Under the Transom How to power it all, including the main propulsion? The answer is fuel cells, power sources already in development that produce energy, instead of storing it like a battery, by changing the chemical energy of a fuel (hydrogen) and an oxidant (oxygen) to electric energy and heat. Bonus points: no moving parts, no noise, no emissions besides water. This technology is already sufficiently developed to power concept cars, buses, and even some buildings and hospitals. "Fuel cells are a long way out, but you're going to see them," says Kelly Grindle, group vice president of the marine electronics group, maker of Minn Kota trolling motors.