By the early 2020s MeyGen Limited intends to deploy up to 398MW of offshore tidal stream turbines to supply clean and renewable electricity to the UK National Grid.
A great deal of investigation work has been carried out over the past few years, and whilst the project is still at an early stage of development it is proposed that the turbines be installed in a series of phases. Phase 1 will consist of a maximum of 86 turbines (86MW). Employing a ‘deploy and monitor strategy’, the initial array deployed in the first two years will provide information on the interactions between the array and the environment and increase the understanding for subsequent phases. Phase 2, comprising the build out of the remainder of the project, will be subject to a separate consent application.
One of the key reasons for this phased approach is that before installation can begin on such large commercial arrays, the installation and operation of the technology must be proven on a smaller scale.
Engineering design and environmental assessments have concentrated on Phase 1 of the project. Below is a summary of the key design aspects of Phase 1.
Turbine technology & testing
Testing of individual prototype turbines is already underway in European waters but, whilst these one-off installations are vital, they cannot satisfy the industry-wide need to understand the additional challenges posed by the combination of multiple turbines in an array.
Understanding that the project needs to prove concept, MeyGen intends to deploy a demonstration array of up to 6 turbines in the Inner Sound as a precursor to the subsequent development of the remaining lease area. Should the project receive planning consent via Marine Scotland the demonstration array will function as a proving ground for up to two turbine designs and all the associated balance of plant, both onshore and offshore. In this phase, the equipment design and integration will be tested in the target environment, and invaluable lessons will be drawn from the construction, installation, operation and maintenance of the project.
The Inner Sound where the MeyGen project is located is recognised as a highly active site in terms of tidal flow and high wave frequency and we have been working closely with turbine technology developers including Atlantis and Andritz Hydro Hammerfest to ensure that the technology deployed can operate and perform in it. We have made excellent progress in the last year towards achieving this. Atlantis has a conditional agreement to supply turbines to the project however, we have ensured that the project design is flexible enough to accommodate other equipment supplier designs also should the project need to.
Each Phase 1 turbine will have its own dedicated export shore to shore. Cables will be brought to shore via horizontal directional drilled (HDD) bores through the bedrock. Cables will be brought to shore and terminated in the Power Conversion Centre (PCC) (see next heading). At the Power Conversion Centre the electricity is transformed up to higher voltages for export to the national grid. All onshore cables will be buried.
MeyGen has secured a 15MW connection to the local distribution network managed by Scottish Hydro Electric Power Distribution plc. (SHEPD). This connection will be provided at the PCC site. MeyGen has also secured a further connection to the high voltage transmission network with Scottish Hydro Electric Transmission Ltd. (SHETL). The connection will provide enough capacity to cover a large proportion of the remainder of the Project.
Onshore Power Conversion Centre
The onshore Power Conversion Centre (PCC) will comprise of a control building for the monitoring of the turbine array and 3 Power Conversion Unit Buildings (PCUBs); each housing power conversion equipment, switchgear and transformers.
Each PCUB will be a maximum of 45m long, 30m wide and 13m high. The PCUBs have been designed following consultation with The Highland Council and Scottish Natural Heritage and has had due regard to the North Highland Onshore Visioning work.
The PCUBs have been designed to modern functional industrial buildings that also satisfy the landscape, and historic environment interests.
Environment Impact Assessment
As part of the consenting process for Phase 1, MeyGen carried out an Environmental Impact Assessment (EIA). The EIA process identifies the areas of the project where significant environmental effects may occur and outlines mitigation measures or management techniques aimed at reducing or offsetting these effects.