A novel multigeneration system driven by a hybrid biogas-geothermal heat source, Part II: Multi-criteria optimization

Abstract

Hybridization of biogas and geothermal energies for power plants can present a promising way to resolve drawbacks of each individual heat source from economic viewpoint, especially when low-temperature geothermal heat source is posited. Concerning this aspect of hybrid renewable heat sources, a novel hybrid biogas-geothermal multigeneration system was proposed in the first part of our study, which was modeled under privilege of thermodynamic laws. In continuation of our previous study, the current study is performed to investigate economic, environmental, and enviroeconomical aspects of the introduced system. Furthermore, single and multi-criteria optimizations of this integrated system are carried out from 4E (energy, exergy, exergoeconomic, and environmental) analysis standpoints. After the optimization, the thermal and exergy efficiencies are raised by 12.07% and 5.16%, respectively, while the overall cost of the product is decreased by 3.7%. Also, the emission rate of the suggested multigeneration system is decreased from 0.1913 kg/kJ to 0.1828 kg/kJ, showing 4.44% reduction in the greenhouse gas emission in comparison with the base mode. From enviroeconomic viewpoint, the environment penalty cost rate is reduced from 147.4 $/h to 144.4 $/h after the optimization. Finally, a comprehensive sensitivity study based on the key economic parameters is performed and results are discussed.