The average U.S. soldier can carry a much as 40 pounds of batteries while on a four-day mission, powering goggles, GPS systems, radios and laptops. Currently, each of those devices requires its own unique batteries — you can't put the radio batteries in your night vision goggles and vice versa. The U.S. Army wants to change that and thinks portable fuel cells could be the solution. A central fuel cell power pack would allow soldiers to plug all their gadgets in one place while cutting the overall weight by as much as 80 percent. And if the fuel cells were tied to something like the solar tents mentioned earlier, the energy would be emissions-free.