GE’s Power Conversion business has been a long time partner with SIMEC Atlantis Energy in building the tidal turbine system MayGen in Scotland, which should end up as a 398 MW generating system. Today it is just 6 MW, and it has slightly adjusted the next phase which is for SIMEC to provide two further turbines, which have now been upgraded from the 1.5 MW AR 1500s planned originally, to two AR2000, which means an additional 4 MW will be released.
These turbines have underwater rotor diameters of between 20 and 24 meters which offers a 2MW output when moving at 3.05 meters per second. It is designed to be the backbone of the entire tidal system eventually.
The turbine is offered as part of a “rotor to grid” tidal generation system, with an array architecture which allows multiple turbines to be connected in parallel, reducing the cost and impact of the subsea infrastructure.
The AR2000 turbine has been in development for two years and builds on the deployment of the firm’s AR1500 turbines at the MeyGen project in Scotland, which began generating power for the grid last year. The new 2MW turbines are expected to be deployed on future phases of the MeyGen project and will be also be available for sale to commercial developers late next year.
The entire project goes back to 2010, when the Crown Estate agreed a lease offshore between Scotland’s northernmost coast and the island of Stroma.
An agreement signed this week between SIMEC Atlantis and GE says they will both engage in joint marketing to promote new subsea connection technologies that they have developed with this project. There is also a preferred supplier agreement with the Power Conversion business of GE which will bring the energy ashore and put it into the grid.
The 3.5 km stretch of sea covers some of the fastest flowing waters in the UK, just 2 km 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 Atlantis 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.
Phase 1 of the project is a precursor to jump to the development of the next 86MW of this project, which should demonstrate that a tidal array is commercially viable and technically feasible.
But there is some heavy lifting involved, as each turbine has to be fixed to an individual foundation weighing between 250 and 350 tonnes, coupled with 6 ballast blocks weighing 1,200 tonnes to 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 drilled borehole within the foreshore bedrock.
The turbines feed into the onshore power conversion unit building at the Ness of Quoys, where the low voltage supply will be converted to 33kV for export via the 14.9 MW grid connection into the local distribution network. On completion this phase of the tidal array will generate sufficient electricity to supply 2,600 homes.
The last part of phase 1 is to build an additional 49 (73.5 MW) turbines at a cost of £420 million, with installation commencing now in 2019. This will create 5,300 full time jobs which will mostly be people repurposed from the oil and gas sector. The idea is to put Scotland into an electricity export market for decades because this electricity should be at such a low Levelized Cost of Energy (LCOE).
Phases 2 and 3 allows for up to 398 MW of tidal stream capacity to be installed in the site although it only has agreed grid capacity for 252 MW at present so would need to upgrade this connection too if it went for the full 398 MW.