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Atlantis deploys a 1 MW tidal turbine at European Marine Energy Centre at Orkney, UK. Photo: Green Energy Futures via Flickr.com.
Atlantis deploys a 1 MW tidal turbine at European Marine Energy Centre at Orkney, UK. Photo: Green Energy Futures via Flickr.com.
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All at sea - the UK's policies for wave and tidal power

Godfrey Boyle

7th March 2014

First the UK made a mess of wind and let Denmark take the prize. And now, writes Godfrey Boyle, the government's prevarication is risking our lead in another key renewable energy sector - marine power.

The UK government has pursued a highly confusing policy towards renewable energy in recent years, repeatedly changing rules and prices, causing uncertainty to long-term investors.

Currents of cautious optimism were flowing at the Wave and Tidal Energy conference in Belfast.

Enthusiastic entrepreneurs and academics presented progress reports on the dazzling assortment of devices under development to harness the abundant energy resources from the seas around the British Isles, and elsewhere.

Attention has moved away from tidal barrages like the huge 5,000MW Severn Estuary project, which has so far failed to gain government support. Surprisingly there was no discussion in Belfast of the more modest tidal lagoon project recently proposed for Swansea Bay.

The new focus - harnessing tidal currents

The focus is now on arrays of smaller devices for harnessing the strong tidal currents present around certain coastlines. To date the leading device has been the 1.2 MW SeaGen turbine installed at Queen's University Belfast's test site in Strangford Lough by Marine Current Turbines (MCT).

The SeaGen resembles two, twin-bladed wind turbines mounted on a horizontal beam and driven by underwater currents. Since 2007 it has generated 9GWh of electricity for the grid. The company was recently taken over by the electrical giant Siemens and now plans to install an array of second generation turbines off North Wales in 2015.

Still at the research stage is the Swedish company Minesto's 'Deep Green' technology. This is essentially a tethered, underwater flying kite - a hydrofoil wing incorporating a turbine and electrical generator, coupled to a control system that makes it perform a continuous figure-of-eight pattern underwater.

Because this creates a greatly increased water velocity into the turbine / generator, Minesto claims it can operate in areas with slower currents than required by conventional large turbines such as SeaGen, opening up a much wider coastal area around the world that could provide energy from tidal power.

The company is testing a quarter-scale prototype at Strangford, not far from the SeaGen project, with the aim of progressing towards a 800KW Deep Green machine.

Competing wave power technologies

Among those researching wave energy, there are also many competing technologies. Aquamarine Power's 'Oyster' device is essentially a hinged flap that moves back and forth as waves pass over it. The motion of the flaps pumps hydraulic fluid through pipes connected to an on-shore electrical generator.

Prototypes rated at 300KW have been tested at the European Marine Energy Centre in Orkney, where the company is now testing a next generation 800KW device that would be deployed in arrays of many devices.

Operating on an entirely different principle is Pelamis, whose eponymous device is named after the sea snake. Facing into the waves, rather than across them like the Oyster, the Pelamis consists of five large cylindrical steel tubes connected by flexible hydraulic joints.

As each tube is tilted by incoming waves, the differential movement of each with respect to its neighbours pumps oil through hydraulic motors, which drive electrical generators.

But in both these areas of research and experiment, the Darwinan process that eventually kills off the less successful technologies has yet to finish.

A hard lesson is blowing in the wind

For example, in wind energy the three-bladed, horizontal-axis, upwind turbine emerged triumphant from competing designs demonstrated during the 1970s and 1980s that featured different numbers of blades arranged horizontally and vertically.

Britain built and encouraged various interesting prototypes, including a large vertical axis turbine at Camarthen Bay and an even larger 5MW horizontal axis turbine on Orkney. But these ultimately proved commercially unsuccessful.

Denmark, by contrast, concentrated on building smaller but more commercially attractive turbines in the 200KW range, and now hosts one of the world's most successful wind turbine manufacturers, Vestas.

Renewables and nuclear - spot the difference

The encouraging speech to the conference given by UK energy minister Greg Barker might suggest that political support in the medium term for marine energy in the UK is strong; but the prospects may not be so promising beyond 2020.

Under the UK electricity market reforms currently being implemented, wave and tidal energy, as still-developing technologies, will be offered a high strike price of some £305 per megawatt-hour (MWh) - considerably more than offshore wind at £155 per MWh. But this price will only apply to schemes of up to 30MW, with a contract duration of 15 years.

By contrast, the mature nuclear power industry is being offered 40 year contracts (at £92 per MWh) backed by government-guaranteed loans.

It is debatable whether - despite the high price offered - the short contracts on offer to marine renewables, and an unclear future, will draw in the investment required to make the best use of the seas' potential.

A cloud of government confusion and dither

The UK government has pursued a highly confusing policy towards renewable energy in recent years, repeatedly changing rules and prices, causing uncertainty to long-term investors.

And although the UK currently leads in off-shore wind power, even here recent policy changes have caused several large developers to scale back their plans.

This stands in stark contrast to strong government encouragement for investment in new nuclear power, or in Britain's shale gas and oil reserves from fracking.

Just as it missed the opportunity to be a leading developer of onshore wind power in the 1980s, it seems the UK government's prevarication risks letting Britain's lead in another key renewable energy technology, marine power, slip through its fingers.

 


 

Godfrey Boyle is Emeritus Professor of Renewable Energy at The Open University. He does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published on The Conversation. Read the original article.

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