Waste heat recovery of a combined Brayton and inverse Brayton cycle for gas turbine based multi-generation hydrogen and freshwater purposes: 4E comparison with a simple coupled Brayton and inverse Brayton cycle

Using gas turbine cycles in power generation layouts can lead to a significant amount of waste energy. The combined Brayton and inverse Brayton cycle (IBC), which are used in such systems, has a considerable amount of waste energy in the heat rejection stage and exhausted gas, which has not been considered in previous studies. In the present research, a simple coupled Brayton and IBC (Configuration 1) is compared with a multi-generation system (Configuration 2) in which a hot water unit, a thermoelectric generator (TEG), and an absorption chiller are added to Configuration 1 for the waste energy utilization of combined Brayton and IBC. Furthermore, the power produced in IBC and TEG is directed to a proton exchange membrane electrolyzer and a reverse osmosis desalination unit for hydrogen and potable water outputs. Results show that although the total investment cost rate of Configuration 2 is higher than that of Configuration 1, the fuel cost rate, environmental cost rate, and exergy destruction cost rate of Configuration 2 are lower. Furthermore, at the best performance point, Configuration 2 has exergy efficiency and unit cost of products equal to 40.77% and 63.19 $/GJ. They are higher than Configuration 1 by 5% and 2%, respectively. Hence, with Configuration 2, a higher exergy efficiency with a lower fuel consumption and environmental cost rate is accessible.