Solar power takes to the seas

Tûranor PlanetSolar, the world’s largest solar vessel, has already has circled the globe powered by SunPower solar cells. Solar ferries, tugs, and sailing vessels are now rolling off a host of dry docks in Europe, the U.S. and India, among other locations.
Small solar systems on recreational boats have been in use for many years, but of late, much larger vessels are being outfitted with solar and storage to provide emergency power, meet dockside exhaust requirements and extend operations already underway. Globally, the market for solar energy for marine applications is largest in the 1 W to 10 kW range, one analyst suggests, including the autonomous unmanned vehicle (AUV). More strategic tie-ups between solar, motor, and storage companies will lift the rising market even faster.

Seaborne solar fields

Thus far, the largest solar-powered vessel in the world is the PlanetSolar, a whopping 89,000 kg (89 metric tons) carbon fiber catamaran, currently owned by Race for Water, based in Lausanne, Switzerland. The vessel was designed by LOMOcean Design, of Auckland, and built by Knierim Yachtbau of Kiel, Germany, at a cost of €15 million ($16.9 million). Launched in March 2010, the topside of the 31 meter boat is covered by 29,124 SunPower Maxeon solar cells, nominally rated at 120 kW, with 18.8% efficiency.
Essentially a luxury yacht, PlanetSolar’s cells drive electric motors in each hull, charging 7.7 metric tons of lithium-ion batteries and permitting speeds of up to 14 knots (26 km/h). After 585 days at sea, PlanetSolar circumvented the globe with zero cell failures, SunPower notes. The Maxeon cells feature back-connection from a copper plate with thick connectors, and a corrosion-resistant combination.

Solar ferries take to the wind

Perhaps the most successful commercial market penetration of solar at sea – or on inland waterways – is as the primary power source for passenger ferries. One global leader in solar ferry production is Ocius Technology, based in New South Wales, Australia. The company built one of its Solar Sailor ferries, carrying 186 passengers, for the Shanghai World Expo, in association with Suntech Power, based in Wuxi, Jiangsu Province, China.
Ocius claims credit for the creation of the hybrid wind-solar sail. “We came up with the Solar Sails idea in 1996, and have built six passenger ferries around the world,” says company CEO Robert Dane. Ocius licenses its technology and intellectual property worldwide.
Solar sails are upright wings that can rotate on two axes, either manually or hydraulically. They can function as a sail alone, a solar collector, or both at once. With maximum exposure, the sails can increase ship efficiency by up to 40%, Dane claims. Initially using Solon solar panels, the company has tried several suppliers since.
“We put the solar sails on one big ship, and they found a 5-6% saving in diesel fuel,” notes Dane. “We often get 120% of production from a solar panel because of higher ambient light and reflection off the water,” he says. However, as fuel prices have declined, the market for solar ferries has slowed, so in the meantime, Ocius has turned to the autonomous unmanned vehicle (AUV) market.
Among solar ferry projects in India is Kochi-based NavAlt Solar & Electric Boats’ 75 passenger vessel, nearly completed for the Kerala State Water Transport Department. The ferry is 20 meters long, seven meters wide, and has a maximum cruising speed of 7.5 knots (14 km/h) for five or six hours a day, which it will use to ply backwaters of Alappuzha on the Laccadive Sea. The joint venture is comprised of Amsterdam’s Alten Energy, EVE System of Taluyers, France, and Navgathi Marine Design and Constructions, based in Kerala. Similarly, Alusín Solar, of Aviles in the Asturias region of Spain, is nearing completion of the Texelstroom passenger ferry for client company TESO, at the La Naval shipyards in Sestao, in Vizcaya Province, sporting 450 solar panels, says xAdvertisement

