Guest Blog: npower’s Wayne Mitchell on marine energy

UK cresting the marine hydro wave As an island nation sandwiched between the immense Atlantic Ocean and the turbulent North Sea, the UK clearly has an abundance of marine energy […]

UK cresting the marine hydro wave
As an island nation sandwiched between the immense Atlantic Ocean and the turbulent North Sea, the UK clearly has an abundance of marine energy resources. You only have to visit the coast to see mile after mile of free energy potential washing over the shore, even on a calm day.

And it’s perhaps because of our country’s historical relationship with the sea that the UK currently leads the world in marine energy development too.

Marine and tidal power technologies include an incredibly diverse range of concepts, but generally fall into a number of broad groups.

Wave power takes advantage of either the vertical or linear motion of waves to drive mechanical, air or water displacement devices, which in turn rotate pumps or generators. Tidal stream technologies sit in stream and frequently, though not always, resemble underwater ‘wind’ turbines.

There are also a number of tidal barrage technologies. In a basic set-up, here the rising tide is allowed to enter an enclosure. Sluice gates are closed retaining a ‘head’ of water and, once the tide has ebbed, the flood water is released through a conventional hydropower turbine.

Given that water has a density of around 800 times that of air, it is easy to imagine the sort of numbers involved should this energy be effectively harnessed to generate electricity.

Potential for 5% of UK power from Severn Estuary
For example, proposals for a power generating barrage across the Severn Estuary to harness one of the world’s largest tidal ranges, some 14 metres, have been mooted for well over a century. A recent Severn barrage concept – subsequently rejected largely on environmental grounds – would have supplied around 5% of the UK’s total electricity requirements alone if completed.

What’s more, the predictability of the tides and the regularity of waves allows more effective power supply planning, and even a degree of load-following in the case of tidal barrage schemes.

While major infrastructure projects such as tidal barrages do present potential engineering and environmental challenges, it’s worth bearing in mind that the world’s oldest and arguably most successful tidal power scheme is a barrage type. The La Rance Estuary in France is the location of a 240 MW plant, which has been operating since the mid-1960s.

Minimal visual impact

Marine and tidal hydropower also benefits from a generally low visual and environmental impact. Typically marine wave devices ride low in the water without any significant superstructure. Tidal machines are usually subsurface and, again, have a minimal surface profile when compared with alternative renewable energy resources, such as wind power.

Given the evident opportunities, it’s encouraging to know that the UK is taking steps to harness these natural resources. Indeed, a number of recent announcements indicate that the technologies that will exploit this surfeit of energy are continuing to receive both private and state support as they close in on commercial maturity.

Investment flowing in
For example, technology company Minesto has been awarded £500,000 by the Department of Energy and Climate Change to extend trials of a quarter-scale version of its Deep Green tidal stream device. Financed as part of the Energy Entrepreneurs Fund, the trials will take place in the Strangford Lough off Northern Ireland.

The world-leading European Marine Energy Centre testing facility off Orkney has also recently received additional support. The Scottish government announced finance through its Marine Renewables Commercialisation Fund to further develop a site research and characterisation platform for high-energy marine environments.

In another recent development, Finnish energy company Fortum is taking advantage of the UK’s testing facilities to lease one of the four development bays at the Wave Hub installation off Cornwall. Wave Hub provides an offshore grid electrical connection some 16 km off the coast. It enables in-situ power generation trials to take place for arrays of wave energy devices of up to 10 MW of cumulative capacity – a world first for the UK.

With investment flowing into the sector, there have been significant advances. Today a number of machines are in the advanced stages of pre-commercial trials, having seen several years of operational history.

Of course, it’s not just the UK that is investigating this potential. The US, Australia and South Korea are just a few of the countries also developing marine energy technologies.

Nonetheless, with the UK offering class-leading testing and development facilities, as well as a superb range of energetic marine environments, it is heartening to see marine engineering and a pioneering spirit once again presenting this country with a new opportunity for growth and jobs. And not just that, now the seas that surround us offer the promise of clean energy too.

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