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Solar-powered boat has its day in the sun

Eighteen months after leaving Monaco, the 100-foot catamaran Turanor PlanetSolar returned to where it started, slipping silently across the finish line May 4 under cloudy skies that nonetheless delivered enough power to secure its place in history as the first boat to circumnavigate under solar power alone.

Turanor PlanetSolar is the first boat to circle the globe under just the power of the sun.

“We did 60,000 kilometers powered only by the sun,” says Raphael Domjan, the Swiss expedition leader and visionary who conceived the exploit, speaking at a press conference at the Monaco Yacht Club. (Video of the finish and press conference are at Domjan says the technology — 38,000 solar cells, 11.7 tons of lithium polymer batteries and the 20- and 40-kW electric motors in each float — worked flawlessly. He says he had more trouble with the vessel’s head and showers and other typical boat issues than with the solar system.

“We always knew it was possible to go around the world in a solar boat,” he says. “We were sure, but until now it was just talking. We did it. Now it’s no longer talking.”

The $16 million wave-piercing cat, with 537 square meters of solar cells on an aircraft carrier-like deck, carried 660 liters of diesel for backup in case of long stretches of sunless skies. However, Patrick Marchesseau, one of PlanetSolar’s two captains, says the crew never had to crack open the fossil fuel. “We are all very proud that we didn’t even use one drop of diesel to get back to Monaco,” he says.

Immo Stroeher — president and CEO of Rivendell AG, a Swiss firm that invests in renewable energy and was the project’s chief underwriter — was ecstatic. “I’m a freak,” says Stroeher, who has been involved in solar energy for 20 years. “I’ve been a freak on solar energy for many years now. … The sun is the most natural and most ordinary source of energy we have.”

Stroeher believes the technology has an economic future. After eight years developing PlanetSolar, he is founding a PlanetSolar Foundation as an “international think tank” for solar technology to develop and commercialize feasible solar projects. He says one already is under way in Tonga, where islanders are installing solar panels at homes. Another is moving forward in the Galapagos, where the government has restricted access to one of the islands to solar or electric boats only. Stroeher is considering two options for PlanetSolar now that it has completed its mission: convert it to the world’s first all-solar luxury yacht or turn it into a mobile power plant that could double as a scientific research vessel.

Stopping at 18 cities along the way to promote solar power, PlanetSolar took 584 days, 23 hours, 31 minutes to finish its voyage. It was not a speed contest, says Erwann LeRouzic, PlanetSolar’s second captain. The crew received twice-daily weather reports with sunlight forecasts from Meteo-France, the French weather service. PlanetSolar’s bridge software factored in the forecasts to set courses to maximize the amount of sunshine the boat encountered. It also regulated speed so that in case of bad weather ahead there was enough stored electricity to make it through without running short. “On good days you go fast; on bad days you go slower,” LeRouzic says. “You have to balance the energy [that the solar cells] produce with the energy [that the motors and house appliances] consume.”

PlanetSolar’s route went through mainly equatorial regions where sunshine is plentiful, but LeRouzic says there were some “really tough days” of no sun in the Mediterranean and off Vietnam, and a three-day wait off Australia for sunny skies. “We became patient, patient and patient through the bad days,” he says. “We got tough and strong.”

Erwann LeRouzic, PlanetSolar's second captain, breaks out the bubbly as the crew celebrates.

Cruising speed was about 5 knots, 9 to 10 knots tops — a little slower than the anticipated 7.5-knot cruising speed and 14-knot top end. The solar cells deliver 94-kW on a bright, sunny day — five times what the motors need to push the boat at an economical cruising speed. Batteries store 1.2 mW hours of electricity, enough to power the boat for three days — about 625 miles — without sunshine. For efficiency, PlanetSolar cruises on just one engine per side; for more effort, two motors per side kick in.

New Zealander Craig Loomes, designer of Pete Bethune’s biodiesel-powered wave-piercer Earthrace, designed PlanetSolar. Knierim Yachtbau in Kiel, Germany, built it of strong, light carbon fiber. Domjan predicts that the future of solar-boat design will be “lighter, faster, cheaper because the technology changes very fast.”
LeRouzic sees solar-power applications now in dive boats, expedition boats, small cruising yachts and enviro-boats. Besides being clean, sun power is peaceful and inexhaustible, Domjan says. Crossing the South Pacific “was like being on the space shuttle,” he says. “You could go for many days, if not forever” — in virtual silence.

This article originally appeared in the July 2012 issue.