VESSEL REVIEW | Electric-powered, long-range unmanned catamarans for Irish subsea data company

XOcean, an underwater data acquisition services provider based in Greenore in northeastern Ireland, has introduced a new fleet of unmanned surface vehicles (USVs) that are capable of nearly emission-free, long-endurance operations.

Each USV in the series has a length of 4.5 metres, a beam of 2.2 metres, a height of 2.2 metres, and a displacement of 750 kilograms. A payload totalling 100 kilograms can be carried on board and may include sensors and equipment for use in a range of applications such as bathymetric surveys, environmental monitoring, data harvesting, and even fisheries enforcement.

The vessels utilise a custom-designed, composite wave-piercing catamaran hull of lightweight construction and with space for an electric propulsion system consisting of a lithium-ion battery pack and pod drives.

The complete propulsion setup on each USV was provided by Torqeedo. This includes the battery, a lightweight micro-generator, two pod drives, two bow-mounted outboard thrusters to assist in station keeping, and an array of solar panels on deck to provide efficient recharging during daylight hours. XOcean said the use of electric propulsion guarantees that the USVs can produce only about one-thousandth of the emissions of a conventional survey vessel.

The two electric bow-mounted thrusters are controlled separately to adjust the speed on each side, steering the boat on the desired course. These and the two main electric drives boast an extremely low noise signature, making the USVs ideal for operation in environments teeming with marine life.

XOcean has also claimed that the electric propulsion can help guarantee a speed of four knots and an operating range of 1,512 nautical miles, providing up to 18 days of mission endurance even with 24/7 operations.

The USVs are designed to be easily and quickly deployed, either via a road trailer or a standard 20-foot container. When underway, the vessels are controlled remotely by qualified pilots at XOcean's shore-based operations centre with the aid of a highly secure cloud-based system for monitoring battery status and the quality of the data being collected and for adjusting the USV itself and sensor parameters as required. The onboard broadband satellite transceiver provides continuous over-the-horizon connectivity, allowing images and situational awareness data to be relayed in real time.

The operators' situational awareness is enhanced by an electronics suite that includes an AIS transponder, a thermal imaging camera, visible light cameras, and image detection sensors. These are essential features as the USV has no autonomous collision avoidance system and therefore has to rely on a human operator to manoeuvre it clear of any obstacles that are detected in its way.

A proprietary mobile app developed by XOcean allows the company's customers access to real-time updates on the USV's disposition and other parameters such as weather. Customers may even view live video feeds from some of the craft's onboard cameras.

XOcean already has a number of the USVs in operation, and there are plans to place 12 in service. An example has already seen use in a real-world operating environment, completing a live seabed-to-shore data harvesting mission from an array of pressure monitoring transponders at the Ormen Lange natural gas field off the coast of Norway. The 30 sensors measure and record pressure, temperature and inclination data at the seafloor at depths of 800 to 1,100 metres. The USV transited more than 160 nautical miles from Kristiansund out to the Ormen Lange field, spent 12 hours on station retrieving data from the sensors using an acoustic array, and completed the return trip to Kristiansund in a total of just over three days.

Click here for more vessel reviews, features, and news stories as part of this month's Unmanned Craft Week.