Energy, exergy, and eco-environment modeling of proton exchange membrane electrolyzer coupled with power cycles: Application in natural gas pressure reduction stations

This paper focuses on introducing a new configuration of a hybrid system for producing power and hydrogen together with pre-heating natural gas in PRSs. The configuration is based on regenerative Brayton, Rankine and proton exchange membrane electrolyzer cycles. Also, a heat exchanger is embedded for supplying the required heating load of NG pre-heating to prevent hydrate formation. A robust energy, exergy, and eco-environment mathematical model with real assumptions is developed to prove feasibility of the introduced system. To make the study applicable for different PRS capacities, the analyses are done for different equipment sizes during different months of year. The parametric study showed that design variables of the Brayton cycle and pressure of inlet NG are very effective parameters in the design of this proposal. Analyzing the results in different months illustrated that the best performance is achieved in January; so that, 20.25 MW of power, 19.91 MW of heating load, and 11.96 kg/h hydrogen are produced for the optimum equipment variables in this month. At these conditions, the first- and second-law efficiencies and the levelized total costs rate are respectively obtained as 58.91%, 34.02%, and 7.03 $/GJ. Also, the payback period is 6.77 years based on the NPV approach.