| Islay Tidal Energy Project |
Location
The island of Islay in Argyll and Bute lies off the south west coast of Scotland and is the southern most of the Inner Hebrides and fifth largest of all the Scottish islands. It has a population of around 3200 people and is perhaps best known for its malt whisky being home to no fewer than eight working distilleries.
In addition to spectacular scenery and wildlife, the island also features some impressive tidal currents both off the west coast and in the south of Islay, the narrow channel between Islay and Jura.
The Overall Picture
Seawater flows into the Irish Sea on a flood (inflowing) tide from the south through the relatively open expanse of water between the Irish Coast at Wicklow, and the Welsh coast of Pembrokeshire, and from the north between the Antrim coast and the Scottish coast of Argyll and Bute. The northern entry is described and marked on UKHO Charts as the North Channel. The island of Islay lies in the approaches to the North Channel.
The Resource
There are a number of potential tidal energy sites in UK and Irish Waters. The most energetic are well known to be those of the Pentland Firth in the North of Scotland, but other areas have also been identified around Holyhead, Pembroke, the Severn Estuary, the Isle of Wight and the Channel Islands.
The Irish Sea holds a number of these potential tidal energy sites, however, the narrow entry (20km at its closest point) as well as the bathymetry (seabed profile) and coastline topography of the North Channel means that the flows entering the Irish Sea through this route are typically of higher velocity than those found in the southern entry.
Tidal resource alone does not necessarily make a site worthy of development. Sea bed conditions, grid connection options, the presence of other users whether transitory vessels (military, commercial or recreational) or site specific including fishing interests, all need to be considered. Likewise other non human users are a key part of determining whether a site can or should be developed requiring detailed stakeholder consultation with relevant specialist bodies and environmental impact assessments to ensure that their proper interests are also considered.
The Site
The proposed Islay Tidal Energy Project occupies an area of approximately 8km2 and lies around 8km off the south western tip of Islay.
With water depths of between 35 and 50m the sea bed across the site area is relatively flat, with few significant bathymetric features of note and as one might imagine, based on the speed of the tidal flows in the area, the seabed is well scoured and devoid of large sediment deposits or concentrations of resident marine life. It is not an easy place for marine life or the birds and animals that live on it to make a living (and this has been reflected in the results of the surveys undertaken to date). However, clearly it is important that other species that use the space in a transitory manner must also be considered and appropriate surveys undertaken.
Shipping traffic which moves into and out of the Irish Sea from the north Atlantic and onto the major UK and Irish ports navigate through the North Channel by a Traffic Separation Scheme (TSS) incorporating both north bound and south bound lanes (illustrated by the purple corridors on the Admiralty Chart). Whilst these are not exclusion zones, smaller vessels such as recreational vessels (yachts or motor boats) or fishing vessels typically navigate outside these traffic lanes in the inshore traffic zones. Since Islay lies some 30km to the north west of the exit to the North Channel TSS zone the water in which the site is located is relatively unconstrained in a navigational sense for any vessels wishing to make their approach into or out of the TSS.
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For submerged vessels the North Channel also provides the closest exit point for Royal Naval Submarines from the base at Faslane to reach the north Atlantic.
Understandably both of these user groups have interests in preserving access to the sea area and minimising potential navigational hazards and this is the subject of ongoing assessment and consultation.
History and Key Characteristics
DP Marine Energy Ltd (DPME) has been exploring and assessing the potential for developing a tidal energy site off the west coast of Islay since 2007 when it was first identified as a site capable of meeting certain key criteria.
The 2007 objectives in searching for suitable tidal energy sites was to identify sites that were 1) capable of supporting a commercial development (i.e. 100-200MW or more), 2) be as benign as possible for other species and be as remote from environmentally designated areas as feasible (particularly in respect of sea mammals), 3) as close as feasible to a significant electrical load point, 4) with little fishing interest and 5) in relatively unconstrained navigational waters.
A number of sites were identified with various strength and weaknesses on each of these key characteristics. The Islay site met all of these key criteria.
Site Studies to Date
Since Islay’s selection a number of studies have been commissioned in order to characterise the available energy resource and to assess the potential environmental impacts.
Resource: A series of acoustic doppler current profile (ADCP) multi beam devices have been licenced and deployed over the course of the resource assessment. These bottom mounted ADCPs enable current velocities to be measured at various points throughout the water column and to record this information both through the change of tide from flood to ebb but also over the course of the monthly lunar cycle. The devices are also able to measure wave effects on the surface an important consideration in order to determine dynamic surge loading on both the devices and their foundations.
ADCP Device Being Deployed
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In parallel with the seabed deployments ADCP transect work from a moving vessel has also been undertaken at both neap and spring tides to ‘fill in’ the spot data obtained from the fixed ADCPs. This enables a wider area to be characterised and a more accurate picture of velocity variation across the site area to be built up.
