Ocean heat could supply essentially endless clean energy to islands

A 140-year-old idea to exploit the temperature differences between layers of the ocean is gaining new interest as a way to provide clean power for people living on islands.

Called ocean thermal energy conversion (OTEC), the idea is to use surface water warmed by the sun to heat a fluid such as ammonia or water, which then spins a turbine as it evaporates, just like a power plant driven by steam. Cold water from deeper layers of the ocean would then be …