be used for the tidal energy analysis in the Severn Estuary by the Hydro-environmental Research Centre (HRC) at Cardiff University. To date much of the hydrodynamic analysis of tidal range structures in the estuary focused on the Severn Barrage proposal (to mention just a few Burrows et al., 2009;Lin et al., 2010;Xia et al., 2010, Bray et al., 2016, Angelouduis and Falconer, 2016. The calculations herein were performed with the Delft3d software suite. ...
With the increasing awareness about climate change and rising prices of fossil fuels the demand for renewable energy is rapidly growing and so is the popularity of tidal energy production. To date only a few small scale tidal power plants are in operation, however this is about to change. The number of studies on this topic is fast increasing. Severn Estuary is one of the most talked about sites when it comes to tidal range power production as it has one of the largest tidal ranges in the world. The Hydro-environmental Research Centre at Cardiff University has a rich legacy of research on the topic. In this paper the Delft3D software was used to develop a hydraulic model that will be used for future studies of tidal range structures at the department. The model was validated against observation data and compared to results from the literature. The Delft3D code had to be modified to accurately represent turbines and sluice gates. Simulations were performed both in 2D and 3D.
... These results are superior to empirical thresholds suggested previously (e.g. 36% for a conventional two-way operation from Burrows et al. (2009) and Prandle (1984) as the pumping opportunities and adaptive operation mechanisms were not considered). It should be remarked that these percentages take into account the energy invested for pumping periods during the annual operation simulation of the designs. ...
The construction and operation of tidal range structures has been in the spotlight since the UK Government-commissioned Hendry Review, published in early 2017, advised that tidal power can play a significant role in the future energy mix. These dam proposals undergo rigorous scrutiny over their feasibility and environmental implications, despite presenting opportunities to deliver sustainable large-scale electricity supplies to the national grid. Preceding efforts to harness the UK's vast untapped tidal energy resource through barrages were dismissed on the grounds of feasibility and environmental uncertainties. There is now an urgent need to develop reliable engineering tools that can be used to improve the feasibility of new designs under consideration. In this case a novel coastal ocean finite element model is coupled with tidal power plant operation algorithms. This is applied to assess the performance of tidal range structures such as the high profile infrastructure projects of the Swansea Bay and Cardiff tidal lagoons. The analysis takes into account an adaptive operation over time that aims to maximise the electricity output over variable spring-neap tidal conditions.
It is demonstrated that such hydrodynamic models, when informed regarding the design of the constituent turbines and sluice gates installed, can simulate the dam's power plant operation to provide insights to the energy output and hydro-environmental impacts of such schemes.
... In the assessment of coastal reservoirs and lagoons, computational approaches have been reported that approximate the problem as anything from a 0-D [17], 1-D [18], 2-D [19][20][21] and 3-D [22] system. Due to the wide range of scales present in such engineering applications, hydrodynamic modeling that is capable of resolving the formation of near-field recirculation zones is feasible in only a subset of these approaches. ...
The generation and evolution of tidally-induced vortices in coastal and estuarine regions can influence water quality and sedimentary processes. These effects must be taken into consideration in the development of coastal reservoirs, barrages and lagoons, among other environmental flow applications. Results are presented here on the fate of large-scale vortices within confined tidally-forced domains. A computational approach is employed using the Thetis depth-averaged coastal ocean modeling framework. Initially, two test cases serve to demonstrate model capability in capturing the formation of dipoles downstream of oscillatory flow channels. Diagnostic quantities of vorticity and localized circulation are used to track the 2-D vortex evolution and dissipation. This approach is then applied to tidal lagoon geometries, where flows through the inlet induce a pair of counter rotating vortices (dipoles). Idealized model geometries and inlet conditions are used to determine the impact of three design parameters on large-scale vortical structures: (a) the lagoon geometry aspect ratio in the horizontal plane, (b) the inlet width and (c) the bathymetry profile as the coastline is approached. The dependence of vortex flushing behavior on the dimensionless ratio Wi/(UT) (where Wi is the width of the inlet channel, U is the maximum velocity and T is the tidal period) is reaffirmed, while the side walls and the sloping bathymetry are found to affect the vortex dissipation process.
