International Marine Energy Journal

The Importance of Empirical Particle Motion Measurements for Monitoring Underwater Noise from Wave Energy Converters

Carola Chicco — 2026-07-31

Underwater noise from Marine Energy Converters (MECs), including Wave Energy Converters (WECs), is a recognized stressor for marine organisms. Current monitoring guidelines focus on scalar pressure, but particle motion is equally important, especially in complex shallow-water environments where WEC systems can affect the soundscape. Many marine species detect sound primarily through particle motion, highlighting the need to include it in monitoring frameworks. This work underscores the importance and role of sound in marine habitats. Using a 3D accelerometer and hydrophone, we collected acoustic data near an Inertial Sea Wave Energy Converter (ISWEC) off Pantelleria, Sicily. Our initial measurements showed discrepancies between pressure and particle motion and higher variability along the vertical axis. These results stress the necessity of incorporating particle motion alongside pressure in underwater noise assessments, with potential implications for benthic and demersal species. They also highlight the need for deeper investigation into particle motion dynamics, particularly in the context of marine energy converter operations in shallow-water environments.

Comparing optical camera and imaging sonar observations of animal interactions with a tidal turbine

Christopher Bassett — 2026-07-31

The potential for animal injury or mortality because of collisions with operating current energy turbines remains an important research question with consequences for management of proposed marine energy projects. During a 141-day deployment of a small-scale (1 m²) tidal turbine, a sensor package including optical cameras and imaging sonars was used to record near-field interactions between animals and the turbine. Over 1000 animal interactions were captured by the optical cameras, including several species of fish, at least two species of diving birds, and harbor seals (Phoca vitulina). Both seals and fish were observed in the vicinity of the turbine while it was rotating, and a range of behaviors were captured. Seals and fish were also observed while the turbine was stationary, although the observed behaviors were different. Diving birds were observed regularly, but only during daytime hours and when the turbine was stationary. In this work, we summarize trends in animal behavior with respect to tidal elevation, time of day, and turbine operational state and discuss specific observations of collisions (only observed for fish), evasion (fish and seals), avoidance, and attraction. Previously published analysis focused on optical camera data due to their ability to resolve near-field interactions with the rotor. Here, co-temporal sonar data are used to provide additional context that includes capturing a higher degree of animal presence near the operating rotor than determined in review of the optical data, documenting additional examples of avoidance and evasion behavior using the larger field of view, and providing evidence of predator/prey interactions that may inform collision risk. Based on our experiences and findings we also recommend approaches for future projects seeking to acquire, analyze, and report on similar data sets.

Influence of Unidirectional Power Flow and Restoring Force Absence on Wavepiston Performance

Eugenio Gelos — 2026-07-31

Wavepiston is a novel wave energy converter (WEC) comprising multiple energy collectors coupled on a string, each equipped with a sail designed to harness surge excitation from incoming waves. The current configuration features two distinctive design characteristics that significantly influence its hydrodynamic behavior and control: (i) a passive Power Take-Off (PTO) enabling only unidirectional power flow, and (ii) the absence of hydrodynamic restoring capabilities. Despite recent technological progress and a high technology readiness level, limited attention has been given to implementing state-of-the-art control strategies for this device, particularly evaluating how its unique design features influence overall performance. Therefore, this preliminary study aims to evaluate how unidirectional power flow imposed by the passive PTO and the absence of restoring capabilities influence the following performance metrics: (i) power capture across various sea states, (ii) operational spaces of sail stroke and (iii) PTO control force, along with (iv) energy production in a specific wave climate. The results provide a basis for identifying performance trade-offs and support the evaluation of potential design pathways accounting for both device dynamics and wave climate characteristics.

Ocean Wave Energy in Australia

Hugh Wolgamot — 2026-07-31

This paper presents a comprehensive overview of the status and opportunities for wave energy in Australia, drawing on a national report completed in 2024. As the country with the largest wave energy resource in the world, Australia has an important role in the development of a global wave energy industry. This paper reviews the international and domestic landscape, Australia’s resource and market opportunities, as well as the industry, social and environmental context for an Australian wave energy industry. Based on these findings, a series of actions are recommended to catalyse the growth of an Australian industry, and make the most of the natural advantages the country is endowed with.

