There are a variety of challenges associated with the deployment of wave and tidal devices offshore. The most significant of these include the inherently hostile environmental conditions on site and therefore severely limited periods of safe working for installation.

The high tidal flow velocities experienced at tidal device installation sites may limit the period of safe working subsea to less than one hour in each tidal cycle. For wave devices, the wave height at the installation site may exceed the safe operating limit of standard installation vessels for a significant fraction of the time. This has the potential to introduce costly weather delays to the installation andcommissioning phase. Project developers and device manufacturers are working to develop methods to minimise complex and weather-dependent operations that must be carried out offshore.

A further challenge is presented by the variation in device designs currently available. There are not yet broadly defined methods of installation that are consistent across several different device types. Installation of tidal devices may require specialist dynamic positioning (DP) vessels to overcome the tidal currents during installation and hold position between tides.  Installation of wave devices may be more straighorward, for example if they can be towed to site and moored using relatively standard methods and readily available vessels.

The use of jack-up vessels may be required for installation of some devices but project developersand device manufacturers are seeking alternative methods – e.g. float-out-and-sink operations. Where piling is required, novel tooling may be used to enable drilling and installation in a single operation.

The number of first tier suppliers able to manage and deliver safe, timely installation of expensive and relatively delicate technology in the tough environmental conditions is presently quite limited. Complete packages of work will exceed £100 million for some projects and these are likely to be awarded to specialist organisations with a strong balance sheet.

At the same time, however, opportunities may also exist for smaller companies. Engagement may be through first tier suppliers employed to manage the delivery of the work. Local knowledge, understanding of conditions and access to labour may be key benefits offered by small suppliers.

The build-out schedule suggests there could be a significant step up from small scale installation (project phases with capacities of 10MW order) in 2013-15 to large scale installation (capacities over100MW) from 2016 onwards. Such a step would require suppliers to move from low volume to high volume techniques, requiring more storage and assembly space as well as more efficient installation methods.

To view further detail please read the  Content Source: The Crown Estate, May 2011 – Wave and Tidal energy in the Pentland Firth and Orkney waters: How the projects could be built.