Abstract
Ocean Thermal Energy Conversion system utilizes shallow seawater as the heat source and deep seawater as the cold source, achieving energy conversion at low temperatures and small temperature differences. To improve the efficiency of the OTEC system, this paper focuses on the working fluid side, based on the closed Organic Rankine Cycle, to analyse and select common low boiling point organic working fluids suitable for the OTEC system. Two of them are combined to form new mixed fluids with different component types and ratios. The impact of different types of mixed fluids on system performance is studied. Results show that M31 mixed working fluid has higher power generation efficiency, lower operation pressure and the best economical. Peak ƞOTEC is 6.43. Compared with pure fluids, using mixed fluids greatly reduces the power consumption and the frictional resistance loss. The R245fa/R245ca (0.3/0.7) mixed working fluid has the smallest power consumption among all its component allocation ratios, with a deep seawater pump consuming 5.085kW, accounting for only 3.3% of that when using pure R245ca. Compared to pure fluids, mixed fluids have higher net output power. So, M31 can be selected as the most suitable working fluids for OTEC system among M1 to M36.