Energy, exergy and sensitivity analyses of a novel hybrid structure for generation of Bio-Liquefied natural Gas, desalinated water and power using solar photovoltaic and geothermal source

Nowadays, with the increased energy demand worldwide, the utilization of various energies with the approach of maximizing the energy systems performance is an inevitable issue. The produced biogas from various types of biomasses as a renewable source of energy can satisfy a portion of the human needs due to its vast resources. In the present study, an integrated structure is developed and analyzed for the generation of bio-liquefied natural gas, desalinated water and power using the upgrading biogas system, multi-effect thermal desalination, and organic Rankine cycle. The photovoltaic system and geothermal source are employed to supply the power and heating for the integrated structure, respectively. This hybrid system generates 5.295 kg/s bio-LNG, 2.773 kg/s desalinated water and 840 kW power. The mixed fluid cascade cycle is used for methane liquefaction that its specific power consumption is reduced to 0.1888 kWh/kg LNG by using the absorption refrigeration system. The overall thermal and exergy efficiencies of the integrated system are 73.22% and 76.84%, respectively. Exergy analysis illustrates that the solar photovoltaic with 70.05% and the towers with 8.05% of exergy destruction have the most exergy destruction to the total equipment. The investigation on the effect of variation of methane percentage in the existing biogas on the system performance shows that with the increase of methane percentage to 75 mol%, the amount of produced bio-LNG and desalinated water increase up to 7.969 kg/s and 2.779 kg/s, respectively. Also, the total thermal efficiency would increase by up to 73.30%.