Editing Ocean thermal energy conversion (section)

=== Closed Anderson cycle ===

As developed starting in the 1960s by J. Hilbert Anderson of Sea Solar Power, Inc., in this cycle, ''Q{{sub|H}}'' is the heat transferred in the evaporator from the warm sea water to the working fluid. The working fluid exits the evaporator as a gas near its [[dew point]].

The high-pressure, high-temperature gas then is expanded in the turbine to yield turbine work, ''W{{sub|T}}''. The working fluid is slightly superheated at the turbine exit and the turbine typically has an efficiency of 90% based on reversible, adiabatic expansion.

From the turbine exit, the working fluid enters the condenser where it rejects heat, ''-Q{{sub|C}}'', to the cold sea water. The condensate is then compressed to the highest pressure in the cycle, requiring condensate pump work, ''W{{sub|C}}''. Thus, the Anderson closed cycle is a Rankine-type cycle similar to the conventional power plant steam cycle except that in the Anderson cycle the working fluid is never superheated more than a few [[degrees Fahrenheit]]. Owing to viscosity effects, working fluid pressure drops in both the evaporator and the condenser. This pressure drop, which depends on the types of heat exchangers used, must be considered in final design calculations but is ignored here to simplify the analysis. Thus, the parasitic condensate pump work, ''W{{sub|C}}'', computed here will be lower than if the heat exchanger pressure drop was included. The major additional parasitic energy requirements in the OTEC plant are the cold water pump work, ''W{{sub|CT}}'', and the warm water pump work, ''W{{sub|HT}}''. Denoting all other parasitic energy requirements by ''W{{sub|A}}'', the net work from the OTEC plant, ''W{{sub|NP}}'' is

:<math> W_{NP}=W_{T}-W_{C}-W_{CT}-W_{HT}-W_{A} \,</math>

The thermodynamic cycle undergone by the working fluid can be analyzed without detailed consideration of the parasitic energy requirements. From the first law of thermodynamics, the energy balance for the working fluid as the system is

:<math> W_{N}=Q_{H}-Q_{C} \,</math>

where {{math|1=''W{{sub|N}}'' = ''W{{sub|T}}'' + ''W{{sub|C}}''}} is the net work for the thermodynamic cycle. For the idealized case in which there is no working fluid pressure drop in the heat exchangers,

:<math> Q_{H}=\int_{H}T_{H}ds \,</math>

and

:<math> Q_{C}=\int_{C}T_{C}ds \,</math>

so that the net thermodynamic cycle work becomes

:<math> W_{N}=\int_{H}T_{H}ds-\int_{C}T_{C}ds \,</math>

Subcooled liquid enters the evaporator. Due to the heat exchange with warm sea water, evaporation takes place and usually superheated vapor leaves the evaporator. This vapor drives the turbine and the 2-phase mixture enters the condenser. Usually, the subcooled liquid leaves the condenser and finally, this liquid is pumped to the evaporator completing a cycle.