Energy, exergy, exergoeconomic, and exergoenvironmental (4E) analysis of a new bio-waste driven multigeneration system for power, heating, hydrogen, and freshwater production: Modeling and a case study in Izmir

Abstract

Today, the world is facing numerous challenges such as the increasing demand for energy, fossil fuels reduction, the growth of atmospheric pollutants, and the water crisis. In the present research, a new multigeneration system based on urban sewage bio-waste has been designed and evaluated for power, hydrogen, freshwater, and heating production. This system, which consists of biomass conversion subsystem, hydrogen production unit, Brayton cycle, atmospheric water harvesting unit, steam Rankine cycle, and organic Rankine cycles, has been evaluated from a thermodynamic point of view, and the energy, exergy, exergoeconomic, and exergoenvironmental analyses have been carried out on it. In the current study, the atmospheric water harvesting unit, as an attractive and environmentally friendly technology, is integrated with this Biomass-based multigeneration. A case study has been conducted on this system using the information collected from Çiğli wastewater treatment plant located In Izmir province, Turkey, and the results indicate that such a system, in addition to receiving sewage sludge from the treatment plant unit as a polluting waste, can produce added value products. The modeling results show that in the base conditions and with a feed rate of 7.52 kg/s, the total power generated by this system is 17750 kW, the hydrogen production rate is 3180 kg/h, the freshwater production rate is more than 18 l/h, and the energy and exergy efficiencies are 35.48% and 40.18%, respectively. According to the exergoeconomic and exergoenvironmental evaluations, the unit cost of total products and the unit emission of carbon dioxide are calculated as 13.05 $/GJ and 0.2327 t/MWh, respectively. Also, the results of parametric studies show that increasing the rate of Biomass improves the overall energy efficiency and production rates and also reduces the unit emission of carbon dioxide, but on the other hand, it causes a decrease in exergy efficiency and an increase in the unit cost of total products.