The proposed array was planned to consist of four SeaGen S devices, giving a combined capacity of up to 8 megawatts (MW). Infrastructure including intra-array and export cables, ancillary onshore works and works in the inter-tidal zone was additionally planned to connect the array to the electricity distribution network. Such infrastructure needed to produce grid compliant electricity was contained within the SeaGen system itself, requiring no external power conditioning. This project intended to serve as a test case for the development of the technology, with this particular array operating for up to 25 years.
The SeaGen S system, developed by Marine Current Turbines (MCT), consists of twin power trains mounted on a crossbeam which is supported by a monopole. The cross beam can be raised above the water by winching it up the monopole support structure. Rotor blades are positioned in the top third of the water column and can be pitched through 180 degrees, allowing them to operate in bi-directional flows. Previous trials have shown that the SeaGen S is capable of achieving more than 48% efficiency over a broad range of current velocities. SeaGen S can be deployed in water depths up to 38 metres and achieves rated power in tidal currents of greater than 2.4 m/s. The developers have recently updated the design, giving each machine an operational capacity of 2MW and increasing the rotor diameter from 16 to 20 m.
Foundations: Each device was planned to have either a tripod or quadropod foundation structure with each ‘foot’ terminating in a pin-pile (up to 2 m diameter), drilled and grouted into a rock socket in the seabed. A quadropod structure was considered in the impact assessments throughout the Environmental Statement as a worst case scenario. Each rock socket may have been up to 11 m deep and up to 2.2 m in diameter, providing a worst case seabed footprint of up to 15.2 m2 for each quadropod. The foundations would also support access ladders, J-tubes (to prevent export cable damage), corrosion protection equipment and a boat landing platform.
Export Cables: The array was to be joined in a daisy chain formation using intra-array cabling. The intra-array cables were 33 kV, typically 3-core copper conductors with insulation/conductor screening and steel wire armouring. A single AC subsea export cable rated at 33 kV would have been required to bring generated electricity from the array to the project substation. The export cable would be directionally drilled from the substation location to a ‘break out’ point as close as possible to the array. The cable was planned to have a polypropylene outer sleeve with an external diameter of approximately 140mm, and include internal fibre optic communication links for control purposes.
Onshore Infrastructure: An assessment of the grid infrastructure in the vicinity of the project indicated that the connection options suitable for the project were all on Skye rather than on Scottish Mainland. A small substation containing electrical switchgear (around 6 m x 3 m footprint by 3 m high) was required for the project, which was planned to be housed inside a prefabricated container. Each SeaGen device contained a separate transformer within its structure, so that the onshore substation size could be kept to a minimum.
Kyle Rhea, between the Isle of Skye and the west coast of Scotland.
Sea Generation (Kyle Rhea) Ltd undertook surveys and studies over two years to inform the feasibility and design of the project and the Environmental Impact Assessment (EIA). The EIA was completed and an application for a Marine Licence was submitted to Marine Scotland. An Environmental Statement detailing the findings of the EIA was submitted in support of the application. Marine Scotland conducted a formal consultation process where bodies such as SNH, MCA, Northern Lighthouse Board and RSPB were consulted on the project. The consultation process ran from the 22nd of February 2013 to the 5th of April 2013. Marine Scotland aimed to make a recommendation with regard to the consenting of projects within approximately 9 months. However, the Marine Licence was soon withdrawn by the developer and no futher consent was sought for the cancelled project at Kyle Rhea.
|Section 36 (Electricity Act) Consent||Scottish Ministers||N/A|
|Marine Licence (Marine (Scotland) Act) Consent||Marine Scotland||N/A|
|Licence to Disturb Marine Species||Marine Scotland||N/A|
|Licence to Disturb Basking Shark||Marine Scotland||N/A|
|Town and County Planning Permission||District of Skye and Lochalsh-Highland Council||N/A|
Atlantis Resources purchased MCT’s/Siemens’ portfolio of tidal sites, including Kyle Rhea, in early 2015. However, in March 2016, it was announced that Atlantis would relinquish the Agreements for Lease that it held at two of these sites, Kyle Rhea and Anglesey Skerries in the north of Wales. Ownership of these sites has now been returned to The Crown Estate. Atlantis stated that they wished to prioritise other sites that are currently under construction and closer to reaching financial close.
