Water is pretty wild when you think about it: all of its three states of matter are consumable by humans, and one in particular can even give off electrical power. A team at the Massachusetts Institute of Technology has discovered that when water condenses on and spontaneously jumps back and forth between specially-treated copper plates, it picks up an electrical charge. To fully take advantage of this ability, said scientists built a machine that harnesses said charge and uses it to create electricity. The researchers admit that yield is low for now, predicting that a cellphone would take around 12 hours to fully charge, but, as MIT News points out, if you’re off the grid, there isn’t much else of a choice for electricity anyway. One possible drawback of this method, though, is that it inherently requires a humid environment, like a rainforest, for it to work.
Last year, MIT researchers discovered that when water droplets spontaneously jump away from superhydrophobic surfaces during condensation, they can gain electric charge in the process. Now, the same team has demonstrated that this process can generate small amounts of electricity that might be used to power electronic devices. The new findings, by postdoc Nenad Miljkovic, associate professor of mechanical engineering Evelyn Wang, and two others, are published in the journal Applied Physics Letters. This approach could lead to devices to charge cellphones or other electronics using just the humidity in the air. As a side benefit, the system could also produce clean water. The device itself could be simple, Miljkovic says, consisting of a series of interleaved flat metal plates. Although his initial tests involved copper plates, he says any conductive metal would do, including cheaper aluminum. In initial testing, the amount of power produced was vanishingly small — just 15 picowatts, or trillionths of a watt, per square centimeter of metal plate. But Miljkovic says the process could easily be tuned to achieve at least 1 microwatt, or millionth of a watt, per square centimeter. Such output would be comparable to that of other systems that have been proposed for harvesting waste heat, vibrations, or other sources of ambient energy, and represents an amount that could be sufficient to provide useful power for electronic devices in some remote locations.