Thermoeconomic analysis and optimization of a reverse osmosis desalination system driven by ocean thermal energy and solar energy

The utilization of solar and ocean energy for seawater desalination represents a significant prospect in solving energy crisis and water shortage. In this work, a new reverse osmosis desalination system based on ocean thermal energy conversion and solar energy utilization is proposed. The reverse osmosis system is driven by organic Rankine cycle, which obtains energy from ocean and solar energy, to produce freshwater. The mathematical model of the system is established and several indicators are employed to evaluate the system performance from the aspects of thermodynamics and thermoeconomic, including turbine shaft power, freshwater output, daily exergy efficiency, total water price and thermoeconomic unit cost. The effects of key thermodynamic parameters on the system performance and the system performance optimization with thermoeconomic unit cost and daily exergy efficiency as the objective functions based on the method of genetic algorithm are implemented. The results show that the turbine inlet pressure and the solar collection temperature have optimal values to reach the peak point of the system performance, while the increases of terminal temperature difference and pinch point temperature difference lead to a negative effect on the system performance. The exergy analysis shows that the main exergy losses occur in solar collector and heat exchangers.