Efficiency Comparison of Subcritical OTEC Power Cycle Using Various Working Fluids

Abstract

This paper presents an investigation into the efficiency of the subcritical Ocean Thermal Energy Conversion (OTEC) power cycle using various working fluids under different operation conditions. The analysis procedure was performed with a simulation program written in EES using four parameters condensing temperature, evaporating temperature, subcooling degree, and superheating degree. With the given analysis conditions, efficiencies of the working fluids were evaluated and compared. It was found that the thermal efficiencies of the subcritical OTEC power cycle depend strongly on the evaporating and condensing temperature, while not depending on subcooling and superheating degrees. With a thorough grasp of these results, an efficient OTEC power cycle can be designed. R717 and R404A yielded the highest and lowest thermal efficiencies among the wet fluids, and R-22 showed the largest efficiency among the dry fluids. For the iso-entropic fluids, R245fa provided the highest thermal efficiency. For all the fluids, R717 yielded the highest thermal efficiency. Although R717 presented the highest efficiency, the toxicity is a concern. R717 is the preferred choice for the subcritical OTEC power cycle.mulation program written in EES using four parameters condensing temperature, evaporating temperature, subcooling degree, and superheating degree. With the given analysis conditions, efficiencies of the working fluids were evaluated and compared. It was found that the thermal efficiencies of the subcritical OTEC power cycle depend strongly on the evaporating and condensing temperature, while not depending on subcooling and superheating degrees. With a thorough grasp of these results, an efficient OTEC power cycle can be designed. R717 and R404A yielded the highest and lowest thermal efficiencies among the wet fluids, and R-22 showed the largest efficiency among the dry fluids. For the iso-entropic fluids, R245fa provided the highest thermal efficiency. For all the fluids, R717 yielded the highest thermal efficiency. Although R717 presented the highest efficiency, the toxicity is a concern. R717 is the preferred choice for the subcritical OTEC power cycle.