1.2.1.2 Efficiency and Cost

Theoretical maximum efficiency is (Twarm-Tcold)/Twarm

This is called the Carnot Efficiency

Theoretical MAXIMUM 7.5% to 8% efficiency

Some is lost to heat, friction, etc

Practical Maximum gross 3.5% to 4.0%

25 to 30% of gross power production is needed to operate the plant

Net electric energy available is about 2.5% and 3%

1.2.1.1 Closed Cycle

Most likely uses Ammonia as a working fluid

Warm surface water enters a boiler/evaporator that contains liquid ammonia

Liquid Ammonia boils and produces a vapor pressure of 9.3 atm

Vapor expands and drives turbine to produce electricity

Vapor then enters a condenser at a pressure of 6.1 atm

Ammonia condenses and liquid is pumped back into evaporator

Same as RANKINE cycle in steam engines, but different fluid and lower temps and pressure

Opposite of a commercial refrigerator

Any common refrigerant fluids (freons) can be used in OTEC

Thus, studies on refrigeration and cryogenic systems can be applicable to OTEC