Matt Lewis

Bangor University · School of Ocean Sciences

Realistic oceanographic conditions are essential to consider in the design of resilient tidal-stream energy devices that can make meaningful contributions to global emissions targets. Depth-averaged or simplified velocity profiles are often used in studies of device performance, or device interaction with the environment. We improve representation...

When selecting suitable sites for tidal stream energy arrays, a wide range of factors must be considered, from the magnitude of the tidal stream resource, to realistic oceanographic conditions. Previous computational and laboratory-scale investigations into the impact of waves upon tidal turbines (such as turbine blade loadings) and turbine arrays...

Tidal Energy Converter (TEC) arrays are expected to reduce tidal current speeds locally, thus impacting sediment processes, even when positioned above bedrock, as well as having potential impacts to nearby offshore sand banks. Furthermore, the tidal dissipation at potential TEC sites can produce high suspended sediment concentrations (turbidity max...

A computationally inexpensive inundation model has been developed from freely available data sources for the northern Bay of Bengal region to estimate flood risk from storm surges. This is the first time Shuttle Radar Topography Mission (SRTM) terrain data have been used in a dynamic coastal inundation model. To reduce SRTM noise, and the impact of...

Field measurement of turbulence in strong tidal currents is difficult and expensive, but the tidal energy industry needs to accurately quantify turbulence for adequate resource characterisation and device design. Models that can predict such turbulence could reduce measurement costs. We compare a Regional Ocean Modelling System (ROMS) simulation wi...

ICOE 2022 presentation Are Marine Renewable Energies expensive? The LCOE (i.e. cost) of marine renewable energy is higher than other forms of renewable electricity. Marine renewable’s LCOE is projected to decrease with technology learning (i.e. TRL increase), but perhaps the valuation of renewable energy is wrong? For example, the predictability...

Worldwide increased demand for offshore renewable energy (ORE) industries and aquaculture requires developing efficient tools to optimize the use of the offshore space, reducing anthropic pressure. The synergetic development of marine renewable energy infrastructure with mariculture has been hypothesized as a way to reduce costs through shared infr...

Marine renewable energy site and resource characterisation, in particular tidal stream energy, require detailed flow measurements which often rely on high-cost in situ instrumentation which is limited in spatial extent. We hypothesise uncrewed aerial vehicles (UAV) offer a low-cost and low-risk data collection method for tidal stream environments,...

Compound estuarine flooding is driven by extreme sea-levels and river discharge occurring concurrently, or in close succession, and threatens low-lying coastal regions worldwide. We hypothesise that these drivers of flooding rarely occur independently and co-operate at sub-daily timescales. This research aimed to identify regions and individual est...

Estuaries are places where floods are usually threatening from two main sources: high tide or storm surge from the sea, and high river flow from the land. Since estuaries are, at the same time, places of great biodiversity and highly populated areas, an adequate flood modelling approach is needed to mitigate and reduce the possible risk. In this st...

Resource quantification is vital in developing a tidal stream energy site but challenging in high energy areas. Drone-based large-scale particle image velocimetry (LSPIV) may provide a novel, low cost, low risk approach that improves spatial coverage compared to ADCP methods. For the first time, this study quantifies performance of the technique fo...

Free-flowing rivers have been impacted by anthropogenic activity and extensive hydropower development. Despite this, many opportunities exist for context-specific energy extraction, at locations deemed undesirable for conventional hydropower plants, in ways that reduce the scale of operation and impact. Hydrokinetic energy conversion (HEC) is a ren...

Southeast Asia is considered to have some of the highest levels of marine plastic pollution in the world. It is therefore vitally important to increase our understanding of the impacts and risks of plastic pollution to marine ecosystems and the essential services they provide to support the development of mitigation measures in the region. An inter...

Climate change induced sea level rise (SLR) is likely to impact estuarine hydrodynamics and associated processes, including tidal energy. In this study, a hierarchy of factors influencing the future of estuarine tidal energy resources is proposed based on their relevance to SLR. These include primary factors (e.g., tidal prism, tidal range, tidal c...

Background Larval connectivity between distinct benthic populations is essential for their persistence. Although connectivity is difficult to measure in situ, it can be predicted via models that simulate biophysical interactions between larval behaviour and ocean currents. The blue mussel (Mytilus Edulis L.) is widespread throughout the northern he...

Estuaries are places where floods are a constant threat from both land and sea direction. At the same time estuaries are places of great biodiversity and traditionally very populated areas, which makes them highly vulnerable. In this study LISFLOOD-FP hydrodynamical model is applied to examine the effectiveness of different coastal protection scena...

This review provides a critical, multi-faceted assessment of the practical contribution tidal stream energy can make to the UK and British Channel Islands future energy mix. Evidence is presented that broadly supports the latest national-scale practical resource estimate, of 34 TWh/year, equivalent to 11% of the UK’s current annual electricity dema...

tidal energy may appear expensive, but perhaps this is due to the valuation system - and the predictability makes it worth any additional cost?

