Thermodynamic, economic, exergoeconomic analysis of an integrated ocean thermal energy conversion system

Abstract

This paper proposes an integrated ocean thermal energy conversion (OTEC) system that couples power generation, refrigeration, and desalination. Based on the mathematical model, the thermodynamic, economic, and exergoeconomic performances are explored by evaluating several crucial parameters such as the ammonia-water concentration of the power subsystem (Xgen), the turbine inlet pressure (Pturb), etc. The results indicate that integrated OTEC system significantly improve the exergoeconomic performance since the efficient utilization of the exhausted cold seawater. The integrated system can achieve maximum net output power of 16.79 kW, refrigeration capacity of 268.87 kW, freshwater production of 53.22 t/d, as well as exergetic efficiency of 31.69% when the power subsystem's flow rate is 1.0 kg/s. Moreover, there is a maximum net output power when Pturb is under 800 kPa, and increasing Pturb leads to higher optimal Xgen. The maximum net output power, for instance, is 2.18 kW, 4.62 kW, and 9.79 kW when Pturb value is 600 kPa, 700 kPa, and 800 kPa, respectively, with corresponding optimal ammonia concentration values of 0.73, 0.83, 0.93. Furthermore, the maximum exergetic efficiency increases as Pturb enlarges. The maximum exergetic efficiency rises from 20.40% to 31.69% when Pturb increases from 600 kPa to 950 kPa. Besides, compared to the single OTEC plant's levelized cost of energy at 3.56 $/(kWh), the integrated system's can be as low as 0.098 $/(kWh).