MeyGen Phase 1A Tidal Turbine Support Structure
Robert Bird Group
Inner Sound, Pentland Firth, Scotland, UK
OFFSHORE INSTALLATION CONTRACTOR: James Fisher Marine Services
TURBINE SUPPLIER: Atlantis Resources Corporation
TURBINE SUPPLIER: Andritz Hydro Hammerfest
TSS FABRICATOR: Global Energy Group
BALLAST FABRICATION: JGC
CABLE SUPPLY AND INSTALLATION: JDR
Robert Bird Group designed the Turbine Support Structures for Phase 1A of the MeyGen project. Four turbines are installed off the north coast of Scotland, together supplying 6MW rated capacity to the grid. This is the first stage of the planned 398MW MeyGen tidal turbine farm, and is the first project of its kind anywhere in the world. Sitting in 30-50m of exposed fast flowing turbulent waters where the Atlantic meets the North Sea, the steel tripod gravity foundations have been designed from first principles to enable year round turbine operation over a 25 year life with no maintenance.
Between the extreme northern point of Scotland and the island of Stroma lies the Pentland Firth. Here the tide flows from the Atlantic to the North Sea and back again twice a day. The narrow passage produces powerful tidal races in the shallow water with average speeds of over eight knots. These are ideal conditions for building a tidal turbine farm. Maygen Phase 1 is the world’s first utility scale tidal turbine array. Its four 1.5 MW turbines, which are now in place and delivering energy to the grid, are the first stage of a 398 MW turbine farm.
The design of the turbine support structures has been carried out by Robert Bird Group.
The seabed is irregular and the flow is highly turbulent, and the site is exposed to Atlantic storms with wave heights of 15 metres. The combined effects of this energetic marine environment produce very powerful hydrodynamic forces on the turbines and their support structures. Methods of holding the 15-metre-high turbine support structures in place were investigated, and it was decided to use a gravity base. The tripod structure is 25m by 20m in plan and weighs 158 tons. Each of the three legs is held down by 200 tons of ballast. The design had to allow for putting these large structures in place in the 45 minutes of slack water between the tides. This is a great contribution to the development of “green” energy, and the battle against climate change.