System design and load profile shaping for a Reverse Osmosis desalination plant powered by a stand-alone PV system in Pozo Colorado, Paraguay

Groundwater is a common source of drinking water all over the world. In some places the groundwater resources are brackish, which means that it is of high salinity and undrinkable unless it is desalinated. Brackish Water Reverse Osmosis (BWRO) desalination is a method that can be applied to produce potable water from saline groundwater resources. This requires electricity to drive the high pressure pumps that enable reverse osmosis. In this article, a preliminary BWRO plant design for a village in Paraguay is presented, supplied by a stand-alone PV system with battery storage. The energy requirement of the desalination plant is estimated for sizing the power supply and storage systems. Two different load profiles are evaluated by simulations in PVsyst; the first scenario is based on constant load for maximum utilization of the membrane capacity, while the second scenario is based on partly adapting the load to the solar irradiation. The second scenario implies an increase of the plant size, since parts of the plant are stopped during nighttime, but allows for reducing the battery capacity since more of the energy for desalination is used when it is directly available from the PV system. The presented results demonstrate how system designs that allow for operation schemes with reduced freshwater production during the night will be economically beneficial due to a larger reduction in investment cost for battery storage than the cost increase due to larger membrane installation.