OTEC runs on warm and cold seawater instead of burning a fuel.
OTEC can only work naturally all year round in the Tropics because it is there that the largest natural temperature differences can be found.
The quoted minimum temperature difference required is 20 degrees but a little less could be possible.
Natural OTEC requires around 2.5 litres per second of deep-sea-cold-water to produce around 1 kw of electricity.
The cold water must be taken from 750-1000 meters below the sea-surface if the system is to work ‘naturally’.