A Comprehensive Study on Hydrogen Production via Waste Heat Recovery of Gas Turbine Cycles in Cogeneration Power-Hydrogen Layouts: 4E Study and Optimization

Abstract

The efficient utilization of waste energy in gas turbine (GT) cycles (GTCs) is a crucial aspect of sustainable energy production. While previous studies have explored various aspects of waste energy recovery, a comparative analysis of different bottoming configurations has been lacking. This research thoroughly studies the literature and investigates four primary bottoming cycles: the steam Rankine cycle (SRC), supercritical Brayton cycle (SBC), inverse Brayton cycle (IBC), and air bottoming cycle (ABC), with the aim of recovering waste energy from the topping GTC. To maximize energy recovery, two thermoelectric generators (TEGs) are employed to harness the waste heat from the main bottoming systems. The generated power from these systems is subsequently directed to a proton exchange membrane electrolyzer (PEME) for hydrogen production. The primary objective of this study is to identify the most cost-effective bottoming system for hydrogen production. Optimization results reveal that the SRC-based bottoming system achieves the highest exergy efficiency at 35.68%. However, it does not align well with economic considerations, exhibiting a total cost rate of $176.6/h, a unit cost of $36.63/GJ, and a specific cost of $0.2904/kWh. Furthermore, the produced hydrogen mass flow rate is 3.324 kg/s. In contrast, the IBC-based system emerges as the optimal configuration, boasting an exergy efficiency of 33.55%. This system offers a more economically favorable profile, featuring a total cost rate of $162.1/h, a unit cost of $26.68/GJ, and a specific cost of $0.2835/kWh. The IBC-based configuration distinguishes itself by presenting the lowest total cost rate, unit cost of outputs, and specific cost among the four considered configurations. At the optimum point, it can generate 500 kW of power and produce 2.207 kg/h of hydrogen. This research, which is a combination of a literature review and a research article, underscores the critical role of selecting an economically efficient bottoming cycle in the context of waste energy recovery and hydrogen production within GT systems.