Rigid solar panels that also act as sails for large cargo vessels could produce fuel savings while lowering emissions, Japanese researchers say.

The EnergySail concept by Japan's Eco Marine Power would harness and store wind and solar power to reduce fuel costs and pollution, providing an additional source of power to a ship's main engines.

The solar/sail panels, with an automatic control system to orient them to catch the wind and sun, could be used on large bulk ore carriers, cable-laying ships, ferries and coast guard patrol vessels, the company said.

The solar sails would work even when the ship is docked, allowing it to forgo the need to run auxiliary diesel generators in port, it said.

"We have started testing in a lab in Osaka and we will bring in other components of the system over the next few months," Greg Atkinson of Eco Marine Power said. "At the moment, we are focused on the control system and command interface testing."

The EnergySail setup could generate annual fuel savings of 10 to 20 percent depending on the type of vessel, Eco Marine Power said.