Because the transportation industry's fortunes are so closely tied to fuel costs, alternative energy sources have become a sort of Holy Grail for freight carriers. For the most part, they've remained as elusive as that legendary chalice. But according to a report by the U.K.'s BBC News, an Australian company called Solar Sailor has developed a hybrid diesel/solar-powered system that could work in commercial shipping.

The technology is currently in use on a handful of ferry boats in Hong Kong, Shanghai, and Sydney. Roof-mounted solar panels on the ferries create electricity, which is stored in a battery and powers the engine while the boats move at slow speeds. The engines switch to diesel when faster speeds are required, such as out on the open ocean. One of the ferries is also equipped with two sails covered in solar panels. The sails allow the boat to use both the sun and wind to further reduce the consumption of diesel fuel.

Other companies are testing solar and wind power for shipping, but Robert Dane, Solar Sailor's founder, told the BBC that his company's technology is closest to a commercial application. Solar Sailor plans to launch a trial with an Australian mining company that will attach a 130-foot-tall solar sail to a newly built ore carrier. Dane estimated that the sail could cut 20 to 40 percent off the annual fuel bill of a ship steaming at 16 knots, and that solar panels would save an additional 3 to 6 percent.