Function
Removal or making safe of offshore infrastructure at the end of its useful life, plus disposal of equipment.
What it costs*
The decommissioning of a 1 GW offshore wind farm will cost around £426million (gross, excluding any resale value of equipment removed).
Who supplies them
Contractors will be similar to those used for installation.
Likely also other offshore operators will enter the space, including players with offshore oil and gas decommissioning experience who will not get involved with new product installation.
Key facts
At the end of the nominal design life of an offshore wind farm, there are a number of options:
- Extend the operational life of existing assets through a programme of risk assessments, inspections, addressing regulatory aspects, and some component replacement.
- Repower the site with new (larger) turbines, likely meaning decommissioning of existing turbines, foundations and array cables, with the possibility to extend the life of electrical transmission assets. The MW rating of the wind farm and transmission system may be unchanged as the area of the wind farm and density of turbines (MW installed per square km) are likely to be unchanged.
- Fully decommission the site.
Properly financed decommissioning plans typically are required as part of gaining planning approval to construct the wind farm. In practice, permission is likely to be sought to deviate from decommissioning plans as the sector matures decommissioning techniques. UK Government acts as decommissioner of last resort so is ultimately responsible. As a result, it takes security for decommissioning.
Turbine decommissioning will require complete removal of the structure. For nacelle and tower components, the potential for recycling is considerable. There is no current process for recycling composite materials such as those used in the blades and nacelle cover, but is likely that methods will emerge by the time a large volume of offshore wind turbine commissioning is required.
The process for foundation decommissioning will depend on the technology adopted and its sea bed connection.
Decommissioning has only been carried out on a number of small, early offshore wind farms overseas.
Environmental surveys are typically required before and after decommissioning, along with post-decommissioning management of the site in line with the Energy Act 2004.