A small-scale seawater reverse-osmosis system with excellent energy efficiency over a wide operating range

A small-scale seawater reverse-osmosis system with excellent energy efficiency is presented. The system promises to deliver up to 460 l/h of potable water, from seawater (at 40,000 ppm), while consuming less than 1600 W of electrical power. This represents a specific energy consumption of less than 3.5 kWh/m3. Moreover, the flow may be controlled in order to reduce the power consumption by a factor of four without any significant loss of efficiency — the specific energy consumption remains near to 3.5 kWh/m3. The keys to these impressive figures are the energy recovery provided by the Clark pump, from Spectra Watermakers Inc., and the use of a variable water recovery ratio control algorithm, developed by CREST. The significance of the system is that it may be operated from variable intermittent renewable-energy sources, such as wind and solar-photovoltaic (PV), without need of batteries. Results of laboratory testing and extensive modeling are presented.