Henry Robinson, the managing director of U.K.-based unmanned marine navigation company Dynautics, spoke at the Autonomous Ship Technology conference in Amsterdam, discussing the possibilities of autonomous vessels that consume low-power while having long-endurance when out in the ocean.
“A good tagline for these low-power, long-endurance autonomous vessels would be ‘less is more.’ The justification is that by using such vehicles, we can take the crew off and also save money on fuel,” said Robinson. “There’s a general trend in shipping and in any form of transport that the further you want to go, the bigger the vessel you’re going to need. These vessels are about bucking that trend by harvesting energy on their own.”
Robinson spoke of the Autonaut, an unmanned surface vessel that is entirely propelled by the motion of ocean waves, converting the wave energy efficiently into electrical energy. Robinson contends that this is better than having wind turbines on ships, because they are not durable enough to weather severe storms.
Nonetheless, the speed of a 16-foot long Autonaut is typically around 1 to 2 knots – a pace expected with the lack of a combustion engine in its midst. “But it is relentless. As long as there are waves, which is pretty much all the time, the vessel can go on almost indefinitely. It is not limited by stored power on-board, has relatively few moving parts and is robust. The greatest advantage is that it is almost dead silent, and is particularly well-suited for maritime surveillance.”
Surveillance via unmanned and perennially active vessels is valuable for military purposes; maritime activity can be monitored without spending millions on ships’ operational costs. Maritime and environmental organizations can also use the Autonaut to detect hydrocarbon emissions coming from ships as they sail close to a port.
The vessel produces energy primarily by the heaving motion of the hull on the waves, and also to a lesser extent, from its pitching motion. That apart, the Autonaut can be decked with solar-powered photovoltaic (PV) cells, which can produce a maximum of 14 watts per square feet. However, Robinson cautioned that this is not usually the case, as heating up of PV cells can dramatically reduce their efficiency, with a typical 16-foot Autonaut producing around 4.7 watts per square feet.
To maximize energy usage, Robinson advocated for reducing the amount of data that gets relayed to and from the vessel to the cloud database. This process consumes a great deal of power, which can be trimmed down by processing collected data on the on-board platform control system.
“The more we push intensive data processing out to the nodes, the more we can reduce our reliance on high bandwidth communications, and the power requirements that go with them,” said Robinson. Sensors collect a variety of data which can be pre-processed on-board, thus reducing the need to send all the data back to the cloud.
“A good example is an experiment we did some years ago. We took several hundred photographs on the Autonaut and ran all of them through an algorithm that automatically scanned every image, decided if there was something of interest on each photo, and if so, picked up that thumbnail, compressed it and sent it back. This reduced a 4-megabyte image to less than 2 kilobytes, with a 2000:1 compression. This meant that a four-hour transmission only lasted seven seconds,” said Robinson.
The Autonaut has been in operation over the last five years and is currently used in The Ocean Cleanup initiative across the Great Pacific Garbage Patch. Robinson concluded by saying that there are thousands of organizations worldwide that study the oceans and a solution like the Autonaut would be tailor-made to understand the oceans at a more granular level.
“The biggest use of power on a vessel is for propulsion. And the technology of wave propulsion is scalable, because if you can do it for a 3-meter vessel, you can also do it for a 30-meter or 300-meter vessel,” said Robinson. “You are not going terribly fast on this [the Autonaut], but you can propel the ship at a good speed if you get enough electric PV cells on the roof.”