Understanding the exposure of marine life to electromagnetic fields generated by subsea cables

Valentina Caradonna — 2026-07-31

Electromagnetic fields (EMF) generated by wave and tidal energy subsea power cables can potentially impact marine life. The primary source of artificial EMF is subsea power cables, whose estimates of the propagating levels are typically conducted using theoretical models. However, these models must be validated with empirical data collected in situ. This study proposes a new measurement methodology that enhances the accuracy of the estimated fields in the water column. The new methodology employs two fluxgate magnetometers operating simultaneously: one stationary near the cable and the other moved around to map spatial variations. The stationary magnetometer thus serves as a reference. Changes in the magnetic field recorded by the stationary fluxgate can be attributed solely to variations in the electric current flowing through the cable. The advantage of this configuration is that it enables linear corrections of changes in the cable current during measurement. Consequently, data from the moving fluxgate can be adjusted according to the fluctuating current. This methodology will produce corrected data suitable for modelling where the current is assumed to be constant. The methodology was tested in situ on a High Voltage Alternating Current offshore wind export cable. Additionally, it was observed that there were two contributions to the observed magnetic field: the magnetic field from a balanced load that attenuates effectively with increasing distance and the magnetic field generated by an unbalanced load that decreases more slowly and, as a result, influences a larger volume.

Assessment of tidal stream power’s ability to enhance energy system resilience

Daniel Coles — 2026-07-31

Results are presented from energy system modelling of the GB grid that investigates the impacts of tidal stream turbine deployment within a future energy scenario. The energy system is stress tested using 2021 as a case study year, when wind resource was lower than average, and gas prices were relatively high. Results show that the inclusion of up to 5 GW of tidal stream capacity, in place of the equivalent offshore wind capacity, results in a 20% reduction in the dispatch of combined cycle gas turbine (CCGT) generation. This is approximately equivalent to a 1 TWh reduction in CCGT dispatch per 1 GW of tidal stream capacity installed. This reduced reliance on CCGT reduces both the total dispatch cost, as well as emissions, by 6.5%. The inclusion of up to 5 GW of tidal stream in place of offshore wind exhibits a reduction in the curtailment of solar PV, offshore wind and tidal stream by 12.5%, 9% and 12.7% respectively. There is also a small but not insignificant uplift in the load factor of all battery storage capacity, of up to 3.5%. These positive system impacts should be balanced against the significant cost premium that tidal stream exhibits relative to offshore wind. Further work is needed to establish the significance of these results in the context of all relevant costs.

Experimental study of a quadrirotor twin vertical axis tidal turbine behaviour under regular waves

Saouli — 2026-07-31

The consideration of the environmental conditions on the power output of vertical-axis tidal turbines (VATT) is a key aspect in assessing their in-situ performance and ensuring stable energy production, as well as a satisfactory lifespan. This study presents an experimental analysis of the surface waves effect on the mechanical response (power and torque fluctuations) of a quadrirotor VATT. Tests were conducted in Ifremer's wave-current flume tank on a 1:20 scale model.
The results highlight a significant increase in power fluctuations under regular waves, particularly near the optimal operating point.
Moreover, the phase-averaged modelling of the wave-induced torque variations reveals a strong relationship between wave-induced velocity fluctuations and torque response.
A parametric model, inspired by Morison’s equation to represent the inertial effects of waves on the machine, effectively captures the wave-related torque contribution. The proposed method thus aims to distinguish wave orbital velocity effects to the turbulence-induced fluctuations.

