A green ammonia and solar-driven multi-generation system: Thermo-economic model and optimization considering molten salt thermal energy storage, fuel cell vehicles, and power-to-gas

In this paper, an ammonia-fueled combined heat and power generation system is modeled and analyzed from thermodynamic and economic points of view for application in large industrial sectors. Moreover, solar parabolic trough collectors and molten salt thermal energy storage are used to preheat water entering a bottoming steam-driven power generation cycle. An electrolizer is installed to separate water into hydrogen and oxygen for charging a hydrogen storage tank, procuring hydrogen for fuel cell vehicles, and producing methane by combining hydrogen and captured carbo dioxide. A mixed-integer nonlinear programming problem is solved to supply the natural gas, heat and electrical demands of a steel industry while minimizing the cost of the electrical power purchased from the local distribution grid during two extremely-hot summer days. It is found that ammonia-solar fueled poly-generation system is not only applicable for industrial sectors with maximum 10 MW electricity, 14 MW heat, and 11 MW natural gas demands under at least 52 % energy efficiency, but also supplies hydrogen for transportation electrification using fuel cell vehicles. The total cost of the electrical power purchased from the upstream distribution company during 48-h study horizon is obtained as 300 $, which proves the economic feasibility of the proposed gas-energy nexus model.