... Much correlative work has been conducted in coastal regions with great tidal ranges all over the world. For example, Burrows et al. (2009), in an attempt to establish the potential scale of extractable resources, assessed the fully predictable tidal electricity generation from the conjunctive operation of five major estuary barrages on the west coast of the UK. Bae et al. (2010) studied real-time tidal characteristics during construction and after completion of the Sihwa tidal power plant near southern Incheon Port, Korea, and estimated the electricity output from the plant. ...
La Rance Tidal Range Power Station in France and Jiangxia Tidal Range Power Station in China have been both long-term successful commercialized operations as kind of role models for public at large for more than 40 years. The Sihwa Lake Tidal Range Power Station in South Korea has also developed to be the largest marine renewable power station with its installed capacity 254 MW since 2010. These practical applications prove that the tidal range energy as one kind of marine renewable energy exploitation and utilization technology is becoming more and more mature and it is used more and more widely. However, the assessment of the tidal range energy resources is not well developed nowadays. This paper summarizes the main problems in tidal range power resource assessment, gives a brief introduction to tidal potential energy theory, and then we present an analyzed and estimated method based on the tide numerical modeling. The technical characteristics and applicability of these two approaches are compared with each other. Furthermore, based on the theory of tidal range energy generation combined with flux conservation, this paper proposes a new assessment method that include a series of evaluation parameters and it can be easily operated to calculate the tidal range energy of the sea. Finally, this method is applied on assessment of the tidal range power energy of the Jiantiao Harbor in Zhejiang Province, China for demonstration and examination.
Over the last two decades, a large body of academic scholarship has been generated on wave and tidal energy related topics. It is therefore important to assess and analyse the research direction and development through horizon scanning processes. To synthesise such large-scale literature, this review adopts a bibliometric method and scrutinises over 8000 wave/tidal energy related documents published during 2003–2021. Overall, 98 countries contributed to the literature, with the top ten mainly developed countries plus China produced nearly two-thirds of the research. A thorough analysis on documents marked the emergence of four broad research themes (dominated by wave energy subjects): (A) resource assessment, site selection, and environmental impacts/benefits; (B) wave energy converters, hybrid systems, and hydrodynamic performance; (C) vibration energy harvesting and piezoelectric nanogenerators; and (D) flow dynamics, tidal turbines, and turbine design. Further, nineteen research sub-clusters, corresponding to broader themes, were identified, highlighting the trending research topics. An interesting observation was a recent shift in research focus from solely evaluating energy resources and ideal sites to integrating wave/tidal energy schemes into wider coastal/estuarine management plans by developing multicriteria decision-making frameworks and promoting novel designs and cost-sharing practices. The method and results presented may provide insights into the evolution of wave/tidal energy science and its multiple research topics, thus helping to inform future management decisions.
People often experience tidal influence at the coast, where the sea meets the land, with a daily or twice-daily rise and fall of the water level. Understanding and predicting tides is critical for: shoreline/hazard management; port, harbor, and shipping activities; renewable energy; and infrastructure management (e.g., telecommunication cables). Accurate prediction is also critical to ensure water sports and beach activities are carried out safely. In shallow waters, tides interact with bathymetry and other physical processes, such as: surges, waves, and density currents. Understanding the net (tidally averaged or residual) flow is key to explaining the transport of particulate and dissolved biogeochemical tracers and physical properties, such as heat and carbon. To observe the tide, (global) gage networks are installed, often providing near real-time data. Harmonic analysis of these data allows accurate prediction of the tide to support the numerous recreational and commercial activities that take place in shelf seas and at the coast.
Tidal Range Structures (TRS) have been considered for large-scale electricity generation for their potential ability to produce reasonably predictable energy without the emission of greenhouse gases. Once the main forcing components for driving the tides have deterministic dynamics, the available energy in a given TRS has been estimated, through analytical and numerical optimisation routines, as a mostly predictable event. This constraint imposes state-of-art flexible operation methods to rely on tidal predictions to infer best operational strategies for TRS, with the additional cost of requiring to run optimisation routines for every new tide. In this paper, a Deep Reinforcement Learning approach (Proximal Policy Optimisation through Unity ML-Agents) is introduced to perform automatic operation of TRS. For validation, the performance of the proposed method is compared with six different operation optimisation approaches devised from the literature, utilising the Swansea Bay Tidal Lagoon as a case study. We show that our approach is successful in maximising energy generation through an optimised operational policy of turbines and sluices, yielding competitive results with state-of-art optimisation strategies, with the clear advantages of requiring training once and performing real-time automatic control of TRS with measured ocean data only.
