Ocean thermal energy conversion (OTEC) is a system that converts heat energy into electricity using the temperature difference between surface seawater and deep seawater. This paper describes a dynamic model construction for the transient performance of OTEC plant using the recently developed power cycle, in which binary mixtures of ammonia and water were used as the working fluid. The mathematical models were constructed based on thermodynamics and structural features of the power cycle. Confidence in the model's accuracy has been established by comparison of the simulation results with those obtained experimentally in a pilot OTEC plant.
Ocean thermal energy conversion (OTEC) is to convert the thermal energy into the electric power using the temperature difference between surface seawater (about 25oC to 30oC) and deep seawater (5oC to 10oC) (Vadus, 1999). OTEC is an effective method of power generation, which has a small impact on the environment and can be semipermanently utilized (Heydt, 1993). However, compared with the thermal power generation using fossils or nuclear energy, whose thermal efficiency is about 50% to 60%, the thermal efficiency of the OTEC is very low about 3% to 4% (Uehara, 1980). Further, the temperatures of the surface and deep seawater have a strong impact on the power output of OTEC plant. Therefore, for an efficiency and stable operation of the OTEC plant, a comprehensive understanding of the characteristics of the plant for achieving an appropriate operation control is required (Nakamura et al., 1988). Furthermore, before setting up a new plant, careful simulations for evaluating the operating performance of the plant are also necessary for the plant design (Uehara and Ikegami, 1990). The studies concerning the thermal energy conversion using temperature difference are mainly in promoting the performance of the power plant under a steady state.