Economic evaluation of SWRO desalination plants using ERD powered by Off-Grid PV system

Abstract

Reverse Osmosis (RO) desalination is one of the most widely used and relied upon technologies for providing potable water supply to areas suffering from scarcity of drinking water. As such, there is considerable interest in reducing the energy requirements of such systems and finding alternate energy sources to replace dependency on traditional fossil fuels. This paper evaluated the economic viability of three seawater reverse osmosis desalination plants (SWRO) with and without Energy Recovery Devices (ERD). The plant capacities evaluated were 100, 300 and 500 m3/day of drinking water, powered by off-grid photovoltaic (PV) electricity for an average duration of 6 hours per day on the coastal city of Tajura-Libya.ROSA Software was used to determine suitable membrane units for the SWRO plants using pressure exchange turbines PX45, PX90, and PX140 models for the 100, 300, 500 m3/day plants respectively. The results showed that using ERD in the lower capacity plant (100 m3/day) resulted in increased Levelized Cost of Water (LCOW) and a favorable reduction in LCOW was obtained with the higher capacity plants (300 and 500 m3/day). On the other hand, the use of ERD resulted in significant reduction both in Specific Energy Consumption (SEC) and capital costs of the off-grid photovoltaic systems (40%-50% for all 3 evaluated desalination plants).