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Environment: As is normal for any kind of renewable energy development a preliminary desk top constraints assessment was undertaken to identify and compile all known information in relation to the project and surrounding wider area. This assessment was supported by consultation with various environmental bodies including the Royal Society for the Protection of Birds (RSPB), and Scottish Natural Heritage (SNH). Consultation was also undertaken with local fishing interests, Argyll and Bute Planning Office, and a preliminary presentation made to the Islay Community Council.
Following the preliminary assessment and consultation a number of key assessments have been commissioned:
Benthic assessment a drop down video camera mounted on a weighted grab sampler as illustrated below was used to provide a visual record of 23 locations within the proposed development site. The objective of the multiple sampling was to assess a broad selection of locations across the area and to explore the presence of various sea bed types (e.g. sand, gravel, rock etc) based on observations made of the bathymetric data and chart data.
Drop Down Video Camera Mounted on Grab Frame
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Sample of Biotopes Recorded |
Sea Mammal and Sea Bird Surveys For DPME perhaps one of the most important environmental surveys undertaken has been that of the site usage by sea birds and sea mammals. A two year programme of monthly visual and hydrophone site surveys was commissioned and commenced in November 2009, and despite difficulties in finding suitable weather windows particularly through the winter months, good survey results have been recorded throughout the seasons. The findings to date and 12 month data review are encouraging with respect to the likely minimal impacts on these other users. The cetaceans were harbour porpoises (Phocoena phocoena), bottlenose (Tursiops truncatus) and Risso’s dolphins (Grampus griseus) while the pinnipeds were both of the UK shelf species: common (harbour, Phoca vitulina) and grey seals (Halichoerus grypus). Of the cetaceans the most frequently sighted species was the harbour porpoise.
Rissos Dolphins Spotted off Islay Coast
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Of the 31 species of bird recorded during site surveys seven were commonly present in the survey area. These were These species are fulmar, Manx shearwater, gannet, kittiwake, common guillemot, razorbill and puffin.
Razorbills (image not recorded on site) |
The Project, Process and Programme
Phased Development: The strategic goal of DPME is to develop the Islay Energy Park through a series of phases matched to both technology readiness and grid availability, starting with a 5MW Demonstration project (target 2015) scaling through to a 30MW Commercial scale (2016 into 2017), and culminating in a full scale 400MW Utility scale development around 2019. The first two phases of this plan fall within the award for an agreement for lease of 30MW from The Crown Estate, whilst steps toward the final utility scale phase have been taken both by commissioned all EIA works across the full site area and also by securing the 400MW grid connection with National Grid Ltd.
From a consenting perspective the strategy being adopted and agreed with the environmental bodies has been one of staged/phased consent. By this process feedback from environmental performance monitoring collected on the early phases of the project (and others) is assessed and used to inform the design, and consenting of the latter phases.
Formal Scoping: Following the informal consultation with a number of key stakeholders and other interested parties described above a request for a scoping opinion was issued to The Consents Unit of The Scottish Government in 2009. This formal scoping document and the responses to it from various bodies has formed the basis for the environmental impact assessment (EIA) works and the consultation programme leading up to the application for consent.
Ongoing Works: During 2012 in parallel with ongoing EIA works and consultations with interested stakeholders (e.g. fishing, shipping, MoD etc) a number of further public consultation exercises will be undertaken on Islay and will be advertised both in the press and via the local Community Council or local interest groups. Any interested parties or individuals with questions, concerns or comments are encouraged to contact us via the appropriate numbers or via the dedicated email address islay@dpenergy.com
Application for Consent: Whilst subject to satisfactory completion of all necessary studies and discussions and agreements with key stakeholders the application for consent is currently scheduled for the end of 2012.
The Technology
DP Marine Energy Ltd (DPME) has been awarded a site agreement for a Commercial Lease (“Saltire Prize” lease) from The Crown Estate to develop the 30MW Islay tidal energy site which forms the Demonstration and First Phase Commercial Scale element of the overall project. The technology selected to support this phase has been designed and built by Tidal Generation Ltd (TGL), a Bristol based company and wholly owned subsidiary of Rolls Royce plc. The 1MW turbine to be used is based on TGL’s 500kW turbine first installed in September 2010 at The European Marine Energy Centre (EMEC) in Orkney. The 500kW device achieved ROC accreditation and has recently passed a major milestone of successfully feeding over 100 megawatt hours (MWh) of electrical power into the national grid.
Image Courtesy of Tidal Generation Ltd
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Key aspects of the device which won its selection was the design concept, attention to detail and the product validation strategy adopted by the company which draws Rolls-Royce’s engineering skills and experience in new product validation. Also noted was TGL`s lead role in the Energy Technology Institute’s (ETI) ReDAPT programme (Reliable Data Acquisition Programme Tidal) featuring a range of objectives focused on an accelerated route to successful commercial operation. However, of critical importance was the test experience being gained by TGL at EMEC which is being fed into the 1MW engineering release programme.
Image Courtesy of Tidal Generation Ltd |
TGL 500kW Turbine Deployed at EMEC |
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