UK study maps out complex tidal flows around ‘world’s most powerful tidal turbine’

A team of scientists from the Marine Biological Association, the University of Plymouth, and the University of the Highlands and Islands (UHI) Shetland have analyzed how Orbital Marine Power’s O2 turbine interacts with Orkney’s powerful currents, providing insights into the optimal placement of tidal stream turbines, and highlighting the need of site-specific assessments.

According to the Marine Biological Association, the findings emphasize that the turbulent flows surrounding tidal devices, such as Orbital Marine Power’s O2 turbine, can impact the device and its performance, as well as the surrounding environment. The research further highlights the importance of real-world data in bridging the gap between simulations and actual field conditions.

Using aerial drones and boat-based surveys, the team mapped out the complex tidal flows around the O2, described as “the world’s most powerful tidal turbine”. Unlike conventional designs, the O2 floats on the sea surface and is anchored by mooring lines to the seabed, noted the Marine Biological Association.

The study also showed how tidal flows exceeding eight knots could influence the turbine’s efficiency and revealed that the wake downstream of the O2 could impact the placement of other turbines and marine habitats. 

“Conducting oceanographic surveys in one of the world’s most powerful tidal streams, where currents can exceed 8 knots, is both exhilarating and challenging. Yet collecting data in these turbulent environments is crucial for addressing some of the complexities the tidal energy industry faces today. The optimal placement of these turbines in narrow channels fringed by islands is a complex endeavour, but our novel methods provided robust insights into these turbulent flows and wake signatures,” said Lilian Lieber, Research Fellow at the Marine Biological Association. 

A previous study by the lead authors found that tightly packed turbine arrays could restrict the movement of marine life, reinforcing the importance of environmental assessments for future tidal installations, noted the Marine Biological Association. The assessments are said to be important, because tidal energy is poised to become a more significant part of the UK’s clean energy mix, with previous research suggesting it could meet up to 11% of the nation’s electricity needs.

Shaun Fraser, Senior Scientist and Fisheries Lead from UHI Shetland added: “This study showcases the benefits of combining scientific expertise and deploying new technologies so that significant progress can be made in understanding dynamic tidal environments. With further development of marine renewable energy infrastructure in the Highlands and Islands region likely in the near future, this work is more relevant than ever to local industries and communities.”

According to the Marine Biological Association, tidal energy faces challenges such as high scaling costs, grid connection issues, and ensuring turbine durability in turbulent conditions. The study tackled these obstacles by advancing field measurement techniques important for long-term reliability and sustainable development of tidal technologies.

“Whether it is floating offshore wind farms in the Celtic Sea or tidal turbines off the coast of Scotland, we are going to see more offshore renewable energy platforms being installed all around the UK coastline over the coming decades,” noted Alex Nimmo Smith, Professor of Marine Science and Technology from the University of Plymouth.

“However, the natural conditions in the waters around the UK are incredibly varied and complex, something that it is impossible to fully replicate in controlled laboratory experiments or computer simulations. This study demonstrates a cost-effective means of countering that, and if we are to get the greatest benefits from the clean energy revolution, assessments that factor in real-world environmental conditions will be of critical importance.”

The Orbital O2 2 MW turbine features a 74-meter-long cylindrical floating steel superstructure. This structure contains power conversion and auxiliary systems and supports two leg structures with nacelles attached at their ends.

Orbital Marine Power’s first O2 machine is deployed in the waters off Orkney, and it has been exporting electricity to the UK grid since July 2021. It completed operational financing in 2022 and is expected to offset around 2,000 tonnes of CO2 per year and power 1,700 homes.

Recently, Orbital Marine Power signed an agreement with the marine classification society, Lloyd’s Register (LR), to initiate the certification process for the tidal energy converter (TEC).