Today's soldiers trekking around on missions need to carry pounds and pounds of electronic equipment with them, and then about that much again in batteries to power it all. The US Army has been trialing systems that harvest kinetic energy through the wearer's walking, and now a chance discovery might also help lighten the load. The US Army Research Laboratory has created an aluminum-based powder that produces a surprisingly high amount of energy when placed in water.
The unexpected discovery came when researchers mixed a nanogalvanic aluminum-based powder with water, and noticed that the water began bubbling away. On closer inspection, they soon realized the reaction was the product of hydrolysis, meaning the material was splitting the water into its composite molecules of oxygen and hydrogen.
Aluminum has been known to produce hydrogen in this manner, but it usually requires a catalyst in the form of heat, acid, electricity or other chemicals. But the new nanomaterial turns out to be an efficient mechanism for rapid and spontaneous hydrolysis of water.
"In our case, it does not need a catalyst," says Anit Giri, a physicist on the team. "Also, it is very fast. For example, we have calculated that one kilogram (2.2 lb) of aluminum powder can produce 220 kilowatts of power in just three minutes. That's a lot of power to run any electrical equipment. These rates are the fastest known without using catalysts such as an acid, base or elevated temperatures."
To test the material, the team used the captured hydrogen to power a radio-controlled model tank (Credit: US Army/David McNally)
For these initial tests, the team used the hydrogen created through the reaction to power a radio-controlled model tank around the lab. But in future, the team says the material's energy potential can effectively be doubled if the heat given off is also harnessed.
"There are other researchers who have been searching their whole lives and their optimized product takes many hours to achieve, say 50 percent efficiency," says Scott Grendahl, team leader on the project. "Ours does it to nearly 100 percent efficiency in less than three minutes."
The researchers say the powder could eventually be used to 3D print drones and robots that could recharge their batteries by dissolving parts of their own structure. And at mission's end, they'll have effectively self-destructed. That idea is a long way down the track, but a scenario we're more likely to see in the nearer future is one where human soldiers carry the material to recharge devices in the field.
"These teams are out for a short number of days, three to five days, and a lot of that depends not only on their food supplies, but on how long their supplies last in terms of their equipment and right now that stems from lithium batteries," says Grendahl. "If we can recharge those batteries, they can stay out longer."
The researchers are currently working on further applications for the material, as well as research papers and patents describing it.
Source: US ArmyView gallery - 4 images