Title: TEMPERATURE GRADIENT
Course: OCEAN POWER, THE BIG UNKNOWN > Section: MARINE ENERGY

Water typically varies in temperature from the surface warmed by direct sunlight to greater depths where sunlight cannot penetrate. This differential is greatest in tropical waters, making this technology most applicable in water locations. A fluid is often vaporized to drive a turbine that may generate electricity or produce desalinized water. Systems may be either open-cycle, closed-cycle, or hybrid.

 Ocean Thermal Energy Conversion (OTEC) uses the ocean thermal gradient between cooler deep and warmer shallow or surface seawaters to run a heat engine and produce useful work, usually in the form of electricity. OTEC could be land, shelf and floating sites.

https://en.wikipedia.org/wiki/Marine_energy#Ocean_thermal_energy