Since 2010, as part of the Pentland Firth and Orkney Waters leasing round, The Crown Estate awarded an agreement for lease to MeyGen plc, granting the option to develop a tidal stream project of up to 398MW at an offshore site between Scotland’s northernmost coast and the island of Stroma, as shown in the map below.
The 3.5km site covers some of the fastest flowing waters in the UK, just 2km from Scotland’s north-east tip. To the north of the site is the uninhabited island of Stroma, which creates a natural channel with the mainland to accelerate the millions of tonnes of water flowing between the North Sea and the Atlantic Ocean every day. This site was originally identified by SAE in 2007, following a global review of tidal resource which concluded that the high flows, medium water depths and proximity to the mainland rendered it a prime location for development.
The MeyGen project is the largest planned tidal stream project in the world and is the only commercial multi-turbine array to have commenced construction. The project is split into three phases as follows:
MEYGEN PHASE 1
The first phase of the MeyGen project comprises four 1.5MW turbines installed on gravity turbine support structures. The array is a precursor to the development of the remaining consented 86MW project and will demonstrate that the development of tidal arrays is both commercially viable and technically feasible. Operating since March 2018, the invaluable lessons drawn from the construction, installation, operation and maintenance of this phase (of the project) will be fed into subsequent phases.
Each turbine is located on an individual foundation weighing between 250 and 350 tonnes, coupled with 6 ballast blocks weighing 1,200 tonnes, that provide horizontal stability over the lifetime of the turbine. Each turbine has a dedicated subsea array cable laid directly on the seabed and brought ashore via a horizontal directionally drilled borehole within the foreshore bedrock.
The turbines feed into the onshore power conversion unit building at the Ness of Quoys, where the 4kV supply is converted to 33kV for export via into the local distribution network. This phase of the tidal array generates sufficient electricity to supply 2,600 homes.
The planning consent for Phase 1 includes three power conversion unit buildings, which have been designed in consultation with The Highland Council and Scottish Natural Heritage as modern functional industrial buildings that reflect their landscape and historic environmental context.
Phase 1 incorporates two different turbine technologies (SAE's AR1500 and Andritz Hydro Hammerfest AH1000 MK1), with environmental monitoring equipment installed that assesses the interaction between the tidal turbines and the marine environment, including marine mammals. The results of the monitoring work will be used to inform subsequent phases of the project.
The key milestones achieved to date are:
- Crown Estate Agreement Lease – October 2010
- Marine Licence granted by Marine Scotland – January 2014
- Financial Close/Construction contracts conclude – September 2014
- Construction commences at the Ness of Quoys site – January 2015
- Offshore subsea array cables installed in Inner Sound – October 2015
- Onshore building works complete, and grid connection energised – June 2016
- Offshore installation of foundations and turbines commenced – October 2016
- First electrons exported to grid – November 2016
- ROC and Ofgem accreditation –– March 2017
- 1GWh exported to the grid – August 2017
- MeyGen Phase 1A formally enters 25-year operations phase– April 2018
- Subsea hub installed at MeyGen – September 2020
The supply chain for the Phase 1 project is spread across the United Kingdom, Europe and North America; 43% of the project’s expenditure was in Scotland and involved companies based in Caithness, and Ross and Cromarty.
Subsea Hub deployment
The subsea hub, deployed at the MeyGen site, demonstrates the technology to have multiple turbines connected to a single power export cable. This will significantly reduce the costs associated with grid connection for future projects. The length of power export cable as well as the amount of onshore conversion equipment required for grid connection will be significantly reduced, as will the amount of horizontal directional drilling and the amount of vessel time required for cable installation.
MEYGEN PHASE 2
Status: In development
SAE has full consent, all necessary permissions and grid capacity to install an additional 80MW of tidal stream capacity on the MeyGen site. The project will be transformational for the tidal energy industry, providing the scale to justify the establishment of turbine manufacturing facilities at Global Energy’s facility in Nigg Energy Park.
Status: In development
The MeyGen offshore lease currently permits up to 398MW of tidal stream capacity to be installed within the site. While presently MeyGen only has grid capacity for up to 252MW, the site is capable of supporting the full project buildout.