Simultaneous optimization of size and short-term operation for an RO plant

• Published in: Desalination Vol. 301; pp. 42 - 52
• Main Authors: Williams, Christopher M., Ghobeity, Amin, Pak, Alex J., Mitsos, Alexander
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 03.09.2012; Elsevier
• Subjects: Applied sciences; Chemical engineering; desalination; Drinking water and swimming-pool water. Desalination; Economics. Management. Design assessment; electricity; Exact sciences and technology; Membrane separation (reverse osmosis, dialysis...); Natural water pollution; operating capital; Optimal RO plant size; Pollution; prices; Reverse osmosis; RO total annualized cost; Scheduling; seawater; Seawaters, estuaries; Spain; Time-dependent optimal operation; Water treatment and pollution; Spain; Time-dependent optimal operation; RO total annualized cost; Optimal RO plant size; Reverse osmosis; Scheduling; Short term; Membrane separation; Desalination; Modeling; Optimization; Capital cost; Seawater
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2012.06.009

The single day operation and size of a seawater reverse osmosis (RO) plant subject to a half-hourly varying electricity price is optimized. The study herein is an extension of Ghobeity and Mitsos, 2010 Desalination. Their model is modified to have a variable plant size controlled by the number of modules. The operating and capital costs are calculated as a function of size and operation. The objective of the optimization is to minimize the total annualized cost of the plant. The number of modules and the half-hourly varying operating frequency constitute the decision variables. The operation and size are optimized for four different electricity price functions: constant, moderately fluctuating, highly fluctuating, and actual electricity prices from a given day in Spain. The results show that variable operation and oversizing can produce savings of up to 7% for a highly fluctuating electricity price. The plant has a higher operating frequency when electricity is cheap and shuts off during periods of high electricity price when oversized. The size and day-by-day operation are also optimized for one year subject to Spain's electricity price. Little savings via oversizing are obtainable for the day-by-day optimization due to low fluctuations in the electricity price during the year. ► Optimized RO plant size and operation simultaneously with total annualized cost model ► Highly fluctuating electricity prices result in high TAC savings. ► Oversizing and long shut-off duration produce high TAC savings. ► Reducing operation costs can be more beneficial than reducing capital costs. ► TAC savings are also possible for day-by-day operation over a year with oversizing.