Abstract
The ocean thermal energy conversion (OTEC) is essential to support the development of renewable energy for tropical islands. This paper introduces an efficient OTEC using Kalina cycle that utilizes the ammonia-water mixture as the working fluid. Aiming to develop a reliable control strategy for rapid load-tracking processes, a dynamic model for heat transfer and power generation in an OTEC using Kalina cycle is proposed, and an experiment of 30 kW-level OTEC using Kalina cycle is conducted to validate this model. Moreover, a multi-objective control strategy consisting of power, evaporation, superheat, and liquid-level control loops for rapid load-following is proposed. The results indicate that the proposed control strategy demonstrates high effectiveness in load-tracking control and ensuring the operational stability of superheat degree and separator liquid-level. When the power load is stepped from 34 kW to 40 kW, the load-tracking process is completed within 8.48 min, with a maximum overshoot of 6.58 % and a settling time of 5.27 min. Furthermore, the step responses of power output to the flow rates of working fluid and warm seawater exhibits underdamped second-order behavior with a transient time less than 5 min, while its response under step disturbance in flow rate of cold seawater presents general inertia.