Tidal power lagoons have the potential to provide a reliable and long-term source of renewable power. The implementation of tidal lagoons will impact the tidal conditions and hydrodynamics of the surrounding coastal system. Impact assessments in the academic literature have generally investigated working proposals from industry of various shapes and sizes. As such, differences between the impacts arising from considered power plants in varying sites are in part influenced by the individual scheme characteristics, potentially masking the influence of site-specific factors. In this study, scheme design consistency is maintained, providing a basis to focus solely on the merits of the selected locations with regards to any associated impacts. The simulated tidal power lagoons are located in the Bristol Channel and Irish Sea, two distinct but tidally connected regions on the British coastline with contrasting marine environment characteristics. Results indicate that the more constrained geometry of the Bristol Channel contributes to higher individual and cumulative impacts than potential developments in the Irish Sea. This is in part facilitated by the higher degree of blockage introduced by tidal lagoon developments in the Bristol Channel. Furthermore, far-field impacts are found to be less pronounced compared to predictions reported in tidal barrage modelling studies.
Offshore Renewable Energy (ORE), comprising marine (wave and tidal energy), and offshore wind, has the potential to supply large amounts of ‘green’ sustainable energy, reducing CO2 emissions. The main obstacles to deployment so far are technical challenges and cost. However, there are also concerns about how harnessing offshore energy can affect the local habitats and marine life, as well as introducing far-field and long-term changes in the physical environment of the sea, which may combine with climate change in unforeseen ways to affect marine ecosystems. The precautionary principle, combined with the requirement for monitoring, introduces obstacles (and costs) which have so far prevented the deployment of offshore renewable energy on a large scale. Here we discuss the physical changes that may occur and the impacts these may have on habitats, species and ecosystems. We explore the possible environmental impacts of offshore wind and marine energy deployment and the options for mitigation of these. This information can assist planners, regulators and developers of offshore energy systems. Some examples of existing and proposed deployments are provided (mainly focusing on the UK), in order to illustrate discussion of the environmental issues. We identify the need for better understanding of the environmental impacts at a population and ecosystem level and identify a way forward to improve the environmental consenting process.
There is a growing research interest in tidal current energy, as it is more predictable when compared to wind and solar. Most past studies on tidal current energy focused on assessing the potential resource of sites with known fast tidal currents. Regions with less energetic tidal currents, but shallow waters for easy installation of energy infrastructure, have not been investigated. One potential tidal current energy location, which fits this categorization, is the strait of Novsko Ždrilo that connects the Novigrad Sea with the Adriatic Sea. In this study a high resolution 3D hydrodynamic model SCHISM was used to estimate the tidal current energy resource potential of this strait. The model results show that tidal current velocities are up to ten times higher than in the outer sea and vary spatially within the strait. However, the obtained velocities in the strait are not sufficient for viable energy exploitation with present tidal energy converter technology level. It is therefore important to further develop turbine type energy converters that could exploit these low tidal current energy resource locations. The applied model can be applied elsewhere for enhanced assessment of tidal energy potential, micro sitting of turbines and environmental impact. Since the current tidal energy potential estimates have been performed mainly with low resolution models, using high resolution models for assessment could lead to overall increase of tidal energy potential.
Based on the finite-volume coastal ocean model (FVCOM), a three-dimensional numerical model FVCOM was built to simulate the ocean dynamics in pre-dam and post-dam conditions in Bachimen (BCM). The domain decomposition method, which is effective in describing the conservation of volume and non-conservation of mechanical energy in the utilization of tidal energy, was employed to estimate the theoretical tidal energy resources and developable energy resources, and to analyze the hydrodynamic effect of the tidal power station. This innovative approach has the advantage of linking physical oceanography with engineering problems. The results indicate that the theoretical annual tidal energy resources is about 2×10 8 kWh under the influence of tidal power station; Optimized power installation is confirmed according to power generation curve from numerical analysis; the developable resources is about 38.2% of theoretical tidal energy resources with the employment of one-way electricity generation. The electricity generation time and power are 3479 hours and 2.55×10 4 KW, respectively. The power station has no effect on the tide pattern which is semi-diurnal tide in both two conditions, but the amplitudes of main constituents apparently decrease in the area near the dam, with the M 2 decreasing the most, about 62.92 cm. The tidal prism shrinks to 2.28×10 7 m 3 , but can still meet the flow requirement for tidal power generation. The existence of station increases the flow rate along the waterway and enhances the residual current. There are two opposite vortexes formed on the east side beside the dam of the station, which leads to pollutants gathering.
