Variable Displacement Piston Energy Recovery Device for Seawater RO

Seawater Reverse Osmosis (SWRO) for production of freshwater requires high pressures and flow rates of feed water, leading to high energy consumption.Energy recovery from the brine waste stream has potential to give SWRO an advantage as a source of drinking water, when compared to the logistical costs and increased risks for convoys trucking bottled water to small units where freshwater is not available.However, energy recovery at the scale of 10-15 GPH freshwater production from seawater is not capable of reaching the 15-20 watt-hr/gallon energy metric required.A combination high-pressure pump and energy recovery device is proposed that will recover the hydraulic energy from the brine stream and transmit it directly to the high pressure pump.The proposed method leverages the high-efficiency performance of piston pumps and hydraulic motors.Innovative design features are included for variable control of freshwater recovery rates while minimizing power transfer losses from the energy recovery device to the high pressure pump.Variable recovery control is essential to maximize SWRO efficiency as source water salinities and RO membrane performance varies.High efficiency pumping, energy recovery, and variable recovery control are all accomplished in one compact, lightweight, easily maintained unit powered by a single electric motor.