Providing remote and off-grid coastal communities with renewable and sustainable electricity is a goal that could be met with tidal-stream technology. Presently there are many turbine designs, which presents a challenge when making an unbiased resource assessment. Moreover, the majority of tidal-stream turbines appear to be aimed at producing large...

Lagrangian Particle Tracking Models (PTMs) have a wide range of applications in the marine environment, from predicting the dispersal of microplastics to larval transport. The increased complexity of ocean-modelling techniques has seen simulation of transport move from probabilistic approaches (e.g. advection and random walk) to more deterministic...

Whenever considering new tidal stream sites; information on current characteristics is of paramount importance. This contribution describes a methodology to measure surface currents at tidal stream sites using drones and provides initial validation of the approach against velocities measured by GPS surface drifters. Drones have the potential to mea...

The small area of the United Kingdom relative to weather systems makes renewable energy sources variable on short time scales. Short term variability is therefore a growing concern with increasing amounts of renewable energy integration. In this work, we address how tidal energy can contribute to reducing medium-term variability in the future UK en...

Estuaries are potentially exposed to compound flooding where weather-driven extreme sea levels can occur synchronously with extreme fluvial discharge to amplify the hazard. The likelihood of compound flooding is difficult to determine due to multiple interacting physical processes operating at sub-daily scales, and poor observation records within e...

Hydrokinetic energy conversion refers to the conversion of kinetic energy in moving water to electricity. It offers an alternative to conventional hydropower, with benefits of modularity and scalability, in addition to being environmentally and socially less impactful. This study aims to determine the theoretical global riverine hydrokinetic resour...

Tidal-stream energy can be predicted deterministically, provided tidal harmonics and turbine-device characteristics are known. Many turbine designs exist, all having different characteristics (e.g. rated speed), which creates uncertainty in resource assessment or renewable energy system-design decision-making. A standardised normalised tidal-stream...

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 th...

There has been a significant increase in the number of published tidal-stream energy resource assessments in recent years due to the growing availability of open-source hydrodynamic models, and freely available data for model bathymetry (e.g. GEBCO_2014 and ETOPO) and boundary conditions (e.g. TPXO, FES, EOT). This study examines how the choice of...

In March 2010, a sequence of three major rainfall events in New England (United States) led to a record‐breaking flooding event in the Pawtuxet River Watershed with a peak flow discharge of about 500‐year return period. After development of hydrological and hydraulic models, a number of factors that played important roles in the impact of this floo...

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...

Better understanding of the global wave climate is required to inform wave energy device design and large-scale deployment. Spatial variability in the global wave climate is analysed here to provide a range of characteristic design wave climates. K-means clustering was used to split the global wave resource into 6 classes in a device agnostic, data...

Tidal energy has the opportunity to bring reliable electricity to remote regions in the world. A resource assessment, including the response of the tidal stream resource to fluctuations in the Indonesian Through Flow (ITF) is performed using the Regional Ocean Modelling System (ROMS) to simulate four different scenarios for flow through the Lombok...

Resource assessments are essential, yet many are based on hydrodynamic models forced with coarse global data products for bathymetry and open-boundary forcing. The aim of this paper is to examine how selection of: (1) two open source bathymetry products (GEBCO and ETOPO) and the inclusion of a higher-resolution bathymetry survey; and (2) considerin...

Natasha has teamed up with the former lighthouse keeper of Ynys Enlli and researchers at Bangor University, so she can achieve a lifelong ambition; to swim the treacherous 3km stretch of water across Enlli sound. A film of Natasha's swim and the explanation of the science and maths behind her attempt can be found at this link (https://youtu.be/UaxX...

Temporal variability in renewable energy presents a major challenge for electrical grid systems. Tides are considered predictable due to their regular periodicity; however, the persistence and quality of tidal-stream generated electricity is unknown. This paper is the first study that attempts to address this knowledge gap through direct measuremen...

The combined hazard of large waves occurring at an extreme high water could increase the risk of coastal flooding. Wave-tide interaction processes are known to modulate the wave climate in regions of strong tidal dynamics, yet this process is typically omitted in flood risk assessments. Here, we investigate the role of tidal dynamics in the nearsho...

Small global positioning system (GPS) trackers are now routinely used to study the movement and behaviour of birds at sea. If the birds rest on the water they become “drifters of opportunity” and can be used to give information about surface currents. In this paper, we use a small data set from satellite-tracked razorbills (Alca torda) in the Irish...

Small GPS trackers are now routinely used to study the movement and behaviour of birds at sea. If the birds rest on the water they become drifters of opportunity and can be used to give information about surface currents. In this paper, we use a small data set from satellite-tracked razorbills (Alca torda) in the Irish Sea to test the potential of...

Characterisations of the tidal stream resource and its variability over various timescales are crucial for the development of the tidal stream energy industry. To date, no research has compared resource sensitivity in standing wave (when peak currents occur midway between high and low water) and progressive wave (where peak currents occur at high a...

To reduce the uncertainty in resource assessments, the physical presence of the turbine arrays must be accounted for. Using a 3-D Regional Ocean Model with tidal stream energy extraction, we show that in regions where tidal stream energy sites have been leased in close proximity to each other there is some degree of inter-connectivity. In this pape...

