Marine Energy


Marine energy is about harnessing the energy from the sea – including waves, tidal streams and tidal range – to generate electricity.

What is Marine Energy?

Wales has huge potential to assist in the National and International drive to lower our reliance on fossil fuels and move towards a low carbon future through the use of its abundant marine renewable energy resources. Marine energy involves harnessing the energy from the sea – including waves, tidal streams and tidal range – to generate electricity.

Wave Energy

Waves are formed by winds blowing over the surface of the sea. The size of the waves generated will depend upon the wind speed, its duration, and the distance of water over which it blows (the fetch), bathymetry of the seafloor (which can focus or disperse the energy of the waves) and currents. The resultant movement of water carries kinetic energy which can be harnessed by wave energy devices. The best wave resources occur in areas where strong winds have travelled over long distances. For this reason, the best wave resources in Europe occur along the western coasts which lie at the end of a long fetch (the Atlantic Ocean).

A study commissioned in 2006 by Welsh Government concluded that Pembrokeshire has the highest concentration of wave resource in Wales equating to an indicative capacity of up to 5600MW. Pembrokeshire is home to one of the sites identified by The Crown Estate as being suitable for wave demonstration activities.  Located 13km offshore and covering an area of 90km2, the Pembrokeshire Demonstration Zone offers a Mean Wave resource level (annual mean power density) of 19.3kW/m to wave array developers.

Please click here to see a list of the eight main types of Wave Energy Converters (WECs) identified by EMEC.

Tidal Stream Energy

Since tides are predictable and reliable, with tide times varying according to location, tidal energy can offer a near continuous power supply. There are two main types of tidal energy:- tidal stream and tidal range.

Tidal stream energy makes use of the kinetic energy of moving water to power turbines. Tidal streams are created by the constantly changing gravitational pull of the moon and sun on the world’s oceans. Tides never stop, with water moving first one way, then the other, the world over. Tidal stream technologies capture the kinetic energy of the currents flowing in and out of the tidal areas. Since the relative positions of the sun and moon can be predicted with complete accuracy, so can the resultant tide. It is this predictability that makes tidal energy such a valuable resource.

Tidal stream resources are generally largest in areas where a good tidal range exists, and where the speed of the currents are amplified by the funnelling effect of the local coastline and seabed, for example, in narrow straits and inlets, around headlands, and in channels between islands. Tidal Energy Limited’s Delta Stream project was the first tidal stream project to be deployed in Wales and is located off Ramsey Island, Pembrokeshire. Tidal streams around the west of Ramsey Island and within Ramsey sound can each up to 4ms-1 providing an indicative capacity of ~150 MW. The Morlais Demonstration Zone has been designated by The Crown Estate for the deployment of tidal energy devices.

Please click here to see the six main types of Tidal Energy Converters (TEC) identified by EMEC.

Tidal Range Energy

Tidal range energy makes use of the potential energy in the difference in height (or head) between high and low tides.

Artificial tidal barrages or lagoons may be constructed to capture the tidal range. Turbines in the barrier or lagoon generate electricity as the tide floods into the reservoir; water thus retained can then be released through turbines, again generating electricity once the tide outside the barrier has receded.

The proposed Tidal Lagoon Swansea Bay one of the world’s first, man-made, energy-generating lagoons, with a 320MW installed capacity and a potential 14 hours of electricity generation every day, producing enough to supply 155,000 homes (equivalent to 90% of Swansea Bay’s annual domestic electricity use) for 120 years.


Floating offshore wind (FLOW) projects involve turbines mounted on floating structures tethered to the sea bed, meaning electricity can be generated in water depths where fixed-foundation turbines are not feasible but wind speed is typically higher and more sustained.

In a recent report, the Offshore Renewable Energy Catapult has advised that there could be as much as 50GW of electricity capacity available in the Celtic Sea in Irish and UK waters. It is estimated by the Catapult that the first GW in the Celtic Sea could potentially deliver over 3,000 jobs and £682m in supply chain opportunities for Wales and Cornwall by 2030. Opportunities for floating wind are currently progressing in Wales with the 96MW Erebus project led by Total and Simply Blue Energy announced in 2020, their follow on 300MW project Valorous and plans for the Pembrokeshire Demonstration Zone to co-locate floating wind and wave technology.

Image credit: Principle Power / Dock 90