José Bayón Torres, a spokesman for Alusín. Taiwan’s AU Optronics’ BenQ Solar division is supplying 450 modules for the vessel.
The 5 kW Solar Sal, designed at Rensselaer Polytechnic Institute, in Troy, New York, regularly plies the waters of Erie Canal at a speed of five knots (9 km/h), thanks to two Torqeedo electric motors. German firm Torqeedo now sells many motors for small vessels outfitted with solar panels. The company also developed the first electric propulsion system designed for kayaks, the Ultralight 403, which weighs 16 pounds (7 kg), including a lithium battery. Larger electric motors from the company use Johnson Controls automotive lithium-ion battery packs.
Eco Marine Power, based in Fukuoka, Kyushu Island, Japan, is developing Aquarius Marine Solar Power, a patented, integrated system that may include a computer, battery chargers, batteries, marine-grade solar panels from Italy’s Solbian Energie Alternative, and interfaces to other equipment. The Solbian panels are crystalline silicon cells encapsulated in polymer films. “The polymers used for the panels have a high resistance to weathering enabling certification according to IEC 61215 and 61730. This combined with their flexibility makes them ideal for use on ships,” says Greg Atkinson, CTO of Eco Marine Power. The system was tested out in 2014 on the passenger ferry Blue Star Delos, in Greece. Like other maritime solar solutions, the Aquarius system can be paired with Eco Marine’s EnergySail technology, under development. “Typically we are looking to reduce fuel consumption by around 10%. At the moment the expected normal wind speed operating limit is around 40 knots (74 km/h) but they are designed to be able to survive higher wind speeds than that,” Atkinson says.

Vessels gain solar endurance

Small autonomous solar marine vessels are growing in number thanks to military, oil and gas, and research sector demand. Liquid Robotics’ Wave Glider family, which combine wave power and solar energy to navigate the world’s oceans, together have logged over 1 million nautical miles. The latest version, the SV3, is a surfboard-shaped hydrokinetic vessel that measures 10×2 feet (3×0.6 m) on the surface, tows a 25 foot (7.6 m) umbilical cable, and supports a submerged 7×4 foot (2×1 m) glider, to which sensors and other electronic gear is mounted. Liquid Robotics now has a fleet of some 350 Wave Gliders, which have withstood dozens of typhoons and untold shark bites. The gliders have solar panels embedded into their decks that sport three 54 W panels — soon to be bumped up to 60 W — and battery backup capacity of up to 6.86 kWh, says Tim Ong, the Vice President of Mechanical Engineering for Liquid Robotics. Protected by five U.S. patents and 14 foreign patents, the vessel is continuously being redesigned at client request to carry more weight and generate more power, a curve set that theoretically has no upper limit, he says.
The solar panels and the batteries for the SV3 are manufactured to Liquid Robotics’ design by outside vendors, whom the company declines to identify. With a proprietary plastic facing, the panels are rigorously tested for thermal cycling, hail, wind and are even submerged for several weeks.

AUV salvage hunters

Another use of solar to power autonomous maritime vessels is the sea-cleaner project SeaVax, by Bluebird Marine Systems, based in the U.K., which is targeting the collection of floating plastic trash on the high seas. Still in development and touted as the world’s largest vacuum cleaner, “SeaVax is a blue water cleanup ship that uses several stages of filtration to remove nets and bulkier plastic waste, and to filter plastic particles from the ocean gyre soups,” according to Chris Close, the Project Director.
SeaVax is a trimaran outfitted with a hybrid solar and wind system to provide over 3.9 kW per metric ton of weight. The initial one year mission of the first full-scale vessel is to target the “swirling mass of waste known as the North Pacific Subtropical Gyre (NPSG) or the Great Pacific Garbage Patch, roughly twice the size of Texas,” describes Close. The vessel would be the first of a fleet that scoops up, grinds down the plastic, and delivers it to crew-operated bulk cargo ships.

Research for use at sea

Research on marine applications for solar is advancing at a rapid rate. One renowned research center that has served both is the Woods Hole Oceanographic Institution (WHOI), based in Cape Cod. The Commonwealth of Massachusetts awarded WHOI a five year, $5 million grant for the construction of research and test facilities for marine robotics including AUVs. WHOI AUV technology has already been spun out to three private companies, Hydroid LLC, Teledyne Webb Research, and Bluefin Robotics.
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