Key Environmental Issues
The following potential impacts were deemed to be potentially significant during the EIA process:
- The introduction of marine non-native species during construction;
- Destruction, obstruction or damage to otter breeding sites, places of rest or shelter and disturbance or reckless injury and killing;
- Collision risk between marine mammals and the device during operation;
- Mortality or physical injury to fish and shell fish as a result of pollution from routine and accidental discharges during construction and operation.
- Adverse effects on local commercial fisheries due to restricted access to fishing grounds on either side of the array.
- Adverse effects on the local seascape and the costal character of the area.
- Collisions between vessels operating in the area and vessel collision with the array.
Mitigation Measures: The following key mitigation and best practice measures to be applied are outlined in the Environmental Statement:
- Development of an Environmental Management Plan (EMP) to be agreed with the Highland Council, SEPA, SNH and Marine Scotland, following submission of this ES. The EMP will be a working document detailing the environmental actions highlighted in the ES, all activities to be carried out on site, responsibilities for those activities, environmental risks and the management protocols to be put in place to control these, as well as identification of personnel responsible for each element of the EMP;
- An Environmental Monitoring and Adaptive Management Plan (EMAMP), to be agreed with Marine Scotland (MS) and Scottish Natural Heritage (SNH);
- A detailed Construction Method Statement (CMS) and a Pollution Control and Spillage Response Plan to be prepared and agreed with SEPA, SNH and MS-LOT prior to commencement of construction;
- All work will be undertaken to an overarching Health, Safety and Environmental Management System (HSEMS), which will include the CMS, the PIRP and the Environmental Management Plan. The project will be supervised in accordance with the Construction Design and Management Regulations (2007);
- Pollution Control and Spillage Response Plans to be developed and included in the EMP;
- A Construction Traffic Management Plan (CTMP) will be developed in consultation with the Highland Council which will include details of the construction vehicles proposed (size; weight; number of axles); construction programme; swept path analysis, preferred route to access the project site; details of any deflectograph surveys required pre and post-construction, temporary signal control during construction, and protocols for Abnormal Indivisible Loads (AILs);
- Site Waste Management Plan to be developed and agreed with SEPA and Marine Scotland
- Horizontal Directional Drilling (HDD) utilised to reduce or remove the pathway for impacts to many receptors.
- Area of disturbance associated with all works will be kept to a minimum.
- Substation and drilling rig footprints will be sited outside of the SAC and SSSI boundary to reduce impacts on sensitive features; and
- An Environmental Clerk of Works (ECoW) will be appointed, to be present on site and oversee the construction phase. The clerk of works will have responsibility for overseeing the implementation of ecological mitigation measures agreed with the key regulators, SEPA, SNH and Marine Scotland.
Each device was planned to have either a tripod or quadropod foundation structure with each ‘foot’ terminating in a pin-pile (up to 2 m diameter), drilled and grouted into a rock socket in the seabed. A quadropod structure was considered in the impact assessments throughout the Environmental Statement as a worst case scenario. Each rock socket may have been up to 11 m deep and up to 2.2 m in diameter, providing a worst case seabed footprint of up to 15.2 m2 for each quadropod. The foundations would also support access ladders, J-tubes (to prevent export cable damage), corrosion protection equipment and a boat landing platform.
The array was to be joined in a daisy chain formation using intra-array cabling. The intra-array cables were 33 kV, typically 3-core copper conductors with insulation/conductor screening and steel wire armouring. A single AC subsea export cable rated at 33 kV would have been required to bring generated electricity from the array to the project substation. The export cable would be directionally drilled from the substation location to a ‘break out’ point as close as possible to the array. The cable was planned tol have a polypropylene outer sleeve with an external diameter of approximately 140mm, and include internal fibre optic communication links for control purposes.
An assessment of the grid infrastructure in the vicinity of the project indicated that the connection options suitable for the project were all on Skye rather than on Scottish Mainland. A small substation containing electrical switchgear (around 6 m x 3 m footprint by 3 m high) was required for the project, which was planned to be housed inside a prefabricated container. Each SeaGen device contained a separate transformer within its structure, so that the onshore substation size could be kept to a minimum.
