Theoretical, numerical and experimental research on an innovative ocean thermal energy conversion coupled VMD desalination system

This paper proposes an OTEC-VMD desalination system that fully exploits tropical ocean thermal energy to alleviate freshwater shortages on remote islands, with no need of coupling with other heat sources. Based on an in-depth analysis of the mass and heat transfer theory of the OTEC-VMD desalination, a CFD model is established by embedding a UDF program in commercial software and an experimental prototype with a water production capacity of 1 kg/h is designed and manufactured. The CFD simulation and experimental test results show good agreement, with relative errors around 5 %. The proposed system can stably produce water, demonstrating the feasibility of OTEC-VMD seawater desalination experimentally for the first time. At a warm seawater temperature of 30 °C, the water production reaches 1.07 kg/h, achieving the design target. The system's water recovery ratio and specific electrical energy consumption are 0.254 % and 2.62 kWh/m3, respectively, and the TDS is lower than 5 mg/L. Compared to low-pressure flashing, the equipment achieves an average volume reduction rate of 94.71 %, making it more suitable for installation and transportation in remote marine locations, with great potential in replacing the low-pressure flashing device in the open-cycle of OTEC power plant to promote the large-scale application of OTEC technology.