La Rochelle, France-based Advanced Aerodynamic Vessels (A2V) believes a revolutionary hullform it has developed has potential applications in the offshore oil and gas industry.
The first example of a new type of vessel is due to enter service servicing oil production facilities in Gabon in West Africa late February 2018. The vessel, Clémentine, was built for Peschaud International in France, and will be used to transport 25 oilfield technicians to inland oil production facilities.
This particular unit, an A2V-25-CB, will not operate offshore, transporting personnel on rivers along the Gabonese coast, but another, larger unit also designed by the French company is suitable for use offshore.
Clémentine completed sea trials early in 2018 and is approved for operation on the rivers in Gabon by Bureau Veritas. It has a service speed of 40 knots with two 600 hp diesel engines.
A2V naval architect/R&D engineer Gianluca Guelfi told OSJ that the vessel has much lower fuel consumption thanks to its unique design, in which the vessel is partially lifted out of the water in the manner of a surface effect ship (SES).
The key difference between the A2V vessel and a SES is that the latter uses blowers to produce lift, whereas the A2V concept uses aerodynamic lift to raise the vessel, in the manner of an aerofoil. Therein lies its reduced hydrodynamic drag, and ability to reach high speeds with lower levels of fuel consumption and emissions than a conventional craft, transferring personnel over long distances in a shorter time period than would otherwise be possible. Other benefits of the concept – which uses business class seating – include reduced noise levels.
The A2V aerodynamic lift concept was tested using a number of prototypes in 2015-2016. The company continues to work with classification society DNV GL to obtain approval in principle for other, similar applications that would make use of the design’s ability to, as Mr Guelfi put it, safely transfer the weight of the vessel “from water to air.”
“Reducing the weight of the vessel is the key to greater efficiency,” said Mr Guelfi. “With A2V you get twice the speed for half the fuel. Thanks to aerodynamic support, above a critical speed, the faster A2V vessels go the less fuel they use.”
This critical speed depends on the application and size of the vessel but the fuel economy with respect to conventional boats is, said Mr Guelfi, “very significant” above 25 knots. This is in contrast to conventional high-speed vessels in which oversized engines allow incremental speed improvements at the cost of much higher fuel consumption and reduced payload, leading to “economically and environmentally unsustainable costs per passenger.”
The unit for Peschaud International has a length overall of 15.3 m and loaded displacement of 19 tonnes. It has a breadth of 12.1 m, air draft of 7.85 m and draft of 0.64 m. The waterjet-propelled unit can transport 25 people with a payload (including passengers) of 3.5 tonnes, at a cruising speed of 40 knots.
The company believes the concept also has potential applications offshore and has developed a version of the design, the A2V-60-CB, for long-range crew changes between shore and offshore platforms.
A2V has developed tools to evaluate the seakeeping behaviour of the larger unit and has been working with DNV GL in a joint development programme. The vessel would be capable of 60 knots offshore Angola and could also operate in safe mode at 18 knots in case of severe weather conditions.
This particular unit has a length overall of 24 m, full load displacement of 55 tonnes, beam of 16.4 m, air draft of 8 m, draft of 1.1 m and could transport 60 passengers. It is designed to comply with DNV HSLC/NSC Crewboat R2 and would have two 1,440 kW main engines and surface-piercing propellers.