Considering the geographical position of South Korea, the concept of C-OTEC (Combined Ocean Thermal Energy Conversion) is thought to be feasible. C-OTEC uses the latent heat of the steam exhausted into the condenser of a power plant as a heat source, in contrast to the conventional OTEC cycle, which is based on warm surface water. More specifically, the C-OTEC heat source can always be maintained at around 32 °C which is the temperature of saturated steam when it is condensed. This paper describes the selection of the working fluid, thermodynamic analysis, and the impact on the Rankine cycle when providing steam to the C-OTEC process. Based on the analysis, C-OTEC is expected to be beneficial for power plants through increased output and plant efficiency. Especially in the case of old power plants which cannot easily maintain their rated output during the summer, C-OTEC is expected to help to improve the condenser vacuum, reduce the necessary pumping power, and reduce the temperature of the discharge side. Given the current economic scenario situation, the focus is on optimizing the fabrication of the main components which can be done with the design of a prototype C-OTEC. Presently, the KEPCO (Korea Electric Power Corporation) Research Institute is conducting a national research project involving the construction of a prototype C-OTEC for a demonstration. It is expected to be operational by the end of 2014.