Thermodynamic and thermoeconomic evaluation and optimization of an ORC coupled to a combined reverse osmosis/membrane distillation desalination system

This paper aims to evaluate and optimize the exergy and exergoeconomic performances of a 100 kWe ORC block coupled to a combined reverse osmosis/membrane desalination (MD) system to meet the electricity, hot water, and freshwater requirements for a remote inland community. The studied plant’s configuration includes a hybrid solar/biomass heat generation system feeding an ORC cycle. Depending on the end-users’ electricity load demand, part of the produced electricity can be used to drive a reverse osmosis unit for brackish water desalination. On the other hand, a fraction of the heat rejected from the ORC condenser is recovered to meet the community's hot water requirements and to feed a membrane distillation unit used to minimize the brine liquid discharge rejected by the reverse osmosis process. Optimization studies based on genetic algorithms were conducted at design conditions to evaluate the impact of the ORC working fluid, its operating conditions, and the hot source temperature on the ORC exergy efficiency, hourly exergoeconomic cost of the produced useful outputs, and the membrane distillation permeate production. Besides, parametric studies were conducted to evaluate the impact of biomass cost, main plant’s components costs, and the solar field’s aperture on the investigated system’s performances. Results showed that R245-fa allows achieving the optimal ORC exergy efficiency and MD permeate production, whereas R1336mzz(Z) permits reaching the minimum overall exergoeconomic cost. Results also showed that for the case of R245-fa, increasing the hot source temperature has a positive impact on the plant’s performances. According to the parametric studies results, biomass cost and ORC investment cost are the most influencing cost items on the hourly exergoeconomic cost of the system. Parametric studies also showed that the increase of the solar field aperture from 1106.4 to 3319.2 m² leads to a rise of the overall exergoeconomic cost by up to 29.87%.     «

This paper aims to evaluate and optimize the exergy and exergoeconomic performances of a 100 kWe ORC block coupled to a combined reverse osmosis/membrane desalination (MD) system to meet the electricity, hot water, and freshwater requirements for a remote inland community. The studied plant’s configuration includes a hybrid solar/biomass heat generation system feeding an ORC cycle. Depending on the end-users’ electricity load demand, part of the produced electricity can be used to drive a revers...     »