Marine renewables

DOI: https://doi.org/10.58248/PN625

Marine renewables encompass a variety of technologies, including tidal stream devices, tidal range barriers and lagoons, and wave energy conversion devices. These produce electricity without emitting greenhouse gases, and may contribute to the UK’s net zero greenhouse gas emissions targets. They could also provide economic and industrial opportunities.

Despite several decades of research and development, the only marine renewables projects are demonstration plants. Together these generate a small fraction of UK electricity. Marine renewables are more expensive and at an earlier stage of development than more mature technologies like wind and solar power.

Key points

• The UK has the largest marine energy resource in Europe and has developed a strong R&D base for the technologies since the 1970s. The technologies have high levels of public support but have remained in early stages of development for much longer than initially expected.
• Tidal stream devices often resemble underwater wind turbines and generate electricity due to the motion of tidal currents. Small-scale projects are currently generating electricity and are connected to the grid.
• Tidal range devices operate in a similar way to hydroelectric dams, trapping water behind a barrier as the tide comes in and releasing it through turbines when the tide goes out. Tidal barrages create this barrier across a river estuary, while tidal lagoons artificially construct a barrier out to sea. Although projects have been proposed, such as the Severn Barrage and Swansea Bay Tidal Lagoon, they have been rejected on cost and other grounds.
• Wave energy devices convert energy from the motion of waves into electricity, using a variety of mechanisms and designs. Attempts at commercialisation have so far been unsuccessful.
• Some modelling suggests that when considering technical potential alone, marine renewables (across all technologies) could provide a substantial portion of UK power. However, when considering wider economic and policy developments this is substantially less. National Grid’s Future Energy Scenarios model up to 3% of UK electricity demand being met by marine renewables by 2050.
• Developing a UK marine renewables industry would provide manufacturing and economic regeneration benefits. Advocates for the marine renewables industry point to its high UK supply chain content and geographic proximity to deprived coastal areas.
• Research and development funding for marine renewables has come from a variety of sources, including UK and devolved governments, and EU structural and investment funds. These have helped establish demonstration projects and sites, such as the European Marine Energy Centre (EMEC) on Orkney and the world’s largest tidal stream project, Meygen, in the Pentland Firth.
• Barriers to the development of marine renewables have included high up-front costs, difficulties in engineering and maintaining structures in harsh marine environments, and competition with other forms of renewables for subsidies.
• Although tidal range technologies are more mature, the high up-front capital cost of construction, alongside environmental concerns for tidal barrages, have prevent large-scale projects from being constructed in the UK.
• The costs of wind and solar power have fallen substantially in recent years, making it difficult for less mature technologies like marine renewables to compete for subsidies under the current subsidy policy structure. Although further deployment of marine renewables would likely reduce costs, it is unclear whether they could ever be competitive with wind and solar.
• Advocates suggest that subsidy reform, such as tax breaks for private companies that purchase power from marine renewable projects, or the ability to bid for separate subsidies without needing to compete with solar and wind, could provide a route to market for marine renewables.

Acknowledgements

POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including:

• Dr Noramalina Mansor, BEIS*
• Tim Hurst, Wave Energy Scotland*
• David Jones, Marine Energy Wales
• Dr Stephen Wyatt, Offshore Renewable Energy Catapult
• Simon Cheeseman, Offshore Renewable Energy Catapult*
• Steve Westbrook, economist*
• Neil Kermode, EMEC*
• David Stoddart-Scott, Sustainable Marine Energy
• Sue Barr, UK Marine Energy Council
• Bente Klein, Tidal Lagoon Power*
• Nathan Bennett, Renewable UK
• Ciaran Frost, BVG Associates
• Professor Richard Willden, University of Oxford*
• Dr David Woolf, Heriot-Watt University
• Dr Matt Hannon, University of Strathclyde
• Richard Yemm, Quoceant
• Professor Rod Rainey, Rod Rainey and Associates
• Professor Deborah Greaves, University of Plymouth*
• Dr Stuart Bradley, University of Warwick*
• Anna Stegman, Energy Systems Catapult
• Dr Laura Watts, University of Edinburgh
• Michael McLaughlin, National Grid
• Andrew Scott, Orbital Marine Power
• Martin Edlund, Minesto
• Sam Leighton, Bombora
• Andrew Garrad CBE
• Tim Mundon, Oscilla Power
• SIMEC Atlantis Energy
• Tidal Range Alliance

* denotes contributors who reviewed the note at external review

Correction [10/07/20]: "Several other tidal range projects are in early stages of development.[Reference 88]" was added to Box 1.

Correction [10/07/20]: "They may also protect against flooding in surrounding coastal areas.[Reference 29]" was added under "Tidal range".