As wind power gathers a series of encouraging headlines on land, chief among them the massive Pampa Wind Project, that other untapped clean energy giant, solar power, has headed out to sea. Gains in ship design and the marine economy have not only encouraged solar power on ships, but made it easier to install there than on our homes.

The most significant of the events that will revolutionize sea travel is “solar sailing,” a method of installing the solar panels on a ship in a series of wings that allow them to be used in more than one way. If they’re deployed in a fashion that’s mechanically alterable by the crew, the ship can be trimmed to the sun as well as the wind, and the energy consumed by vessel can be reduced by as much as 90% as it cruises along not only under the energy of its propeller, but also the gentle push of the wind.

This concept has appeared in several mock-ups, but maybe most significantly was in 2007, when it set a record for speed crossing the Atlantic under solar power on a French-made testbed known as Sun21.

Sun21 traveled from the Canary Islands to Martinique in just 29 days. The technology has since matured, being accepted into business bids for a ferry service in San Francisco Bay and Sydney Harbor. There’s also a mock-up of a cargo ship operating under the French flag, and a fleet of small vessels operating around Doha, Quatar as water taxis for the wealthy.

So Why Is This Better Than Putting Panels On My House?

Placing solar panels on a ship is so wonderfully efficient because it captures the power of the wind, as well—something that they can’t do on the roof of a stationary building or while sitting anchored to the ground. The use of the panels as sails also gives ships the opportunity to maneuver the panels into a position for maximum solar exposure during periods of light wind, a secondary ability derived from that consideration, but one that serves to greatly improve the viability of the photovoltaic cells. More direct exposure to the sun means more power. It’s that simple—and sure, you could install a system allowing you to pivot the panels on your home, but that’s prohibitively expensive considering you’d have to stay at home to operate it. Ships have sailors.

How Soon Can I Ride In One?

If you’re in Sydney, tomorrow—the Solar Sailors are in operation right now, and will happily ferry you across the harbor without so much as a whiff of a diesel fuel fume. In Doha, the plan is to import some of the French-made versions by 2009 as a hedge against rising operating costs, because in a land of perpetual sun, even oil sheiks apparently can’t turn down the possibility of riding around in a clean, quiet, cost-effective ship. San Francisco is less clear, as Hornblower Cruises and events won the contract in 2006 but has yet to apparently take delivery of the ships they’ve publicly compared to a hybrid car.

More Reading:

Solar, wind powered ferries to sail on S.F. Bay (MSNBC.com)
Green ships for blue highways (CNN)
Solar Sailor (Company homepage)

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