There is growing interest in harnessing renewable energy resources in Latin America. Converting the energy of the tides into electricity has the distinct advantage of being predictable, yet the tidal range resource of Latin America is largely unquantified. The northern part of the Gulf of California (GC) in Mexico has a relatively large mean tidal range (4m–5m), and so could be a potential site for tidal range energy exploitation. A detailed quantification of the theoretical tidal range energy resource was performed using tidal level predictions from a depth-averaged barotropic hydrodynamic model. In addition, a 0-D operation modelling approach was applied to determine the power that can be technically extracted at four key sites. The results show that the annual energy yield ranges from 20 to 50 kWh/m², while the maximum values are between 45 and 50 kWh/m² in the vicinity of the Gulf of Santa Clara. Within the region, the Gulf of Santa Clara is one of the most promising, delivering a technical annual energy output of 125 GWh (ebb-only generation), 159 GWh (two-way) and 174 GWh (two-way with pumping) within an impoundment area of 10 km². This equates to 50%, 40% and 33% of the absolute value power relative to a much-studied reference site (Swansea Bay, UK) that has been under consideration as the world's first tidal lagoon power plant. This study provides the basis for more detailed analysis of the GC to guide selection of suitable sites for tidal range energy exploitation in the region.
This paper proposes an innovative desalination technology for sustainable off-grid systems taking advantage of complementary features of tidal range and solar PhotoVoltaic (PV) energies. According to the literature survey, this proposal has not been considered before. Since fresh water production can be easily stored, the key issue in designing SeaWater Reverse Osmosis (SWRO) desalination plants is to minimise the capital cost required per m³ of fresh water produced throughout the plant lifetime. In addition, water cost of renewable energy - driven desalination strongly depends on decisions concerning battery capacity and nominal power installed, thus hybrid systems play and important role in this regard. The energy analysis performed quantifies the temporal complementarity of tidal and solar resources in an exemplary case study of a semiarid plant location at Broome, Australia. An estimation of the yearly energy production profile of the tidal range power plant is calculated with a zero-dimensional numerical model whereas the System Advisor Model (SAM) is used for the solar PV plant. The main result obtained is the great temporary complementarity of tidal and solar photovoltaic resources for SWRO application. For a given size of the PV generator the inclusion of the tidal range power plant implies an increase of the operating time of the desalination plant at nominal capacity between 1.8 and 2.8 times compared to the only solar PV driven case. This result depends on the SWRO nominal capacity. The recommended design for the case study consists in off-grid desalination plants, with minimum battery capacity if any, powered by a hybrid energy system with a ratio of installed desalination capacities of 55·10³ m³/d per each hydraulic turbine of 10 MW. This system can be operated at full load a 42% of the year maximizing the yearly fresh water production.
For a long time, Iraq has been suffering from the environmental pollution and electricity crisis. Therefore, tidal energy is one of the best renewable sources should be used to solve together the environmental pollution and electricity crisis. Tidal energy is usually available in coastal areas. Southern of Iraq has coastal areas in Basra Governorate on the northern Arabian Gulf. Therefore, this study has been investigated the possibility of establishing tidal power stations in two locations in Basra, Um Qasr and Al-Faw. In the case of the construction of a 4km 2 tidal barrage in Um Qasr, the electricity generated was 98.85MW and 197.69MW to meet the demand for electricity in Basra by 6.59% and 13.18% in the case of one-way and two-way generation, respectively. While in case of construction of a 4km 2 tidal lagoon in Al-Faw, the electricity generated was 31.37MW and 62.73MW to meet the demand for electricity in Basra by 2.09% and 4.18% in the case of one-way and two way generation, respectively. So, this study clearly shows that tidal energy can contribute significantly to relief the electricity crisis in Basra Governorate.
