Thermodynamic analysis of heat storage of ocean thermal energy conversion integrated with a two-stage turbine by thermal power plant condenser output water

The ocean thermal energy conversion (OTEC) system uses the temperature difference between warm sea surface water and deep cold water to generate electrical power. Due to the low-temperature difference between surface warm water and deep-sea cold water, the thermal efficiency of these systems is low compared to fossil fuel-driven power plants. In the present study, to propose a method for increasing the output power, thermal efficiency, and heat storage of an OTEC cycle, the warm water outlet of the existing thermal power plant is used instead of surface water which is conventionally employed in basic OTEC cycles. The results show that, considering average electrical net power in the basic OTEC cycle per month the energy and exergy efficiencies are 3.34 % and 17.2 %, respectively. Then, the suggested OTEC cycle is investigated using a two-stage turbine and reheating in terms of energy and exergy. Comparing the results obtained for the two configurations shows that, in the proposed cycle, the average output power is increased by 552 kWh per month, and energy and exergy efficiencies are improved by 0.048 % and 0.31 %, respectively. As an existing thermal cycle performance, a case study of a real Combined Cycle Power Plant (CCPP) is modeled with the proposed cycle. The results show that the average net electrical power is produced by 17.72 MWh per month by using the outlet water from the condenser of CCPP and the energy and exergy efficiencies have been increased by 1.432 % and 8.02 %, respectively Compared to the base cycle. Also, using condenser outlet warm water, an average of 18,829 tons per day of fresh water is produced, and the thermal efficiency of the CCPP is improved by 1.87 %.