For tidal-stream energy to become a competitive renewable energy source, clustering multiple turbines into arrays is paramount. Array optimisation is thus critical for achieving maximum power ...performance and reducing cost of energy. However, ascertaining an optimal array layout is a complex problem, subject to specific site hydrodynamics and multiple inter-disciplinary constraints. In this work, we present a novel optimisation approach that combines an analytical-based wake model,
FLORIS
, with an ocean model,
Thetis
. The approach is demonstrated through applications of increasing complexity. By utilising the method of analytical wake superposition, the addition or alteration of turbine position does not require re-calculation of the entire flow field, thus allowing the use of simple heuristic techniques to perform optimisation at a fraction of the computational cost of more sophisticated methods. Using a custom condition-based placement algorithm, this methodology is applied to the Pentland Firth for arrays with turbines of
3.05
m
/
s
rated speed, demonstrating practical implications whilst considering the temporal variability of the tide. For a 24-turbine array case, micro-siting using this technique delivered an array 15.8% more productive on average than a staggered layout, despite flow speeds regularly exceeding the rated value. Performance was evaluated through assessment of the optimised layout within the ocean model that treats turbines through a discrete turbine representation. Used iteratively, this methodology could deliver improved array configurations in a manner that accounts for local hydrodynamic effects.
•Temporal characterisation of wave and tidal resource availability for Great Britain.•Ten metrics used to explore temporal characterisation and supply-demand matching.•Generation profiles with marine ...energy consistently outperform those without.•Correlation with load is not a suitable metric to establish supply-demand alignment.•Detailed discussion of potential GB power system benefits from marine energy.
Wave and tidal energy have the potential to provide benefits to power systems with high proportions of stochastic renewable generation. This is particularly applicable in combination with wind and solar photovoltaics, as the offsetting of these renewable resources results in more reliable renewable generation. This study utilises ten metrics to quantify the temporal complementarity and supply-demand balancing requirements of the energy mix in Great Britain, to investigate the potential magnitude of these system benefits. Wave and tidal generation profiles are created using historical resource data and hydrodynamic models. The results show that the inclusion of wave and tidal generation creates a renewable energy mix which is more available under multiple conditions: throughout a year of operation; at times of peak demand; for multiple consecutive hourly time periods; and at times when wind and solar generation are not available. Three regional case studies also show that the inclusion of marine energy allows for improved regional supply-demand matching, reducing instances of energy shortage and excess and potentially relieving transmission congestion at particularly constrained locations within GB. Finally, the implications of these findings are discussed in terms of GB wholesale market operation, system balancing and system security.
The feasibility and sustainable operation of tidal lagoons and barrages has been under scrutiny over uncertainties with regards to their environmental impacts, potential interactions and energy ...output. A numerical modelling methodology that evaluates their effects on the hydro-environment has been refined to consider technical constraints and specifications associated with variable turbine designs and operational sequences. The method has been employed to assess a number of proposals and their combinations within the Bristol Channel and Severn Estuary in the UK. Operational challenges associated with tidal range power plants are highlighted, while also presenting the capabilities of modelling tools tailored to their assessment. Results indicate that as the project scale increases so does its relative hydrodynamic impact, which may compromise annual energy output expectations if not accounted for. However, the manner in which such projects are operated can also have a significant impact on changing the local hydro-environment, including the ecology and morphology. Therefore, it is imperative that tidal range power plants are designed in such a way that efficiently taps into renewable energy sources, with minimal interference to the regional hydro-environment through their operation.
•We present formulations for the operation simulation of tidal lagoons and barrages within a hydrodynamic model.•We demonstrate that a tidal power plant's hydro-environmental impact is closely linked to its operational characteristics.•We calculate the energy potential and impacts of multiple tidal power plants under a range of conditions.•We highlight challenges and opportunities associated with the power generation intermittency of tidal range turbines.
Determining the respective attribution proportions of climate change and land use change to streamflow variations in river systems is of increasing interest to researchers and practitioners tasked ...with managing river basins. This paper proposes an extension to established techniques of attributing the relative proportions of climate change (CC) and land use change (LUC) drivers to streamflow change by instead considering these proportions as distributed through a probability density function (pdf), rather than as a point value. The novel method is demonstrated for the River Tweed in the UK. Results are determined by the flow, temperature and precipitation data, and upon the algorithms used to identify change points in these vectors. The ratio of the LUC and CC attribution proportions (Land Use and Climate Change Attribution Proportions, LCAP) is more appropriately expressed as a vector of values, each associated with its own probability value within a probability density function. The paper demonstrates that the LCAP ratio pdf can vary considerably over time and that it is possible to track physical changes in the catchment in the evolution of the probability density function. Results show that the land-use change/climate change attribution proportion (LCAP) ratio varies over time and can be expressed as probabilistic estimate. It can be concluded, with a high degree of confidence, that for the Tweed catchment the LUC is a significant driver of streamflow change. Hence this finding may have implications for future catchment flood management utilising nature based solutions (NbS) to reverse landscape degradation and mitigate effects of climate change, provided that the economic and social costs are outweighed by the benefits.
•We describe new optimisation approaches for improving the operational design of tidal power plants.•We demonstrate the value of flexible operation in maximising income from the Day Ahead energy ...market.•An income-based optimisation for a tidal lagoon case led to a 23% improvement in energy market income.•Tidal range power plants can have a short-term storage capability for generation during high-demand periods.
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.
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.
•Differences of single-basin against linked-basin tidal energy systems are presented.•Linked-basin systems generate less energy relative to single-basin power plants.•Twin-basin systems can be configured to generate power continuously in each cycle.
Wave–Current Interactions (WCI) emerge in nearshore coastal areas, prompting the development of coupled modelling systems to simulate these phenomena. We present a new multi-scale parallelised ...Python-interfaced WCI coupled system adopting a component-based approach enabling model-component integration without inhibiting their respective development. The underlying principles emphasise model equitability, flexibility and language interoperability. The hybrid model comprises the spectral wave model SWAN and the 2-D shallow-water equation model, Thetis. The coupling is performed through the Basic Model Interface. The coupled WCI model is the first to employ a Python interface, while maintaining the efficiency of different lower-level compiled programming languages, Fortran for SWAN and C for Thetis. We discuss the system implementation, architecture, and underlying physics considered. The coastal waters of Duck, NC, serve as a practical demonstration in simulating WCI. We then elaborate on the rationale for the coupled system design to inform the development of coupled modelling frameworks for environmental systems.
•A new multi-scale WCI system intended for regional scales is presented.•Coupling models of diverse programming languages fosters language interoperability.•Component-based coupling is promoted by employing a coupling interface.•Model equitability is advocated by establishing Python as the system’s central hub.•The rationale for the selected model components is explained.
•We describe numerical methods to simulate the operation of tidal range power plants.•We couple simplified power plant operation models with gradient-based optimisation algorithms.•The consideration ...of a flexible operation with pumping is shown to have the potential to deliver significant energy gains.•Optimisation of larger plant designs should be coupled with hydrodynamics solvers.
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. 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 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.
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.
•Consistent tidal lagoon design highlights influence of marine environment on impacts.•Impacts resulting from developments in Bristol Channel and Irish Sea combine linearly.•Cumulative impacts in the Bristol Channel notable in whole region.•Impacts of Irish Sea tidal lagoons more localised than in the Bristol Channel.
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