types of OTEC

Closed Cycle: 
Closed cycle Ocean Thermal Energy Conversion systems use a working fluid with a low boiling point, Ammonia, for example, and use it to power a turbine to generate electricity. 
Warm seawater is taken in from the surface of the oceans and cold water from the deep at 5o. 
The warm seawater vaporises the fluid in the heat exchanger, turning the generator’s turbines. 
The fluid now in the vapour state is brought in contact with cold water, which turns it back into a liquid. 
The fluid is recycled in the system, which is why it is called a closed system.

Open Cycle:
Open cycle OTEC directly uses the warm water from the surface to make electricity. 
The warm seawater is first pumped into a low-pressure chamber, where it undergoes a drop in boiling point due to the pressure drop. 
This causes the water to boil. 
This steam drives a low-pressure turbine which is attached to an electrical generator. 
The advantage this system has over a closed system is that, in the open cycle, desalinated water is obtained in the form of steam. 
Since it is steam, it is free from all impurities. 
This water can be used for domestic, industrial, or agricultural purposes.