Reverse osmosis is one of the most efficient ways of desalinating seawater. A single reverse osmosis membrane not much bigger than a rolled newspaper can produce almost 400 litres of fresh water a day.
However, reverse osmosis requires pressures in the range of 800psi and current reverse osmosis plants use a lot of energy to produce this pressure.
In 2013, a senior design project at the University of North Carolina at Charlotte centered around proving the viability of using wave energy to pressurize water for the reverse osmosis process. This led Chris Matthews and Justin Sonnet to found SAROS which is now field-testing a prototype device that uses the forces generated by ocean waves to pump water through a reverse osmosis desalination system.
As the SAROS buoy rises and falls with passing swells, it works against its mooring tether to drive pumps. These pumps intake seawater at the buoy and pump it to shore under pressure. A device called a wavebank smooths the surges of incoming water from the buoy into a steady stream which flows through the reverse osmosis system. This removes salt, bacteria and other harmful material from the seawater.
The current test device is able to produce about 1,900 litres of fresh waste a day. A slightly larger production unit is planned to produce up to 13,000 lites of desalinated water a day at about half of current desalination processes.