Abstract
The UK has outlined an ambitious plan to cut carbon emissions by 68% by 2030, shifting its energy sources from fossil fuels to renewable energy alternatives (BEIS, 2022). Tidal stream technology, the process of harnessing the power of ocean tidal currents, is a reliable source of renewable energy and presents a promising option to support this clean energy transition.
While this technology is reaching the point of commercial-scale deployment, the growth of the sector has been hindered by economic challenges, and uncertainties surrounding potential environmental impacts on marine habitats and species during construction and operation. In the UK, there are consenting concerns on the negative impacts tidal stream devices may have on marine fauna, including the risk of collision, disturbance caused by underwater noise, avoidance and displacement. These concerns have contributed to long consenting timelines and the need for costly long-term data collection to fill evidence gaps and understand these impacts.
The aim of this data summary is to provide an overview of environmental monitoring data collected to date on operational or decommissioned tidal stream energy projects in the UK and globally, to assess the impacts these devices may have on marine species. The data and evidence summarised in this report primarily explores the issue of collision risk for marine mammals, as this risk remains a significant barrier to tidal stream consenting and a key concern for regulators. This project’s purpose is to recognise what data has been collected to date, draw insight from monitoring, and how monitoring conclusions can inform future tidal stream energy developments in the UK. A primary objective of this report has been to assess monitoring methods used at tidal stream sites, with a particular focus on impact monitoring techniques, in order to better understand the evidence base relating to collision risk and possible displacement. By providing clarity on the advantages and limitations of tidal stream technology monitoring techniques, the report’s ultimate aim is to support the tidal stream energy consenting process.
Utilising The Crown Estate’s Marine Data Exchange and third-party peer reviewed journals, this report summarises monitoring data for four tidal energy sites in the UK; SeaGen Unit, Shetland Tidal Array, MeyGen Tidal Energy Project and the European Marine Energy Centre, summarising publicly available information on their potential impacts on marine fauna. While focusing on UK case studies, this report also considers evidence that has been gathered around the world to investigate lessons learned in other countries including: the United States of America, Canada and France. The breadth of sites covered in this review showcases the data gathered across the UK and globally, highlighting the existing evidence base for developers and regulators to utilise. Each case study provides insights into the advantages and limitations of monitoring techniques carried out at each location. Marine mammal monitoring techniques that were explored in this report include: Pinniped (seal) telemetry; Passive Acoustic Monitoring; underwater video footage; active sonar; and visual surveys, as well as sound measurements to assess underwater noise levels at the turbine site both during construction and operation phases. Along with this review of selected case studies, The Crown Estate liaised directly with developers to create fact sheets with a high-level overview of each site location, providing details on physical site characteristics and tidal stream device technical details.
In the case studies summarised, which consist of various devices located in differing habitats in Scotland and Northern Ireland, there have been no recorded marine mammal collisions with tidal turbines, and individuals appear to avoid turbines when they are operating. While different monitoring methods were used at each site, this does suggest that collision risk potential is low for single and small-scale arrays. Across the SeaGen, Shetland Tidal Array, and MeyGen Tidal Energy Project case studies, four of the reports concluded that there was localised avoidance of the turbine when in operation, similarly suggesting collision risk maybe be lower than previously perceived for single and small-scale arrays. However, larger-scale arrays still warrant further investigation, especially if avoidance and displacement also occur from potentially important areas for marine species’ life cycles.
Through the synthesis of available evidence, this report has evaluated the methods used to quantify risk and has identified that current environmental monitoring methods can often lack standardisation and consistency, with variability in data quality and reliability, making it difficult to compare results across different sites. To address these limitations, the report recommends enhancing the evidence base through the continued development and implementation of advanced monitoring technologies as well as increased collaboration between researchers, policymakers and industry stakeholders, to help share knowledge and best practice, ultimately improving the overall quality of environmental monitoring. Whilst test and demonstration sites provide developers with the opportunity to refine device technology to reach the point of commercial scale up, they also provide a good opportunity to trial monitoring techniques for devices. Advanced technologies such as the use of active sonar and AI to automatically detect marine species in real time, could help to address uncertainties faced due to challenges of collecting nearfield data that previously resulted in the monitoring not providing definitive evidence on absence (or not) of risk.
Despite the growing evidence base on single devices or small-scale arrays, knowledge gaps persist on the potential impacts larger scale arrays may have on the surrounding marine environment which may not yet be observable in the current small-scale deployments. As tidal stream developments scale up, monitoring should take place throughout a phased deployment to evaluate change at a sufficient spatial and temporal scale to assess wider ranging impacts. By utilising technological advancements, leveraging learnings from previous data and evidence collection and encouraging collaboration, the industry can accelerate development, mitigate risks, and enhance the overall performance of tidal stream energy to enable its scale up to commercial sites.
- Based on the insights concluded in this report, the following next steps are recommended:
- Further investment into test and development sites to improve tidal stream energy technological innovations and ensure consistent environmental monitoring techniques
- Deployment and testing of new monitoring technologies such as active sonar, in situ sensors and AI to automatically detect marine species in real time
- Further funding for coordinated strategic research and evidence programmes to address knowledge gaps, particularly regarding the impacts of large-scale arrays
- Improve data sharing between sites to encourage shared learnings to create a larger evidence base for developers and regulators
- Improve standardisation of monitoring methodologies by implementing data standards to reduce effort and time required to aggregate and analyse multiple data sets.
Following the publication of this report, The Crown Estate is set to advance the next phase of work which will encompass the development of a comprehensive data transferability matrix and framework, aiming to enhance the usability of tidal stream data from one site to another. This initiative reflects The Crown Estate’s commitment to supporting the sustainable development of the tidal stream industry by helping to develop a robust data and evidence base, whilst encouraging the use and reuse of data collected from one site to another.