A novel integrated system for sustainable generation of hydrogen and liquid hydrocarbon fuels using the five-step ZnSI thermochemical cycle, biogas upgrading process, and solar collectors

The utilization of renewable energy sources such as solar energy and biogas have recently received more attention due to a decline in fossil energy sources and environmental issues. A leading method for long-term renewable energies sources storage is to convert to fuels such as hydrogen and heavy value hydrocarbons. In this work, a novel integrated structure is developed for sustainable cogeneration of hydrogen and heavy liquid hydrocarbon fuels. This integrated structure consists of the zinc-sulfur-iodine thermochemical cycle, biogas treatment cycle, Fischer–Tropsch synthesis reactions, a carbon dioxide power generation, and solar dish collectors. It is demonstrated that this integrated structure produces 359.8 kmol/h hydrogen, 116.8 kmol/h liquid fuels, 1714 kmol/h carbon monoxide, and 289,149 kmol/h hot water. The thermal energy and exergy efficiencies of the integrated structure are 58.03% and 44.34%, respectively. The exergy analysis illustrates that exergy destruction mostly occurs in heat exchangers (36.67%), reactors (24.69%), and collectors (20.25%). The sensitivity analysis demonstrates that the absorbed useful energy and solar collector thermal efficiency decrease up to 9.7353 kW and 0.7751, respectively when the average operating wall temperature in each solar collector increases from 627 °C to 1127 °C. The thermal efficiency and productivity of the liquid fuels increase up to 0.63 and 383.6 kmol/h, respectively with increase of carbon dioxide composition in the biogas from 40 mol% to 55 mol%.