Includes all installation and commissioning of turbines, offshore balance of plant and onshore balance of plant. This starts with the shipping of major items to the construction port and ends when the fully commissioned assets are handed over to operational teams.

What it costs

About £170 million for a 450 MW floating offshore wind farm. This includes the installation of the turbines and balance of plant, with related offshore logistics. It also includes developer’s insurance, construction project management and spent contingency (not itemised in sections below).

Who supplies them

Companies capable of engineer, procure, construct and installation services (EPCI) for significant installation scopes are expected to include Boskalis, Heerema, Maersk, Saipem, Subsea 7, TechnipFMC and Van Oord.

Installation contractors for smaller scopes are listed in relevant sections.

Key facts

The typical installation process is as follows, noting there are parallel operations where possible:

  1. Offshore substation installation
  2. Offshore cable installation
  3. Onshore export cable installation
  4. Anchor and mooring pre-installation
  5. Floating offshore wind turbine assembly, and
  6. Floating offshore wind turbine installation.

The installation period for a 450 MW floating offshore wind farm is typically three years from the start of onshore works.

Weather downtime is a key cost consideration for any offshore activity with a third of time often lost through waiting on weather.

Significant wave height (Hs) is the most widely used measure of limitation for offshore activity. In practice this needs to be combined with wave periodicity, direction, persistence (the length and frequency of suitable weather windows), wind speed, wind direction and tidal flow to determine workability for different activities.

Sites farther from shore are typically associated with more adverse weather conditions and higher weather downtime.

Weather windows of sufficient duration are required for tow-out and hook-up to moorings and array cable. Hook-up operations at site such as cable pull-in require more benign conditions compared to fixed wind farms, however offshore lifts are avoided as final assembly of the turbine with the floating substructure is completed in port.

The opportunity for innovation to reduce costs is substantial. Decreasing offshore cycle times and increasing the operating range of offshore operations is key as this increases vessel utilisation and accelerates project delivery. Addressing health and safety considerations also needs to remain a focus, as new innovations specific to floating offshore wind are introduced.

Installation services are supplied on a day rate or lump sum basis, principally for the vessel or vessels and the crew and equipment onboard. Additional costs are fuel and harbour dues.

For floating projects, developers may opt for a single foundation and balance of plant installation contract, because of the multiple potential interface risks and that installation processes need to be engineered around the floating substructure design.

Guide to a Floating Offshore Wind Farm