Integrated approach in eco-design strategy for small RO desalination plants powered by photovoltaic energy

Reverse osmosis (RO) plants powered by photovoltaic (PV) panels at community scale for remote places are increasing in importance. However, RO recovery rates in these seawater desalination plants are usually below 40% because of non-optimized plant configurations. Low recovery rates increase both the global costs of the plant and the volume of concentrate discharge, which is an ecological issue. This study aims to determine the RO plant configuration that enables the highest recovery rate and leads to the lowest global costs for small PV RO plants. The choice of the plant configuration includes the type, number and arrangement of the RO modules, single or double stage configuration, the area of the PV panels, the possibility of using batteries, and of using evaporation ponds for concentrate disposal. Based on an optimization procedure and cost estimation, the best PV RO plant configurations were found according to the production needed. A 65% recovery rate could be possible in double stage plants producing more than 5 m(3).d(-1) and would reduce costs. The use of a battery could reduce the costs in plants producing 5 m(3).d(-1) because the extra cost of the battery would be compensated by the possibility of using fewer RO modules.