Urban energy models assume that energy is imported from outside the urban area. Forecast increases in urban population and energy use intensity will increase energy requirements. One alternative is to integrate sources of renewable energy within cities boundaries. To do so, differences in urban form, resources availability, energy requirements, condition of buildings, infrastructure, and population and building density make city-specific analysis necessary. This study identifies 14 factors that urban planners should consider to make the most appropriate technology choices for a given city. Through consultation with 78 experts, the presence of renewable energy sources was selected as the most important factor, followed by economic conditions in the city. The least important factors were environmental consequences of global warming, eutrophication and acidification.
Details are given of the growing worldwide interest in tidal renewable energy projects, including tidal stream devices and tidal range structures (i.e. barrages and lagoons), but the main emphasis in this chapter is on tidal range renewable energy structures. In investigating the hydro-environmental impacts of such tidal energy schemes, both for regional and far field effects, a 2D numerical model has been refined to predict the hydrodynamic impacts, including wake effects and flood risk and hazard impacts, and changes in the concentration distribution of conservative and nonconservative solutes, including primarily salinity, turbidity, fecal indicator organisms, and phosphorous and nitrogen levels. The model has been applied to a number of key sites and particularly in the Severn Estuary, UK, which has the second highest tidal range worldwide. The key schemes considered and reported herein include: (i) a series of lagoons along the North Wales coast and (ii) a barrage across the mouth of the Severn Estuary. The main findings are that: (i) two-way generation offers the best options for maintaining the current conditions in the region as closely as possible, (ii) boundary conditions need to be generated from the Continental Shelf, (iii) momentum conservation is crucial for turbine representation, (iv)lagoons interact with one another, reducing efficiency, (v) the design of turbine distribution is critical for optimum efficiency and minimal environmental change. © 2018 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.
Some regions of the world concurrently experience a high wave and a high tidal energy resource. These regions include the seas of the northwest European continental shelf, the Gulf of Alaska, New Zealand, northwest Australia, and the Atlantic seaboard of Argentina. Due to the interaction of waves and tides, special consideration needs to be given to resource characterization of marine renewable energy schemes developed in such regions. Waves have been shown to reduce the tidal current, which, because tidal-stream power is proportional to the cube of velocity, reduce the available energy resource. Further, waves can reduce the tidal-stream energy resource during extreme wave periods when ocean renewable devices may not operate. Waves should be also considered in the design and resilience of tidal-stream energy devices. Hence, waves can have a critical effect on the planning, operation, maintenance, and resource assessment of tidal energy sites. Conversely, tides can significantly alter wave properties through various wave-current interaction mechanisms. For example, tidal currents can alter wave steepness which is an important consideration in the design of marine energy mooring. Wave power, in general, is proportional to the wave group velocity and the wave height squared, both of which change in presence of tidal currents. Therefore, resource assessments of such regions should account for the way that one marine energy resource affects another at a variety of timescales from semidiurnal, spring-neap, to seasonal. Finally, wave-current interaction processes affect turbulence, and the dynamics of sediment transport; therefore, they should be considered when the impact of an energy device, or an array of such devices, on the environment is studied. This chapter introduces the basic concepts of wave-tide interaction in relation to the ocean renewable energy resource assessment. Various aspects of the marine renewable energy industry that are affected by wave-tide interactions, such as resource assessment and the influence of wave-tide interactions when characterizing the oceanographic site conditions, are discussed. Methods ranging from simplified analytical techniques to complex fully coupled wave-tide models are explained.
