A comprehensive review on ocean thermal energy conversion technology: Thermodynamic optimization, multi-energy integration, and byproduct utilization

Ocean thermal energy conversion (OTEC) utilizes the temperature difference between surface seawater and deep seawater to generate electricity. The global theoretical potential is 8-10TW. Despite the potential is grant, practical implementations face critical challenges rooted in low thermodynamic efficiency and high capital costs. This review systematically analyses the evolutionary trajectory of OTEC technologies through bibliometric analysis, identifying three emerging research frontiers: thermodynamic cycle, multi-energy integration, and byproduct utilization. Subsequently, these three research hotspots will be explored in depth. The optimized thermodynamic cycles, particularly multi-stage pressure configurations based on organic Rankine cycles and multi-stage heat exchange architectures, demonstrate enhanced thermal gradient utilization and improved system exergy efficiency. In energy hybridization strategies, solar energy integration has been identified as a promising strategy for augmenting the operational efficiency of OTEC systems. Furthermore, the utilization of OTEC byproducts, including desalinated seawater, hydrogen storage, and seawater air-conditioning systems, presents a transformative paradigm. Notably, these co-generation applications not only achieve cost reduction in power generation but also address critical challenges in sustainable refrigeration and freshwater supply for remote island communities. Finally, the challenges faced by commercial OTEC power plants in technological, economic, and environmental aspects are summarized, and relevant suggestions are put forward.