Wave Powered Desalination

20 DEC 2019
If we had unlimited energy supplies without environmental impact what would we use that energy for? A good chance we'd use it to create fresh potable water, and to treat effluent and polluted water run-off. Imagine the flowering of dry arid deserts, and the remediation of salinised land. Food scarcity would be removed, and the pressure on our natural environments reduced.

In Western Australia a wave powered desalination plant has been in operation for a few years now and is providing fresh water free from carbon emissions. The genius of Carnegie Wave Energy Limited is in the process. The tethered wave powered generator creates a pressurised stream of water that flows to the land where it is used directly to presurise a reverse osmosis desalination system. Salt water is push against a very tiny nano-scale sieve that allows water molecules to pass while stopping the large salt molecules. The salt is then flushed from the sieve with a change in pressure, and returned to the wave generator where the brine is returned to the sea.

Excess energy is captured and sent to the grid as electricity.

In traditional reverse osmosis systems, many have these in their kitchens where water quality is suspect, electricity is used to power the pumps to create the pressure differential. So to use the movement of waves to create the pressure required is inspired.

There are many other ways to desalinate water, with varying degrees of efficiency. Wave-Powered may be the most elegant but it may still prove difficult to scale. There are many streams of water that could be remediated and reused for potable drinking water. Singapore and London famously recycle their effluent, while brackish water can be up-cycled to fresh more readily.

There are drawbacks to desalination - mainly the flow of brine that carries the concentrated salt back to the sea. I could imagine that in desert regions this brine could be used to start off the production of salt for industrial and domestic use - the balance being evaporated naturally. But we're always going to face this problem - and perhaps we should consider brine a pollutant.

It may be that even with unlimited energy - should we ever manage that - will still require smart ways to deal with brine. Perhaps concentrated into blocks it could effectively be sequestered, or used as a building material. The need to balance salt with water will always be with us.
By Hab3