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 feasibilit...

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 feasibilit...

There has been a growing interest in tidal-stream energy, with most past studies focusing on assessing the potential resource of sites with fast tidal currents in relatively shallow water. Regions with less energetic tidal currents, but in deeper waters, have been overlooked. One potential tidal-stream energy region, which fits this categorization,...

To mitigate against future changes to estuaries such as water quality, catchment and estuary models can be coupled to simulate the transport of harmful pathogenic viruses, pollutants and nutrients from their terrestrial sources, through the estuary and to the coast. To predict future changes to estuaries, daily mean river flow projections are typic...

Accounting for the feedbacks of tidal stream energy extraction reduces uncertainties within modelled resource assessments and environmental impact studies. Historically, modellers have implemented tidal energy extraction in regional-scale models using an enhanced drag applied at the seabed or a uniform drag applied over the water column. Here, we c...

As the marine renewable energy industry evolves, in parallel with an increase in the quantity of available data and improvements in validated numerical simulations, it is occasionally appropriate to reassess the wave and tidal resource of a region. This is particularly true for Scotland-a leading nation that the international community monitors for...

Acoustic Doppler current profilers (ADCPs) are commonly used to assess mean currents and turbulence at energetic sites. Since 2014, five-beam ADCP configurations have become more common, but conventional analysis of turbulence properties is still based on the four-beam Janus configuration. We use measurements from a single site to investigate impro...

Tidal energy extraction offers a highly predictable, reliable energy resource. Natural flow regimes will be altered by the installation of large scale tidal arrays. Bed morphology, sensitive to changes in tidal flow, will be impacted as a result of feedbacks between tidal arrays and coastal hydrodynamics. This research investigates the impact of la...

Following recent and rapid development, the contribution of renewable generation to a low carbon energy system can be significantly expanded through careful design of tidal-stream schemes. Although tidal circulation can be almost 100% predicted – and a typical tidal cycle describes the typical tidal-stream energy resource, variability is significan...

To make meaningful contributions to renewable energy targets, a tidal-stream energy device that can be deployed at a wide range of sites throughout the world is needed. To inform industry, the distribution of the global tidal-stream energy resource must be characterised. The "first-generation" of tidal energy devices are being developed for wave sh...

Advancements in computing and numerical models have enabled the practice of modelling the tidal stream resource in 3-D, albeit at a much higher computational cost than the traditional 2-D modelling approach. Modelling tidal energy extraction poses a multiscale challenge to the tidal energy research community, turbine scale - the hydrodynamic flow b...

A 30 day time series of depth averaged ADCP data from the coast of northwest Anglesey, in the Irish Sea.

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 t...

The majority of tidal energy convertors (TECs) currently under development are of a non-yawing horizontal axis design. However, most energetic regions that have been identified as candidate sites for installation of TEC arrays exhibit some degree of directional and magnitude asymmetry between incident flood and ebb flow angles and velocities, parti...

As the marine renewable energy industry evolves, in parallel with an increase in the quantity of available data and improvements in validated numerical simulations, it is occasionally appropriate to re-assess the wave and tidal resource of a region. This is particularly true for Scotland - a leading nation that the international community monitors...

Access to high performance computing has made 3-D modelling de rigueur for tidal energy resource assessments. Advances in computing resources and numerical model codes have enabled high resolution 3-D ocean models to be applied at basin scales, albeit at a much higher computational cost than the traditional 2-D modelling approach. Here, a compariso...

The assessment of the resource at potential kinetic in-stream tidal energy conversion sites must take into account far more than the basic characterization of flow speed, water depth and water column profile. Consideration should also be given to addressing and resolving other variables and factors that might contribute to uncertainty in analysis....

The regular and predictable nature of the tide makes the generation of electricity with a tidal lagoon or barrage an attractive form of renewable energy, yet storm surges affect the total water-level. Here we present the first assessment of the potential impact of storm surges on tidal-range power. Water-level data (2000–2012) at nine UK tide gauge...

Small variations in velocity lead to large variations in power. Using a device-specific power curve, technical power can be calculated for the data period. For data > 30 d, tidal analysis allows us to estimate more accurately annual power generation and variability from tides. The spatio-temporal resolution of the modelling simulation aligned to it...

The marine renewable energy industry is expanding globally in response to increased energy demands and the desire to curtail greenhouse gas emissions. Within the UK, Wales has the potential for the development of diverse marine renewable technologies, with a strong tidal range resource, areas of high tidal current energy, and a spatially limited wa...

Estuarine impact modelling can help quantify estuarine and coastal retention times for catchment-sourced material such as pathogenic viruses, pollutants, and macronutrients. Under the European Water Framework Directive, these systems require to be “future-proofed” to ensure climate change will not impact the objective for ‘good status’ in coastal w...

Satellite tracking data collected by The Royal Society for the Protection of Birds from tagged seabirds sitting on the water has revealed the potential for using this data to predict information about tidal current amplitude around the North coast of Anglesey, North Wales. Here we present a method by which these Lagrangian datasets can be used to p...