Offshore wind is widely considered to be the most mature of the offshore renewables industries, and features in the current and planned energy mix of many countries. A drive to reduce costs, improve efficiency and go to deeper water with floating structures means there is a real need for reliable and innovative technology.
FEASIBILITY STUDIES AND SITE INSPECTION
Feasibility studies and site inspection include activities such as bathymetric surveys, cable route surveys and UXO surveys. The addition of accurate navigation and positioning instrument can improve the quality of surveys significantly. If towed vehicles are used, tracking equipment designed for shallow water use provides essential input to ensure quality data output. Although not currently commonplace, the use of AUVs and other autonomous vehicles brings significant benefits, including reducing vessel movements and improving project timelines. Accurate positioning and navigation systems can improve the output from AUV surveys, which can be further enhanced by the use of systems designed specifically for those platforms.
Whether undertaking cable lay operations or installing foundations, there is a requirement for highly accurate and robust monitoring of the position of structures and cables. Depending on the application, USBL or LBL may be deemed more suitable. Higher accuracies can be achieved by adding AHRS and precision enhanced with INS. As sites move to deeper waters further offshore, the additional of subsea acoustics to support dynamic positioning operations may be required.
OPERATION AND MAINTENANCE
Maintenance tasks carried out by divers and ROVs can be enhanced by the addition of tracking and underwater positioning. Not only does this improve diver safety, as teams of divers can be tracked using one system and both relative and absolute positions are known, but points of interest can be logged with accuracy, creating a clear audit trial for future reference and making it easier to return for subsequent work.
There are various options for undertaking scour surveys or subsea infrastructure inspections, including sonars, laser and LIDAR. The addition of highly coupled and precise navigation systems and software can upgrade subsea laser or LIDAR systems from static to mobile. This significantly enhances the capability of these systems, permitting extremely rapid but detailed surveying of subsea structures. An alternative is the use of force multipliers such as AUVs. Although in its infancy, the use of AUVs for regular inspection activities offers the benefits of reduced operational costs and minimising the use of divers.
Monitoring of structural weak points such as cables exposed to wave and tide action can be challenging to achieve in the highly dynamic and space limited environments. Wireless monitors that can transmit data in real time or near real time using underwater telemetry offer significant benefits and make retrofitting easily.
FLOATING OFFSHORE WIND
The growth of floating offshore wind farms brings new challenges to the wind industry, including the development of new structural designs, anchoring and integrity monitoring. In deeper waters, wireless systems with integrated subsea telemetry to send data back to surface remove the need for subsea intervention by divers and ROVs, thus improving safety and reducing operational costs.