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.
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.
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.
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.
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.
