Working Fluid % Efficiency Lower Bound Upper Bound First Law Carnot Ammonia 1.41 1.67 1.42 7.41 1,3, Butadiene 6.14 6.56 6.17 7.41 Methyl Chloride 2.32 2.63 2.33 7.41 Propane 5.27 5.64 5.28 7.41 Refrigerant # 12 5.63 5.99 5.65 7.41 Refrigerant # 21 4.34 4.65 4.36 7.41 Refrigerant # 504 1.76 2.00 1.76 7.41 Water 1.60 1.75 1.60 7.41 While the upper bound shown by Inequality (7) is dependent on the properties of the working fluid in addition to temperatures of heat source and heat sink.

Table 1: Comparison of efficiencies of various working fluids which may be used in an OTEC Rankine power cycle operating between temperatures of 40°F (4.4°C) and 80°F (26.7°C).