An analysis of transient momentum balances is carried out to elucidate circulation, dynamics, and exchange mechanisms at shallow barotropic tidal inlets. Circulation is computed using a depth-integrated, fully nonlinear, time-stepping, finite-element model with variably spaced grids having horizontal resolution down to 50 m. Velocity and elevation fields from the model are used to directly evaluate the contribution of each term in the momentum equations to the overall momentum balance. A transformation of the x-y momentum terms into an s-n coordinate system is used to simplify the interpretation of the dynamics and provide vivid illustrations of the forces and resulting accelerations in the flow. The analysis is conducted for an idealized inlet and contrasted with a highly detailed model of Beaufort Inlet, North Carolina. Results show that momentum balances in the immediate vicinity of these inlets vary significantly in time and space and oscillate between two dynamical states. Near maximum ebb or flood, the alongstream momentum balances are dominated by advective acceleration, pressure gradient, and bottom friction. Cross-stream balances are dominated by centrifugal acceleration and pressure gradients. Near slack, balances more closely follow linear wave dynamics, with local accelerations balancing pressure gradients, and (to a lesser degree) Coriolis. Comparisons between the idealized inlet and Beaufort Inlet show broad similarities in these momentum balances. However, natural inlet geometry and bottom topography, as well as the tidal transmission characteristics of the sounds behind Beaufort Inlet produce strong asymmetries. Moreover, momentum balances are highly localized, often with subkilometer length scales. The dynamics are used to explain the physical mechanisms for inlet exchange. In particular, the results indicate that the cross-stream dynamics generate a ''wall'' along the length of an inlet during the stronger phases of the tide. The wall is established by opposing cross-inlet pressure gradients and centrifugal forces, and it poses a significant barrier to cross-inlet exchange during the stronger phases of the tide but is absent near slack.
This paper describes the potential environmental changes caused by tidal power installations with illustration for schemes in the eastern Irish Sea, focusing mainly on major estuarine barrages. The generic impacts in the near-field and far-field are discussed. Results from a zerodimensional and a two-dimensional model are presented: the former allows rapid calculations to be made for a large range of options while the latter allows the full effect on two-dimensional hydrodynamics to be investigated. It is shown that there may be a significant change in tidal amplitude at the coast of Northern Ireland. The bed stress in the Bristol Channel will be significantly reduced if a Severn barrage is constructed. Some effects on the tidal mixing are expected although the location of tidal fronts in the Irish and Celtic Seas will not be changed significantly. The largest environmental impact is expected to be on the amount of inter-tidal area retained after construction of an estuarine barrage. It is shown that the loss of mudflats can be substantially reduced by using a dual-mode (ebb and flood generation) scheme with an increased number of turbines over the lowestcost option.
This paper describes the substantial potential of tidal barrage solutions for renewable energy generation in the UK. It demonstrates that installations on as few as eight major estuaries should be capable of meeting at least 10% of present electricity demand, and possibly significantly more, employing fully proven technology. This should be achievable, under favourable UK Treasury discount rates, at unit electricity prices that are likely to be competitive against future costs of alternative sources. This potential substantially exceeds that of 'tidal stream' turbine or practicable 'lagoon' systems, much vaunted in recent times. It also draws attention to a recent study investigating the tidal power potential in the north-west of England.
Basic parameters governing the design of tidal power schemes are identified and converted to dimensionless form by reference to (i) the mean tidal range and (ii) the surface area of the enclosed basin. Optimum values for these dimensionless parameters are derived and comparison made with actual engineering designs. A theoretical framework is thus established which can be used (i) to make a rudimentary design at any specific location or (ii) to compare and evaluate designs for various locations.Both one-way (flood or ebb) and two-way (flood and ebb) schemes are examined and, theoretically, the two-way scheme is shown to be more efficient. However, in practice, two-way schemes suffer disadvantages arising from (i) two-way flow through both turbines and sluices and (ii) lower average turbine heads.An important dimensional aspect of tidal power schemes is that, while energy extracted is proportional to the tidal amplitude squared, the requisite sluicing area is proportional to the square root of the tidal amplitude. In consequence, sites with large tidal amplitudes are best suited to tidal power development whereas for sites with low tidal amplitudes sluicing costs may be prohibitive.
This paper presents a systematic study of the spatial convergence characteristics of a depth-integrated, finite element, M 2 tidal model of the western North Atlantic, Gulf of Mexico and Caribbean Sea. Two sequences of model runs with uniform grids are used to separate the effects of increased grid resolution (i.e., more grid points per M 2 wave length) from the effects of improved resolution of bathymetric features that accompanies increased grid resolution. These runs show that the model is much more sensitive to bathymetric resolution than it is to horizontal grid spacing. A third sequence of model runs with nonuniform grids shows that a grid designed to maintain a constant ratio of M 2 wave length to grid spacing is quite inadequate for our problem. Rather, increased resolution in the vicinity of steep bathymetric gradients is critical for obtaining a converged numerical solution. A nonuniform grid can be a very efficient way of obtaining high resolution in critical areas without overburdening computations with a needlessly fine grid throughout the entire model domain.