Baseline Assessment: Kyle Rhea Tidal Stream Array Project
|Receptor||Study Description||Design and Methods||Results||Status|
|Marine Mammals||Marine mammal survey commissioned to Royal Haskoning||Two vantage points were used which provide optimal views of the majority of Kyle Rhea, and fully encompass the proposed development area. The survey methodology is informed by the SNH draft guidance on survey and monitoring in relation to marine renewables deployments in Scotland.||Grey seal appear to leave Kyle Rhea during breeding season; Harbour seal are present at the site during the breeding season however the number of sightings of juvenile seals (<1 year) was relatively low; Most seals are recorded resting or hauled out close to the shore although they also use the whole of the Kyle, including the proposed array site; <0.5% of the recorded harbour seal behaviour was diving; no grey seals were recorded diving / feeding; Small numbers of harbour porpoise were recorded, most likely transiting through Kyle Rhea; and only 3 basking sharks were recorded.||Completed July 2012 (one year survey)|
|Marine Mammals||Statistical analysis of the year 1 VP survey data by DMP Statistical Solutions.||Year 1 data were analysed to establish: statistical models for marine mammal densities; relationships between available covariates and animal densities; and the power to detect changes in animal densities of various sizes.||There were sufficient sightings of harbour and grey seals to model density surfaces. Harbour porpoise were observed too infrequently to develop density models.||Completed 2012 (using data collected in survey from July 2011 to July 2012)|
|Birds||Bird survey commissioned to Natural Research Projects Ltd.||Vantage point watches, Snap-shot scans and flying bird watches. The survey design took into consideration the draft SNH guidance on survey and monitoring for wet renewable developments.||The results show that, with the exception of shag and cormorant the survey area is generally of low importance for seabirds, waders and wildfowl species. Nevertheless, several species of high conservation value were recorded, but in all cases relatively infrequently and in small numbers.||Completed 2012 (one year survey from July 2011 to July 2012)|
|Physical Environment||Doppler Current Profiler Survey by Partrac Ltd.||Acoustic Doppler Current Profiler use to determine flow rates within Kyle Rhea.||Flood tide = max flow speed of 4m/s, approximately 1m/s faster than the peak flow during the ebb tide. The highest energy flows occurred in the centre of the channel. The area just south of the proposed device locations experienced the highest velocities for the longest duration.||Completed 2012 (time in year not specified in environmental statement)|
|Birds, Physical Environment, Fish, Marine Mammals||Extended Phase 1 Habitat Survey and Otter Survey by Royal Haskoning||This survey used the JNCC methodology for the mapping of habitats and invasive species, and included the assessment of habitats for the presence of protected species. The Otter Survey was undertaken concurrently with the Extended Phase 1 Habitat Survey. The methodology used conformed to SNH guidance.||No features or habitats regarded as being rare or particularly sensitive were recorded during either survey.||Completed 2012 (between 7th and 8th of May and again on 27th of November)|
|Physical Environment, Fish, Invertebrates||Benthic survey commissioned to Envision Mapping.||Drop down video survey to characterise seabed within the study area in terms of: distribution and abundance of marine habitats and communities; identify habitats or species of conservation importance; and determine the substrate type at all locations sampled.||Four species have been identified as being of some conservation importance, namely maerl, spurdog, common seal and sandeel. The substrate type at each of the video sampling stations has been identified and mapped.||Completed (June 2012)|
Post-Installation Monitoring: Kyle Rhea Tidal Stream Array Project
|Stressor||Receptor||Study Description||Design and Methods||Results||Status|
|Collision||Marine Mammals||Active Sonar||To monitor near field behaviour of marine mammals passing close to the devices.||N/A||Cancelled|
|Collision||Marine Mammals||Carcass surveys||Surveys of the local area to identify any washed up marine mammal carcasses.||N/A||Cancelled|
|Collision||Birds||Monitoring studies to quantify changes in the distribution, abundance and behaviour of diving seabirds within the project area||Monitor: cormorant and shag diving behaviour for evidence of avoidance response; foraging behaviour and success of white tailed eagle; and potential benefits to bird species through provision of perches on surface piercing towers and any associated with enhanced feeding opportunities.||N/A||Cancelled|
|Displacement||Marine Mammals||Vantage Point surveys||To monitor use and behaviour in the array area.||N/A||Cancelled|
|Displacement||Marine Mammals||Passive Acoustic monitoring||To monitor use of the Kyle by cetaceans and ensure passage |
|Habitat Change||Physical Environment||Habitat monitoring||Randomised or stratified randomised visual sampling within Kyle Rhea, using remote methods such as drop video and acoustic seabed mapping.||N/A||Cancelled|