The Future of Leaner, Greener, and Safer Offshore Wind Survey

The offshore wind industry in the United States took a major step forward in May 2021 with the official Federal approval for the construction and development of the 800 MW Vineyard Wind 1 wind farm off the coast of Massachusetts.

Today, there are many more projects in various stages of development up and down the east coast, from Maine to Virginia, a clear sign that the US offshore wind (OSW) industry is poised for massive growth in 2023 and beyond.

However, the operating costs and practicalities associated with wind farm planning is a major hurdle for developers. Geotechnical and geophysical surveys are traditionally conducted using large survey vessels and work class ROVs, a bottleneck of activity that puts additional strain on ports, harbors, and coastal communities. Furthermore, the environmental preservation of the marine ecosystems found in and around the target sites for development is of mounting concern, and so proposals are often subject to stringent and lengthy permitting processes, which can significantly jeopardize project deadlines.

To meet these challenges, however, operators can now rely on new—and proven—uncrewed technologies like Uncrewed Surface Vessels (USVs) for a leaner, greener, and safer alternative to executing the data-rich marine survey campaigns needed for thorough OSW planning and construction.

UNCREWED SOLUTION

Exail’s (formerly iXblue) DriX is a highly reliable, multi-faceted ultra-low-carbon-footprint USV that enables operators to remove humans from risky offshore operations. With its unrivaled speed, intelligent obstacle avoidance system (OAS), stability and reduced noise radiations, DriX offers significantly more efficiency, endurance, and safety across many different survey operations—including nearshore activities in shallow, high-traffic waters—than traditional survey methods.

As a fully certified USV (by Bureau Veritas (BV) and Lloyd’s Register), we believe DriX has a key role to play in both the OSW planning (and build out) phase by executing multibeam (MBES) surveys for site investigations, pre-construction surveys for monopiles and cable routes, and during trenching operations and as-laid surveys, and the post-construction operation and maintenance (O&M) phase, running scheduled inspection maintenance and repair (IMR) procedures, including fisheries and biomass assessment.

EXCEPTIONAL DATA, EXTENSIVE COVERAGE

OSW development relies on precise seabed mapping and analysis, and so data acquired from both nearshore shallower depths and deeper offshore sites with minimal disruption to the surrounding ecosystem—including the native sea life—or other potential hazards, such as UXOs.

DriX is capable of operating in less than a meter of water—impossible for ROVs and AUVs or other long-established survey methods—but is also equipped with a whole range of sensors for deep-water survey, including an MBES capable of data capture to depths of 3,600-m, ideal coverage for pre and post cable lay routes. DriX can also be equipped with Exail’s Gaps USBL (Ultra Short Base Line) system, an excellent solution for accurately (and autonomously) tracking subsea assets, such as trenchers and ROVs, where traditional acoustic methods can be challenging, especially when operating in a noisy environment with long lay backs.

DriX’s hydrodynamic monohull and drop keel guarantee exceptional stability and balance in high waters (sea state 5) and in cross current situations, further validating the integrity of the data. The tumblehome bow cuts through the incoming waves, adding to minimize the wave induced motions on the vehicle, and allows for high operational speeds of up to 14 knots.

In terms of operational endurance, DriX can sail for 6 days at 7 knots. It can maintain continuous operations for 24 hours at a top speed of 14 knots, with a 10-day mission operating at 4 knots. Further efficiency gains are possible by force multiplication—the synchronized deployment of multiple units to carry out the same mission plan.

SITUATIONAL AWARENESS

DriX can operate autonomously under the supervision of a DriX supervisor or be directly piloted using a remote control. The supervised autonomous operation can be performed either in Line of Sight (LOS) or Over the Horizon (OTH), relying on a proprietary software framework developed by Exail.

Vehicle safety is governed by an intelligent obstacle avoidance system (OAS) that triggers real-time alerts and, when in autonomous mode, can course correct the USV to avoid any object to be avoided, while keeping the operator in the loop at all times.

DriX’s 360° situational awareness is optimized by a sensor suite that includes radar (long range detection; 3D LiDAR; 360-degree optical (camera) coverage; an Inertial Navigation System (position/attitude); GPS (position); an Automated Identification System (AIS); and a forward-looking Infrared Camera (IR). A 3D volumetric sonar such as Exail SeapiX, capable of providing real-time full 3D biomass assessment and bathymetry in shallow and deep waters, can also be integrated. This multi-sensor payload facilitates full situation awareness in variable weather and affords a 24-hour operational envelope.

KEEPING DATA SAFE

Thanks to its composite hydrodynamic monohull with Kevlar reinforcement, the 8-m DriX is both surprisingly lightweight and robust. Sensors are fully integrated within a retractable “universal gondola” located 2 m below the surface, with space to accommodate a variety of interchangeable sensor combinations, including MBES, Inertial Navigation System (INS), Ultra Short Baseline (USBL), Sub-Bottom Profiler (SBP), Sound Velocity Profiler (SVP), Magnetometers, in a bubble-free environment. An embedded high grade IMU (Exail Phins Compact C7 INS) avoids any bias or mechanical decoupling between the acoustic antennas and the measurement of the motions.

FUTURE OUTLOOK

To establish true operational efficiencies throughout the full life cycle of offshore windfarms, USVs like DriX will prove instrumental over the coming years. Intuitive uncrewed systems that minimalize a project’s CO2 footprint, while at the same establishing unprecedented HSSE standards, present offshore energy developers with a leaner, greener way of working in typically challenging marine environments.

When it comes to long duration wind measurements in greenfields for future wind farm development, DriX is also an attractive mobile alternative to the standard use of static buoys and has also proved well suited to perform other autonomous survey operations in and around wind farms, such as scour detection.

Prioritizing the ongoing development of smart ocean technologies, like DriX, that seamlessly integrate the latest in intelligent marine instrumentation and leverage the advances in speed, endurance, agility, and non-intrusive data gathering platforms is key to driving responsible, carbon conscious efficiencies throughout each phase of wind farm development.

For more information, visit. www.exail.com.

This feature originally appeared in Ocean News & Technology's Magazine December 2022 edition. To read more, access the magazine here.