Quarter-wave tidal resonance in the Bristol Channel - Celtic Sea shelf area is investigated using a simple one-dimensional numerical model. It is found that semi-diurnal resonant modes extending across the shelf are possible. The effects of tidal barrages on resonant period are determined. (A)
This paper examines the similarities and contrasts between environmental and water quality changes caused by the 1966 tidal power barrage at La Rance in North Brittany, France and those expected to result from construction of a tidal power barrage in the Severn estuary in the UK. Over the 40-year period since the opening of La Rance, a great deal of knowledge has been accumulated concerning the operation of such schemes and the way water quality and ecosystems have altered. Knowledge gained from experiences at Rance is consequently of great benefit in predicting the effects of the proposed Severn barrage. The nature of the changes anticipated in the Severn estuary is thus unambiguous, but whether this would make the estuary better or worse is a matter of perception. As at Rance, it would be different.
Three finite element codes, namely TELEMAC, ADCIRC and QUODDY, are used to compute the spatial distributions of the M2, M4 and M6 components of the tide in the sea region off the west coast of Britain. This region is chosen because there is an accurate
topographic dataset in the area and detailed open boundary M2 tidal forcing for driving the model. In addition, accurate solutions (based upon comparisons with extensive observations)
using uniform grid finite difference models forced with these open boundary data exist for comparison purposes. By using boundary
forcing, bottom topography and bottom drag coefficients identical to those used in an earlier finite difference model, there
is no danger of comparing finite element solutions for “untuned unoptimised solutions” with those from a “tuned optimised
solution”. In addition, by placing the open boundary in all finite element calculations at the same location as that used
in a previous finite difference model and using the same M2 tidal boundary forcing and water depths, a like with like comparison of solutions derived with the various finite element
models was possible. In addition, this open boundary was well removed from the shallow water region, namely the eastern Irish
Sea where the higher harmonics were generated. Since these are not included in the open boundary, forcing their generation
was determined by physical processes within the models. Consequently, an inter-comparison of these higher harmonics generated
by the various finite element codes gives some indication of the degree of variability in the solution particularly in coastal
regions from one finite element model to another. Initial calculations using high-resolution near-shore topography in the
eastern Irish Sea and including “wetting and drying” showed that M2 tidal amplitudes and phases in the region computed with TELEMAC were in good agreement with observations. The ADCIRC code
gave amplitudes about 30cm lower and phases about 8° higher. For the M4 tide, in the eastern Irish Sea amplitudes computed with TELEMAC were about 4cm higher than ADCIRC on average, with phase
differences of order 5°. For the M6 component, amplitudes and phases showed significant small-scale variability in the eastern Irish Sea, and no clear bias between
the models could be found. Although setting a minimum water depth of 5m in the near-shore region, hence removing wetting
and drying, reduced the small-scale variability in the models, the differences in M2 and M4 tide between models remained. For M6, a significant reduction in variability occurred in the eastern Irish Sea when a minimum 5-m water depth was specified. In
this case, TELEMAC gave amplitudes that were 1cm higher and phases 30° lower than ADCIRC on average. For QUODDY in the eastern
Irish Sea, average M2 tidal amplitudes were about 10cm higher and phase 8° higher than those computed with TELEMAC. For M4, amplitudes were approximately 2cm higher with phases of order 15° higher in the northern part of the region and 15° lower
in the southern part. For M6 in the north of the region, amplitudes were 2cm higher and about 2cm lower in the south. Very rapid M6 tidal-phase changes occurred in the near-shore regions. The lessons learned from this model inter-comparison study are summarised
in the final section of the paper. In addition, the problems of performing a detailed model–model inter-comparison are discussed,
as are the enormous difficulties of conducting a true model skill assessment that would require detailed measurements of tidal
boundary forcing, near-shore topography and precise knowledge of bed types and bed forms. Such data are at present not available.
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