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Naval engineering 

Autonomous boat

An autonomous prototype of a solar-powered vessel carries out measurements and collects data in rivers, lakes and the ocean

Holos BrasilPowered by nothing more than solar energy harnessed by photovoltaic panels mounted on its canopy, a small electric boat developed by Holos Brasil (a company based in Rio de Janeiro) and controlled by a single person on land with a portable computer is capable of autonomous, unpiloted navigation. Besides batteries for storing electricity, the boat carries instruments for a variety of missions, including meteorological, oceanographic and fluvial data collection (depth, mapping of floor topography, etc.), and for studying aquatic life. Furthermore, with its ability to monitor underwater pipelines and other equipment, the solar- powered boat has applications in the oil industry. Measuring 3.2 meters in length, 1.6 meters wide and weighing 82 kilograms, the catamaran-type boat (having two parallel hulls connected by two beams bearing the solar panels) cruises at three knots (5.5 km/h). Still a prototype at the testing phase, it is the first vessel with these features ever built in Brazil.

Lorenzo Cardoso de Souza, a naval engineer and partner at Holos, explains that the idea behind the vessel’s development came about when he participated in 2009 in Solar Challenge Brazil, a competition between single-pilot boats powered by photovoltaic energy that was organized by the Federal University of Rio de Janeiro (UFRJ) and sponsored by Enel Brasil (a natural gas and electric power generation and distribution company), the city of Búzios in Rio de Janeiro, and the Secretariat of Sports of the State of Rio de Janeiro. “At the first of these events Holos competed with two vessels through a partnership with researchers from Coppe [Alberto Luiz Coimbra Institute for Graduate Studies and Engineering Research at UFRJ]” explains Souza, who, along with Frederico Garcia Magalhães, founded Holos in 1998. “Both vessels won in their respective categories,” he said. Besides developing this prototype, the company manufactures sailboats, oceanographic buoys, racing boat equipment and carbon fiber wheelchairs.

At the same competition, a team from the Federal University of Santa Catarina (UFSC) took first place in the catamaran category. Later, in 2010, the team joined Holos in Holland to meet a similar test: the Frisian Solar Challenge. From then on, collaboration between the two teams got stronger and, at the invitation of the Santa Catarina team, Holos participated in the construction of a solar-powered boat for transporting schoolchildren in the community of Santa Rosa, situated on Onças Island in Barbacena municipality, in the state of Pará. The 22-passenger piloted vessel was completed in 2014 and is now in operation, transporting students between the Island where they live and downtown Barbacena.

First prototype
As Souza tells it, it was during this effort that he and Magalhães broke into the world of electric powered boats. “We then came up with the idea of developing a boat that would be autonomous not only in terms of navigation, but also the energy that powers it,” he explains. It would be a vessel that could, by means of solar panels, store energy by day to travel at night.” The project was submitted in 2103 to the Rio de Janeiro Research Foundation (FAPERJ), which approved R$300,000 in funding.

Holos Brasil With solar panels, the boat travels with uninterrupted autonomy, its speed falling from 5.5 to 1.8 km/h under overcast skiesHolos Brasil

The first prototype was completed in 2016 and has already undergone a bathymetry (depth measurement) test requested by Coppe at Fundão Island, where the UFRJ main campus is situated. The boat’s four photovoltaic panels—each measuring 50 cm by one meter and housed between its two hulls—supply a total of 400 watts of energy. The electric power that is generated is stored in six lithium batteries, which ensure uninterrupted cruising, 24 hours a day. “With the panels, the vessel’s autonomy is constant, allowing it to cruise without having to stop,” explains Souza. “Even on overcast days, the boat continues cruising. In this case, with less power available, velocity would be reduced, perhaps by only one knot (1.8 km/h). With batteries alone and no panels, the boat remains autonomous for 10 hours.”

The boat is equipped with computers and programs for autonomous navigation, as well as a compass, accelerometers, and gyroscopes. “These systems and this equipment ensure that the boat will follow a pre-programed route, unaffected by tides, winds, and other oceanic conditions,” says Souza. In this first prototype, communications between the vessel and base of operations are carried out via UHF radio, which limits the operating radius to about 10 km. “We have a project underway for the vessel to communicate via satellite,” adds Souza.

The success of the prototype, the C-400, prompted Souza and Magalhães to found a new company, Unmanned Surface Solar Vehicle (USSV) to sell autonomous boats. Two models are in the final stage of development: a small one measuring 2.5 m in length capable of up to 20 hours of autonomous navigation, and an oceanic vessel, 4.5 m and autonomous for up to 90 hours. The average speed of both boats will be 5.5 k/h. “The C-400 has aroused the interest of Petrobras and the Brazilian Navy,” says Souza. Holas plans to sell each of its smaller boats for R$130,000. The price for the oceanic model has not yet been determined.

Marcos Gallo, an engineer and professor at the Dynamics Laboratory of Cohesive Sediments (LDSC) of Coppe’s coastal and oceanographic engineering division, who monitored the prototype tests, sees the importance of developing autonomous boats. “They facilitate access to areas that other types of vessels find restricted owing to their size and draft [the portion of the vessel’s structure that remains submerged], and offer greater mobility and practicality when conducting measurements,” explains Gallo.

Nonetheless, Souza recognizes the boat’s disadvantages, such as its limited power. “This restricts the amount of equipment that can be placed on board, because the energy generated by the photovoltaic panels has to be shared between them and the vessel itself,” he explains. “The large area taken up by the solar panels presents another disadvantage,” adds Souza.

Autonomous solar vessels are still rare. Souza mentions the British firm ASV, manufacturer of a boat that—besides being solar powered—uses a diesel engine. The Seacharger, the first autonomous solar-powered boat tested in 2016, was developed by Damon McMillan, a U.S. company. It arrived in Hawaii after a 4,469-kilometer voyage from California that lasted 41 days. The Wave Glider, another autonomous boat that was developed by the U.S. company Liquid Robotics, has also cruised great distances, travelling from San Francisco to Australia in 2015. The Wave Glider’s solar panels power the on-board equipment while the boat is propelled by sea-wave energy.

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