On the combined Brayton-Kalina cycle with PEM hydrogen production: An exergoeconomic analysis and multi-objective optimization with LINMAP decision maker

Abstract

Energy recovery and hydrogen production are essential in the current energy horizon of the globe. Applying the waste thermal energy and producing clean fuels in the power-generating cycles by keeping a sustainable view are the main goals of the current study. A combined Brayton-Kalina cycle accompanied by a PEM hydrogen production unit is studied using thermodynamic, exergetic, and economic evaluations. An external source is applied to supply the required heat for the closed Brayton cycle and the waste thermal energy is fed into the Kalina cycle. The Brayton cycle destructs more exergy than the Kalina cycle, respectively by the sharing value of 58% and 40%. The Brayton cycle shows the highest investment cost rate and the Kalina sets in the next rank. The PEM unit needs about 1% share of the total investment cost rate. A multi-objective optimization using NSGA-II algorithm is conducted to find the best operating conditions, considering the energy and exergy efficiency as well as investment cost rate function, as the objectives. The optimization makes an increase of 6% and 3% respectively in the total energy and exergy efficiency compared to the base working conditions, while it raises the investment cost rate by about 15%.