Does the ocean’s waves have what it takes to clean water?

Desalination is expensive and, though it has long been understood to be a promising answer to the issue of the scarcity of fresh water, it has remained on the fringes of near-term water policy in much of the world. Yes, 97.2% of the planet’s water is saline, yet the process of taking the salt out of it thus far provides only 1% of our species’ drinking water. So while a pragmatist may say that there is still a lot of room for progress here, a cynic might say that the room for progress has always been there, and could well stay there.

The problem that has kept desalinated water a niche market? The trick is to push the water through a membrane that will block the salt, “reverse osmosis.” But as Andrew Tarantola put the point for Engadget a year ago, “it takes a lot of energy to push salt water through these membranes at a sufficient rate.”  

Waves and Mechanical Energy

A solution might be surprisingly close to home. Perhaps the motion of the ocean’s waves itself can create the energy necessary to desalinate the water. That is the view of Bill Staby, the founder of Resolute Marine Energy.

Under Staby’s leadership, Resolute has developed what it calls Wave2O technology,  a system whereby communities on an ocean shore can harness the energy of the waves to desalinate. The Resolute design operates only on mechanical power: it is a technique that neither offers anything to the electrical grid nor draws from it. Waves move a lever back and forth, and the swinging lever sends pressurized sea water to an onshore facility and through the sort of filter described above, so that sea water in essence presses itself through the filters. 

Reading a flattering profile of Staby in Forbes reminded us a bit of plans by a Dutchman, Boyan Slat, and his non-profit, Ocean Clean-Up, to enable the Pacific Ocean, again through the energy of its waves, to clear itself of much of the plastic debris that has accumulated between Hawaii and California.

Of course, the devices that Slat has in mind will operate far from shore, and neither contributing to nor taking from any onshore grid will be an option.

Waves and Electricity

Work continues on wave-powered devices that do produce electricity. They’ve been around for a long time, but there has been a lot of innovation of late. The Electric Power Research Institute has estimated that the waves breaking against the U.S. coastline alone could generate 2,640 terawatt hours each year. But all power generation is local, and, depending on the site, shipping, fishing, environmental concerns or other priorities will limit how many of those TWh are recoverable. The recoverable estimate -- again, limiting inquiry to the US coast -- is  1,170 TWh a year. Still, that is an impressive figure: nearly a third of the amount of electricity the U.S. consumes.

How exploit that? On August 14, 2018, Czero Inc. (a Colorado-based engineering firm) and CalWave Power Technologies announced that they’ll be working together to perfect and render operational CalWave’s patented Wave Energy Converter, a subsurface device that produces an electrical current from ocean waves. CalWave’s device, like Resolute’s, operates beneath the surface, both to allow it to ride out stormy weather and to keep it from sight.  It has a contract with the US Department of Energy to demonstrate its system, which it says has doubled the energy that can be captured from ocean waves given the prior state of the art.

Meanwhile, in Italy, 40South Energy and Elements Works have just completed an upgrade on a system known as the H24 in the Ligurian Sea. Michele Grassi, the CEO of 40South, says that in its first demonstration, in 2015, the electricity generated by the H24 was “dissipated locally,” but after the upgrade, “we will inject the electricity into the Italian grid.”

A Final Thought

Drawing power, whether mechanical or electrical, from the motions of the sea has one obvious advantage: there is no danger that it is going to “run out.” The oceans are restless for the simplest of reasons: the planet keeps turning. In addition, evaporation, precipitation, the tidal pull of the moon, differences in temperature and salinity, and a number of other factors stir the oceans and complicate the movements of its water. And always will.

GET THE LATEST STORIES AND TIPS FROM CATERPILLAR – SIGN UP FOR OUR E-NEWSLETTER