Environmental Impacts and Sustainability
Bahram Hosseinzadeh Samani; Marziyeh Ansari Samani; Rahim Ebrahimi; Zahra Esmaeili; Ali Ansari Ardali
Abstract
Due to limited oil reserves, the rising world fuel prices and environmental problems caused by the use of fossil fuels increase the tendency to use alternative fuels such as biodiesel and bioethanol. In this study, the evaluation of energy and exergy flow from seed planting to final production of biodiesel ...
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Due to limited oil reserves, the rising world fuel prices and environmental problems caused by the use of fossil fuels increase the tendency to use alternative fuels such as biodiesel and bioethanol. In this study, the evaluation of energy and exergy flow from seed planting to final production of biodiesel from rapeseed oil was carried out. Biodiesel production from rapeseed was made in three main phases: farm, oil extraction, and industrial biodiesel production. Initially, the input and output variables for rapeseed production were collected through questionnaires from 30 rapeseed farms in Khuzestan province, Iran. Thus, the amount of energy input and output to the field for rapeseed was estimated to be 12826.98 and 22195 MJ/ha, respectively. The highest energy consumption is related to chemical fertilizers with 65 % share of other inputs. Input and output exergy rates were obtained as 3933.494 and 22603.39 MJ/ha, respectively, and the highest exergy consumption related to diesel fuel with 58 % share of other inputs. At the biodiesel production stage, the input energy and output energy were 156.95 MJ and 41.88 MJ, respectively, and the highest amount of electricity consumed was 91.02 MJ. The total amount of exergy in the production of biodiesel and the output exergy was 48.412 MJ and 64.568 MJ, respectively. In this study, the effects of alcohol-to-oil molar ratio, ultrasound power (W), catalyst concentration (w/w %), and the reaction time (min) on methyl ester yield using response surface methodology based on Box Behnken experimental design in the Design Expert software were investigated. Finally, gas emissions were studied at the planting and biodiesel production stages, and the resultsshowed that the highest greenhouse gas emissions at the planting stage were related to chemical fertilizers and alcohol production.
Mahboobe Sabaghian; Fateme Ahmadi Boyaghchi
Abstract
Energy, exergy and exergoeconomic (3E) evaluation are performed to assess the performance of a NH3/H2O cycle integrated with parabolic trough solar collectors (PTSC). To provide continuous electricity produced by generator when solar beam radiation is insufficient a stabilizer temperature subsystem is ...
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Energy, exergy and exergoeconomic (3E) evaluation are performed to assess the performance of a NH3/H2O cycle integrated with parabolic trough solar collectors (PTSC). To provide continuous electricity produced by generator when solar beam radiation is insufficient a stabilizer temperature subsystem is utilized. The major thermodynamic parameters and climate conditions variations are selected to investigate, for their effects on the energy efficiency, exergy efficiency and unit cost of electricity of the overall system. The results reveal that the solar collectors exhibit the worst exergy and exergoeconomic performance, so that when system is only fuelled by solar energy, elevation of solar beam irradiation around 40% reduces the efficiencies and electricity production cost within 23% and 0.4%, respectively. It is found that the increment of ammonia basic concentration, turbine inlet pressure, evaporator inlet temperature and evaporator pinch temperature lead to elevation of energy and exergy efficiencies and decrement of electricity production cost. Then, the single and multi-objective optimizations are performed to maximize the energy and exergy efficiencies and minimize the electricity production cost based on genetic algorithm (GA). Results indicate that the electricity production cost obtained through economic optimization is less than around 2% and 2.2% compared to the optimization based on the first and second laws of thermodynamics. Multi objective optimization causes reduction of electricity production cost around 14% and enhancement the energy and exergy efficiencies 8.5% and 6.7%, respectively too.
