|How the Energy Efficient System Works
This is why we can save 60% energy:
The Pressure Exchanger (PE) greatly increases the efficiency of the
SWRO system by harnessing the energy of the reject brine.
This efficiency can drive energy consumption under 2.8 kWh/m³ of product water.
By directly pressurizing a portion of the incoming seawater, the main high-pressure
pump size can be reduced by up to 60%. This not only saves energy, it also cuts
major capital costs.
Applying (PE) technology to SWRO is different from conventional recovery devise
design, but in practice its quite simple. (See diagram). The reject brine from the
SWRO membranes is passed through the (PE), where its pressure energy is
transferred directly to a portion of the incoming raw seawater at up to 94% efficiency.
This seawater stream, nearly equal in volume to the reject stream, then passes
through a small booster pump, which makes up for hydraulic losses through the
SWRO system. This seawater stream now joins the seawater stream from the main
high-pressure pump; it does not pass through the high-pressure pump.
This is significant, because now the main pump is sized to match the permeate flow,
not the full flow.
The main pump also makes up the small volume of brine lost through the (PE’s)
hydrostatic bearing. In a typical SWRO plant using the (PE) system, the main pump
will provide 41% of the energy, the booster will provide 2% and the (PE) will provide
the remaining 57%. Since the (PE) uses no external power, the total power saving is
57%, compared to a system with no recovery.
The (PE’s) one moving part, a shaft less ceramic rotor with multiple ducts, is
hydrostatically suspended within a ceramic sleeve. The rotor affects an exchange of
pressure from brine to seawater through direct contact displacement, with negligible
Unlike similar devises, the (PE) does not use separate valves or pistons. Due to the
precision of the rotor and the short resistance time, mixing of the raw water and brine