Studying the Waste Heat Recovery of a Gas Turbine Cycle from a Thermodynamic Perspective

Abstract

An evaluation was conducted to assess the effectiveness of a proposed integrated cycle designed to recover waste heat from a gas turbine for the production of power, hot water, freshwater, and hydrogen. The system comprises a gas turbine, a steam Rankine cycle, an organic Rankine cycle, a PEM electrolyzer, a reverse osmosis (RO) unit, and a domestic water heater (DWH), working together to deliver the primary outputs of power, hydrogen, hot water, and freshwater. A comprehensive thermodynamic simulation was performed using EES software, accompanied by a parametric analysis to evaluate the cycle's performance under varying input parameters. The results revealed that the system achieves energy and exergy efficiencies of 24.92% and 15.01%, respectively. Furthermore, the combined power output from the system's three turbines and two thermoelectric generators (TEGs) totals 320,412.8 kW. Moreover, the system produces 0.556 kg/s of hydrogen and 18.31 kg/s of freshwater. An exergy loss analysis identified the gas turbine and the steam Rankine cycle as the components with the highest exergy destruction rates. It was observed that increasing the evaporator temperature of the steam Rankine cycle enhances power output from TEG 2 and freshwater production, while simultaneously reducing power output from TEG 1 and lowering the total exergy destruction cost. Furthermore, raising the figure of merit of the TEG improves the system's energy and exergy efficiencies, boosts power generation from the TEG, and enhances freshwater production rates. Finally, it was demonstrated that improving the efficiency of the electrolyzer significantly increases the hydrogen output of the system.