Abstract
Ocean thermal energy has drawn great interest due to its great storage capacity, stability and free emissions. To harness this ocean energy, researchers have proposed various Ocean thermal energy conversion (OTEC) systems, which utilize the temperature difference between warm surface seawater and cold seawater in depth to generate electricity. However, the moderate temperature difference of seawater makes the OTEC system efficiency relatively low. In this context, this paper reviews different approaches to improve the performance of the system from perspectives of both thermal cycles and multi-generation. The OTEC systems reviewed in this work incorporate Rankine Cycle, Kalina Cycle, Uehara Cycle, and Guo Hai Cycle and possible improvement measures associating with working fluid selection and thermal cycle reconfiguration to obtain higher cycle efficiency. In addition, the multi-generation OTEC systems serve for different functions including power generation, desalination, refrigeration and hydrogen production are extensively discussed. The technical challenges faced by the OTEC systems are identified in the end of this work. It is worth noting that the current research on OTEC systems is still biased towards theoretical simulations and few studies using experimental methods have been conducted.