Evaluation of power and freshwater production based on integrated gas turbine, S-CO2, and ORC cycles with RO desalination unit

Abstract

In this paper, the simultaneous production of power and freshwater by the integration of a gas turbine (GT), a supercritical carbon dioxide (S-CO2) cycle, an organic Rankine cycle (ORC) and a reverse osmosis (RO) desalination unit is proposed. The S-CO2 and the ORC are bottoming cycles that recover the waste heat from the exhaust gases of the GT. A RO seawater desalination unit has been added to this power generation cycle to produce low-cost freshwater. The thermodynamic modelling and the simulation of the integrated cycle are performed. In addition, exergetic, exergoeconomic and exergoenvironmental analyses have been carried out. Cyclopentane has been chosen as working fluid of the ORC. The results show that the total energy generated by the cycles is about 75.1 MW; the compressors and pumps consume 44% and the rest is sent to the electricity grid. The integration of the S-CO2 cycle with the gas turbine increases the total efficiency by 10.9%. Also, the addition of the ORC to this integration, improves the efficiency by about 2%. The cost of power generation in the gas turbine is about 0.604 $/s, in the turbine of the S-CO2 cycle about 0.182 $/s and in the turbine of ORC cycle about 0.036 $/s. The cost of freshwater production in the RO unit with 5 MW of power consumption is 0.88 $/m3. The results show that the proposed combined GT/S-CO2/ORC/RO regenerative system is promising in terms of waste heat recovery from gas turbines. As advantages, deep waste heat recovery, high exergetic efficiency, and low power and freshwater costs have been achieved.