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Army Tries Water From Vehicle Exhaust Fumes
Associated Press  |  October 05, 2005
Keeping an army provisioned in the desert is a ballet of logistics, particularly when it comes to supplying two vital liquids: diesel fuel and water.

Now, using technologies developed for the space program, the U.S. Army is conducting an experiment that could convert the exhaust pipes of military vehicles into water fountains.

Later this month, United Technologies Corp.'s Hamilton Sundstrand unit will deliver two military Humvees to the Army for three months of testing at the Aberdeen Proving Ground outside Baltimore. Built into each vehicle's truck bed is a complex system that can recover water from engine exhaust, purifying as much as half the liquid volume from a tank of fuel.

"This is one of those things where, when you first hear about it, you think the scientists have gone out of their minds," says Robert Leduc, president of Hamilton Sundstrand's flight systems business, which includes the water-recovery program. "But once you taste the water, you realize the potential."

The military calculates that a soldier in the desert needs about 20 gallons of water a day, five of which must be pure enough to drink, prepare food and use for medical needs. (The other 15 gallons are for bathing, washing clothes and the like.) Water gets to the front in vulnerable, slow-moving truck convoys that require armed escorts, or it is pumped from local rivers, lakes or ponds and purified by heavy-duty filters.

For the Army, the logistics of moving water limits how it can use troops. When soldiers are deployed in the field, it can easily take 40 percent of them to move water and other materials, often placing them in vulnerable positions, says Jay Dusenbury, science and technology team leader for the Army's Tank-Automotive Research, Development and Engineering Center, or TARDEC, in Warren, Mich. "Anything that can cut down on that vulnerability and enable troops to fight - even if they have been cut off from traditional water supplies - could be huge," he says.

Hamilton Sundstrand, based in Windsor Locks, Conn., has a $2 million contract to provide the Army with the first two water-generating Humvees. It also is completing a $1 million contract for a high-powered dehumidifier the size of a dorm-room refrigerator that can extract water vapor from the air, even in the desert. The Army plans to display the water-from-air box this week in Washington, D.C., at the annual convention of the Association of the U.S. Army, a lobbying and support group for active and retired personnel.

Converting diesel exhaust into drinking water is an idea that has been around for a while. It continues a field of research aimed at squeezing the most out of valuable resources in areas such as space travel. "When it costs $10,000 a pound to bring water to the space station, you start getting creative," says Ed Francis, vice president of land and sea systems at Hamilton Sundstrand. "We try to take waste products and turn them back into usable products again."

In motor vehicles, among the byproducts of fuel combustion are unburned hyrdrocarbons and water. Scientists have long known that those waste products, along with much of the heat, are expelled out the exhaust pipe and into the atmosphere. Laboratory scientists at the University of Kentucky's Center for Applied Energy Research, in Lexington, discovered a way to filter out usable water vapor.

Scientists Marit Jagtoyen, Geoff Kimber and the late Frank Derbyshire patented the filter technology, and Dr. Jagtoyen co-founded Lexington Carbon Co. in 1994. She installed the first prototype of a water-recovery system in a commercial Humvee in 2001, as part of an Army-funded small-business research grant. LexCarb later teamed with Hamilton Sundstrand to develop a unit that could withstand the rigors of military use.

The Humvees in the the demonstration program are, from the outside, indistinguishable from other military vehicles, except for a small water spigot behind the right rear wheel. Beneath the metal panels of the truck bed is a system of pipes and filters, which can collect water whenever the engine is running, at a rate of one gallon of water for every two gallons of fuel burned.

In the combustion process, the oxygen in the air combines with the hydrogen in the fuel, producing water vapor and exhaust gases. Rather than going out the tailpipe, the gases are vented through a catalytic converter to bake off as many impurities as possible, then run through two heat exchangers, which extract heat and cause the water vapor to condense into the collection tank. "At this point, the water is - at best - gray in color," says Gregg Newbold, general manager of Hamilton Sundstrand's Army and Marine programs.

From there, the decidedly unappetizing-looking water moves to a series of six "treatment beds," which consist of proprietary carbon filters developed by LexCarb. The first four filters strain out black gunk so that the water becomes amber. The final two filters remove remaining impurities, resulting in water that is as clean, or cleaner, than the tap water of many U.S. cities.

From there, the system adds a chlorine solution to kill bacteria and algae that might form post-purification and then deposits the water in a five-gallon tank. A spigot inside the cab of the vehicle dispenses water chilled by the air conditioner. "It has a slight chlorinated taste, but compared to how it started out, it's quite good," says Hamilton Sunstrand's Mr. Newbold. In theory, the tank could function as a source of drinking water for a crew of, say, four people over the course of a day. (It isn't intended to be the sole water source for an extended period.)

The filtration system, like many other fledgling processes, has tough hurdles to clear before ever making it into regular use, and many such technologies never survive the testing process. The water-recovery systems will have to get much cheaper before they can widely used. The goal would be to have the system cost no more than 20 percent of a military vehicle's price tag.

Weight and efficiency present the biggest drawbacks. The system on the Humvee weighs just under 500 pounds and can filter only between 75 and 200 gallons of water before the filters must be replaced. And of course it produces water only as long as the vehicle is burning fuel. The water-from-air system makes about 600 gallons of water a day, compared with 600 gallons an hour for a traditional machine that purifies water from a river or pond.

"But the potential of this technology really fires up the imagination," says the Army's Mr. Dusenbury. "We have proven that it can be done, so now it's a matter of proving that it can be more robust and practical."

For Hamilton Sundstrand, the potential upside could be huge. As part of the Army's plans to transform its fighters into more nimble, self-sufficient forces under the ongoing multibillion-dollar Future Combat Systems program, contractors have been asked to develop systems that will enable soldiers to fight for 72 hours without any logistical support.

In coming years, the military plans to procure thousands of vehicles, ranging from an estimated 5,000 souped-up fighting vehicles to 60,000 Humvee replacements to 30,000 large trucks for hauling heavy loads. "Any and all of these vehicles could be candidates for a water-recovery system," says Mr. Newbold.

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