Ocius Bluebottle USV | Digest In addition to the five sold to the RAN, the company itself owns seven Bluebottles, using them as demonstrator or contract vehicles in collaboration with prospective customers. “Over more than 23,000 nautical miles we’ve lost two solar sails, one rudder, lots of flippers, and power to the propeller a few times, but because of redundancy of power from solar, wind or waves, we’ve always been able to stay safe and 99% of the time get ourselves home,” Dane recounts. In addition to these and the five built and delivered to the RAN, three more were in construction at the time of writing and lined up for work in the defence and oil & gas industries. One, called Bathy, will be a prototype of a new class with a 5 kW diesel generator in the payload bay and 400 litres of diesel fuel in the keel where the winch would normally go. This will increase the power output available for hydrography so it can use high-end bathymetric echo sounders for seafloor mapping. Solar power Power supply is a matter of careful balances and trade-offs. Around 120- 150 W is needed to run the Bluebottle 24/7, and if there are 8 hours of sunlight in a day (and propulsion produced using the rudder-flipper and sail rather than the propeller), the solar array will produce 300 W per hour on average. That makes for 150-180 W of surplus power for payloads or for storage in batteries. “We really only use the propeller in doldrums, for collision avoidance or for quick dashes to catch sight of something like fleeting criminal or biological activity,” Dane adds. “At full battery, we can do 6 knots for 10 hours, but we try to get by on windsailing and flippering at 2-3 knots, saving the excess solar energy gathered during the day to give a constant 150 W to the payload sensors. “We also try to maximise the solar power throughout the day. For instance, when the sun rises or sets it’s at a low angle, giving the Bluebottle with the sail down only about 80-100 W, but with the solar sail deployed we get 400- 500 W at dawn and dusk. Similarly, if we get strong winds around midday we can lower the sail and flipper straight into the unfavourable winds, using zero throttle but generating 500-700 W.” The sail is deployed autonomously, using an electromechanical actuator in the forward hull compartment to lift or lower the mast. When not in use, it sits flat on the deck, and has an identical layout of solar cells on the sail as on the deck. “It’s like the wing of a bird – it folds completely away but doesn’t take up any valuable payload space,” says Dane. Lower decks Most of the Bluebottle’s solar cells are assembled and provided by Solbian, and are designed around a crystalline silicon semiconductor with a 21.5% solar conversion efficiency. Ocius selected them for their modularity, as well as their proven efficiency in competitive environments – Volvo for example uses them in round-the-world races. “They’re encapsulated, so we can install them on the decks and the solar sail, and bend them,” Dane observes. “They don’t seem to be affected by salt residue, even though we’re averaging 3050 days at sea per mission. “That means there’s been no noticeable reduction in solar power despite the high potential for stains and damage on them, they’ve really been very reliable. Theoretically we could use other suppliers as well – we’ve designed the boat to allow it to take industry-standard solar Tired of generic job boards and speculative CVs? Why sift through irrelevant CVs when a laser focused recruitment portal can deliver quality over quantity? Contact teddy@uncrewedengineeringjobs.com for more information on our 1x, 5x, 10x & unlimited job packages. The solar cells are encapsulated, so we can install them on the decks and solar sail, and bend them. They don’t seem to be affected by salt residue
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