1 October 2009

Producing more fresh water using less energy

Water is the one resource the world needs and is not getting enough of. So, one approach is to turn salt water into usable fresh water.

That means the next generation of technology to turn saltwater into a fresh resource is now on tap. The Office of Naval Research (ONR) is sponsoring the development of an innovative solution for generating potable water at twice the efficiency of current production for forces afloat, Marine Corps expeditionary forces, and humanitarian missions ashore.

“Saving energy and producing clean water is a tactical issue for the Navy,” said Dr. J. Paul Armistead, an ONR program officer with interests in water purification. “We plan to build prototype desalination units that will use 65% less energy and be 40% smaller by weight and by volume relative to current Navy reverse osmosis systems. They should require roughly 75% less maintenance.”

Delivering drinkable water for ships at sea and Marines ashore for less cost and less energy became an ONR priority in 2004 under the Expeditionary Unit Water Purification Program, or EUWP.

Before the advent of modern desalinization plants, mariners relied on the fresh water they collected from rain and stowed while at sea. Today, sailors and Marines benefit from high-tech, Reverse Osmosis (RO) desalinization plants aboard most U.S. Navy ships.

It takes energy to make water, and that energy comes from burning fuel to spin turbine generators that produce electricity necessary for ship systems, including RO plants. A more efficient desalinization plant translates into a more efficient ship, which uses less fuel, extends combat capability, and reduces its carbon footprint.

Since its inception, the EUWP program has produced advances in desalinization capability. The first generation EUWP technology demonstrator was a deployable high water production unit more easily transported by the military and used for a variety of missions.

The second generation EUWP Gen II technology demonstrator, built with shipboard constraints imposed on the design, is a larger, more stationary demonstration unit, and has potential for use by isolated communities. It has successfully tested at the Seawater Desalination Test Facility at the Naval Facilities Engineering Service Center in Port Hueneme, Calif.

Armistead anticipates increased capabilities from the newer demonstration unit. “From current Navy desalination systems we only get 20% product water,” he said. “That means for 1,000 gallons of feed water, we would get only 200 gallons product water. These new systems will likely double that.”

For related information, go to www.isa.org/manufacturing_automation.