Controlling tip vortices and cavitation with a grooved-tip design for tidal turbines

Yabin Liu — 2026-07-31

Cavitation can result in blade erosion, vibration, and cavitation noise due to bubble collapse. Tidal turbines' blade tips experience the highest flow speed, and thus, risks of cavitation increase due to low pressure inside tip vortices at high Tip Speed Ratios (TSRs). This can cap their power efficiency and lead to an upper TSR limit. The present work focuses on controlling tip vortices through a novel approach: tip permeability achieved by a grooved tip design. A blade-resolved Reynolds-Averaged Navier-Stokes simulation has been carried out on a model-scale horizontal-axis turbine. In our work, the simulation results have been validated with existing experimental data from the UK Supergen Benchmarking turbine and our wing tip vortex measurements in a water tunnel. We modelled a porous zone placed over the blade tip section, demonstrating that there is an optimal permeability that can substantially reduce the tip vortex intensity and associated pressure drops, and thus mitigate the risk of cavitation. Building on this conclusion, in this study, we have developed a novel design with multiple grooves distributed along the blade tip chord, resulting in an equivalent local 2D permeability. The spanwise scope of the porous or grooved zone is 0.1\% of the turbine diameter. It is found that the grooved tip design can significantly increase the minimum pressure coefficient at the tip vortex core by up to 27\% at a TSR of 6. We also explored different groove channel designs, either by pitching the grooves or making them convergent. We found that, although the effects remain significant and relatively consistent across all design types, the tip vortices are most effectively suppressed when the groove channel has a convergent shape. This promising outcome suggests a substantial reduction of the tip vortex cavitation risks and can thus enable turbines to operate at higher TSRs. Additionally, as the spanwise extent of the permeable tip is minimal, the impact on the turbine's power and thrust coefficients is slight.

Modular electrical generator power take off system for wave - MEGA WAVE PTO

Markus Mueller — 2026-07-31

A wave energy device operates in a wide range of sea states from low load to 4 to 8 times rated load over a wide speed range. Existing PTOs combine mechanical speed enhancers with conventional high speed electrical generator and power converter, with questions over reliability and cannot operate over wide operating ranges. The EU funded MEGA WAVE PTO project is addressing this challenge by developing an all-electric power take off incorporating three sub-systems: a contactless magnetic gear; the modular C-GEN generator; and modular power electronics. The rationale for the technology choice for the all electric power take off is summarised to provide context. An outline of the methodology is presented through six main themes ranging from engineering design, control and testing, to levelized cost, carbon footprint and supply chain analysis, all with the main aim to demonstrate a scalable, reliable and maintainable fully integrated all-electric modular PTO system customized for wave energy devices from kWs to MWs across the Blue Economy sector. Preliminary work from two deliverables completed in the first year are presented to show the design of a 1000 Nm magnetic gear prototype, and a framework for life-cycle assessment of wave devices to understand the potential impact of MEGA WAVE PTO on carbon footprint.

Multiparametric optimization of the middle vanes of a counter‐rotating axial impulse turbine for Oscillating Water Column devices

Aitor Vega-Valladares — 2026-07-31

Oscillating Water Column devices have been historically one of the most studied Wave Energy Converters. Despite the existence of other alternatives, bidirectional turbines are the most widespread solution to take advantage of the characteristic bidirectional air flows in these devices. This category mainly includes Wells and impulse turbines. M. E. McCormick introduced the counter‐rotating impulse turbines in 1978. Unlike the aforementioned, these specific impulse turbines mount two counter‐rotating rotors. Thus, the downstream rotor is able to harness the kinetic energy at the output of the upstream rotor. These turbines traditionally achieved poor efficiencies at low flow rates due to the misalignment of the flow between rotors. More recently, the introduction of a row of Middle Vanes between the two rotors was proposed in order to overcome this drawback. In this work, a CFD based optimization of the Middle Vanes of a counter‐rotating axial impulse turbine is presented. The Mixing Plane technique was used to simulate the relative movement of the blades. Three geometric parameters used to define the shape of the Middle Vanes, as well as the number of them, were considered as Input Parameters for the optimization. Meanwhile, the total‐to‐static efficiency reached by the turbine at a flow coefficient of 1 was set as the only Output Parameter to maximize in this multiparametric and single‐objective optimization, this leading to a 1.2% improvement in terms of peak efficiency.

Preface to the special issue sections of the 16th EWTEC 2025

Luís Manuel de Carvalho Gato — 2026-07-31

The 16th European Wave and Tidal Energy Conference (EWTEC 2025) was organized by the University of Lisbon and held in Madeira from 7-11 September 2025.