Optimal energy mix for a reverse osmosis desalination unit considering demand response

Purpose: Reverse osmosis (RO) has become an important method of desalination to meet the ever-growing water needs around the world. Its integration with renewable energy source (RES) reduces the environmental impact of gas emissions and cost of conventional fossil energy sources. The optimal sizing of energy sources to power RO desalination system is intended mainly to minimize the annualized cost of the system and by extension minimize freshwater cost while maximizing production. Design/methodology/approach: In this study, a mathematical optimization approach is used to determine the optimal energy mix, which includes grid power, diesel generator and a photovoltaic (PV) module to supply an RO desalination unit. Three cases of optimal sizing approach were compared. Case 1 is a system with only grid power and diesel generator as energy sources; Case 2 has PV incorporated in the energy supply mix while Case 3 has the three energy sources and a Time of Use (TOU) demand response program on the demand side. Findings: The results of implementing the optimization models show that Case 3 turnout the highest freshwater production (1,521 m3/day) at a unit cost of 1.36$/m3 when compared to Case 1 with daily freshwater production of 1,250 m3/day at a unit cost of 1.68$/m3 and Case 2 having a daily freshwater production of 1,501 m3/day at a unit cost of 1.33$/m3. Originality/value: The integration of RES to power desalination system with application of TOU demand response is the significance of this study.