Navigant Research Blog

Water, Water Everywhere—But Not a Drop to Drink

Anne Wrobetz — July 31, 2015

Floating islands are the stuff of fantasy novels, Kevin Costner movies, and Final Fantasy VI. They can also occur in nature, as a conglomeration of aquatic plants, mud, and peat. With current predictions by climate scientist James Hansen that the sea level will rise at least 10 feet in the next 50 years, living on floating islands might become a necessity sooner than we think.

Fortunately, manmade floating cities are becoming as vogue as tiny houses.  In fact, outside of Kampala, Uganda, a group of 10 artists have taken up chic residence on a chunk of land that broke away from the mainland and is floating around Lake Victoria. The artists have everything they could want—constantly changing scenery, serenity, grass huts, a fresh supply of lake water, and even some fairly soggy garden beds.

Not a Drop to Drink

When floating islands are in a lake, it’s easy to rig up a filter or a simple chlorination system to make water potable. But water supply is an extraordinary issue when living at sea. The Seasteading Institute, in partnership with the Netherlands’ DeltaSync, recently ended a contest for architectural designs of modular floating islands. Participants were encouraged to consider sources of energy, but the contest did not require a water treatment center. Unless the island is connected to a mainland water source, though, on-island treatment systems are necessary. Some private companies have already developed solutions to this salty problem. On a $6.5 million private floating island (really more of a yacht) made by the Austrian company, Orsos, water supply is guaranteed through an onboard reverse osmosis desalination system. But with current high energy demands of traditional desalination plants, and the high price of this private island, this doesn’t seem likely to be a sustainable solution.

Enter the DESalting Island on Renewable multi-Energy Supply, or DESIRES. DESIRES utilizes several renewable energy sources (eolian, solar, tidal, wave, and hydrothermal gradient) and large storage reservoirs to produce salt-free, potable water at a cost of $0.88-$1.32 per cubic meter. Even the largest, most efficient desalination plants running on shore cost around $1.62 to produce a cubic meter of fresh water. Further, the DESIRES system has a small footprint—a module between 0.06 square km and 0.65 square km can produce enough water to supply a city of about 105 inhabitants. Further still, the system utilizes enhanced energy during storms to pump water, reducing its impact even further. However, the system is only in research phases right now. Real-world implementation could lead to more expensive and less efficient operation. In addition, the sheer number of renewable energy systems aboard the system could make the commercial capital cost quite prohibitive. Only time will tell whether the DESIRES system will be far more sustainable than traditional desalination technology.

But in the meantime, future denizens of the floating island rejoice!

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