Off-Grid Solar Desalination

Water and energy are the two most basic and important aspects of off-grid living. Since the late 1990s, we have shown that solar photovoltaics and reverse-osmosis desalination can make a reliable, efficient source of both.

Until recently, the lead-acid batteries required to produce water around the clock accounted for over 60% of the cost of desalinated water. Those economics are changing fast, and off-grid solar desalination is becoming an economical option for off-grid living.

The ability to desalinate seawater anywhere there is sun transforms the potential of arid, off-grid land. As the cost of panels and batteries keeps falling, growing food in the desert becomes ordinary — a sustainable community needs only a source of seawater (or brackish groundwater) and the sun.

The system uses variable frequency drives to draw the DC current from solar panels and batteries directly. This creates an efficient, flexible demand that pairs well with the variability of solar — attractive for microgrids, which can treat a desalination plant as a sacrificial load.

Water production is an ideal sacrificial load because water can be stored easily while energy cannot. Extra water made during solar hours is used at night, for crops, or for hydroponics. Because RO's energy use is bounded by physics, becoming part of renewable-energy infrastructure is the only way to reduce and ultimately eliminate the emissions associated with desalination.