Volume 5: Innovative Solutions for Energy Transitions: Part IV

Thermodynamic Analyses of Dual-Pressure Organic Rankine Cycles for Ocean Thermal Energy Conversion (OTEC) Qiang Liu, Zhigang Lan, Ting Yu, Dashu Li, Yonghu Wu, Juan Yue

Abstract

Ocean thermal energy has been identified as a good thermal source for electric power generation especially for offshore oil and gas platforms and island energy security. Organic Rankine Cycles (ORCs) are promising systems for conversion ocean thermal energy to electricity; however, the thermal efficiencies still need to be increased. In this work, a dual-pressure ORC is used to improve the thermal efficiency of a closed ocean thermal energy conversion (OTEC) power plant. The evaporation and condensation temperatures of the dual-pressure ORCs are optimized to maximize the net power out. Compared to single-pressure ORCs, the dual-pressure ORCs can reduce the warm seawater temperature drop about 2 °C and generate 28-29% more net power. The working fluid with a higher critical temperature has a lower flow rate for the optimal condition. R600 produces slight high power than the other selected working fluids.

Keywords dual-pressure Organic Rankine Cycle, ocean geothermal energy conversion (OTEC), thermodynamic analysis, parameter optimization, working fluid