"Slapping photovoltaic cells on a 60,000-ton boat will cut fuel consumption by 6.5 percent, which seems paltry until you realize the average cargo ship burns 120 gallons per mile. The system Nippon Yusen KK is paying Nippon Oil Corp. $1.4 million to develop will save about 46,800 gallons of fuel carrying all those cars 6,000 miles from Japan to Califonia.
To put that in perspective, if you bought a Toyota that arrived on a solar ship with 4,999 other cars, it would have saved nine gallons of fuel before you ever even saw it.
But solar ships do more than save fuel. They also clear the air. Cargo ships burn "bunker fuel," the truly nasty stuff that literally comes from the bottom of the barrel. It's kind of like the Milwaukee's Best of fossil fuels.
A study published in Environmental Science and Technology found emissions from the bunker fuel cargo ships burn may cause 60,000 deaths worldwide."