The quest started three decades ago at NYU, when grad student Dean Corren wrote his thesis on the then-obscure subject of global warming. This fall, Verdant Power, where Corren is chief technology officer, submerged a sixteen-foot-wide turbine in the turbulent waters off Roosevelt Island. A previous test had powered a Gristedes on the island, but the river’s fierce flow chewed up the turbine’s blades; this time, rotors made from layered fiberglass and plastic emerged without a scratch, a major step forward. Verdant expects to bolt five turbines to the East River’s bedrock by 2014, perhaps selling the electricity to Con Ed or hooking up with the new Cornell tech campus to supply renewable energy. Fulfilling one dream will put even bigger goals on the agenda: tidal-powered electric cars and manufacturing turbines that can spin beneath the oceans.