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Feature

Could Isle of Wight be tidal centre?


George Marsh

A plan to install a tidal energy technology evaluation centre on the Isle of Wight has just received a boost with the Council, a keen promoter of the project, setting aside £1 million to start the physical implementation of the plan.

If tidal energy is to be the next wave in renewable energy after wind, then the Isle of Wight off the UK's central south coast is well placed to exploit it. Well placed, that is, both geographically and in terms of its determination to make it happen. Tidal energy is seen as a crucial element of the Island's vision to become self supporting in energy.

Geographically (more precisely hydrologically), the location of the 380 km2 diamond-shaped Island is such as to obstruct the strong tide that flows up and down the English Channel. The Island splits the flow into two components, one passing to the north of the Island through the Solent, the channel separating the Island from the English mainland, and the other passing to the south of the Wight. In each case, because the same volume of water has to flow through a smaller area – in essence a constriction – the flow is accelerated, resulting in fast currents in the Solent and off the southernmost extremity of the Island, St Catherine's Point.

In particular, flows of up to 2.25 m/s (4.5 kts) have been recorded during peak spring tides up to 5 miles off St Catherine's, with peak flows at Neaps being approximately half of this. Since the amount of electricity that can be generated from a tidal stream is proportional to the cube of the tidal velocity, these flows are potentially productive. According to local marine and engineering consultancy MTMC, which carried out an initial feasibility study, the flow at St Catherine's has the potential to yield 2.8-3.8 GWh of electricity per year.

The Isle of Wight Council, well aware of this, is keen to see the Island's tidal resources tapped. Council Leader David Pugh says: “In its tides, the Island has a limitless power source just waiting to be harnessed. What's more, it also has an indigenous industry base capable of supporting such a facility.”

This is the message with which the Council has sought to create interest at national level so that central Government funding might follow. Specific bids for grants from the Regional Growth Fund (RGF) to establish a tidal energy centre have so far been rejected (although Vestas was awarded a RGF grant for work at its Isle of Wight wind turbine R&D facility), prompting the Council to join industry recently in calling for more Government support for tide and wave power.

On a broader level, the UK has seen announcements worth £4.7 billion into renewables, supporting 15,000, in the period April 2011 to February 2012, and more is underway.

But present financial constraints and the notorious difficulty of attracting funds, private or public, to a new and relatively unproven technology (also known as the Valley of Death), are obliging all concerned to proceed in modest, carefully calibrated steps. The Council has committed £1m of its own money to a plan that would see tidal turbines operating at two tidal hot spots, one being a ‘nursery site’ off Fort Victoria at the western end of the Solent and the other, suitable for larger installations, a location off St Catherine's. These would be operated as the Solent Ocean Energy Centre (SOEC), a facility that would enable tidal energy developers to evaluate their technologies under representative operational conditions as part of their development programmes.

A twin-site approach

The initial £1m, which the Council expects be matched by private industry investment as the project develops, will enable work to start on SOEC. So far, the Council has been engaged in protracted negotiations with the Crown Estate over intended options on the two seabed sites. According to Jim Fawcett, the Council Official who is heading up the Island's tidal energy initiative, a formal process for finalising these leases should be completed by September. After that, and subject to further funding input, the project should be able to move ahead.

A first phase, Fawcett tells Renewable Energy Focus, will involve obtaining all the necessary consents and licences, both for the two sites and for associated onshore infrastructure – such as sub-stations and a control and data analysis centre. Only then can work begin on the construction and installation phase, which will see the SOEC become a physical reality. Cost for the entire programme could, it is estimated, be £25-£30m. Of this, some two thirds would be public money, the balance being made up of corporate and private investment.

Each of the two sites would then enable tidal energy developers to ‘plug in’ their turbines or other machines for periods of evaluation. The twin-site approach offers a progression whereby developers can try out their technologies at reduced scale at the nursery site before proceeding to trials at large or full scale at St Catherine's. The sea bed installations would be complemented by a data centre ashore where results would be processed and analysed. Providing performance data in standardised formats will help in assessing the technical and commercial viability of devices.

Connecting machines to the local grid will enable power produced to be sold at commercial rates. Studies have established that the Isle of Wight's electricity network could absorb up to 7 MW of power from external sources, of which about 5 MW could be absorbed in the area of Ventnor, the town nearest to St Catherine's Point.

Complementary to other centres

SOEC is seen as complementary to other UK-based marine energy test centres including the European Marine Energy Centre (EMEC) in the Orkneys and the Wavehub off Cornwall.

Many developers feel that a relatively sheltered and accessible marine site in the south of England with high tidal flows would be useful for short-term testing of tidal devices in an environment that is more aggressive than test facilities ashore, but not so remote and severe as offered by EMEC with its fierce Pentland Firth tides. More of a development facility than an endurance testing centre, SOEC could also be used for testing the installation, performance and maintenance of mooring systems, gravity bases, ground anchors and other ancillary equipment.

Although tidal currents at SOEC are strong, they are not extreme and this would suit the several developers aiming to exploit lower flow rates up to, say 2.5 m/s, rather than 4.5m/s. Moreover, the wave environment there is less arduous than for example at Scotland's EMEC, permitting longer windows for deployment and maintenance. The climate is milder, with longer daylight hours in winter, facilitating work on site.

Workboats and crane barges can be stationed close by in local ports ranging from Yarmouth and Cowes to Southampton and Portsmouth, and travel for engineering personnel is easier. Water depths are adequate, greater than 20 m off St Catherine's, and the connecting distance to shore is manageable. Commercial shipping would rarely intrude into the main St Catherine's site, the shipping lanes being further to the south.

In lobbying central government, the Isle of Wight Council argues that the plan represents not only a major step forward in achieving the Eco-Island vision for the Island to become self-sufficient in power, but also provides a valuable opportunity for the UK to maintain its early lead in tidal power developments. It would also boost the economy in the south east England region. As Stuart Love, the Council's Director of Economy and Environment, says: “We have been working closely with Southampton University to demonstrate that there is the potential off our coast, not only to generate enough power for the Island and more, but also to create 700 jobs in the Solent region and up to 5000 nationally.”

Momentum behind the scheme is building and a number of enterprises have expressed their keenness to participate. Fawcett notes that there is demand from tidal energy developers looking for suitable evaluation sites and facilities. There is now a good chance that local and corporate commitment allied with the obvious tidal energy potential, may impress governmental and industrial officials sufficiently to loosen purse strings and enable the physical construction of SOEC to proceed.

See also: Wave and tidal power – an emerging new market for composites.

About the author: George Marsh: Engineering roles in high-vacuum physics, electronics, flight testing and radar led George Marsh, via technology PR, to technology journalism. He is a regular contributor to Renewable Energy Focus.

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